JPS5822197A - Heat-sensitive recording material - Google Patents

Abstract

PURPOSE:To obtain a heat-sensitive recording material having improved heat respondence and dust adherence by combined use of a p-oxybenzoate as a developing substance and a heat-meltable substance having a specific melting point. CONSTITUTION:In a heat-sensitive recording material in which a heat sensitive coloring layer containing as main components a colorless or light-color coloring agent[e.g., 3,3-bis(p-dimethylaminophenyl)-phthalide, 3-cyclohexylamino-6-chlorfluoran, etc.]and a developing substance capable of coloring said coloring agent when being heated is formed on a supporter, as the developing substance, a p- benzoate of the formula (where R is a C2-C4 alkyl or benzyl) (e.g., ethyl p- oxybenzoate, benzyl p-oxybenzoate, etc.) is used, and a heat-meltable substance of a melting point of 80-150 deg.C (e.g., stearic acid amide, etc.) as a sensitizer is added to said heat-sensitive coloring layer. Thus, a heat-sensitive recording material which is high in heat respondence and the uniformity of color image and also less in the adherence of dust to head can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, and more specifically, the present invention relates to a heat-sensitive recording material, and more specifically, a color-forming substance that is usually colorless or slightly pale in color and a color-developing substance that causes the color-forming substance to develop color when heated are used as color-forming components. It relates to a heat-sensitive recording material comprising a heat-sensitive coloring layer containing a heat-sensitive coloring layer provided on a support.

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 the diversification and increase of information, resource conservation, and pollution-free technology. Among them, thermal recording materials (1) A colored image is recorded simply by heating, eliminating the need for the current 11 complicated steps; (2) it can be manufactured using a relatively simple and compact device;
Furthermore, the resulting recording material is easy to handle and maintenance costs are low; (3) paper is often used as a support; in this case, not only is the support cost low;
, i', The feel of the recorded recording material is similar to that of plain paper, etc., which is useful in the fields of computer output, printers such as calculators, recorders for medical measurement, low and high speed facsimile fields, and automatic ticket vending. It is widely used in the mechanical field, thermal copying field, etc.

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

Conventional examples of such heat-sensitive recording materials include, for example,
Examples include heat-sensitive recording materials disclosed in Japanese Patent Publication No. 3-4160 or Japanese Patent Publication No. 45-14039. In such conventional heat-sensitive recording materials, components in the heat-sensitive coloring layer melt due to heating during recording, resulting in a thermal head or a thermal pen. Adhesion (residue adhesion) may cause problems with paper feeding, resulting in a sticking phenomenon, or the adhesive may transfer to the recording material and cause trailing, or the adhesive may accumulate and reduce the density of the colored image. This may reduce sharpness or cause distortion. These properties are called head matching properties,
This is extremely important when considering the quality of heat-sensitive recording sheets. Moreover, these conventional heat-sensitive recording materials have low thermal responsiveness, and as recording speeds increase, sufficient recording density and sharpness cannot be obtained.

As a method to improve such drawbacks, for example, Japanese Patent Application Laid-Open No. 1986-
No. 19231 discloses that the thermosensitive coloring layer has a melting point of 40 to 10.
A method for improving heat responsiveness by incorporating waxes at 0°C is described, and in Japanese Patent Publication No. 51-27599, fatty acid amide and petroleum wax are used in combination in a heat-sensitive coloring layer to improve heat responsiveness and cast. Although methods for improving adhesion have been described, none of them are sufficient to improve the adhesion, especially head matching properties such as scum adhesion, sticking, trailing, and unsharpness of one image, thermal response, and uniformity of colored images. With regard to performance, it is not possible to obtain sufficiently satisfactory results using only the techniques disclosed in such publications.

In view of the current situation, the inventors of the present invention have conducted various studies and have found that
It was discovered that the above-mentioned problems could be solved by using p-oxybenzoic acid ester as a color developing substance and using it in combination with a thermofusible substance having a melting point of 80 to 150°C, and in order to complete the present invention. It has arrived. That is, according to the present invention, a thermosensitive color-forming layer having a structure formed on a support, the heat-sensitive color-forming layer mainly consisting of a normally colorless or slightly light-colored color-forming substance and a color-developing substance that can cause the color-forming substance to develop color when heated. In heat-sensitive recording materials,
A p-oxybenzoic acid ester represented by the general formula (wherein R represents an alkyl group having 2 to 4 carbon atoms or a benzyl group) is used as the color developing substance, and a melting point of 80 to 80 is used in the thermosensitive coloring layer. A heat-sensitive recording material is provided, characterized in that it contains a substance that is thermofusible at 150°C.

Specifically, p-oxybenzoic acid esters represented by the above general formula include ethyl p-oxybenzoate (M, P, 116-
118℃) n-propyl p-oxybenzoate (M, P
, 96-98°C) isopropyl p-oxybenzoate
(M, P, 84-86°C) n-butyl p-oxybenzoate (M, P, 69-72°C) Inbutyl p-oxybenzoate (M, P, 75-77°C) Benzyl p-oxybenzoate (M, P, lt1°C). In the present invention, p-oxybenzoic acid ester is used in an amount of 0.5 to 10 parts by weight, preferably 1 to 1 part by weight, per 1 part by weight of a color-forming substance such as a leuco dye listed below.
5 parts by weight are used.

The thermofusible substance contained in the thermosensitive coloring layer together with the color developing substance described above acts as a sensitizer and functions to enhance the thermal responsiveness of the thermosensitive coloring layer. As the thermofusible substance, any substance can be used as long as it exists as a solid at room temperature, does not cause a significant coloring reaction when it comes into contact with a coloring substance, and melts at a temperature of 80 to 150°C. However, preferred examples include:

N-stearylcarbamoylbenzene (m, p, 86~
87℃) Stearic acid amide (m, p, 97-9
8℃) dimethyl terephthalate) (m, p,
141-142℃) p-toluenesulfonamide
(m, p, 137.5°C) Phthalonitrile (
m, p, 141°C) methylolated stearamide
(m, p, 107-110°C) ethylene bisstearamide (m, p, 140°C) CH3(CH,,)2
1NH-CO-CH3 (m, p, 86.5-87.5℃
)CHs(CH2)+tNH-CO-CH2<◇(m,
p, 93 to 94°C) The thermofusible substance is usually 0.1 to 5 parts by weight, preferably 0.2 to 5 parts by weight, per 1 part by weight of p-hydroxybenzoic acid ester.
2 parts by weight are used.

As the color-forming substance used in the present invention, any substance can be used as long as it develops color when heated with p-hydroxybenzoic acid ester as the color-developing substance, including triphenylmethane, fluoran, and phenothiazine. system,
Auramine-based and spiropyran-based leuco dyes are preferably applied.

Specific examples of these leuco dyes are shown below.

As leuco dyes, there are usually colorless or light-colored leuco forms of various dyes shown below.

(a) Leuco compound of triphenylmethane dye represented by the following general formula: Rz (wherein RX, RY and RZ are hydrogen, hydroxyl group), rogene, alkyl group, nitro group, amine group, dialkylamine group, Monoalkyl group, allyl group. ) Specific examples of the above 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-dimethylamino phenyl)-6-dibutylaminophenyl 3.3-bis(p-dimethylaminophenyl)-6-chlorophthalide 3.3-bis(p-dibutylaminophenyl)phthalide (b) Fluoran dyes represented by the following general formula Leuco compound: Rz In the formula, Rx, RY and Rz are the same as in the case of 0) above.

Specific examples of the above compound 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-diethylamine-7,8-benzfluoran f→ Leuco compound of fluoran dye :3-diethylamino-6-methyl-7-chlorofluoran 3-pyrrolidino-6-methyl-7-anilinofluoran 2-(N-(3'-to!)
j 〕 methyl phenyl amine)-, 6-dinithylaminofluorane 2-(3.6-bis(diethylamino)-9-(0-chloroanilino)xanthylbenzoic acid lactam) represented by the following general formula Lactone compound: (X4
> n In the formula, R7 and R represent hydrogen, a lower alkyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted phenyl group, a cyanethyl group, or a β-halogenated ethyl group, or R1 and R2 is combined with +CHt+4. −
(-CH2 also represents +cH2+r04 CH2'%, R3 and R4 represent hydrogen, lower alkyl group, alkyl group, amino group or phenyl group, either one of R3 and R4 is hydrogen, X, X2 and X3
is hydrogen, lower alkyl group, lower alkoxyl group, halogen atom, halogenated methyl group, nitro group, amine group,
It also represents a substituted amino group, X4 represents hydrogen, halogen, a lower alkyl group or a lower alkoxyl group, and n represents 0 or an integer of 1-4.

Specific examples of the above compounds are as follows.

3-(2'-hydroxy-4'-dimethylaminophenyl) -3-(2'-methoxy-5'-chlorophenyl)phthalide 3- (2'-hydroxy-4'-dimethylaminophenyl) -a-( 2'-methoxy-5-nitrophenyl)
Phthalide 3-(2+-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl)
7Thallide 3 (21-methoxy-41-dimethylaminophenyl)
-3-(2'-hydroxy-4'-chloro-5'-methylphenyl)phthalide.

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

Polyvinyl alcohol, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch, starch derivatives, gelatin, styrene.
Water-soluble ones such as maleic anhydride copolymer, inbutylene-maleic anhydride copolymer, etc., or polystyrene, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, SBR, latex, styrene-acrylic ester An aqueous emulsion, such as, can be used as a binder.

In addition, if necessary, the heat-sensitive coloring layer may contain conventional auxiliary additives, such as calcium carbonate, clay, Merck, zinc oxide, polystyrene pigment, urea-formalin resin pigment, etc. for whitening and improving writability. It is also possible to add inorganic organic pigments, and waxes such as polyethylene wax, baraki wax, carnauba wax, montan wax, and higher fatty acid metal salts to improve head matching properties.

Generally known methods can be used to obtain the heat-sensitive recording material of the present invention using the various heat-sensitive color forming layer forming components. That is, a color-forming substance, a color-developing substance, a binder,
Fillers and other additives are added alone or in a mixture except for color-forming substances to an aqueous medium together with a protective colloid substance such as polyvinyl alcohol, a surfactant, etc.
Grind and disperse using a dispersing machine such as a ball mill, attritor, or sand mill. Next, each dispersion liquid is mixed to prepare a heat-sensitive color forming layer coating liquid, which is coated on a support such as paper, synthetic paper, or plastic film, and is manufactured by drying.

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

Example 1 A mixture having the following composition was separately ground for 24 hours using a ball mill to prepare a liquid A and a liquid B.

[Liquid A]

3-Cyclohexylamino-6-methyl-7-anilinofluorane 1.5 parts by weight 2
0% polyvinyl alcohol aqueous solution s, o s water
43.5 parts by weight [Liquid B] Benzyl p-oxybenzoate 6.0 parts by weight N-stearyl (p-methoxycarbonyl)benzoylamide 1.0
Calcium carbonate 1.0 Calcium stearate 1.0 10th grade polyvinyl alcohol aqueous solution s, op water
37.5 #Next, 1.0 part by weight of the above liquid A and 1.0 part by weight of liquid B were mixed to prepare a thermosensitive coloring layer forming liquid, and this was coated in a dry coating amount of 5 g.
/771' commercially available high-quality paper (average basis weight 50/m
) and dried to form a heat-sensitive coloring layer to obtain the heat-sensitive recording material of the present invention.

Example 2 A mixture having the following composition was separately ground for 24 hours using a ball mill to prepare Solution C.

[Liquid C]

Benzyl p-oxybenzoate 6.0 parts by weight Dimethyl terephthalate 1.0I Calcium carbonate 1.0 parts by weight Calcium stearate 1.0 #10 Polyvinyl alcohol aqueous solution s, o #Water
37,5 #Above liquid C 1
．． 0 parts by weight and 1.0 parts by weight of liquid A of Example 1 were mixed to prepare a thermosensitive coloring layer forming liquid, and this was coated in a dry coating amount of 5 g.
/m'' using commercially available high-quality paper (average basis weight 50 g/m
'') and dried to form a heat-sensitive coloring layer, thereby obtaining a heat-sensitive recording material of the present invention.

Comparative Example 1 A comparative heat-sensitive recording material was obtained in exactly the same manner as in Example 1 except that stearyl (p-methoxycarbonyl) benzoylamide in liquid B was omitted.

The performance of the thermal recording paper of the present invention and the comparative thermal recording paper prepared as described above was tested. The results are summarized in Table-1.

The coloring characteristics are measured at 60°C or higher using Toyosei S@) Clear Incline Tester.
Color was developed by contacting with 2 kg An for 1 sec in a range of 150°C, and the density was measured using a Macbeth densitometer RD-514 (filter W-106) to obtain color density (versus) temperature characteristics. Maximum color density at this time: Saturation color density Heat Sensitivity: # degree -0.8 temperature Color development start temperature:
・Defined as the temperature at which a concentration of -0.2 is obtained. Therefore thermal sensitivity,
The lower the color development start temperature, the better the sensitivity. Thermal response (recording density) was measured using a G-1 mode facsimile test machine with a thin film head (current application time to the resistor was 2.2 ms, 0
．． 5w/1 dot), solid black printing was performed, and the recording density is shown. The uniformity of the colored image was evaluated by evaluating the uniformity of a solid black image. The adhesion of head debris was recorded using the test machine described above in a checkered pattern over a distance of 1 m to evaluate the amount of debris adhering to the head.

As can be seen from Table 1, it was confirmed that the thermal recording paper of the present invention had high thermal responsiveness, high uniformity of colored images, and little residue adhesion to the head.

Claims (1)

[Claims] (1) In a heat-sensitive recording material having a structure in which a heat-sensitive color-forming layer is formed on a support, the main components being a normally colorless or slightly light-colored color-forming substance and a color-developing substance that can cause the color-forming substance to develop color when heated, As the color developing material, a p-oxybenzoic acid ester represented by the general formula (wherein R represents an alkyl group having 2 to 4 carbon atoms or a benzyl group) is used, and a melting point in the thermosensitive coloring layer is used. 1. A heat-sensitive recording material characterized by containing a thermofusible substance having a temperature of 80 to 150°C. ,