JPH0867069A - Thermosensitive recording medium - Google Patents

Abstract

PURPOSE: To enhance optical readability by providing a thermosensitive color developing layer containing a fluoran derivative which is a basic dye and diphenylsufone derivative which is a coloring agent, on a support. CONSTITUTION: A thermosensitive color developing layer containing at least, one type of a fluoran derivative expressed by formula I (R1 , R2 are a C1 to C6 alkyl group, an ethoxypropyl group and a p-toluidino group; R3 is a C1 to C12 alkyl group and a benzyl group) and a diphenylsulfone derivative expressed by formula II (R4 , R5 are a C1 to C4 alkyl group, a C2 to C4 alkenyl group, a C1 to C4 alkoxyl group, a benzyloxy group, a halogen atom; m is an integer of 0 to 2; n is an integer of 1 to 3; and p, q are integers of 0 to 2), is laminated on a support to form a thermosensitive recording medium. This thermosensitive recording medium has a long lasting readability to optical character reading in a wavelength region of 650 to 700nm, if exposed to high temperature and high humidity for a long time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material utilizing a color reaction between a colorless or light-colored basic dye and a color developing agent, and particularly, it is suitable for optical character reading (OCR) in the wavelength region of 650 to 700 nm. The present invention relates to an excellent thermal recording material.

[0002]

2. Description of the Related Art A thermosensitive recording medium is known in which a color or color reaction between a colorless or pale basic dye and an organic or inorganic coloring agent is used to bring a color image into contact with each other to obtain a recorded image. Has been. Since such a thermal recording material is relatively inexpensive and the recording device is compact and its repair is relatively easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields.

With the recent diversification of needs, various performances are required for the thermal recording material. As one of them, there is a demand for a thermal recording material for OCR or OMR which has a black color tone and is readable in the wavelength region of 650 to 700 nm. As a method for obtaining such a heat-sensitive recording material, the coating amount of the black-coloring fluoran dye which has been conventionally used is simply increased, or 65 is applied at the time of coloring.
Examples of the dye having a strong absorption at 0 to 700 nm include 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide or 3-di-n-butylamino-6,8,8-trimethyl-8. , 9-dihydro-
A method is used in which (3,2, e) pyridofluorane or the like is used in combination with a black coloring fluorane dye. However, although these methods have the OCR suitability immediately after color development, if they are stored at high temperature or high humidity for a long time, the OCR suitability is lost, or the white paper part develops color (background fog), and therefore its improvement is strongly demanded. ing. Further, Japanese Patent Application Laid-Open No. 2-12085 discloses a thermosensitive recording medium using a dye represented by the above general formula (1) as a colorless or light-colored basic dye. There's a problem.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a thermal recording material having excellent suitability for optical character reading (OCR) in the wavelength region of 650 to 700 nm.

[0005]

DISCLOSURE OF THE INVENTION The present inventors have proposed a thermosensitive recording medium comprising a support and a recording layer containing a colorless or light-colored basic dye and a color developing agent. By using at least one of the fluorane derivatives represented by the following general formula (1) as the functional dye and incorporating the diphenylsulfone derivative represented by the following general formula (2) as the colorant, the above problems can be solved. The present invention has been completed and the present invention has been completed.

[0006]

[Chemical 4] [Wherein R ₁ and R ₂ are each a C _{1 1} C ₆ alkyl group, an ethoxypropyl group or a p-toluidino group;
₃ represents a C ₁ -C ₁₂ alkyl group, a benzyl group or a phenethyl group. ]

[0007]

[Chemical 5]

[In the formula, R ₄ and R ₅ are respectively C _{1 to} C ₄
Alkyl group, an alkenyl group of C ₂ -C ₄ of, C ₁ -C ₄
Represents an alkoxyl group, a benzyloxy group or a halogen atom. m is an integer of 0 to 2, n is an integer of 1 to 3, p,
q shows the integer of 0-2, respectively. ]

That is, according to the present invention, by using a specific fluorane derivative as a colorless or light-colored basic dye and a specific diphenylsulfone derivative as a color-developing agent, exposure to high temperature or high humidity for a long time is made. Even 65
It is possible to obtain a black color-type heat-sensitive recording material in which the suitability for optical character reading (OCR) in the wavelength range of 0 to 700 nm is not deteriorated and the background fog is small.

[0010]

The following are specific examples of the fluoran derivative represented by the general formula (1) used in the present invention. 4-methylamino-8-diethylamino-benzo [a] fluorane, 4-isopropylamino-8-diethylamino-benzo [a] fluorane, 4
-Isobutylamino-8-diethylamino-benzo [a] fluorane, 4-t-butylamino-8-diethylamino-benzo [a] fluorane, 4-n-octylamino-8-diethylamino-benzo [a] fluorane, 4- Isooctylamino-8-diethylamino-benzo [a] fluorane, 4-t-octylamino-8-
Diethylamino-benzo [a] fluorane, 4-isononylamino-8-diethylamino-benzo [a] fluorane, 4-n-dodecylamino-8-diethylamino-
Benzo [a] fluorane, 4-benzylamino-8-diethylamino-benzo [a] fluorane, 4-phenethylamino-8-diethylamino-benzo [a] fluorane, 4-isooctylamino-8-di-n-butylamino -Benzo [a] fluorane, 4-benzylamino-8
-Di-n-butylamino-benzo [a] fluorane, 4
-Phenethylamino-8-di-n-butylamino-benzo [a] fluorane, 4-n-dodecylamino-8-di-n-pentylamino-benzo [a] fluorane, 4-
Benzylamino-8-di-n-pentylamino-benzo [a] fluorane, 4-phenethylamino-8-di-n
-Pentylamino-benzo [a] fluorane, 4-benzylamino-8- (N-ethyl-N-isoamyl) amino-benzo [a] fluorane, 4-phenethylamino-
8- (N-ethyl-N-isoamyl) amino-benzo [a] fluorane, 4-benzylamino-8- (N-ethyl-N-ethoxypropyl) amino-benzo [a] fluorane, 4-phenethylamino-8 -(N-ethyl-
N-ethoxypropyl) amino-benzo [a] fluorane, 4-benzylamino-8- (N-methyl-Nn-)
Propyl) amino-benzo [a] fluorane, 4-phenethylamino-8- (N-methyl-Nn-propyl)
Amino-benzo [a] fluorane, 4-benzylamino-8- (N-ethyl-p-toluidino) -benzo [a]
Fluorane, 4-phenethylamino-8- (N-ethyl-p-toluidino) -benzo [a] fluorane, 4-isooctylamino-8- (N-ethyl-p-toluidino) -benzo [a] fluorane, 4 -N-dodecylamino-8- (N-ethyl-p-toluidino) amino-benzo [a] fluorane and the like. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

Of these, the compounds represented by the following general formula (3) are preferably used because they are particularly excellent in terms of color developability and background fog.

[0012]

[Chemical 6] [In the formula, R ₆ and R ₇ each represent a C _{1 to} C ₆ alkyl group, and R ₈ represents a benzyl group or a phenethyl group. ]

Further, among the compounds represented by the general formula (3), 4-benzylamino-8-diethylamino-benzo [a] fluorane is particularly preferable because it is excellent in color developability.

In the present invention, as the basic dye known in the range that does not impair the desired effects of the present invention, for example, triarylmethane compounds, fluorane compounds, phenothiazine compounds, rhodamine lactam compounds, spiropyran compounds, etc. It is also possible to use together.

In the heat-sensitive recording material of the present invention, the specific fluoran derivative as described above is selectively combined with the diphenylsulfone derivative represented by the above-mentioned general formula (2) as a coloring agent to obtain the OCR readability. However, the following are specific examples of such a diphenyl sulfone derivative.

4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 3,
3'-diallyl-4,4'-dihydroxydiphenyl sulfone, 3,3 ', 5,5'-tetrabromo-4,4'
-Dihydroxydiphenyl sulfone, 3,3 ', 5,
5'-tetrachloro-4,4'-dihydroxydiphenyl sulfone, 4-hydroxydiphenyl sulfone, 4-
Hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-3 ', 4'-tetramethylene diphenyl sulfone, 4-hydroxy-4'-methoxydiphenyl sulfone, 4-hydroxy-4'-ethoxydiphenyl sulfone, 4-hydroxy- 4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-n-butoxydiphenyl sulfone, 4-hydroxy-4'-benzyloxydiphenyl sulfone, 3,4-dihydroxydiphenyl sulfone, 3,4-dihydroxy-4'- Methyldiphenyl sulfone, 3,4,4'-trihydroxydiphenyl sulfone, 3,4,3 ', 4'-tetrahydroxydiphenyl sulfone, 2,3,4-trihydroxydiphenyl sulfone and the like. Of course, it is not limited to these, and it is also possible to use two or more kinds together if necessary.

Among these diphenyl sulfone derivatives, 3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone and 4-hydroxy-4'-isopropoxydiphenyl sulfone are In particular, it is more preferably used because a heat-sensitive recording material having a good storability on a blank sheet and a recording sensitivity and an OCR readability at high temperature or high humidity can be obtained. In the present invention, the specific diphenylsulfone derivative as described above is selectively used as a color-developing agent, but other known color-developing agents are used in combination within a range that does not inhibit the desired effect of the present invention. It is also possible to do so.

The heat-sensitive recording material of the present invention is generally a medium in which a binder is dissolved or dispersed, and a fluoran derivative represented by the general formula (1) as a basic dye and the general formula ( It is produced by applying a coating solution obtained by dispersing fine particles of the diphenylsulfone derivative represented by 2) onto a suitable support.

The use ratio of the basic dye and the coloring agent in the recording layer is not particularly limited, but generally 1 to 10 parts by weight, and preferably 2 to 5 parts by weight of the coloring agent per 1 part by weight of the dye. Is used. The coating liquid containing them is generally prepared by dispersing the dye and the color former together or separately by using water as a dispersion medium and a stirring / pulverizing machine such as a ball mill, an attritor or a sand mill.

In such a coating liquid, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene / maleic anhydride copolymer salt, styrene / acrylic acid copolymer are usually used as binders. Combined salt, styrene-butadiene copolymer emulsion, etc. are 10 to 40% by weight of the total solid content, preferably 15 to 3%.
About 5% by weight is used.

Further, various auxiliary agents can be added to the coating liquid, for example, dispersion of sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate / sodium salt, fatty acid metal salt and the like. Agent, UV absorbers such as triazoles,
Other examples include defoaming agents, fluorescent dyes, coloring dyes and antioxidants. Also, in order to prevent sticking of the thermal recording material due to contact with recording equipment or recording heads, use a dispersion or emulsion of stearic acid, polyethylene, carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax, etc. in the paint. It can also be added.

Further, in the heat-sensitive recording material of the present invention,
The recording layer may contain the following compounds as a recording sensitivity improver. Caproic acid amide, capric acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, linoleic acid amide, linolenic acid amide, N-methylstearic acid amide, stearic acid anilide, N-methyloleic acid amide, Benzanilide, linoleic acid anilide, N-ethylcapric acid amide, N-butyllauric acid amide, N
-Octadecylacetamide, N-oleinacetamide, N-oleylbenzamide, N-stearylcyclohexylamide, polyethylene glycol, 1-benzyloxynaphthalene, 2-benzyloxynaphthalene,
1-Hydroxynaphthoic acid phenyl ester, 1,2-
Diphenoxyethane, 1,4-diphenoxybutane,
1,2-bis (3-methylphenoxy) ethane, 1,2
-Bis (4-methoxyphenoxy) ethane, 1-phenoxy-2- (4-chlorophenoxy) ethane, 1-phenoxy-2- (4-methoxyphenoxy) ethane, 1-
(2-Methylphenoxy) -2- (4-methoxyphenoxy) ethane, terephthalic acid dibenzyl ester, oxalic acid dibenzyl ester, oxalic acid di (4-methylbenzyl) ester, p-benzyloxybenzoic acid benzyl ester, p -Benzylbiphenyl, 1,5-bis (p
-Methoxyphenoxy) -3-oxa-pentane, 1,
4-bis (2-vinyloxyethoxy) benzene, p-
Biphenyl-p-tolyl ether, benzyl-p-methylthiophenyl ether, 2- (2'-hydroxy-
5'-methylphenyl) benzotriazole, 2-hydroxy-4-benzyloxybenzophenone and the like.

Further, in the heat-sensitive recording material of the present invention, in order to further improve the image storability, the following compounds may be contained in the recording layer as a recording storability improver. 2,2'-methylenebis (4-methyl-6-
t-butylphenol), 2,2'-methylenebis (4
-Ethyl-6-t-butylphenol), 2,2'-ethylenebis (4,6-di-t-butylphenol),
4,4'-thiobis (3-methyl-6-t-butylphenol), 4,4'-thiobis (2-methyl-6-t-)
Butylphenol), 4,4'-butylidene bis (6-
t-butyl-m-cresol), 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4)
-Hydroxy-5-t-butylphenyl) butane, 1-
[Α-Methyl-α- (4′-hydroxyphenyl) ethyl] -4- [α ′, α′-bis (4 ″ -hydroxyphenyl) ethyl] benzene, 2,2′-methylenebis (4,6-di) -T-butylphenyl) sodium phosphate, 2,2'-methylenebis (4,6-di-t-butylphenyl) magnesium phosphate, cresol novolac type epoxy resin, p-hydroxydiglycidyl ether, 4,4'- Diglycidyloxydiphenyl sulfone, 4-benzyloxyphenyl-4 '-(2-methyl-2,3-epoxypropyloxy) phenyl sulfone, etc. Although the amount of the recording storage improver used is not particularly limited. In general, it is desirable to use 5 to 200 parts by weight, preferably 10 to 100 parts by weight, based on 100 parts by weight of the basic dye.

In addition, kaolin, clay, talc, calcium carbonate,
It is also possible to add an inorganic pigment such as calcined clay, titanium oxide, diatomaceous earth, particulate anhydrous silica, activated clay.

The support may be paper, plastic film, synthetic paper, or a plastic film or synthetic paper laminated with coated paper or high-quality paper via an adhesive, or a paper laminated with plastic. used. Examples of such plastic film include films of polyethylene, polyester, polypropylene, polyvinyl chloride, polystyrene, nylon and the like. As the synthetic paper, for example, synthetic paper manufactured by the film method or the fiber method is used.
The film method includes an internal paper making method in which a synthetic resin, a filler, and an additive are melt-kneaded and then extruded to form a film, a surface coating method in which a pigment coating layer is provided, a surface treatment method, and the like. Include synthetic pulp paper and spunbond paper.

The coating method of the recording layer is not particularly limited, and it can be formed according to a conventionally known and commonly used technique, for example, bar coating, air knife coating, rod blade coating, pure blade coating, short dwell coating. It is formed by a method of applying and drying the coating liquid by the above method. When a plastic film is used as the support, the coating efficiency can be increased by subjecting the surface to treatments such as corona discharge and electron beam irradiation. The coating amount of the coating liquid is also not particularly limited, but it is usually ^{2 to} 10 g / m ² , preferably 3 to 7 g in dry weight.
It is adjusted in the range of about / m ² .

Further, by providing a protective layer composed of an adhesive, a lubricant, a pigment and the like on the thermosensitive recording layer, a thermosensitive recording material excellent in chemical resistance against plasticizer, oil and the like can be obtained. Specific examples of the adhesive used in the protective layer include polyvinyl alcohols having various degrees of saponification, acetoacetyl group-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, acrylic resin, and polyurethane resin. Further, it is desirable that these adhesives are adjusted in the range of 10 to 95% by weight, preferably 30 to 90% by weight, based on the total solid content. The coating amount of the protective layer is 0.5 to 10 by dry weight.
g / m ^2, it is adjusted preferably, 1 to 7 g / m ² range of about.

In addition, a layer containing a water-soluble, water-dispersible, electron beam curable or ultraviolet curable resin may be provided on the protective layer for the purpose of imparting high gloss, etc. It is of course possible to provide a protective layer on the back surface of the recording medium or to provide an undercoat layer on the support, and various known techniques in the field of producing a thermosensitive recording medium can be added.

[0029]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, parts and% in examples are parts by weight and% by weight, respectively.

Example 1 [Preparation of solution A] 10 parts of 4-benzylamino-8-diethylamino-benzo [a] fluorane, 1,2-bis (3-)
A composition consisting of 25 parts of methylphenoxy) ethane, 10 parts of a 5% aqueous solution of methylcellulose, and 55 parts of water was pulverized with a sand mill until the average particle size became 0.9 μm.
A liquid was obtained.

[Preparation of solution B] 3,3'-diallyl-4,
A composition consisting of 20 parts of 4'-dihydroxydiphenyl sulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 55 parts of water was pulverized with a sand mill until the average particle size was 1.2 μm, to obtain a liquid B.

[Formation of Recording Layer] Liquid A 100 parts, Liquid B 80
Parts, light calcium carbonate 10 parts, fine particle silicon oxide pigment (oil absorption 180 ml / 100 g) 20 parts, zinc stearate 3
15 parts of 0% dispersion and 15 parts of polyvinyl alcohol
% Coating solution obtained by mixing and stirring 100 parts of 50% aqueous solution.
dry weight fine paper g / m ² is applied and dried so as to 4g / m ^2, to obtain a heat-sensitive recording material by super calendering.

Examples 2 to 7 Thermosensitive recording materials were prepared in the same manner as in Example 1 except that the following compounds were used in place of 4-benzylamino-8-diethylamino-benzo [a] fluorane in the preparation of solution A. Obtained. Example 2: 4-Benzylamino-8-di-n-butylamino-benzo [a] fluorane Example 3: 4-Benzylamino-8- (N-ethyl-N)
-Isoamyl) amino-benzo [a] fluorane Example 4: 4-phenethylamino-8-diethylamino-benzo [a] fluorane Example 5: 4-phenethylamino-8- (N-ethyl-
N-isoamyl) amino-benzo [a] fluorane Example 6: 4-isooctylamino-8-diethylamino-benzo [a] fluorane Example 7: 4-n-dodecylamino-8- (N-ethyl-p- Toluidino) -benzo [a] fluorane

Examples 8 to 9 Thermal recording materials were prepared in the same manner as in Example 1 except that the following compounds were used in place of 3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone in the preparation of solution B. Got Example 8: 2,4'-Dihydroxydiphenylsulfone Example 9: 4-Hydroxy-4'-isopropoxydiphenylsulfone

Comparative Examples 1 to 3 Thermal recording was carried out in the same manner as in Example 1 except that the following compounds were used in place of 10 parts of 4-benzylamino-8-diethylamino-benzo [a] fluorane in the preparation of solution A. Got the body Comparative Example 1: 3-di-n-butylamino-6-methyl-7
-Anilinofluorane 10 parts Comparative Example 2: 3-di-n-butylamino-6-methyl-7
7 parts of anilinofluorane and 3 parts of 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide Comparative Example 3: 3-di-n-butylamino-6-methyl-7
7 parts of anilinofluorane and 3-di-n-butylamino-6,8,8-trimethyl-8,9-dihydro- (3,
2, e) Pyridfluorane 3 parts

Comparative Example 4 Example 1 was repeated except that 4,4'-isopropylidenediphenol was used in place of 3,3'-diallyl-4,4'-dihydroxydiphenylsulfone in the preparation of solution C.
A thermosensitive recording medium was obtained in the same manner as described above.

The heat-sensitive recording material thus obtained was evaluated by the following methods, and the results are shown in Table 1. [PCS value] The PCS value is an index indicating the degree of readability of OCR. The PCS value represents the relative density difference between the recorded portion and the unrecorded portion, and is calculated by the following equation. PCS = (Rw-Rp) / Rw Rw represents the reflectance of the unrecorded portion, and Rp represents the reflectance of the recorded portion. Therefore, the higher the PCS value, the clearer the discrimination between the recorded portion and the unrecorded portion, and the higher the readability. Generally, the PCS value is 0.7 or more, preferably 0.8.
The above is required.

[Measurement of PCS value at 670 nm] Recording was carried out using a thermal recording evaluation device [TM-PMD type, manufactured by Okura Electric Co., Ltd., applied voltage 16 V, pulse cycle 0.51 ms, applied pulse width 0.3 ms]. The reflectance of the unrecorded area at a wavelength of 670 nm was measured with a spectrophotometer [U-3300, manufactured by Hitachi, Ltd.], and the PCS value was calculated from the value. The color tones of the obtained recorded images were all bluish black or black.

[Background Fogging] The unrecorded area was measured with a Macbeth densitometer [Macbeth RD-914 type, visual filter].

[Moisture resistance] After recording, after leaving for 72 hours at 40 ° C. and 90% RH, the PCS value and the background fog were measured.

[Heat resistance] After recording, after leaving at 60 ° C. for 72 hours, the PCS value and the background fog were measured.

[0042]

[Table 1]

[0043]

As is clear from the results of [Table 1], the thermosensitive recording medium of the present invention has a sufficiently high PCS value at 670 nm and little background fog even when it is stored at high temperature or high humidity for a long time. Met.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Danou Nobuhisa 4-3-1, Jokoji Temple, Amagasaki City, Hyogo Prefecture Shin-Oji Paper Co., Ltd. Kanzaki Mill

Claims (4)

[Claims] 1. A thermosensitive recording medium comprising a support and a recording layer containing a colorless or light-colored basic dye and a coloring agent, wherein a basic dye represented by the following general formula (1) is used in the recording layer. Using at least one of the fluoran derivatives represented,
A heat-sensitive recording material containing a diphenyl sulfone derivative represented by the following general formula (2) as a coloring agent. Embedded image [In the formula, R ₁ and R ₂ are each a C _{1 to} C ₆ alkyl group, an ethoxypropyl group or a p-toluidino group;
₃ represents a C ₁ -C ₁₂ alkyl group, a benzyl group or a phenethyl group. ] [Chemical 2] [In the formula, R ₄ and R ₅ each represent a C _{1 to} C ₄ alkyl group, a C _{2 to} C ₄ alkenyl group, a C _{1 to} C ₄ alkoxyl group, a benzyloxy group or a halogen atom.
m is an integer of 0 to 2, n is an integer of 1 to 3, and p and q are integers of 0 to 2, respectively. ] 2. The heat-sensitive recording material according to claim 1, wherein the fluoran derivative is a compound represented by the following general formula (3). [Chemical 3] [In the formula, R ₆ and R ₇ each represent a C _{1 to} C ₆ alkyl group, and R ₈ represents a benzyl group or a phenethyl group. ] 3. A fluorane derivative is 4-benzylamino-
The thermosensitive recording medium according to claim 1, which is 8-diethylamino-benzo [a] fluorane. 4. A diphenylsulfone derivative is 3,3′-
The heat-sensitive recording material according to claim 1, 2 or 3, which is diallyl-4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone or 4-hydroxy-4'-isopropoxydiphenyl sulfone.