JPS61273985A - Coating composition for pressure-sensitive copy paper - Google Patents

Abstract

PURPOSE:To obtain pressure-sensitive copy paper excellent in coating property, storage stability, color developability and color forming fog resistance, by using copolymer latex, which is obtained by polymerizing a monomer composition containing specific monomer components in a specific ratio, as a binder. CONSTITUTION:As a binder component, copolymer latex, which is obtained by copolymerizing 2-30wt% (based on monomer components) of aliphatic conjugated diene, 5-70wt% of ethylenic unsaturated carboxylic ester and 10-90wt% of other ethylenic unsaturated compound, is contained. The glass transition temp. of the copolymer constituting the copolymer latex is pref. -50-30 deg.C and the toluene insolubles of the copolymer are pref. 30wt% or more. The use amount of the copolymer latex is 3-50pts. by wt. of 100pts. of a microcapsule on the basis of the compolymer component. The content of an emulsifier in the copolymer latex is 1% or less by wt. of the copolymer component.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a coating composition for pressure-sensitive copying paper that is improved particularly in terms of color development and color fog.

[Conventional technology]

Pressure-sensitive copying paper called carbonless copying paper includes, for example, a color former layer containing microcapsules containing a color former (hereinafter referred to as "color former microcapsules") and a color developer containing a color developer. A type in which a layer is formed respectively on the back and front side of two stacked supports (usually paper), or a type in which a color former microcapsule and a color developer are mixed or mixed on the surface of a lower support. There are known types in which a recording layer is formed by laminating layers. The pressure sensitive
In the case of copy paper, mechanical or impact pressure is applied to the surface of the upper support by writing instruments, typewriters, other types of mechanical printers, printers, etc. This destroys the microcapsules that contain the coloring agent, and the coloring agent inside the capsules is destroyed.
When the agent is exposed and comes into contact with the color developer, color development, photocopying, and recording are achieved.

, \・4λ,, -i, coating 5 for forming the above-mentioned coloring agent layer;, :yu &l*#4
! 'Q@tf'I? 49 o”7′)b゛(11[j
It consists of PJ (X Patilt), a binder and other additives. The protective agent is a color former.
+z, ailti:ac yoa, :(7)? -1゜′,′ :゛ Has a function to prevent damage caused by direct exposure to unexpected external forces applied when the capsule is not intended for copying/recording. However, it is usually composed of microparticles of organic or inorganic substances with a particle size slightly larger than that of the color former. In addition, the binder has the function of binding and fixing the coloring agent microcapsules, the protective agent, and other additives to the support. Conventionally, such binders include polyvinyl alcohol, starch, modified starch, Water-soluble polymer compounds such as carboxymethyl cellulose and casein are often used.

However, coating compositions using water-soluble polymer compounds as described above as binders have the following problems.

■ Pressure-sensitive copying paper tends to cause so-called color fog.

Color fog occurs when the color former microcapsules are destroyed by mechanical pressure, frictional force, or heat applied during handling of pressure-sensitive copying paper other than when used for copying and recording purposes, such as during manufacturing or storage. , which is a phenomenon in which color develops unnecessarily. For coating compositions using water-soluble polymer compounds as binders □.

One of the reasons why such colored fog tends to occur is that the dried paint film formed from water-soluble polymeric substances is generally strong but lacks elasticity, and as a result, external forces applied to the paint film are It is thought that this is because the color former is not absorbed but is directly transmitted to the color former microcapsules and acts on them.

■ Poor shelf life.

Water-soluble polymer compounds are easily putrefied and are difficult to clean.
□ゎWork, □Yuma ゎE7□Quality. 4. It is difficult to preserve it at 1゜゛.

,,,　　　　　　　　■　Poor coatability.

- Binders using water-soluble polymer compounds have high viscosity and properties, making it difficult to perform coating operations efficiently and smoothly. Reduce the solid content percentage in □゛
This will cause inconvenience.

1 Natsume・＼、・ This will solve the problem of color fogging in ① above;).

:,・ From this point of view, it is effective to increase the content ratio of the protective agent, but if you do this, it will be difficult to copy.
The color former capsules are less likely to be destroyed by external forces such as writing pressure and printing pressure applied to the color former layer during recording, resulting in a problem in which the color density of the pressure-sensitive copying paper is reduced.

The aim is to solve these problems,
A coating composition for pressure copying paper using an acrylic acid ester polymer Latinx instead of a water-soluble polymerized metal material (Japanese Patent Laid-Open No. 72891/1989)
and those using latex (Japanese Unexamined Patent Publication No. 57-7758
9) has been proposed. Since these coating compositions use latex as a binder, sufficient improvements were seen in the storage stability (2) and the coating properties (2) above, but they are still sufficiently satisfactory in terms of color fog (2) above. The desired results have not been obtained.

II! 11"'N'r L -1-6t t 4 fo
t+5JIN,) (''The present invention is
Comprehensively solves the problems of conventional technology in terms of color fog, storage stability, and workability, and in particular, sufficiently prevents color fog from occurring due to unnecessary destruction of color former microcapsules while maintaining excellent color performance. It is an object of the present invention to provide a coating composition for pressure-sensitive copying paper that can form a pressure-sensitive copying paper with a high quality coating.

[Means for solving problems]

The above-mentioned problem is solved in the coating composition for pressure-sensitive copying paper containing microcapsules encapsulating a coloring agent and a binder.
As the binder component, the following monomer component ・'(8) Aliphatic conjugated diene 2
~30% by weight □ Mountain) Ethylenically unsaturated carboxylic acid ester'
5-70% by weight (C1(b
The problem is solved by a coating composition for pressure-sensitive copying paper, which contains a copolymer latex obtained by copolymerizing 10 to 93% by weight of an ethylenically unsaturated compound other than 1.

That is, the coating composition for pressure-sensitive copying paper of the present invention is a copolymer obtained by polymerizing a monomer composition containing an aliphatic conjugated diene and an ethylenically unsaturated carboxylic acid ester in a specific proportion. Add coloring agent Mami Microcapsules, protective agent, and other materials as necessary to the binder containing polymer latex.
It is composed of dispersed additives.

−ゝ゛・ Hereinafter, the present invention will be explained in detail.

, ), −.

For use in the production of copolymer latex in the present invention. Examples of aliphatic conjugated dienes that can be present include butadiene, isoprene, 2-
Examples include chloro-1,3-butadiene, and butadiene is particularly preferred.The amount of aliphatic conjugated diene used is 2 to 30% by weight, preferably 5 to 20% by weight based on the entire monomer component. . If the amount used is less than 2% by weight, the color development in the pressure-sensitive copying paper will be insufficient, and if the amount used exceeds 30% by weight, coloring fog will occur due to friction or heating in the pressure-sensitive copying paper. Both are undesirable.

Examples of ethylenically unsaturated carboxylic acid esters that can be used in the production of the copolymer latex of the present invention include methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, and acrylic acid.
2-ethylhexyl, hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, methacrylic acid-
Examples include 2-ethylhexyl and hydroxyethyl methacrylate, with butyl acrylate, 2-ethylhexyl acrylate, butyl methacrylate, and 2-ethylhexyl methacrylate being particularly preferred.

The amount of ethylenically unsaturated carboxylic acid ester used is 5 to 70% by weight, preferably 10 to 6% by weight based on the total monomer components.
It is 0% by weight. If this usage amount is less than 5% by weight,
Color fogging due to heating tends to occur, while if the amount used exceeds 70% by weight, color fogging due to pressure or friction tends to occur, both of which are unfavorable.

Examples of ethylenically unsaturated compounds other than ethylenically unsaturated carboxylic acid esters that can be used in the synthesis of the copolymer latex of the present invention include monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, and methacrotonic acid; acids, unsaturated carboxylic acids such as dicarboxylic acids such as maleic acid and fumaric acid and anhydrides of these dicarboxylic acids, aromatic vinyls such as styrene, α-methylstyrene and vinyltoluene, acrylamide, methacrylamide, N-methylolacrylamide, etc. Examples include alkylamides of unsaturated carboxylic acids, vinyl cyanides such as acrylonitrile, and vinyl acetate, and these may be used alone or in combination of two or more.

The glass transition temperature of the copolymer constituting the copolymer latex in the present invention is preferably -50°C to 30°C, more preferably -40°C to 25°C. If the glass transition temperature is lower than 150° C., the elasticity of the binder tends to become excessive, resulting in a decrease in the color development of the pressure-sensitive copying paper, which is undesirable. On the other hand, if the glass transition temperature exceeds 30° C., color fogging due to heating tends to occur, which is not preferable.

The toluene insoluble content of the copolymer constituting the copolymer latex in the present invention is preferably 30% by weight or more, particularly preferably 40 to 100% by weight.

If the toluene-insoluble content is less than 30% by weight, the color development of the pressure-sensitive copying paper tends to decrease, which is not preferable.

The toluene-insoluble content here refers to copolymer latex that is adjusted to pH 6 to 8 with sodium hydroxide, coagulated with methanol, and then washed and dried.
0.3g of the coagulated material obtained was collected as a sample,
□ Calculate the ratio of insoluble matter to the total sample obtained when this sample was immersed in 1001 toluene for 20 hours.

゛.

゛ The amount of copolymer latex used in the present invention is preferably 3 to 50 parts by weight, more preferably 6 parts by weight, based on 100 parts by weight of microcapsules in terms of copolymer components.
Preferably, it is 5 to 40 parts by weight. If the amount of copolymer latex used is less than 3 parts by weight, the adhesive strength of the coating composition will be insufficient;
, ゛, the microcapsules in the coating layer become thickly covered with the copolymer component, and as a result, the coloring properties of the pressure-sensitive copying paper deteriorate.

, 1 The copolymer latex in the present invention is of an emulsion type, and is used to emulsify and disperse monomers or to stably disperse copolymer particles produced after emulsion polymerization.

1. Contains an emulsifier used for IR. This is 1 unit (such emulsifiers include anionic surfactants, positive and
) Near; 〉 ] Ionic surfactant, nonionic surfactant, both 11. ] Pa, ゛ Raw surfactants, etc. are used alone or in combination of two or more types. Preferred emulsifiers are anionic surfactants, such as sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium laurylnaphthalenesulfonate, sodium dialkylsulfosuccinate, etc., which can be used alone or in combination of two or more.

The content of the emulsifier in the copolymer latex is preferably at most 1% by weight, particularly preferably at most 0.5% by weight, based on the copolymer components. Emulsifier content is 1% by weight
If it exceeds 100%, the coloring properties of pressure-sensitive copying paper tend to decrease, which is not preferable. In particular, when gelatin microcapsules synthesized by the coacervation method are used as color former microcapsules, the color former inside the capsules may be extracted by the surfactant because the gelatin film has low resistance to surfactants. It is preferable that the amount of the emulsifier added is 0.4% by weight or less since coloring capri tends to occur.

The copolymer latex in the present invention preferably has the above-mentioned glass transition temperature, toluene-insoluble content, and N
and emulsifier content.

More preferably, it includes two conditions, and still more preferably, it includes three conditions.

The color former microcapsules in the present invention can be produced by, for example, the coacervation method specifically described below, t'
.

, □゛ Interfacial polymerization method, In 5itu
"Ding,""i," by various methods such as polymerization method
-y 7 ′i′′8 h !
6 (7) “JflkN4.:, & “”.

■Coacervation method: This method is disclosed in, for example, U.S. Patent Nos. 2,800,457 and 2,800,458.
□□ As shown above, an oily liquid in which a coloring agent has been dissolved is emulsified and dispersed in the form of minute oil droplets in an aqueous solution of a hydrophilic polymer such as gelatin or gum arabic, and the above is applied to the surface of these minute oil droplets. The hydrophilic polymer colloid undergoes phase separation (coacervate) and is cured to form a wall film.
This is to obtain black capsules.

: ■Interfacial method Mi1 This method is described, for example, in Japanese Patent Publication No. 44-27257, Japanese Patent Publication No. 42-771, Japanese Patent Publication No. 4
As disclosed in Publication No. 6-18127 and Publication No. 50-72507, two types of substances that react with each other to form an insoluble film at the interface of a hydrophilic liquid and a hydrophobic liquid are mixed into a hydrophilic liquid and a hydrophobic liquid, respectively. and by dissolving it in a hydrophobic liquid and causing an interfacial reaction, for example, a polyamide capsule",J,'++Id*""?C17"ゞ/L41
1J(7).

■In-5-itu polymerization method This method, as disclosed in Japanese Patent Publication No. 44-3495, uses a core material (oil droplets containing a coloring agent) and a reactant, that is, monomers and prepolymers necessary to form a polymer. Alternatively, polymerization may be carried out in a dispersion system in which reaction system components such as catalysts coexist, thereby forming a voluminous substance that is insoluble in the particles of the core material and the dispersion medium at the interface between the particles of the core material and the dispersion medium. Microcapsules are obtained by forming a polymer shell on the particle surface. According to this method, the capsule wall membrane is melamine-
Microcapsules made of formalin resin, urea-formalin resin, etc. can be obtained.

By using wall membranes such as melamine-formalin resin and urea-formalin resin using the In 5 intu method,
The microcapsules are heat resistant, solvent resistant, and water resistant. The coloring agent of the present invention has excellent properties in terms of properties and chemical resistance, and the microcapsules can be stably produced by a simple process.
It can be advantageously used as a black capsule.

- A color former that constitutes the color former microcapsule.

1, :':'□,' (for example, 1,) □・S 8. Crystal violet lactone, penzoyluro'4 0゛ Icomethylene blue, fluorans, Spiαpira, V ,・ Puff.

You can use the following.

□ In addition, as a color developer that develops color by contacting this color former, for example, inorganic color developers such as acid clay, activated mortar, and earth, organic color developers such as phenolic resin, and salicylic acid derivative salts. 5. Use a color developer. I can do it.

The protective agent used in the present invention may be one that is commonly used, such as powders of organic substances such as starch and cellulose, or powders of inorganic substances.
The amount used is generally 20 to 80 parts by weight per 100 parts by weight of color former microcapsules.

In the kettle invention, various additives such as an antifoaming agent and a waterproofing agent can be further included as necessary. In addition to the copolymer latex used in the present invention, as a binder, water-soluble polymers such as water-soluble modified starch, polyvinyl alcohol, hydroxyethyl cellulose, etc. may be used in combination as necessary to supplement adhesive strength. can.

The coating composition of the present invention is prepared by mixing the above-mentioned various materials, and the solid content concentration in the coating composition is generally 15 to 50.
% by weight. This coating composition can be applied to blade coaters, air knife coaters, and
A preferred coating amount of the coating composition of the present invention is determined per unit of base paper by coating the base paper with an on-machine coater (equipped with a coating device such as a bar coater, roll coater, size press coater, etc.) to make pressure-sensitive copying paper. As the base paper, which has a density of 2 to 5 g/nl per area, high-quality base paper, medium-quality base paper, etc. obtained by acidic or alkaline paper making can be used.

〔Example〕

Examples of the present invention will be described below, but the present invention is not limited thereto. In the following description, "parts" and "%" refer to parts by weight and % by weight, respectively.
shows.

,, Examples 1 to 7. Comparative example 1~
4. (1) Production of copolymer latex A-J 1,9
<Copolymer latex A> Water 160
parts, 0.3 parts of sodium alkylbenzenesulfonate,
0.6 parts of sodium bicarbonate and 0.6 parts of potassium persulfate.
5 parts were charged into a 1001 volume autoclave. Next, a monomer composition consisting of 15 parts of butadiene, 62 parts of styrene, 20 parts of butyl acrylate, 1 part of acrylic acid, and 2 parts of fumaric acid was added at once along with 2 parts of carbon tetrachloride, and the mixture was heated to 70°C while stirring. did. When polymerization was continued in this state for 20 hours, the polymerization conversion rate reached 100%. The copolymer latex obtained in this way had a good polymerization mode and little generation of coagulum. A sodium hydroxide solution was added to this copolymer latex to adjust the pH to 9, and then the latex was concentrated by monomer stripping and vacuum distillation. The obtained copolymer latex is referred to as "Latex A".

Copolymer Latex B-J> Nine types of copolymer latexes were obtained by the same procedure as Copolymer Latex A using the monomer components shown in Table 1. These copolymer latexes are called “Latex B-JJ”
shall be.

Note that latex G-J is a latex for comparison; latex G does not contain an aliphatic conjugated diene ((al'), and latex H contains an aliphatic conjugated diene ((al)).
If the proportion of .
This is an example of a case where the ratio of bl ) is excessive.

The glass transition temperature (Tg) and toluene insoluble content of the above latex A-J are also listed in Table 1.

(2) Synthesis of color former microcapsules 3.5 parts of crystal violet lactone per 100 parts of organic solvent rsAs296J (manufactured by Megaga).
The dissolved color former solution was mixed with styrene-maleic anhydride/acid copolymer 4.
was added to an aqueous solution containing 100% of the total amount of 100% of the total amount of 100% of the product.

,＼ Next, the initial stage of melamine-formalin with a solid content of 15%,
Ill r S R613J
(Sumitomo Chemical [[manufactured by 1] O water tljH5'7...'70' after adding 60 parts)
The mixture was heated to C and allowed to react for 3 hours. Next, this reaction product solution was adjusted to pH 9.0.

111, A dispersion of colorant microcapsules was created. This ＼ is 9p) The average particle size of the microcapsules is 4. It was .5 μm.

, □・, '::) (3> Preparation of coating composition J) Using the copolymer latex obtained as above, t~ 1 and color former microcapsules, the ゛ grouping shown in Table 2 was carried out. The following materials were mixed to prepare 7 types of coating materials with a solid content ratio of 35% and 4 types of □ ゛, L., and Comparative Examples.

1. (4) Characteristic test Each of the coating compositions obtained in (3) above was applied to base paper using a rondo so that the coating amount was 3.0 g/rrl, and the upper paper for pressure-sensitive copying paper was coated. I got it. These top paper and commercially available bottom paper 1''ccpJ (manufactured by Jujo Paper Industries, Ltd.) were overlapped to form samples of pressure-sensitive copying paper, and the following four items were tested.

(2) Color development Each sample was printed using a typewriter, and 30 minutes later, the color density of the lower paper was measured using a Hunter colorimeter to determine the degree of whiteness (%), and the color development was evaluated based on this. The smaller the whiteness value, the better the color development.

■Pressure resistance (occurrence of color fog due to pressure a) After pressurizing each sample at a pressure of 50-/- for 5 minutes,
The whiteness of the bottom paper was measured using a Hunter colorimeter. The higher the whiteness value, the less color fog will occur;
Pressure resistance is good.

■Abrasion resistance (state of color fogging caused by friction B) Place the bottom paper of each sample on top, place a weight of 3 kg on top of it, slide it over a certain distance (30C1l), and then place the bottom paper on top. The whiteness of the sample was measured using a Hunter colorimeter. The larger the whiteness value, the less color fog occurs and the better the abrasion resistance.

■Heat resistance After heating each sample in an open oven set to 120℃ for 3 hours, the whiteness of the bottom paper was
It was measured by an internal colorimeter. The larger the whiteness value, the less color fog occurs and the better the heat resistance.

The results of the above characteristic tests are shown in Table 2.

, ゛, I couldn't get good results over time. That is, in Comparative Example 1, no aliphatic conjugated diene was included as a monomer component used in the production of the copolymer latex, and the color development was insufficient. In Comparative Example 2, the amount of aliphatic conjugated diene is excessive, and color fogging is likely to occur due to friction or heating. In Comparative Example 3, the amount of ethylenically unsaturated carboxylic acid ester is too small, and color fogging is likely to occur due to heating. In Comparative Example 4, the amount of ethylenically unsaturated carboxylic ester is excessive, and color fogging is likely to occur due to pressure or friction.

〔Effect of the invention〕

The coating composition for pressure-sensitive copying paper of the present invention uses a copolymer latex obtained by polymerizing a monomer composition containing specific monomer components in a specific ratio as a binder, and has the following effects. have an effect.

(1) Excellent coating properties.

The coating composition of the present invention uses a copolymer latex as a binder and does not require the use of a water-soluble polymer compound with high viscosity, or even if it is used, only a small amount thereof is used. Construction work can be carried out smoothly.

In addition, for the same reason, the solid content concentration of the coating composition can be increased while maintaining good coating properties.
This is advantageous in terms of coating productivity.

(2) Excellent storage stability.

The coating composition of the present invention uses a copolymer latex as a binder, and does not require the use of perishable water-soluble polymer compounds, or even if it is used, only a small amount is used, so it has good shelf life and long-lasting properties. There will be no deterioration in quality due to overtime.

(3) Pressure-sensitive copying paper excellent in color development and color fog can be obtained.

Since the coating composition of the present invention uses a copolymer latex as a binder, it can impart appropriate elasticity to the coating film (color former layer), and as a result, it has an effect on pressure-sensitive copying paper even when not in use. It can sufficiently absorb external forces such as relatively small pressing force, frictional force, thermal stress, etc. that are inevitably or accidentally applied during manufacturing, storage, etc., and the force that acts on the color former capsule. Since the coloring function can be weakened, it is possible to effectively prevent coloring fog from occurring without impeding the coloring function during use.

Claims (1)

[Scope of Claims] 1) A coating composition for pressure-sensitive copying paper containing microcapsules encapsulating a coloring agent and a binder, wherein the binder component includes the following monomer components (a) aliphatic conjugated diene 2 ~30% by weight (b) Ethylenically unsaturated carboxylic acid ester 5~70
Weight% (c) Ethylenically unsaturated compounds other than (b) 10-9
A coating composition for pressure-sensitive copying paper, characterized in that it contains a copolymer latex obtained by copolymerizing 3% by weight of a copolymer latex. 2) The coating composition for pressure-sensitive copying paper according to claim 1, wherein the copolymer component in the copolymer latex has a glass transition temperature in the range of -50°C to +30°C. 3) The coating composition for pressure-sensitive copying paper according to claim 1, wherein the toluene-insoluble content of the copolymer component in the copolymer latex is 30% by weight or more. 4) The coating composition for pressure-sensitive copying paper according to claim 1, wherein the amount of emulsifier used in the copolymer latex is 1% by weight or less based on the copolymer components.