JPH021378A - Thermal recording material - Google Patents

Abstract

PURPOSE:To improve color forming sensitivity and developed color density by providing a thermal recording layer comprising a specified leuco dye, a color developer for developing the dye into a color upon making contact therewith and a specified sensitizer on a support to produce a thermal recording material. CONSTITUTION:At least one leuco dye of formula I (each of R1, R2 is H, a lower alkyl or benzyl, R3 is H or a lower alkyl, and R4 is H, Cl, F, a lower alkyl or the like) or formula II (R5 is a lower alkyl, and X is a halogen), at least one sensitizer of formula III (R6 is H or Cl, R7 is methyl or the like, and R8 is H, butyl or the like) and a color developer are dispersed in an aqueous medium to prepare a coating liquid. The coating liquid is applied to a support, and is dried to provide a thermal recording layer, thereby obtaining a thermal recording material.

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 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, unlike conventional visible light, the wavelength of semiconductor lasers is 780 nm.
The wavelength is so-called near-infrared wavelength such as 900 nm or 900 nm. Therefore, in order to cope with this, the heat-sensitive recording material should sufficiently absorb near-infrared light in its coloring part.
It is necessary to create a clear contrast with the reflection from the background.

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 infrared region.
No. 64 discloses a specific fluoran leuco dye used in the present invention.

The publication lists the following compounds as sensitizers to be used.

Higher fatty acid amides, benzamide, stearamide, acetoacetanilide, thioacetanilide, dimethyl phthalate, dibenzyl terephthalate, dibenzyl isophthalate, bis(tert-butylphenol), such as 4,4'-dimethoxydiphenylsulfone, 4-iso Diethers of bisphenol S such as propoxy-4'-butoxysulfone, 4,4'-dibutoxydiphenylsulfone, 4,4'-di-n(or iso)-pentyloxydiphenylsulfone, diphenylamine, carbazole, 2. 3-di-m-tolylbutane, 4,
4'-dimethylbiphenyl, di-β-naphthylphenylenediamine, etc.

[Problem to be solved by the invention]

However, even if sensitizers including the above-mentioned sensitizers have good effects on other fluoran-based leuco dyes, none show satisfactory effects on the fluoran-based leuco dyes used in the present invention. I can't find it. In other words, the known sensitizers for fluorane-based leuco dyes are not as effective for increasing the sensitivity and density of the image coloring area as they are for other fluorane-based leuco dyes. Even if the sensitivity and density increase to some extent are not noticeable, they have the opposite effect on heat resistance, resulting in severe background fogging and discoloration of the image area, and are not suitable for use.

In the future, it is expected that control using reading devices using semiconductor lasers will become even more common in industry, and there will be a strong demand for the development of industrial labels that can be stably used in high-temperature environments.

Therefore, the present invention has high color development sensitivity and color density for reading using a semiconductor laser, and can withstand use in a high temperature environment. The purpose is to provide a heat-sensitive recording material with excellent 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 has the following general formula (
A heat-sensitive recording material characterized in that it uses at least one of the compounds represented by 1) and (II) and at least one of the compounds represented by the following general formula (III) as a sensitizer. provided.

(In the formula, R1 and R2 each independently represent a hydrogen atom, a lower alkyl group, or a benzyl group, R1 represents a hydrogen atom or a lower alkyl group, and R4 represents a hydrogen atom, a chlorine atom, a fluorine atom, a lower alkyl group, a lower (In the formula, R9 represents a lower alkyl group and X represents a halogen atom.) (In the formula, RG represents a hydrogen atom or a chlorine atom, R7 represents a methyl group, (R8 represents a hydrogen atom, a butyl group, or a tertiary-amylphenyl group. At least one fluoran compound represented by the general formula (Il) is used as a sensitizer, and
By using at least one of the compounds shown in l), the barcode can be read by a barcode reader using a semiconductor laser, and has high coloring sensitivity and color density, as well as excellent heat resistance. Become.

Specific examples of the compound represented by the general formula (TIr) used as a sensitizer in the present invention include the following, but are not limited thereto.

(1) 2-(2'-hydroxy-5'-methylphenyl)-benzotriazole0■ [13 (2) 2-(2'-hydroxy-3'-tertiary-
Butyl-5'-methylphenyl)-5-chlorobenzotriazole l-1゜(3) 2-(2'-hydroxy-5'-tert-
octylphenyl)-benzotriazole (4) Even with 2-(2'-hydroxy-3',5'-ditertiary-amylphenyl)-benzotriazole, no improvement in coloring sensitivity can be expected and it is economically disadvantageous.

In addition, in the present invention, at least one compound represented by the general formulas (1) and (II) is used as the leuco dye, and among fluoran compounds, this compound is particularly suitable for the long wavelength range of visible light. It has the ability to absorb electromagnetic waves in the infrared range.

Specific examples of the leuco dye represented by the general formula (I) or (If) include those shown in Table 1, but are not limited thereto.

Table 1 All of these compounds can be easily obtained by known methods.

In the present invention, the above-mentioned sensitizer is for leuco dye,
It is usually added in an amount of 10 to 300% by weight, preferably 80 to 200% by weight. If the amount added is less than 10 weight percent, the sensitivity improvement effect will be insufficient; on the other hand, if it exceeds 300 weight percent,
In the present invention, as the leuco dye, the general formula (1
) and (II), and preferably a compound represented by the following general formula (IV) is used in combination. By using the compound in combination,
Absorption in the long wavelength region of 800 nm or more becomes strong.

(In the formula, R0 is an alkyl group with 8 or less carbon atoms, R2 is an alkyl group with 8 or less carbon atoms, a cycloalkyl group with 5 to 7 carbon atoms, a chlorine atom, a bromine atom, an alkyl group with 4 or less carbon atoms as a substituent) >Jt also represents a benzyl group or phenyl group. Oll, 2 or 3, x1 comrades of (Xl)m and x2 comrades of (x2)n may be the same or different.x3 is chlorine 1jX
or bromine atom. ) Specific examples of the compound represented by the general formula (IV) are as follows.

(101) 3.3-bis(2-(p-dimethylaminophenyl)-2-(phenylethynyl)-4,5,6
,7-te1-rachlorophthalide (102) 3.3-bis[2-(P-dimethylaminophenyl)-2-(p-methylphenyl)ethynyl3
-4.5,6.7-te1~rachlorophthalide (103) 3.3-bis(2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethynyl)~4.5,6.7 -Titrachlorophthalide (104) 3.3-bisC2-Cp-dimethylaminophenyl)2~(p-ethoxyphenyl)ethynyl)
-4,5,6,7-te1helachlorophthalide (105) 3.3-bis[2-(P-dimethylaminophenyl)-2-(m+p-dimethylphenyl)ethynyl]-4.5,6 .7-Titrachlorophthalide (106) 3.3-bis(2-(p-dimethylaminophenyl)-2-(o-methyl-P-methoxyphenyl)ethynyl]-4゜5.6.7-Titra Chlorophthalide (107) 3.3-bis(2-(p-dimethylamino-0-methylphenyl)-2-phenylethynyl)-
4,5,6,7-titrachlorophthalide (108) 3.3-bis(2-(p-dimethylamino-0-chlorophenyl)-2-(p-methylphenyl)ethynyl)-4,5゜6 .7-Titrachlorophthalide (1,09) 3.3-bis(2-(p-dimethylaminophenyl)-2-(p-chlorophenyl)ethynyl)-4,5,6,7-titrachlorophthalide (+10) 3.3-bis(2-(p-dimethylaminophenyl)-2-(o,p-dimethoxyphenyl)ethynyl)-4,5,6,7tetrachlorophthalide (111) 3.3- Bis(2-(p-methylbutylaminophenyl)-2-(p-methoxyphenyl)ethynyl)-4,5,6°7-titrachlorophthalide (112) 3.3-bisf:2-(p -dimethylaminophenyl)2-(p-octylphenyl)ethynyl]-4.5,6.7-te1herachlorophthalide(+13) 3.3-bis(2-(p-dimethylaminophenyl)2-(p -hexyloxyphenyl)ethynyl)-4,5,6゜7-titrachlorophthalide (114) 3.3-bis(2-(p-methylcyclohexylaminophenyl)-2-(p-methylphenyl) ethynyl]-/1,5,6.7-titrachlorophthalide (115) 3.3-bis[2-(ρ-ethylbenzylaminophenyl)-2~(p-methoxyphenyl)
ethynyl]-4,5゜6.7-titrachlorophthalide (116) 3.3-bisC2-(p-dimethylaminophenyl)-2-phenylethynyl)-4,5,6,
7-te1-dibromophthalide (117) 3.3-bis(z-(p-dimethylaminophenyl)-2-phenylethynyl]-5-chloro-
4,6,7-1~ribromophthalide (II8) 3.3-bisC2-Cp-dimethylaminophenyl)-2-(p-methoxyphenyl)ethynyl]-5,6-dichloro-4,7-dibromophthalide Further, as the color developer used in the present invention, various electron-accepting substances that react with the leuco dye and develop color when heated are used, and specific examples thereof include phenol as shown below. Examples include acidic substances, organic or inorganic acidic substances, or their esters and salts.

gallic acid, salicylic acid, 3-isopropylsalicylic acid,
3-cyclohexylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4'-impropylidene diphenol, 4,4'-isopropylidene bis(2-chloro phenol), 4,4'-isopropylidene bis(2,6-dibromophenol), 4,4'-inpropylidene bis(
2,6-dichlorophenol), 4,4'-isopropylidene bis(2-methylphenol), 4,4'-isopropylidene bis(2,6-dimethylphenol), 4
, 4'-isopropylidene bis(2-tert-butylphenol), 4,4'-secondary-butylidene diphenol, 4,4'-cyclohexylidene bisphenol, 4,4'-cyclohexylidene bis(2-methylphenol) ), 4-tert-butylphenol, 4
-phenylphenol, 4,4'-methylenebis(oxyethylenethio)diphenol, 4,4'-thiobis(
6-tert-butyl-3-methylphenol), 2,
2'-methylenebis(4-methyl-6-tert-butylphenol), 4-hyperoxydiphenoxide,
α-Naphl--, β-naphthol, 3,5-xylenol, thymol, methyl-4-hydroquinone-1, 4-hydroxyacet-phenone, novolak-type phenolic resin, 2,2'-thiobis( 4,6-dichlorophenol), catechol, resorcinol, hydroquinone, pyrogallol, phloroglycine, fluoroclidine carbon 1, 4-tert-octylcatechol, 2,
2'-methylenebis(4-chlorophenol), 2,2
'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-dihydroxydiphenyl,
Butyl p-hydroxybenzoate, ρ-propyl benzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-hydroxybenzot'f
Z-p-chlorobenzyl, p-hydroxybenzoic acid-0
-Chlorbenzyl, p-methylbenzyl p-hydroxybenzoate, n-octyl p-hyroxybenzoate, benzoic acid, zinc salicylate, 1-hydroxy-2-
Naphthoic acid, 2-hydroxy-6-naphthoic acid, zinc 2-hydroxy-6-naphthoate, 4-hydroxydiphenylsulfone, 4-hydroxy-4'-chlorodiphenylsulfone, bis(3-allyl-4-hydroxyphenyl) Sulfone, bis(4-hydroxyphenyl) sulfide, 2-hydroxyloxyP-1-ruylic acid, 3,5-
Zinc di-tert-butylsalicylate, 3,5-di-
Tin tertiary-butylsalicylate, tartaric acid, oxalic acid,
Maleic acid, citric acid, succinic acid, stearic acid, 4-
Hydroxyphthalic acid, 4-hydroxybenzoic acid chlorobenzyl ester, etc.

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

These include:

Polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolone, acrylamide/acrylic acid ester copolymer, Acrylic aluminum 1-/
Water-soluble polymers such as acrylic acid ester/methacrylic acid terpolymer, styrene/maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein, etc. In addition, emulsions such as polyvinyl acetate, polyurethane, polyacrylic ester, polymethacrylic ester, vinyl chloride/vinyl acetate copolymer, ethylene/vinyl acetate copolymer, styrene/butadiene copolymer, styrene/butadiene/acrylic Latex such as copolymers, etc.

In addition, in the present invention, in addition to the leuco dye, color developer, and sensitizer, if necessary, auxiliary additive components that are commonly used in this type of heat-sensitive recording material, such as fillers, dispersants, and color image stabilization agents, may be added. It is also possible to contain agents, antioxidants, antifoaming agents, light stabilizers, fluorescent brighteners, and the like. In this case, examples of the filler include calcium carbonate, silica, oxidized
In addition to fl buttons, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, surface-treated inorganic fine powders such as calcium and silica, urea-formalin resin, styrene/methacrylic acid copolymer, Examples include organic fine powder such as polystyrene resin.

In the present invention, conventionally known over Jt'), under layer, back Jt layer, etc. may be provided for the purpose of preventing head wear, preventing sticking, and stabilizing images. Although paper is mainly used as the support for the heat-sensitive recording material according to the present invention, various nonwoven fabrics, plastic films, synthetic papers, gold M foil, etc., or composite sheets made of combinations of these may optionally be used. can.

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 at least one of the fluoran compounds represented by the above-mentioned -formation) and (n) as a leuco dye, and the compound represented by the above-mentioned -formation (rJ■) as a sensitizer. By using at least one type of barcode, it is possible to read it with a barcode reader using a semiconductor laser, and it also has excellent thermal response and heat resistance.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. In addition, all parts and percentages shown below are "weight", fノ, (
It is standard.

Example 1 First, a mixture consisting of the following composition was ground in a sand grinder.
A mixed dispersion liquid [Liquid A] was prepared by dispersing for ~4 hours.

[Liquid A]

Bis(3-allyl-4-hydroxyphenyl)sulfone 24 parts Aluminum hydroxide 18 parts 10% aqueous solution of polyvinyl alcohol 42 parts Water
126 parts Next, a stirred liquid CB liquid having the following composition was prepared as a heat-sensitive layer coating liquid.

[Liquid B]

[Liquid A 3 105 parts 2
-(2'-Hydroxy-5'-methylphenyl)-16.3% aqueous solution of benzo-1-lyazole 37 parts table-
20% aqueous solution of a compound of Na 21 in 1 15 parts water
The amount of paint attached after drying is 6 g/n of the 40 parts Hokuki heat-sensitive Jf coating liquid? The heat-sensitive recording material of the present invention was prepared by coating it on high-quality paper and drying it.

Example 2 In [Liquid 13] of Example 1, 2-(2'-hydroxy-3'-tert-butyl 5 '-methylphenyl)-5-chlorobenzo 1
A heat-sensitive recording material of the present invention was prepared in the same manner as in Example 1, except that lyazole was used.

Ratio I bite example 1 In the [Il solution] of Example 1, except that 2,4-di(vinyloxyethylhexy)benzene was used instead of 2-(2'-hydroxy5'-methylphenyl)-benzotriazole. A comparative heat-sensitive recording material was prepared in the same manner as in Example 1.

Comparative Example 2 [Liquid B] of Example 1 except that N-octadecylcarbamoyl-p-methyl-oxycarbonylbenzene was used instead of 2-(2'-hydroxy-57-methylphenyl)-benzotriazole. A comparative heat-sensitive recording material was prepared in the same manner as in Example 1.

Ratio 1 Bite Example 3 Example 1 except that methyl glycol dibenzoate was used instead of 2-(2'-hydroxy-5'-methylphenyl)-benzo I lyazole in [Liquid B] of Example 1. A heat-sensitive recording material for comparison was prepared in the same manner as described above.

The heat-sensitive recording material obtained as described above was tested for color development sensitivity and heat resistance.

The results are shown in Table-2. Note that the 411 constant value is the reflectance determined by Mlll at a wavelength of 780 nm using a Hitachi 330 model spectrophotometer. Moreover, the test method was as follows.

(1) Color development sensitivity A thermal printing experimental device manufactured by Matsushita Electronics Components and equipped with a thin film head, head power 0.45 W/dot, line recording time 10 m5ec/1ine, scanning line density 8 x 3.
．． Under the condition of 85 dots l”/mm, the pulse 111 was set to 0,
Printing was performed at 9 m5ec, and the reflectance of the background and printed area was measured.

(2) Heat resistance Samples printed under the conditions of (1) were tested at 70°C and 80°C.
After being left in a constant humidity chamber at °C for 24 hours, the reflectance of the background and printed area was measured in the same manner.

Table 2 Example 3 In Example 1, Nα in Table 1 was used as the leuco dye.
21 compound and 3,3-bis(2-(p-dimethylaminophenyl)-2-(phenylethynyl)-4,5,6
, 7-titrachlorophthalide (compound of specific example Nα101) was used in the same manner as in Example 1 to prepare a heat-sensitive recording material, which had good absorption characteristics in a wide range from 630 nm to 950 r+m. was gotten.

From the above results, it can be seen that the heat-sensitive recording material of the present invention has excellent thermal responsiveness and excellent heat resistance.

Patent Applicant Rico Co., Ltd. 1st Attorney Patent Attorney Toshiaki Ikeura (and 1 other person) Procedural Amendments June 2, 1989 Commissioner of the Japan Patent Office Yoshi 1) Moon Yi 1, Indication of Case 1999 Patent Application No. 23248 2. Name of the invention Thermal recording material 3. Relationship with the case of the person making the amendment Patent applicant address 1-3-6 Nakamagome, Ota-ku, Tokyo Name
(674) Rico Co., Ltd. - Representative Hama 1)
Hiro 4, Agent Address: 151 Address: 1-58-10, Yoyogi, Shibuya-ku, Tokyo Date: Amended Specification 1, Name of Invention Thermal Recording Material 2, Claims (1) Leuco dye and heating the leuco dye In a heat-sensitive recording material that utilizes a color-forming reaction between a color developer and a color developer that develops color upon contact, the leuco dyes include the following general formulas (I) and (
Using at least one of the compounds shown in ■),
A heat-sensitive recording material characterized in that at least one compound represented by the following general formula (III) is used as a sensitizer.

(In the formula, R1 and 2 each independently represent a hydrogen atom, a lower alkyl group, or a benzyl group, R1 represents a hydrogen atom or a lower alkyl group, and R4 represents a hydrogen atom, a chlorine atom, a fluorine atom, a lower alkyl group, (In the formula, R6 represents a lower alkyl group and X represents a halogen atom.) (In the formula, R6 represents a hydrogen atom or a chlorine atom, and R7 represents a methyl group. , represents a tertiary-octyl group or a tertiary-amylphenyl group, and R8 represents a hydrogen atom, a butyl group, or a tertiary-amylphenyl group.) 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to color formers. The present invention relates to a heat-sensitive recording material using a leuco dye, 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 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 needle-side 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, unlike conventional visible light, the wavelength of semiconductor lasers is 780 nm.
nm, 900r+n+, etc. 6 Therefore, in order to cope with this, the heat-sensitive recording material should sufficiently absorb the near-infrared light in its coloring area, thereby reducing the reflection from the background part. It is necessary to create a clear contrast.

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 infrared region.
No. 64 discloses a specific fluoran leuco dye used in the present invention.

The publication lists the following compounds as sensitizers to be used.

Higher fatty acid amide, benzamide, stearic acid amide, acetoacetanilide, thioacetanilide, dimethyl phthalate, dibenzyl terephthalate, dibenzyl isophthalate, bis(tert-butylphenol) 1 e.g. 4,4'-dimethoxydiphenylsulfone, 4-iso Diethers of bisphenol S such as propoxy-4'-butoxysulfone, 4,4'-dibutoxydiphenylsulfone, 4,4'-di-n(or iso)-pentyloxydiphenylsulfone, diphenylamine, carbazole, 2. 3-di-m-tolylbutane, 4,
4'-dimethylbiphenyl, di-β-naphthylphenylenediamine, etc.

[Problem to be solved by the invention]

However, even if sensitizers including the above-mentioned sensitizers have good effects on other fluoran-based leuco dyes, none show satisfactory effects on the fluoran-based leuco dyes used in the present invention. I can't find it. In other words, the known sensitizers for fluorane-based leuco dyes are not as effective for increasing the sensitivity and density of the image coloring area as they are for other fluorane-based leuco dyes. Even if the sensitivity and density increase to some extent are not noticeable, they have the opposite effect on heat resistance, resulting in severe background fogging and discoloration of the image area, and are not suitable for use.

In the future, it is expected that control using reading devices using semiconductor lasers will become even more common in industry, and there will be a strong demand for the development of industrial labels that can be stably used in high-temperature environments.

Therefore, an object of the present invention is to provide a heat-sensitive recording material that has high color development sensitivity and color density, can withstand use in high-temperature environments, and has excellent heat resistance for reading using a semiconductor laser.

[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 (
1) and (TI), and at least one compound represented by the following general formula (III) as a sensitizer. provided.

(In the formula, Ro and R2 each independently represent a hydrogen atom, a lower alkyl group, or a benzyl group, R3 represents a hydrogen atom or a lower alkyl group, and R4 represents a hydrogen atom, a chlorine atom, a fluorine atom, a lower alkyl group, a lower (In the formula, R5 represents a lower alkyl group, and X represents a halogen atom.) (In the formula, RG represents a hydrogen atom or a chlorine atom, R7 represents a methyl group, tertiary-octyl group or tertiary-amylphenyl group, and R represents a hydrogen atom, a butyl group, or a tertiary-amylphenyl group.) That is, the heat-sensitive recording material of the present invention is a leuco dye containing the general formula (1) and At least one fluoran compound represented by the general formula (II) is used as a sensitizer, and
By using at least one of the compounds shown in I), it is possible to read a bar code with a bar code reader using a semiconductor laser, and it has high color sensitivity and color density as well as excellent heat resistance. Become.

Specific examples of the compound represented by the general formula (III) used as a sensitizer in the present invention include the following, but are not limited thereto.

(1) 2-(2'-hydroxy-5'-methylphenyl)-benzotriazole 113 (2) 2-(2'-hydroxy-3'-tert-
Butyl-5'-methylphenyl)-5-chlorobenzotriazole (3) 2-(2'-hydroxy-5'-tertiary-
octylphenyl)-benzotriazole (4) 2-(2'-hydroxy-3',5'-ditertiary-amylphenyl)-benzotriazole All of these compounds can be easily obtained by known methods.

In the present invention, the above-mentioned sensitizer is for leuco dye,
It is usually added in an amount of 10 to 300% by weight, preferably 80 to 200% by weight. If the amount added is less than 10% by weight, the sensitivity improvement effect will be insufficient, and if it exceeds 300% by weight, no improvement in coloring sensitivity can be expected, and this will be economically disadvantageous.

In addition, in the present invention, at least one compound represented by the general formulas (1) and (If) is used as the leuco dye, and among fluoran compounds, this compound is particularly suitable for the long wavelength range of visible light. It has the ability to absorb electromagnetic waves in the infrared range.

Specific examples of the leuco dye represented by the general formula (I) or (I[) include those shown in Table 1, but are not limited thereto.

Table 1 In the present invention, at least one of the compounds represented by the above general formulas (1) and (II) is used as the leuco dye, and a compound represented by the following general formula (IV) is also used in combination. It is preferable to do so. By using these compounds in combination, absorption in the long wavelength region of 800 nm or more becomes stronger.

(In the formula, R is an alkyl group having 8 or less carbon atoms, R2 is an alkyl group having 8 or less carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, and a chlorine atom, a bromine atom, an alkyl group having 4 or less carbon atoms as a substituent. Indicates a benzyl group or a phenyl group that may have a group. ×1, indicates 0.1.2 or 3, x1 comrade of (Xl)m, x2 comrade of (x2).
They may be the same or different. x3 represents a chlorine atom or a bromine atom. ) Specific examples of the compound represented by the general formula (rV) are as follows.

(101) 3.3-bis(2-(p-dimethylaminophenyl)-2-(phenylethynyl)-4,5,6
,7-titrachlorophthalide (102) 3.3-bis(2-(p-dimethylaminophenyl)-2-(p-methylphenyl)ethynyl)
-4,5,6,7-titrachlorophthalide (103) 3.3-bis(2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethynyl)-4,5,6,7 -Titrachlorophthalide (104) 3.3-bis(2-(p-dimethylaminophenyl)-2-(p-ethoxyphenyl)ethynyl)-4,5,6,7-titrachlorophthalide (105) 3.3-bis(2-(p-dimethylaminophenyl)-2-(m,ρ-dimethylphenyl)ethynyl)-4,5,6,7-titrachlorophthalide (106) 3.3-bis( 2-(p-dimethylaminophenyl)2-(o-methyl-2-methoxyphenyl)ethynyl]-4゜5.6.7-titrachlorophthalide (107) 3.3-bis(2-(p- dimethylamino-0-methylphenyl)-2-phenylethynyl)-
4,5,6,7-titrachlorophthalide (108) 3.3-bis(2-(p-dimethylamino-0-chlorophenyl)-2-(p-methylphenyl)ethynyl)-4,5゜6 .7-tel-lachlorophthalide (109) 3.3-bis(2-(p-dimethylaminophenyl)=2-(ρ-chlorophenyl)ethynyl)
-4,5,6,7-titrachlorophthalide (110) 3.3-bis[2-(p-dimethylaminophenyl)2-(o+p-dimethoxyphenyl)ethynyl]-4.5,6.7- 1-Lachlorophthalide (11,1) 3,3-bis[2-(ρ-methylbutylaminophenyl)-2-(p-methoxyphenyl)ethynyl)-4,5,6゜7-titrachlorophthalide ( 112) 3.3-bis[:2-(p-dimethylaminophenyl)2-(p-octylphenyl)ethynyl)-4,5,6,7-tetrachlorophthalide (113) 3.3-bis(2 -(p-dimethylaminophenyl)-2-(p-hexyloxyphenyl)ethynyl)-4,5,6゜7-titrachlorophthalide (114) 3.3-bis(2-(p-methylcyclo) xylaminophenyl)-2-(p-methylphenyl)ethynyl]-4,5,6,7-titrachlorophthalide (115) 3.3-bis(2-(p-ethylbenzylaminophenyl)-2- (p-methoxyphenyl)ethynyl)-4,5゜6.7-titrachlorophthalide (116) 3.3-bis(2-(p-dimethylaminophenyl)-2-phenylethynyl)-4,5, 6,
7-titrabromophthalide (117) 3.3-bis[2-(p-dimethylaminophenyl)-2-phenylethynyl]-5-chloro-
4,6,7-Tribromophthalide (118) 3.3-bis[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethynyl]-5,6-dichloro-4,7- Dibromophthalide Furthermore, in the present invention, other leuco dyes can also be used in combination to adjust the color tone and the like.

As the leuco dye used in combination in this case, leuco dyes that are generally known in this type of leuco-based heat-sensitive recording material are used, such as triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, Leuco compounds of dyes such as fluorenes 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-p-tolyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane.

2- (N-(3'-trifluoromethylphenyl)
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-(0-chloroanilino) ) Fluoran, 3-dibutylamino-7-(o-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-pyrylospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrylospirane, 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-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-trifluoromethylanilino)fluoran, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluoran, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluoran, 3-(N-ethyl-P-toluidino)-7-Cα-phenylethylamino)fluoran, 3-diethylamino-7-(o-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-penzo7-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(diethylamine)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, etc.

Further, as the color developer used in the present invention, various electron-accepting substances that react with the leuco dye and develop color when heated are used, and specific examples thereof include phenol as shown below. Examples include acidic substances, organic or inorganic acidic substances, or their esters and salts.

gallic acid, salicylic acid, 3-isopropylsalicylic acid,
3-cyclohexylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4'-isopropylidene diphenol, 4,4'-isopropylidene bis(2-chloro phenol), 4,4'-isopropylidene bis(2,6-dibromophenol), 4,4'-isopropylidene bis(
2,6-dichlorophenol).

4.4'-isopropylidene bis(2-methylphenol), 4,4'-isopropylidene bis(2,6-dimethylphenol), 4,4'-isopropylidene bis(
2-tert-butylphenol), 4,4'-secondary-butylidene diphenol, 4,4'-cyclohexylidene bisphenol, 4,4'-cyclohexylidene bis(2-methylphenol), 4-tert-
Butylphenol, 4-phenylphenol, 4,4
'-Methylenebis(oxyethylenethio)diphenol, 4,4'-thiobis(6-tert-butyl-3-
methylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 3,5-xylenol, thymol, methyl-4-hydroxybenzoate , 4-hydroxyacetophenone, novolac type phenolic resin, 2,2'-thiobis(4,6-dichlorophenol), catechol, resorcinol, hydroquinone, pyrogallol, phloroglycin,
Phloroglizine carboxylic acid, 4-tert-octylcatechol, 2,2'-methylenebis(4-chlorophenol), 2,2'-methylenebis(4-methyl-6-
tertiary-butylphenol), 2,2'-dihydroxydiphenyl, ethyl p-hydroxybenzoate, P-
Propyl hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-chlorobenzyl p-hydroxybenzoate, 0-chlorobenzyl p-hydroxybenzoate, p-methyl p-hydroxybenzoate Benzyl, p-hydroxybenzoic acid-n
-Octyl, benzoic acid, zinc salicylate, ■-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic acid, zinc 2-hydroxy-6-naphthoate, 4-hydroxydiphenylsulfone, 4-hydroxy-4'-chloro Diphenylsulfone, bis(3-allyl-4-hydroxyphenyl)sulfone, bis(4-hydroxyphenyl)sulfide, 2-hydroxy-p-toluic acid, 3.
Zinc 5-di-tert-butylsalicylate, 3,5-
tin di-tert-butylsalicylate, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid,
4-hydroxyphthalic acid, 4-hydroxybenzoic acid chlorobenzyl ester, etc.

In order to manufacture the heat-sensitive recording material of the present invention, when the above-mentioned leuco dye, color developer, and sensitizer are bonded and supported on a support, various commonly used binders can be used as appropriate, and specific examples thereof can be used. Examples 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 the present invention, in addition to the leuco dye, color developer, and sensitizer, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material, such as fillers, dispersants, and color image stabilization agents, may be added. It is also possible to contain agents, antioxidants, antifoaming agents, light stabilizers, fluorescent brighteners, and the like. In this case, fillers include, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, and surface-treated inorganic fine powders such as calcium and silica. , urea-formalin resin, styrene/methacrylic acid copolymer, polystyrene resin, and other organic fine powders.

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. 6
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 at least one fluoran compound represented by the general formulas (1) and (II) as a leuco dye, and a fluoran compound represented by the general formula (III) as a sensitizer.
) By using at least one type of compound shown in ), it is possible to read with a bar code reader using a semiconductor laser, and has excellent thermal response and heat resistance.

〔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, a mixture consisting of the following composition was ground in a sand grinder.
A mixed dispersion liquid [Liquid A] was prepared by dispersing for ~4 hours.

Liquid cA] A 10% aqueous solution of aluminum hydroxide polyvinyl alcohol in water and a mixed stirring liquid [Liquid B] having the following composition were prepared as a layer coating liquid.

[Liquid B]

[Liquid A] 18 parts 42 parts 126 parts thermosensitive 105 parts 16.3% aqueous solution of 2-(2'-hydroxy-5'-methylphenyl)-benzotriazole 37 parts 20% of the compound Nα21 in Table 1 Aqueous solution 15 parts water
40 parts of the above heat-sensitive layer coating liquid, the coating amount after drying is 6g/
The heat-sensitive recording material of the present invention was prepared by coating it on high-quality paper and drying it to ensure durability.

Example 2 In [Liquid B] of Example 1, 2-(2'-hydroxy-3'-tert-butyl-5' was used instead of 2-(2'-hydroxy-5'-methylphenyl)-benzotriazole. A heat-sensitive recording material of the present invention was prepared in the same manner as in Example 1 except that -methylphenyl)-5-chlorobenzotriazole was used.

Comparative Example 1 In [Liquid B] of Example 1, 2,4-di(vinyloxyethoxy)benzene was used instead of 2-(2'-hydroxy-5'-methylphenyl)-benzotriazole. A comparative heat-sensitive recording material was prepared in the same manner as in Example 1.

Comparative Example 2 The same procedure was carried out except that in [Liquid B] of Example 1, N-octadecylcarbamoyl-p-methoxycarbonylbenzene was used instead of 2-(2'-hydroxy-5'-methylphenyl)-benzotriazole. A comparative heat-sensitive recording material was prepared in the same manner as in Example 1.

Comparative Example 3 In [Liquid B] of Example 1, methyl glycol dibenzoate was used instead of 2-(2'-hydroxy-5'-methylphenyl)-benzotriazole.
A comparative heat-sensitive recording material was prepared in the same manner as in Example 1.

The heat-sensitive recording material obtained as described above was tested for color development sensitivity and heat resistance.

The results are shown in Table-2. In addition, the measured value is Hitachi 33
The reflectance at a wavelength of 780 nm was measured using a 0-type spectrophotometer. Moreover, the test method was as follows.

(1) Color development sensitivity A thermal printing experimental device made of electronic components and equipped with a thin film head was used, with head power of 0.45 W/dot, 1 line recording time of 10 m5ec/1ine, and scanning line density of 8 x 3.
Under the conditions of 85 dots/mm, the pulse width was 0, 9m5e
c, and the reflectance of the background and printed area was measured.

(2) Heat resistance Samples printed under the conditions of (1) were tested at 70°C and 80°C.
After leaving it for 24 hours in a constant temperature bath at .degree. C., the reflectance of the background and printed portion was measured in the same manner.

Table 2 Example 3 In Example 1, Nα in Table 1 was used as the leuco dye.
21 compound and 3,3-bis[2-(p-dimethylaminophenyl)-2-(phenylethynyl)-4,5,6
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that ,7-titrachlorophthalide (compound of specific example Nα101) was used in combination, and it showed good absorption characteristics in a wide range from 630 parts m to 950 nm. I got what I had.

From the above results, it can be seen that the heat-sensitive recording material of the present invention has excellent thermal responsiveness and excellent heat resistance.

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, the leuco dye is represented by the following general formulas (I) and (II). A heat-sensitive recording material characterized in that at least one compound is used and at least one compound represented by the following general formula (III) is used as a sensitizer. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (In the formula, R_1 and R_2 each independently represent a hydrogen atom, a lower alkyl group, or a benzyl group, R_3 represents a hydrogen atom or a lower alkyl group, and R_4 represents a hydrogen atom or a lower alkyl group. atom, chlorine atom, fluorine atom, lower alkyl group, lower alkoxyl group, or trifluoromethyl group.) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (In the formula, R_5 represents a lower alkyl group, and represents a halogen atom.) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(III) (In the formula, R_6 represents a hydrogen atom or a chlorine atom, and R_
7 represents a methyl group, a tertiary octyl group or a tertiary amyl phenyl group, and R_8 represents a hydrogen atom, a butyl group or a tertiary amyl phenyl group. )