JPH04110186A - Pressure-sensitive copy paper and manufacture of developer therefor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a color developer for pressure-sensitive copying paper and pressure-sensitive copying paper, and in particular to a method for producing a color developer for pressure-sensitive copying paper, in particular a method for producing a copying paper with significantly improved light resistance. The present invention relates to a method for producing a color developer for pressure copying paper.

``Prior art'' Pressure-sensitive copying paper is a top paper coated with a color former capsule composition containing microcapsules containing an electron-donating organic color former (hereinafter simply referred to as color former) on one side of a support. and,
A color developer composition containing an electron-accepting color developer (hereinafter simply referred to as a color developer) as a main component that develops color when it comes into contact with the color former is applied to one side of the support, and a color develops to the other side. There are various types of sheets, such as an inner sheet coated with a color developer capsule composition, and a lower sheet coated with only a color developer composition on one side of the support, and generally the upper sheet-lower sheet, or the upper sheet-middle sheet-lower sheet. They have been put into practical use by combining them in this order. Also known is a self-coloring type pressure-sensitive copying paper in which a color-forming agent capsule composition and a color developer are coated on the same side of a support to enable pressure-sensitive copying on one sheet.

Color developers used in these pressure-sensitive copying papers include clays such as acid clay, activated clay, acupurgite, zeolite, and bentonite, and phenol polymers such as phenol-aldehyde polymers and phenol-acetylene polymers. Furthermore, nuclear substituted salicylates and the like are known.

However, the use of clay has the drawback that during long-term storage, the clay adsorbs substances in the air, resulting in a significant decrease in color developing ability, and that printed characters gradually change color or fade during storage. . Furthermore, there is also the drawback that the print density is extremely reduced when the print is exposed to water. Furthermore, phenol polymers have poor light resistance, and when exposed to light, print density is significantly reduced and the color developer layer yellows.

For this reason, nuclear-substituted salicylates are attracting attention because they exhibit superior properties in various respects compared to clays and phenol polymers.

That is, pressure-sensitive copying paper using a nuclear-substituted salicylate exhibits almost no decrease in color developing ability even after long-term storage.

■Colored printing has good stability over time and is resistant to discoloration or fading.

(2) When using a nuclear-substituted salicylate that is difficult to dissolve in water, the print density hardly decreases even if it gets wet with water.

■The developer layer does not easily yellow even when exposed to light.

■Very high color developing ability.

■Even when processed for several hours under conditions of ioo'c or higher, there is almost no change in color developing ability or print density.

It exhibits various excellent characteristics such as.

However, even with pressure-sensitive copying paper using nuclear-substituted salicylate, if the copying paper before printing or after printing is exposed to direct sunlight, the color developing ability may decrease or the colored image may fade. This phenomenon has been observed, and there is a strong demand for further improvement in light resistance.

``Problems to be Solved by the Invention'' The present invention provides a method for producing a nuclear-substituted salicylate color developer that has significantly improved light resistance without impairing excellent properties such as color developing ability, and a method for producing the color developer. The object of the present invention is to provide pressure-sensitive copying paper with excellent light resistance.

It has been well known for a long time that titanium oxide has ultraviolet absorption ability. However, if titanium dioxide is simply added to the color developer coating solution for the purpose of improving the light resistance of pressure-sensitive copying paper, especially the color developer layer, it is necessary to add a relatively large amount of titanium dioxide. effect cannot be obtained. Moreover, if enough titanium diacid is added to obtain the desired light resistance, the color developing ability will be significantly reduced.

Therefore, the present inventors have conducted various studies on methods for improving the light resistance of a nuclear-substituted salicylate color developer without reducing its excellent color developing ability.

As a result, the inventors discovered that the above objective can be efficiently achieved by mixing and heat-treating a salicylate color developer and titanium diacid to integrate the two, and have completed the present invention.

"Means for Solving the Problems" The present invention provides a zinc salt of a nuclear-substituted salicylic acid having at least one hydrocarbon substituent and a total number of carbon atoms of the substituents being 8 or more, and titanium dioxide. This is a method for producing a color developer for pressure-sensitive copying paper, which comprises mixing and heat-treating the following.

Further, the present invention is a pressure-sensitive copying paper prepared by coating a support with a coating solution containing a color developer for pressure-sensitive copying paper obtained by the above manufacturing method.

"Function" In the present invention, the reason why a color developer for pressure-sensitive copying paper having the above-mentioned excellent properties can be obtained by mixing and heat-treating a zinc salt of a nuclear-substituted salicylic acid and titanium dioxide is not necessarily clear. Although it is not clear, it is assumed as follows. That is, because titanium dioxide exists in a form encapsulated in the zinc salt particles of nuclear-substituted salicylic acid due to the mixed heat treatment,
Although it has the highest hiding power among white pigments, it does not reduce the color developing ability, and it is thought that this is because the purple color (line absorption ability) of titanium dioxide is efficiently exhibited.

It has been known that in the zinc salt of nuclear-substituted salicylic acid, if the total number of carbon atoms in the substituents is less than 8, the effect as a color developer is insufficient. This method uses a zinc salt of a nuclear-substituted salicylic acid having a hydrocarbon substituent whose substituents have a total number of carbon atoms of 8 or more.

Specific examples of such nuclear-substituted salicylic acids include the following.

3-Methyl-5-secondarioctylsalicylic acid, 3-
Methyl-5-tertiaryoctylsalicylic acid, 3-methyl-5-isononylsalicylic acid, 3-methyl-5-secondarydecylsalicylic acid, 3-methyl-5-secondarydodecylsalicylic acid, 3-methyl-5-isododecylsalicylic acid, 3 -Methyl-5-(α-methylbenzyl)salicylic acid, 3-methyl-5-(α,α-dimethylbenzyl)salicylic acid, 3-isopropyl-5-tertiaryoctylsalicylic acid, 3-isopropyl-5-isononylsalicylic acid, 3-isopropyl-5-(α-methylhensyl)salicylic acid, 3-isopropyl-5-(α,α-dimethylbenzyl)salicylic acid, 3,5-ditertibutylsalicylic acid, 35-ditertiarybutyl-6-methylsalicylic acid, 3- tert-butyl-5-tert-lioctylsalicylic acid, 3-tert-butyl-5-isononylsalicylic acid, 3-tert-butyl-5-(α-
methylhensyl) salicylic acid, 3-tert-butyl-
5-(α,α-dimethylbenzyl)salicylic acid, 3.5
- ditertiaryoctylsalicylic acid, 3,5-ditertiaryamyl-6-methylsalicylic acid, 3,5-disendaryohexylsalicylic acid, 3-secondaryoctylsalicylic acid, 3-secondaryoctyl-5-methylsalicylic acid, 3-secondaryoctyl- 6-methylsalicylic acid, 3
-Secondaryoctyl-5-isopropylsalicylic acid,
3-tert-octyl salicylic acid, 3-tert-octyl-5-methylsalicylic acid, 3-tert-octyl-6-methylsalicylic acid, 3-isononylsalicylic acid,
3-isononyl-5-methylsalicylic acid, 3-isononyl-6-methylsalicylic acid, 3.5-diisononylsalicylic acid, 3-isononyl-5-(α-methylbenzyl)salicylic acid, 3-secondarydecylsalicylic acid, 3-secondarydecyl-5- Methylsalicylic acid, 3-secondarydecyl-6-methylsalicylic acid, 3-secondarydodecylsalicylic acid, 3-secondarydodecyl-5-methylsalicylic acid, 3-isododecylsalicylic acid, 3-isododecyl-5-methylsalicylic acid, 3-isododecyl-6-methyl Salicylic acid, 3-cyclohexyl-5-tert-butylsalicylic acid, 3-cyclohexyl-5-isononylsalicylic acid, 3-cyclohexyl-5(α-methylbenzyl)salicylic acid, 3-phenyl-5-isononyl Salicylic acid, 3-phenyl-5-(α-methylbenzyl)salicylic acid, 3-phenyl-5-(α,α-dimethylbenzyl)salicylic acid, 3-(α-methylhensyl)salicylic acid, 3-(α-methylhensyl)-5 - methyl salici)
IiM, 3-(α-methylhensyl)-5-isononylsalicylic acid, 3,5-di(α-methylhensyl)salicylic acid, 3-(α,α-dimethylhensyl)salicylic acid,
3-(α,α-dimethylhensyl)-5-methylsalicylic acid, 3-(α,α-dimethylhensyl)-6-methylsalicylic acid, 35-di(α,α-dimethylbenzyl)salicylic acid, 3.5 -di(α,α-dimethylhensyl)-
Condensation or addition products of 6-methylsalicylic acid, furthermore 3,5-di(α-methylbenzyl)salicylic acid, and hensyl chloride or styrene.

However, here, the tertiary octyl group refers to a dimer of diisophthylene or 1-butene, the isononyl group refers to a trimer of propylene, and the isododecyl group refers to a tetramer of propylene or a trimer of 1-butene. are defined as substituents formed by adding to the nucleus of salicylic acid.

All of these nuclear-substituted salicylic acids form salts with zinc. There are two types of salts: neutral salts in which one atom of zinc corresponds to two molecules of nuclear-substituted salicylic acid, and basic salts in which one or more zinc atoms correspond to two molecules of nuclear-substituted salicylic acid. However, any of them can be used for the purpose of the present invention.

On the other hand, the method for producing titanium dioxide used in the present invention is not particularly limited, and white fine powder obtained by a general production method such as a sulfuric acid method or a chlorine method can be used. Further, as the particle size of titanium dioxide, fine powder having an average primary particle size of 2 microns or less is preferable.

Note that, if necessary, it is also possible to use titanium dioxide that has been surface-treated by adding soluble salts such as aluminum, zinc, tin, and silica.

There are various embodiments of the method of producing a color developer by heat-treating a mixture of a zinc salt of a nuclear-substituted salicylic acid and titanium dioxide, as listed below, but any method is suitable. You can get good results.

■ Mix the zinc salt of nuclear-substituted salicylic acid and titanium dioxide, heat treat the mixture, cool it, and then pulverize it to make a color developer.

■ A zinc salt of nuclear-substituted salicylic acid and titanium dioxide are mixed and heat-treated in the presence of water or an organic solvent, and if desired, the water or organic solvent is removed after the heat treatment, dried, and then finely pulverized to form a color developer. shall be.

(2) A zinc salt of a nuclear-substituted salicylic acid and titanium dioxide are mixed and heated in the presence of water or an organic solvent to remove the water or organic solvent, dried, and then pulverized to obtain a color developer.

■ A zinc salt of a nuclear-substituted salicylic acid and titanium dioxide are dispersed in the presence of water and an organic solvent, and then heat-treated. If desired, after the heat treatment, at least a portion of the organic solvent or at least a portion of the organic solvent and water are dispersed. A portion is removed to obtain an aqueous developer dispersion.

■ Add zinc salt of nuclear-substituted salicylic acid and titanium dioxide to water,
It is emulsified and dispersed in the presence of a dispersant and an organic solvent, followed by a heat treatment, and if desired, after the heat treatment, at least a portion of the organic solvent or at least a portion of the organic solvent and a portion of the water are removed to form a color developer. Make an aqueous dispersion.

■ Add zinc salt of nuclear-substituted salicylic acid and titanium dioxide to water,
It is emulsified and dispersed in the presence of a dispersant and an organic solvent, and then heated to remove at least a portion of the organic solvent or at least a portion of the organic solvent and a portion of the water to obtain an aqueous developer dispersion.

■ Nuclear substitution Nuclear substitution is produced by adding an excess amount of an aqueous solution of alkali hydroxide or alkali carbonate, an aqueous solution of a water-soluble zinc salt such as zinc sulfate or zinc chloride, and titanium dioxide to the alkali metal salt of nuclear-substituted salicylic acid to perform double decomposition. A water-insoluble substance containing zinc salt of salicylic acid and titanium dioxide is separated and used as a color developer. Note that the heat treatment may be performed either during metathesis or after metathesis.

■ Titanium dioxide, an organic solvent, and an aqueous solution of a water-soluble zinc salt such as zinc sulfate or zinc chloride are added to an aqueous solution of an alkali metal salt of a nuclear-substituted salicylic acid to cause double decomposition, and the resulting product contains a zinc salt of a nuclear-substituted salicylic acid and titanium dioxide. The organic layer is separated, and the organic layer is treated in the same manner as in item (1), item 0, item 0, or item 0 above to obtain a color developer or a color developer aqueous dispersion.

The above heat treatment temperature is preferably in the range of 40 to 220 °C, more preferably in the range of 50 to 2 (10 °C). The heat treatment time depends on the heat treatment temperature and the presence or absence of water or organic solvent. for 5 seconds or 2 (1
It varies over a wide range of 0 hours.

When the heat treatment temperature is low, a longer treatment time is required, and the presence of an appropriate amount of water or an organic solvent has the effect of shortening the treatment time.

The organic solvent used in the method of the present invention preferably has a boiling point in the range of 50 to 2 (10 °C) at normal pressure. Specific examples thereof include methanol, ethanol, isopropanol, butanol, secondary butanol, Isobutanol, tertiaryliftanol, pentanol, isopentanol, ethylene glycol 1,000 methyl ether, ethylene glycol 1,000 ethyl ether, ethylene glycol monobutyl ether, 3-methoxybutanol, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, dioxane, acetone, Examples include methyl ethyl ketone, methyl isobutyl ketone, hexane, heptane, octane, dichloroethane, trichloroethane, cyclohexane, methylcyclohexane, henzene, toluene, xylene, ethyl henzene, chlorohensen, and dichlorobenzene.

Preferred dispersants that can be used in the present invention include, for example, alkali metal sulfate esters, alkyl sulfonic acids, alkylnaphthalene sulfonic acids, N-methyltaurine oleic acid amide, dialkyl sulfosuccinates, or sulfuric esters of alkylphenol ethylene oxide adducts. , anionic surfactants represented by ammonium or amine salts and funnel oil, alginic acid,
Carboxymethylcellulose, phosphorylated starch, lignin sulfonic acid, acrylic acid polymer, acrylic acid copolymer, vinylhenzenesulfonic acid polymer, vinylhenzenesulfonic acid monopolymer, maleic acid copolymer, itaconic acid copolymer, or High molecular weight anionic compounds represented by alkali metal, ammonium or amine salts such as sulfuric esters of polyvinyl alcohol, and water-soluble nonionic compounds represented by polyvinyl alcohol, methyl cellulose, acrylamide polymers or acrylamide copolymers, etc. Examples include molecular compounds.

Furthermore, in the present invention, in order to further improve the suitability of the zinc salt of nuclear-substituted salicylic acid as a color developer for pressure-sensitive copying paper, antioxidants, ultraviolet absorbers, plasticizers, or polymer compounds may be added as appropriate. You can also do it.

The most preferable positional relationship between the zinc salt of nuclear-substituted salicylic acid and titanium dioxide is that titanium dioxide is encapsulated in the fine particles of the zinc salt of nuclear-substituted salicylic acid.
It is desirable to use it in the range of 1 to 3 (10 parts by weight, more preferably 2 to 50 parts by weight) per 0 parts by weight.

The color developer produced by the method of the present invention is wet-pulverized if necessary, and starch, casein, gum arabic, etc.
carboxymethylcellulose, polyvinyl alcohol,
Adhesives such as styrene-butadiene copolymer latex, vinyl acetate latex or acrylic ester latex, inorganic fillers such as zinc oxide, magnesium oxide, titanium oxide, aluminum hydroxide, calcium carbonate, magnesium carbonate or calcium sulfate; A coating liquid for forming a color developer layer is prepared by adding various other auxiliary agents as appropriate.

Then, the developer coating solution prepared in this way is coated on high-quality paper using a conventional coating device such as an air knife coater, blade coater, roll coater, size press coater, curtain coater or short dwell coater.
Coated on a support such as coated paper, synthetic paper or film,
Finished as developer paper for pressure-sensitive copying paper.

"Example" The present invention will be described in more detail with reference to Examples below, but it is of course not limited to these.

In addition, "parts" and "%J" in the examples represent "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 3.5-di(α
85 g of zinc salt of salicylic acid (methylhensyl), styrene/α-methylstyrene copolymer (average molecular weight: 1.
2 (10) Prepare 15 g and toluene Bog,
After mixing and dissolving, 15 g of titanium dioxide was further mixed and dispersed. To this dispersion, add acrylamide copolymer (butyl acrylate/acrylic acid/acrylamide = 7/3/
After adding 1180 g of water-soluble i'ff containing 4 g of 90 mol%) and 0.2 g of sodium carbonate, the mixture was heated at 45°C at 10.0 g per minute using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.; Model M).
(The emulsified dispersion was emulsified and dispersed for 15 minutes at 100 rotations.The emulsified dispersion was transferred to a hard glass three-neck flask with an internal volume of 101 (10O), and 50g of water was added, and the flask was heated while stirring slowly to distill the dispersion. Toluene and water were distilled out from the mouth. During this time, the internal temperature of the flask changed from 80°C to 10°C. The total distilled amount of toluene and water decreased to 1
When the weight reached 30 g, heating was stopped and the contents were cooled.

Note that distillation required about 5 hours.

The contents were an aqueous color developer dispersion containing approximately 46% non-volatile components and having a dispersed phase with an average particle size of 0.8 microns.

Example 2 Zinc 3,5-di(α-methylhensyl)salicylate powder 9 (10 g) containing 50 g of water, 150 g of styrene/α-methylstyrene copolymer powder, and 150 g of titanium dioxide
150 g of this powder was kneaded in a 1-inch double-screw extruder heated to 180° C. so that the average residence time was 30 seconds. The extruded strands were cooled in air, and powder 1 (10 g) obtained by crushing into approximately 3 (10 meshes) and an aqueous solution 4 (10 g) containing 4 g of acrylamide copolymer and 0.2 g of sodium carbonate were prepared.
, and glass beads 5 (10 m1 in diameter) with internal volume 101 (10 O pot-type sand mill (manufactured by Igarashi Machine Manufacturing Co., Ltd.; model TSG 4H) with a cooling jacket)
2.3 (10 revolutions per minute) while passing brine at -15°C through the cooling jacket, rotating intermittently, being careful not to overheat the contents, and increasing the total rotation time. Wet pulverization was carried out for 20 minutes.The glass beads were removed to obtain an aqueous developer dispersion containing about 30% of non-volatile components and having an average particle size of 1.9μ.

Example 3 Fine powder 1 of zinc 3-isododecylsalicylate (10 g,
15 g of titanium dioxide and 80 g of toluene were mixed and dissolved. To the obtained solution, 150 g of an aqueous solution containing 4 g of acrylamide copolymer and 0.2 g of sodium carbonate was added,
The mixture was emulsified and dispersed using a homomixer at 45°C for 15 minutes at a rotation speed of 10 (100) times per minute.

Thereafter, the non-volatile components were removed by treatment in exactly the same manner as in Example 1.
An aqueous developer dispersion containing 0% of color developer and having an average particle size of 0.7 μm was obtained.

Example 4 180 g of zinc 3,5-di(α-methylbenzyl)salicylate powder containing 10 g of water, 30 g of styrene/α-methylstyrene copolymer powder, 30 g of titanium dioxide,
70 g of Hensen and 70 g of ethanol were charged into a three-necked flask with an internal volume of 5 (10 ml) equipped with a stirrer, a thermometer, and a reflux condenser.

The flask was heated while the contents were stirred relatively vigorously until the contents slightly boiled. After maintaining this condition for about 3 hours, the contents were transferred to a stainless steel hunt and vacuum dried. Final temperature of vacuum drying is 130°C1
The vacuum level was 20 torr and the test was carried out for 2 hours. After cooling, this was pulverized into 3 (10) meshes, and then subjected to wet pulverization treatment in the same manner as in Example 2 to form a color developer aqueous dispersion with a non-volatile component content of approximately 30% and an average particle size of 2.5μ. Obtained.

Comparative Example 1 The same procedure as in Example 1 was carried out except that titanium dioxide was not added, and a water dispersion of a color developer with a non-volatile component of about 46% and an average particle size of the dispersed phase of 0.9 microns was carried out. I got the liquid.

Comparative Example 2 The same procedure as in Example 2 was carried out except that titanium dioxide was not used to obtain an aqueous developer dispersion containing approximately 30% non-volatile components and an average particle size of 1.9μ. .

Comparative Example 3 The method of Example 3 was followed except that titanium dioxide was not used, except that the non-volatile components were reduced to about 50%.
An aqueous developer dispersion having an average particle size of 0.6 μm was obtained.

Comparative Example 4 The same procedure as in Example 4 was carried out except that titanium dioxide was not used to obtain an aqueous color developer dispersion containing about 30% of nonvolatile components and having an average particle size of 2.6 μm.

Nobino・
The amount of zinc 3.5-di(α-methylbenzyl)salicylate or zinc 3-itodecylsalicylate in the aqueous developer dispersions obtained in Examples 1 to 4 and Comparative Examples 1 to 4 corresponds to 10 parts. Mix and disperse 90 parts of calcium carbonate and 1 part of water, then use 10% polyvinyl alcohol aqueous solution (10 parts) as a binder, carboxyl-modified SBR latex with solid content of 50% (product name: 5N-307, Resident Naugatack) Eight types of developer coating liquids (Examples 1 to 4 and Comparative Examples 1 to 4) were prepared by mixing and dispersing 20 parts of Co., Ltd.).

Furthermore, for comparison, the color developer aqueous dispersion obtained in Comparative Example 1 (
Solid content: 46%) 22 parts, calcium carbonate 80 parts, titanium dioxide 10 parts, water 1 (10 parts), 10% polyvinyl alcohol aqueous solution 1 (10 parts), and 20 parts of carboxyl-modified SBR latte 7 lath with solid content 50% A developer coating solution (Comparative Example 5) was prepared by mixing and dispersing.

The resulting coating solution was applied to one side of 40 g/n base paper so that 0.4 g/rd of zinc salt of nuclear-substituted salicylic acid was deposited and dried to obtain nine types of developer paper for pressure-sensitive copying paper. .

A microcapsule coating liquid prepared by dissolving crystal violet lactone in alkylnaphthalene and microcapsulating this oily liquid was applied to one side of base paper with a dry weight of 4.
A top paper was obtained by coating and drying so as to give g/rd.

The coated surfaces of the main and fold color developing paper and the top paper were placed opposite each other, and the color was developed using a drop-type color tester (weight: 150 g, height: 20 cm), and the color density was determined by MacHess reflection 1 hour after pressing. It was measured using a densitometer and the results are shown in Table 1. (The larger the number, the better the color development.) Layer the developer paper and the upper paper so that the coated sides face each other, and apply a load of 1 (10 kg/cTil) to develop a color image. was formed, and the color density was measured using a Maches reflection densitometer, and the value was set as Do.Next, after exposing this color developer paper to sunlight for 6 hours, the color density of the color image was measured again, and the value was set as Dl. And so.

The light resistance (colored area) was determined using the following formula, and the results are shown in Table 1. The closer the value is to 1 (10, the better the light resistance is).

Lightfastness (colored part) = X1 (109
′.

After exposing the color developer paper to sunlight for 6 hours, stack the upper paper and coated side facing each other, apply a load of 1 (10 kg/ci) to form a color image, and measure the color density using a Maches reflection densitometer. It was measured and the value was designated as D3.

In addition, the developer paper and the upper paper that had not been exposed to sunlight were stacked so that the coated sides were facing each other, and 1 (10 kg/c+
A colored image was formed by applying a load of fl, and the color density was measured using a Machhes reflection densitometer, and the value was defined as D2.

The light resistance (blank area) was determined using the following formula, and the results are listed in Table 1. The closer the value is to 1 (10), the better the light resistance is.

"Effect" As is clear from the results in Table 1, a color developer paper for pressure-sensitive copying paper using a color developer obtained by mixing and heating a zinc salt of nuclear-substituted salicylic acid and titanium dioxide by the method of the present invention. was an excellent color developing paper with significantly improved light fastness without impairing color development.

Claims (11)

[Claims] (1) A zinc salt of a nuclear-substituted salicylic acid having at least one hydrocarbon substituent and a total number of carbon atoms of those substituents of 8 or more is mixed and heat-treated with titanium dioxide. A method for producing a color developer for pressure-sensitive copying paper. (2) A zinc salt of a nuclear-substituted salicylic acid having at least one hydrocarbon substituent and the total number of carbon atoms in the substituents is 8 or more and titanium dioxide are mixed in the presence of water or an organic solvent. A method for producing a color developer for pressure-sensitive copying paper, which comprises heat treatment. (3) A zinc salt of a nuclear-substituted salicylic acid having at least one hydrocarbon substituent and a total of 8 or more carbon atoms in those substituents and titanium dioxide are mixed in the presence of water or an organic solvent. A method for producing a color developer for pressure-sensitive copying paper, which comprises removing water or an organic solvent while performing a heat treatment. (4) A zinc salt of a nuclear-substituted salicylic acid having at least one hydrocarbon substituent and a total number of carbon atoms of those substituents of 8 or more, and titanium dioxide in the presence of water, a dispersant, and an organic solvent. A method for producing a color developer for pressure-sensitive copying paper, which comprises emulsifying and dispersing the color developer into a liquid, followed by heat treatment. (5) A zinc salt of a nuclear-substituted salicylic acid having at least one hydrocarbon substituent and the total number of carbon atoms of those substituents is 8 or more, and titanium dioxide in the presence of water, a dispersant, and an organic solvent. 1. A method for producing a color developer for pressure-sensitive copying paper, which comprises emulsifying and dispersing the color developer into a liquid, followed by heat treatment to remove water and an organic solvent. (6) An organic solvent, titanium dioxide, and a water-soluble zinc salt are added to an aqueous solution of an alkali metal salt of a nuclear-substituted salicylic acid having at least one hydrocarbon substituent and the total number of carbon atoms of those substituents is 8 or more. Add an aqueous solution of and perform metathesis with or without heating, separate the generated organic layer containing the zinc salt of the nuclear substituted salicylic acid and titanium dioxide, add water and a dispersant to this, emulsify and disperse, A method for producing a color developer for pressure-sensitive copying paper, the method comprising: subsequent heat treatment. (7) An organic solvent, titanium dioxide, and a water-soluble zinc salt are added to an aqueous solution of an alkali metal salt of a nuclear-substituted salicylic acid having at least one hydrocarbon substituent and the total number of carbon atoms of the substituents is 8 or more. Add an aqueous solution of and perform metathesis with or without heating, separate the generated organic layer containing the zinc salt of the nuclear substituted salicylic acid and titanium dioxide, add water and a dispersant to this, emulsify and disperse, A method for producing a color developer for pressure-sensitive copying paper, which comprises removing water and an organic solvent while subsequently performing a heat treatment. (8) Claim (1) wherein the heat treatment temperature is 40 to 220°C.
) to (7), the method for producing a color developer for pressure-sensitive copying paper. (9) The method for producing a color developer for pressure-sensitive copying paper according to any one of claims (1) to (8), wherein the nuclear-substituted salicylic acid is 3,5-di(α-methylbenzyl)salicylic acid. (10) The method for producing a color developer for pressure-sensitive copying paper according to any one of claims (1) to (8), wherein the nuclear-substituted salicylic acid is 3-isododecylsalicylic acid. (11) Pressure-sensitive copying paper obtained by coating a support with a coating liquid containing a color developer for pressure-sensitive copying paper obtained by the manufacturing method according to claims (1) to (10).