JPS58128892A - Ink composition for producing self-coloring pressure- sensitive recording paper - Google Patents

Abstract

PURPOSE:To provide the titled ink composition which is economical and applicable to only a desired part and which facilitates printing with high quality, comprising an ink composition of a color former and a color developer which are microencapsulated with a specified rsin film, particulate silicic acid, an adhesive and an alcohol base dispersion medium. CONSTITUTION:The objective composition is of a single-layer type and consists essentially of (A) a colorless dye (e.g., leuco dye) as a color former, (B) a phenolic resin or a salicyclic acid derivative (or a metallic salt thereof) (e.g., p- phenylphenol-formaldehyde resin, 3,5-di-tert-butylsalicylic acid or zinc salt thereof) as a color developer, (C) particulate silicic acid as a pigment, (D) an adhesive (preferably, partially saponifiedd polyvinyl alcohol) and (E) an alcohol base dispersion medium, wherein components A and B are microcapsulated with a film material of a melamine-formaldehyde resin. The quantity of component C to be added is 10-100pts.wt., preferably 20-60pts.wt. per 100pts.wt. (dry basis, in total) of microcapsules.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ink composition for producing self-coloring pressure-sensitive recording paper.

Pressure-sensitive recording paper usually consists of an upper paper coated with microcapsules containing a colorless dye, which is a color former, and an acidic substance, which is a color developer (e.g., activated clay, phenolic resin, salicylic acid derivatives or metal salts thereof). It is well known and used in combination with the lower paper, for writing with both coated surfaces facing each other, or as a tie-bra.

Furthermore, a self-coloring pressure-sensitive recording paper in which a color forming agent-containing microcapsule and a color developer or a color developer-containing microcapsule are coated in one or two layers on the same side of a sheet-like support is also disclosed in Japanese Patent Application Laid-Open No. 49 -37710, JP-A-55-12
No. 8492, etc., and is already publicly known. However, conventional self-coloring pressure-sensitive recording paper coats the entire surface with a water-based coating solution, so ink called desensitizing ink is applied to areas where it is not desired to develop color due to pressure, such as letterpress, offset, flexography, etc. The printing method was used to print, but since the color former and developer are both present on the same side of the support, the desensitization effect is lower than when printing on the developer-coated side of ordinary carbonless paper. Unfortunately, it was necessary to increase the amount of desensitizing ink applied, and as a result, the ink drying properties in the printing section were poor, which often caused problems.0 Also, for printing companies, it was difficult to use expensive self-coloring pressure-sensitive recording paper. Purchasing and then performing desensitized printing is extremely wasteful, time-consuming, and involves high-cost slips, which is extremely uneconomical.

Therefore, the present inventor aimed to develop an ink composition that would enable the production of self-coloring pressure-sensitive recording paper by partially printing only the areas desired to be colored by pressure on a support such as high-quality paper. We have considered this. As a result, we created a flexo ink whose main composition is: ■ Microcapsules made of a melamine/formalin resin film containing a color former; ■ Microcapsules made of a melamine/formalin resin film containing a color developer; ■ Finely divided silicic acid; ■ Adhesive; and ■ Alcohol-based dispersion medium. It has been found that the above object can be achieved by the composition.

The reason for choosing the flexographic printing method is that the microcapsules used in the ink composition are compatible with letterpress or lithographic printing, which has a strong printing pressure.
This is because microcapsules are destroyed by pressure in the offset printing method, whereas no destruction of the microcapsules was observed in the flexographic printing method, where the printing pressure is relatively weak.

The alcoholic dispersion medium (2) is a dispersion medium mainly composed of methanol, ethanol, and (iso)furobyl alcohol, but it can also be used in a mixed system with water or other organic solvents. However, if the proportion of water in the solvent is high, a large amount of drying energy is required and it also causes wrinkles in the paper. The alcohol content must be 50% or more.

Therefore, the microcapsules may be prepared and used in the form of an aqueous dispersion with a high solid content, but it is also possible to use microcapsules made into powder by, for example, a spray drying method.

In addition, the reason why we use melamine-formalin resin as the microcapsule membrane material for the color former and color developer is that melamine and formalin resin membrane microcapsules have particularly strong alcohol resistance, and have traditionally been used in carbonless paper. In the gelatin-based microcapsules used,
This is extremely inconvenient as the internal phase is extracted with alcohol, causing a color cast.

n Microencapsulation is the kg 5 itu method, which is described in, for example, JP-A No. 54-49984, etc., but in summary, the acidic method of maleic anhydride copolymers such as ethylene maleic anhydride, styrene maleic anhydride, etc. Encapsulation by dispersing and emulsifying a hydrophobic substance to become the internal phase substance of microcapsules in an aqueous solution, adding an initial polymer of melamine-formalin to the emulsion, and precipitating the melamine-formalin polymer as a microcapsule film under acidic and heated conditions. In particular, excellent microcapsules can be obtained by using styrene and maleic anhydride copolymers as emulsifiers and performing microcapsules under heating conditions of 65° C. or higher, particularly preferably 70° C. or higher.

As the color former, a known electron-donating dye for pressure-sensitive paper, such as a leuco dye, is used.

Representative examples include crystal violet lactone and fluoran derivatives. As a color developer, Special Publication No. 42-20
Substituted phenol-formalin resin described in No. 144
The salicylic acid derivative polyvalent metal salt described in No. 1-25174 is a typical example, and preferred specific examples include P-phenylphenol formalin resin, 3,5-tar
Examples include t-butylsalicylic acid or its zinc salt, and 3,5-di(dimethylbenzyl)salicylic acid or its zinc salt.

The capsule inner phase oil that dissolves these color formers and color developers is SAS [diarylethane type manufactured by Nippon Petrochemical Co., Ltd.]
Aromatic hydrocarbons such as TKM (:! [manufactured by Kureha Kagaku ■, dialkylnaphthalene type]) can be used, and if necessary, known ester or aliphatic oils may be used in combination.

The finely divided silicic acid used as a pigment in the present invention is an inorganic white pigment with a secondary agglomerated average particle size of about 2 to 10 μm.
Compared to the white pigment used in self-coloring pressure-sensitive recording paper, which had an oil absorption of less than 100d/100g, the oil absorption is approximately 200d/100.9 or more. It is characterized by a large . The effect of adding fine silicic acid is that it can significantly improve the color density and initial color development speed compared to inorganic white pigments such as clay, kaolin, and calcium carbonate.This is because fine silicic acid destroys microcapsules at the same time. It is thought that this is because it absorbs the dye-containing oil and the color developer-containing oil contained therein, and efficiently helps the contact reaction between the dye and the color developer, that is, color development.

The amount of finely divided silicic acid added is microcapsules (dry total) 10
10 to 100 parts, preferably 20 to 60 parts by weight
Department.

Furthermore, since the specific gravity is relatively small and the ink is well dispersed in an alcohol-based dispersion medium, an ink with excellent stability with little precipitation and high whiteness can be obtained.

As adhesives, various cellulose derivatives, vinyl acetate derivatives, maleic acid resins, ethylene-acrylics, styrene-modified acrylics, shellac, etc. can be used, but those with saponification degree of 40 are particularly preferred from the viewpoint of coloring properties and ink stability. -95 mole partially saponified polyvinyl alcohol.

The amount of adhesive used is 10 microcapsules (dry total)
0 parts, 30 to 300 parts, preferably 100 to 2 parts
It is 00 copies.

Other additives include starch particle cellulose powder with an average particle size of about 10 to 30μ, wax fine particle dispersion, etc. as a capsule protectant, dispersants, antifoaming agents, ultraviolet absorbers, antioxidants, and fluorescent dyes. , etc. can be added. In addition, it is also possible to use a white inorganic pigment in combination, if necessary.

Hereinafter, the present invention will be specifically explained using examples, but the invention is not limited to the examples. Note that "parts" refers to parts by weight.

Example 10 Color former capsule 15 parts of crystal violet lactone mixed with 5 parts of Hysol
The mixture was heated and dissolved in 85 parts of ASN-296 (oil manufactured by Nippon Petrochemicals) to obtain 100 parts of internal phase oil.

Suflipset 520 (manufactured by Monsando, styrene-maleic anhydride copolymer) was emulsified in 100 parts of an aqueous solution of pH 5.5 in which a small amount of sodium hydroxide was dissolved.

Add 7 parts of melamine and 18 parts of 37-formalin to 30 parts of water, adjust the pH to 9 with sodium hydroxide, heat at 80°C for 15 minutes to obtain a melamine-formalin initial condensate, and add this to the emulsion, By stirring the mixture at a liquid temperature of 75° C. for 3 hours, color former-containing microcapsules were obtained. The average particle size was 5 pμ.

Example 2. Color developer capsule PPI' resin <manufactured by Sumitomo Teeretstsu, No (raphenylluphenol-formalin resin) 41t No Isol S
The mixture was heated and dissolved in 660 parts of AI N-29 to obtain 100 parts of the internal phase. This was encapsulated in the same manner as in Example 1 to obtain color developer capsules with an average particle size of 4.5μ. Coloring agent capsule 80 parts (solid content) Modified vinyl acetate derivative [Cohonyl PK-40゜Nippon Gosei ■] 150 parts (solid content) Special wheat starch
A pigment-free flexographic ink-A was prepared by uniformly mixing 200 parts methanol and 280 parts or more.

Example 4゜Fine powder silicic acid [Syroid 244 Fuji Davison Chemical ■] in the flexo ink-A of Example 3
40 parts were uniformly mixed to form a flexographic ink.

Example 5゜Flexo ink A of Example 3 with fine powder silicic acid [Mizukasil p-801N Mizusawa Chemical Industry ■]
40 parts were uniformly mixed to make a flexo ink.0Comparative Example 1゜Flexo ink A of Example 3 Active clay [Jilton A, Mizusawa Kagaku ■] Calcium carbonate [Brilliant-15゜Shiraishi Kogyo ■] Titanium oxide [ Tybake 0R-80, Ishihara Sangyo ■] 40 parts of each aluminum oxide [reagent special grade, Wako Tsumugi ■] were mixed to prepare four types of flexographic inks.

Comparative Example 2゜Inner phase oil 10 in which the same coloring agent as in Example 1 was dissolved in the same ratio
0 part was added to 100 parts of a 10% acid gelatin aqueous solution whose pH was adjusted to 9 to obtain color former-containing microcapsules by the gelatin coacervate method. -Also, Example 2
A developer-containing microcapsule was obtained using the gelatin coacervate method using 100 parts of the internal phase oil in which the same developer was dissolved in the same ratio as in Example 3, and a pigment-free flexible ink was created with the same composition ratio as in Example 3. The flexo ink was unusable due to bluing caused by insufficient micro-encapsulation of the agent and the extraction of the color former and developer from the microcapsules by methanol.

Example 6: The flexographic inks obtained in Examples 3 to 5 and Comparative Example 1 were diluted with methanol and printed on high-quality paper with a basis weight of 50 g/+++ using a foam printing machine to give an ink coverage of approximately 51 i'' in terms of solid content. 7
A spot-printed self-coloring pressure-sensitive paper was prepared by printing in a size of m. Furthermore, the printed surface of the printed paper has a basis weight of 40
11/m' of high-quality paper is stacked on top of each other, and a linear pressure of 100 kt is applied.
r/ctn (passed through a test super calendar under D conditions, and measured the color density (reflectance of the colored area) of the printed area after 1 hour using a color difference meter ND-101D manufactured by Japanese Army Color ■.
It was calculated using the following formula.

The smaller the number, the higher the color density.

Chi

Claims (1)

[Claims] 1. Basically: ■Colorless dye as a color former ■Phenol resin or salicylic acid derivative or its metal salt as a color developer ■Pigment ■Adhesive and ■Single-layer type self-coloring pressure-sensitive recording consisting of ■alcoholic dispersion medium A self-coloring ink composition for paper manufacturing, characterized in that (1) the color forming agent and (2) the color developer are microencapsulated with a membrane material made of melamine-formalin resin, and (2) the pigment is finely powdered silicic acid. Ink composition for manufacturing type pressure-sensitive recording paper 0