WO2019035358A1

WO2019035358A1 - Vehicular mirror, and vehicular mirror equipped with image display function

Info

Publication number: WO2019035358A1
Application number: PCT/JP2018/028865
Authority: WO
Inventors: 二村　恵朗; 田口　貴雄
Original assignee: 富士フイルム株式会社
Priority date: 2017-08-15
Filing date: 2018-08-01
Publication date: 2019-02-21
Also published as: JP6967075B2; JPWO2019035358A1

Abstract

The present invention addresses the problem of providing a vehicular mirror with which a mirror reflection image having no irregularities can be observed, and a vehicular mirror equipped with an image display function. This vehicular mirror includes: a phase difference layer which is obtained by immobilizing a liquid crystal compound which is twist-aligned at a twist angle equal to or less than 360˚ along a helical axis extending along the thickness direction; and a circular polarization reflection layer.

Description

Vehicle mirror, mirror with image display function for vehicle

The present invention relates to a vehicle mirror and a mirror with an image display function for a vehicle.

In recent years, a half mirror is provided on the surface of the image display unit of an image display device, and a mirror with an image display function that displays an image in display mode and functions as a mirror in non-display mode such as power off of the image display device. Proposed. For example, Patent Document 1 exemplifies a mirror with an image display function that uses a reflection layer using selective reflection of cholesteric liquid crystal.

International Publication No. 2016/199786

The inventors of the present invention examined a mirror equipped with an image display function using a reflection layer using selective reflection of cholesteric liquid crystal as described in Patent Document 1 mounted on a vehicle. When used as a mirror in a non-display mode, etc., hatched light and dark unevenness (more specifically, formed by a plurality of hatchings) on a mirror reflection image of light reflected from the vehicle surface and incident from the vehicle rear through the rear glass It has been found that lattice-like unevenness (brightness and darkness unevenness) may occur.

Then, this invention makes it a subject to provide the mirror for vehicles which can observe the mirror reflected image without a nonuniformity.
Another object of the present invention is to provide a mirror with an image display function for a vehicle.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to achieve the said subject, the present inventors discover that the said subject can be solved by using the mirror for vehicles which laminated | stacked the circularly-polarized-light reflection layer and the phase difference layer which has a predetermined | prescribed characteristic. Completed the invention.
That is, it discovered that the said objective could be achieved by the following structures.

[1] A vehicle mirror including a retardation layer formed by fixing a liquid crystal compound which is twisted and oriented at a twist angle of 360 ° or less along a helical axis extending along a thickness direction, and a circularly polarized light reflection layer.
[2] The vehicle mirror according to [1], wherein the twist angle is 50 to 200 °.
[3] The vehicle mirror according to [1] or [2], wherein the twist angle is 50 to 100 °.
[4] The vehicle mirror according to any one of [1] to [3], wherein the circularly polarized light reflection layer includes a cholesteric liquid crystal layer.
[5] Furthermore, including a front plate,
The vehicle mirror according to any one of [1] to [4], wherein the front plate, the retardation layer, and the circularly polarized light reflection layer are disposed in this order.
[6] Further, it contains a transparent substrate,
The vehicle mirror according to [5], wherein the front plate, the retardation layer, the transparent substrate, and the circularly polarized light reflection layer are disposed in this order.
[7] Further, it includes a transparent substrate,
The vehicle mirror according to [5], wherein the front plate, the retardation layer, the circularly polarized light reflection layer, and the transparent substrate are disposed in this order.
[8] A vehicle mirror according to any one of [1] to [7] and an image display device,
The mirror with the image display function for vehicles by which the said phase difference layer, the said circularly polarized light reflection layer, and the said image display apparatus are arrange | positioned in this order.
[9] The mirror with an image display function for a vehicle according to [8], further including a quarter-wave plate between the mirror for a vehicle and the image display device.
[10] The mirror with an image display function for a vehicle according to [9], wherein the circularly polarized light reflection layer and the 1⁄4 wavelength plate are in direct contact with each other.

According to the present invention, it is possible to provide a vehicle mirror capable of observing a mirror reflection image without unevenness.
Further, according to the present invention, it is possible to provide a mirror with an image display function for a vehicle.

It is a sectional view of the 1st embodiment of the mirror with a picture display function for vehicles. It is a schematic diagram which shows the relationship of the in-plane slow axis of a phase difference layer. It is a sectional view of the 2nd embodiment of the mirror with a picture display function for vehicles. It is sectional drawing of 3rd embodiment of the mirror with a picture display function for vehicles. It is sectional drawing of the 4th embodiment of the mirror with a picture display function for vehicles.

Hereinafter, the present invention will be described in detail.
In the present specification, “to” is used in the meaning including the numerical values described before and after it as the lower limit value and the upper limit value.
In the present specification, for example, angles such as “45 °”, “parallel”, “vertical” or “orthogonal” have a difference with the exact angle within the range of less than 5 degrees unless otherwise specified. Means The difference from the exact angle is preferably less than 4 degrees, more preferably less than 3 degrees.

In the present specification, the term "sense" for circularly polarized light means that it is right circularly polarized light or left circularly polarized light. The sense of circularly polarized light is right circularly polarized when the tip of the electric field vector rotates clockwise with time increase when the light is viewed as it travels to the front, and left when counterclockwise. Defined as circularly polarized.
In the present specification, the term "sense" may be used with respect to the twist direction of the helix of the cholesteric liquid crystal. The selective reflection by the cholesteric liquid crystal reflects right circularly polarized light when the twisting direction (sense) of the cholesteric liquid crystal spiral is right, transmits left circularly polarized light, and reflects left circularly polarized light when the sense is left, and right Transmits circularly polarized light.

Visible light is light of wavelengths visible to human eyes among electromagnetic waves, and shows light in a wavelength range of 380 to 780 nm. That is, the visible light region intends a region of 380 to 780 nm. Infrared (infrared light) is an electromagnetic wave in a wavelength range longer than visible light. That is, the infrared light region is intended for a region of more than 780 nm, and is preferably a region of more than 780 nm and 2500 nm or less.

As a feature of the present invention, a retardation layer (hereinafter also referred to as a twist retardation layer) formed by immobilizing a liquid crystal compound twisted and oriented at a twist angle of 360 ° or less along a helical axis extending along the thickness direction. And a circularly polarized light reflection layer.

The inventors of the present invention have the cause of unevenness in the mirror reflection image of light incident from the rear of the vehicle through the rear glass because fine retardation unevenness (Re (550) present in the rear glass is about 50 nm. Re (550) Means that the retardation is at a wavelength of 550 nm.
It is known that the tempered glass (for example, tempered glass which is not the composition of laminated glass) used for rear glass has a birefringence distribution. Tempered glass is generally produced by heating float sheet glass to 700 ° C. near the softening point and then blowing air onto the glass surface for quenching. While this treatment lowers the temperature of the glass surface first and shrinks and hardens, the temperature inside the glass is slower than the surface and slower to shrink, so that stress distribution occurs inside and there is no birefringence. Even when float plate glass is used, birefringence distribution occurs in the tempered glass.

Therefore, it is thought that the above-mentioned unevenness arises in the mirror reflection image by the light which penetrates the rear glass etc. of the vehicle in which the produced tempered glass is used, and enters the vehicle mirror (front) including the circularly polarized light reflection layer . More specifically, first, the light reflected by the surface of the vehicle has a large proportion of s-polarized light. When light including polarized light passes through the rear glass, a polarization distribution is generated in the transmitted light due to the birefringence distribution of the rear glass. When the light in which the polarization distribution is generated is reflected by the circularly polarized light reflection layer of the vehicle mirror, since the reflectance is different due to the difference in the polarization state of the incident light, the unevenness of brightness is visually recognized.
On the other hand, the vehicle mirror of the present invention includes the twist phase difference layer to shift the phase of the incident light whose polarization state differs depending on the place to a region where the difference in the intensity of the reflected light is less likely to occur, thereby reducing unevenness. There is. Specifically, the vehicle mirror according to the present invention includes the twist phase difference layer to increase the reflectance of incident light as a whole and to increase the overall brightness of the mirror reflection image. As a result, unevenness is caused. It is believed that the reduction of
Furthermore, the present inventors confirmed that when the twist angle of the aligned liquid crystal compound in the twist retardation layer exceeds 360 °, the unevenness in brightness and darkness is not reduced.
Below, embodiment of the mirror for vehicles of this invention and the mirror with an image display function for vehicles is shown.

<< First embodiment >>
Hereinafter, a first embodiment of a mirror with an image display function for a vehicle according to the present invention will be described with reference to the drawings. FIG. 1 shows a cross-sectional view of a first embodiment of a mirror with an image display function for a vehicle of the present invention. The figures in the present invention are schematic views, and the relationship of thickness of each layer, positional relationship and the like do not necessarily coincide with the actual ones. The same is true for the following figures.
The vehicle image display function-equipped mirror 10 includes an image display device 12, a quarter wavelength plate 14, a circularly polarized light reflection layer 16 including a cholesteric liquid crystal layer, and a twist retardation layer 18 in this order. The circularly polarized light reflection layer 16 and the twist retardation layer 18 constitute a vehicle mirror of the present invention. Further, although the quarter wavelength plate 14 is included in the first embodiment shown in FIG. 1, the invention is not limited to this embodiment, and even if the quarter wavelength plate is not included in the mirror with the image display function for vehicles Good.
The circularly polarized light reflection layer 16 includes a first cholesteric liquid crystal layer 20 which selectively reflects red light, a second cholesteric liquid crystal layer 22 which selectively reflects green light, and a third cholesteric which selectively reflects blue light. And a liquid crystal layer 24. The twist retardation layer 18 is on the viewing side. The circularly polarized light reflection layer 16 reflects one of right-handed circularly polarized light and left-handed circularly polarized light, and transmits the other. This function makes it possible to use the mirror as a mirror that reflects the rear of the vehicle in a non-display mode such as when the power of the image display device 12 is turned off.
As described above, in the mirror 10 with an image display function for a vehicle, the phase of light transmitted through the rear glass of the vehicle and the like and incident on the mirror 10 with an image display function for a vehicle is reflected light by the twist phase difference layer 18 It shifts to the area where the difference in strength is unlikely to occur. As a result, a mirror reflection image without unevenness is obtained.
Further, in the mirror 10 with an image display function for a vehicle, the quarter wavelength plate 14 is disposed between the image display device 12 and the circularly polarized light reflection layer 16 to circularly polarize the light from the image display device 12. And the circularly polarized light reflection layer 16. That is, light reflected by the circularly polarized light reflection layer 16 and returned to the image display device 12 side can be largely reduced, and image display with high luminance can be performed.
As shown in FIG. 1, the image display device 12 and the quarter wavelength plate 14 are preferably in direct contact with each other, and preferably, the quarter wavelength plate 14 and the circularly polarized light reflection layer 16 are also in direct contact with each other. . However, the present invention is not limited to this aspect, and other layers (for example, between the image display 12 and the 1⁄4 wavelength plate 14 and between the 1⁄4 wavelength plate 14 and the circularly polarized light reflection layer 16 may be used. , An adhesive layer, a transparent substrate, etc.) may be disposed.
In addition, it is preferable that the spiral sense of the circularly polarized light reflection layer 16 and the spiral sense of the twist retardation layer 18 coincide with each other.
Hereinafter, each member which comprises the mirror 10 with an image display function for vehicles is explained in full detail.

<Image display device>
The image display device is not particularly limited, but a liquid crystal display device or an organic electroluminescent display device is preferable. Moreover, it is preferable that an image display apparatus is an image display apparatus which radiate | emits linearly polarized light (it emits light) and forms an image.
The liquid crystal display device may be transmissive or reflective, and is preferably transmissive. The liquid crystal display device has an IPS (In-Place-Switching) mode, an FFS (Fringe Field Switching) mode, a VA (Virtical Alignment) mode, an ECB (Electrically Controlled Birefringence) mode, an STN (super twisted nematic) mode, and a TN (Twisted Nematic) Or any optically liquid crystal display device such as OCB (Optically Compensated Bend) mode.
The organic electroluminescent display device preferably includes at least a light emitting layer, and preferably further includes an anti-reflection circularly polarizing plate. The circularly polarizing plate includes a form including a λ / 4 wavelength plate and a polarizer.
The image display device preferably has a visible light average reflection of at least 20%, more preferably at least 30%, at a wavelength of 400 to 700 nm when the power is off. The reflection of visible light when the power of the image display apparatus is off may be derived from the constituent members of the image display apparatus (such as a reflective polarizing plate and a backlight unit).

The image shown on the image display unit of the image display device may be a still image, a moving image, or mere text information. In addition, monochrome display such as black and white, multi-color display, and full-color display may be performed.

<1/4 wave plate (λ / 4 wave plate)>
The quarter-wave plate is a retardation plate having a function of converting linearly polarized light of a specific wavelength into circularly polarized light (or circularly polarized light into linearly polarized light). More specifically, it is a retardation plate whose retardation at a predetermined wavelength λ nm (preferably a wavelength in the visible light region) indicates Re (λ) ≒ λ / 4 (or an odd multiple thereof).
It is preferable that the angle of the slow axis of the quarter-wave plate be adjusted so that the image becomes brightest when the quarter-wave plate is bonded to the image display device. That is, the polarization direction (transmission axis) of the linearly polarized light and the quarter-wave plate of the linearly polarized light so that the linearly polarized light is best transmitted through the circularly polarized light reflection layer, particularly to the image display device displaying an image by the linearly polarized light. It is preferable that the angle with the slow axis be adjusted. For example, in the case of a single-layer quarter-wave plate described later, it is preferable that the polarization direction (transmission axis) and the slow axis of the quarter-wave plate form an angle of 45 °. The light emitted from the image display device displaying an image by linearly polarized light, after passing through the 1⁄4 wavelength plate, becomes circularly polarized light of either right or left sense. The circularly polarized light reflection layer is preferably composed of a cholesteric liquid crystal layer having a twisting direction that transmits the above-mentioned sense circularly polarized light.

Examples of the quarter-wave plate include a single-layer quarter-wave plate and a wide-band quarter-wave plate in which a quarter-wave plate and a half-wave plate are stacked. Here, the half-wave plate refers to a retardation plate in which the phase difference at a specific wavelength λ nm (preferably, the wavelength in the visible light region) satisfies Re (λ) ≒ λ / 2.
The phase difference of the former 1⁄4 wavelength plate may be 1⁄4 of the emission wavelength of the image display device. Therefore, for example, when the emission wavelength of the image display device is 450 nm, 530 nm, and 640 nm, the wavelength of 450 nm is 112.5 nm ± 10 nm (preferably 112.5 nm ± 5 nm, more preferably 112.5 nm), 530 nm 132.5 nm ± 10 nm (preferably 132.5 nm ± 5 nm, more preferably 132.5 nm) at the wavelength, and 160 nm ± 10 nm (preferably 160 nm ± 5 nm, more preferably 160 nm) at the 640 nm wavelength Such a reverse dispersion retardation layer is preferably a quarter wave plate.
As the 1⁄4 wavelength plate, it is also possible to use a retardation plate with small wavelength dispersion of retardation, and a retardation plate of forward dispersion.
The inverse dispersion means a property that the absolute value of the retardation increases as the wavelength becomes longer, and the forward dispersion means the property that the absolute value of the retardation increases as the wavelength becomes shorter.

As a laminated quarter-wave plate, the quarter-wave plate and the half-wave plate are bonded at an angle of 60 ° between the slow axes of both, and the half-wave plate side is linearly polarized. It is preferable to use one that is disposed on the incident side of the light source and that the slow axis of the half-wave plate crosses 15 ° or 75 ° with the polarization direction (transmission axis) of the incident linearly polarized light.
In the present specification, the phase difference means front retardation. The phase difference can be measured using a polarization phase difference analyzer AxoScan manufactured by AXOMETRICS. Alternatively, light of a specific wavelength may be made incident in the film normal direction in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments Co., Ltd.) for measurement.

The quarter wavelength plate is not particularly limited, and can be appropriately selected according to the purpose. For example, a quartz plate, a stretched polycarbonate film, a stretched norbornene-based polymer film, a transparent film oriented by containing inorganic particles having birefringence such as strontium carbonate, and an inorganic dielectric on a support An obliquely deposited thin film and the like can be mentioned.
A commercially available product can also be used as the 1⁄4 wavelength plate, and examples of the commercially available product include trade name: Pure Ace WR (manufactured by Teijin Limited).

The quarter-wave plate may be formed by aligning and fixing a polymerizable liquid crystal compound or a polymer liquid crystal compound, and is preferably a layer formed by curing a liquid crystal composition containing the polymerizable liquid crystal compound. . For example, a quarter wavelength plate applies a liquid crystal composition containing a polymerizable liquid crystal compound on a predetermined substrate, heat-treats the polymerizable liquid crystal compound in a nematic orientation, and then fixes it by photocrosslinking or thermal crosslinking. , Can be formed.
The liquid crystal composition may contain other components (for example, a polymerization initiator, a solvent, and the like) in addition to the polymerizable liquid crystal compound.

The thickness of the quarter-wave plate is not particularly limited, but is preferably 0.2 to 10 μm, and more preferably 0.5 to 2.0 μm.

<Circularly polarized light reflection layer>
The circularly polarized light reflection layer is a layer that reflects circularly polarized light, and in the first embodiment, the central wavelength of the selective reflection band (selective reflection wavelength band) is located in the visible light region (shows selective reflection in the visible light region) It is a layer containing a cholesteric liquid crystal layer. That is, the circularly polarized light reflection layer includes a predetermined cholesteric liquid crystal layer, and the central wavelength of the band (reflection band) selectively reflected by the predetermined cholesteric liquid crystal layer is located in the visible light region. The specific configuration of the cholesteric liquid crystal layer will be described in detail later.
In FIG. 1, the circularly polarized light reflection layer 16 includes a first cholesteric liquid crystal layer 20 that reflects red light, a second cholesteric liquid crystal layer 22 that reflects green light, and a third cholesteric liquid crystal layer 24 that reflects blue light. It contains three cholesteric liquid crystal layers.

In the first embodiment of FIG. 1, the circularly polarized light reflection layer 12 includes three cholesteric liquid crystal layers, but the present invention is not limited to this embodiment, and the circularly polarized light reflection layer includes at least one cholesteric liquid crystal layer described above. The number of cholesteric liquid crystal layers may be two or four or more.
When the circularly polarized light reflection layer contains a plurality of cholesteric liquid crystal layers, it is preferable that central wavelengths of selective reflection bands of the cholesteric liquid crystal layers be different from each other.

When the circularly polarized light reflection layer includes a plurality of cholesteric liquid crystal layers, they are preferably in direct contact with the adjacent cholesteric liquid crystal layers.
The thickness of the circularly polarized light reflective layer is preferably 2.0 to 300 μm, and more preferably 5.0 to 200 μm.
The thickness of each cholesteric liquid crystal layer is preferably 1.0 to 150 μm.

Examples of the first cholesteric liquid crystal layer 20 that selectively reflects red light include a cholesteric liquid crystal layer having a central wavelength of the selective reflection band in 580 to 700 nm. Further, as the second cholesteric liquid crystal layer 22 that selectively reflects green light, a cholesteric liquid crystal layer having a central wavelength of the selective reflection band in the range of 500 nm to less than 580 nm can be mentioned. Further, as the third cholesteric liquid crystal layer 20 which selectively reflects blue light, a cholesteric liquid crystal layer having a central wavelength of the selective reflection band in the range of 400 nm to less than 500 nm can be mentioned.
In FIG. 1, the first cholesteric liquid crystal layer 20, the second cholesteric liquid crystal layer 22, and the third cholesteric liquid crystal layer 24 are arranged from the side close to the image display device 12, but this aspect is not limited. The three layers may be arranged in any order.
Among them, as shown in FIG. 1, when the circularly polarized light reflection layer includes a plurality of cholesteric liquid crystal layers, the cholesteric liquid crystal layer closer to the image display device has a central wavelength of a longer (longer wavelength side) selective reflection band. It is preferable to have With such a configuration, it is possible to suppress the oblique color in the display image and the mirror reflection image.

(Cholesteric liquid crystal layer)
In the present specification, a cholesteric liquid crystal layer means a layer in which a cholesteric liquid crystal phase is fixed. The cholesteric liquid crystal layer may be simply referred to as a liquid crystal layer.
The cholesteric liquid crystal phase exhibits circularly polarized selective reflection that selectively reflects circularly polarized light of either one of right circularly polarized light and left circularly polarized light and transmits circularly polarized light of the other sense in a specific wavelength range Are known. In the present specification, circular polarization selective reflection may be simply referred to as selective reflection.
Many films formed from a composition containing a polymerizable liquid crystal compound as a film including a layer to which a cholesteric liquid crystal phase exhibiting a circularly polarized light selective reflectance is fixed are conventionally known, and for cholesteric liquid crystal layers, those films You can refer to the technology.

The cholesteric liquid crystal layer may be any layer as long as the orientation of the liquid crystal compound in the cholesteric liquid crystal phase is maintained, and typically, after the polymerizable liquid crystal compound is in the aligned state of the cholesteric liquid crystal phase, ultraviolet irradiation is performed. The layer may be polymerized and cured by heating or the like to form a layer having no fluidity, and at the same time, the layer may be changed to a state in which no change in orientation is caused by an external field or an external force. In the cholesteric liquid crystal layer, it is sufficient as long as the optical properties of the cholesteric liquid crystal phase are maintained in the layer, and the liquid crystal compound in the layer may no longer exhibit liquid crystallinity. For example, the polymerizable liquid crystal compound may become high in molecular weight by the curing reaction and may no longer have liquid crystallinity.

The central wavelength λ of the selective reflection band of the cholesteric liquid crystal layer depends on the pitch P (= helical period) of the helical structure in the cholesteric liquid crystal phase, and follows the relationship between the average refractive index n of the cholesteric liquid crystal layer and λ = n × P.
In the present specification, the central wavelength λ of the selective reflection band of the cholesteric liquid crystal layer means a wavelength at the central position of the circularly polarized light reflection spectrum measured from the normal direction of the cholesteric liquid crystal layer.
As understood from the above equation, the central wavelength of selective reflection can be adjusted by adjusting the pitch of the helical structure. The central wavelength λ can be adjusted in order to selectively reflect either right circular polarization or left circular polarization with respect to light of a desired wavelength by adjusting the n value and the P value.

The pitch of the cholesteric liquid crystal phase depends on the type of the chiral agent used with the liquid crystal compound (preferably, the polymerizable liquid crystal compound) or the addition concentration thereof, and the desired pitch can be obtained by adjusting these. For the method of measuring the sense and pitch of the spiral, use the method described in “Introduction to Liquid Crystal Chemistry Experiment” edited by The Liquid Crystal Society of Japan, published by Sigma Publication 2007, p. 46, and “Liquid Crystal Handbook” Liquid Crystal Handbook Editorial Committee Maruzen p. 196. it can.

A bright image excellent in light utilization efficiency can be displayed by adjusting the central wavelength of the selective reflection band of the cholesteric liquid crystal layer to be used according to the light emission wavelength range of the image display device and the use mode of the circularly polarized light reflection layer. .

The sense of the reflected circular polarization of the cholesteric liquid crystal layer corresponds to the sense of the helix. As each cholesteric liquid crystal layer, a cholesteric in which the sense of the spiral is either right or left according to the sense of circular polarization of sense obtained by being emitted from the image display device and transmitted through the 1⁄4 wavelength plate A liquid crystal layer is used. Specifically, it is preferable to use a cholesteric liquid crystal layer having a sense of a spiral that transmits circularly polarized light of a sense obtained by being emitted from the image display device and transmitted through the 1⁄4 wavelength plate. When the circularly polarized light reflection layer includes a plurality of cholesteric liquid crystal layers, preferably the senses of the spirals are all the same.

The half width Δλ (nm) of the selective reflection band exhibiting selective reflection depends on the birefringence Δn of the liquid crystal compound and the pitch P, and follows the relationship Δλ = Δn × P. Therefore, control of the width of the selective reflection band can be performed by adjusting Δn. The adjustment of Δn can be performed by adjusting the type of liquid crystal compound and the mixing ratio thereof, or controlling the temperature at the time of alignment fixation.
In order to form one type of cholesteric liquid crystal layer having the same central wavelength of the selective reflection band, a plurality of cholesteric liquid crystal layers having the same period P and the same helical sense may be stacked. By laminating cholesteric liquid crystal layers of the same helical sense with the same period P, it is possible to increase the circular polarization selectivity at a specific wavelength.

The formation method of a cholesteric liquid crystal layer is not specifically limited, A well-known method is mentioned. Among them, a liquid crystal composition containing a polymerizable liquid crystal compound and a chiral agent is coated on a predetermined substrate from the viewpoint of excellent productivity, and the polymerizable liquid crystal compound is aligned in cholesteric liquid crystal by heat treatment, and then irradiated with light. Alternatively, a method may be mentioned in which the polymerization of the polymerizable liquid crystal compound is advanced by heat treatment to be cured.
The liquid crystal composition may further contain other components (for example, a polymerization initiator, a solvent, and the like).

As described in detail later, the circularly polarized light reflection layer is a circularly polarized light reflection layer including a quarter wavelength plate and a reflective linear polarizer (hereinafter, also referred to as a reflective linear polarizer). It may be.

<Twist retardation layer>
The twist retardation layer is a layer for turning the polarization axis of linearly polarized light, and is a layer for changing the ellipticity of elliptically polarized light more.
The twist retardation layer is a layer formed by fixing a liquid crystal compound twisted and oriented at a twist angle of 360 ° or less along a helical axis extending along the thickness direction. Among them, as described later, it is preferable that the layer be obtained by polymerizing and curing the polymerizable liquid crystal compound by ultraviolet irradiation, heating or the like after setting the liquid crystal compound in a predetermined twisted alignment state.
In addition, that the liquid crystal compound is twist-oriented means that the liquid crystal compound from one surface to the other surface is twisted, with the thickness direction of the layer as an axis (helical axis). Along with that, the alignment direction (in-plane slow axis direction) of the liquid crystal compound differs depending on the position in the thickness direction. The liquid crystal compound will be described in detail later, but as the liquid crystal compound used in the twist retardation layer, a liquid crystal compound exhibiting a nematic liquid crystal phase is preferable. In addition, when forming the said phase, it is preferable to use what mixed the liquid crystal compound which shows a nematic liquid crystal phase, and the chiral agent (chiral agent) mentioned later.

Next, the positional relationship of the in-plane slow axis in the twist retardation layer will be described in detail with reference to FIG. The black arrows in the twist retardation layer shown in FIG. 2 intend an in-plane slow axis.
The twisting direction of the liquid crystal compound is preferably determined by the spiral sense of the circularly polarized light reflecting layer described above, but may be right twist or left twist.
The twist angle of the liquid crystal compound is 360 ° or less. The lower limit is, for example, about 20 °. Among them, 50 to 200 ° is preferable and 50 to 100 ° is more preferable in that the effect of the present invention is more excellent. The twist angle corresponds to an angle θ between the in-plane slow axis at one surface 18 a in the twist retardation layer 18 in FIG. 2 and the in-plane slow axis at the other surface 18 b.

The product Δnd of the refractive index anisotropy Δn of the twist retardation layer measured at a wavelength of 550 nm and the film thickness d of the twist retardation layer is not particularly limited, but it is preferably 10 to 500 nm and more preferably 50 to 300 nm.

The type of liquid crystal compound used to form the twist retardation layer is not particularly limited. As the twist retardation layer, for example, a layer obtained by orientating a low molecular weight liquid crystal compound in a predetermined direction and then immobilizing it by photocrosslinking or thermal crosslinking is preferable.

Generally, liquid crystal compounds can be classified into rod-like types (rod-like liquid crystal compounds) and disk-like types (disk-like liquid crystal compounds and discotic liquid crystal compounds) according to their shapes. Furthermore, there are low molecular type and high molecular type, respectively. In general, a polymer refers to one having a degree of polymerization of 100 or more (Polymer physics / phase transition dynamics, Masao Doi, page 2, Iwanami Shoten, 1992). Any liquid crystal compound can also be used in the present invention. In addition, two or more types of rod-like liquid crystal compounds, two or more types of discotic liquid crystal compounds, or a mixture of a rod-like liquid crystal compound and a discotic liquid crystal compound may be used.

The twist retardation layer is more preferably formed using a liquid crystal compound (a rod-like liquid crystal compound or a disc-like liquid crystal compound) having a polymerizable group, since the change in optical properties due to temperature and / or humidity can be reduced. The liquid crystal compound may be a mixture of two or more types, in which case it is preferable that at least one has two or more polymerizable groups.
That is, the twist retardation layer is preferably a layer formed by fixing a liquid crystal compound having a polymerizable group by polymerization, and in this case, it is no longer necessary to exhibit liquid crystallinity after forming a layer.
The type of the polymerizable group contained in the liquid crystal compound is not particularly limited, and a functional group capable of addition polymerization reaction is preferable, and a polymerizable ethylenically unsaturated group or a ring polymerizable group is preferable. More specifically, (meth) acryloyl group, vinyl group, styryl group or allyl group is preferable, and (meth) acryloyl group is more preferable.
At this time, “(meth) acryloyl group” is a notation representing both an acryloyl group and a methacryloyl group.
The twist angle of the liquid crystal compound in the twist retardation layer can be adjusted by the type of chiral agent or the concentration thereof.

The thickness of the twist retardation layer is not particularly limited, but is preferably 0.5 to 10 μm, and more preferably 0.5 to 5.0 μm.

The formation method of a twist retardation layer is not specifically limited, A well-known method is mentioned. Among them, a liquid crystal composition containing a polymerizable liquid crystal compound and a chiral agent is coated on a predetermined substrate from the viewpoint of excellent productivity, and the polymerizable liquid crystal compound is twisted by heat treatment, and then light irradiation or light irradiation is performed. There is a method in which the polymerization of the polymerizable liquid crystal compound is advanced by heat treatment to be cured and the twist-oriented polymerizable liquid crystal compound is immobilized.
The conditions for the heat treatment are not particularly limited, and are preferably 50 ° C. to 120 ° C., and more preferably 60 ° C. to 100 ° C.
At the time of light irradiation, it is preferable to use ultraviolet light. The irradiation energy is preferably ^{20mJ / cm 2 ~ 50J / cm} 2, more preferably 100 ~ 1,500mJ / cm ^2.

The definition of the polymerizable liquid crystal compound is as described above.
The content of the polymerizable liquid crystal compound in the liquid crystal composition is preferably 80 to 99.9% by mass with respect to the solid content mass (mass excluding the solvent) of the liquid crystal composition, and 85 to 99. More preferably, it is 5% by mass.

The chiral agent is not particularly limited, and known compounds (for example, Liquid Crystal Device Handbook, Chapter 3 4-3, TN, chiral agents for STN, page 199, edited by Japan Society for the Promotion of Science 142th Committee, 1989) Description), isosorbide and isomannide derivatives can be used.
The chiral agent may also be a liquid crystal compound.
The content of the chiral agent in the liquid crystal composition is preferably 0.01 mol% to 200 mol%, and more preferably 1 mol% to 30 mol% of the amount of the liquid crystal compound (particularly, polymerizable liquid crystal compound).

The liquid crystal composition further includes other components (for example, a polymerization initiator, a solvent, a surfactant, an alignment control agent, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, and the like). It may be.

In addition, as a method of laminating a twist retardation layer and a circularly polarized light reflection layer, for example, a method of directly forming a twist retardation layer on a circularly polarized light reflection layer using the above-mentioned liquid crystal composition, and a temporary support The method of transcribe | transferring the twist retardation layer formed in (4) on a circularly polarized light reflection layer is mentioned.

<Other layers>
The vehicle image display function-equipped mirror 10 may include other layers other than the image display device 12, the 1⁄4 wavelength plate 14, the circularly polarized light reflection layer 16, and the twist retardation layer 18.
Hereinafter, optional members will be described in detail.

(Adhesive layer)
For example, the vehicle image display function mirror may include an adhesive layer for adhering each layer. The adhesive layer may be formed of an adhesive.
As the adhesive, there are a hot melt type, a thermosetting type, a photocuring type, a reactive curing type, and a pressure sensitive adhesive type which does not require curing from the viewpoint of curing system.

(Support)
The vehicle image display function mirror may include a support. The support may be used in the formation of the above-mentioned quarter-wave plate, cholesteric liquid crystal layer and twist retardation layer, and may constitute a part of the mirror with an image display function for a vehicle as it is.
Examples of the support include polyesters such as polyethylene terephthalate (PET), polycarbonates, acrylic resins, epoxy resins, polyurethanes, polyamides, polyolefins, cellulose derivatives, and plastic films such as silicones.
The thickness of the support may be about 5 to 1000 μm.

(Alignment layer)
The mirror with an image display function for vehicles may contain an orientation layer as a lower layer to which a liquid crystal composition is applied at the time of formation of a quarter wavelength plate, a cholesteric liquid crystal layer, and a twist phase contrast layer.
The thickness of the alignment layer is preferably 0.01 to 5.0 μm, more preferably 0.05 to 2.0 μm.
The liquid crystal composition may be coated on the surface of the temporary support or on the surface of the temporary support subjected to rubbing treatment without providing the alignment layer.

<Method of manufacturing mirror with image display function for vehicle>
The method for producing a mirror with an image display function for vehicles according to the present invention is not particularly limited, and, for example, a laminate including a twist retardation layer, a circularly polarized light reflection layer and a quarter wavelength plate on the image display surface of the image display device. It can be produced by bonding on the quarter wavelength plate side.
In addition, the manufacturing method of each layer is as having mentioned above.

<Use>
A mirror with an image display function for a vehicle can be used as a rearview mirror (inner mirror) of a vehicle. The vehicle image display function mirror may have a frame, a housing, a support arm for mounting on a vehicle body, and the like for use as a rearview mirror. Alternatively, the vehicle image display function mirror may be one that is shaped for incorporation into a rear view mirror.

The mirror with an image display function for vehicles may be plate-like or film-like, and may have a curved surface. The front surface of the vehicle image display function mirror may be flat or curved. It is also possible to make it the wide mirror which can visually recognize a back visual field etc. in a wide angle by curving and making a convex curve into the front side.
The curvature may be in the vertical direction, the horizontal direction, or the vertical direction and the horizontal direction. The curvature is usually 500 to 3000 mm, preferably 1000 to 2500 mm. The radius of curvature is the radius of the circumscribed circle when assuming the circumscribed circle of the curved portion in the cross section.

<< Second embodiment >>
Hereinafter, a second embodiment of the mirror with an image display function for a vehicle according to the present invention will be described with reference to the drawings. FIG. 3 shows a cross-sectional view of a second embodiment of the mirror with an image display function of the present invention.
The mirror 100 for an image display function for a vehicle includes an image display device 12, a quarter wavelength plate 14, a circularly polarized light reflection layer 16 including a cholesteric liquid crystal layer, a twist retardation layer 18, and a front plate 26 in this order Include. The circularly polarized light reflection layer 16, the twist retardation layer 18, and the front plate 26 constitute the vehicle mirror of the present invention. The front plate 26 is on the viewing side.
Since the mirror 100 with the image display function for vehicles shown in FIG. 3 includes the same layer as the mirror 10 with the image display function shown in FIG. 1 except that the front plate 26 is included, Are attached with the same reference numerals, the description thereof is omitted, and the configuration of the front plate 26 will be described in detail below.

<Front plate>
The front plate may be larger than, the same as, or smaller than the twist retardation layer. The twist retardation layer may be bonded to a part of the front plate, and other types of reflective layers such as metal foil may be bonded or formed on other portions.
On the other hand, the twist retardation layer may be disposed on the entire surface of the front plate. That is, by forming the front plate, the twist retardation layer, the circularly polarized light reflection layer, and the image display unit of the image display device as the same area, image display on the entire surface of the mirror is also possible.

The type of front plate is not particularly limited. The front plate includes a glass plate or a plastic plate used for producing a conventional mirror. The front plate is preferably transparent in the visible light range and has a small birefringence. Examples of the plastic film include polyesters such as polyethylene terephthalate (PET), polycarbonates, acrylic resins, epoxy resins, polyurethanes, polyamides, polyolefins, cellulose derivatives, silicones, and the like.
Among them, a glass plate is preferable as the front plate.

A preferred embodiment of the front plate is a front plate having a haze of 1 or less. The haze is more preferably 0.1 or less. The lower limit is not particularly limited.
If the haze is within the above range, the visibility of the image is further improved.
As a method of measuring the haze, a general haze meter can be used, and for example, NDH4000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.) can be mentioned as a measuring device.
The thickness of the front plate may be about 100 μm to 10 mm, preferably 200 μm to 5 mm, and more preferably 500 to 1000 μm.

<Method of producing mirror 100 with image display function for vehicle>
For example, after forming a twist retardation layer, a circularly polarized light reflection layer, and a quarter-wave plate in this order from the front plate side on the front plate, the mirror 100 with an image display function for a vehicle is obtained Alternatively, after a laminate is obtained by sequentially transferring a quarter wavelength plate, a circularly polarized light reflection layer, and a twist retardation layer formed on a temporary support to a front plate, the image display surface of the image display device In addition, the laminate can be manufactured by bonding on the quarter wavelength plate side.

<< Third Embodiment >>
Hereinafter, a third embodiment of the mirror with an image display function for a vehicle according to the present invention will be described with reference to the drawings. FIG. 4 shows a cross-sectional view of a third embodiment of the mirror with an image display function for a vehicle according to the present invention.
A mirror 120 with an image display function for vehicle includes an image display 12, a quarter wavelength plate 14, a circularly polarized light reflection layer 16 including a cholesteric liquid crystal layer, a transparent substrate 28, a twist retardation layer 18, and a front plate And 26 in this order. That is, the twist retardation layer 18 is disposed between the transparent substrate 28 and the front plate 26. Here, the vehicle mirror of the present invention is constituted by the circularly polarized light reflection layer 16, the transparent substrate 28, the twist retardation layer 18 and the front plate 26. The front plate 26 is on the viewing side.
A mirror 120 for an image display function for a vehicle shown in FIG. 4 includes the same layers as the mirror 100 for an image display function shown in FIG. 3 except that the transparent substrate 28 is included. Are attached with the same reference numerals, the description thereof is omitted, and the configuration of the transparent substrate 28 will be described in detail below.

<Transparent substrate>
The type of transparent substrate is not particularly limited. As a transparent substrate, the glass plate or plastic plate used for preparation of a normal mirror is mentioned. The transparent substrate is preferably transparent in the visible light range and has a small birefringence. As a kind of transparent substrate, specifically, the same one as the front plate described above can be mentioned. Among them, a glass plate is preferable as the transparent substrate.

The transparency of the transparent substrate is preferably 1 or less. The haze is more preferably 0.1 or less. The lower limit is not particularly limited. The method of measuring the haze is as described above.
The thickness of the transparent substrate may be about 100 μm to 10 mm, preferably 200 μm to 5.0 mm, and more preferably 500 to 1000 μm.

<Method of producing mirror 120 with image display function for vehicle>
The image display function-equipped mirror 120 for a vehicle includes, for example, a laminate 1 obtained by forming a twist retardation layer on a front plate, and a circularly polarized light reflection layer and a quarter wavelength plate on the transparent substrate side on a transparent substrate. The laminate 2 obtained by forming in this order can be manufactured by bonding to the image display surface of the image display device. The laminate 1 is adhered to the laminate 2 on the twist retardation layer side. In addition, the laminate 2 is bonded to the image display device on the quarter wavelength plate side.
In addition, when the types of the transparent substrate and the front plate are both glass, as a method of manufacturing the mirror 120 with an image display function for a vehicle, first, a laminated glass having a twist retardation layer sandwiched is produced, and this laminated glass May be bonded to another member.

<< Fourth embodiment >>
Hereinafter, a fourth embodiment of the mirror with an image display function for a vehicle according to the present invention will be described with reference to the drawings. FIG. 5 shows a cross-sectional view of a fourth embodiment of the mirror for image display function for a vehicle according to the present invention.
A mirror 140 with an image display function for a vehicle includes an image display 12, a quarter wavelength plate 14, a transparent substrate 28, a circularly polarized light reflection layer 16 including a cholesteric liquid crystal layer, a twist retardation layer 18, and a front plate And 26 in this order. That is, the twist retardation layer 18 and the circularly polarized light reflection layer 16 are disposed between the transparent substrate 28 and the front plate 26. The transparent substrate 28, the circularly polarized light reflection layer 16, the twist retardation layer 18, and the front plate 26 constitute the vehicle mirror of the present invention. The front plate 26 is on the viewing side.
The mirror 140 for an image display function for vehicles shown in FIG. 5 includes the same layers as the mirror 120 for an image display function shown in FIG. 4 except that the arrangement of the transparent substrate 28 is different. The same reference numerals are assigned to the elements, and the description thereof is omitted.

<Method of producing mirror 140 with image display function for vehicle>
The image display function-equipped mirror 140 for a vehicle is, for example, a laminate 3 obtained by forming a twist retardation layer and a circularly polarized light reflection layer in this order from the front plate side on the front plate, and 1/4 on the transparent substrate. The laminate 4 obtained by forming the wave plate can be manufactured by bonding to the image display surface of the image display device. The laminate 4 is bonded to the laminate 5 on the side of the circularly polarized light reflection layer. In addition, the laminate 5 is bonded to the image display device on the quarter wavelength plate side.

<< Other Embodiments >>
In the first to fourth embodiments, the circularly polarized light reflecting layer including the cholesteric liquid crystal layer is shown as the circularly polarized light reflecting layer, but the circularly polarized light reflecting layer is not limited to this embodiment. It may be a circularly polarized light reflective layer including a reflective linear polarizer (hereinafter also referred to as a reflective linear polarizer).
In addition to the circularly polarized light reflection layer 16, the twist retardation layer 18, and optionally the front plate 26 and the transparent substrate 28, the vehicle mirror of the present invention includes other layers (for example, an adhesive layer, a support, an orientation layer , And a quarter wave plate etc.) may be further included.

Hereinafter, the present invention will be more specifically described by way of examples. Materials, reagents, substance amounts and proportions thereof, operations, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Accordingly, the scope of the present invention is not limited to the following examples.

Example 1 Production of Vehicle Mirror (Half Mirror)
(Preparation of coating solution for quarter-wave plate)
The components shown below were mixed to prepare a coating solution for a quarter wave plate.
-Rod-like liquid crystal compound shown below: 100 parts by mass of compound 1-Initiator: 4 parts by mass of IRGACURE 819 (manufactured by BASF)-Alignment control agent shown below: 0.1 parts by mass of compound 2-Crosslinking agent: A-TMMT ( Made by Shin-Nakamura Chemical Co., Ltd. 1 part by mass Solvent: 2-butanone (manufactured by Wako Pure Chemical Industries, Ltd.) 170 parts by mass

The crosslinking agent "A-TMMT" is intended to be pentaerythritol tetraacrylate.

The compound 2 was produced by the method described in JP-A-2005-99248.

(Preparation of coating solution for circularly polarized light reflective layer)
<< Preparation of Coating Liquid 1 for Cholesteric Liquid Crystal Layer >>
The components shown below were mixed to prepare a coating liquid 1 for a cholesteric liquid crystal layer. The central wavelength ("selective reflection center wavelength") of the selective reflection band of the cholesteric liquid crystal layer formed by the coating liquid 1 for the cholesteric liquid crystal layer is 630 nm. The produced cholesteric liquid crystal layer was a right circularly polarized light reflection layer.
The above rod-like liquid crystal compound: 100 parts by mass of compound 1 Chiral agent for right twist: PARIO COLOR LC756 (manufactured by BASF AG)
4.7 parts by mass-Initiator: 4 parts by mass of IRGACURE 819 (manufactured by BASF Corp.)-Alignment control agent: 0.1 parts by mass of compound 2-Crosslinking agent: 1 part by mass of A-TMMT (manufactured by Shin-Nakamura Chemical Co., Ltd.) Solvent: 2-butanone (manufactured by Wako Pure Chemical Industries, Ltd.) 170 parts by mass

<< Preparation of Coating Liquid 2 for Cholesteric Liquid Crystal Layer >>
The components shown below were mixed to prepare a coating liquid 2 for a cholesteric liquid crystal layer. The central wavelength ("selective reflection center wavelength") of the selective reflection band of the cholesteric liquid crystal layer formed by the coating liquid 2 for cholesteric liquid crystal layer is 540 nm. The produced cholesteric liquid crystal layer was a right circularly polarized light reflection layer.
The above rod-like liquid crystal compound: 100 parts by mass of compound 1 Chiral agent for right twist: PARIO COLOR LC756 (manufactured by BASF AG)
5.5 parts by mass Initiator: IRGACURE 819 (manufactured by BASF) 4 parts by mass Alignment control agent: 0.1 part by mass Compound 2 Crosslinking agent: A-TMMT (manufactured by Shin-Nakamura Chemical Co., Ltd.) 1 part by mass Solvent: 2-butanone (manufactured by Wako Pure Chemical Industries, Ltd.) 170 parts by mass

<< Preparation of Coating Liquid 3 for Cholesteric Liquid Crystal Layer >>
The components shown below were mixed to prepare a coating liquid 3 for a cholesteric liquid crystal layer. The central wavelength ("selective reflection center wavelength") of the selective reflection band of the cholesteric liquid crystal layer formed by the coating liquid 3 for the cholesteric liquid crystal layer is 450 nm. The produced cholesteric liquid crystal layer was a right circularly polarized light reflection layer.
The above rod-like liquid crystal compound: 100 parts by mass of compound 1 Chiral agent for right twist: PARIO COLOR LC756 (manufactured by BASF AG)
6.7 parts by mass Initiator: IRGACURE 819 (manufactured by BASF) 4 parts by mass Alignment control agent: 0.1 parts by mass Compound 2 Crosslinking agent: A-TMMT (manufactured by Shin-Nakamura Chemical Co., Ltd.) 1 part by mass Solvent: 2-butanone (manufactured by Wako Pure Chemical Industries, Ltd.) 170 parts by mass

(Production of Laminate A)
«Formation of quarter-wave plate»
A PET (polyethylene terephthalate) film (Cosmo Shine A4100, thickness: 100 μm) manufactured by Toyobo Co., Ltd. is prepared as a temporary support (280 mm × 85 mm), and the surface of the temporary support is rubbed (rayon cloth, pressure: 0.1 kgf) (0. 98 N), rotation speed: 1000 rpm, conveyance speed: 10 m / min, frequency: 1 reciprocation).

Next, a coating solution for a quarter wave plate was applied to the rubbing-treated surface of the PET film using a wire bar to form a coating, which was then dried. Place the obtained coated film with PET film on a hot plate at 30 ° C., and apply 6 seconds to the above coating film with an electrodeless lamp “D bulb” (60 mW / cm ² ) manufactured by Fusion UV Systems Inc. UV (ultraviolet) radiation was performed to fix the cholesteric liquid crystal phase. According to the above procedure, a 1⁄4 wavelength plate with a film thickness of 0.8 μm was obtained.

«Formation of circularly polarized light reflection layer»
A circularly polarized light reflective layer was laminated on the obtained temporary support-equipped quarter-wave plate according to the procedure described later. The circularly polarized light reflection layer includes a cholesteric liquid crystal layer 1 having a central wavelength of a selective reflection band in the wavelength range of red light, a cholesteric liquid crystal layer 2 having a central wavelength of a selective reflection band in the wavelength range of green light, and blue light The three-layer configuration with the cholesteric liquid crystal layer 3 having the central wavelength of the selective reflection band in the wavelength range of

The coating liquid 1 for cholesteric liquid crystal layers was apply | coated to a quarter wavelength plate surface using a wire bar, the coating film was formed, and this was dried. The obtained coated film with a coated film is placed on a hot plate at 30 ° C., and for 6 seconds with respect to the above-mentioned coated film using an electrodeless lamp “D bulb” (60 mW / cm ² ) manufactured by Fusion UV Systems Inc. The cholesteric liquid crystal phase was fixed by carrying out UV (ultraviolet) irradiation of the above to obtain a cholesteric liquid crystal layer 1 having a film thickness of 3.5 μm. Furthermore, the same steps were repeated using the coating liquid 2 for the cholesteric liquid crystal layer and the coating liquid 3 for the cholesteric liquid crystal layer in this order. According to the above procedure, a laminate (laminate A) of a temporary support-equipped quarter-wave plate and a circularly polarized light reflection layer composed of three cholesteric liquid crystal layers was obtained.

In the laminate A, the film thickness of the cholesteric liquid crystal layer 2 was 3.0 μm, and the film thickness of the cholesteric liquid crystal layer 3 was 2.7 μm.
The transmission spectrum of the layered product A was measured by a spectrophotometer (V-670, manufactured by JASCO Corporation), and transmission spectra having reflection peaks at 630 nm, 540 nm, and 450 nm were obtained.

(Preparation of coating solution for twist retardation layer)
The components shown below were mixed in a container kept at 25 ° C. to prepare a coating solution 1 for twist retardation layer.
・ A mixture of liquid crystal compound 1 shown below and liquid crystal compound 2 shown below (composition ratio: liquid crystal compound 1 / liquid crystal compound 2 = 80 mass% / 20 mass%) 1 g
-Chiral agent 2 3 mg shown below
・ Horizontal alignment agent 1 1 mg shown below
-Initiator: IRGACURE 907 (manufactured by BASF) 40 mg
-MEK (methyl ethyl ketone) 1.6 g

(Formation of twist retardation layer 1)
The prepared coating solution 1 for a twist retardation layer was applied to the surface of the circularly polarized light reflective layer of the obtained laminate A using a wire bar, and a coating film was obtained by drying at room temperature. The obtained coated laminate A was allowed to stand on a hot plate at 100 ° C. for 1 minute to perform heat treatment of the coating.
Next, UV irradiation was performed for a fixed time at room temperature under a nitrogen atmosphere (oxygen concentration of 500 ppm or less) on the coated film after the heat treatment to cure the coated film. According to the above-described procedure, a laminate (laminate B) of a twist retardation layer having a film thickness of 1.25 μm and the laminate A was formed.
Then, a glass substrate (thickness: 1 mm, manufactured by Matsunami Glass Industrial Co., Ltd.) was bonded via an adhesive (thickness: 30 μm, manufactured by Soken Chemical Co., Ltd., “SK2057”) to face the twist retardation layer in the obtained laminate B After that, only PET manufactured by Toyobo Co., Ltd., which is a temporary support, was peeled off.

The obtained twist retardation layer contained a liquid crystal compound twisted and oriented along a helical axis extending along the thickness direction, and the twist angle of the liquid crystal compound was 70 ° (see FIG. 2). The twist angle θ of the liquid crystal compound of the twist retardation layer was measured by the method described later.
The cholesteric liquid crystal layer 1, the cholesteric liquid crystal layer 2, the cholesteric liquid crystal layer 3, and the twist retardation layer all have the same helical sense (right twist).

(Measurement of twist angle θ in twist retardation layer)
The twist angle θ in the twist retardation layer was measured by the following method.
As a temporary support (280 mm × 85 mm), a PET (polyethylene terephthalate) film (Cosmo Shine A4100, thickness: 100 μm) manufactured by Toyobo Co., Ltd. was prepared, and the surface of the temporary support was subjected to rubbing treatment.
The coating solution 1 for the twist retardation layer was coated on the temporary support using a wire bar, and dried at room temperature to obtain a coated film. The obtained film-coated temporary support was allowed to stand on a hot plate at 100 ° C. for 1 minute to carry out heat treatment of the film.
Next, UV irradiation was performed for a fixed time at room temperature under a nitrogen atmosphere (oxygen concentration of 500 ppm or less) on the coated film after the heat treatment to cure the coated film. According to the above-described procedure, a twist retardation layer having a thickness of 1.25 μm was formed.
Subsequently, a temporary support with a twist retardation layer was cut out to a sample size of 50 mm × 50 mm. Next, using a commercially available adhesive “SK 2057”, the twisted retardation layer in the cut temporary support with twisted retardation layer was transferred to an optical glass to prepare a measurement sample.
The obtained measurement sample was measured using AxoScan OPMF-1 (manufactured by Opto Science), and the twist angle θ of the liquid crystal compound in the twist retardation layer was determined using the attached device analysis software.

[Example 2 and Example 3: Production of Vehicle Mirror (Half Mirror)]
A coating solution for twist retardation layer was prepared in the same manner as in the preparation of coating solution 1 for twist retardation layer except that the amount of chiral agent 2 was changed to the amount shown in Table 1. Subsequently, the mirror for a vehicle (half mirror) of Example 2 and Example 3 was produced by the method similar to Example 1 using each obtained coating liquid for twist phase difference layers.
In the twist retardation layer in the vehicle mirror of Example 2, the twist angle θ was 120 °. Further, in the twist retardation layer in the vehicle mirror of Example 3, the twist angle θ was 40 °.

Comparative Example 1: Production of Vehicle Mirror (Half Mirror)
A vehicle mirror (half mirror) of Comparative Example 1 was produced in the same manner as in Example 1 except that the twist retardation layer was not formed.

[Production of mirror with image display function for vehicles]
An image display was further adhered to the obtained vehicle mirrors of Examples 1 to 3 and Comparative Example 1, and mirrors for the vehicle with an image display function of Examples 4 to 6 and Comparative Example 2 were produced. .
Below, the concrete preparation method of the mirror with a picture display function for vehicles is shown.
The vehicle manufactured in the above manner such that the twist retardation layer, the circularly polarized light reflection layer, the quarter wavelength plate, and the image display device are in this order on the surface of the image display unit of the image display device (iPad (registered trademark) Retina) The mirror for the vehicle was adhered, and the mirror with the image display function for vehicles was produced. At this time, the slow axis of the quarter-wave plate was disposed at an angle of 45 degrees with respect to the transmission axis of the image display device (polarization direction of light emission of LCD (liquid crystal display)).

[Evaluation of unevenness of mirror reflection image]
The mirror with an image display function produced above was attached at the position of the inner mirror of a vehicle (vehicle type: Honda's 2002 model step wagon) so that the twist retardation layer is closest to the driver's seat (observer). The mirror reflection image which can be confirmed from the observer of the driver's seat in a state where sunlight is incident on the position of the inner mirror from the rear glass (100 × 50 cm) of the vehicle was evaluated according to the following criteria. In addition, the evaluation was made in the vicinity of the center of the glass member (a part where unevenness is uniformly generated). The results are shown in Table 1.
(Evaluation criteria)
"A": The lightness-and-dark unevenness of the light in the shape of oblique lines to be recognized is less than 10% (the unevenness in the lightness and darkness of the oblique lines is hardly recognized)
"B": 10% or more and less than 50% of light and dark unevenness of hatched light can be visually recognized "C": 50% or more and less than 90% of light and dark unevenness of hatched light can be visually recognized "D": light of hatched shape 90% or more of the light and dark unevenness can be visually recognized Note that, for example, when 10% or more of the light and dark unevenness of hatched light can be visually recognized, the unevenness can be visually recognized in the area of 10% or more of the visual field range under the above conditions. Intended.

From the results shown in Table 1, it can be seen that in Examples 4 to 6 in which the twist retardation layer is used, unevenness due to birefringence of the rear glass of the mirror reflection image is difficult to visually recognize. Furthermore, in particular, when the twist angle of the liquid crystal compound in the twist retardation layer is 50 to 200 ° (more preferably 50 to 100 °), unevenness due to birefringence of the rear glass of the mirror reflection image becomes more difficult to visually recognize. That was confirmed.

10, 100, 120, 140 Mirror with Image Display Function for Vehicle 12 Image Display Device 14 Quarter Wave Plate 16 Circularly Polarized Reflective Layer 18 Twisted Retardation Layer 18a One Surface in Twisted Retardation Layer 18 18b Twisted Retardation Layer 18 other surface 20 first cholesteric liquid crystal layer 22 second cholesteric liquid crystal layer 24 third cholesteric liquid crystal layer 26 front plate 28 transparent substrate

Claims

A vehicle mirror comprising: a retardation layer formed by fixing a liquid crystal compound twisted and oriented at a twist angle of 360 ° or less along a helical axis extending along a thickness direction; and a circularly polarized light reflection layer.
The vehicle mirror according to claim 1, wherein the twisting angle is 50 to 200 °.
The vehicle mirror according to claim 1 or 2, wherein the twisting angle is 50 to 100 °.
The vehicle mirror according to any one of claims 1 to 3, wherein the circularly polarized light reflection layer includes a cholesteric liquid crystal layer.
In addition, including the front plate,
The vehicle mirror according to any one of claims 1 to 4, wherein the front plate, the retardation layer, and the circularly polarized light reflection layer are disposed in this order.
Furthermore, it includes a transparent substrate,
The vehicle mirror according to claim 5, wherein the front plate, the retardation layer, the transparent substrate, and the circularly polarized light reflection layer are disposed in this order.
Furthermore, it includes a transparent substrate,
The vehicle mirror according to claim 5, wherein the front plate, the retardation layer, the circularly polarized light reflection layer, and the transparent substrate are disposed in this order.
A vehicle mirror according to any one of claims 1 to 7 and an image display device,
A mirror with an image display function for a vehicle, in which the retardation layer, the circularly polarized light reflection layer, and the image display device are arranged in this order.
The mirror with an image display function for a vehicle according to claim 8, further comprising a quarter wave plate between the mirror for a vehicle and the image display device.
The mirror with an image display function for a vehicle according to claim 9, wherein the circularly polarized light reflection layer and the quarter wavelength plate are in direct contact with each other.