JPH06143802A - Pressure sensitive recording sheet - Google Patents

Abstract

PURPOSE:To enhance the water resistive property of an auto-coloring type pressure sensitive recording sheet by the use of a maleic acid copolymer as a binder of a microcapsule layer and a developer layer. CONSTITUTION:The same surface of a supporter is applied with a layer containing a microcapsule with a developer by the use of the ammonium salt of a maleic acid copolymer and a layer containing a developer to give colors in contact with the color former as a binder in each case. As the maleic acid copolymer, it is preferable to employ a copolymer of maleic acid and styrene, ethylene and isobutylene. In this manner, the whole of a pressure sensitive recording sheet is improved In its water resistive property. Furthermore, the micro capsule wall is preferably made of polyurethaneurea wall film. Thus, a pressure recording sheet capable of withstanding thermal reaction can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-coloring type pressure-sensitive recording sheet, and more particularly to a self-coloring type pressure-sensitive recording sheet in which the water resistance of the coated layer is improved.

[0002]

2. Description of the Related Art A color image is formed by a reaction between an electron-donating or proton-accepting colorless organic compound (hereinafter referred to as a color former) and an electron-accepting or proton-donating compound (hereinafter referred to as a developer). It has been known for a long time, and pressure-sensitive recording sheets, heat-sensitive recording materials and the like have been widely used as concrete applications of this phenomenon.

Generally, a pressure-sensitive recording sheet is a combination of an upper leaf paper in which microcapsules containing a color former are coated on a support such as paper and a lower leaf paper in which a developer is coated on a support such as paper. Or a combination of the above-mentioned upper leaf paper and the above-mentioned lower leaf paper, which is formed by coating microcapsules containing a color-developing agent on one side of a support such as paper and coating the color developer on multiple sides.

When the microcapsule layer and the color developer layer of the pressure-sensitive recording sheet are placed in contact with each other and a writing pressure or a printing pressure is applied, the microcapsule is broken and the color-forming agent in the capsule is destroyed. The color developer reacts to develop color, and a color image is formed for recording.

In addition to the pressure-sensitive recording sheet of the above-mentioned type, two layers of a microcapsule layer containing a color former and a developer layer are provided on the same support such as paper, so-called self-printing. Color-forming pressure-sensitive recording sheets are used for special purposes. For example, if you want to put an ordinary paper on the self-coloring type pressure-sensitive recording sheet and record with a writing instrument, type, etc., and want to leave a copy recorded on the paper etc., put an ink ribbon etc. on this pressure-sensitive recording sheet. When printing directly with a type without using O
Used for recording with CR (the above-mentioned general pressure-sensitive recording sheet is difficult to use due to paper warpage and powder falling, and a combination of ordinary paper and self-coloring type pressure-sensitive recording sheet is used). There is.

When making a plurality of copies using a self-coloring type pressure-sensitive recording sheet, a microcapsule layer containing a color-forming agent is further provided on the back surface of the sheet, and the above-mentioned middle leaf paper and / or lower leaf paper is provided. It is used in combination with paper (the present invention also includes such a self-coloring type pressure-sensitive recording sheet).

[0007]

The binder usually used in the coating layer of a self-coloring type pressure-sensitive recording sheet is PV.
Water-soluble polymers such as A, starch and SBR were used.
Therefore, it has no water resistance, and if water or the like adheres to the coating layer and is rubbed, the coating layer easily peels off. Although there is no practical problem in using it indoors, in recent years, there are many cases in which it is used outdoors, and there are cases where it is exposed to water such as rain, which causes the above problems.

Therefore, an object of the present invention is to provide a self-coloring type pressure sensitive recording sheet in which the water resistance of the coating layer surface of the pressure sensitive recording sheet is improved.

[0009]

The above object of the present invention is to provide a layer containing microcapsules containing a color-forming agent on the same surface of a support, and a layer containing a color-developing agent which develops a color when contacted with the color-forming agent. Achieved by a pressure-sensitive recording sheet characterized by using an ammonium salt of a maleic acid-based copolymer as a binder of each microcapsule layer and a developer layer in a self-coloring type pressure-sensitive recording sheet coated with and We were able to.

That is, the present invention uses an ammonium salt of a maleic acid copolymer in the capsule layer and the developer layer, and the ammonium salt of the maleic acid copolymer acts as a water resistant binder, Improves the water resistance of the pressure-sensitive recording sheet as a whole. Conventionally, a water-soluble binder has been used for a self-coloring type pressure-sensitive recording sheet, but this has been taken into consideration in that it does not lower the color development density, improves manufacturing coating suitability, and has a low raw material cost. Although latex-like materials have been known as water-resistant binders, a large amount must be added in order to make the coating film water-resistant, so that there is a problem in that the color density decreases and the coating agglomerates. there were.

On the other hand, the water-resistant binder of the present invention has sufficient water resistance and does not cause the drawbacks of the conventional known problems such as a decrease in color density and aggregation of the coating liquid. A pressure recording sheet could be obtained. Further, in the present invention, the microcapsule wall is preferably a polyurethane urea wall film, which makes it possible to obtain a pressure-sensitive recording sheet that is resistant to heat fog.

The maleic acid type copolymer is a copolymer obtained from a compound copolymerizable with maleic acid.
In the present invention, examples of the copolymer with maleic acid include styrene, isobutylene, diisobutylene, ethylene, methyl vinyl ether, acrylonitrile, propylene, butadiene and vinyl acetate. Of these, styrene, ethylene and isobutylene are preferable. Most preferred is styrene. The molecular weight is preferably 20,000 to 100,000, particularly preferably 30,000 to 70,000. The degree of esterification is 2
0 to 50% is preferable, and 35 to 50% is particularly preferable.

As the alcohol used for esterification, known alcohols can be appropriately used, but alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol and butyl alcohol are particularly preferable. As an alkaline additive used for neutralizing the copolymer, ammonia is preferable in order to make the film formed of the copolymer water resistant. The neutralization with alkali is used in the range of neutralization degree 0.3 to neutralization degree 1.0 (complete neutralization), and the alkali salt of the copolymer obtained by neutralization is used as a water-soluble resin.

These maleic acid copolymer binders may be used in combination with the conventionally known binders to the extent that water resistance is not deteriorated. The added amount of the maleic acid-based copolymer is preferably 5 to 15%, more preferably 7 to 10% of the solid content of each coating solution. If it is 5% or less, the water resistance of the coating film is inferior, and if it is 15% or more, the color density decreases.

As a conventional binder, polyvinyl alcohol as a water-soluble polymer binder, a combination of carboxy-modified polyvinyl alcohol and a polyamide epoxy resin, methyl cellulose, carboxymethyl cellulose,
Examples thereof include hydroxypropyl cellulose, gum arabic, starch, gelatin, polyvinylpyrrolidone, casein, and styrene / butadiene latex, acrylonitrile / butadiene latex, polyvinyl acetate, polyacrylic acid ester as a latex binder.

In the present invention, as the electron-donating dye (color former), colorless or light-colored triallylmethane type dyes, diphenylmethane type dyes, spiro type dyes, fluorane type dyes and the like which have been conventionally used for pressure sensitive recording sheets are used. Used.
In the present invention, an ultraviolet absorber may be used if necessary.

Regarding the method for producing microcapsules in the present invention, a method utilizing coacervation of hydrophilic colloid sol described in US Pat. Nos. 2,800,457 and 2,800,458, and British Patent 86
7,797, 950,443, 989,264
No. 1,091,076, etc., and the method described in US Pat. No. 3,103,404. As the capsule wall material, a synthetic resin wall material is preferable, and a polyurethane urea-based capsule is particularly preferable.

The polyurethane urea resin wall microcapsule dispersion used in the present invention is obtained by emulsifying and dispersing in a hydrophilic liquid a solution of a polyisocyanate, a polyhydroxy compound and a color former dissolved in a hydrophobic liquid. It is obtained by adding a polyvalent amine to the emulsified dispersion and coating the hydrophobic droplets with a polyurethane urea resin. Both the polyvalent hydroxy compound and the polyvalent amine may be used, or only one of them may be used.

In the present invention, an electron-donating colorless dye may be used alone or in combination with a UV absorber in a solvent (synthetic oil such as alkylated naphthalene, alkylated diphenyl, alkylated diphenylmethane, alkylated terphenyl, and chlorinated parafil: cotton. Oil, vegetable oil such as castor oil: animal oil: mineral oil or a mixture thereof), and after containing it in microcapsules, it is applied to a support such as paper, woodfree paper, plastic sheet, resin coated paper, etc. To do.

In the present invention, the developer layer is provided on the microcapsule layer provided as described above. In addition,
The developer layer may be provided first and the microcapsule layer may be provided thereon, but the former mode is preferred from the viewpoint of preventing ultraviolet rays.

Examples of the color developer used in the present invention include:
Acid clay, activated clay, attapulgite, zeolite,
Examples thereof include clay substances such as bentonite and kaolin, metal salts of aromatic carboxylic acids, phenol formaldehyde resins and the like, but metal salts of aromatic carboxylic acids are preferable. The developer such as a metal salt of an aromatic carboxylic acid used in the present invention is mechanically dispersed in an aqueous system or dissolved in an organic solvent before use.

When mechanically dispersing in an aqueous system, it is treated with a ball mill, attritor, sand grinder or the like and used as a dispersion. Examples of the organic solvent include diisopropylnaphthalene, 1-phenyl-1-xylylethane, 1-phenyl-1-isopropylphenylethane, 1-phenyl-1-ethylphenylethane, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, acetic acid. Examples thereof include ethyl, butyl acetate, amyl acetate, methylene chloride, butanol, paraffin and kerosene.

The metal salt of aromatic carboxylic acid is used by dissolving it in the solvent in an amount of 10 to 200% by weight. The above organic solvent solution is added by 5 to 120% by weight, preferably 50 to 100% by weight, with respect to water containing a dispersant, and emulsified and dispersed. Subsequently, the emulsified dispersion liquid may be heated to remove the organic solvent.

As the dispersant, an ionic or nonionic surfactant or a water-soluble polymer is used. The final amount of the color developer applied to the support is 0.1 g / m ² ~
3.0 g / m ² , preferably 0.2 g / m ^{2 to} 1.0
g / m ² is suitable.

[0025]

【Example】

(Example-1) [Preparation of color-forming agent-containing microcapsule solution] 5.0 g of crystal violet lactone, 1.0 g of benzoyl leuco methylene blue, and 100 g of diisopropylnaphthalene were dissolved as color-forming agents. IP Solvent 1620 (made by Idemitsu Petrochemical Co., Ltd.) as a paraffin solvent in this oily liquid
And 60 g of carbodiimide-modified diphenylmethane diisocyanate (manufactured by Nippon Polyurethane Company, trade name “Millionate MTL”) as polyvalent isocyanate and hexamethylene diisocyanate piuret body (manufactured by Sumitomo Bayer Urethane Co., trade name “Sumijour N32”).
00 ") and 3.0 g of an ethylenediamine butylene oxide adduct (addition mole number of butylene oxide to ethylenediamine: 16.8 mol, molecular weight: 1267) as an alkylene oxide adduct of amine 1
The next solution was prepared.

Next, 1 part of polyvinyl alcohol was added to 140 g of water.
A secondary solution was prepared by dissolving 0 g and 5 g of carboxymethyl cellulose. The second solution was vigorously stirred and the above 1
The next solution was poured to form an oil-in-water emulsion. When the size of the oil droplet reached 5.0μ, weaken the stirring and then add 100 parts of water at 20 ° C to the emulsion.
g, and then tetraethylenepentamine 0.
5 g was added, the temperature of the system was gradually raised to 70 ° C., and this temperature was maintained for 90 minutes.

The capsule liquid thus obtained contains 25
% Styrene-maleic acid copolymer ammonium salt 90
g, and 60 g of starch particles (average particle size 15 μ). Next, water was added to adjust the solid content concentration to 20% to prepare a color-forming agent-containing microcapsule liquid. [Preparation of color developer dispersion] 100 g of 3,5-bis (α-methylbenzyl) salicylate zinc was added to 80 g of xylene and dissolved.

This xylene solution was added to 120 g of a 4% polyvinyl alcohol (PVA-205 Kuraray) aqueous solution, 4 g of a 10% polyoxyethylene sorbitan oleate aqueous solution was further added as a surfactant, and the emulsion was averaged with a homogenizer. An emulsified dispersion was prepared so that the particle size was 1.0 μm. Next, 180 g of water was added to this emulsified dispersion and then heated to remove azeotropically xylene and water from the emulsified dispersion to adjust the solid content concentration to 30% to obtain a developer dispersion. It was [Preparation of developer coating liquid] Calcium carbonate 120 g, zinc oxide 20 g, sodium hexametaphosphate 1 g and water 20
Using 0 g, an inorganic pigment dispersion liquid obtained by atomizing with a sand mill was obtained.

5% PVA was added to 300 g of this inorganic pigment dispersion.
-117 (manufactured by Kuraray) aqueous solution 50 g and 25% styrene-maleic acid copolymer ammonium salt (Polymaron 38
5) 50 g was added, and further 15 g of the above-mentioned color developer dispersion was added and water was prepared so that the solid content concentration was 20% to obtain a color developer coating solution. [Preparation of self-coloring type pressure-sensitive recording sheet] 5.0 g of a microcapsule liquid containing a color former on one side of a 40 g / m ² base paper
/ M ² of solid content is applied with a coating bar and dried, and then a developer coating solution of 6.0 g / m ^{2 is applied.}
Was coated with a coating bar to obtain a solid content of and dried to obtain a self-coloring type pressure-sensitive recording sheet. (Example-2) Recording was carried out in the same manner as in Example-1 except that an ammonium salt of an ethylene-maleic acid copolymer was used instead of the ammonium salt of a styrene-maleic acid copolymer used in Example-1. Got the sheet. (Example-3) Recording was carried out in the same manner as in Example-1, except that an ammonium salt of isobutylene-maleic acid copolymer was used instead of the ammonium salt of styrene-maleic acid copolymer used in Example-1. Got the sheet. (Comparative Example-1) Styrene added to each layer in Example-1
A recording sheet was obtained in the same manner as in Example 1 except that the same amount of polyvinyl alcohol (Kuraray PVA117) was added in solid content instead of the ammonium salt of the maleic acid copolymer. (Comparative Example-2) Styrene added to each layer in Example-1
A recording sheet was obtained in the same manner as in Example 1 except that sodium hydroxide was used instead of the ammonium salt of the maleic acid copolymer, and the sodium salt of the styrene-maleic acid copolymer was added. (Comparative Example-3) Styrene added to each layer in Example-1
Example-except that SBR latex was added in an amount of 30 g in terms of solid content instead of the ammonium salt of the maleic acid copolymer-
A recording sheet was obtained in the same manner as in 1.

[Water resistance test] The self-coloring type pressure-sensitive recording sheet was immersed in water for 3 days and taken out, and then the coating layer surface was rubbed with a finger three times in a wet state to test whether the coating film peeled off.
The results are shown in Table 1.

[0031]

[Table 1]

From the above results, it can be seen that the present invention is a recording sheet excellent in water resistance and color density.

[0033]

INDUSTRIAL APPLICABILITY According to the present invention, by using the ammonium salt of the maleic acid type copolymer as the water resistant binder, a water resistant pressure sensitive recording sheet can be obtained without impairing the color density.

Claims (2)

[Claims] 1. A self-coloring type sensation in which a layer containing microcapsules containing a color-forming agent and a layer containing a color-developing agent that develops color by contacting with the color-forming agent are coated on the same surface of a support. A pressure-sensitive recording sheet, wherein an ammonium salt of a maleic acid-based copolymer is used as a binder of each microcapsule layer and a developer layer in the pressure-sensitive recording sheet. 2. The pressure-sensitive recording sheet according to claim 1, wherein the microcapsule wall is a polyurethane urea wall film.