JPS61217281A - Color developer sheet for image-recording material - Google Patents

Abstract

PURPOSE:To enhance smoothness of a color developer sheet, prevent smudging and obtain a color developer sheet for an image-recording material having excellent printability, by incorporating an inorganic color developer and an acrylic latex into a coated layer. CONSTITUTION:The color developer sheet comprises an electron-donative colorless dye and an electron-acceptive color developer. The coated layer comprises a semisynthetic solid acid as an inorganic color developer and an acrylic latex as a binder. The inorganic color developer is derived from a clay mineral having a lamellar structure constituted of regular tetrahedrons of silica, and shows an electron diffraction pattern characteristic of crystals having said lamellar structure. the latex has a minimum film-forming temperature of not higher than +45 deg.C. Accordingly, the color developer sheet has high smoothness, possibility of smudging becomes extremely low, while developed color density is high, and the density is not lowered under a high-humidity condition.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a color developing sheet for image recording materials;
・More specifically, we use electron-donating colorless dyes and electron-accepting color developers, especially activated clays represented by acid clay, activated clay, etc., or clay minerals with a layered structure consisting of regular tetrahedrons of silica. According to electron beam diffraction, it shows a diffraction pattern based on a crystal with a layered structure consisting of regular tetrahedrons of the silica, but according to X-ray diffraction, the entire diffraction pattern based on a crystal with the above structure is substantially A color developing sheet for an image recording material using an image recording material not shown in , and consisting of an inorganic color developer such as a semi-synthetic solid acid containing at least silicon and magnesium and/or aluminum as an element other than oxygen. be.

(I3) Prior art As is well known, image recording materials that utilize a color reaction caused by a combination of an electron-donating colorless (leuco) dye and an electron-accepting color developer are disclosed in, for example, U.S. Pat.
There are carbonless pressure-sensitive recording materials such as those described in the specifications of No. 0471, No. 2730456, No. 3418250, etc., and this has a long history and is also a large chestnut.
However, there are other image recording materials that fully utilize this coloring principle, such as thermal sublimation colorless (leuco).
Dye thermochromic image recording materials (JP-A-52-149123, JP-A-54-53538, etc.), □゛thermal thermal transfer color image recording materials, etc. are available.

Carbonless pressure-sensitive recording materials basically consist of a colorless (leuco) dye donor sheet (upper paper) and a color developer sheet (lower paper).
(In addition to this, there are also applied products such as inner paper and self-contained paper.) Colorless (leuco) dyes are often dissolved in high boiling point solvents and incorporated into microcapsules.

Conventionally, microencapsulation has been carried out using the core cell pageron method,
It is carried out by in-situ polymerization method, interfacial polymerization method, etc. Colorless (leuco) dyes include crystal violet lactone, 3@3.bis(P-dimethylaminophenyl) natutalide, 3-(P-dimethylaminophenyl)- 3-(2-methylindol-3-yl)-6-
Triallylmethane phthalide series such as dimethyl minophthalide and acyl conducting systems such as benzoyl, dinizoyl, and piparoyl of methylene blue; 3-diethyl minino-6-methyl-7-chlorofluorane, 3-diethylamino-7- Dibenzylaminofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-methyl-cyclohexylamino-6-methyl-7-anilinofluorane, 3-ethyl-P-1lylamino-6-methyl There are xanthine phthalide series such as -7-anilinofluorane and other leuco dyes.

High-boiling point solvents often used in carbonless pressure-sensitive recording materials include alkylnaphthalenes represented by diisogropylnaphthalene, diallylalkane represented by 1-phenyl-1-xylylethane, and inglobylpiphenyl. Aromatic hydrocarbons such as alkyl biphenyls, other triallyl dimethanes, alkylbenzenes, benzylnaphthalenes, sialyl alkylenes, and allyl indanes; carboxylic acid ester compounds represented by diptyl phthalate, dioctyl maleate, etc. ; Phosphoric ester compounds represented by tricresyl phosphate; Naturally produced animal and vegetable oils and fats such as castor oil, soybean oil, cottonseed oil, and whale oil, or their modified products; High-boiling distillates of natural products such as mineral oil (
(consisting of aliphatic hydrocarbons).

The electron-accepting color developer is an inorganic color developer using natural clay minerals such as acid clay and attapulgite clay: acid clay, which is a montmorillonite clay mineral, is mixed with hydrochloric acid and nitric acid. Activated clay treated to a moderate or high degree with inorganic acids such as sulfuric acid, various phenolic compounds, novolak type phenolic resins, aromatic carboxylic acids or their polyvalent metal salts are already available as organic color developers. proposed and used.

Among these color developers, novolac deaf phenolic resin, an organic color developer, and substituted salicylic acid (salt), an aromatic carboxylic acid, are used in containers filled with natural or synthetic mineral fine sand, hard glass fine particles, metal fine particles, etc. It is wet milled in an aqueous system using a so-called ball mill or sand mill to a particle size of 1 to 4 microns or less, and prepared with pigments such as clay, kaolin, and calcium carbonate, and binders such as starch, dextrin, carboxymethylcellulose, and polyvinyl alcohol. The color developing sheet, which is made by applying a coating liquid applied to a sheet support, has good smoothness, high color density, and excellent sunlight resistance of the color image, but the color development speed is slow, and the color image is glassy. The color will fade if it comes into contact with plasticizers or oils.

Moreover, the printing suitability of the ink set and the like is poor, and since it is an organic chemically synthesized product, the cost is high.

On the other hand, inorganic colorants have excellent printability such as ink setting properties and are low in cost, making them attractive as industrial materials, but the developer sheet has poor smoothness and is prone to smudging. There is a drawback. One of the reasons for this is that the particle size of the inorganic color developer is large. Activated clay, which is a type of inorganic color developer, is disclosed in Japanese Patent Publication Nos. 41-2373 and 4.
As described in No. 1-7622 and No. 42-8811, acid clay or similar clays are treated with mineral acids to produce acid-soluble aluminum, iron, sodium,
Generally used is one in which zinc and other basic components are eluted, washed with water, dried, and then dry-pulverized, and the particle size of 10 microns or less is 80% by weight or more and the particle size of 1 micron or less is about 15% by weight or less.

Conventionally, in order to improve color development ability and smoothness, the particle size of the inorganic color developer has been made finer, with 100% by weight of 5 microns or less, but the specific surface area is also 200rr? /f, which increases the viscosity during preparation of the coating liquid, and unless the amount of binder is increased, the blanket of the printing press will be stained, making it impractical.

Further, even if a large amount of anti-dusting agent such as calcium stearate is added, the effect is small. Furthermore, if you try to increase the smoothness by applying strong pressure with a color developing sheet (k machine calendar, etc.), the pulp fibers of the sheet will be destroyed, opacity will be lost, whiteness will decrease, and printing suitability such as ink setting will be affected. It was found that if the quality of the product is poor, the product value will be greatly reduced.

(C1 Purpose of the Invention The purpose of the present invention is to improve the smoothness of a color developer sheet using an inorganic color developer, eliminate stains (smudges), and obtain a color developer sheet for image recording materials that has excellent printability. There is a particular thing.

Among the inorganic colorants used in the present invention, the color developers recommended are JP-A-57-15996 and JP-A-58-1688.
This is a semi-synthetic solid acid whose production method was proposed in Publication No. 5. This is done by preparing a clay mineral having an I-layer structure consisting of regular tetrahedrons of silica such that the S i O2 content is 82 to 96.5% by weight on a dry basis (drying at 105°C for 3 hours), preferably 85 to 95% by weight. acid treatment and the resulting clay mineral is contacted in an aqueous medium with a compound of magnesium and/or aluminum that is at least partially soluble in said medium, and if this soluble compound is other than a hydroxide, the hydroxide. This is a new type of inorganic color developer produced by neutralizing with an alkali or acid to form a mineral, completely introducing magnesium and/or aluminum components into the acid-treated clay mineral, and optionally drying. In the present invention, this will be referred to as a semi-synthetic solid acid. That is, the production method is also new, and the acid-treated clay mineral is
When measured by line diffraction or electron beam diffraction, the clay mineral has a structure that substantially does not exhibit a diffraction pattern based on the crystal layer structure of regular tetrahedrons of silica that the clay mineral has before acid treatment. Specifically, by completely introducing magnesium and/or aluminum components into this acid-treated clay mineral as described above, electron beam diffraction shows a diffraction pattern based on crystals with a layered structure consisting of regular tetrahedrons of the silica.
The color developer contains at least silicon, magnesium and/or -aluminum as elements other than oxygen, and exhibits a diffraction pattern based on crystals having the layered structure according to line diffraction.

This semi-synthetic solid acid completely solves the drawbacks of conventional clay mineral complexion agents such as acid clay and activated clay, which are the insufficient color density and the decrease in the density of colored images under high humidity. It is a new type of blood-tinting agent that can

Here, the present inventors have found that when a color developer sheet is manufactured by preparing a coating liquid with an inorganic color developer, especially a semi-synthetic solid acid, which is a new type of blood coloring agent manufactured as described above, the color density is certainly high. Although the decrease in density of colored images under high humidity has been improved, on the other hand, it has been found that conventional activated clay tends to have this tendency, but has poor smoothness and is prone to staining (smudges). .

(D+ Structure of the Invention The present inventors conducted extensive research on semi-synthetic solid acids, which are a type of inorganic color developer, and found that semi-synthetic solid acids, which are color developers, and acrylic, which is a binder, The present invention has been achieved by creating a color developing sheet for image recording materials with a coating layer containing a latex.The color developing sheet of the present invention has high smoothness, very little staining (smudges),
However, the color density is high, the density of the color image decreases rapidly under high humidity, the color image does not disappear due to plasticizers or oils, and the surface strength of the color developer sheet (I
GT Pick) is also strong and has excellent printability, making it possible to obtain practically high-quality products.

Acrylic latex, which is the binder used in the present invention, is originally a copolymer of acrylic ester and methacrylic ester, but recently the film forming temperature (MFT: Min
imum Film Forming Tempera
In order to achieve a balance of performance such as smoothness and binding strength at +45°C or lower, methyl methacrylate and/or styrene as a hard monomer component and ethyl acrylate, butyl acrylate, 2- as a soft monomer component.
It is a copolymer latex consisting of one or more types selected from ethylhexyl acrylate.

The structure of the acrylic latex of the present invention is a general copolymer in which the units of two types of monomers are irregularly distributed in a continuous manner, or an alternating copolymer in which the units of the two monomers are regularly arranged alternately, and special copolymers. Regarding copolymerization technology, there are block copolymers in which each unit is long and continuous, and graft copolymers in which one unit of one type of monomer is taken over one unit of another type of monomer on a continuous frame. It is a latex that has been developed and developed to have a multilayer structure (for example, a latex that has a two-layer structure consisting of a hard upper layer (shell) and a soft monomer (core)). Then, to improve mechanical stability and binding properties, small amounts of acrylic acid, methacrylic acid, itaconic acid, and maleic acid or their half esters are added for carboxy modification, and emulsifiers are reduced to improve water resistance and suppress foaming. A so-called soap-free type is also used in the present invention. Furthermore, even if the minimum film forming temperature (MFT) is fully controlled by adding a small amount of plasticizer and film forming aid, the objects and effects of the present invention will not be impaired.

Here, the definition and measurement method of the minimum film forming temperature will be explained.

When an acrylic latex aqueous dispersion forms a film, the lowest temperature at which water evaporates and polymer molecules interact with each other to form a film is the minimum film forming temperature (MFT:
Minimum Film Forming Temp
The measurement method is to use a thermal gradient test device to measure the temperature gradient (for example, from -5°C to 195°C).
) is coated with an aqueous acrylic latex dispersion on a metal plate, and dried in an atmosphere excluding humidity. temperature) and whitening point temperature (temperature at which a film becomes white without being formed).

The preferred addition amount of the acrylic latex of the present invention is 10 to 50 parts by weight based on 100 parts by weight of the inorganic color developer in solid weight. If the amount is less than 10 M parts, no improvement in smoothness can be obtained, and if it is more than 50 parts by weight, the important coloring ability is reduced, and the practical commercial value is impaired.

In the present invention, a coating liquid containing an inorganic color developer and an acrylic latex having a minimum film forming temperature (MFT) of +45°C or less as a binder is prepared, and the coating liquid is coated on a sheet-like support with a coater and dried. The major feature is that it is a color developing sheet. According to experiments conducted by the present inventors, the minimum film forming temperature (MP'
When using acrylic latex with T ) of +45°C or higher, a continuous film is formed under normal drying conditions (drying temperature is 105 to 150°C a few seconds after application) using a coater. It was found that the color became white and the binding strength decreased significantly. In addition, the binder latex that is widely known and used is styrene-butadiene-based latex, but according to the experiments of the present inventors, the ratio of styrene and butadiene, the combination of methyl methacrylate, carboxy-modified, and even particle The change in diameter has an effect on the color density and the light fastness of the color image, and the binding power is also sufficient, but the smoothness and staining (smudge) are insufficient.

On the other hand, acrylic latex film is soft, and by keeping the minimum film forming temperature (MFT) below i+45°C, film formation can be completed under normal coater application and drying conditions, resulting in a smooth and smooth film. It is possible to obtain a product with high hardness, no staining (smudges), excellent binding power, sufficient color density of the applied color developer sheet, sufficient light fastness of the color image, and excellent printability.

The present invention provides an inorganic color developer with a minimum film forming temperature (MFT) of +
Add acrylic latex below 45℃, dispersant,
A color developing sheet for image recording materials that is coated and dried on a support such as paper with a water retention agent, antifoaming agent, etc. using a coater such as an air knife, blade, roll, rubber doctor, or curtain. Manufacture.

In the present invention, if desired, water-soluble binders such as starch, polyvinyl alcohol, carboxymethyl cellulose, and dextrin; clay, kaolin, magnesium carbonate, satin white, titanium oxide, zinc oxide, urea resin pigments,
Pigments such as plastic pigments, talc, alumina, aluminum hydroxide, etc. may be added to the coating solution.

Inorganic color developers particularly recommended for use in the present invention include the semi-synthetic solid acids described in JP-A-57-15996 and JP-A-58-16885, but are not limited to these. Colorless (leuco) dyes are adsorbed onto the surface of the colorant and develop color, so the larger the specific surface area per unit weight, the better the color development efficiency becomes. That is, the smaller the particle size of the color developer is, the more advantageous it is. The present invention is most effective when trying to improve color development efficiency by minimizing the particle size of the inorganic color developer, and to prepare a fluid coating solution that does not gel and improve smoothness. do.

Conventionally, the particle size of the inorganic color developer was usually cut to 5 to 6 microns (products that passed through a mesh of 5 to 6 microns), but according to the present invention, particles cut to 4 microns can be used, and even 3.5 microns can be used. Coating liquid can be prepared even for micron cut products.

Next, a method for manufacturing a coloring (agent) sheet (colorless (leuco) dye donor sheet) for blue coloring used in Examples of the present invention will be described. In addition, all parts below represent parts by weight.

Method for producing a coloring (agent) sheet for blue coloring 3.5 parts of crystal violet lactone, which is a colorless (leuco) dye, and 1 part of malachite green lactone are dissolved in 100 parts of a diarylethane-based organic solvent, which is a high boiling point solvent, to produce acid-treated gelatin. (Isoelectric point: 7.8) It was emulsified in 160 parts of a 10% aqueous solution.

Emulsion of 11,500 parts of water with 20 parts of gum arabic dissolved in it, and adjusted to pH 8.5 with caustic soda.
Keep the liquid temperature at 0℃, adjust the pH to 4.4 with acetic acid, cool to 10℃, and add 20 parts of 37% formalin aqueous solution.
After continuing to stir for 4 hours, the mixture was adjusted to pn 10 with caustic soda and made into microcapsules.

Add 100 parts of the above microcapsules (solid content) to 50 parts of K10 per cent polyvinyl alcohol aqueous solution and 30 parts of wheat starch to give a coating amount of 5 f/l on 40 ♡ high-quality paper.
r? (solid content) using an air knife coater and dried to obtain a blue coloring (agent) sheet.

Hereinafter, preferred embodiments and excellent effects of the present invention will be explained in detail using the most typical examples.

(g)l Examples Example 1 3.5 parts of 30% sodium silicate and 1° part of 5% sodium pyrophosphate were added to 180 parts of water and stirred to obtain semi-synthetic solid acid (particle size: 3.5 microns). )1
After gradually adding and dispersing 00 parts without stirring, 10 parts
Add 100 parts of percent oxidized starch aqueous solution, stir, and add 40 parts of 50 percent styrene acrylic latex (ratio of styrene/butyl acrylate = 55/45 copolymer latex Φ minimum film forming temperature (MFT) + 20°C). The mixture was stirred to form a coating liquid. This coating liquid f 40 t/n?
The amount of coating on high quality paper is 4.8fA7? (solid content) was coated with an air knife coater and dried to form a color developing sheet.

Example 2 50 percent styrene acrylic latex of Example 1 (ratio styrene/butyl acrylate = 55745)
Copolymer latex・Minimum film forming temperature (MFT) +20
°C) to 50% methyl methacrylate acrylic latex (ratio methyl methacrylate/butyl acrylate/2φ ethylhexyl acrylate) = 15/45
/40 copolymer latex/minimum film forming temperature (MF'T
40 f/lt? The coating amount was 4.8η2 (
It was coated with an air knife coater and dried to give a color developing sheet (solid content).

Example 3 30 percent sodium silicate in 173.5 parts of water 3.
5 parts and 10 parts of 5% sodium birophosphate were added and stirred to form a semi-synthetic solid acid (particle size: 3.5 microns).
) After gradually adding and dispersing 100 parts with stirring,
Addition of 100s'e of 10% oxidized starch aqueous solution-
Stir and add 46.5 parts of 43% methyl methacrylate acrylic latex (two-layer latex with a ratio of methyl methacrylate (shell layer)/butyl acrylate (core) = 15785, minimum film forming temperature (MFT) + 37°C) and stir. It was made into a coating liquid. This coating liquid f 40 t/;r?
The mixture was coated on high-quality paper using an air knife coater to a coating amount of 4.8 f/d (solid content) and dried to form a developing sheet.

Comparative Example 1 3.5 parts of 30% sodium silicate in 24.5 parts of water
10 parts of sodium birophosphate and 300 parts of 10% starch oxide aqueous solution were added and stirred.
Semi-synthetic solid acid (particle size 3.5 microns) 100
The mixture was gradually added and dispersed while stirring to form a coating liquid. This coating liquid was applied to a 4097-backed high-quality paper using an air knife coater so that the coating amount was 4.8 fA (solid content) and dried to form a color developing sheet.

Comparative Example 2 A coating liquid was prepared in the same manner as in Comparative Example 1 except that the same amount of the 10% e-formed starch aqueous solution was replaced with a 10% polyvinyl alcohol (saponified 1i 98.5 mol percent, degree of polymerization 500) aqueous solution. ? The coating amount on high-quality paper is 4.89. Ay? (solid content) was dried using an air knife coater to form a color developing sheet.

Comparative Example 3 To 180 parts of water, 3.5 parts of 30% sodium silicate and 10 parts of 5% sodium pyrophosphate were added and stirred, and 1 part of semi-synthetic solid acid (particle size cut to 3.5 microns) was added.
After gradually adding and dispersing 00 parts with stirring, 10 parts
Add 100 parts of percent oxidized starch aqueous solution and stir for 50 minutes.
155/35 copolymer latex/minimum film forming temperature (M
FT) +5°C) was added and stirred to prepare a coating liquid. This coating liquid was applied to 40 t/lri high-quality paper using an air knife coater so that the coating amount was 4.8 ml (solid content).
It was dried and made into a color developing sheet.

Comparative Example 4 The 50% styrene-butadiene latex of Comparative Example 3 (copolymer latex with a ratio of methyl methacrylate/styrene/butadiene = 10155/35 - minimum film forming temperature (MFT) - 5°C) was converted into 50% styrene-acrylic latex. Coating liquid was applied in the same manner except that the same amount was replaced with Tux (copolymer latex with a ratio of styrene/butyl acrylate = 75/15, minimum film forming temperature (MFT) + 59°C), and coated on high-quality paper with a back of 40. Application, amount is 4. El/
m'' (solid content) and was coated with an air knife coater and dried to form a color developing sheet.

Comparative Example 5 2O-J1 The 50% styrene-butadiene latex of Example 3 (copolymer latex with a ratio of methyl methacrylate/styrene/butadiene = 10155/35, minimum film forming temperature (MFT) + 5°C) was replaced with 50% methyl methacrylate acrylic. Latex (ratio methyl methacrylate (shell layer)/ethyl acrylate (core) = 5015
0 two-layer structure latex/minimum film forming temperature (IViFT)
+73°C) except that the temperature was changed to 4.8f/ly, using the same method to apply the liquid to high-quality paper of 40f~ C solid content) was coated with an air knife coater and dried to form a color developing sheet.

Test Method The color developing sheet obtained as described above was tested and measured in the following manner.

Q Color development density Color development sheet The color development sheet was passed through a calendar together with the above color development (agent) sheet, and the following values were measured using a color difference meter. The smaller the number, the higher the color density.

0 Smoothness Measured using a Beck smoothness tester. The larger the number, the higher the root lubricity.

o Dirt (colored stains due to smudges and masatsus) Omo IJ
' was placed on the sheet and rubbed against the above color developing (agent) sheet, and the following values were measured for stains on the color developing sheet using a color difference meter. The higher the number, the less dirt there is. ,.

O surface strength (printing/aptitude test) The strength when measured using an IGT tester is 5.4.3
．． It was set to 2.1. (5...strong, 1...weak) η Invention effectiveness test results! 118-/-1 (7) + 1 Similar work margin) Table 1 As is clear from Table 1, the semi-synthetic solid acid and the binder, acrylic latex at a minimum film-forming temperature CMFT) +45°C or less, are used. Containing color developer sheet 1 - By manufacturing,
It can be seen that a color developing sheet for image recording materials with excellent smoothness, very little staining (smudges), good surface strength and high color density can be obtained.

Procedural correction tooth (method) % formula % 2, Name of the invention Developing sheet for image recording material 3, Relationship with the case of the person making the amendment Patent applicant address 4-2 Marunouchi Otsu-chome, Chiyoda-ku, Tokyo @ Name (598) ) Mitsubishi Paper Mills Co., Ltd. 4, Agent Address: 100 Marunouchi, Chiyoda-ku, Tokyo = No. T 4-2 Mitsubishi Paper Mills Co., Ltd. 6, Subject to amendment ○ Yes.

"3. Detailed explanation of the invention"

Claims (1)

[Scope of Claims] 1. In a color developer sheet for an image recording material comprising an electron-donating colorless dye and an electron-accepting color developer capable of coloring the colorless dye, an inorganic color developer and an acrylic latex are coated as a coating layer. A color developing sheet for an image recording material, characterized in that it contains: 2. The inorganic color developer is derived from a clay mineral having a layered structure consisting of regular silica tetrahedrons, and according to electron diffraction, the inorganic color developer is a crystal with a layered structure consisting of regular silica tetrahedra. However, according to X-ray diffraction, it does not substantially show a diffraction pattern based on a crystal with the above structure, and the color developer contains at least silicon, magnesium, and/or aluminum as an element other than oxygen. A color developing sheet for an image recording material according to claim 1. 3. Acrylic latex has minimum film forming temperature (MFT) +
The color developing sheet for image recording materials according to claim 1, which has a temperature of 45° C. or lower.