JPH0667665B2 - Developer composition for leuco dye - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to a developer composition for leuco dyes,
More specifically, it relates to a developer composition which is excellent in coating workability and has a combination of excellent initial color density, fading resistance and water resistance.

(Prior Art) Conventionally, a combination of a leuco dye and a developer made of an acidic substance has been widely used for various information recording, for example, pressure-sensitive recording, heat-sensitive recording, electrophotographic recording, printing and the like. .

Known as developers are organic compounds such as various phenols, phenolic resins, zinc salicylate and its derivatives, and inorganic solid acids such as silica, aluminum silicate, clay minerals or acid-treated products thereof. However, while the inorganic solid acid type is excellent in heat resistance, solvent resistance, printing and transcription characteristics, etc., it is inferior in terms of color development performance, fading due to the effects of light, heat and moisture. Defects are recognized.

For example, a developer composed of amorphous silica gives a clear color image in combination with a leuco dye, but the image formed is extremely poor in light fastness, for example, when exposed to a weather-o-meter for 2 hours, Image density drops below 50%. Aluminosilicate-based clay minerals or acid-treated products thereof have slightly better light resistance than amorphous silica, but they tend to discolor when an image comes into contact with water.

In particular, in the field of pressure-sensitive paper, a paper substrate provided with a layer of a color developer on one surface is used as a so-called stamp paper, but when a viscous mineral or an acid-treated product thereof is used as a color developer. Has a problem that the coating layer is colored in a specific hue. Further, known developers tend to cause discoloration when exposed to light or environment for a long time, and this tendency is remarkable in the case of organic developers such as phenol resins.

In JP-A-56-37189, a solid acid developer such as acid clay or activated clay is compounded with a combination of a thiourea compound and a zinc oxide and / or zinc hydroxide as an agent for promoting color development and fading. Is described.

(Problems to be Solved by the Invention) First, an inorganic solid acid-based developer, like other inorganic-based developers, has a remarkably high viscosity when made into an aqueous coating solution, and therefore, The constraint arises that the agent must be applied to the paper as a relatively dilute concentration of coating solution. On the other hand, in terms of the pressure-sensitive paper manufacturing cost, it is desired to reduce the thermal energy cost for evaporating water as much as possible, so that the viscosity of the developer coating solution can be reduced and the solid content concentration can be reduced. It is an important technical requirement to raise it as much as possible.

In particular, when the inorganic solid acid-based developer is compounded with a metal oxide or hydroxide, as seen in the prior art,
It is recognized that the viscosity of the coating solution is much larger than the viscosity of the inorganic solid acid developer alone.

(Means for Solving the Problems) The present inventors have proposed that an inorganic magnesium salt of layered silicic acid having a MgO / SiO ₂ molar ratio in the range of 0.14 to 1.20 and a specific surface area of 180 m ² / g or more. When a solid acid color developer is mixed with a thiourea compound and at least one carbonate salt of calcium and magnesium and a reaction is carried out between at least a part of them, the reaction mixture is used as a color developer. Dispersion in water to prepare an aqueous coating solution can lower the viscosity far more than the original inorganic solid acid developer aqueous coating solution, so that a high-concentration aqueous coating solution can be prepared for coating work. Therefore, it has been found that the coating workability can be remarkably improved.

Further, it was found that the resulting developer composition has a markedly improved color forming performance, the initial color density is remarkably improved, and further the light resistance and the fading resistance are improved and excellent water resistance is obtained. .

The present invention has been completed based on this finding.

The purpose of the present invention is to provide a developer having excellent color forming performance as a developer, initial color density, light resistance, fading resistance and water resistance, and having a low viscosity of the developer coating liquid and excellent coating workability. A colorant composition is provided.

According to the present invention, an inorganic solid acid developer, a thiourea compound, which is a magnesium salt of layered silicic acid having a MgO / SiO ₂ molar ratio in the range of 0.14 to 1.20 and a specific surface area of 180 m ² / g or more, And a leuco dye developer composition comprising a reaction mixture of at least one carbonate of calcium and magnesium.

(Function) In the present invention, the remarkable decrease in the viscosity of the aqueous coating solution, the remarkable improvement in the color development performance, the initial color density, the light resistance and the fading resistance, and the excellent water resistance are obtained by the above-mentioned inorganic solid acid color development. It becomes possible only by adding a thiourea compound and a carbonate to the agent and carrying out a partial reaction.

That is, as shown in the examples described below, when thiourea alone is blended with the inorganic solid acid developer or when carbonate alone is blended, the viscosity of the aqueous coating solution is adjusted to that of the coating solution containing only the developer. On the other hand, it cannot be lowered at all. Further, when oxides and hydroxides were used instead of the metal carbonates, even in combination with thiourea, the viscosity was remarkably increased as compared with the viscosity of the coating liquid containing the developer alone. To be

On the other hand, in the present invention, when the thiourea compound and at least one carbonate of calcium and magnesium are allowed to act on the inorganic solid acid, the viscosity of the aqueous coating solution is quite unexpected from the fact described above. It was found that the color remarkably decreased as compared with the case where only the color developer was used. The reason for this has not yet been clarified, but it is considered that the reason is that a reaction has occurred between the inorganic solid acid developer, the thioureas and the carbonate. That is, it is considered that a reaction occurs between them and the metal components in the thiourea and the carbonate are taken in and incorporated between the layers of the inorganic solid acid developer. Moreover, the metal component incorporated between the layers as described above has an initial color-developing density, light resistance, fading resistance and water resistance of the inorganic solid acid developer as compared with a composition containing these components in a mixed state. , Which will be apparent from the examples below.

(Advantageous Effects of the Invention) According to the present invention, it is possible to greatly reduce the viscosity of the coating liquid of the color developer, which makes it possible to significantly improve the coating workability of the coating liquid when manufacturing the pressure-sensitive recording element. In addition, the solid content concentration in the coating liquid can be increased to reduce the heat energy cost required for water evaporation.

In addition, while increasing the initial color density of the image formed by the reaction of the inorganic solid acid developer and the leuco dye, it prevents the fading tendency associated with exposure to light rays and various atmospheres, and further improves the image by contact with water. It is possible to prevent the tendency for the concentration to decrease remarkably.

(Explanation of preferred embodiments of the invention) In the present invention, as the inorganic solid acid developer, MgO / SiO 2 is used.
The molar ratio of ₂ is in the range of 0.14 to 1.20 and the specific surface area is 180.
A layered silicic acid magnesium salt having a m ² / g or more is used.

A specific manufacturing method of this product is, for example, Japanese Patent Publication No. 4-64874.
It is disclosed in the publication. For example, a clay ore having a layered structure of tetrahedron of silica has a SiO ₂ content of 82 to 96.5% by weight, preferably 85 to 95% by weight on a dry basis (dried at 105 ° C. for 3 hours). Acid treatment so that the resulting clay mineral is in contact with at least one compound of magnesium and aluminum, which is at least partially soluble in the medium, in an aqueous medium, and the soluble compound is other than hydroxide. In the case of, it can be produced by neutralizing with an alkali or an acid so as to form a hydroxide, introducing at least one component of magnesium and aluminum into the acid-treated clay mineral, and drying if desired. it can. These have a basic layer unit having a three-layer structure in which two tetrahedral layers of SiO ₄ are sandwiched with at least one octahedral layer of AlO ₆ and MgO ₆ sandwiched between them. The basic unit is a two-layer structure in which the integrated one and at least one octahedral layer of AlO ₆ and MgO _{6 and} a tetrahedral layer of SiO ₄ are paired, and the basic layer unit is integrated in the C-axis direction. There are things and combinations of these. The degree of accumulation in the C-axis direction can be variously changed from regular to random.

In the magnesium salt of layered silicic acid of the present invention, magnesium is mainly introduced into the acid-treated mineral.

In the present invention, the molar ratio of MgO / SiO ₂ is 0.14 to 1.2.
0, especially in the range of 0.28 to 0.97 and a specific surface area of 180 m ²
Magnesium salt of layered silicic acid in the range of / g or more, especially 200 m ² / g or more is used. As a typical example of this, a commercially available developer for semi-synthetic pressure sensitive paper Shilton SS-1 (manufactured by Mizusawa Chemical Co., Ltd., trade name, MgO / SiO ₂ molar ratio 0.25 to 0.75, specific surface area 350 to 500 m ² / g) ).

As the thiourea compound, thiourea, alkylthiourea (eg N-ethylthiourea), arylthiourea (eg N, N-diphenylthiourea) and the like can be used.

At least one carbonate salt of calcium and magnesium may be used alone or in combination with each other. Further, the carbonate may be a normal carbonate or a basic carbonate.

In the present invention, the amount of the thiourea compound and the carbonate with respect to the inorganic solid acid developer is 1 to 50 parts by weight, particularly 5 to 40 parts by weight, and 1 part by weight of the carbonate per 100 parts by weight of the inorganic solid acid. To 50 parts by weight, especially 2 to 30 parts by weight.

These components may be mixed in advance by wet or dry mixing to prepare the coating liquid, or by adding each component to the coating liquid and carrying out mixing and reaction on the spot. Good.
Heating is preferably performed to accelerate the reaction, and this heating may be heating when the coating liquid is dried.

The developer composition for a leuco dye of the present invention is particularly useful for producing a pressure-sensitive recording paper. In the production of stamp paper, solid acid developer is 5 to 50% by weight, especially 15 to 40% by weight, and binder is 1 to 10% by weight, especially 3 to 8% by weight.
To prepare an aqueous slurry containing 1 to 10 g / color developer
It is applied at a coating amount of m ² , particularly 3 to 8 g / m ^2, and dried. Examples of the binder include aqueous latex binders such as styrene-butadiene copolymer latex; self-emulsifying binders such as self-emulsifying acrylic resins; water-soluble binders such as carboxymethyllose and polyvinyl alcohol. Can be applied to all recording methods, for example, heat sensitive recording, electrophotographic recording, printing and the like.

The leuco dye developer composition of the present invention can be mixed with known organic developers such as phenol resins, zinc salicylate or its derivatives in various proportions, and the leuco dye of the present invention can be used. It is one of the useful forms of use, which takes advantage of the excellent advantages of the color developer.

The invention is illustrated by the following example.

In the examples, the method for preparing a stamp paper, the method for measuring its color development performance and water resistance, and the method for measuring the viscosity of a dispersed slurry are as follows.

1. Preparation of Stamp Paper The color developer samples prepared in the respective examples were taken to be 20 g on a dry weight basis at 110 ° C. and dispersed in 50 g of water and 10 g of SBR latex (Dow620, solid content concentration 50%). After that, 1
Adjust the pH of the slurry to 9.5 by adding 0% NaOH. A small amount of water is added to make the total amount 100 g, and a uniform slurry is obtained by stirring. (Color developer concentration =
20%, solid content concentration = about 25%).

The slurry prepared as described above is applied to each of the four base paper sheets using a coating rod.

2. Coloring performance (2-1) Coloring The transfer paper coated with microcapsules containing various colorless dyes and the receiving paper prepared by the above method are overlaid,
Color is developed by applying pressure. In other words, two sheets of paper are superposed so that the surface of the stamp paper coated with the color developer and the surface of the transfer paper coated with the microcapsules face each other, and a pressure of 50 kg / cm ² is applied to completely crush the microcapsules and develop color on the stamp paper. Get a face.

The colorless dyes contained in various transfer papers used are as follows. (Color in parentheses is the color tone) CVL paper (violet) = crystal violet lactone.

Commercially available transfer paper (blue / black) = crystal violet / lactone / benzoyl / leucomethylene blue.

(2-2) Initial color development performance The color development surface of the receiving paper obtained by the method of (2-1) is exposed indoors so that direct sunlight is not exposed, and after 1 hour, the reflection density of the visible part is measured with a densitometer ( Fuji Photo Film KK, Fuji Densi
tometer Model-P), and the average value of the measured values of four samples and the visual observation are used for the determination, and the evaluation is displayed by the following symbols.

(2-3) Printing lightfastness (2-3-1) Indoor lightfastness After the color-developing paper measured in (2-2) was left indoors for one month in the same manner, the color density and The printing light resistance is evaluated from the degree of fading as follows.

(2-3-2) Daylight resistance to sunlight After selecting the day of fine weather for the colored printing paper measured in (2-2) and leaving it for 5 hours outdoors in direct sunlight, the same evaluation as (2-3-1) was conducted. To do.

3. Water resistance Put the stamp paper in a desiccator filled with saturated saline solution (related humidity 75%), leave it at 80 ° C for 24 hours, and then take out the stamp paper and color it. This color density was compared with the initial color density which was normally colored separately.

Example 1 and Comparative Example 1 thiourea was dissolved in a predetermined amount of water (the total solid content concentration was 25% finally), and calcium carbonate and magnesium carbonate were shown in Table 1 with sufficient stirring. Finally, a commercially available layered magnesium silicate-based semi-synthetic pressure sensitive developer Shilton SS-1 (manufactured by Mizusawa Chemical Industry Co., Ltd.) was added.
100 g on a dry weight basis at 0 ° C. was added and treated at 90 ° C. for 2 hours. After that, the entire slurry was sufficiently dried with an electric constant temperature dryer at 110 ° C. and pulverized to obtain a sample.

The viscosities of the slurries dispersed in water were measured for these samples, and the color development performance and water resistance were tested. The results are shown in Table 1.

For comparison, Shilton SS-1 alone, Shilton
The same combinations were tested for combinations of SS-1 and thiourea, Shilton SS-1 and calcium carbonate, and Shilton SS-1 and magnesium carbonate. The results are shown in Table 1.

As can be seen from the table, each of the examples (1-1 to 1-4) shows a marked decrease in viscosity as compared with the comparative example. Also, a remarkable improvement in color development performance is recognized. Water resistance shows good results.

Example 2 Silton SS-1, thiourea, calcium carbonate and carbonic acid, magnesium were tested in the same manner as in Example 1 at the mixing ratios shown in Table 2. The test results are shown in Table 2. By changing the ratio of thiourea with respect to the carbonate, it was possible to obtain a product having both excellent color development performance and water resistance.

Claims (1)

[Claims] 1. An inorganic solid acid developer which is a magnesium salt of layered silicic acid having a MgO / SiO ₂ molar ratio of 0.14 to 1.20 and a specific surface area of 180 m ² / g or more, a thiourea compound, and A developer composition for leuco dyes which comprises a reaction mixture of at least one carbonate of calcium and magnesium.