JPH0298489A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a stable material having a strong absorption over the range from a longer wavelength region of visible rays to a near infrared region, for reading by use of a semiconductor laser, by using a specified compound as a leuco dye, and incorporating at least one of other two specified compound. CONSTITUTION:A thermal recording material comprises a divinyl compound of formula I which has a strong absorption in the vicinity of 900nm as a leuco dye, and at least one of the compounds of formula II and III which have a strong absorption in the wavelength range of 600-800nm. The recording material thus has a strong absorption throughout the wavelength range from a longer wavelength region of visible rays to a near infrared region, shows stable preservability at any wavelength, and has excellent properties for reading by use of a semiconductor laser. The at least one compound of formula II or III is added in an amount of ordinarily 5-200wt.%, preferably 10-100wt.% based on the amount of the leuco dye of formula I. If the addition amount is less than 5wt.%, a sensitivity-enhancing effect will be insufficient, whereas an addition amount in excess of 200wt.% does not promise a corresponding enhancement of color forming sensitivity and is inadvantageous on an economical basis.

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.
It is used as pressure-sensitive recording paper, heat-sensitive recording paper, etc., and its use 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 electrophotographic and electrostatic recording materials, such heat-sensitive recording materials can be recorded in a short time using relatively simple equipment without complex processing 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.
It is not only used for so-called output recording, but because it is compatible with bar codes, it is used in a wide range of applications, including price tags used in food labels, single parts, and industrial labels used for product management.

In recent years, devices using semiconductor lasers, which are inexpensive, durable, and easy to maintain, have been used as barcode reading devices. However, unlike conventional visible light, the wavelength of semiconductor lasers is 780 nm.
The wavelength is so-called near-infrared wavelength, such as 900 nm and 900 na+. 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 in the range of 700 nm to 1°000 nm. Particularly in the vicinity of 900, strong absorption is exhibited, creating a clear contrast with the reflection from the background.

[Problems to be Solved by the Invention] However, the divinyl compound has a
It has a disadvantage that its absorption at 900 nm is inferior to that 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 is not sufficient, sufficient contrast cannot be obtained. There is a need for reliable reading with clearer contrast.

One possible 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-cyamitsufluorane, 2,6-diamitsufluorane, 2,6-diamitsufluorane, spiropyran, phenoxazine, leukoolamine, carbacylimethane, 3-indolyl-3-
(amino)phenylphthari 1ζ, 3-indolyl-3-
(aminophenyl) azaphthalide, triaminofluorene phthalide, tetraaminodivinyl phthalide, etc. are shown, but even if these coloring agents are used in combination, the
The absorption at n■ 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, due to light resistance, heat resistance, etc., the absorption rate of the image area decreases greatly near 780 nm, making reading much more unstable than reading near 900 nm.

Therefore, there is a need for an efficient method to solve these problems, and in particular, as the wavelength of semiconductor lasers continues to get shorter, clearer contrast can be achieved at the wavelengths of 600 nm to 800 nm, which will become mainstream in the future. Reliable reading and storage stability are required.

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

[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 is represented by the following formula (1):
There is provided a heat-sensitive recording material characterized in that it uses the compound represented by the formula (11) and at least one of the compounds represented by the following formulas (11) and (III).

That is, the heat-sensitive recording material of the present invention contains 900% as a leuco dye.
Using a divinyl compound represented by the above formula (1) that has strong absorption in the vicinity of 600 nm to 800 nm.
By containing at least one of the compounds represented by formulas (II) and (III) that have strong absorption in the In addition, it exhibits stable storage stability at all wavelengths and has excellent readability with a semiconductor laser.

In the present invention, the amount of the compounds of formulas (II) and (m) added to the leuco dye of formula (1) is usually 5 to 5.
200% by weight, preferably 10-100% 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 formulas (1), (■) and (III
) 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) Watari 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-p-tolyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane , 2-(N-(3'-trifluoromethylphenyl)amino)-6-ethylaminofluorane, 2-(
3,6-bis(diethylamino)-9-(o-chloroanilino)xantylbenzoic acid lactam), 3-diethylamino-6-methyl-7-chloromethylanilino)fluoran, 3-diethylamino-7-(o-chloroanilino) Fluoran, 3-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)fluoran, benzoylleucomethylene blue 6'-chloro-8'-methoxy-benzoindolino-virillospirane.

6'-Bromo-3'-methoxy-benzoindolino-virirosvirane, 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)phthalide, 3- (2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-nitrophenyl)phthalide, 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2 '-methoxy-51-methylphenyl)phthalide, 3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-51
-methylphenyl)phthalide, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-( N-benzyl-trifluoromethylanilino)fluoran, 3-pyrrolidino-7-(di-ρ-chlorophenyl)methylaminofluorane, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluoran, 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-penzo 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, the color developer used in the present invention includes various electron-accepting metal compounds that cause the leuco dye to undergo catalytic color development, such as phenolic compounds, thiophenolic compounds, thiourea derivatives, organic acids, and metal salts thereof. preferably applied,
Specific examples include those shown below.

4.4'-isopropylidene bisphenol, 4.4
′ -isopropylidene bis(0-methylphenol)
, 4.4'-Secondary-butylidene bisphenol.

4.4'-isopropylidene bis(2-tertiary-
butylphenol), 4.4'-cyclohexylidene diphenol.

4.4'-isopropylidenebis(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 3-tris(2-methyl-4-hydroxy -5-tert-butylphenyl)butane,! , 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-4'-hydroxydiphenylsulfone, 4.4'-diphenolsulfoxide, P-hydroxybenzoic acid Isopropyl, 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(-monophenyl)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, calcium, etc., 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 produce the heat-sensitive recording material of the present invention, when the leuco dye and color developer are bonded and supported on a support, various commonly used binders can be used as appropriate. , include the following:

Polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide/acrylic acid ester copolymer, acrylamide/acrylic acid ester/methacrylic In addition to water-soluble polymers such as acid ternary copolymers, styrene/maleic anhydride copolymer alkali salts, isobutylene/maleic anhydride copolymer alkali salts, polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate , polyurethane, polyacrylic acid ester, polymethacrylic acid ester, vinyl chloride/vinyl acetate copolymer, ethylene/vinyl acetate copolymer, etc. emulsion, styrene/butadiene copolymer, styrene/butadiene/acrylic copolymer, etc. latex etc.

In addition, in the present invention, in addition to the leuco dye and color developer, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material, such as fillers, dispersants, color image stabilizers, antioxidants, etc. agents, antifoaming agents, light stabilizers, fluorescent brighteners,
A surfactant, a thermofusible substance (or 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 balmitate, and behenic acid. Fatty acid metal salts such as brewed zinc, p-
Benzyl biphenyl, terphenyl, triphenylmethane, benzyl p-benzyloxybenzoate, β-benzyloxynaphthalene, β-naphthoic acid phenyl ester, l-hydroxy-2-naphthoic phenyl ester, l-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, 1,4-bis(phenoxy)butane, 1,4-bis(phenoxy)-2-butene, dibenzoylmethane, l
.

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, 1.1-diphenylethanol, 1.
1-diphenylpropatol, p-(benzyloxy)
Examples include benzyl alcohol, 1,3-diphenoxy-2-propatol, N-octadecylcarbamoyl-P-methoxycarbonylbenzene, and N-octadecylcarbamoylbenzene.

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 the formula (1) as a leuco dye.
) is used, and the divinyl compound represented by the formula (
By containing at least one of the compounds shown in II) and (1), it has strong absorption even in the range of 600 nm to 800 nm, and can be read at long wavelengths ranging from the long wavelength region of visible light to the near infrared region. It is excellent in reading at all wavelengths with barcode reading devices using semiconductor lasers, and is stable at all wavelengths in the above wavelength range in terms of storage stability such as light resistance and heat resistance. be.

〔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 electric switches.

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

[Liquid A] Compound of formula (1) 20 parts 10% aqueous solution of polyvinyl alcohol 20 parts water
60
Part [Liquid B] Compound of formula (n) 20 parts 10% aqueous solution of polyvinyl alcohol 20 parts Water
6
0 parts [Liquid C] 2.2-bis(4-hydroxyphenyl)propane
12 parts aluminum hydroxide 7 parts 10% aqueous solution of polyvinyl alcohol 25 parts water
50 parts Next, a mixed stirring liquid [Liquid D] having the following composition was prepared as a heat-sensitive layer coating liquid.

[Liquid D]

(Liquid A) 4 parts [
B liquid] 1 part [C
Liquid] 67 parts water
8 parts of the above [Liquid D], the paint adhesion amount after drying is 5g.
The heat-sensitive recording material of the present invention was prepared by coating and drying the mixture on high-quality paper so that the temperature was 700 to 1,200 seconds.

Example 2 The heat-sensitive recording material of the present invention was produced in the same manner as in Example 1, except that the compound of formula (II) was used instead of the compound of formula (II) in [Liquid B] of Example 1. Created.

Example 3 In the [Liquid D] composition of Example 1, [Liquid] 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 2 parts.

Comparative Example A comparative heat-sensitive recording material 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 Electronics Co., Ltd. and equipped with a thin film head, the head power was 0.68 seconds/dot, the recording time per line was 10 m5ec/1ine, and the scanning line density was 8 x 3.
Under the conditions of 85 dots/school sandals, pulse width is 0.9+1se
Print with c.

(1) Image Area Absorption The reflectance of the image area of the printed sample was measured in the wavelength range of 600n+m-1,000nm using a Hitachi Model 300 spectrophotometer.

(2) Heat resistance After the printed sample was left at 70° C. under dry conditions for 24 hours, the reflectance of the image area was measured at 780 ns+ and 900 nm using a Hitachi Model 300 spectrophotometer.

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

As is clear from Table 1, Figure 1, and Table 1, the heat-sensitive recording material of the present invention has a 6001m-800n
It has strong absorption in the wavelength range of about 100 m, and has stable storage properties such as heat resistance and light resistance. It can be seen that the image has excellent contrast.

[Brief explanation of drawings]

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 (actual IIA'): Color image reflection spectrum curve 2 (-dotted chain line) of the heat-sensitive recording material obtained in Example 1: Color image reflection spectrum curve 3 (actual IIA') of the heat-sensitive recording material obtained in Example 2. Dot-dashed line): Colored image reflection spectrum curve 4 of the heat-sensitive recording material obtained in Example 3 (dotted line): Colored image reflection spectrum of the heat-sensitive recording material obtained in Comparative Example Patent applicant Rico Co., Ltd.

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 formula (I) is used as the leuco dye, and A heat-sensitive recording material comprising at least one compound represented by the following formulas (II) and (III). ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (I) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (III)