JPH0248983A - Pressure-sensitive recording sheet - Google Patents

Abstract

PURPOSE:To enhance light fastness of a coloring material by providing on a support an electron-acceptive color developer layer comprising a metallic salt of a specified salicylic acid derivative, calcium carbonate with a specified particle diameter and a specified binder in respectively specified amounts. CONSTITUTION:An electron-acceptive color developer layer for forming a color by a reaction of a substantially colorless electron-donative dye with an electron- acceptive color developer is provided on a support to produce a pressure- sensitive recording sheet. The color developer layer comprises (a) a metallic salt of a salicylic acid derivative of formula I (each of R11 to R14 is H or an alkyl) as the color developer, (b) calcium carbonate with an average particle diameter of not more than 5.0mum as a pigment in an amount of at least 50wt.% based on the total amount of pigments, with the amounts of the color developer and the pigment being in a weight ratio of from 1:5 to 1:15, and (c) a carboxy- modified styrene-butadiene latex and a water-soluble high molecular weight compound in a weight ratio of from 50:50 to 25:75.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pressure-sensitive recording sheet. More specifically, a nearly colorless electron-donating dye precursor (hereinafter referred to as a color former).
The present invention relates to a pressure-sensitive recording sheet that obtains a colored image by a reaction between the present invention and an electron-accepting color developer (hereinafter referred to as a color developer).

(Prior art) Color-forming agents and developers, such as clay materials such as acid clay, activated clay, acpulgite, zeolite, bentonite, and kaolin, metal salts of aromatic carboxylic acids, and phenol-formaldehyde resins, have been conventionally used in color-forming reactions. Pressure-sensitive recording materials using
No. 05.470, No. 2,505,489, No. 2. 5
50. No. 471, No. 2,548,366, No. 2,7
12゜507, 2,730,456, 2.73
1ff No. 0.457, No. 3,418,250, Japanese Unexamined Patent Publication No. 1973-
No. 28,411, JP-A-50-44,009, etc.

The properties that a pressure-sensitive recording sheet should have are: 1) less deterioration in color developing ability over time;

2) The coloring body has excellent light resistance.

3) There is little yellowing of the developing surface when exposed to light.

4) The colored body has excellent water resistance and plasticizer resistance.

5) Less yellowing of the developing surface due to nitrogen oxides in the air.

etc. can be mentioned.

Among currently known color developers, metal salts of aromatic carboxylic acids show the best performance. However, among the above performances, the light resistance of the color former and the yellowing of the color developing surface due to light are limited. , it is still not sufficient when exposed to sunlight etc. for a long time.

(Objective of the Invention) An object of the present invention is to provide a pressure-sensitive recording sheet in which the coloring material has excellent light resistance and yellowing of the color-developing surface due to light is small.

(Structure of the Invention) The object of the present invention is that the electron-accepting color developer layer has (a) the general formula (
Contains a metal salt of a salicylic acid derivative shown in 1),
b) [Calcium carbonate with an average particle size of 5.0μ or less is used as a material in an amount of 60% by weight or more of the total pigment, and the ratio of color developer to pigment is 1:5 to 1:15 by weight. and
(C) Carboxy-modified styrene-butadiene latex and water-soluble polymer as a binder in a weight ratio of 50:50
This was achieved with a pressure-sensitive recording sheet characterized in that it is used in a ratio of ~25:75.

H1? +3 In the above general formula (1), RII%R1! , RI3, and R14, hydrogen atoms and alkyl groups having 1 to 22 carbon atoms are preferred;
In particular, a tertiary alkyl group having 4 to 18 carbon atoms is preferred.

Specific examples of the group represented by R++sR+t, R13, and R14 include a hydrogen atom, a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a t-octyl group, a t-nonyl group, a t-amyl group, Examples include t-dodecyl group, cyclohexyl group, cyclohexylcyclohexyl group, butyl group, hexyl group, octyl group, decyl group, dodecyl group, octadecyl group, hexadecyl group, and the like.

The salicylic acid derivative according to the present invention preferably has a total of 13 or more carbon atoms, particularly preferably 19 or more carbon atoms, from the viewpoint of water insolubility.

The metals that make metal salts with the above salicylic acid derivatives include:
Examples include aluminum, calcium, chromium, manganese, iron, cobalt, nickel, copper, barium, zinc, etc. Among these, preferred are zinc, aluminum,
Calcium and nickel are preferred, and zinc is particularly preferred.

Specific examples of salicylic acid derivatives according to the present invention are shown below, but the present invention is not limited thereto.

3.5-dicyclopentagenylsalicylic acid, 35-di-t-octylsalicylic acid, 3.5-bis-1-hexylsalicylic acid, 5-t-octylsalicylic acid, 5-t-
Nonylsalicylic acid, 5-t-dodecylsalicylic acid, 5-
Octadecylsalicylic acid, 3.5-bis-t-nonylsalicylic acid, 35-bis-t-dodecylsalicylic acid, 5-
Zinc salts, nickel salts, aluminum salts, calcium salts, etc., such as cyclohexylcyclohexylsalicylic acid, etc. may be used.In addition, in the pressure-sensitive recording sheet according to the present invention, phenol derivatives, aromatic Metal salts of carboxylic acids of the genus, novolak resins, metal-treated novolak resins, metal complexes, and the like may be used in combination.

Examples of these are Special Publication No. 9309 of 1972 and Special Publication No. 1 of 1973.
No. 4039, JP-A-52-140483, JP-A-48
-51510, JP-A-57-210886, JP-A-58-87089, JP-A-59-11286, JP-A-60-176795, JP-A-61-95988, etc.

Examples of the pigment used in the present invention include zinc oxide, aluminum hydroxide, calcium carbonate, titanium oxide, magnesium carbonate, magnesium oxide, barium sulfate, kaolin, activated clay, and talc.

In the present invention, the pigment has an average particle size of 5. Calcium carbonate of 0 μ or less is used in an amount of 60% by weight or more of the total pigment. If the amount of calcium carbonate used is less than 60% by weight, sufficient performance in terms of light resistance of the color former and yellowing of the color developing surface due to light cannot be obtained.

In addition, sufficient color developing ability cannot be obtained unless calcium carbonate with an average particle size of 5.0μ or less is used.
Calcium carbonate with a particle size of less than μ is commercially available, such as Br1lliant-15 and Br1llia manufactured by Shiraishi Kogyo.
nt-S 15, Br1lliant-30, PC
.

Examples include P CX and Unibur-70.

In the present invention, the color developer and pigment are used in a weight ratio of 1:5 to 1:15. If the ratio of R material used is higher or lower than this, sufficient color developing ability cannot be obtained.

The color developer and pigment are mechanically dispersed in an aqueous system using a ball mill, attritor, sand mill, etc. together with a dispersant, a water-soluble polymer, and other additives to obtain a dispersion. It is also possible to use an emulsion in which the colorant is dissolved in a battering machine solvent and emulsified in water.

The thus obtained dispersion or emulsion is coated on a support with the addition of a binder.

The final amount of developer applied to the support was 0.1g/
n? ~2. Og/rd, preferably 0.2g/n (~
1°Og/- is appropriate.

In the present invention, as a binder, carboxy-modified styrene-butadiene latex and water-soluble polymer are used in a weight ratio of 50
: Use in a ratio of 50-25-75.

The carboxy-modified styrene-butadiene latex is preferably one modified with an unsaturated acid, particularly an acid such as acrylic acid, methacrylic acid, maleic acid, or itaconic acid.

Examples of water-soluble polymers include synthetic or natural polymers such as polyvinyl alcohol, maleic anhydride-isobutylene copolymer, carboxymethyl cellulose, hydroxyethyl cellulose, polyacrylamide, polyacrylic acid, polyvinylpyrrolidone, starch, casein, gum arabic, and gelatin. Substances can be used.

When the usage ratio of carboxy-modified styrene-butadiene latex is higher than 50, the light resistance of the color former and the yellowing of the color developing surface due to light deteriorate. Moreover, when the usage ratio of carboxy-modified styrene-butadiene latex is lower than 25, the water resistance of the color developing surface deteriorates.

The color former that reacts with the color developer used in the pressure-sensitive recording sheet of the present invention is not particularly limited, but specific examples of these color formers include triphenylmethane phthalide compounds, fluoran compounds, and phenothiazine. system compounds,
Examples include indolylphthalide compounds, indolyl azaphthalide compounds, leucoauramine compounds, rhodamine lactam compounds, triphenylmethane compounds, triazene compounds, and spiropyran compounds.

The color former is dissolved in a solvent, encapsulated, and applied to a support.

As a solvent, natural or synthetic oils can be used alone or in combination. ? Examples of the nine solvents include cottonseed oil, kerosene, paraffin, naphthenic oil, alkylated biphenyls, alkylated terphels, chlorinated paraffins, alkylated naphculenes, diphenylalkanes, and the like.

As a method for manufacturing the color former-containing microcapsules, an interfacial polymerization method, an internal polymerization method, a phase separation method, an external polymerization method, a core cell basis method, etc. are used.

A water-soluble binder or a latex-based binder is generally used to prepare a coating solution containing microcapsules for colored mesh. Further, a capsule protectant such as cellulose powder, starch particles, RILKU, etc. is added to obtain a color former-containing microcapsule coating liquid.

The performance of the color developer sheet for pressure-sensitive recording of the present invention was tested using the following coloring mesh as a microcapsule sheet.

[Preparation of color former-containing microcapsule sheet] 5 parts of a partial sodium salt of polyvinylbenzenesulfonic acid (manufactured by Nasinal Starch Co., Ltd., νER5A, T L500, average molecular weight 1,500,000) was stirred in 95 parts of hot water at about 80°C. Add and dissolve while stirring.

After dissolving for about 30 minutes, it is cooled. The pH of the aqueous solution is 2~
3, and a 20% by weight aqueous sodium hydroxide solution was added thereto to adjust the pH to 4.0. On the other hand, diisopropylnaphthalene 10 in which 2.5% crystal violet lactone and 1.0% hendyl leucomethylene blue were dissolved.
0 part was emulsified and dispersed in 100 parts of a 5% aqueous solution of a partial sodium salt of the polyvinylbenzenesulfonic acid to obtain an average diameter of 4.
An emulsion with a particle size of 5 μm was obtained. Separately, 6 parts of melamine, 11 parts of 37% by weight formaldehyde aqueous solution, 3 parts of water
0 part was heated to 60° C. and stirred, and after 30 minutes, a transparent mixed aqueous solution of melamine, formaldehyde, and melamine formaldehyde initial 3tlI condensate was obtained. The pH of this mixed aqueous solution was 6-8.

Below, this melamine, formaldehyde and melamine-
The mixed aqueous solution of the formaldehyde initial condensate is referred to as an initial condensate solution. The first jJ] condensate solution obtained by the above method was added to and mixed with the above emulsion, and the pH was adjusted to 6.0 with 3.6% by weight hydrochloric acid solution while stirring, and the liquid temperature was raised to 65°C. Stirring was continued for 360 minutes. The capsule liquid was cooled to room temperature and adjusted to pH 9.0 with 20% by weight sodium hydroxide.

To this capsule dispersion, 200 parts of a 10% by weight polyvinyl alcohol aqueous solution and 50 parts of starch particles were added, and water was added to adjust the solid content concentration to 20% to prepare a color former-containing microcapsule coating liquid.

This coating liquid was applied to a base paper of 50 g/rrl using an air knife coater so that the solid content was 5 g/m, and dried to obtain a color former-containing microcapsule sheet.

The color developer sheet for pressure-sensitive recording of the present invention will be specifically explained below with reference to Examples, but it is not limited to these Examples.

(Examples of the invention) Example 1-1 [Preparation of dispersion liquid] 15 parts of zinc 3.5-zyl-t-octylsalicylate, calcium carbonate (manufactured by Shiraishi Kogyo, Brllliant-15
, average particle size 0. 5μ) 120 parts, activated clay 10 parts, zinc oxide 20 parts, sodium hexametaphosphate 1 part and water 2
Using a sand grinder, use 00 parts to uniformly disperse the particles to an average particle size of 3μ. (A) was obtained.

[Adjustment of coating liquid]

To 300 parts of dispersion liquid (A) were added 7 parts (as solid content) of 10% PVA-117 (manufactured by Kuraray) water-soluble i & 100 parts carboxy-modified SBR latex (manufactured by Sumitomo Nogatafuku, 5N-307) (as solid content), and the solid content concentration was 20. %, and a coating liquid was obtained.

[Application of color developer sheet]

This coating liquid was applied to a 50 g/ITr base paper using an air knife coater so that the solid content was 5.0 g/rd, and dried to obtain a color developer sheet.

Example 1-2 Example except that 15 parts of zinc 5-t-dodecylsalicylate was used instead of 15 parts of zinc 3.5-di-t-octylsalicylate in [Preparation of dispersion] in Example ri. ! -1
A developer sheet was obtained in the same manner as above.

Example 1-3 Same as Example 1-1 except that 15 parts of zinc 5-cyclohexylcyclohexylsalicylate was used instead of 15 parts of zinc 3,5-di-1-octylsalicylate in [Preparation of dispersion liquid]. A developer sheet was obtained in the same manner as in Example 1-1.

Example I-4 Example! Example 1-1 except that 15 parts of zinc 5-t-octylsalicylate was used in place of 15 parts of zinc 3,5-di[-octylsalicylate] in [Preparation of dispersion] in -1.
A developer sheet was obtained in the same manner as above.

Example r5 In [Preparation of dispersion] in Example 1-1, 3.5-di[
- 10 parts of zinc octylsalicylate and 3,5-bis(α
A color developer sheet was obtained in the same manner as in Example r-1 except that 5 parts of zinc (~methylbenzyl) salicylate was used.

Comparative Example 1-1 3.5-bis(
Example except that 15 parts of zinc α-methylbenzyl) salicylate was used! A developer sheet was obtained in the same manner as in -1.

Comparative Example 1-2 Example 1-1 except that 15 parts of p-phenylphenol formaldehyde resin was used instead of 15 parts of zinc 3.5-zyl-t-octylsalicylate in [dispersion preparation] of Example 1-1. A developer sheet was obtained in the same manner as in 1.

Example n-1 [Preparation of dispersion liquid] 15 parts of zinc 3.5-di-t-octylsalicylate, 1 part of calcium carbonate (Shiraishi Kogyo type, PC1 average particle size 3.2μ)
20 parts of kaolin, 20 parts of zinc oxide, 1 part of sodium hexametaphosphate, and 200 parts of water were uniformly dispersed using a sand grinder to give an average particle size of 3 μm to obtain a dispersion (B).

[Adjustment of coating liquid]

100 parts of a 10% PVA-117 (manufactured by Kuraray) aqueous solution and 5 parts (as solid content) of carboxy-modified SBR latex (manufactured by Sumitomo Noga Tank, 5N-307) were added to 300 parts of dispersion liquid (B), so that the solid content concentration was 20. %, and a coating liquid was obtained.

[Application of color developer sheet]

Apply this coating liquid to 50 g/rrr (7) of base paper. 0g/r
tr(D) was coated with an air knife coater so that the solid content was coated, and dried to obtain a color developer sheet.

Comparative Example nt [Preparation of dispersion liquid] 15 parts of zinc 3.5-di-t-octylsalicylate, calcium carbonate (Shiraishi Kogyo type, pc, average particle size 3.2μ) 6
0 parts, 80 parts of kaolin, 20 parts of zinc oxide, 1 part of sodium hexametaphosphate, and 200 parts of water were uniformly dispersed using a sand grinder so that the average particle size was 3 μm to obtain a dispersion liquid (C).

[Adjustment of coating liquid]

100 parts of a 10% PVA-117 (manufactured by Kuraray) aqueous solution and 5 parts (as solid content) of carboxy-modified SBR latex (manufactured by Sumitomo Nogatank, 5N-307) were added to 300 parts of dispersion liquid (C), so that the solid content concentration was 20. %, and a coating liquid was obtained.

[Application of color developer sheet]

Apply this coating liquid to 50 g/rrr (7) of base paper. 0g/r
d (D) was coated with an air knife coater so that the solid content was coated, and dried to obtain a color developer sheet.

Comparative Example U-2 [Adjustment of coating liquid] 10% to 300 parts of the dispersion (B) obtained in Example n-1
50 parts of PVA-117 (manufactured by Kuraray) aqueous solution and carboxy-modified SBR latex (manufactured by Sumitomo Naugatac, 5N-3)
07) Added 10 parts (as solid content) and adjusted water so that the solid content concentration was 20% to obtain a coating liquid.

[Application of color developer sheet]

This coating liquid was applied to 508/ffl base paper using an air knife coater so that the solid content was 5.0 g/m.
It was dried to obtain a color developer sheet.

An evaluation test was conducted on the combination of each of the above color developer sheets and color former-containing microcapsule sheets as an angry pressure recording sheet, and the results are listed in Table 1. The evaluation test was conducted using the following method.

+11 Color development density test The microcapsule layer of the color former-containing microcapsule sheet was placed on the developer sheet, and a load of 300 g/d was applied to develop color. After leaving this in a dark place for 24 hours, the spectral absorption curve of the chromophore in the wavelength range of 380 to 780 nm was measured, and the concentration at the maximum absorption (fresh concentration Do) was determined.
was measured.

(2) Light resistance test of coloring material After leaving it for 24 hours in a dark place obtained in (1), the coloring material was measured using a xenon fetometer (FAL-25AX-HC).
After 8 hours of irradiation with the "Hitachi Color Analyzer Model 307" (manufactured by Suga Test Instruments), the spectral absorption curve of the color former was measured, and the density at the absorption maximum was measured. e1 (manufactured by Hitachi, Ltd.).The value indicating light resistance (light resistance value) was calculated using the following formula.

(3) Yellowing test of the color developing surface due to light The color developing surface of the color developer sheet was
After 16 hours of irradiation with X-) (Type C)'' (manufactured by Suga Test Instruments), the reflection density (yellow) of the developing surface was measured with a densitometer (Macbeth, Model RD514).

Table 1 *The larger the light fastness value, the better the light fastness of the color former.

As shown in Table 1, it can be seen that the color developer sheet of the present invention has excellent light resistance of the color forming body compared to the comparative color developer sheet, and yellowing of the color developing surface due to light is less.

Claims (1)

[Scope of Claims] In a pressure-sensitive recording sheet that obtains a colored image by a reaction between an almost colorless electron-donating dye and an electron-accepting color developer, the electron-accepting color developer layer comprises (a) a color developer; , contains a metal salt of a salicylic acid derivative represented by the general formula (I), (b) uses calcium carbonate with an average particle size of 5.0 μ or less in an amount of 60% by weight or more of the total pigment as a pigment, and contains a color developer and The usage ratio with the pigment is 1:5 to 1:15 by weight, and (c)
The weight ratio of carboxy-modified styrene-butadiene latex and water-soluble polymer as a binder is 50:50 to 25.
:A pressure-sensitive recording sheet characterized by being used at a ratio of 75. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the above formula, R_1_1, R_1_2, R_1_3, R_
1_4 represents a hydrogen atom or an alkyl group. )