WO2001087585A1

WO2001087585A1 - Inkjet papers incorporating zirconium salts

Info

Publication number: WO2001087585A1
Application number: PCT/US2000/027561
Authority: WO
Inventors: J. Craig White; Scott C. Peterson; Bernard W. Wolff
Original assignee: Hopton Technologies, Inc.
Priority date: 1999-10-05
Filing date: 2000-10-05
Publication date: 2001-11-22
Also published as: AU8638001A

Abstract

A new color recording paper for non-impact printers comprises a paper substrate coated with a zirconium salt-containing coating composition. The use of the zirconium salt improves color printing quality with non-impact printers, especially ink jet printer. The coating composition further comprises calcium carbonate, starch, and styrene maleic anhydride salt.

Description

INKJET PAPERS INCORPORATING ZIRCONIUM SALTS

FIELD OF THE INVENTION

This invention relates to a new color recording paper for non-impact

printers, more particularly a color recording paper coated with a coating

composition which comprises a zirconium salt, and a method of making the

color recording paper. The new color recording paper has improved color

printing quality and prevent inks from migrating and bleeding during the

printing process. This invention also relates to an ink jet recording paper for

recording with a water-based ink, and in particular to an ink jet recording

paper which provides high recording quality.

BACKGROUND OF THE INVENTION

In ink jet recording, small ink drops are released by a variety of

different mechanisms so as to form a dot image on the printing paper. Unlike

the case of dot impact printing, this method is not noisy, makes it easy to

obtain full color images, and permits printing to be performed at high

speeds. However, as the ink used in ink jet recording is usually a water-

based ink based on a direct dye or acidic dye, that typically has poor drying

properties. The main characteristics required of the paper used in ink jet recording are as follows: (1) Permits fast ink drying; (2) permits high

printing speeds; and (3) gives little spreading, tailing or blurring of dots.

Property (1) was improved by providing an ink jet recording layer

comprising a silica of large specific surface area so as to increase ink

absorption. However, if the ink absorption is increased too much, the print

density falls.

Because of recent progress in ink jet printers and more diverse needs,

a- requirement has emerged for better resolution and higher image quality.

However, using an ink jet recording paper having a recording layer with a

pigment of large specific surface area, results in a recording layer surface

having low smoothness. As a result, the appearance of the image was

lacking in quality, the dots were not perfect circles, and the reproducibility

of the image was unsatisfactory.

To improve the smoothness of the recording layer surface,

conventional pigment-coated ink jet recording papers were given a

supercalender treatment or other treatment. This improved gloss and

smoothness, but the porous structure of the ink jet recording layer was

destroyed. Consequently, ink absorption amount and ink absoφtion speed

declined, and drying properties were poorer.

Ink jet recording papers are mainly divided into -two groups; one is the plain type ink jet recording paper, which- consists of only cellulosic fibers or

of cellulosic fibers and a filler in order that inks may be absorbed in the

space between fibers or spaces which are formed fiber and filler, and the

other is the coated type ink jet recording paper, which consists of paper, a

substrate, and coating materials, which consists of pigment and binder, in

order that inks may be absorbed in a fine void of the coating layer. Although

the coated type recording paper provides a small spread and a circular form

of ink dot, as well as a high resolution power, it has poor ink absoφtivity

capacity and slow ink absoφtion rate. Hence the paper has the drawback that

it is unsuitable for the multi-color printing of a large amount of ink and too

expensive.

There are also resin-coated ink jet recording papers which have a

relatively smooth surface. However, as this type of paper contains almost no

pigments of large specific surface area, ink absoφtion amount and

absoφtion speed were low. In ink jet recording, aqueous ink where a dye is

dissolved in water are used, but if the water adheres to the paper, the image

tends to blur and run after printing. In the case of resin-coated papers, water-

soluble resins are generally used, so this tendency was particularly acute.

Also, other difficulties are encountered when printing paper sheets

with non-impact printers using color inks, If the paper sheet is lightly sized, the ink penetrates excessively into the sheet interior, resulting in poor color

density or poor brightness of color shade. Alternatively, if the paper sheet is

sized sufficiently to impart good color density, the color inks do not

penetrate into the sheet, and migrate together with an effect referred to as

"bleeding" or "feathering" ( inks bleeding outward from application point).

Efforts have been made by trying to add pigments such as calcium

carbonate, talc and kaolin into the paper in order to improve color density

and bleeding. The puφose of the addition of the pigments is to close the

surface of the paper or sheet to prevent excessive ink penetration into the

paper while providing voids between pigments to absorb the ink carriers.

However, adding such pigments in a surface sizing composition or a coating

composition is not desirable for multiple application paper sheets due to its

adverse effect on xerographic performance. Under certain circumstances,

adding pigments to a surface sizing composition is just impractical.

In current attempts to produce a paper sheet capable of producing near

photographic quality ink jet or non-impact printed images, silica based

pigments are added in a coating composition which requires non-traditional

pigment binders. Silica based pigments also present problems. Not only they

are expensive, but also difficult to hold in the coating forming dust which is

harmful to workers, and they abrade machine surfaces. The non-traditional pigment binders are not typically used in paper making and they are

expensive too. Therefore, the cost to produce a sheet with these atypical

additives is higher compared with paper produced with standard additives.

It has been suggested that the use of zirconium salts in- a sizing

composition can improve the surface sizing property in paper making.

US 4400440, issued to Shaw, describes a method of coating a paper

substrate in which a thin coating of a reactive film forming resin is applied

to the paper and the resin reacted with an ammonium zirconyl complex. This

treatment avoids blocking or sticking together of successive layers of paper

coated with relatively low glass transition temperature film forming resins.

US 4092457, issued to Fujita et al., describes a synthetic fiber paper

having an improved printability for offset printing. The paper is treated with

an aqueous composition containing water soluble polymer, a copolymer and

a salt of a polyvalent metal, such as zirconium.

US 3930074, issued to Drelich et al., describes a synthetic resin

composition containing zirconyl complex salt and a method of applying the

same composition onto porous absorbent materials for controlling migration,

spreading or penetration thereof.

US 5362573 and 5472485, issued to Pandian et al, describes an

aqueous surface sizing composition containing a compound selected from alkenyl succinic anhydrides, alkyl ketene dimers and mixtures thereof and a

metal salt, such as zirconium salt. The use of the sizing compositions during

paper making provides paper products with superior liquid storage

properties.

The inventors of the instant subject matter have found that including

zirconium salts in unpigmented or pigmented surface sizing composition, or

in fine paper coating composition , has a beneficial effect on color density

and bleeding/feathering when water based inks are applied through non¬

impact methods such as ink jet printing. Benefits are seen in unpigmented

surface sized sheets for multiple use, and with specialty paper sheets

intended for high quality ink jet applications.

After carrying out many studies on ink jet recording papers to solve

the aforesaid problems, the Inventors found it was possible to obtain a

recording surface that confers water resistance an improved ink-bleed. These

discoveries led to the present invention.

OBJECTS OF THE INVENTION

It is an object of the present invention to provide a color recording

paper for non-impact printers having improved color printing quality. It is a further object of the present invention to provide a color

recording paper for non-impact printers that prevent ink bleeding during the

printing process.

It is another object of the present invention to provide a method for

improving the color printing quality in a paper for non-impact printers.

A still further object of the invention is to provide a method for

preventing ink bleeding in a paper for non-impact printers.

Still, another object of the present invention is to provide a coating

composition comprising a zirconium salt, an alkaline carbonate, a binder,

and a salt of a styrene/ maleic anhydride copolymer.

SUMMARY OF THE INVENTION

The present invention relates to a color recording paper for non¬

impact, printers comprised of a paper substrate coated with a coating

composition which comprises a zirconium salt in an effective amount to

improve color printing quality and prevent ink bleeding during the printing

process. The instant invention is also directed to a method for improving the

color printing quality and preventing ink bleeding in a paper for non-impact

printers, which comprises coating said ink jet paper with a composition

containing a zirconium salt in an effective amount to improve color printing

quality and prevent ink bleeding during the printing process.

The present invention further relates to the use of zirconium salts to

improve color printing with non-impact printers including inkjet printers.

Zirconium ions contained within the applied surface treatment of paper form

chemical bonds with reactive sites such as carboxyl groups on ink carriers.

The bonding action immobilizes the ink carriers when the ink is applied to

the sheet surface.

As a result of adding zirconium salts to the surface treatment of the

paper, the ink is held more closely to the surface through the immobilization

of the dye and ink pigments. Furthermore, due to the ability of zirconium

salts to prevent resolubilization of coatings the ink bleed and feathering are

reduced when the ink is applied to the sheet.

DETAILED DESCRIPTION OF THE INVENTION

The ink jet recording paper of the present invention contains one or

more layers; that is, it is produced by supeφosing a plurality of ink-receptive layers either on one or both sides of at least one base layer, or combining a

base layer and an ink-receptive layer. The function required for the base

layer is mainly to prevent inks coming into the ink-receptive layer from

further penetrating deeply and rapidly. Concretely, in order to achieve the

function, the opacity and the sizing degree are important factors. To be

exact, the opacity is desirable to be 75% and over, and the sizing degree

measured in terms of the Stockigt sizing degree is preferable to be 3 seconds

and over. When the recording inks have passed through the ink-receptive

layer and reached the base layer of which the opacity is 75% or over, the

show through that is observed from the back side of the ink jet recording

paper, is reduced and hence the print through becomes lessened too. Also, in

the case that the Stockigt sizing degree is 3 seconds or over, inks having

passed through the ink-receptive layer and reached the base layer are

prevented from further penetrating into the base layer near its surface (strike

through), with the result that the print through is improved. However, when

the sizing degree is extremely high, and a large amount of ink is applied, the

ink-receptive layer cannot afford to hold the ink anymore.When the sizing

degree is too low, ink penetrates into the base layer so deeply that the print

through becomes noticeable. Also, with the decrease of ink staying in the

ink-receptive layer, the density declines, and the clarity of recorded images is reduced, which is undesirable. For these reasons, the sizing degree is

desirable to be in a so-called weak sizing degree, although it has to be 3

seconds and over.

The ink-receptive layer has to be provided with good ink-absorbency

and enough to hold plentiful ink from multi-colored recording. Additionally,

it must be good in color-reproducibility, and can give uniform images and

increased optical density. Therefore, the ink-receptive layer should consist of

a^" material having good affinity for inks, and it should be a porous layer

having a uniform thickness and higher transparency as described hereinafter.

If the ink-receptive layer lacks in affinity with ink's solvents, not only will

the ink not be absorbed but also its drying is retarded, and accordingly the

ink flows out and the recorded images are so easily damaged by abrasion

that this kind of layer becomes unsuitable for multi-colored recording using

plentiful ink. Likewise, if any material in the ink-receptive layer has little

affinity for ink-dyes, the inks will not fix in the material and therefore some

portions of the ink dots are not dyed, with the result that uniform images

cannot be produced. For these reasons, when an aqueous ink is used for ink

jet recording, the addition of more than a certain amount of sizing agent to

the ink-receptive layer deteriorates the penetration and the drying of water as

solvent and therefore the object of this invention cannot be fully

π accomplished. Likewise, if such material as synthetic pulp having little

affinity for water and dyes is contained in the ink-receptive layer exceeding

a certain quantitative limit, uniform images cannot be produced because the

material leaves some portions in the ink dots unfixed, which performs the

object of this invention impossible.

Since the color inks are produced in accordance with the principle of

color substraction, it is unexpected that the less light scattering is in the ink-

receptive layer, i.e., the more transparent the ink-receptive layer is, the better

the ink's color reproducibility becomes and the clearer the images look.

When the surfaces of the recorded ink- receptive layer is exposed to a certain

amount of light energy, the light energy is sufficiently absorbed. Thereby,

the less the light is scattered, the better the color reproduction and the higher

the color density become.

The ink-receptive layer of this invention comprises pulp, filler,

retention aid, a zirconium salt and auxiliary agent, such as water-soluble

resin etc., which control the paper qualities or productivity. The pulp in the

ink-receptive layer includes wood pulp, linter pulp, and recycled pulp from

waste paper. Unlike the base layer, such pulp or fiber that has not affinity

with ink's solvents or dyes cannot be used for the ink-receptive layer.

Therefore, glass fiber or synthetic pulp, which may be mixed in the base layer, should not be mixed in the ink-receptive layer. A similar kind of fillers

to those used in the base layer may be used for the ink-receptive layer as

well. In selecting from those fillers, care must be taken in such a way as to

increase the ink-absorbency and lessen the light scattering of the ink-

receptive layer.

As for the transparency of the ink-receptive layer, fillers should not

necessary be used. However, it is rather desirable to use filler so as to further

increase the ink-absorbency, and control and spread and form of ink dots in

order to give clear images, high color density and high resolution. In this

connection, experiments revealed that ground calcium carbonate pulverized

to medium size is more desirable than precipitated calcium carbonate or

synthetic silica.

The reason for this is unclear yet, but it seems to the present inventors

that very fine filler such as precipitated calcium carbonate and silica adheres

to fiber and thereby increase the light scattering and reduce the transparency

of the ink-receptive layer, whereas the medium-sized ground calcium

carbonate does not deteriorate the transparency of the ink-receptive layer so

much as the fine filler because it adheres to fiber less than they do, and most

of them lie in a space between fibers.

The term "transparency", as far as it is used in this invention, means an extent to which incident light in the ink-receptive layer is scattered

thereby; in this sense, the more incident light is scattered in the ink-receptive

layer, the lower the transparency thereof becomes, whereby recorded images

look whitish as much.

Thus, this transparency can be represented in terms of the specific

light scattering coefficient (S) of the Kubelka-Munk equation, which

indicates the degree of light scattering. In connection with the specific light

scattering coefficient, wood pulp is 200-700 cm /g, synthetic pulp is 900-

1300 cmVg, and fillers are 600-1000 cm²/g on the average. These values (S)

differs with the kind of the materials by the treatment processes and or the

particle size of material; therefore, some of the above-mentioned material

sometimes indicate greater coefficient than their average.

The value (S) decreases with the increase of pulp beating degree; thus,

in order to produce more vivid images by reducing light scattering in the

ink-receptive layer, it is desirable to use high beating pulp. However, when

the beating is too high, the vacant spaces for absorbing inks are decreased; in

consequence, they reduce the ink-absorbency of the ink-receptive layer.

From this point of view, excessively high beating is undesirable.

It is desirable to coat or saturate the ink-receptive layer with a solution

or dispersion of fine filler in order to produce clearer images and higher density. Alumina, aluminum hydroxide, silicate, and silica are desirable for

this puφose, and among these, synthetic silica is the best of all. Therefore,

synthetic silica, obtained by the precipitation process, the gel process, and

the vapor phase process, can be used as fine silica. In any case, when the

specific surface area of silica, determined by the B.E.T. method, is equal to

or greater than 150 m /g, and the particle size distribution thereof is of the

narrowest possible, images of high color density are produced.

In the case that such kind of fillers are used for coating or

impregnating method, a water-soluble resin or latex as a binder can be added

to them. Additionally, such additives as a viscosity control agent, an agent

for giving recorded images of a water-resistance, or an agent for controlling

the spread of dots can also be mixed in their coating color.

Among the water-soluble resin mentioned above are starch, cationic

starch, polyvinyla ohol, gelatin, alginate, hydroxyethylcellulose,

carboxymethylcellulose, polyacrylamide, polystyrene sulfonate,

polyacrylate, polyvinylpyridine, polyvinylpyrrolidone, polyethyleneoxide,

hydrolysis product of starch-acrylonitrile graftpolymer and the like. Among

these substances, a high water-absoφtive water-soluble resin can effectively

be used to improve not only the surface binding strength but also the ink-

absorbency of the ink-absorbency of the ink-receptive layer. Employing a large amount of latex provides the poor ink-absorbency, but the coating of

the ink-receptive layer with so much latex as not to deteriorate the ink-

absorbency is effective in order to improve the surface binding strength and

the water-resistance of the ink-receptive layer.

The above and related objects of the present invention are achieved by

adding a zirconium salt to the coating composition for color recording paper.

The use of zirconium salts improves color printing with non-impact printers

including inkjet printers. The zirconium ions contained within the applied

surface treatment of paper form chemical bonds with reactive sites such as

carboxyl groups on ink pigments and dyes. This bonding action immobilizes

the ink pigments and dyes when the ink is applied to the sheet surface.

According to the present invention, a color recording paper with the coating

composition make the ink held more closely to the surface through the

immobilization of the ink carrier; and therefore, ink migration which causes

bleeding or feathering is reduced by immobilizing the ink dyes and pigments

and not allowing resolubilization of the coating.

Examples of the zirconium salts include ammonium zirconium

carbonate (AZC), ammonium zirconium sulfate, zirconium nitrate,

zirconium acetate, potassium zirconium carbonate. The amount used in the coating composition is from 0.01 to 15 % by weight based on the dry weight

of the total composition. The preferred amount is from 0.05 to 10 % by

weight based on the dry weight of the total composition.

The base layer of this invention can comprise a cationic polymer,

pulp, filler, internal size, a sizing agent, retention aid, and other auxiliary

agents. Retention aids are defined in the "Pulp & Paper Dictionary" by J.

Lavigne, 2nd Edition, Pulp and Paper Research Institute of Canada, Pointe

Claire, Canada, as materials, such as vegetable gums, cationic starches,

potato starch, sodium aluminate, colloidal animal glue, acrylamide resin,

etc., added to the papermaking process at the paper machine headbox, fan

pump, or other location close to the wire. They are added in small amounts

for the express puφose of maximizing the retention of fillers by altering

their electrical charge or bonding. The pulp mainly includes plant pulps,

such as wood pulp and linter pulp, and recycled pulp from waste paper;

however, it may include an inorganic fiber such as glass fiber, or synthetic

pulp, for example, if necessary.

Used as the internal sizing agent are acid sizing agents such as

fortified rosin size, petroleum resin size, and emulsion-type rosin size, and

neutral sizing agents used in the paper manufacturing, such as alkylketene

dimer and cationic size. The ketene dimers used in the invention are known per se and have the following general formula:

Wherein R_f and R₂ each individually represents an organic hydrophobic

hydrocarbon group having about 8-40 carbon atoms. Examples of some

suitable hydrophobic hydrocarbon groups include alkyl groups, alkenyl

groups, aralkyl groups, alkaryl groups, and alkyl substituted cycloalkyl

groups. Illustrative of some suitable alkyl groups for R_{ and R₂ having about

8 to about 40 carbon atoms are decyl, undecyl, dodecyl, tridecyl, tetradecyl,

pentadecyl, hexadecyl, heptadecyl, octadecyl, tetracosyl, and pentacosyl

groups.

The preferred alkyl groups contain from about 12 to about 30 carbon

atoms. Some examples of suitable alkenyl groups containing about 8 and 40

carbon atoms include decenyl, tridecenyl, heptadecenyl, octadecnyl,

eicosenyl, and tricosenyl groups. Some suitable aralkyl, alkaryl and alkyl

substituted cycloalkyl groups having at least about 8 carbon atoms include 4-

tert butylphenyl, octylphenyl, nonylphenyl, dodecylphenyl tridecylphenyl, pentadecylphenyl, octadecylphenyl, heneicosylphenyl, nonycyclopropyl,

dodecylcyclobutyl, tridecylcyclopentyl, tetradecylcyclohexyl groups.

It is understood that the alkyl, alkenyl, alkaryl, aralkyl and

alkycycloalkyl groups can contain non-interfering, inert substituents as is

known to persons skilled in the art. Some examples of inert substituents

include ether, carboalkoxy, alkyloxy, ar loxy, aryloxy, arylalkyloxy, keto

(carbonyl) tert amide groups and the like. Some radicals which preferably

should not be to any large degree in the hydrophobic groups R_! and R₂

include hydroxyl groups, amide groups containing amide hydrogen primary

and secondary amino groups, unstable halogens and carboxylic groups and

other acidic groups. Of course, persons skilled in the art can readily

determine which substituents can be employed if it is desired to avoid

undesirable side reactions. Each Ri and R₂ individually is preferably an alkyl

group containing 8 to 30 carbon atoms. Moreover, mixtures of ketene dimers

can be used when desired. The ketene dimers can be prepared by previously

known methods. For instance, the ketene dimers can be obtained by reacting

thionyl chloride and carboxylic acid containing the desired hydrophobic

hydrocarbon group to produce the corresponding acid chloride, and then

dimerizing the acid chloride by hydrogen chloride splitting to produce the

desired ketene dimer. Cationic starch dosage with AKD also is typically above what is

required to retain AKD or ASA per se to enhance the sheet strength prior to

its being dried (wet web strength). For example, 0.4%-0.5% is adequate for

retention, and an additional 0.20% often is added for improved strength. In

the selection of these sizing agents, there should be chosen the agents that

hardly diffuse into the ink-receptive layer from the base layer. In this

respect, if a diffusible one is employed, the ink-receptive layer becomes so

water-repellent that its ink-absorbency deteriorates which is undesirable.

Considering this, such sizing agents having a strong affinity with pulp and a

high molecular weight is suitable for this aim; in this sense, styrene-acrylic

cationic resin is desirable for this invention.

The coating composition used for the present invention further

contains a binder. Those water soluble hydroxylated polymers are suitable

for the puφose. Examples for the binder include starches and gums. An

ethylated corn starch is preferred for the present invention. The amount used

in the coating composition is from 25 to 48 % by weight based on the dry

weight of the total composition. The preferred amount is from 30 to 45% by

weight based on the dry weight of the total composition.

A synthetic water soluble polymer such as a salt of a styrene maleic anhydride inteφolymer (SMA) can be used in combination with a starch.

The amount used in the coating composition is from 0.05 to 0.5 % by

weight based on the dry weight of the total composition. The preferred

amount is from 0.1 to 0.3 % by weight based on the dry weight of the total

composition. Other water-soluble resins that can be used in this invention

are cationic starch, polyvinylalcohol, gelatin, sodium alginate,

hydroxyethylcellulose, carboxymethylcellulose, polyacrylamide, polystyrene

sulfonate, polyacrylate, polydimethyldiallylammonium chloride,

polyvinylbenzyltrimethylammonium chloride, polyvinylpyridine,

polyvinylpyrrolidone, polyethyleneoxide, hydrolysis product of starch-

acrylonitrile graftpolymer, polyethyleneimine, polyalkylene-

polyaminedicyandiamideammonium condensate, polyvinylpyridinium

halide, poly-(meth)acrylalkyl quaternary salts, ρoly-(meth)acrylamidealkyl

quaternary salts and the like. Among these, cationic starch, whose aqueous

solution shows low viscosity, polyacrylamide,

polydimethyldiallylammonium chloride, and polyvinylpyrrolidone are

particularly desirable for this invention. Among the retention aid to be used

in this invention are vegetable gum, cationic starches, potato starches,

sodium aluminate, colloidal animal glue, acrylamide resin, aluminum

sulfate, styrene-acrylic resin, polyethylene-imine, modified polyethylene- imine, polyethylene-imine quaternary salt, carboxylated polyacrylamide

partially aminated polyacrylamide, acid addition compounds of partially

aminomethylated polyacrylamide, acid addition compounds of partially

methylolated polyacrylamide, epichlorohydrin resin, polyamide

epichlorohydrin resin, formalin resin, modified polyacrylamide resin and the

like.

When manufacturing the paper coatings of the present invention, the

cationic polymer is typically present in an amount of 0.2 to 0.5 % by weight

based on the total dry weight of the coating composition.

The coating composition may contain other pigments, such as calcium

carbonate, titanium dioxide, silica and talc. The amount used can be up to 70

% by weight based on the dry weight of the total composition. Other fillers

and pigments which can used in this invention include clay, activated clay,

aluminum hydroxide, diatomaceous earth, barium sulfate, organic resinous

pigment, and the like, all of which are commonly used in the paper-

manufacturing or paper-converting factories. These are produced in many

different grades, but this invention does not limit the use of any of them.

Moreover, if necessary, a mixture of plurality of different fillers or a mixture

of same filler of different grades can be used. In order to increase the opacity

of the base layer, such fillers as titanium oxide and calcium carbonate that have high refractive index and can be atomized easily are preferable, and, in

view of the availability and the economy, finely powdered precipitated

calcium carbonate is the most preferable of all.

The surface coating composition used in the present invention also

contains an alkenyl succinic acid neutral paper-manufacturing material, such

as alkyl ketene dimer (AKD) and/or an alkenyl succinic anhydride (ASA).

The AKD is as defined above. The substituted succinic anhydride useful for

this invention is a hydrophobic molecule. Usually it will have one

substituent in the 3-position but it may have substituents in both the 3- and

4-positions. In general, the substituent will be an alkyl, alkenyl or aralkyl

group. Other elements may be present in a minor amount, such as a sulfur or

ether linkage. The total number of carbon atoms in the substituent is between

6 and 50. A preferred substituent size is between 10 and 30 carbon atoms.

More preferred is between 12 and 25 carbon atoms. A preferred embodiment

of the contemplated anhydrides is the alkenyl succinic anhydride made by

allowing an oiefin to react with maleic anhydride. For present puφoses, We

shall refer to the anhydrides contemplated as "ASA". Such materials are

exemplified by the maleic anhydride copolymers with n-pentadecene-2; n-

pentadecene-3; n-pentadecene-6; n-hexadecene-4; n-hexadecene-5; n-

hexadecene-8; n-heptadecene-3; n-heptadecene-5; n-heρtadecene-7; n- octadecene-3; n-octadecene-4; n-octadecene-9; n-nonadecene-2; n-

nonadecene-7; n-eicosene-4; n-eicosene- 10; n-heneicosene-3 ; n-

heneicosene-9; n-tetracosene-2; n-tetracosene-5 and n-tetracosene- 11. Other

surface sizing agents include, for example, acid sizing agents such as

fortified rosin size, petroleum resin size, emulsion-type rosin size, cationic

resin sizing agent; anionic or cationic acrylamides; and the like. These

surface sizing agents can be applied with water-soluble resins, such as

starch, polyvinyl alcohol, etc. The viscosity of the coating material is

controlled to 5-2000 C. P., in order to prevent an extreme penetration into a

base layer. The addition amount of the materials and the coating amount

thereof are controlled so that the whole recording sheet has a Stockigt sizing

degree of 3 seconds and over, wherein they are easily determined by

experiments.

Coating compositions suitable for coating the paper substrate of the

present invention are described in OS 5,472,485 as mentioned above.

Accordingly, the entire contents of US Patent No.5,472,485 are incoφorated

by reference herein.

In order that the present invention may be more clearly understood, reference will now be made to the following examples; however, the

examples are only to illustrate this invention and not to be construed to limit

this invention. The following examples are given to illustrate the invention

without any limitation to the scope of the invention. Examples 4 and 5

illustrates how to make multiple puφose paper sheet. Examples 6 and 7

show how to make custom ink jet sheets. Unless otherwise indicated, the

parts mentioned in the examples are on dry weight basis.

The following Examples illustrate how to make ASA and AKD

containing compositions and other compositions useful in the present

invention as shown in our U.S. Patent 5,472,485.

EXAMPLE 1

An emulsion of AKD was prepared as follows:

200 gallons (1,668 pounds) of water

166.8 pounds of AKD wax

333.6 pounds (dry basis) oxidized cationic potato starch

20 pounds ("as received") of AZCote₅₈o_0m Ammonium zirconium Carbonate

(6% based upon the weight of the Starch)

The ingredients were mixed and homogenized to form an emulsion. Another emulsion was prepared in the same manner as above, but the AZC

was omitted.

The resulting emulsions were applied at 0.15% of paper furnish or 3.0

pounds per ton (2000 pounds) of paper furnish in a 144 lbs/3000 ft.² sheet. A

quaternary cationic potato starch was used at 6.7 dry pounds/ton of fiber to

retain the AKD in the sheet. The resulting paper sheet samples were tested

for comparative H₂0₂ absoφtion using the above described Test Method.

EXAMPLE 2

An emulsion of ASA was prepared as follows:

200 gallons (1,668 pounds) of water

66.0 pounds of cationic potato starch

4.6 pounds of AZCote₅8ooM Ammonium Zirconium Carbonate

220.0 pounds of ASA

The ingredients were mixed and homogenized to form an emulsion.

EXAMPLE 3

A surface sizing compound was prepared by adding AZC

(AZCote₅₈oo_m), containing about 12 to about 18 percent zirconium as calculated as Zr0₂, to a 7 percent solution of a low molecular weight starch,

which had been converted using ammonium persulfate. Paper was sized,

dried and cured and the paper was tested (starch+AZC). Next, 4.5 percent

(dry basis on starch solids) sodium salt of SMA was added to the surface

sizing compound and paper was sized, dried and cured, and the paper was

tested (Starch+NH₄ SMA). AZC was next added at 4 percent "as received"

level, based on the dry content of starch and SMA, to the surface sizing

compound; paper was then sized, dried and cured and the paper was tested

(Starch+NH₄ SMA+AZC).

EXAMPLE 4

A test was conducted in a paper mill producing 10 and 80

grams/meter 2 (gsm) paper, respectively. The 80 gsm sheet is used for ink jet

and offset printing. The 70 gsm sheet is used for photocopy applications.

Both sheets use alkyl ketene dimer (AKD) for internal sizing, and both

sheets contained calcium carbonate ash. Oxidized starch is applied at the

size press. The 70 gsm sheet has a more "open", absorbent surface due to

less refining of the fiber, and a lower dosage of AKD (1.2 pounds/ton ). The

80 gsm sheet has a more "closed" surface, with a higher dosage of AKD (3

ponds/ton). Attempts were made to improve ink jet printability of the 80 gsm sheet by

using high levels of internal size in combination with a significant level of

synthetic surface size ( styrene/acrylic), and 5 % pigment in the surface size.

These attempts had been partly successful. Color printing on a Hewlett

Packard 340 DeskJet ink jet printer and an Epson ink jet printer produced

sheets with good color density and minimum bleeding. However, the ink set

off (drying) time was in excess of 2 minutes. The long set off time rendered

the sheet unsuitable for other types of applications, and smearing of the

drying ink during contact with surfaces reduced the effectiveness in the

intended application.

According to the present invention, the following differences are

made for 80 gsm paper:

1. AKD was reduced to 2 pounds/ton;

2. Pigment was removed from the surface size due to production

related considerations;

3. Ammonium zirconium carbonate was applied at 6 % "as received"

based upon starch; and

4. Sodium salt of styrene maleic anhydride (SMA) was added to the surface size at 2 pounds/ton on dry basis.

The surface size was applied with a gate roll size press. Sheets were

printed with the above-mentioned Hewlett Packard and Epson ink jet

printers, using Hewlett Packard Test Patterns. The color density was equal

to, and bleeding superior to, sheets previously made with heavy internal

sizing and pigment in the size press. However, the ink set off time was less

than 15 seconds, rendering the sheet suitable for other applications

including offset printing.

In subsequent tests, the previously described 70 gsm sheet is used for

xerographic applications. Pigment was added to the surface size due to the

"openness" of the sheet. The action of the invention resulted in good ink jet

printing characteristics as defined by color density, bleeding, and ink set off

time. The present invention thus allows all paper grades to be produced from

the 70 gsm sheet, with changes being made only in the surface size. The

significantly improves the production efficiency of this operation.

EXAMPLE 5

A paper mill produced a 75 gsm sheet, sized with alkyl succinic anhydride, with a low cost corn starch modified on site with ammonium

persulfate. The sheet was tested for improvement of color inkjet printing by

using a Hewlett Packard 500 series printer. The standard paper sheet, using

6 % "as received" ammonium zirconium carbonate and 2 pounds/ton dry

sodium salt SMA, printed well on single color black ink. Offset printing

was good, and xerographic performance was acceptable. Color ink jet

printing resulted in unacceptable bleeding. Increasing the level of

ammonium carbonate to 8% to 10% achieved acceptable color inkjet

printing (including color density, bleeding, ink set off time), using Hewlett

Packard #3 and #4 Criteria Test Patterns. Offset printability and xerographic

performance remained acceptable.

PROCEDURE FOREXAMPLES 6 AND 7

When making down the formulations in Examples 6 & 7 the viscosity

of the formulation will increase dramatically unless the materials are added

in a specific order. Also, there will be a dramatic viscosity increase when

using the high amounts of ammonium zirconium carbonate, unless an equal

amount of water is added with the ammonium zirconium carbonate while

mixing. The proper order of addition is as follows:

Calcium Carbonate Starch

SMA

Cationic Polymer

AZC

EXAMPLE 6

The present invention was tested in a pig nented surface size applied

via laboratory size press and draw downs, in a development program to

produce a high quality sheet capable of near premium quality images when

printed with a Hewlett Packard 820 color ink jet printer. The object of the

program was to produce a sheet with near premium ink jet grade quality

using standard surface sizing and coating additives for surface treatment to

the base paper sheet. A surface size applied to the sheet was prepared using

the following formulation:

100 parts Calcium Carbonate

50 parts ethylated starch

5 dry parts of AZC

0.5 dry parts sodium salt SMA

(Binder and additives are based on dry pigment)

The color density of the paper approached premium i jet quality, with minimum bleeding. The color densities and bleed was improved by

using the above formulation with the AZC and SMA over the formulation

without the AZC or SMA.

EXAMPLE 7

The relatively high dosage of ammonium zirconium carbonate used in

Example 6 resulted in a very high cost for the formula. As a result, another

experiment was conducted using a 50% solid cationic polyquantenary amine

polymer (HTI 9082) designed to react with the dye pigments to improve

color density and bleed. The theory being that the cationic charge of the

polymer would react with the cationic charge of the ink pigment to keep the

ink close to the surface and prevent bleeding by fixing the ink to the surface.

The objective of the experiment was to allow for a reduced dosage of AZC

in order to lower the cost of the formulation. The formula as used contained:

100 Parts Calcium Carbonate

50 parts ethylated corn starch

0.25 dry parts sodium salt SMA

0.50 dry parts cationic polymer

2.5 dry parts ammonium zirconium carbonate The immobilizing action of ammonium zirconium carbonate in the

surface treatment, combined wit the fast drying effect of the cationic

polymer, produced a sheet with high quality ink jet printability as measured

by color density, bleeding and ink dry time. Through crosslinking the

coating components, ammonium zirconium carbonate imparted sufficient

resistance against rewetting from the high water content of the ink jet inks,

and with the help of the cationic polymer the ink was immobilized giving

improved color density and bleed

It will be apparent from the foregoing that many other variations and

modifications may be made regarding the inkjet papers described herein,

without departing substantially from the essential features and concepts of

the present invention. Accordingly, it should be clearly understood that the

forms of the inventions described herein are exemplary only and are not

intended as limitations on the scope of the present invention as defined in the

appended claims.

Claims

We claim:

1. A color recording paper for non-impact printers comprised of a

paper substrate coated with a coating composition which comprises a

zirconium salt in an effective amount to improve color printing quality and

prevent ink bleeding during the printing process.

2. A color recording paper for non-impact printers according to Claim

1; wherein the zirconium salt is selected from the group consisting of

ammonium zirconium carbonate and potassium zirconium carbonate.

3. A color recording paper for non-impact printers according to Claim

2, wherein the zirconium salt is ammonium zirconium carbonate in amount

of 0.01 to 10 % by weight based on the total dry weight of the coating

composition.

4. A color recording paper for non-impact printers according to Claim

1, wherein the coating composition further comprises calcium carbonate in

amount of 50 to 70 % by weight based on the total dry weight of the coating

composition.

5. A color recording paper for non-impact printers according to Claim

1, wherein the coating composition further comprises a binder in amount of

25 to 40 % by weight based on the total dry weight of the coating

composition.

6. A color recording paper for non-impact printers according to Claim

1 , wherein the binder is starch.

7. A color recording paper for non-impact printers according to Claim

1, wherein the coating composition further comprises sodium salt of styrene

maleic anhydride in amount of 0.1 to 0.3 % by weight based on the total dry

weight of the coating composition.

8. A color recording paper for non-impact printers according to Claim

1, wherein the coating composition further comprises a cationic polymer in

amount of 0.2 to 0.5 % by weight based on the total dry weight of the

coating composition.

9. A color recording paper for non-impact printers according to Claim

1, wherein the coating composition comprises, based on the total dry weight of the coating composition, 1.5 to 3.5 % ammonium zirconium carbonate,

60 to 65 % calcium carbonate, 30 to 35% starch and 0.15 to 0.2 % sodium

salt of styrene maleic anhydride.

10. A color recording paper for non-impact printers according to

Claim 9, wherein the coating composition further contains 0.3 to 0.35 % a

cationic polymer.

11. A color recording paper for non-impact printers according to

Claim 1, wherein the coating composition further comprises, based on the

total dry weight of the coating composition, to % of alkyl ketene dimer.

12. A color recording paper for non-impact printers according to

Claim 1, wherein the non-impact printers are inkjet printers.

13. A method for improving the color printing quality and preventing

ink bleeding in a paper for non-impact printers, which comprises coating

said ink jet paper with a composition containing a zirconium salt in an

effective amount to improve color printing quality and prevent ink bleeding

during the printing process.