JP2777593B2 - Thermal recording material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat-sensitive recording material using a leuco dye as a color former, and more particularly to a heat-sensitive recording material characterized by absorption of wavelengths in the near infrared region.

[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, and the like, and the amount of use thereof is increasing year by year.

The leuco-based heat-sensitive recording material is obtained by supporting a leuco dye and a color developer on a support, and gives a color-developed image when an image signal is given thermally by a micro heating resistor element.

Such a heat-sensitive recording material is used for other recording materials, for example,
Compared to electrophotographic or electrostatic recording materials, recording can be obtained in a short time with relatively simple equipment without complicated processing such as development and fixing, maintenance is easy, and noise is generated. Facsimile, printer, industrial measurement recorder, computer terminal, etc., not only used for so-called output recording, but also used for food labels etc. with barcode correspondence In addition to price tags, it is widely used for industrial labels used for parts and product management.

In recent years, a bar code reader using a semiconductor laser which is inexpensive, has excellent durability and is easy to maintain has been used. However, the wavelength of the semiconductor laser is different from that of visible light,
The wavelength is a so-called near-infrared portion such as m or 900 nm. Therefore, in order to cope with this, it is necessary that the thermosensitive recording material sufficiently absorbs the near-infrared portion in the color-developed portion, thereby producing a clear contrast with the reflection by the background portion.

Heretofore, several proposals have been made regarding leuco dyes having a property of absorbing electromagnetic waves having wavelengths ranging from a long wavelength part to an infrared part of visible light, and for example, Japanese Patent Application Laid-Open No. 62-106964 discloses a method for use in the present invention. Certain fluoran leuco dyes are disclosed. The publication thus discloses the following compounds as sensitizers to be used.

Higher fatty acid amides, benzamides, stearic acid amides, acetoacetic anilides, thioacetanilides, dimethyl phthalate, dibenzyl terephthalate, dibenzyl isophthalate, bis (tert-butylphenol) s,
For example, 4,4'-dimethoxydiphenylsulfone, 4-isopropoxy-4'-butoxysulfone, 4,4'-dibutoxydiphenylsulfone, 4,4'-di-n (or iso) -pentyloxydiphenylsulfone, etc. Bisphenol S diethers such as diphenylamine,
Carbazole, 2,3-di-m-tolylbutane, 4,4′-dimethylbiphenyl, di-β-naphthylphenylenediamine and the like.

[Problems to be solved by the invention]

However, even if the above sensitizers and sensitizers exhibiting good effects on other fluoran leuco dyes are used, those which show a satisfactory effect on the fluoran leuco dye used in the present invention are not provided. I can't find it. That is, the known sensitizer for the fluoran leuco dye, for the leuco dye used in the present invention, the effect of increasing the sensitivity of the image coloration portion, the higher the density, the more fluoran leuco dye appears in other fluoran leuco dye Even those which are not remarkable and show some degree of increase in sensitivity and density, have an adverse effect on heat resistance, cause background fogging and fading of the image area, and there is nothing suitable for use.

In the future, it is expected that the management of readers using semiconductor lasers will be further extended in industrial aspects, and there is a strong demand for the development of industrial labels and the like that can be used stably under high-temperature environments.

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

[Means for solving the problem]

According to the present invention, in a heat-sensitive recording material utilizing a color-forming reaction between a leuco dye and a developer that causes the leuco dye to develop a color when heated, the following general formulas (I) and (II) are used as the leuco dye. And at least one compound represented by the following general formula (III) is used as a sensitizer.

(Wherein, 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, R ₄ represents a hydrogen atom, a chlorine atom, a fluorine atom,
Represents a lower alkyl group, a lower alkoxyl group or a trifluoromethyl group. ) (In the formula, R ₅ represents a lower alkyl group, and X represents a halogen atom.) (Wherein, R ₆ represents a hydrogen atom or a chlorine atom, R ₇ represents a methyl group, a tertiary-octyl group or a tertiary-amylphenyl group, and R ₈ represents a hydrogen atom, a butyl group or a tertiary-amylphenyl group. That is, the heat-sensitive recording material of the present invention uses at least one of the fluoran compounds represented by the general formulas (I) and (II) as the leuco dye and uses the general formula (II) as a sensitizer.
By using at least one of the compounds represented by I), it is possible to read with a bar code reader or the like using a semiconductor laser, and to have high color sensitivity and color density and 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 (2) 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole (3) 2- (2'-hydroxy-5'-tert-octylphenyl) -benzotriazole (4) 2- (2'-hydroxy-3 ', 5'-ditert-amylphenyl) -benzotriazole All of these compounds can be easily obtained by a known method.

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

In the present invention, at least one of the compounds represented by the above general formulas (I) and (II) is used as the leuco dye. It has the ability to absorb electromagnetic waves over the infrared. The general formula (I) or (I
Specific examples of the leuco dye represented by I) include those shown in Table 1, but are not limited thereto.

In the present invention, at least one of the compounds represented by the general formulas (I) and (II) is used as the leuco dye, and a compound represented by the following general formula (IV) may be used in combination. preferable. By using the compound in combination, the absorption in the long wavelength region of 800 nm or more is enhanced.

Wherein R ₁ is an alkyl group having 8 or less carbon atoms, and R ₂ is an alkyl group having 8 carbon atoms.
The following alkyl groups, cycloalkyl groups having 5 to 7 carbon atoms,
A benzyl group or a phenyl group which may have a chlorine atom, a bromine atom, or an alkyl group having 4 or less carbon atoms as a substituent. X ¹ and X ^{2 each} represent an alkyl group having 8 or less carbon atoms, an alkoxy group having 8 or less carbon atoms, a fluorine atom, a chlorine atom or a bromine atom, m and n each represent 0, 1, 2 or 3; ¹ ) m
X ¹ comrades, (X ²⁾ n X ² comrades may also say be the same. X ³ represents a chlorine atom or a bromine atom. Specific examples of the compound represented by the general formula (IV) include the following.

(101) 3,3-bis [2- (p-dimethylaminophenyl) -2- (phenylethenyl) -4,5,6,7-tetrachlorophthalide (102) 3,3-bis [2- (P-dimethylaminophenyl) -2- (p-methylphenyl) ethenyl] -4,5,6,
7-tetrachlorophthalide (103) 3,3-bis [2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,
6,7-tetrachlorophthalide (104) 3,3-bis [2- (p-dimethylaminophenyl) -2- (p-ethoxyphenyl) ethenyl] -4,5,
6,7-tetrachlorophthalide (105) 3,3-bis [2- (p-dimethylaminophenyl) -2- (m, p-dimethylphenyl) ethenyl] -4,
5,6,7-tetrachlorophthalide (106) 3,3-bis [2- (p-dimethylaminophenyl) -2- (o-methyl-p-methoxyphenyl) ethenyl] -4,5,6, 7-tetrachlorophthalide (107) 3,3-bis [2- (p-dimethylamino-o-
Methylphenyl) -2-phenylethenyl] -4,5,6,7
-Tetrachlorophthalide (108) 3,3-bis [2- (p-dimethylamino-o-
(Chlorophenyl) -2- (p-methylphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide (109) 3,3-bis [2- (p-dimethylaminophenyl) -2- (p- Chlorophenyl) ethenyl] -4,5,6,
7-tetrachlorophthalide (110) 3,3-bis [2- (p-dimethylaminophenyl) -2- (o, p-dimethoxyphenyl) ethenyl]-
4,5,6,7-tetrachlorophthalide (111) 3,3-bis [2- (p-methylbutylaminophenyl) -2- (p-methoxyphenyl) ethenyl]-
4,5,6,7-tetrachlorophthalide (112) 3,3-bis [2- (p-dimethylaminophenyl) -2- (p-octylphenyl) ethenyl] -4,5,
6,7-tetrachlorophthalide (113) 3,3-bis [2- (p-dimethylaminophenyl) -2- (p-hexyloxyphenyl) ethenyl]
-4,5,6,7-tetrachlorophthalide (114) 3,3-bis [2- (p-methylcyclohexylaminophenyl) -2- (p-methylphenyl) ethenyl] -4,5,6, 7-tetrachlorophthalide (115) 3,3-bis [2- (p-ethylbenzylaminophenyl) -2- (p-methoxyphenyl) ethenyl]
-4,5,6,7-tetrachlorophthalide (116) 3,3-bis [2- (p-dimethylaminophenyl) -2-phenylethenyl] -4,5,6,7-tetrabromophthalide (117) 3,3-bis [2- (p-dimethylaminophenyl) -2-phenylethenyl] -5-chloro-4,6,7-
Tribromophthalide (118) 3,3-bis [2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -5,6
-Dichloro-4,7-dibromophthalide As the developer used in the present invention, various electron-accepting substances that react with the leuco dye at the time of heating to develop the color are applied, and specific examples thereof are given below. The following are phenolic substances, organic or inorganic acidic substances, esters and salts thereof, and the like.

Gallic acid, salicylic acid, 3-isopropylsalicylic acid, 3-cyclohexylsalicylic acid, 3,5-ditert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4′-isopropylidene diphenol,
4,4'-isopropylidenebis (2-chlorophenol), 4,4'-isapropylidenebis (2,6-dibromophenol), 4,4'-isopropylidenebis (2,6-dichlorophenol) , 4,4'-isopropylidenebis (2
-Methylphenol), 4,4'-isopropylidenebis (2,6-dimethylphenol), 4,4'-isopropylidenebis (2-tert-butylphenol), 4,4 '
-Secondary butylidene diphenol, 4,4'-cyclohexylidenebisphenol, 4,4'-cyclohexylidenebis (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, novolak phenolic resin, 2,2'-thiobis (4,6-dichlorophenol), catechol, resorcin, hydroquinone, pyrogallol, phloroglysin , Phloroglysin carboxylic acid, 4-tert-octylcatechol, 2,
2'-methylenebis (4-chlorophenol), 2,2'-
Methylenebis (4-methyl-6-tert-butylphenol), 2,2'-dihydroxydiphenyl, p-
Ethyl hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-chlorobenzyl p-hydroxybenzoate, o-chlorobenzyl p-hydroxybenzoate, p- Hydroxybenzoic acid-p-methylbenzyl, p-hydroxybenzoic acid-n-octyl, benzoic acid, zinc salicylate, 1-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic acid, 2-hydroxy-6-naphthoic acid Zinc acid, 4-hydroxydiphenylsulfone, 4-hydroxy-4'-chlorodiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) sulfide, 2
-Hydroxy-p-toluic acid, zinc 3,5-di-tert-butylsalicylate, tin 3,5-di-tert-butylsalicylate, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid, 4 -Hydroxyphthalic acid, chlorobenzyl 4-hydroxybenzoate and the like.

When the above-mentioned leuco dye, color developer and sensitizer are bound and supported on a support for producing the heat-sensitive recording material of the present invention, various conventional binders can be appropriately used, and specific examples thereof are given below. Examples thereof include the following.

Polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylate copolymer, acrylamide / acrylate /
Water-soluble polymers such as methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein, and polyacetic acid Vinyl, polyurethane, polyacrylate,
Emulsions such as polymethacrylic acid esters, vinyl chloride / vinyl acetate copolymers, ethylene / vinyl acetate copolymers, and latexes such as styrene / butadiene copolymers and styrene / butadiene / acrylic copolymers.

Further, in the present invention, together with the above-mentioned leuco dye, color developer and sensitizer, if necessary, auxiliary additives commonly used in this type of heat-sensitive recording material, for example, fillers, dispersants, and color image stabilization. Agents, antioxidants, defoamers, light stabilizers, optical brighteners and the like. In this case, as the filler, for example, other than inorganic fine powder such as calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, surface-treated calcium and silica, etc. Organic fine powder such as urea-formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin.

In the present invention, conventionally known over layers, under layers, back layers, and the like can be provided for the purpose of preventing head wear, preventing sticking, and stabilizing images. Further, as the support used in the thermosensitive recording material according to the present invention, paper is mainly used, but various nonwoven fabrics,
Plastic films, synthetic papers, metal foils and the like, or composite sheets combining these can be used arbitrarily.

The heat-sensitive recording material of the present invention can be used in various fields as well as conventional ones. In particular, the heat-sensitive recording material is used for optical character readers and bar code readers by utilizing its excellent near-infrared light absorption characteristics. Can be used as a recording material for reading a record.

〔The invention's effect〕

The heat-sensitive recording material of the present invention uses at least one of the fluoran compounds represented by the general formulas (I) and (II) as a leuco dye, and uses the general formula (III) as a sensitizer.
By using at least one of the compounds represented by
It enables reading with a bar code reader or the like using a semiconductor laser, and has excellent thermal response and heat resistance.

〔Example〕

Next, the present invention will be described in more detail with reference to examples. In addition, all the parts and% shown below are based on weight.

Example 1 First, a mixture having the following composition was dispersed with a sand grinder for 2 to 4 hours to prepare a mixed dispersion [Solution A].

[A liquid]

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 mixed stirring liquid [Solution B] having the following composition was prepared as a heat-sensitive layer coating liquid. did.

[B liquid]

[Solution A] 105 parts 16.3% aqueous solution of 2- (2'-hydroxy-5'-methylphenyl) -benzotriazole 37 parts 20% aqueous solution of compound No. 21 in Table 1 15 parts Water 40 parts The following heat sensitivity The layer coating solution was applied on wood free paper such that the coating weight after drying was 6 g / m ² , and dried to prepare the heat-sensitive recording material of the present invention.

Example 2 In Example 1, [solution B], 2- (2'-hydroxy-3'-tert-butyl-5 'was used instead of 2- (2'-hydroxy-5'-methylphenyl) -benzotriazole. -Methylphenyl) -5-chlorobenzotriazole was used in the same manner as in Example 1 to prepare a heat-sensitive recording material of the present invention.

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

Comparative Example 2 Example 2 was repeated except that [N-octadecylcarbamoyl-p-methoxycarbonylbenzene] was used in place of 2- (2'-hydroxy-5'-methylphenyl) -benzotriazole in [Solution B] of Example 1. In the same manner as in Example 1, a comparative thermosensitive recording material was prepared.

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

The heat-sensitive recording material thus obtained was tested for color sensitivity and heat resistance. Table 2 shows the results. The measured values are obtained by measuring the reflectance at a wavelength of 780 nm using a Hitachi 330 type spectrophotometer. The test method was as follows.

(1) Color sensitivity Using a thermal printing tester with a thin film head, manufactured by Matsushita Electronic Components Co., Ltd., under conditions of head power 0.45 w / dot, one line recording time 10 msec / line, and scanning line density 8 × 3.85 dots / mm. Then, printing was performed with a pulse width of 0.9 msec, and the reflectance of the background and the printed portion was measured.

(2) Heat resistance Samples printed under the conditions of (1) were subjected to 70 ° C and 80 ° C.
After standing for 24 hours in the constant temperature bath, the reflectance of the background and the printed portion was measured in the same manner.

Example 3 In Example 1, as a leuco dye, N in Table 1 was used.
o.21 and 3,3-bis [2- (p-dimethylaminophenyl) -2- (phenylethenyl) -4,5,6,7-tetrachlorophthalide (compound of Specific Example No. 101) A heat-sensitive recording material was prepared in the same manner as in Example 1 except that the above was used in combination, and a material having good absorption characteristics in a wide range of 630 nm to 950 nm was obtained.

From the above results, it can be seen that the heat-sensitive recording material of the present invention is excellent in heat response and heat resistance.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tetsuya Amano 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (56) References JP-A-63-37158 (JP, A) JP-A Sho 62-106964 (JP, A) JP-A-62-176880 (JP, A) JP-A-57-193388 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/30

Claims (1)

(57) [Claims] 1. A heat-sensitive recording material utilizing a color-forming reaction between a leuco dye and a developer which causes the leuco dye to form a color when heated and brought into contact, wherein the leuco dye is represented by the following general formula (I):
A heat-sensitive recording material comprising at least one compound represented by formula (II) and at least one compound represented by the following general formula (III) as a sensitizer. (Wherein, 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, R ₄ represents a hydrogen atom, a chlorine atom, a fluorine atom,
Represents a lower alkyl group, a lower alkoxyl group or a trifluoromethyl group. ) (In the formula, R ₅ represents a lower alkyl group, and X represents a halogen atom.) (Wherein, R ₆ represents a hydrogen atom or a chlorine atom, R ₇ represents a methyl group, a tertiary-octyl group or a tertiary-amylphenyl group, and R ₈ represents a hydrogen atom, a butyl group or a tertiary-amylphenyl group. .)