JPS5811195A - Thermo-sensitive recording material - Google Patents

Abstract

PURPOSE:To obtain the thermo-sensitive recording material, thermal response property thereof is excellent, the fog of foundation thereof is little and color formation property thereof is superior, by making the grain size of leuco dyestuffs as the color-forming component of a thermo-sensitive color-forming layer and an acidic substance as a developing component uniform within the range of 1-2mu. CONSTITUTION:The aimed thermo-sensitive recording material is acquired by forming the thermo-sensitive color-forming layer while using materials of which the grain size of the leuco dyestuffs and the acidic substance color-forming the leuco dyestuffs when heating is within the range of 1-2mu as principal ingredients. The grain size of the leuco dyestuffs and the acidic substance is adjusted as follows; that is, these components are each mixed with a proper disperser such as water together with a dispersion assistant agent as necessary, and pulverized up to 0.3-40mu or smaller by means of a pulverizing and dispersing machine, such as a ball mill, an attriter, etc., each disperser obtained is filtered by means of a proper filter medium such as a membrane filter, and the materials, grain size thereof is within the range of 1-2mu, are recovered. The dispersers are adjusted, applied onto a substrate and dried, and the aimed recording material is acquired.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, more specifically, a heat-sensitive coloring layer containing as a main component a usually colorless or light-colored leuco dye and an acidic substance capable of coloring the leuco dye when heated. The present invention relates to an improvement in a heat-sensitive recording material having the structure formed above.

Recently, various recording materials have been researched and developed and put into practical use in the information recording field in response to social demands such as diversification and increase in information, resource conservation, and pollution-free technology.Among them, thermal recording materials are (1) A colored image is recorded simply by heating, eliminating the need for a complicated development process; (2) It is relatively simple and can be produced using compact equipment; and the resulting recording material is easy to handle. (3) paper is often used as a support;
In this case, not only the cost of the support is low, but also the feel of the obtained recording material is similar to that of plain paper.
It is widely used in the fields of computer output, printers such as calculators, recorders for medical measurement, low and high speed facsimiles, automatic ticket vending machines, thermal copying, etc.

The above-mentioned heat-sensitive recording material is produced by coating a paper-like support such as ordinary paper, synthetic paper, or synthetic resin film with a heat-sensitive coloring layer forming liquid containing a coloring component that can cause a coloring reaction when heated, and drying it. A colored image is recorded on the heat-sensitive recording material thus obtained by heating it with a thermal pen or a thermal head.

Typical heat-sensitive recording materials include, for example,
3-4160 or Japanese Patent Publication No. 45-14039. However, such conventional heat-sensitive recording materials have low thermal responsiveness, and when applied to high-speed recording, recording A colored image with excellent density and clarity could not be obtained.

Several attempts to improve the above-mentioned drawbacks of conventional thermal recording paper have been proposed, for example, Japanese Patent Publication No. 51-2
No. 7599, Japanese Unexamined Patent Publication No. 48-19231, and the like disclose that the thermal responsiveness can be improved by adding a thermofusible substance. However, even with these techniques, sufficiently satisfactory results have not yet been obtained. In recent years, with the development of society, the demand for high-speed recording has increased, and there is a strong desire to develop heat-sensitive recording materials that can be compatible with high-speed recording devices. However, in general, increasing the sensitivity of a heat-sensitive recording material and improving its thermal responsiveness causes background coloring called fog, while attempts to reduce background coloring result in poor thermal responsiveness, and there is no way to solve this problem. This was a major point in developing a heat-sensitive recording material that could adequately handle high-speed recording.

The present inventors have conducted intensive research to solve the problems in the conventional technology as described above, and have recently decided to improve the particle size of the leuco dye, which is the coloring component of the thermosensitive coloring layer, and the acidic substance, which is the color developing component. The present inventors have discovered that by adjusting the thickness within the range of 1 to 2 .mu.m, it is possible to obtain a heat-sensitive recording material with good thermal response, less background fogging, and good color development, and have thus completed the present invention. That is, the present invention provides a heat-sensitive recording material having a structure in which a heat-sensitive coloring layer containing a leuco dye and an acidic substance that causes the leuco dye to develop color when heated is formed on a support, in which particles are used as the leuco dye and the acidic substance. Diameter is 1~2μ
The object of the present invention is to provide a heat-sensitive recording material characterized by using a material in the range of .

The particle size of the leuco dye and acidic substance is preferably adjusted as follows. That is, each of these components is mixed with a suitable dispersion medium such as water together with a dispersion aid as necessary, and a grinding/dispersing machine such as a ball mill or an attritor is used to reduce the
The particles are ground to a particle size of 40 μm or less, and each of the resulting dispersions is separated daily using a suitable filtration material such as a membrane filter, and those having a particle size in the range of 1 to 2 μm are collected.

The leuco dye-containing dispersion and acidic substance-containing dispersion having a particle size in the range of 1 to 2μ obtained as above are as follows:
A heat-sensitive coloring layer forming liquid is prepared by mixing with each dispersion liquid containing a binder, filler, sensitizer, antifoaming agent, penetrating agent, etc., which are separately prepared as necessary. This is coated onto a support by a conventional coating method, and after drying, a heat-sensitive recording material is obtained. The dispersion liquid may be prepared in the form of a mixture of the above-mentioned heat-sensitive color forming layer forming components as long as the object of the present invention is not impaired.

Next, specific examples of leuco dyes, acidic substances, and other components to be applied in the present invention will be given.

(4) Leuco Dye As the leuco dye, leuco bodies of various colorless or light-colored dyes shown below are usually used.

(a) Leuco compound of triphenylmethane dye represented by the following general formula: group, monoalkyl group, and allyl group.) Specific examples of the above-mentioned leuco compounds are as follows.

3.3-bis(p-dimethylaminophenyl)-phthalide, 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone) 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone) (dimethylaminophenyl)-6-dibutylaminophenyl 3.3-bis(p-dimethylaminophenyl)-6-chlorophthalide 3.3-bis(p-dibutylaminophenyl)phthalide (b) Fluoran type represented by the following general formula Leuco compound of dye: (2) In the formula, RX, RY and R2 are the same as in the above (a).

Specific examples of the above compounds are as follows.

3-Cyclohexylamino-6-chlorofluorane 3-
(N,N-diethylamino)-5-methyl-7-(N.

N-dibenzylamino)fluoran 3-dimethylamino-5,7-dimethylfluoran 3-
Diethylamino-7-methylfluoran 3-diethylamino-7,8-benzfluoran (c) Leuco compound of fluoran dye: 3-diethylamino-6-methyl-7-chlorofluoran 3-pyrrolidino-6-methyl-7 - anilinofluorane) lactone compound represented by the following general formula: in the formula, R
1 and R2 are hydrogen, a lower alkyl group, substituted -1 is an unsubstituted aralkyl group, a substituted or unsubstituted phenyl group,
represents a cyanethyl group or a β-halogenated ethyl group, or R1 and R2 are bonded, -c
+v, -(-CH2-37-also 6CH2 amount cmn2
%, R3 and R4 are hydrogen, lower alkyl group,
Represents an alkyl group, amine group or phenyl group, R3
Any one of and R4 is hydrogen, and X□, X2 and In the formula, X4 represents hydrogen, halogen, a lower alkyl group or a lower alkoxyl group, and n represents 0 or an integer of 1 to 4.

Specific examples of the above compounds are as follows.

3- (2'-Hydroxy-4'-dimethylaminophenyl) -3-(2'-methoxy-57-chlorophenyl)phthalide 3- (2'-hydroxy-4'-dimethylaminophenyl) -3-(2 '-Methoxy-5'-nitrophenyl)phthalide 3-(2'-hydroxy-41-diethylaminophenyl) -3-(2'-methoxy-5'-methylphenyl)phthalide 3- (2'-methoxy-4 '-dimethylaminophenyl) -3-(2'-hydroxy-4'-chloro-5'
-methylphenyl)phthalide.

(6) Acidic Substances The following various acidic substances can be used as acidic substances that react with the above-mentioned leuco dye to develop color when heated.

(a) Organic and inorganic acids boric acid, oxalic acid, maleic acid, tartaric acid, citric acid, co-phosphoric acid, benzoic acid, stearic acid, gallic acid, salicylic acid, 1-hydroxy-2-naphthoic acid, 0-hydroxy Benzoic acid, m-hydroxybenzoic acid, 2-hydroxy-p-toluic acid.

(b) Phenolic substances 3.5-xylenol, thymol, p-tert-butylphenol, 4-hydroxyphenoxide, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, α-naphthol, β-naphthol, catechol, resorcin, hydroquinone , 4-tert-octinol, 2.2'-dihydroxydiphenyl, 2.2
'-methylenebis(4-methyl-6-tert-butylphenol), 2,2-bis(4-hydroxyphenyl)propane, 4,4-isopropylidene-bis(2-t
ert-butylphenol), 414-BeC-butylidene diphenol, pyrogallol, phloroglucin, phloroglucin carboxylic acid.

(0 Binder As the binder for bonding and supporting the thermosensitive coloring layer on the support, various binders as shown below can be used.

Water-soluble ones such as polyvinyl alcohol, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch, gelatin, etc.
Alternatively, an aqueous emulsion such as polystyrene, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, etc. can be used as the binder.

0 Filler The heat-sensitive recording material of the present invention further contains fillers such as calcium carbonate, silica, alumina, magnesia, talc, kaolin, barium sulfate, urea-formalin resin, styrene resin, etc. in the heat-sensitive layer, if necessary. By adding fine powder, the clarity of the colored image and the running performance of the thermal head can be further improved.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 A mixture of the following components was ground for 24 hours using a ball mill to prepare an aqueous dispersion ah, B.

[Dispersion A]

Crystal violet lactone 1.5 parts by weight 5
Tivoli vinyl alcohol aqueous solution 5.0 water
43.5
n [Dispersion B] Bisphenol A 6.0 5 Tivolivinyl alcohol water m liquid to.

〃Water 3
4.

The aqueous dispersions A and B prepared as above were each subjected to a membrane filter treatment,
Aqueous dispersions A and B with particle sizes adjusted to a range of 1 to 2 μm were obtained. These aqueous dispersions A and B whose particle sizes have been adjusted are mixed in equal weight to prepare a thermosensitive coloring layer forming liquid, and then the thermosensitive coloring layer forming liquid is coated on the surface of commercially available high quality paper (5097m) using a wire bar. After drying, the adhesion amount was 5.0117
A heat-sensitive coloring layer having a solid content of m (solid content) was formed, and then calendered to obtain a Bekk smoothness of 200 to 300 seconds to obtain a heat-sensitive recording material.

Example 2 Aqueous dispersions C and D were prepared by pulverizing and dispersing a mixture consisting of the following components for 24 hours using a ball mill.

[Dispersion liquid C]

3-diethyl-6-methyl-7-anilino 1.5 parts by weight Fluorane 5-tipolyvinyl alcohol aqueous solution W s, o
tt water
43.5 // [Dispersion D] Bisphenol A 6.0 parts by weight Calcium carbonate 2.5〃5 Polyvinyl alcohol aqueous solution 10. Ott water
31.5 u
The above aqueous dispersion C was filtered using a membrane filter in the same manner as in Example 1.
, D' to obtain an aqueous dispersion with a particle size adjusted to a range of 1 to 2 μm, and then mix equal weights of each g to prepare a thermosensitive coloring layer forming liquid. A heat-sensitive recording material was produced in the same manner as in Example 1 using the layer forming liquid.

Comparative Example 1 The aqueous dispersions A and B of Example 1 were pulverized and dispersed in a ball mill for 24 hours without being passed through a membrane filtration device, and then mixed in equal weights to form a thermosensitive coloring layer forming liquid. (The particle size range was 0.1 to 18 μm), and using this, a comparative heat-sensitive recording material was obtained in the same manner as in Example 1.

Comparative Example 2 The aqueous dispersions A and B of Example 1 were each passed through a membrane, the particle sizes of the aqueous dispersions A and B were adjusted to a range of 3 to 6 μm, and these were mixed in equal weight to form a thermosensitive A coloring layer forming liquid was obtained.

Using this, a heat-sensitive recording material was obtained in the same manner as in Example 1.

Comparative Example 3 The aqueous dispersions A and B of Example 1 were each passed through a membrane sieve to adjust the particle size to a range of 0.1 to 2μ, and then mixed in equal weights to form a thermosensitive coloring layer forming liquid. Obtained.

Next, using this, a heat-sensitive recording material was obtained in the same manner as in Example 1.

Comparative Example 4 The aqueous dispersions C and D of Example 2 were mixed in equal weights in a kneaded state without filtration treatment, and the particle size range was 0.1.
A thermosensitive coloring layer forming solution of ~23μ was obtained.

Using this, a heat-sensitive recording material was obtained in the same manner as in Example 1.

The heat-sensitive recording papers of Examples 1 to 2 and Comparative Examples 1 to 4 produced as described above were sent to a facsimile machine (Oki Electric Industry Co., Ltd.: 0KIFAX-7100) for 12 minutes.
High-speed printing was performed under the condition of 5 V to obtain a colored image. The measurement results of image density (Macbeth densitometer RC-514, yellow filter used) and background density (Photovolt densitometer, green filter used) are shown in Table 1. From the table, it can be seen that the recording material of the present invention has low background fog, high image density, and provides clear images.

Patent applicant Ricoh Co., Ltd. Agent: Patent attorney: Toshiaki Ikeura

Claims (1)

[Claims] (1) In a heat-sensitive recording material having a structure in which a heat-sensitive coloring layer containing a leuco dye and an acidic substance that causes the leuco dye to develop color when heated is formed on a support, the particle size of the leuco dye and the acidic substance is A heat-sensitive recording material characterized by using a material having a particle size in the range of 1 to 2μ.