JPH02136287A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance preservability such as light resistance and heat resistance by providing a thermal recording material by supporting two leuco dyes and color developers for developing the leuco dyes into colors by making contact therewith when being heated, on a support by binding the dyes and the developers by a binder. CONSTITUTION:Leuco dyes of formulas I and II (R is an alkyl, each of R1 and R2 is an alkyl or aryl, R3 is H, a lower alkyl, alkoxyl or aralkyloxyl, R4 is H, a lower alkyl, halogen or the like, R5 is H, a halogen or the like, and each of R6 and R7 is a lower alkyl) and color developers for developing the dyes into colors upon making contact therewith when being heated are mixed with a binder to prepare a coating liquid. The coating liquid is applied to a support, followed by drying to provide a recording layer, thereby producing a thermal recording material. The recording material has strong absorptivity throughout the wavelength range from a longer wavelength part of the visible region to a near infrared region.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat-sensitive recording material using a leuco dye as a coloring agent, and more particularly to a heat-sensitive recording material characterized by absorption of near-infrared wavelengths.

[Conventional technology]

Recording materials using leuco dyes have been known for a long time and are used as pressure-sensitive recording paper, heat-sensitive recording paper, etc., and their usage is increasing year by year.

A leuco thermosensitive recording material has a leuco dye and a color developer supported on a support, and produces a colored image when an image signal is thermally applied to it by a minute heating resistor element.

Compared to other recording materials such as electrophotography and electrostatic recording materials, such heat-sensitive recording materials can be recorded in a short time using relatively simple equipment without the need for complicated processes such as development and fixing. It has advantages such as easy maintenance, no noise generation, etc., and is widely used in facsimiles, printers, industrial measurement recorders, computer terminals, etc.
They are not only used for so-called output recording, but because they are compatible with barcodes, they are used in a wide range of applications, including price tags used in food labels, as well as industrial labels used to manage parts and products.

In recent years, devices using semiconductor lasers, which are inexpensive, durable, and easy to maintain, have been used as barcode reading devices. However, the wavelength of semiconductor lasers is 78, unlike that of conventional visible light.
The wavelength is so-called near-infrared wavelength such as 0 nm or 900 nm. Therefore, in order to cope with this, it is necessary for the heat-sensitive recording material to sufficiently absorb near-infrared light in its colored part to create a clear contrast with the reflection from the background part.

In the past, several proposals have been made regarding leuco dyes that have the property of absorbing electromagnetic waves with wavelengths ranging from the long wavelength region of visible light to the near-infrared region.
No. 653 discloses a specific divinyl compound used in the present invention. This compound is pale in color and has color-developing properties, and also has some absorption at 700 nm-1, 000 n+++. In particular, it exhibits strong absorption near 900 nm, creating a clear contrast with the reflection from the background.

[Problem to be solved by the invention]

However, the divinyl compound has a wavelength of 600 nm to 800 nm.
It has a disadvantage that the absorption at m is inferior to the absorption at around 900 nm. That is, when reading with a semiconductor laser at around 900 nm, sufficient reading can be obtained due to clear contrast, but at around 780 nm,
For example, when the thermal energy of a thermal head or the like is insufficient, there is a problem that sufficient contrast cannot be obtained, and reliable reading with clearer contrast is required.

One way to make the absorption in the 600 nm to 800 nm range as strong as possible is to increase the amount of dye added, but this method is very disadvantageous from an economical point of view, and the effect cannot be said to be sufficient. In addition, the above-mentioned publication mentions 3,3-bis(aminophenyl)-6-aminophthalide, 3,3-bis(indolyl)phthalide,
3-aminofluorane, aminobenzofluorane, 2,
6-Diamitsufluorane.

2.6-Diami2-3-methylfluorane, spiropyran, phenoxazine, leukoolamine, carbacylimethane, 3-indolyl-3-(amino)phenylphthalide, 3-indolyl-3-(aminophenyl)azaphthalide, tri Aminofluorene phthalide, tetraaminodivinylphthalide, etc. are shown, but even if these color formers are used in combination, absorption at 600 to 800 ro++ is insufficient.

In addition, in contrast to the vicinity of 900 nm, where absorption is strong, in the vicinity of 780 nm, problems arise in reading the image portion in the storage state after printing. That is, the decrease in the absorption rate of the image area due to light resistance, heat resistance, etc. is large near 780nA+, and at 900nm
It is quite unstable compared to nearby readings.

Therefore, there is a need for an innovative method that can solve these problems, and in particular, as the wavelength of semiconductor lasers continues to become shorter, it is possible to improve reliability by providing clearer contrast in the wavelength range of 600 nm to 800 nm, which will become mainstream in the future. There is a need for reliable reading and storage stability.

The present invention has strong absorption in the entire wavelength range from the long wavelength region of visible light to near-infrared light for reading using a semiconductor laser, and is also stable in terms of storage stability such as light resistance and heat resistance. . The purpose is to provide excellent heat-sensitive recording materials.

[Means to solve the problem]

According to the present invention, in a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye and a color developer that causes the leuco dye to develop color upon contact with heat, the leuco dye has the following general formula (
When using the compound represented by 1), the following general formula (
A heat-sensitive recording material containing at least one of the compounds represented by II) is provided.

(In the formula, R9Rt-1%-R3-R41R5, RGI
Rv, ■, and n represent the following.

R: Alkyl group R1, R,: Substituted or unsubstituted alkyl group, substituted or unsubstituted aryl group R3: Hydrogen atom, lower alkyl group, alkoxy group, or aralkyloxy group R4: Hydrogen atom, lower alkyl group, alkoxy group , halogen or dialkylamino group R6: hydrogen atom, halogen or dialkylamino group RG, R,: lower alkyl group Φ: benzene ring or naphthalene ring n: an integer from ] to 4). 900 as dye
In addition to using a divinyl compound represented by the general formula (1) that has strong absorption near n■, 600 nm to 800 nm
By containing at least one type of compound represented by the general formula (■) having strong absorption in the nm range, the compound has strong absorption in the entire wavelength range from the long wavelength region of visible light to the near infrared region, and It exhibits stable storage stability at all wavelengths and has excellent readability with a semiconductor laser.

In the present invention, the amount of the compound of general formula (U) added to the leuco dye of general formula (1) is usually 5 to 20
It is 0% by weight, preferably 10 to 100% by weight.

If the amount added is less than 5% by weight, the sensitivity improvement effect will be insufficient, and if it exceeds 200% by weight, no improvement in coloring sensitivity can be expected, and this will be economically disadvantageous.

In the present invention, the general formula (I) and the general formula (TI
) is used, but other leuco dyes can be used in combination if necessary. In this case, the leuco dye used in combination is a leuco dye that is generally known for this type of leuco heat-sensitive recording material.
For example, leuco compounds of triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, and fluorene-based dyes are preferably used. Specific examples of such leuco dyes include those shown below.

3.3-bis(p-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3
-N-methyl-N-isobutyl-6-methyl-7-anilinofluorane, 3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluorane.

3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane.

3-diethylamino-6-methyl-7-chlorofluorane.

3-(N-ρ-tri-N-ethylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2-(N-(3'-trifluoran) (methylphenyl)
amino)-6-dinithylaminofluorane, 2-(3
, 6-bis(diethylamino)-9-(o-chloroanilino)xantylbenzoic acid lactam), 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran.

3-diethylamino-7-(o-chloroanilino)fluoran.

2-dibutylamino-7-(0-chloroanilino)fluoran, 3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl -7-(2', 4'-
dimethylanilino)fluoran, 3-(N,N-diethylamino)-5-methyl-7-(
N,N-dibenzylamino)fluorane, benzoylleucomethylene blue 2'-chloro8'-methoxybenzoindolino-pyrylospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrylospirane, 3-(2'- 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy- 5'-nitrophenyl) phthalide, 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl) phthalide, 3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'
-methylphenyl)phthalide.

3-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-(N-benzyl-trifluoro methylanilino)fluorane, 3-pyrrolidino-7-(di-P-chlorophenyl)methylaminofluorane, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluorane.

3-(N-ethyl-p-toluidino)-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-(0-methoxycarbonylphenylamino)fluoran.

3-diethylamino-5-methyl-7-(α-phenylethylamino)fluorane, 3-diethylamino-7-piperidinofluorane, 2-
Chloro-3-(N-methyltoluidino)-7-(p-n
-butylanilino)fluoran, 3- (N-methyl-
N-isopropylamino)-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-(N-benzyl-N-cyclohexylamino)-5
, 6-benzo-7-α-naphthylamino-4'bromofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-N-ethyl-N-(2-ethoxypropyl)amino-6 -Methyl-7-anilinofluorane, 3-N-ethyl-N-tetrahydrofurfurylamino-
6-Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-mesitidino 4',5'-benzofluorane, 3.6-bis(dimethylamino)fluorene-9-spiro-3'- (6'-dimethylamino)phthalide, 3-
Diethylamino-6-dimethylaminofluorene-9-
spiro-3'-(6'-dimethylamino)phthalide,
3.6-bis(diethylamino)fluorene-9-spiro-3'-(6'-dimethylamino)phthalide, 3-
Dibutylamino-6-dimethylaminofluorene-9-
spiro-3'-(6'-dimethylamino)phthalide,
3-diethylamino-6-dimethylaminofluorene-
9-spiro-3'-(6'-diethylamino)phthalide and the like.

In addition, as the color developer used in the present invention, various electron-accepting compounds that cause the leuco dye to undergo catalytic color development are preferably used, such as phenolic compounds, thiophenolic compounds, thiourea derivatives, organic acids, and metal salts thereof. applied,
Specific examples include those shown below.

4.4'-isopropylidene bisphenol, 4.4
′ -isopropylidene bis(O-methylphenol)
, 4.4'-Secondary-butylidene bisphenol, 4.4'-Isopropylidene bis(2-tert-butylphenol), 4.4'-Cyclohexylidene diphenol, 4.4
′ -isopropylidene bis(2-chlorophenol)
, 2.2'-methylenebis(4-methyl-6-tert-butylphenol), 2.2'-methylenebis(4-ethyl-6-tert-butylphenol), 4.4'-butylidenebis(6-tert-butyl- 2-methylphenol), 1.1.3-tris(2-methyl-4-hydroxy-5
-tert-butylphenyl)butane.

1.1.3-Tris(2-methyl-4-hydroxy-
5-cyclohexylphenyl)butane, 4.4'-thiobis(6-tert-butyl-2-
methylphenol), 4,4'-diphenolsulfone.

4-isopropoxy-4'-hydroxydiphenylsulfone.

4-benzyloxy-41-hydroxydiphenyl sulfone, 4.4'-diphenol sulfoxide.

Isopropyl P-hydroxybenzoate, benzyl P-hydroxybenzoate, benzyl protocatechuate, stearyl gallate, lauryl gallate, octyl gallate.

1,7-bis(4-hydroxyphenylthio)-3,5
-dioxahebutane, 1,5-bis(4-hydroxyphenylthio)-3-oxapentane, 1,3-bis(4-hydroxyphenylthio)-propane.

1.3-bis(4-hydroxyphenylthio)-2-hydroxypropane, N,N'-diphenylthiourea, N,N'-di(m-chlorophenyl)thiourea, salicylanilide, 5-chloro-salicylanilide , 2-hydroxy-3-naphthoic acid, 2-hydroxy-1-naphthoic acid, 1-hydroxy-2-naphthoic acid, metal salts of hydroxynaphthoic acid such as zinc, aluminum and calcium.

Bis-(4-hydroxyphenyl)acetic acid methyl ester, bis-(4-hydroxyphenyl)acetic acid benzyl ester, (1), 3-bis(4-hydroxycumyl)benzene, 1.
4-bis(4-hydroxycumyl)benzene.

2.4'-diphenolsulfone, 3.3'-diallyl-4,4'-diphenolsulfone.

3.4-dihydroxy-4'-methyldiphenylsulfone, α,α-bis(4-hydroxyphenyl)-α-methyltoluene.

Antipyrine complex of zinc thiocyanate, tetrabromobisphenol A, tetrabromobisphenol S, etc.

In order to manufacture the heat-sensitive recording material of the present invention, when the above-mentioned leuco dye and color developer are bonded and supported on a support, various commonly used binders can be used as appropriate, and specific examples thereof include, for example, , include the following:

Cellulose derivatives such as polyvinyl alcohol, starch and its derivatives, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose.

Sodium polyacrylate, polyvinylpyrrolidone, acrylamide/acrylic ester copolymer, acrylamide/acrylic ester/methacrylic acid terpolymer, styrene/maleic anhydride copolymer alkali salt, imbutylene/maleic anhydride copolymer In addition to water-soluble polymers such as polymer alkali salts, polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, polyacrylic ester, polymethacrylic ester, vinyl chloride/vinyl acetate copolymer, ethylene/ Emulsions such as vinyl acetate copolymers, latex such as styrene/butadiene copolymers, styrene/butadiene/acrylic copolymers, etc.

In addition, in the present invention, in addition to the leuco dye and developer, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material, such as fillers, are used.

A dispersant, a color image stabilizer, an antioxidant, an antifoaming agent, a light stabilizer, a fluorescent whitening agent, a surfactant, a thermofusible substance (or a lubricant), etc. can also be included.

In this case, fillers include, for example, inorganic fine powders such as calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay talc, surface-treated calcium and silica, and urea. - Examples include organic fine powders such as formalin resin, styrene/methacrylic acid copolymer, and polystyrene resin.

Examples of thermofusible substances include fatty acids such as stearic acid and behenic acid, fatty acid amides such as stearic acid amide and palmitic acid amide, zinc stearate, aluminum stearate, calcium stearate, zinc palmitate, and behenic acid. Fatty acid metal salts such as zinc acid, P-
Benzyl biphenyl, terphenyl, triphenylmethane, benzyl P-benzyloxybenzoate, β-benzyloxynaphthalene, β-naphthoic acid phenyl ester, 1-hydroxy-2-naphthoic acid phenyl ester,
1-Hydroxy-2-naphthoic acid methyl ester, diphenyl carbonate, terephthalic acid dibenzyl ester, terephthalic acid dimethyl ester, 1゜4-dimethoxynaphthalene, 1,4-jethoxynaphthalene, 1,4-
Dibenzyloxynaphthalene, 1,2-bis(phenoxy)ethane, 1,2-bis(3-methylphenoxy)ethane, 1,2-bis(4-methylphenoxy)ethane,
■, 4-bis(phenoxy)butane, 1,4-bis(phenoxy)-2-butene, dibenzoylmethane, 1゜4
-bis(phenylthio)butane, 1,4-bis(phenylthio)-2-butene, 1,3-bis(2-vinyloxyethoxy)benzene, 1,4-bis(2-vinyloxyethoxy)benzene, p- (2-vinyloxyethoxy)biphenyl, p-aryloxybiphenyl, P-
Propargyloxybiphenyl, dibenzoyloxymethane, 1,3-dibenzoyloxypropane, dibenzyl disulfide, 1. l-diphenylethanol, 1.1
-diphenylpropatol, P-(benzyloxy)benzyl alcohol, 1,3-diphenoxy-2-propatol, N-octadecylcarbamoyl-p-methoxycarbonylbenzene, N-octadecylcarbamoylbenzene, and the like.

In the present invention, a conventionally known over layer, under layer, back layer, etc. may be provided for the purpose of preventing head wear, preventing sticking, and stabilizing images. Further, as the support used in the heat-sensitive recording material according to the present invention, paper is mainly used, but various nonwoven fabrics, plastic films, synthetic papers, metal foils, etc., or composite sheets made of a combination of these can also be used as desired. .

The heat-sensitive recording material of the present invention can be used in various fields like conventional ones, but in particular, it can be used in optical character reading devices and bar code readers by taking advantage of its excellent near-infrared light absorption properties. It can be used as a recording material for reading records.

〔Effect of the invention〕

The heat-sensitive recording material of the present invention uses a divinyl compound represented by the general formula (I) as a leuco dye, and contains at least one compound represented by the general formula (II), so that it has a 600 na+- It has strong absorption even at 800 nm, making it excellent for reading at all wavelengths, such as in barcode reading devices that use semiconductor lasers that read in long wavelengths from visible light to near-infrared wavelengths, and is also light and heat resistant. It is also excellent in terms of storage stability, such as stability, and is stable at all wavelengths in the above wavelength range.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. Note that all parts and percentages shown below are based on weight.

Example 1 First, mixtures having the following compositions were dispersed using a sand grinder for 2 to 4 hours to prepare mixed dispersions [Liquid ^], [Liquid B], and [Liquid C].

[Liquid A]

In the above general formula (1), R1 to R6 are 20 parts methyl group 10% aqueous solution of polyvinyl alcohol 20 parts water
60 parts [Liquid B] 10% aqueous solution of polyvinyl alcohol 20 parts water
60 parts [Liquid C] Aluminum hydroxide 7 parts 10% aqueous solution of polyvinyl alcohol 25 parts Water
50
Next, a mixed stirring liquid [Liquid D] having the following composition was prepared as a heat-sensitive layer coating liquid.

[Liquid D]

[^Liquid] 4 parts [B
Liquid] 1 part [Liquid C] 67 parts water
8 parts of the above [Liquid D], the paint adhesion amount after drying is 7.5 g.
The heat-sensitive recording material of the present invention was prepared by coating the mixture on high-quality paper and drying it, followed by calendering to obtain a smoothness of 700 to 1200 seconds.

Example 2 In the B solution of Example 1, 3-(4-diethylamino-
3-(4-diethylamino-2-benzyloxy)-3- instead of 2-methoxyphenyl)-3-(1(4-dimethylaminophenyl)-1(4-chlorophenyl)-1,3-butadienyl)benzophthalide A heat-sensitive recording material of the present invention was prepared in the same manner as in Example 1, except that (1(4-diethylaminophenyl)-1-phenyl-1,3-butadienyl)benzophthalide was used.

Example 3 In [Liquid B] of Example 1, 3-(4-diethylamino-2-methoxyphenyl)-3-(1(4-dimethylaminophenyl)-1(4-chlorophenyl)-1,3
-butadienyl)benzophthalide instead of 3-(4-
diethylamino-2-methoxyphenyl)-3-(1(
4-dimethylaminophenyl)-1-phenyl-1,3
A heat-sensitive recording material of the present invention was prepared in the same manner as in Example 1, except that (-butadienyl)benzophthalide was used.

Example 4 In the [Liquid D] composition of Example 1, [Liquid A] and [Liquid B]
A heat-sensitive recording material of the present invention was prepared in the same manner as in Example 1, except that the amounts of each were changed to 3 parts.

Comparative Example A heat-sensitive recording material for relative softness was prepared in the same manner as in Example 1, except that [Liquid B] was not used in [Liquid D] of Example 1.

The heat-sensitive recording material obtained as described above was tested for absorption, heat resistance, and light resistance in the image area. The results are shown in FIG. 1 and Table 1.

Sample preparation method Using a thermal printing experiment device manufactured by Matsushita Electronic Components@ with a thin film head, head power 0.681/dot, line recording time 10m5ec/1ine, scanning line density 8 x 3.
Under the condition of 85 dots/am, the pulse width is 0.9 m5ec.
Print with .

(1) Image area absorption The above printed sample was measured in the wavelength range of 600n+ml to 0OOn+m using a Hitachi 300 spectrophotometer.
The reflectance of the image area was measured.

(2) Heat Resistance After the printed sample was stored at 70° C. under dry conditions for 24 hours, the reflectance of the image area was measured at 78° C. and 900 nm using a Hitachi Model 300 spectrophotometer.

(3) Light resistance The above-mentioned printed sample was left under a 5,0 OOLux fluorescent lamp for 100 hours, and then measured in the same manner as in (2) above.

Table 1 It can be seen that it is an excellent product with several advantages.

Note that the heat-sensitive recording materials obtained in Examples 2 and 3 also had colored image reflection spectra similar to those of Example 1.

[Brief explanation of the drawing]

FIG. 1 shows the reflectance for each wavelength of colored images of the heat-sensitive recording material of the present invention and the heat-sensitive recording material for comparison. Curve 1 (solid line): Colored image reflection spectrum of the heat-sensitive recording material obtained in Example 1 Curve 2 (dotted line): Colored image reflection spectrum of the heat-sensitive recording material obtained in Comparative Example Figure 1 and Table 1 As is clear from the figure, the heat-sensitive recording material of Example 1 of the present invention was compared with that of the comparative example. It has strong absorption from 600nm to 800n+++, and has stable storage stability such as heat resistance and light resistance.
This creates a clear contrast with the reflection from the skin in a wide wavelength range from the long wavelength range of visible light to near-infrared light. Patent applicant: Toshiaki Ikeura, patent attorney at Rico Co., Ltd. (and one other person)

Claims (1)

[Claims] (1) In a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye and a color developer that causes the leuco dye to develop color upon contact with heat, a compound represented by the following general formula (I) is used as the leuco dye, and , a heat-sensitive recording material containing at least one compound represented by the following general formula (II). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (In the formula, R, R_1, R_2, R_3, R_4, R_5
, R_6, R_7, ▲There are mathematical formulas, chemical formulas, tables, etc.▼
, n represent the following. R: alkyl group R_1, R_2: substituted or unsubstituted alkyl group, substituted or unsubstituted aryl group R_3: hydrogen atom, lower alkyl group, alkoxy group or aralkyloxy group R_4: hydrogen atom, lower alkyl group, alkoxy group, Halogen or dialkylamino group R_5: Hydrogen atom, halogen or dialkylamino group R_6, R_7: Lower alkyl group ▲ Numerical formula, chemical formula, table, etc. ▼: Benzene ring or naphthalene ring n: Integer from 1 to 4)