JPH0478571A - Carbonless pressure-sensitive copy paper - Google Patents

Abstract

PURPOSE:To obtain carbonless pressure sensitive copy paper sufficiently well- balanced with respect to developed color density and static pressure developed color contamination by using amphoteric latex as a binder. CONSTITUTION:Carbonless pressure-sensitive copy paper is fundamentally formed by applying a coating solution containing an anionic microcapsule including a colorant, a buffer material and a binder to paper to dry the coating layer and, as the binder, an amphoteric latex is used. By adding the amphoteric latex, the particles of the amphoteric latex adhere to the surface of the microcapsule discontinuously to become a form protecting the microcapsule. The paper coated in this form becomes markedly well in antistaining properties because the microcapsule is sufficiently protected by the latex particles. That is, when pressure of 200-600 kg/cm<2> is applied at the time of color development, since the surface of the microcapsule is discontinously protected, the inner phase of the microcapsule is easily discharged after destruction and developed color density also becomes high. Further, the aptitude of the coating solution becomes well.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to carbonless pressure sensitive copying paper having a coating of microcapsules. More specifically, the present invention relates to a carbonless pressure-sensitive copying paper that has excellent stain resistance and coating suitability.

[Conventional technology]

Carbonless pressure-sensitive copying paper is usually produced by coating a support with microcapsules containing a colorless leuco dye (coloring agent) and a color developer. Each is coated individually on a support and used as a base paper and a bottom paper, and each coated on both sides is generally used as a middle paper. Self-contained papers have also been used in which one or two layers of each are coated on one side of the support. Multiple sheets of these sheets are combined as appropriate, and physical pressure is applied by writing, typewriter, impact printer, etc. to destroy the microcapsules, and the leuco dye inside the capsules comes into contact with the color developer, causing color development. This is a system that can obtain recorded images. In general, the following two items are listed as important quality conditions required for carbonless pressure-sensitive copying paper. (1) Dark and clear images can be obtained in a short time and there is no deterioration over time. (2) When color development is not intended, i.e., during the manufacturing process of carbonless pressure-sensitive copying paper, during cutting and various printing processes, and during storage and handling in sheet or rolled form, color development stains should not occur. . Since (1) and (2) above have contradictory effects, it is generally difficult to fully satisfy both and maintain a balance. Generally, a coating layer containing microcapsules consists of microcapsules, a buffer material, a binder, and other additives; Partial improvements can be made by modifying factors such as, and many proposals have been made regarding this. ■The method for producing microcapsules containing a coloring agent is as follows:
Although many are known, the representative methods include: - Coacervation method using a polyion complex of gelatin-gum arabic.・An interfacial polymerization method that forms an insoluble film at the interface between a hydrophilic liquid as a dispersion medium and a hydrophobic liquid to be included.・After adding a coating resin initial condensate such as melamine-formalin resin or urea-formalin resin from the hydrophilic liquid side that will serve as a dispersion medium, it is converted into a resin and encapsulated.
itu polymerization method. can be mentioned. Recently, raw materials are cheap and stably supplied, highly concentrated microcapsule emulsions can be obtained, and the manufacturing process is simple.
For these reasons, synthetic resin capsules, especially capsules made by the ingifg polymerization method, have come to be used. In addition, a method has been proposed to solve the above problems (1) and (2) by aggregating anionic capsules with an amphoteric polymer electrolyte such as gelatin and hardening them with formaldehyde etc. ( (Japanese Patent Application Laid-Open No. 60-166026). Regarding the type of binder (2), proposals have recently been made to use various latexes. The latex itself can be combined with other known binders (polyvinyl alcohol, starch glue, etc.)
It has the advantage of higher cushioning properties. However, since it is a fine emulsion, its permeability into the support layer is high and sufficient effects cannot be obtained in many cases. As a solution to this problem, it has been proposed to use all or part of an alkali-thickened latex with reduced permeability (JP-A-64-49678, JP-A-1234289, JP-A-1-234290, JP-A No. 1288480, JP-A No. 2-3367, and other publications). Although a number of proposals have been made as described above, the current situation is that nothing satisfactory has been obtained yet.

[Problems to be solved by the invention]

The present invention simultaneously overcomes the quality and manufacturing problems of conventional carbonless pressure sensitive copying paper. That is, when sufficient color density is obtained, color stains are significantly reduced. Specifically, the purpose is to improve the balance characteristics of the following ASB, which are contradictory factors. Improved color density for people 2. A dark and clear copy image can be obtained, and a clear image can be obtained even when copying a large number of sheets. Prevents coloring stains when B3 coloring is not intended. Types of colored stains include: - Dynamic colored stains that occur during rubbing; - Static pressure colored stains that are applied during storage, transportation, printing, and guillotine cutting in rolled or sheet form; - Heated and humidified conditions. Examples include colored stains caused by capsule destruction during long-term storage. In any of these cases, it should exhibit excellent resistance to color development and staining. The object of the present invention is to obtain carbonless pressure-sensitive copying paper that satisfies all of the above items.

[Means to solve the problem]

As a result of extensive research, the present inventors have found that, in carbonless pressure-sensitive copying paper made by applying and drying a coating liquid containing anionic microcapsules containing a coloring agent, a buffer material, and a binder, the binder The problem was solved by using a zwitterionic latex as a solution. The amphoteric latex used in the present invention means that when mixed with anionic microcapsules, it ionically associates with the anionic microcapsules in the pH range of 7 to 14, causing them to partially aggregate and/or aggregate. It is latex with properties. Specifically, a substance composed of a mixture of a cationic group and an anionic group in the same molecule, and/or a mixture of a substance with a cationic group and an anionic group, and more. Latex is preferred. Recently, amphoteric latex has been developed, and its use can be effective. Note that the amphoteric latex in the present invention is broadly defined to include those obtained by emulsifying a polymer compound by solution polymerization, those obtained by emulsion polymerization, and the like. When microcapsules are produced using an anionic polymer as an emulsifier, the resulting microcapsules themselves are generally anionic. On the other hand, the latex itself that has been used conventionally is also generally anionic. When the two are mixed, they will not join or aggregate due to electrostatic repulsion. If a cationic substance is added, the two will aggregate, but due to their strong bond, they will form a large aggregation, making the coating solution unsuitable for carbonless pressure-sensitive copying paper. By adding the amphoteric latex, the amphoteric latex particles adhere discontinuously to the capsule surface and protect it. The upper paper (CB) coated in this form is
Microcapsules are well protected by latex particles, and stain resistance is much better. At the time of color development, i.e. 20
When a pressure of 0 to 600 kg/d is applied, the capsule surface is protected discontinuously by the particles, so that the internal phase is easily released after destruction, and the coloring density becomes high. Moreover, the liquid properties of the coating liquid are improved. On the other hand, when a water-soluble amphoteric polymer compound such as gelatin is used, the microcapsules are continuously coated, which improves color stain resistance, but the release of the internal phase upon color destruction is insufficient. As a result, good coloring performance cannot be obtained. or,
A coating liquid with good liquid properties cannot be obtained as in the case of using amphoteric latex. The amphoteric latex used in the present invention is polymerized using part of the cationic monomer during emulsion polymerization of the anionic latex. ■ After producing anionic latex, anionic groups and/or
Alternatively, a part of the nonionic group is chemically changed into a cationic group. (2) Use a cationic and/or amphoteric dispersant for anionic latex. Particularly preferred are those produced by methods such as, but when mixed with anionic microcapsules, pH = 7 to 1.
This is not the case as long as the latex has the property of ionically associating with the anionic capsule and partially aggregating and/or aggregating it in the region 4. A specific example of the above item (■) is N. (Meth)acrylic acid ester monomers such as N-dimethylaminoethyl methacrylate (1)M) have been proposed (Japanese Unexamined Patent Publication No. 61-261302). As a specific example of the above (2), latex containing an acrylamide group is converted into an amino group by Hofmann rearrangement to be amphoteric. It is also possible to introduce tertiary amines by Mannich reaction or the like. The cationic dispersants used in the above (2) include laurylpyridinium chloride, octylbenzyltrimethylammonium chloride, dodecyltrimethylammonium chloride, and condensates of primary aliphatic amines and ethylene oxide. Amphoteric dispersants include quaternary amine derivatives of fatty acids such as cocoa-β-alanine, the methyl ester of dimethyloctadecylbetaine chloride, and cetyldimethylammonium internal carboxylate. The amount of amphoteric latex to be used varies depending on the balance of ionic strength, but is preferably in the range of 0.1 to 100 parts by solid weight per 100 parts by solid weight of anionic microcapsules. As the binder, in addition to the amphoteric latex, anionic latex such as styrene-butadiene copolymer latex, vinyl acetate-based latex, various acrylic-based latex, or alkaline earth metal anionic latex can also be used in combination. As the alkali thickening anionic latex, the commonly used ones mentioned above can be used. There is no problem in using an appropriate amount of a water-soluble polymer substance such as soluble starch, casein, gelatin, gum arabic, polyvinyl alcohol, or methyl cellulose. Usually, the combined amount of these binders is 1 microcapsule.
The range of 0 to 100 parts by solid weight is preferred. Particularly preferred is a range of 0 to 50 parts by solid weight. The encapsulation method used in the present invention is not particularly limited, but since microcapsules formed by coacervation may have a film destroyed in latex, interfacial polymerization or in-cilu polymerization may be used. It is preferable to use legal encapsulation methods. The emulsifier used for encapsulation is preferably an anionic polymer electrolyte AV material. Specifically, styrene-maleic anhydride copolymer, styrene-benzyl methacrylate-maleic anhydride copolymer. α-methylstyrene-maleic anhydride copolymer. Nuclear monomethyl-substituted styrene-maleic anhydride copolymer, nuclear dimethyl-substituted styrene-maleic anhydride copolymer, styrene-maleic anhydride monomethyl ester copolymer, ethylene-maleic anhydride copolymer, polystyrene sulfonic acid, polyacrylic acid. An aqueous solution of acrylic acid-acrylic acid ester copolymer 2 or the like is used. The emulsifier used for interfacial polymerization encapsulation is
In addition to the above in≦ilu encapsulation, PVA, CMC
, HEC, and various (wheat, potato, corn, etc.) starches may also be used. It should be noted that there is no problem even if known substances having nonionic, cationic, or amphoteric surfactants are added and used in combination to the extent that they do not cause problems in the encapsulation process. A buffer is added for the purpose of preventing destruction of microcapsules. In general, wheat starch, potato starch, corn starch, fine cellulose powder, synthetic plastic pigments, etc. are preferred, and the amount is usually in the range of 10 to 400 parts by solid weight per 100 parts by solid weight of microcapsules. It is preferable to use Even 10-100
A range of parts by weight solids is particularly preferred. The coating method used in the present invention is a conventional coating machine (
coater) and dried. As a specific coating machine, an air knife coater, a blade coater, a rod coater, a bar coater, a roll coater, a size press coater, a curtain coater, etc. are used. As the support, acidic paper or neutral paper mainly composed of cellulose fibers is usually used, but synthetic paper may also be used. The color developer used in combination with the carbonless pressure-sensitive copying paper obtained by the present invention is preferably a phenol resin compound, a salicylic acid metal salt compound, a solid acid compound, or the like.

【Example】

Next, comparative examples and examples will be shown. The following parts numbers are expressed in parts by weight of dry solids, unless otherwise specified. Example 1 U microencapsulation] 4 parts of crystal violet lactone (CVL) was dissolved in a diarylethane solvent (Hysol SAS N-29).
6: manufactured by Nippon Petrochemical Co., Ltd.)) was dissolved in 96 parts. 220 parts of the above hydrophobic liquid was gradually added to 180 parts of a 5% aqueous solution of styrene-maleic anhydride copolymer (manufactured by Hikariyo Kagaku Co., Ltd.) under strong stirring, and the stirring was continued until the volume average particle diameter became 5 microns. Next, an emulsion was obtained. Separately, 11 parts of melamine, 2 parts of 37% formaldehyde aqueous solution
Melamine obtained by heating and dissolving 1.2 parts and 28.2 parts of water.
A formaldehyde initial condensate aqueous solution was added to the emulsion and stirred for 2 hours at a temperature of 70°C to obtain a microcapsule liquid. [Preparation of carbonless pressure-sensitive copying paper (CB)] 100 parts of the above microcapsules, 35 parts of wheat starch, and a styrene-butadiene copolymer-based amphoteric latex having a quaternary alkylamine group on the surface (Acostar C122:
(manufactured by Mitsui Cyanamid Co., Ltd.) was added thereto. When adding the latex, the pH in the latex and other material system is adjusted so that the latex appropriately aggregates around the anionic microcapsules, and the final coating for carbonless copying paper has a pH of 9.0. A working solution was obtained. The coating liquid was applied using the air knife coating method to produce 40 g/
Dry capsule coating amount is 2゜5g/r on rrf high quality paper.
RF to obtain carbonless pressure-sensitive recording paper (CB). [Measurement of color density and static pressure color stain] The obtained CB was combined with a commercially available carbonless pressure-sensitive copying paper lower paper (Mitsubishi NCR paper lower downstream paper 40.40 g/n (base lower paper)), and the following was done. The color density and static pressure color stain were measured. ・The upper paper and the lower paper, which were combined with the color density, were colored under a pressure of 400 kg/ci. CF receipt reflectance measurement was performed using Color Difference manufactured by Nippon Heavy Industries Ltd. Meter NDIOIDP
It was measured using a mold. The display was expressed as reflectance of the colored part/reflectance of the untreated part (background part) x i 00 (%). The smaller this value is, the darker the color density becomes. ・After holding the top paper and bottom paper, which are combined with static pressure color development stains, under a pressure of 20 kg/cnf for 60 seconds, remove the dirt on the bottom paper using the above method. It was measured using the same method as the color density. As this value increases, it indicates that the static pressure color stain decreases. Polymer latex (#0
853: manufactured by Japan Synthetic Rubber Co., Ltd.) 10 parts and Accostar 0
Example 1 was carried out in the same manner as in Example 1, except that 10 parts of 122 were used. Example 3 Instead of 20 parts of Acostar C122, #0853
5 parts of Acostar CJ-22, 10 parts of Acostar CJ-22, alkali-thickened styrene-butadiene copolymer latex (#06
The same procedure as in Example 1 was conducted except that 5 parts of 28.28 (manufactured by Japan Synthetic Rubber Co., Ltd.) were used. Example 4 Instead of 20 parts of Acostar 0122, #0628
The same procedure as in Example 1 was conducted except that 10 parts of Acostar 0122 and 10 parts of Acostar 0122 were used. Example 5 Instead of 20 parts of Accostar 0122, styrene-
Butadiene copolymer-based amphoteric latex (#086
The same procedure as in Example 1 was carried out except that 20 parts of 1. manufactured by Japan Synthetic Rubber Co., Ltd.) were used. Comparative Example 1 Instead of 20 parts of Acostar C122, #0853
The same procedure as in Example 1 was carried out except that 20 parts of . Comparative Example 2 Instead of 20 parts of Acostar 0122, #0628
The same procedure as in Example 1 was carried out except that 20 parts of . Comparative Example 3 After completing the "microencapsulation" of Example 1, the liquid temperature was set to 60°C.
and for 100 parts of microcapsule solid weight,
A 10 vt% gelatin aqueous solution corresponding to 1 part of solid weight was also added. After sufficient stirring and mixing, 2 parts of 1% hydrochloric acid was gradually added to adjust the pH to 3. Next, 37w (%i) formalin corresponding to 0.8 parts of solid weight was added and stirred for about 12 hours. To 101.8 parts of the above microcapsule and gelatin association, 20 parts of Acostar 0122 was added. ,
The same procedure as in Example 1 was conducted except that 19 parts of 10853 were used. The results of Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1. (Left below) Table A: Non-alkali thickened latex B, alkali thickened latex C, amphoteric latex D = amphoteric polymer (gelatin)

【Effect of the invention】

As is clear from the above, a carbonless pressure-sensitive copying paper with a well-balanced color density and static color stain was obtained. A further unintended effect is that a coating liquid with excellent coating suitability can be obtained.

Claims (1)

[Claims] Basically, amphoteric latex can be used as a binder in carbonless pressure-sensitive copying paper, which is made by coating and drying a coating solution containing anionic microcapsules containing a coloring agent, a buffer material, and a binder. Features carbonless pressure-sensitive copying paper.