JP2559060B2 - Microcapsule coating liquid for sensitive paper - Google Patents

Description

The present invention relates to a microcapsule coating liquid for pressure-sensitive copying paper. More specifically, the present invention relates to a microcapsule coating liquid which provides a microcapsule coated paper for pressure-sensitive copying paper which is excellent in color development, pressure stain resistance and strength.

[Conventional technology]

Generally, a pressure-sensitive copying paper contains an upper paper coated with fine capsules containing an electron-donating colorless or light-colored leuco dye dissolved in an organic solvent (capsule oil) on the back side, and an electron-accepting developer. It consists of a lower sheet with a developing layer on the front surface, a developing sheet on the front surface, and a middle sheet with a capsule coated on the back surface.The two coated surfaces are laminated so that they face each other, and pressure is applied with a ballpoint pen or typewriter. By adding, the capsule of the pressurized part is destroyed,
The print oil can be obtained by transferring the capsule oil containing the leuco dye to the color developing layer to cause a color development reaction.

Further, in addition to the upper paper and the middle paper having the back surface coated with the microcapsules as described above, a single recording sheet or a self-contained paper having both the capsule and the color developer coated on the same surface of the support is used. It also includes what is called.

In recent years, these pressure-sensitive copying papers have shown remarkable growth in demand along with the rationalization of office work, the development of the information industry, and the spread of computers, and their applications have been diversified.

Such pressure-sensitive copying paper develops color only after the microcapsules are destroyed by the writing pressure of a ballpoint pen or typewriter, but the microcapsules are destroyed by the pressure generated during the manufacturing process, the transportation process, and the storage before use. There was a problem of pressure pollution that the color was already developed.

In order to solve such problems, a method of using inactive particles, which are slightly larger than the particle size of the capsule, as a capsule protective material is generally used, but the use of such a protective material for the purpose of improving pressure contamination resistance. On the contrary, when the amount is increased, the color developability at the time of use is deteriorated, which is not a sufficient solution.

Further, as disclosed in JP-A-61-280985 and JP-A-61-273985, a proposal has been made to solve the problem by using a copolymer latex having a specific composition as a binder, but it is still satisfactory. The current situation is that nothing has been obtained.

[Problems to be Solved by the Present Invention]

An object of the present invention is to provide a microcapsule coating liquid for pressure-sensitive copying paper, which is capable of obtaining a microcapsule-coated paper for pressure-sensitive copying paper, which is excellent in pressure stain resistance and strength, without deteriorating color development. Especially.

[Means for solving problems]

As a result of intensive studies to solve the above problems, the present inventors have found that an alkali-insoluble copolymer latex having a specific composition and an alkali-soluble copolymer latex having a specific molecular weight are used as binders in a specific ratio. It was found that by using the microcapsule coating liquid used as above, a microcapsule coated paper excellent in pressure stain resistance and strength can be obtained without lowering the color developability, and the present invention was completed.

That is, the present invention provides an aliphatic conjugated diolefin monomer 25 as a binder (II) per 100 parts by weight of a microcapsule (I) containing an organic solvent in which a colorless or light leuco dye is dissolved.
~ 60% by weight, ethylenically unsaturated carboxylic acid monomer 0.5 ~ 1
0% by weight and other monomers copolymerizable therewith 30-74.
An alkali-insoluble copolymer latex (A) composed of 5% by weight and an alkali-soluble copolymer latex (B) having a weight average molecular weight of 15,000 to 500,000 are in a weight ratio of (A) /
The present invention provides a microcapsule coating liquid for pressure-sensitive copying paper, which contains 5 to 40 parts by weight in the range of (B) = 97 to 80/3 to 20.

 Hereinafter, the present invention will be described in detail.

The aliphatic conjugated diolefin-based monomer constituting the alkali-insoluble copolymer latex (A) of the present invention is 4
~ Selected from those having 10 carbon atoms, specifically
1,3-butadiene, 2-methyl-1,3-butadiene, 2,3
-Dimethyl-1,3-butadiene, halogen-substituted butadienes, substituted linear conjugated pentadienes, conjugated hexadienes having a straight chain or a side chain, and the like, and one kind or two or more kinds can be used.

Examples of the ethylenically unsaturated carboxylic acid monomer include monocarboxylic acids such as acrylic acid and methacrylic acid, dicarboxylic acids such as itaconic acid, fumaric acid and maleic acid, and maleic anhydride. The above can be used.

Other monomers copolymerizable with them include aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene and dimethylstyrene, methyl acrylate, ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate. , Lauryl acrylate, 2
-Hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, 2
-Unsaturated carboxylic acid alkyl ester monomers such as hydroxypropyl methacrylate, unsaturated nitrile monomers such as acrylonitrile and methacrylonitrile, and further acrylamide, N-methylol acrylamide, glycidyl acrylate, glycidyl methacrylate and the like. One kind or two or more kinds can be used.

The aliphatic conjugated diolefin-based monomer is used in an amount of 25 to 60% by weight, but if it is less than 25% by weight, the strength and pressure stain resistance are inferior, and if it exceeds 60% by weight, the color developability is deteriorated. It is preferably 30 to 55% by weight.

0.5-10% by weight of ethylenically unsaturated carboxylic acid monomer
Used in, but less than 0.5% by weight or 10% by weight
If it exceeds, the strength is lowered, which is not preferable. Preferably 1 to
It is 7% by weight.

Other monomers copolymerizable with these are used in an amount of 30 to 74.5% by weight, but if the amount is less than 30% by weight, the color developability is inferior.
If the content is more than 10% by weight, the strength and pressure stain resistance are poor, which is not preferable. It is preferably 38 to 69% by weight.

Further, as a method for producing the alkali-insoluble copolymer latex (A), an emulsion polymerization method can be generally adopted.

The alkali-soluble copolymer latex (B) in the present invention is an opaque liquid at pH 5 or lower, but becomes transparent or translucent when adjusted to pH 9 or higher.
Specifically, 3 of the alkali-soluble copolymer latex is used.
% Aqueous solution adjusted to pH 9 or higher with 3% NaOH aqueous solution has a transmittance of 80% or higher at a wavelength of 700 nm.
If the transmittance is less than 80%, sufficient pressure stain resistance cannot be obtained.

Furthermore, the weight average molecular weight measured by GPC method is 15,000.
Must be in the range of ~ 500,000. The molecular weight is 1
When it is less than 5,000, the pressure stain resistance is poor, and when it is more than 500,000, the color development is poor, which is not preferable. Preferably 15,000-35
It is 0,000.

The alkali-soluble copolymer latex (B) in the present invention is a copolymer latex composed of an ethylenically unsaturated carboxylic acid monomer and an unsaturated carboxylic acid alkyl ester monomer. Are the same as those described for the alkali-insoluble copolymer latex (A), and one kind or two or more kinds can be used respectively.

The composition ratio thereof is not particularly limited, but is preferably 20 to 50% by weight of the ethylenically unsaturated carboxylic acid monomer and 80 to 50% by weight of the unsaturated carboxylic acid alkyl ester monomer.

The alkali-soluble copolymer latex (B) in the present invention can generally employ emulsion polymerization, and as the emulsifier in that case, a conventionally known anionic surfactant,
Nonionic surfactant, etc. and the following general formula I and / or II
Although it is possible to use the oligomer represented by the above, it is preferable to use the oligomer alone or in combination with a conventionally known emulsifier, and the amount of the oligomer used is 100% from the viewpoint of color development and pressure stain resistance. More preferably, it is 0.5 to 20 parts by weight per part by weight.

General formula Where R _{1 is} an alkyl group having 5 to 20 carbon atoms, R _{2 to} R _{7 is} hydrogen or an alkyl group having 1 to 5 carbon atoms, and a carboxyl group or a carboxymethyl group, or an ammonium base, an amine base, an alkali metal base or an alkali earth metal bases _{X: -COOC 2 H 4 OH,} -COOC 3 H 6 OH, -CONHCH 2 OH, -CONHC 2 H 5, -CONHCH 3, -CONHC 3 H 7, -COOCH 3, -COOC 2 H 5 , -COOC ₄ H ₉ , -CONH ₂ , -CN, (R ₈ : hydrogen, halogen or an alkyl group having 1 to 4 carbon atoms) Y: —OCH ₃ , —OC ₂ H ₅ , —CH ₂ OH or —COOR ₉ (R ₉ : hydrogen, ammonium salt, amine base, alkali Metal or alkaline earth metal) Z: sulfonic acid group, Or _{- (CO) O-CnH 2} nSO 3 H or their alkali metal base, (n-1~4) a: Number of 0 to 100 b: The number of 1 to 100 c: 1 to 100 number above co of The polymer latexes (A) and (B) are usually produced in separate reactors, but after polymerizing the alkali-insoluble copolymer latex (A), the alkali-soluble copolymer latex (B) is produced in the same reactor. It is sufficiently possible to use the copolymer latex obtained by polymerizing as a binder.

The microcapsule (I) in the present invention is a gelatin capsule by a commonly used coacervation method,
Any of polyurea capsules by the interfacial polymerization method, polyurethane by the in-situ method, melamine formalin resin capsules and the like can be used.

When coating these microcapsules on a support, as a binder, the alkali-insoluble copolymer latex (A) and the alkali-soluble copolymer latex (B) are used in a weight ratio of (A) / (B) = 97-80 / It must be used in the range of 3-20. If the weight ratio of the alkali-soluble copolymer latex is less than 3, the pressure resistance stain resistance is not improved, and if it exceeds 20, the color developability and strength are deteriorated.

These copolymer latexes (A) and (B) are used as a binder in an amount of 5 to 4 per 100 parts by weight of microcapsules.
If it is used in an amount of less than 5 parts by weight, pressure stain resistance and strength will be poor, and if it exceeds 40 parts by weight, color development will be poor. It is preferably 10 to 30 parts by weight.

In preparing the microcapsule coating liquid of the present invention, the copolymer latexes (A) and (B) used as binders may be separately added to the microcapsule dispersion liquid, or (A) in advance. You may add after mixing and (B). Furthermore, it is also possible to use the copolymer latexes (A) and (B) and the microcapsule dispersion together with other water-soluble binders and capsule protectors.

〔Example〕

Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to the examples. All parts and% used are parts by weight and% by weight, unless otherwise specified.

The test methods for various measurement items are as follows.

(A) Coloring properties The microcapsule-coated papers prepared in the examples and comparative examples of the present invention were superimposed on the lower paper of a commercially available pressure-sensitive copying paper, printed with an electric typewriter, and visually observed for color density after 5 minutes. Was determined.

(B) Stain resistance against pressure After the microcapsule-coated paper prepared in the examples of the present invention and the comparative example and the lower sheet of the commercially available pressure-sensitive copying paper are overlaid, they are pressed with an RI printing machine to stain the lower sheet. It was judged visually.

(C) Strength Printing was performed using an RI printer, and the picking state was visually determined.

The evaluation of (a), (b), and (c) is made into 10 steps, and 10 (good) → 1 (bad).

Preparation of Alkali-Insoluble Copolymer Latex (A) A monomer mixture shown in Table 1 and t-dodecyl mercaptan 0.5 were placed in an autoclave previously purged with nitrogen.
Parts, sodium alkylbenzene sulfonate 1.0 parts, sodium bicarbonate 0.5 parts, potassium persulfate 1.0 parts and pure water
100 parts of it was added and polymerization was carried out at 70 ° C. for 16 hours with stirring to obtain alkali-insoluble copolymer latexes i to vii.

Preparation of Alkali-Soluble Copolymer Latex (B) In an autoclave previously purged with nitrogen, the monomer mixture, emulsifier, t-dodecyl mercaptan and sodium bicarbonate 0.5 parts, potassium persulfate 0.5 parts and pure water 200 shown in Table 2 were prepared. Parts were added and polymerization was carried out at 70 ° C. for 8 hours with stirring to obtain latexes a to j. After diluting these latexes to a solid content of 3%, adjusting the pH to 9-10 with 3% NaOH aqueous solution, and then measuring the transmittance with a spectrophotometer at a wavelength of 700 nm and a path length of 10 mm. The transmittance was 80% or more. Moreover, when the molecular weight was measured using polyethylene glycol as a reference under conditions of pH 9 to 10 using an aqueous GPC column, the molecular weight was 15,0 except for h and j.
It was in the range of 00 to 500,000.

Preparation of microcapsules 5 of polyvinylbenzene sulfonic acid adjusted to pH 4
100% aqueous solution, crystal violet lactone 4
Part of the color developer oil was dissolved in 100 parts of an organic solution (KMC-113 manufactured by Kureha Chemical Co., Ltd.) to emulsify and disperse to obtain an O / W type emulsion. To this, 12.5 parts of 80% melamine formalin initial condensate (Sumitomo Chemical Co., Ltd .: SR-613) was added, polymerized at 60 ° C. for 2 hours, and then adjusted to pH 7 to 8 with NaOH to prepare a microcapsule dispersion liquid. It was created.

Examples 1 to 9 and Comparative Examples 1 to 7 Microcapsule dispersion solid content prepared by the above method
With respect to 100 parts, the alkali-insoluble copolymer latex and the alkali-soluble latex shown in Tables 3 and 4 are 27 parts and 3 parts in solid content, respectively, and wheat starch 30 parts.
Parts, adjust the pH to 8 with 10% caustic soda, then adjust the solid content to 20%, and use 4.0g on the base paper with a wire bar.
It was coated so as to be / m ² to prepare a microcapsule coated paper. Color development using this microcapsule coated paper,
The pressure stain resistance and strength were examined.

Examples 10 to 13 and Comparative Examples 8 to 11, except that the above microcapsules, alkali-insoluble copolymer latex i, alkali-soluble copolymer latex a, polyvinyl alcohol, and wheat starch were used in the proportions shown in Table-5, A microcapsule-coated paper was prepared in the same manner as in Example 1, and the color developability, pressure stain resistance and strength were measured.

[Effects of the Invention] As described above, by using the microcapsule coating liquid of the present invention, a microcapsule coated paper for pressure-sensitive copying paper excellent in color developability, pressure stain resistance and strength can be obtained. .

Claims (1)

(57) [Claims] 1. A binder (II) containing 25 to 60% by weight of an aliphatic conjugated diolefin-based monomer and ethylene per 100 parts by weight of a microcapsule (I) containing an organic solvent in which a colorless or light-colored leuco dye is dissolved. Alkali-insoluble copolymer latex (A) composed of 0.5 to 10% by weight of unsaturated unsaturated carboxylic acid monomer and 30 to 74.5% by weight of another monomer copolymerizable therewith, and weight average molecular weight of 15,000 to 500 , 00
A pressure-sensitive copying paper characterized by containing 5 to 40 parts by weight of an alkali-soluble copolymer latex (B) of 0 in a weight ratio of (A) / (B) = 97-80 / 3-20. Microcapsule coating liquid.