JPS597085A - Developer sheet for pressure-sensitive duplication - Google Patents

Abstract

PURPOSE:To obtain a developer sheet for pressure-sensitive duplication, having improved yellowing resistance and excellent sanitary safeness by providing a developer containing a phenol novolak resin, a clay mineral (e.g., acid clay, etc.), and zinc citrate on a supporter. CONSTITUTION:A paint containing containing phenol novolak resin and/or a clay mineral (e.g., one or more of acid clay, activated clay, etc.) and zinc citrate, with 1:99-90:10 proportion of clay mineral and zinc citrate, is coated on a supporter (e.g., paper, etc.) by means of knife coater, etc., in an amount of 40-60g/m<2> and dried to obtain an objective sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color developer sheet for pressure-sensitive copying. More specifically, a phenol novolac resin and/or a color developer based on clay minerals such as acid clay, activated clay, attapulgite, zeolite, bentonite, kaolins, and talcs containing a zinc salt of citric acid is added to the support. The object of the present invention is to provide a color developer sheet that improves yellowing resistance while retaining the original characteristics of a color developer layer mainly composed of clay minerals, and is excellent in terms of hygiene and safety.

As is already well known, clay minerals such as acid clay, activated clay, and bentonite have been used as color developers for pressure-sensitive copying paper for a long time. When left in the air, due to the strong adsorption properties of clay minerals, they absorb moisture from the air, which reduces the strength of the coloring reaction, and nitrogen oxides, which are often dropped as airborne pollutants. It absorbs cigarette smoke, leading to yellowing, and it also absorbs cigarette smoke, causing yellowing and reducing the intensity of coloring.Furthermore, the colored image changes in hue, reducing its commercial value. It has often been finger-dropped. However, as mentioned above, instead of color developers mainly consisting of clay minerals, which are compounds without bars, compounds with bars were used, such as phenols in Japanese Patent Publication No. 48-33210 and phenol novolac resins in Japanese Patent Publication No. 42-20144. Many coloring agents have been proposed for use in combination with clay minerals. However, phenol and polyhydric phenols alone do not have a strong instantaneous coloring, and they have an odor, low vapor pressure, and are definitely not desirable from the viewpoint of toxicity and health and safety. It's hard to say.

Furthermore, phenol compounds are generally not used for prizes because they tend to yellow due to nitrogen oxides in the air. Therefore, in order to improve these drawbacks, proposals have been made to use a high-molecular-weight product as a color developer, and one of them that has been put into practical use is a combination of phenol novolac resin and clay mineral. . It is true that there is something to be seen in terms of sunlight resistance over time, but improvements to more stable quality are desired. In other words, if the color developing sheet itself is left in the air, yellowing cannot be avoided. There are also problems in terms of price and handling. Furthermore, recently, aromatic acids in which the benzene nucleus is substituted with carboxylic acid groups or sulfonic acid groups, and polyvalent metal salts of hydroxy-containing aromatic acids have become very effective as color developers for pressure-sensitive copying, and clay minerals have been developed. There is also a proposal that a color developer sheet for pressure-sensitive paper can be manufactured without using any kind of materials. For example, salicylic acid, hydroxynaphthoic acid, and polyvalent metal salts of their derivatives have been proposed in many cases, including Japanese Patent Publications No. 49-10856, Japanese Patent Publication No. 20883-1983, Japanese Patent Publication No. 25174-1974, and Japanese Patent Publication No. 49-13451. There is. It is true that these inventions have excellent color development strength, speed, density, and light resistance as a color developer for pressure-sensitive paper without using any clay minerals, and the yellowing of the color developer sheet itself has been significantly improved. It is excellent as a color developer sheet for pressure-sensitive paper. However, these proposed polyvalent metal salts of hydroxyl-containing aromatic acids that are directly linked to the benzene nucleus, such as salicylic acid and hydroxyna silicate, pose no health and safety problems. It is not clear whether or not there is no such substance, but its raw materials, such as salicylic acid and hydroxynaphthoic acid, are not completely toxic orally, and they are not strictly toxic as color developers for pressure-sensitive paper used as office supplies. It is considered inappropriate in its meaning.

In consideration of the above points, the present invention has been developed by carrying out further intensive studies on a color developer layer for pressure-sensitive paper which is mainly composed of clay minerals, and has arrived at the present invention. That is, a phenol novolac resin and/or a concrete containing zinc citrate and at least one clay mineral selected from acid clay, activated clay, attapulgite, zeolite, bentonite, kaolin, and talc is placed on a support such as paper. It consists of a color developer sheet for pressure-sensitive recording provided with a color layer.

The clay minerals used in the present invention are selected from well-known acid clay, activated clay, attapulgite, zeolite, bentonite, kaolin, and talc. Acidic clay or activated clay, which has a large capacity as a solid acid, is preferably used.

On the other hand, phenol novolaks used in combination with clay minerals are commonly known, do not contain groups such as methylol groups, are obtained by polymerizing phenols and formaldehyde, and are generally insoluble in water. Particularly desirable are phenol resins obtained by polymerizing formaldehyde with phenols having a substituent at the P position of the phenolic hydroxyl group, such as P-phenylphenol, P-cyclohexylphenol, and P-nonylphenol.

Zinc salts of citric acid or zinc salts of citric acid can be used as yellowing resistance improvers that have the characteristics of the phenol novolac resin and/or clay mineral that are the object of the present invention, have no problems in terms of safety and health, and can be used as yellowing resistance improvers. We have found that particular oxides or zinc hydroxides or carbonates are most effective for the present invention. For example, lactic acid, tartaric acid, malic acid, and glycolic acid are examples of acids similar to citric acid, but for reasons that are completely unknown, the effects of the present invention cannot be obtained. On the other hand, dibasic acids such as oxalic acid, maleic acid and fumaric acid, which are more acidic than citric acid as aliphatic acids, as well as saturated or unsaturated carboxylic acids with one or more carbon atoms such as formic acid and acetic acid, can also be converted into zinc salts. Although the reason for this is not clear, the coloring ability itself is completely poor and the effects of the present invention cannot be obtained at all. Therefore, with these zinc salts of acid, if the amount added to clay minerals increases, the speed of color development and density will decrease, and if the amount added is too small, the inherent defects of clay minerals cannot be corrected. It has no particular effect.

Therefore, the effects of the present invention are not simply due to the strong acidity of aliphatic carboxylic acids, as has been often said.

On the other hand, other polyvalent metal salts such as calcium, magnesium, and aluminum salts can be used instead of zinc salts, but salts other than zinc salts cannot exhibit the characteristics and effects of the present invention and have no coloring ability at all. Therefore, the zinc salt of citric acid of the present invention is a special compound that has an appropriate coloring ability and is resistant to yellowing, and is most suitable for improving the defects of clay minerals. On the other hand, zinc citrate exhibits much better safety than salicylic acids, which are aromatic acids, and is ideal for use in office supplies such as pressure-sensitive paper.

In producing the color developing sheet of the present invention, it is particularly effective to use zinc citrate in a ratio of 1:99 to 90:10 by weight to clay minerals such as acid clay and activated clay. In terms of color development effect and improvement of yellowing resistance, it is rated 5.
:95 to 80:20, particularly preferably about 50:50. However, the proportion of these combinations does not limit the present invention in any way.

In other words, it may be selected appropriately depending on the type and amount of the pressure-sensitive dye used and the type of clay mineral used as a color developer. In addition, if necessary, it is acceptable to add solid powders such as TiO2 and Al2O3 to the blended system of clay minerals and zinc citrate to stabilize the dye dispersion as long as the performance is not impaired. .

The zinc citrate used in the present invention may be obtained by separately dissolving citric acid in water and adding zinc oxide, zinc hydroxide, or zinc carbonate to this to generate zinc citrate. In addition, citric acid and zinc oxide, citric acid and zinc hydroxide, or citric acid and zinc carbonate may be added in the process of making clay minerals into paints to generate zinc salts of citric acid during the process of manufacturing paint dispersions. good. Zinc citrate may be produced by any method as long as it does not impair the yellowing resistance improvement effect of the present invention, and there are no particular limitations on the method for producing zinc citrate salt.

Since the aqueous dispersion obtained as described above cannot be stably present on a support as it is, known glue materials such as gum arabic, ethyl cellulose, polyvinyl alcohol, starch, styrene-butadiene copolymer latex, and acrylic are used. A binder such as butadiene copolymer latex is used alone or in combination. The paint thus obtained is coated with a roll coater, an air knife coater, a knife blade, or any other commonly known coating tool.
Approximately 5 to 10 g/m 2 is coated on a paper surface of 60 g/m 2 and dried.

In this way, it is possible to obtain an excellent product that has a color developer sheet that is resistant to yellowing without impeding the color development ability in any way compared to conventional color developer sheets that are mainly made of clay minerals, and that is also safe from the standpoint of health and safety. I can do it.

Specific examples of the present invention will be described below, but of course the present invention is not limited to these descriptions, and in the examples, parts refer to parts by weight, and percentages refer to percent by weight.

Example 1 192 g (1 mol) of citric acid was dissolved in 600 parts of water, and a predetermined amount of zinc white was gradually added thereto to precipitate zinc citrate. The obtained precipitate is collected by filtering,
It was used in the next step without drying. In other words, 20 parts of activated clay (trade name: Silton, manufactured by Mizusawa Chemical Co., Ltd.) and 10 parts of zinc citrate obtained by the above method are dispersed in 100 parts of water, and if necessary, further finely dispersed with a ball mill. Next, 15 parts of a 10% polyvinyl alcohol aqueous solution was added to form a paint, and a coating amount of 1 was coated on the paper using a knife coater.
Apply on a 40g/m2 paper surface so that it is 0g/m2,
Dry.

Example-2 15 parts of zinc citrate obtained in Example-1 was added to 100 parts of water.
20% of a 10% polyvinyl alcohol aqueous solution.
The mixture was added to form a paint, which was coated on a 40 g/m2 paper surface with a knife coater to a coating amount of 7 g/m2, and dried.

Example 3 Dissolve 19.2 g of citric acid in 150 parts of water, add 30 parts of Silton to this, disperse well, and gradually mix in 10 g of powdered zinc white while stirring to form a dispersed clay. It's rising. Further, 42 parts of a 10% polyvinyl alcohol aqueous solution was added to form a paint, which was coated with a knife coater to a coating amount of 7 g/m2 and dried.

Comparative Example-1 30 parts of activated clay (trademark: Shilton, manufactured by Mizusawa Chemical Co., Ltd.) was dispersed in 100 parts of water, and 22 parts of a 10% polyvinyl alcohol aqueous solution was added to form a paint, with a coating amount of 10 g/m2.
It was coated on a paper surface of 40 g/m2 using a knife coater so that the resultant composition was obtained and dried.

Comparative Example-2 30 parts of zinc oxide was dispersed in 100 parts of water, and then 10%
A coating was prepared by adding 22 parts of a polyvinyl alcohol aqueous solution, and a pressure-sensitive paper provided with a layer of zinc oxide was obtained in the same manner as in Comparative Example-1.

Comparative Examples 3 to 10 Zinc citrate alone instead of activated clay in Comparative Example 1 (Comparative Example 3) Zinc acetate (Comparative Example 4) Zinc tartrate (Comparative Example 5) Zinc lactate (Comparative Example 6) Malein Zinc acid (Comparative example-7) Zinc fumarate (Comparative example-8) 1:1 mixture of activated clay and zinc acetate (Comparative example-9) 1:1 mixture of activated clay and zinc maleate (Comparative example-10) ) were separately made into paints and applied on paper in the same manner as in Comparative Example 1 to create a color developer sheet.

In order to test the performance of the color developer sheets obtained in the above-mentioned Examples and Comparative Examples as copying paper, pressure-sensitive paper manufactured by Fuji Film Co., Ltd. and trademark KS manufactured by Kanzaki Paper Industries Co., Ltd. were used as color developer-containing papers.
Using copy paper and three types of color-containing sheets manufactured by Jujo Paper Co., Ltd., stack them so that the color developer paper prepared in this application is facing each other, press them with a typewriter, print, and measure the color development speed, density, and hue. were determined visually. The color developer sheet was also exposed to the air for 3 months, and the yellowing tendency was determined visually. Furthermore, the specimens were left in a nitrogen oxide atmosphere, and the degree of yellowing was also determined. The results are summarized in Table 1. In the table, ○Good＞○〜△＞△〜○
>△>× to △>× (defective), and the magnitude of color development, yellowing of the color developing layer, and the magnitude of color development after time are compared.

Example-4 15 parts of kaolin and 10 parts of novolac resin obtained by reacting parphenylphenol and formaldehyde were added to 15 parts of activated clay (trademark: Silton, manufactured by Mizusawa Chemical Co., Ltd.) and well dispersed in water, and further 10 parts of zinc citrate was added. The total amount of water was adjusted to 150 parts, and 35 parts of a 10% aqueous solution of polyvinyl alcohol was added to make a paint, and the coating amount was 7 g on 40 g/m2 paper in the same manner as in Example-1. /m2 and dried.

Comparative Example 11 A coating solution without the addition of zinc citrate was prepared in Example 4, applied in the same manner as in Example 4, and evaluated in the same manner as in Table 1. The results in Table 2 were obtained. Got ■

Claims (2)

[Claims] (1) A color developer containing a phenol novolac resin and/or one or more clay minerals selected from acid clay, activated clay, attapulgite, zeolite bentonite, kaolin, and talc, and zinc citrate salt on a support. Pressure-sensitive copying color developer sheet provided with an agent (2) Phenol novolak resin and/or acid clay, activated clay, attapulgite, zeolite,
A color developer for pressure-sensitive copying comprising a color developer layer containing one or more clay minerals selected from bentonite, kaolin, and talc, and citric acid with zinc oxide, hydroxide, or carbonate added. agent sheet