JPH06179286A - Pressure-sensitive recording sheet - Google Patents

Abstract

PURPOSE:To enable the reading of an optical character using near infrared rays by supporting microcapsules containing a specific electron donating colorless paint, an ultraviolet absorber and an electron acceptive compd. on a support. CONSTITUTION:A predetermined amt. of an electron donating compd. represented by formula I (wherein R1-R4 are H, a 1-8C alkyl group or a 5-7C cycloalkyl group, R5 and R6 are a 1-4C alkyl group or an alkoxy group, R7 and R8 are H or a 1-4C alkyl group and X is -CH- or N) and a predetermined amt. of an ultraviolet absorber such as a benzotriazole compd. are dissolved in a solvent and the resulting soln. is microencapsulated. The obtained microcapsules are applied to a support such as paper or a plastic sheet and dried to produce a colorant sheet. An electron acceptive compd. is dispersed in a binder such as polyvinyl alcohol to be applied to a support and dried to form a developer sheet. Both sheets are combined to obtain a thermal recording sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive recording sheet,
In particular, it relates to a pressure-sensitive recording sheet suitable for reading optical characters.

[0002]

2. Description of the Related Art Recently, with the development of optical character reading devices (OCR) and bar code reading devices using near infrared rays, optical character reading has come to be applied to pressure-sensitive recording sheets and the like. However, in the case of the conventional pressure-sensitive recording sheet, the optical character reading is performed only on the characters written on the upper leaf paper, and not on the characters formed by breaking the microcapsules.

By the way, as a color former capable of forming a dye having absorption in the near infrared region, JP-B-58-5940, JP-A-60-230890 and JP-A-59-199757.
Various dyes are proposed in each publication, and if these are used,
It is possible to read the characters on all papers (up to 5 to 6) of the pressure-sensitive recording sheet with an optical character reader, but these dyes may be colored yellow, fog on the background, poor color development, etc. There was a problem and it was not suitable for practical use.

[0004]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a pressure-sensitive recording sheet which can be read by an optical character reader using near-infrared rays with respect to characters on all papers without being decomposed even when the microcapsule paper is exposed to light. To provide.

[0005]

As a result of various studies, the present inventor has found that the above object can be achieved by the present invention described below.

That is, according to the present invention, in a pressure-sensitive recording sheet for obtaining a color image by the reaction of an almost colorless electron-donating dye and an electron-accepting compound, the compound represented by the general formula (1) and the ultraviolet absorption are contained in microcapsules. A pressure-sensitive recording sheet containing an agent. General formula (1)

[0007]

[Chemical 2]

Where R₁ ~ R_FourAre the same or different
Also, hydrogen atom and alkyl having 1 to 8 carbons respectively
Group, C5-7 cycloalkyl group, C1-4
An alkyl group having 7 to 20 carbon atoms, which may be substituted with an alkyl group.
Ralalkyl group and C1-C4 alkyl group, C1-C1
4 alkoxy group or substituted amino group having 1 to 20 carbon atoms
An aryl group having 6 to 26 carbon atoms which may be substituted with
Represent, R₁ And R₂ And R₃And R_FourAre bound to each other
A 7-membered ring may be formed. R_FiveAnd R₆Are the same but different
Which may have an alkyl group having 1 to 4 carbon atoms,
C1-C4 alkoxy group, C1-C4 alkyl
Represents a thio group and a halogen atom. R₇And R ₈Are the same
May be different from each other, and each is a hydrogen atom or a carbon number 1 to
4 alkyl group, 1-8 carbon alkoxy group, carbon number
It represents an alkylthio group of 1 to 4 and a halogen atom. X is
It represents a -CH- group and a nitrogen atom.

In the general formula (1), among the substituents represented by R _{1 to} R ₄ , a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkyl group having 1 to 4 carbon atoms or 1 carbon atom To an alkoxy group having 4 to 4 and an aryl group having 6 to 24 carbon atoms which may be substituted with a substituted amino group having 1 to 18 carbon atoms, R ₁
When R and R ₂ and R ₃ and R ₄ form a ring, a 5- or 6-membered ring is preferable. The substituted amino group here means an alkylamino group, a phenylamino group, a dialkylamino group, a diphenylamino group, or an N-alkyl-N-phenylamino group. These substituents may further have a substituent. Specifically, among R _{1 to} R ₄ , hydrogen atom, methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group, phenyl group, 4-methylphenyl group, 4-methoxyphenyl group, 4 -Dimethylaminophenyl group, 4
-Diethylaminophenyl group and 4-diphenylaminophenyl group are preferred. When R ₁ and R ₂ and R ₃ and R ₄ form a ring, (R ₁ ) (R ₂ ) N-, (R ₃ ).
As (R ₄ ) N-, a 1-pyridinyl group and a piperidino group are preferable. Of R ₅ and R _6, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a methylthio group, an ethylthio group, a fluorine atom and a chlorine atom are preferable. Hydrogen atom among R ₇ and R ₈ , a methyl group, an ethyl group, a methoxy group, an ethoxy group,
A methylthio group, an ethylthio group, a fluorine atom and a chlorine atom are preferable.

Specific examples of preferred compounds represented by formula (1) are shown below, but the invention is not limited thereto.

[0011]

[Chemical 3]

[0012]

[Chemical 4]

[0013]

[Chemical 5]

[0014]

[Chemical 6]

[0015]

[Chemical 7]

[0016]

[Chemical 8]

Preferred as the ultraviolet absorber used in the present invention are benzophenone type ultraviolet absorbers, benzotriazole type ultraviolet absorbers, salicylic acid type ultraviolet absorbers,
Examples thereof include cyanoacrylate-based UV absorbers and oxalic acid anilide UV absorbers. Examples of these are JP-A-58-212844 and 59-46646.
No. 59-109055, JP-B-36-10466
No. 42, No. 42-18787, No. 48-5496, No. 4
8-41572, U.S. Pat. No. 3,754,919,
No. 4,220,711, Japanese Patent Publication No. 48-31255,
No. 50-10726, U.S. Pat. No. 2,719,086.
No. 3,707,375, Japanese Patent Publication No. 48-30492
JP-A-47-10537 and JP-A-58-111942.
No. 59-19925, No. 63-53544, and the like.

Specific examples of the benzophenone type ultraviolet absorber include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2
-Hydroxy-4-methoxy-5-sulfobenzophenone and the like can be mentioned.

Specific examples of benzotriazole type ultraviolet absorbers
An example is 2- (2'-hydroxy-5'-methylphenyl).
Phenyl) benzotriazole, 2- (2'-hydroxy)
-5 ^,-T-butylphenyl) benzotriazole, 2
-(2'-hydroxy-3 ', 5'-di-t-butylphen
Phenyl) benzotriazole, 2- (2'-hydroxy)
-3'-t-butyl-5'-methylphenyl) -5-ku
Lolobenzotriazole, 2- (2'-hydroxy-
3 ', 5'-di-t-amylphenyl) benzotriazo
2- (2'-hydroxy-4'-octyloxy
Phenyl) benzotriazole, 5-chloro-2-
[2'-hydroxy-3'-t-butyl-5 '-(2-
Ethylhexyloxycarbonylethyl) phenyl]
Nzotriazole, 5-chloro-2- [2'-hydroxy
Ci-3'-t-butyl-5 '-(octyloxycarbo
Nylethyl) phenyl] benzotriazole, 5-chloro
Ru-2- [2'-hydroxy-3'-t-butyl-5 '
-(Methoxycarbonylethyl) phenyl] benzotri
Examples include azoles.

Specific examples of the salicylic acid type ultraviolet absorber include phenyl salicylate, pt-butylphenyl salicylate, p-octylphenyl salicylate and the like.

Specific examples of the cyanoacrylate type ultraviolet absorber include 2-ethylhexyl-2-cyano-3,
3'-diphenyl acrylate, ethyl-2-cyano-
3,3'-diphenyl acrylate etc. are mentioned.

Particularly preferred among these are benzotriazole type ultraviolet absorbers.

The amount of the ultraviolet absorber used is preferably 5 to 200% by weight, more preferably 10 to 100% by weight, based on the compound of the general formula (2).

In the present invention, when the pressure-sensitive recording sheet is read by an optical character reader and the obtained record is to be read visually, it is preferable to use an electron-donating colorless dye which develops black in combination. A fluoran compound having an anilino group at the 2-position and a substituted amino group at the 6-position is preferred as the black electron-donating colorless dye.

Specific examples of the fluoran compound used in the present invention include US Pat. Nos. 3,624,107 and 3,627,78.
No. 7, No. 3,641, 011, No. 3,462, 828
Issue No. 3,681,390 Issue No. 3,920,510
No. 3,959,571 and the like. Examples of the fluoran compound include, but are not limited to, the following compounds.

2-anilino-3-methyl-6-dimethylaminofluorane, 2-anilino-3-methyl-6-N
-Methyl-N-ethylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N- (iso-propyl) aminofluorane, 2-anilino-3-methyl-6
-N-methyl-N-pentylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N-cyclohexylaminofluorane, 2-anilino-3-methyl-6
-Diethylaminofluorane, 2-anilino-3-chloro-6-dimethylaminofluorane, 2-anilino-3
-Methyl-6-N-ethyl-N-isoamylaminofluorane, 2-anilino-3-methyl-6-N-methyl-
N-isoamylaminofluorane, 2-anilino-3-
Chloro-6-diethylaminofluorane, 2-anilino-3-chloro-6-N-methyl-N-ethylaminofluorane, 2-anilino-3-chloro-6-N-methyl-
N- (iso-propyl) aminofluorane, 2-anilino-3-chloro-6-N-methyl-N-pentylaminofluorane, 2-anilino-3-chloro-6-N-methyl-N-cyclohexylamino Fluorane, 2-anilino-3-methyl-6-N-ethyl-N-pentylaminofluorane, 2-anilino-3-chloro-6-N-ethyl-N-pentylaminofluorane, 2- (p- Methylanilino) -3-methyl-6-dimethylaminofluorane, 2- (p-methylanilino) -3-methyl-6-
Diethylaminofluorane, 2- (p-methylanilino) -3-methyl-6-N-methyl-N-ethylaminofluorane, 2- (p-methylanilino) -3-methyl-6-N-methyl-N- ( iso-propyl) aminofluorane, 2- (p-methylanilino) -3-methyl-
6-N-methyl-N-pentylaminofluorane, 2-
(P-Methylanilino) -3-methyl-6-N-methyl-N-cyclohexylaminofluorane, 2- (p-methylanilino) -3-methyl-6-N-ethyl-N-pentylaminofluorane, 2- (P-methylanilino)
-3-Chloro-6-dimethylaminofluorane, 2-
(P-methylanilino) -3-chloro-6-diethylaminofluorane, 2- (p-methylanilino) -3-chloro-6-N-methyl-N-ethylaminofluorane,
2- (p-methylanilino) -3-chloro-6-N-methyl-N- (iso-propyl) aminofluorane, 2
-(P-methylanilino) -3-chloro-6-N-methyl-N-cyclohexylaminofluorane, 2- (p-
Methylanilino) -3-chloro-6-N-methyl-N-
Pentylaminofluorane, 2- (p-methylanilino) -3-chloro-6-N-ethyl-N-pentylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N-tetrahydrofurfurylamino Fluoran,
There are 2-anilino-3-ethyl-6-N-methyl-N-tetrahydrofurfurylaminofluorane, 2-dibenzylamino-6-diethylaminofluorane and the like.

In the present invention, an electron-donating colorless dye conventionally used can be used in combination with the above-mentioned fluoran compound. Specifically, triphenylmethane phthalide compounds, phenothiazine compounds, indolyl phthalide compounds, leuco auramine compounds, rhodamine lactam compounds, triphenyl methane compounds, triazene compounds, spiropyran compounds, fluorene compounds A compound etc. are mentioned.

Specific examples of phthalides are US Reissue Patent 2
3,024, U.S. Patents 3,491,111, 3,
491, 112, 3, 491, 116 and 3,
509,174, specific examples of spiro dipyrans are US Pat. No. 3,971,808, and specific examples of pyridine-based and pyrazine-based compounds are US Patents 3,775,424, 3,853,869, 4 , 246, 318, and specific examples of fluorenes are described in JP-A-63-94878 and the like.

The electron-accepting compound used in the recording sheet of the present invention includes phenol derivatives, salicylic acid derivatives, metal salts of aromatic carboxylic acids, acid clay, activated clay,
Examples thereof include attabalgite, zeolite, bentonite, kaolin, novolac resin, metal-treated novolac resin, and metal complex. These examples are Japanese Examined Japanese Patent Publication No. 40-930
9, 45-14039, JP-A-52-14048.
No. 3, No. 48-51510, No. 57-210886
No. 58-87089, No. 59-11286, No. 60-176795, No. 61-95988, and the like.

The aspect of the recording sheet of the present invention is described in US Pat.
505, 470, 2, 505, 471, 2, 5
05,489, 2,548,366, 2,71
2,507, 2,730,456, 2,73
0,457, 3,103,404, 3,41
It may take various forms as described in prior patents such as 8,250 and 4,010,038. Most commonly it consists of at least a pair of sheets which separately contain an electron donating colorless dye and an electron accepting compound.

As a method of producing microcapsules, a method utilizing coacervation described in US Pat. Nos. 2,800,457 and 2,800,458, British Patents 867,797 and 950,443 are used. , Same 989,
No. 264, No. 1,091,076 and the like, and the method described in US Pat. No. 3,103,404 and the like. In general, an electron-donating colorless dye is used alone or in a mixture, a solvent (alkylated naphthalene, alkylated diphenyl, alkylated diphenylmethane, alkylated terphenyl, synthetic oil such as chlorinated paraffin, cotton oil, vegetable oil such as castor oil, It is dissolved in animal oil, mineral oil or a mixture thereof, contained in microcapsules, and applied to paper, wood free paper, plastic sheet, resin coated paper, etc. to obtain a color former sheet. The electron-donating colorless dye according to the present invention is compared with conventionally known electron-donating colorless dyes,
It has a characteristic that it is easily dissolved in the solvent used for the microencapsulation described above. Therefore, the density of the electron-donating colorless dye can be increased, and the color density can be improved. Further, the electron-accepting compound and, if necessary, additives are dispersed alone or in a mixture in a binder such as styrene-butadiene latex or polyvinyl alcohol, and together with a pigment, paper, high-quality paper, plastic sheet, resin-coated paper, etc. A developer sheet is obtained by applying.

As the binder, it is preferable to use a carboxy-modified styrene-butadiene latex in combination with a water-soluble polymer from the viewpoint of light resistance and water resistance. Further, as the pigment, it is preferable to use calcium carbonate having an average particle size of 5.0 μ or less in an amount of 60% by weight or more of the total pigment from the viewpoint of color developing ability.

The amount of the electron-donating colorless dye and the electron-accepting compound used depends on the desired coating thickness, pressure-sensitive recording mode, capsule production method, and other conditions, and may be appropriately selected according to the conditions. A person skilled in the art can easily determine this usage amount.

[0034]

EXAMPLE The recording sheet of the present invention was tested for its performance using the following color developing sheet. (1) Preparation of developer sheet To 70 parts of water, 2 parts of zinc oxide, 18 parts of calcium carbonate and 4 parts of zinc 3,5-di-α-methylbenzylsalicylate were added and mixed, and then dispersed by an attritor for 30 minutes. Carboxy modified SBR latex in solid content in the liquid
5 parts and 10 wt% PVA (saponification degree 99% polymerization degree 100
0) 12 parts of an aqueous solution was added and uniformly stirred to obtain a coating solution. This coating solution was coated and dried by an air knife coating machine such that a solid content of 4 g / m ² was coated on a base paper of 50 g / m ² to obtain a developer sheet.

An evaluation test as a pressure-sensitive recording sheet was carried out by combining the above-mentioned color developing sheet and a color-forming agent-containing microcapsule sheet (preparation method will be described later), and the results are shown in Table 1. The evaluation test was performed by the following method.

(2) PCS (Print Control)
Measurement of st Signal) value The microcapsule layer of the color-forming agent-containing microcapsule sheet was overlaid on the color-developing agent sheet, and a load pressure of 300 kg / cm ² was applied to develop the color. After leaving this for 24 hours in a dark place, the reflectance of 380 nm to 1000 nm of the color developing surface was measured with a spectrophotometer (Shimadzu UV-3100). The PCS value is calculated by the following formula.

PCS value = (reflectance of white background−reflectance of color former) / (reflectance of white background)

(3) Light resistance test of microcapsule layer After irradiating the microcapsule layer of the microcapsule sheet containing a color former with a fluorescent lamp fading tester (33,000 lux) for 8 hours, 300 kg / cm ²
Was applied to develop the color. After that, the PCS value was measured in the same manner as in (2). In addition, the degree of coloring of the microcapsule sheet was measured by a densitometer (Macbeth RD9
18 type).

(4) OCR Reading Test The microcapsule layers of the fluorescent lamp-unirradiated and fluorescent lamp-irradiated color-forming agent-containing microcapsule sheets were superposed on the developer sheet, and letters and numbers were printed in OCR-B font. This printed sample was used as an OCR reader (Toshiba V-301
0, using a blue fluorescent lamp).

Example 1-1 A coloring agent was added to 100 parts (weight, the same applies hereinafter) of a 4.4% aqueous solution of a partial sodium salt of polyvinylbenzenesulfonic acid (average molecular weight 500,000) adjusted to pH = 4. Specific example (16) 6 parts, 2
-Anilino-3-methyl-6-N-ethyl-N-isopentylaminofluorane 6 parts, 2-dibenzylamino-
2 parts of 6-diethylaminofluorane, 1 part of benzoyl leuco methylene blue, 2- (2'- as an ultraviolet absorber
4 parts of hydroxy-5'-methylphenyl) benzotriazole were dissolved in 100 parts of diisopropylnaphthalene. The color former oil was emulsified and dispersed to obtain an emulsion having a particle size of 4.5 μm in average particle size. Separately, 6 parts of melamine, 11 parts of 37% by weight formaldehyde aqueous solution, and 30 parts of water are added at 60 ° C.
After heating and stirring for 30 minutes, a transparent mixed aqueous solution of melamine and formaldehyde and a melamine-formaldehyde initial condensation product was obtained. The pH of this mixed aqueous solution is 6.0 to 8.0.
Met. Hereinafter, the mixed aqueous solution of melamine, formaldehyde, and melamine-formaldehyde precondensate will be referred to as an initial condensate solution. The initial condensate solution obtained by the above method is added to and mixed with the above emulsified mixture, and the mixture is stirred and stirred for 3.6.
The pH was adjusted to 6.0 with a wt% hydrochloric acid solution and the liquid volume was adjusted to 6
The temperature was raised to 5 ° C. and stirring was continued for 6 hours. The capsule liquid was cooled to room temperature and adjusted to pH 9.0 with 20% by weight of sodium hydroxide.
Adjusted to. 100 parts of a 10% by weight aqueous solution of polyvinyl alcohol, 10 parts of a carboxy-modified SBR latex in terms of solid content and 50 parts of starch based on this capsule dispersion liquid.
Parts and 10 parts of calcium carbonate were added and water was added to adjust the solid content concentration to 20% to prepare a color developer-containing microcapsule coating solution.

This coating solution was applied to a base paper of 50 g / m ^{2 in} an amount of 5 g /
A microcapsule sheet for pressure-sensitive copying was obtained by coating with an air knife coater so that the solid content of m ² was coated and drying.

[Example 1-2] 2-as an ultraviolet absorber
A microcapsule sheet was obtained in the same manner as in Example 1-1, except that 4 parts of (2′-hydroxy-3′-t-butyl-5′-methylphenyl) -5-chlorobenzotriazole was used.

[Example 1-3] 2-as an ultraviolet absorber
A microcapsule sheet was obtained in the same manner as in Example 1-1, except that 4 parts of (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) -5-chlorobenzotriazole was used.

[Example 1-4] 2-as an ultraviolet absorber
A microcapsule sheet was obtained in the same manner as in Example 1-1, except that 4 parts of hydroxy-4-octoxybenzophenone was used.

[Comparative Example 1] A microcapsule sheet was obtained in the same manner as in Example 1-1, except that no ultraviolet absorber was used.

[Example 2-1] A specific example (2
1) 6 parts, 2-anilino-3-methyl-6-diethylaminofluorane 5 parts, and 2-anilino-6-N-ethyl-N-hexylaminofluorane 3 parts were used, and 2- () was used as an ultraviolet absorber. 2'-hydroxy-5'-methylphenyl) benzotriazole 4 parts and 1-phenyl-1-xylylethane 100 parts as a solvent for dissolving the color former and the ultraviolet absorber were used in the same manner as in Example 1-1. A microcapsule sheet was obtained.

[Example 2-2] 2-as an ultraviolet absorber
Example 2 except that 4 parts of (2'-hydroxy-3 ', 5'-di-t-amylphenyl) benzotriazole were used.
A microcapsule sheet was obtained in the same manner as in -1.

[Example 2-3] 2-as an ultraviolet absorber
A microcapsule sheet was obtained in the same manner as in Example 2-1, except that 4 parts of (2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole was used.

[Comparative Example 2] A microcapsule sheet was obtained in the same manner as in Example 2-1 except that the ultraviolet absorber was not used.

Example 3 A microcapsule sheet was obtained in the same manner as in Example 1-1, except that the specific example (15) was used as the color former.

[Comparative Example 3] A microcapsule sheet was obtained in the same manner as in Example 3 except that the ultraviolet absorber was not used.

[0052]

[Table 1]

As is clear from the results in Table 1, when the microcapsule sheet of the present invention was used, the PCS value after fluorescent lamp irradiation was higher, the coloration of the capsule was less, and the recorded character was smaller than that of the comparative example. OCR reading was possible.

Claims (2)

[Claims] 1. A substantially colorless electronic child in a microcapsule.
The compound contains an electron-donating dye and the electron-accepting compound
A pressure-sensitive recording sheet that produces a color image by reaction with an object
As an electron-donating colorless dye in microcapsules.
Containing a compound represented by the general formula (1) and an ultraviolet absorber.
A pressure-sensitive recording sheet characterized by having the general formula (1):Where R₁ ~ R_FourCan be the same or different, that
Hydrogen atom, C1-C8 alkyl group, and C5-C5, respectively
7 cycloalkyl group, 1 to 4 carbon alkyl group
An optionally substituted aralkyl group having 7 to 20 carbon atoms and
C1-C4 alkyl group, C1-C4 alkoxy
Substituted by a group or a substituted amino group having 1 to 20 carbon atoms
Optionally represents an aryl group having 6 to 26 carbon atoms, R₁ And R
₂ And R₃And R_FourCombine with each other to form a 5-7 membered ring
May be. R_FiveAnd R₆Can be the same or different
Respectively, an alkyl group having 1 to 4 carbon atoms, and 1 to 4 carbon atoms
Alkoxy groups, alkylthio groups having 1 to 4 carbon atoms and
Represents a logen atom. R₇And R ₈Are the same or different
May be a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
Group, an alkoxy group having 1 to 8 carbon atoms, an alkyl group having 1 to 4 carbon atoms
Represents a thio group and a halogen atom. X is a -CH- group
And nitrogen atom. 2. The pressure-sensitive recording sheet according to claim 1, wherein the ultraviolet absorber is a benzotriazole-based compound.