JPS6315782A - Coating composition for pressure sensitive paper - Google Patents

Abstract

PURPOSE:To obtain a color reaction paper for a pressure sensitive paper having excellent color forming properties, light resistance and moisture resistance and not hindering printability or workability at all, by using an organic color developer, light calcium carbonate and a specified binder. CONSTITUTION:The title composition comprises an organic color developer, light calcium carbonate and a binder. A copolymeric latex comprising 25-65wt% of an aliphatic conjugated diolefin monomer, 0.2-10wt% of an ethylenic unsaturated carboxylic acid amide monomer and 25-74.8wt% of other monomer copolymerizable with these monomers is used as the binder. The aliphatic conjugated diolefin monomer may be 1,3-butadiene, 2-methyl-1,3- butadiene or the like. The ethylenic unsaturated carboxylic acid amide monomer may be acrylamide, methacrylamide, N-methylolacrylamide or the like. The other monomer being copolymerizable may be styrene, alpha-methylstyrene, vinyltoluene or the like.

Description

Detailed Description of the Invention A1 Object of the Invention [Field of Industrial Application] The present invention relates to a coating composition for pressure-sensitive copying paper,
Ru. More specifically, the present invention provides a coating material for pressure-sensitive copying paper that is excellent in color development, light fastness, and moisture resistance, and also exhibits excellent surface strength and desensitizing ink drying properties. The present invention relates to a composition.

In general, pressure-sensitive copying paper contains clay paper coated on the back with fine capsules containing an electron-donating colorless or light-colored leuco dye dissolved in an organic solvent (capsule oil), and an electron-accepting color developer. It consists of a base paper with a color developing layer on the surface, and these two coated surfaces are overlapped so that they are facing each other, and pressure is applied using a typewriter such as a pen typewriter. capsule was destroyed,
Capsule oil containing leuco dye transfers to the color developing layer and performs a color reaction, resulting in printed records.
It was made by sea urchin.

The coloring paper for pressure-sensitive copying paper expressed in the present invention is a base paper provided with a color developer layer as described above, a color developer layer on the front surface, and a coating layer on the back surface. Including inner paper. Another form is a single recording sheet or a single coloring paper in which both the capsules and color developer are coated on the same side of the substrate.4 Coloring paper for pressure-sensitive copying paper. Inclusion as a form. ,.

In recent years, demand for pressure-sensitive copying paper has shown remarkable growth with the rationalization of office work, the development of the information industry, and the spread of computers, and its uses have also diversified. All four abilities are required. For example, in addition to being able to obtain clear, high-density colored images when copying, the stability of colored images over time, especially sunlight fastness (light fastness) and humidity fastness (humidity fastness), is excellent. In addition, it is required that the color developing performance of the color developer decreases little over time. In addition, in general ruled line character printing and desensitizing printing, there are often demands for no piling trouble and good desensitizing ink drying properties in order to withstand high-speed printing.

[Conventional technology]

In order to satisfy the required performance for pressure-sensitive copying paper, many attempts have been made to improve it from various aspects, including the coating composition consisting of a color developer, pigment, binder, and the like.

Regarding binders, carboxy-modified styrene and
Various studies have been conducted on the use of butadiene copolymer latex as a binder because the properties of the latex are effective in improving the above-mentioned properties. For example,
No. 52236 discloses a carboxy-modified styrene butadiene copolymer latex containing unsaturated IJ, JP-B No. 58-19475 and JP-A No. 53-314.
No. 05 discloses a carboxy-modified styrene-butadiene copolymer latex with an extremely high Kel content,
In Japanese Patent Publication No. 196289, a carboxy-modified styrene-butadiene copolymer latex with a high Kel content and a low Glue content is used in combination, and in Japanese Patent Publication No. 60-369.53, the swelling property of the latex film with respect to capsule oil remains below a certain level. JP-A-60-24992 proposes the use of a carboxy-modified styrene-butadiene copolymer latex containing a large amount of unsaturated carboxylic acid.However, as mentioned above, Certain carboxy-modified styrenes such as
Even if butadiene copolymer latex is used as a binder, all of the performance requirements of pressure-sensitive copying paper, such as color development, light fastness and moisture resistance, and printability such as surface strength and desensitizing ink drying properties, can be achieved at the same time. The effect of actual mushrooms is not satisfactory, and further improvements are needed to meet the needs of the market.

On the other hand, with regard to pigments, Japanese Patent Application Laid-Open No. 55-28857 proposes the use of calcium carbonate with a particle size distribution of 2μ or less and 55% or more for the purpose of improving color development and fading resistance of colored images. ing. However, when pigments with various fine particle sizes are used, the specific surface area of the pigment naturally increases, resulting in an increase in the amount of binder used. Therefore, when the amount of binder used is normal, the surface strength decreases and the workability during printing (pinking and troubles occur frequently) deteriorates. In order to improve this, if the amount of binder used is increased more than usual, the color development and the fading resistance of the color image will decrease, and the effect that can be achieved by using a pigment with a specific particle size distribution will not be fully exhibited. There is a problem.

Therefore, it can be said that with this method, it is difficult to simultaneously satisfy the above-mentioned performances required of pressure-sensitive copying paper.

Furthermore, as a countermeasure against deterioration of surface strength and workability, 06
Calcium carbonate less than μ and 0.08 μ as a binder
It is proposed to use the following styrene-butadiene copolymer latex with an extremely fine particle size. However, when using latex with such a fine particle size,
The number of latex particles naturally increases, improving its effectiveness as a binder for adhering fine calcium carbonate, but on the other hand, the total surface area of latex particles increases and the contact area with the color developer increases, resulting in desensitization. Due to this effect, the fading properties (light fastness, moisture fastness) of the colored image deteriorate, and the current situation is that satisfactory performance cannot always be obtained.

Indeed, latex with a fine particle size has a very high viscosity at normal latex concentrations, which poses problems in handling.

[Problems to be solved by the present invention]

The purpose of the present invention is to improve the various problems detailed in the prior art section, namely, to improve color development, light fastness, and moisture resistance, and at the same time improve surface strength and drying properties of desensitized ink in high-speed printing. It is an object of the present invention to provide a coating composition for pressure-sensitive copying paper that can produce colored paper for pressure-sensitive copying paper that does not cause any problems in printability and workability.

Summary of the Invention [Means for Solving the Problems] The present inventors have completed the present invention as a result of intensive research in order to achieve the above object.

That is, the present invention uses an organic color developer, light calcium carbonate, and aliphatic conjugated diolefin monomers 25 to 25 as a binder.
A copolymer latex consisting of 65% by weight, 02-10% by weight of an ethylenically unsaturated carboxylic acid amide monomer, and 25-748% by weight of other monomers copolymerizable with these. A coating composition for pressure-sensitive copying paper is provided.

The present invention will be explained in more detail below.

Examples of the organic color developer used in the present invention include Japanese Patent Publication No. 49-10856 and Japanese Patent Publication No. 51-25174.
Benzoic acid, P-tert-butyl-benzoic acid, 4-methyl-3-nitrobenzoic acid, salicylic acid, 3-
phenylsalicylic acid, 3-cyclohexylsalicylic acid,
3-tert-butyl-5-methylsalicylic acid, 3.5
-di-tert-butylsalicylic acid, 3-methyl-5-
Benzylsalicylic acid, 3-phenyl-5-(α, α′-
dimethylbenzyl)salicylic acid, 3-cyclohexyl-
5-(α,α-dimethylbenzi-norisalicylic acid, 3-
(α,α-dimethylbenzyl)-5-methylsalicylic acid, 3,5-cycyclohexino-salicylic acid, 3,5-
C(α-methylbenzyl)salicylic acid, '3,5-di(α,10α-dimethylbenzylsalicylic acid), 3
-(α-Methylbenzyl)-5=, (α1α-dimethylbenzyl)salicylic acid, 4-methyl-5-cyclohexyl-1-monocylic acid, 2-hydroxy-1-benzyl-3
-naphthoic acid, 1-benzoyl-2-hydroxy-3-
naphthoic acid, 3-hydroxy-5-cyclohexyl-2
- Various aromatic carboxylic acids such as naphthoic acid and salts of these with polyvalent metals such as zinc, aluminum, magnesium, calcium, cobalt, etc.: Special Publication No. 1973
No. 309, Special Publication No. 4'2"-2'0144, Japanese Patent Publication No. 4
6,6 as described in No. 8-1.4409.
Phenol compounds such as '-methylenebis(4-chloro-m-cresol); phenol-aldehyde resins such as P-phenylphenol-formalin resin; phenol-aldehyde resins such as P-tertiary butylphenol-acetylene resin; Feder/l/Resins and polyvalent metal salts thereof: Acidic polymers such as silicic acid-rosin resins, styrene, ethyl ether, or copolymers of vinyl methyl ether and maleic anhydride: Japanese Patent Publication No. 1973-
No. 8215, Special Publication No. 48-8216, Special Publication No. 52=
Examples include polymers of aromatic carboxylic acids and aldehydes or acetylene, as described in No. 1'326, and polyvalent metal salts thereof.

Among these organic color developers, aromatic carboxylic acids and their polyvalent metal salts, phenol resins and their polyvalent metal salts, copolymers of aromatic carboxylic acids and aldehydes or acetylene, and their polyvalent metal salts, Metal salts are particularly preferably used.

Using one or more inorganic color developers such as clay, activated clay, acid clay, attapulgide, bentonite, zeolite, silicate talc, and kaolin in combination with the organic color developer □ does not impede the effects of the present invention. As long as it can be done effectively.

The particle size and amount of light calcium carbonate used in the present invention are not particularly limited, but the average particle size is 04μ or less and the total solid content of the coating composition is 50% or more. Used wisely.

The copolymer latex as a binder used in the present invention will be explained in detail below.

The aliphatic conjugated diolefin monomer used in the present invention is selected from those having 4 to 10 carbon atoms, specifically 1,3-butadiene, 2-methyl-1,
Examples include 3-butadiene, 2,3-dimethyl-1,3-butadiene, halogen-substituted butadienes, substituted linear conjugated pentagenes, and conjugated hexadienes having a linear or side chain. The aliphatic conjugated diolefin monomer is
It is used in a monomer composition of 25 to 65% by weight.

If this ratio is less than 25% by weight, the adhesive strength will be poor;
If it exceeds 5% by weight, the light resistance decreases, which is not preferable.

Examples of the ethylenically unsaturated carboxylic acid amide monomer used in the present invention include acrylamide, methacrylamide, N-methylolacrylamide, diacetone acrylamide, and the like. The ethylenically unsaturated carboxylic acid amide monomer (d, - or two!)
- can be used in combination, and can be used in a monomer composition of 02 to 10% by weight. If this ratio is less than 0.2 weight ratio, the effect of the present invention is not recognized, and if it exceeds 10 weight ratio, the adhesive strength, especially the wet viscosity, tends to decrease, which is not desirable.

Other monomers copolymerizable with the aliphatic conjugated diolefin monomer and ethylenically unsaturated carboxylic acid amide monomer used in the present invention include -C, suy-lene, α −
Aromatic vinyl monomers such as methylstyrene, vinyltoluene, and dimethylstyrene; acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, 2-hydroxyethyl acrylate, and 2-hydroxypropyl acrylate methacrylate monomers such as methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycidyl methacrylate; unsaturated nitrile monomers such as acrylonitrile and meccrylonitrile; divinylbenzene , diallyl phthalate, sialyl maleate, triallyl cyanuate, diallyl methacrylate, ethylene glycol dimethacrylate, allyl acrylate, and other crosslinkable monomers that form a molecular crosslinked structure. These can be used alone or in combination of two or more, and are used in a monomer composition of 25 to 74.8% by weight. If this proportion is less than 25% by weight, the light resistance will decrease, and if it exceeds 748% by weight, the contact M strength will decrease, which is not preferable. Kel content of the copolymer latex used in the present invention Although there is no particular restriction on
00 weight range is preferable, more preferably 95 to 1
A range of 0.00 weight ratio is suitable. In addition, there are no particular restrictions on the particle size of the copolymer latex, but 7.4 Taking into account the viscosity of the copolymer latex 7. It is preferable to use Furthermore, as for the method for producing the copolymer latex, known emulsion polymerization methods such as continuous emulsion polymerization, -stem-pore polymerization, and two-stage emulsion polymerization can be employed, and in this case, various known emulsifiers, chain transfer agents, Additives used in general emulsion polymerization, such as polymerization initiators, electrolytes, and chelating agents.
Auxiliary agents can be used, and polymerization temperatures can be selected from any number of companies, including high and low temperatures.

When preparing a color developer-containing coating composition in the present invention,
The copolymer latex is mixed in a dispersion system of a color developer, and the dispersion medium at this time is water and/or an organic solvent compatible with the copolymer latex. Various auxiliary agents, such as dispersants, antifoaming agents, and surfactants, which have been conventionally used in the production of pressure-sensitive copying paper, can be used. The amount of copolymer latex added is mainly considered from the viewpoint of adhesive strength and economic efficiency, and is usually determined by the amount of the coating composition (solid content).
It can be contained in an amount of 3 to 50 parts by weight per 100 parts by weight.

These color developers should be sufficiently retained on the substrate surface.Usually, starch, casein, gelatin, gum arabic,
Albumin, Torari Gantt Gum, Methylcellulose, Ethylcellulose, Carboxyethylcellulose, Carboxyethylcellulose, Hydroxyethylcellulose,
It can be applied to the substrate surface together with a binder such as polyvinyl alcohol, carboxy-modified snalene-butadiene copolymer, vinyl acetate copolymer, acrylic copolymer, etc., but of course it can be applied in combination with a binder such as those previously used71. can be effectively carried out as long as it does not impede the effects of the present invention.

The following margins [Examples] The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to the Examples. In addition,
All parts and references used refer to parts and percentages by weight unless otherwise specified.

On the other hand, the test methods for various measurement items are as follows.

(al) A coated surface provided with a color-developing layer in a color-forming paper for color-forming pressure-sensitive copying paper,
The microcapsule-coated surface of a commercially available microcapsule-coated paper coated with microcapsules containing microdroplets of alkylnafucrene containing crystal violet lactone was superimposed, and the paper was colored under a load of 100 kq/cm and placed in a dark place. After standing for a while, the density of the colored portion was measured using a Macbeth color densitometer. (Hereinafter, the measured value will be referred to as the initial density, and the larger the value, the better the color development.

(bJ) The colored paper developed under the conditions described in (a) is further exposed to direct lδ injection light for two days, the color density of the colored area is measured, and the light fastness is determined according to the following formula. Note that the larger the value, the better the light resistance.

(el Moisture resistance) Colored paper developed under the conditions of (a) above was heated to a relative humidity of 90%.
% atmosphere for 2 days, the color density of the colored part was measured, and the moisture resistance was determined according to the following formula. Note that the larger the value, the better the moisture resistance.

(dl Desensitizing ink drying RI printing machine is used to print the desensitizing ink solidly on colored paper.Then, the desensitizing ink is printed on the black paper (replica) at regular intervals, and the desensitizing ink is transferred to the replica. The amount of ink is 5
Judgment is made visually using a graded evaluation. The smaller the amount of desensitized ink transferred, the faster the desensitized ink dries, and the better the drying properties of the desensitized ink become. The outline of the five-level evaluation is as follows: 50 (fast drying) to 10 (slow drying) (e) Surface strength dry pick: The surface strength of the colored paper is measured using an RI printing machine.

Printed three times with commercially available off-cent ink, and evaluated the paper on a five-point scale based on the state of the paper with the naked eye as shown below.

50 (excellent) to 10 (poor) Wet Vic: Measure the surface strength of colored paper in a wet state using an RT printing machine.

After moistening the surface of the colored paper with a Molton roll,
Print once with a commercially available off-cent ink, and evaluate the paper using the naked eye based on the state of the paper at that time, using the following 5-level evaluation.

50 (excellent) - 10 (poor) Below 0 margins Example-1 (Preparation of copolymer latex) In an autoclave that had been purged with nitrogen in advance, the monomer mixture and chain transfer agent shown in Table 1, and sodium alkylbenzenesulfonate were placed. 10 parts, sodium hydrogen carbonate 05
15 parts of potassium persulfate and 100 parts of pure water were polymerized at 70°C for 16 hours to form a copolymer latex.
I got ~■.

(Preparation of coating composition) Add 85 parts of various calcium carbonate and kaolin having different average particle sizes listed in Table 2 to 15 parts of zinc 3-phenyl-5-(α,α-dimethylbenzyl)salicylate, and add polyacrylic Disperse in water using 0.6 parts of sodium chloride at a concentration of 5.
0% Slurry 7&: Prepare.

Next, 3 parts of oxidized starch and 14 parts of copolymer latex (solid content) shown in Table 2 were added to obtain coating compositions 1 to 12 with a solid content of 33%.

(Preparation of colored paper and performance evaluation) Using the obtained coating compositions 1 to 12, 52P/m
'A dry coating amount of 5y/nX was applied to one side of high-quality paper to create colored paper. The performance of each colored paper obtained was evaluated and the results are shown in Table 2.

Table 1 ・Example 2 (Preparation of copolymer latex) Into an autoclave that had been purged with nitrogen in advance, the monomer mixture and chain transfer agent shown in Table 3 were added, and 10 parts of pure water and 10 parts of pure water were added.
0 parts and polymerized for 8 hours at 68°C. Copolymer latex a-jk1 etc. -8 (Preparation of coating composition) Using the obtained copolymer latex a-jk, each of the following All coating compositions 21 to 30 were prepared according to the recipe.

Active white soil 1
5 parts light calcium carbonate (average particle size 015μ)
60 parts Sodium polyacrylate 06 parts Starch oxide 3 parts Copolymer latex (solid content) 14 parts Desired amount of water necessary to adjust the solid content to 33% (coloring paper preparation and performance evaluation) Paint composition obtained 65y/m' using objects 21 to 3o
Each side has a dry coating weight of 55i'/nr on one side of high-quality paper.
Apply it to obtain colored paper. The performance of each colored paper obtained was completely evaluated and the results are shown in Table 4.

:23. Example-3 Using the copolymer latex a-jk obtained in Example-2, coating compositions 31 to 40 were prepared according to the following formulations. Colored paper was prepared and evaluated in the same manner as in Example-2. The results are shown in Table-5.

Active white soil 1
5 parts light calcium carbonate (average particle size 035μ) 7
0 parts sodium hexametaphosphate 1 part sodium hydroxide 08 parts oxidized starch
7 parts copolymer latex (solid content)
15 parts Desired water margin 0 required to adjust solid content to 30% Example 4 (Preparation of copolymer latex) Monomers and chain transfer agents used in the first stage polymerization shown in Table 6 and sodium alkylbenzenesulfonate 0
6 parts of sodium bicarbonate, 06 parts of potassium persulfate, 100 parts of pure water and gold were placed in an autoclave which had been purged with nitrogen in advance, and polymerization was carried out at 65°C until the polymerization conversion rate reached 70% or more. Next, in order to perform the second stage polymerization, the monomers used in the second stage polymerization shown in Table 6 were added to the same autoclave, and the polymerization was completed at 68°C to form copolymer latex A-G. I got it. The final polymerization conversion rate was 98% or more in all cases.

(Preparation of coating compositions) Using the obtained copolymer latex A-CJ-, coating compositions 41 to 47 were obtained in the same manner as in Example-2.

The following margins (coloring paper preparation and performance evaluation) Using the obtained coating compositions 41 to 47, each example -
Colored paper was prepared in the same manner as in 2 and evaluated. The results are shown in Table-7.

Below, the margin C1 Effects of the invention [Effects of the invention] If the coating composition for pressure-sensitive copying paper of the invention is used, color development,
Obtain high-quality colored paper for pressure-sensitive copying paper with excellent light fastness and moisture resistance, and at the same time, without any problems in printability and workability such as surface strength and desensitized ink drying properties even during high-speed printing. be able to.

Claims (1)

[Claims] 1. Organic color developer, light calcium carbonate, 25 to 65% by weight of aliphatic conjugated diolefin monomer as a binder, 0.2 to 10% by weight of ethylenically unsaturated carboxylic acid amide monomer, and co-organized with these. Other polymerizable monomers 25-74.
8% by weight of a copolymer latex. A coating composition for pressure-sensitive copying paper.