JPS5833116B2 - Self-coloring pressure-sensitive recording paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel structure of 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). If you place both cloth sides facing each other and apply pressure by writing or printing with a typewriter, you can obtain the desired copy record on the developer coated side. It is publicly known and for public use.

In addition, self-coloring pressure-sensitive recording paper, which is formed by coating a layer of color former-containing microcapsules and a layer of a color developer twice on the same side of a sheet-like support, is also publicly available and does not require a type ribbon. It has unique usefulness, such as being able to obtain a copy record by printing or writing or printing on plain paper, and the demand for it has increased in recent years.

For self-coloring pressure-sensitive recording paper, a method improved from a smearing machine has been proposed, as described in JP-A-47-6207, because it requires two coats.

Further, Japanese Patent Publication No. 47-16096 describes a single-layer type self-coloring pressure-sensitive recording paper using liquid smearing.

This method can be said to be an excellent method for self-fogging (staining), but because the capsule membrane material is a hydrophilic film-forming polymer material impregnated with phenol-aldehyde resin, yellowing due to it is a problem. The present inventors have confirmed that it has the disadvantage that it is difficult to produce because it is intensely colored and darkly colored.

Furthermore, JP-A-50-6413 describes a method of adding amines to prevent self-fogging (staining).
Although this method is somewhat effective, it has the drawback that color development is inhibited if an amount of amine is added that completely blocks the fog, and the paper surface tends to yellow.

Japanese Patent Publication No. 47-10780 describes the method of printing, but unlike paper that is smeared on the surface, color development occurs within the paper, so it has drawbacks such as insufficient density.

In order to further improve the color cast, JP-A-49-377
As shown in No. 10, an attempt has been made to create a self-coloring pressure-sensitive recording paper using a liquid by examining encapsulation.

The color cast can be improved depending on the film material and method of making the capsule, but in order to completely eliminate the color cast, it is necessary to
In particular, the capsule membrane must be made thick, which has the drawback of deteriorating the original color development.

Furthermore, since the phenol resin, salicylic acid derivative, or its metal salt, which is an oil-soluble color developer, has active hydrogen, it reacts with the isocyanate compound, etc., which is the raw material for the membrane, so it is difficult to encapsulate it using this method. It is.

The present invention shows the structure of a new self-coloring type pressure-sensitive recording paper, and provides a single-layer type self-coloring type pressure-sensitive recording paper that is free from coloring fog and has excellent coloring properties.

The coating layer of the present invention is made by mixing and coating at least the following five components.

That is, (1) a colorless dye which is a color former; (2) a phenol resin or a salicylic acid derivative or a metal salt thereof which is a color developer; (2) starch particles; (2) a pigment; (2) an adhesive;

In order to prevent color fog and improve color development, at least one of the color former and the color developer must be encapsulated in liquid form.

Except when using a phenol resin (color developer) that is liquid at room temperature, the color forming agent or color developer is usually dissolved (or dispersed) in a high-boiling oil substance before use.

In this case, a known electron-donating leuco dye is used as a coloring agent.

Representative examples include crystal violet lactone and cruolan derivatives.

Typical color developers include substituted phenol-formalin resins described in Japanese Patent Publication No. 42-20144 and polyvalent metal salts of salicylic acid derivatives described in Japanese Patent Publication No. 51-25174.
Preferred specific examples include p-phenylphenol formalin resin, 3,5-di-tert-butylsalicylic acid or its zinc salt, and 3,5-di(dimethylbenzyl)salicylic acid or its zinc salt.

The high-boiling point oily substances that are used together with these oils include 5AS (manufactured by Nippon Petrochemical Co., Ltd., diarylethane type) and KMC (manufactured by Kureha Chemical Co., Ltd., dialkylnaphthalene type), which are known as ordinary carbonless paper oils. If necessary, known ester or aliphatic oils may be mixed.

The properties of the capsule membrane are particularly important when producing self-coloring pressure-sensitive recording paper with a liquid, and at least one of the capsules must be substantially encapsulated with a membrane material made of melamine-formalin resin. desirable.

Capsules produced by the coacervation method of gelatin and capsules produced by the interfacial polymerization method using polyamide, which have been put into practical use or under consideration, have not been able to produce good self-coloring pressure-sensitive recording paper, perhaps because the properties of the capsule membrane are insufficient. do not have.

I don't know why only melamine/formalin resin is better, but I think it's because it has a dense membrane and is highly water resistant, so it holds the contents of the capsule inside during the smearing process.

These encapsulations are disclosed in Japanese Patent Application Laid-Open No. 53-84881 or Japanese Patent Application No. 116249-1983, filed by the same applicant as the present application.
Patent application No. 53-89159, Patent application No. 120906-1983
It is obtained by the In 5itu method detailed by No.

In particular, when a styrene-maleic anhydride copolymer is used as an emulsifier, the stability of particle size and the heat resistance of the capsule membrane are excellent.

The present invention is also characterized by the amount of starch particles used.

That is, for the capsule (solid content) used, 1.
It requires 5 times more starch particles (weight ratio).

It has been known for some time that starch particles can be used in carbonless paper (Japanese Patent Publication No. 47-1178, Special Publication No. 47-1178,
8-33204), these are.

At most 5 capsules on the capsule side of the top paper and middle paper.
It was described that about 0 φ should be added, but in the case of such a self-coloring sheet, a good coloring sheet cannot be obtained with about 50 φ, and the coloring is easily smeared and other papers are stained.

The starch particles are suitably about 10 to 30 microns in size.

Regarding pigments, conventionally known clays, kaolin,
Calcined clay, calcium carbonate, titanium oxide, zinc oxide,
Plastic pigments are used based on conventional techniques.

It is used to improve paper whiteness, printability, and color development, so the amount used varies depending on the type of pigment, but 10 capsules
It is preferably about 10 to ioo parts to 0 parts.

As the adhesive, commonly used hydroxyethyl cellulose, (modified) starch, carboxymethyl cellulose, acrylic latex, SBR latex, polyvinyl alcohol, etc. can be used.

As mentioned above, self-coloring pressure-sensitive recording paper uses a sheet-like support (
In the past, multilayer type products were common, in which a layer of color former-containing microcapsules and a layer of color developer were coated twice on the same surface of paper, film, etc., but recently, microcapsule technology has been developed. With advances, microcapsules with less leakage of capsule core substances have become available, and a color former and/or color developer is encapsulated in microcapsules and mixed to form a single liquid, which is then applied in a single layer. This led to attempts to obtain self-coloring pressure-sensitive recording paper.

However, according to the research conducted by the present inventors, it was only when both the color forming agent and the color developer were microencapsulated, and when the method of microencapsulating the color developer was limited to a specific method, that it was put to practical use. Only a self-coloring pressure-sensitive recording paper with a sufficiently white background was obtained.

It has been found that the microcapsules made of the melamine-formalin resin film used in the present invention are perfectly suited for use as color developer microcapsules in these two-capsule type single-layer coated self-coloring pressure-sensitive recording papers. However, in addition, one capsule type single-layer coated self-coloring pressure-sensitive recording paper in which only one of the color forming agent and the color developer is microencapsulated, especially when only the color developer is encapsulated. It was discovered that this capsule is optimal and unique, leading to the present invention.

In other words, when trying to manufacture self-coloring pressure-sensitive recording paper, a single-layer coating type and one-capsule type is ideal not only from the economical point of view of manufacturing, but also from the viewpoint of quality, especially in terms of quick color development speed. Although everyone agrees that this is a goal, it has not been realized until now because a sufficient microencapsulation method has not been developed.

For example, if gelatin-based capsules produced by the complex coacervation method are used, the entire coated surface becomes colored.

When microcapsules made of urea-formalin resin as a membrane material, such as those described in JP-A-51-9079, are used, a white background can be obtained, but colored spots are observed and the product value is lost.

The microencapsulation method using a polyvalent incyanate compound as a prepolymer reacts with compounds having active water atoms such as -OH\NH and -COOH, so it is difficult to use these as the core material.

However, the present inventors have discovered the new and important fact that by using microcapsules made of melamine-formalin resin as a membrane material, it is possible to manufacture single-layer coated capsules for the first time.

These facts will be specifically described in Examples.

In the structure of the present invention, other additives such as ultraviolet absorbers, antioxidants, dispersants, waterproofing agents, lubricants, antifoaming agents, etc. can be used based on conventional techniques, and can be used in the coating process. Regarding the method, known methods such as air knife coating, roll coating, and blade coating can be used.

This will be explained below using examples.

Example 1 [Color developer capsule] 40 parts of paraphenylphenol (m, p 86°C, PR26142 manufactured by Sumitomo Juretsu) was mixed with Hysol 5ASN-2.
96 (oil manufactured by Nippon Petrochemicals) was heated and dissolved to obtain 100 parts of internal phase oil.

The internal phase oil was emulsified in 200 parts of a styrene-maleic anhydride copolymer aqueous solution adjusted to pH 5.3.

A melamine-formalin initial condensate prepared by adjusting 20 parts of melamine and 45 parts of 37% formalin to pH 8.5 with caustic soda and heating to 80'C was added to the above emulsion, the temperature of the system was set to 70°C, and the reaction was carried out for 1 hour. to obtain developer capsules.

The average particle size was 5.2μ.

Example 2 [Capsule of color developer] 3.5-tert-butylsalicylic acid zinc salt, 2
Encapsulation was carried out in the same manner as in Example 1 using 40 parts of KMC-113 (Kureha Chemical Oil) and 40 parts of a high-boiling aliphatic hydrocarbon oil (Ink Solvent No. 3) as internal phase oils.

Example 3 [Color former capsule] Crystal violet lactone 5 parts, KMC-11
Using 395 parts as internal phase oil, encapsulation was carried out in the same manner as in Example 1 to obtain color former capsules.

The average particle size was 4μ.

Example 4 Solid content (including water) Capsules of Example 1 100 parts (color developer) CVL20 dispersion 4 parts (20 parts) (color former) Wheat starch granules 200 parts Calcium carbonate 30 parts 10% PVA aqueous solution 20 (200 parts) were mixed well to form a single liquid, and applied to paper with a metering bar.
A one-capsule single-layer self-coloring sheet was created.

The smear volume was 69/vl. CVL20% above
The dispersion liquid is obtained by finely pulverizing CVL crystals and dispersing them in water, and the CVL remains solid (powder) and is not microencapsulated.

Here, a self-coloring sheet with good whiteness and no coloring stains was created.

When type-printed, a clear blue color was obtained.

Example 5 Solid content (including water) Capsules of Example 1 50 parts (color developer) Capsules of Example 3 50 parts (color former) Wheat starch granules 250 parts Kaolin clay 30 parts Oxidized starch 25 Aqueous solution 50 parts ( 7.5 fl/m” (solids) on high-quality paper with a formulation of 200 parts)
A two-capsule single-layer self-coloring sheet was created by smearing with an air knife coater.

A white self-coloring pressure-sensitive recording sheet free from color stains was obtained.

When type-printed, a bright deep blue color appeared instantly.

In this way, the new fact was confirmed that by encapsulating with a membrane material made of melamine-formalin resin, it is possible to produce not only two-capsule single-layer type but also one-capsule single-layer type self-coloring pressure-sensitive recording paper. .

Claims (1)

[Scope of Claims] 1 ■Colorless dye as a color former ■Phenol resin or salicylic acid derivative or its metal salt as a color developer ■Starch particles ■Pigment and ■Adhesive mixed and coated with a -liquid. In the single-layer type self-coloring pressure-sensitive recording paper, at least one of the color forming agent and color developer is liquid and dissolved in a hydrophobic solvent in an acidic aqueous solution of styrene maleic anhydride copolymer. After dispersing or emulsifying a colorless dye or color developer solution into discontinuous microparticles, melamine
It is encapsulated with a membrane material made of melamine/formalin resin obtained by adding a formalin initial condensate and reacting under acidic heating, and has a content of 150% based on the capsule (solid content).
A self-coloring pressure-sensitive recording paper characterized by using starch particles having a weight ratio of 1. 2. The self-coloring pressure-sensitive recording paper according to claim 1, wherein (1) the color forming agent is solid or powder, and (2) the color developer is liquid and encapsulated with a melamine/formalin resin. 3. The self-coloring pressure-sensitive recording paper according to claim 1, wherein (1) the color former and (2) the color developer are both encapsulated with a melamine/formalin resin.