JPS6023093A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide the titled material having high sensitivity, free from discoloration or flushing of images and having high ground brightness, wherein a thermal recording layer comprising a leuco dye and a color developer consisting of a specified bisphenol derivative as main constituents is provided on a base through a specified undercoat layer. CONSTITUTION:In a thermal recording material wherein a thermal color forming layer comprising a leuco dye and a color developer as main constituents is provided on a base, at least one bisphenol derivative of formula I , wherein n is 1 or 2, and at least one bisphenol derivative of formula II, wherein X is halogen, Y is -SO2- or -C(CH3)2- and m is 1 or 2, provided that the groups X in the left and right benzene rings are located at positions symmetrical with respect to the group Y, are used as the color developer. In addition, an undercoat layer comprising a bisphenol derivative of formula III, wherein Z is -S-, -C(CH3)- or the like and each of R1-R4 is H or 1-4C alkyl, a filler and a binder is provided between the base and the thermal color forming layer to obtain the objective material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a heat-sensitive recording material, and more particularly to a leuco dye that is colorless or slightly light-colored at room temperature.

The present invention relates to an improvement in a heat-sensitive recording material provided on a support with a heat-sensitive coloring layer containing as a main component a color developer which reacts with the leuco dye and develops color when heated.

[Prior art]

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) Simply force.

(2) It records a colored image simply by heating, eliminating the need for a complicated development process; (2) It can be manufactured using relatively simple and compact equipment; and the resulting recording material is easy to handle and maintenance costs are low. To be.

(3) Paper is often used as a support, and in this case, not only is the cost of the support low, but also the feel of the resulting recording material is similar to that of plain paper. It is widely used in the field of printers such as computers and calculators, recorders for medical measurement, low and high speed facsimiles, automatic ticket vending machines, thermal copying, etc.

2. Thermosensitive recording materials are usually manufactured by coating and drying a thermosensitive coloring layer solution containing a coloring component that can cause a coloring reaction when heated, on a support such as 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, heat-sensitive recording materials disclosed in Japanese Patent Publication No. 43-4160 or Japanese Patent Publication No. 45-14039; Responsiveness was low, and sufficient color density could not be obtained during high-speed recording. As a method for improving such drawbacks, for example, JP-A No. 49-38424 discloses the use of nitrogen-containing compounds such as acetamide, stearamide, m-21-roaniline, and dinitrile phthalate; Acetoacetanilide is used in JP-A-53-11036.
In the publication, N,N-diphenylamine derivatives, benzamide derivatives, and carbazole derivatives are disclosed in JP-A-53-39.
No. 139 discloses alkylated biphenyls and biphenylalkanes, and JP-A-56-144193 discloses P-
A method of increasing speed and sensitivity by incorporating oxybenzoic acid ester derivatives has been disclosed, and among them, using p-oxybenzoic acid ester derivatives as a color developer is known to be the most effective method. It was getting worse.

However, these various color developers still have drawbacks such as fading of the recorded image and whitening of the image area (white powder is generated on the surface). In order to improve these problems, the present inventors have developed the following general formula (
We have proposed a heat-sensitive recording material characterized by using at least one of the bisphenol derivatives represented by 1) and (II) as a color developer (Japanese Patent Application No. 58-3949).
No. 8). However, although this product is excellent in preventing whitening of images, it has been found that further improvement is desired in terms of fading of recorded images.

(In the formula, n represents l or 2) (In the formula, X is halogen, ■ is -502, - or -C (C
H3) 2-1 tumor represents 1 or 2, and X of the left and right benzene rings is substituted in a symmetrical position with respect to Y) [Purpose] The present invention has unprecedented high sensitivity. Moreover, it is an object of the present invention to provide a heat-sensitive recording material which does not cause fading or whitening of recorded images and has a high background whiteness.

〔composition〕

According to the present invention, in a heat-sensitive recording material in which a heat-sensitive color forming layer containing a leuco dye and a color developer as main components is provided on a support, the color developer is represented by the following general formulas (1) and (II). At least one type of bisphenol derivative is used, and an undercoat layer consisting of a bisphenol derivative represented by the following general formula (m), a filler, and a binder is provided between the support and the heat-sensitive coloring layer. A heat-sensitive recording material is provided.

(In the formula, n represents 1 or 2) (In the formula, X is halogen, Y is -302- or -C(CI
13 h, m represents 1 or 2, and X of the left and right benzene rings is substituted at a symmetrical position with respect to Y.) (In the formula, Zl; L -5-, -C (CH )2-1-
6 - represents R1, R7, R3 and town) I or cL-c4. When the bisphenol derivative of general formula (m) used in the present invention is contained in the heat-sensitive coloring layer, fading of the recorded image can be prevented, but background fogging becomes significant. If the particle size of the leuco dye or color developer is increased and used in order to prevent background fogging, high sensitivity of the heat-sensitive recording material cannot be achieved. On the other hand, by configuring the recording material of the present invention as described above, prevention of fading and high sensitivity can be achieved at the same time.

Examples of the compound represented by the general formula (1) include .

Examples of the compound represented by the general formula (n) include the formula %formula% Examples include compounds shown in the following.

Further, examples of the compound represented by the general formula (m) include shiM GH and the like.

The compound represented by the general formula (1) used in the present invention has a melting point of 1-00-150°C and a high color developing ability. It has higher thermal responsiveness than conventional color developers such as butylidene diphenol, and also has excellent uniformity of colored images. The compound represented by general formula (II) has a much higher melting point than the color developing substance of formula (1-) above, but when the two are mixed together, they form a eutectic compound, and the color developing substance of formula (1) forms a eutectic compound. Recrystallization at .

It is thought that this prevents the phenomenon of fading and whitening. Additionally, in general, when two or more color-developing substances are used in combination, the water solubility increases, the eutectic temperature becomes too low, the fog of the heat-sensitive coating liquid becomes thicker, and the background fog during storage increases. However, since the color developing substance represented by the above formula (II) has low water solubility, such a problem does not occur.

In addition, the bisphenol derivative of formula (m) has a higher color developing ability than the bisphenol derivative of formula (II), so if it is contained in the heat-sensitive coloring layer, there are problems as described above.
By including it in the undercoat layer together with a binder, there is no fogging on the background, and the leuco dye and the compounds of general formulas (1), (II), <11) are eutectic only when heated, so that the recorded image does not fade. is expected to be further improved. Since the undercoat layer in the structure of the present invention has the function of smoothing the unevenness on the surface of the base paper, the unevenness on the surface of the upper heat-sensitive coloring layer can also be reduced, and as a result, the sensitivity is further increased. It will be done.

In the present invention, the color developer consisting of the above combination used in the thermosensitive coloring layer is generally 1 to 10 parts by weight, preferably 2.0 parts by weight, per 1 part by weight of the leuco dye. It is used in the range of ~6 overlapping parts. Further, the weight ratio of the color developer represented by the general formula ('1) and the color developer represented by the general formula (■) is preferably 1:1 to 10:1, preferably 2 :1 to 5:1 is preferable.

In the heat-sensitive recording material of the present invention, an undercoat layer consisting of a compound represented by the general formula (m), a filler, and a binder is provided between the support surface and the heat-sensitive coloring layer. As the agent, any inorganic or organic pigment used for membrane paper making or coating may be used, and specific examples include the following.

Calcium carbonate, kaolin, talc, zinc oxide, aluminum hydroxide, silica, magnesium silicate, polystyrene resin, urea-formaldehyde resin, etc.

Further, as the binder, generally known water-soluble polymers and aqueous emulsions are used, and specific examples include those shown below.

Polyvinyl alcohol, methylcellulose, hydroxyethylcellulose, starch, starch derivatives, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyamide, SBR latex, polystyrene-acrylate emulsion, polyvinyl acetate emulsion, etc.

The weight ratio of filler and binder in this undercoat layer is arbitrarily determined depending on the selected components, but is preferably 1.
:9 to 9:1, and the general formula (I
The bisphenol derivative I) is preferably used in an amount of 0.5 to 4 times the weight of the leuco dye in the heat-sensitive coloring layer. Furthermore, the coating amount of the undercoat layer is 1 g.
/rd or more is effective, but preferably 3g/n
f or more is good.

The leuco dyes used in the present invention can be applied singly or in combination of two or more types, but such leuco dyes include:
Any dye that has been applied to this type of heat-sensitive material may be used. For example, leuco compounds of dyes such as triphenylmethane, fluoran, phenothiazine, auramine, and spiropyran dyes are preferably used. Specific examples of such leuco dyes include those shown below.

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-dibutylaminophenyl, 3.3-bis(p-dimethylaminophenyl)-6-chlorophthalide, 3.3-bis(P-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6- Chlorfluorane, 3-dimethylamino-5,7-dimethylfluorane, 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-
chloranilino)xantylbenzoic acid lactam), 3-
Diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran.

3-diethylamino-7-(o-chloroanilino)fluoran, 3-dibutylamino-7-(o-chloroanilino)fluoran, 3-N-methyl-N-amylamino-6-methyl-7-
7-anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane.

3-diethylamino-6-methyl-7-anilinofluorane, 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'- 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)fluorane, 3-pyrrolidino-7-(di-p-chlorophenylmethylaminofluorane, 3-diethylamino-5-chloro-7 -(α-phenylethylamino)fluoran, 3-(N-ethyl-p-toluidino)-7-(α-)engineered methylethylamino)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-benzyl-N-cyclohexylamino)-5
．． 6-penzo 7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino 4
', 5'-benzofluorane, etc.

In the present invention, in order to bind and support the leuco dye and color developer on the support, various commonly used binders can be used as appropriate, such as polyvinyl alcohol, starch and its derivatives, methoxycellulose, hydroxyl, etc. Ethyl cellulose.

Carboxymethylcellulose, methylcellulose.

Cellulose derivatives such as ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide/
Acrylic acid ester copolymer, acrylic acid amide l acrylic acid ester l methacrylic acid ternary copolymer, styrene/maleic anhydride copolymer alkali salt, isobutylene/
In addition to water-soluble polymers such as maleic anhydride copolymer alkaline salts, polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, styrene/butadiene copolymers, polyacrylic acid, polyacrylic acid esters, and chloride Vinyl/vinyl acetate copolymer, polybutyl methacrylate, ethylene/vinyl acetate copolymer,
By using a latex such as a styrene/butadiene/acrylic copolymer, in addition to the leuco dye and color developer, if necessary, additional auxiliary materials commonly used in this type of heat-sensitive recording material can be used. Additive component 1 For example, fillers, surfactants, thermofusible substances (or lubricants), etc. can be used in combination. 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. Examples of thermofusible substances include higher fatty acids or their esters, amides, or metal salts. In addition, various waxes, feed compounds of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols,
dialkyl 3,4-epoxy-hexahydrophthalate,
50-2 of higher ketones, other thermofusible organic compounds, etc.
Examples include those having a melting point of about 00°C.

Conventional methods can be used to produce the heat-sensitive recording material of the present invention. For example, the above-mentioned components are separated into at least the leuco dye and the color developer, and then dispersed with a dispersion machine such as a ball mill, attritor, or sand mill to obtain a dispersed particle size of 1 to 1.
After pulverizing and dispersing the powder to a size of 3μ, the mixture is blended into a certain formulation to prepare a heat-sensitive coloring layer solution. On the other hand, apart from this, the bisphenol derivative of the general formula (m) may be added to an aqueous medium, for example,
After adding it to the aqueous solution of the water-soluble polymer and pulverizing and dispersing it using a dispersion machine, filler and binder aqueous solution are added and mixed and stirred to prepare an undercoat layer solution.

Next, the undercoat layer liquid is coated and dried on a support such as paper, film, synthetic paper, etc., and the heat-sensitive coloring layer liquid is coated and dried on top of the undercoat layer liquid, followed by calendering. One heat-sensitive recording material was obtained.

〔effect〕

The heat-sensitive recording material of the present invention has the general formula (1).

Because the bisphenol derivatives of (■) are combined and contained in the heat-sensitive coloring layer, and the bisphenol derivative of the general formula (I [I) is contained in the undercoat layer together with a filler and a binder, the problem of background fogging occurs. Moreover, there is no fading or whitening of the recorded image, and in addition, the undercoat layer smoothes unevenness on the surface of the support, and the penetration of the thermosensitive coloring layer liquid into the support is reduced, so thermal sensitivity is extremely high. It is excellent.

〔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.

[Examples 1 to 4] Next, the mixture of the components was dispersed using a sand glider for 2 hours (liquid A3-(E) was prepared).

(A) Solution 4.4'-thiobis(3-methyl-6-t-butylphenol) 75 parts Calcium carbonate 225 parts 10% polyvinyl alcohol aqueous solution 300 Water 40
0/1 [B] Solution 4,4'-thiobis(3-methyl-
Same composition except that 6-1,-butylphenol) was changed to 4,4'-cyclohexylidene diphenol [C,]
Liquid 3-(N-methyl-N-cyclohexyl)amino-6-
Methylanilinofluorane 200 parts 10% polyvinyl alcohol aqueous solution 300 Water 50011 Solution (D) 2.2', 6.6'-tetrabromo-4,4'-sulfonyldiphenol 25 parts (2,2', 6. 6'-tetrabromo-4,4'
-dihydroxydiphenylsulfone) Calcium carbonate 125n 10% polyvinyl alcohol aqueous solution 300 parts Water 45
0# [E] Instead of 2,2',6.6'-tetrabromo-4゜4'-sulfonyldiphenol in solution (D), 2
．． 2'.

6. Same composition method except that 6'-tetrabromo-4,4'-isopropylidenediphenol was used, (C]: (D)=(C): (E)=l:
(C) solution and CD) solution, and (C
] solution and (E'l solution) were mixed and stirred to prepare heat-sensitive coloring layer coating solutions [D'] and [E'], respectively.

These undercoat layer coating liquid (A) or (BE and heat-sensitive color forming layer coating liquid [D'] or [E'] were mixed with a basis weight of 52 g/m'.
"Undercoat layer is 5g/m dry weight on high quality paper"
After coating and drying according to the contents of Table 1 so that the heat-sensitive coloring layer becomes 5 to 6 g/m'', the Bekk smoothness is 500 to 200.
Four types of heat-sensitive recording materials of the present invention were prepared by calendering so that the temperature was 0 seconds.

Table-1 Comparative Example 1 In Example 1, undercoat layer coating liquid [A] to 4
Comparative Example 1 was carried out in the same manner except that ,4'-thiobis(3-methyl-6-butylphenol) was removed.
A thermosensitive recording material was created.

Comparative Example 2 In Example 2, no undercoat layer was provided, and 2.2', 6.6' - in the heat-sensitive coloring layer coating liquid [E']
4,4'-thiobis(3-methyl-6
A heat-sensitive recording material of Comparative Example 2 was prepared in the same manner except that 1-butylphenol) was used.

Comparative Example 3 In Example 2, undercoat layer coating liquid [A] to 4
, 4'-thiobis(3-methyl-6-t-butylphenol) was used, and a heat-sensitive recording material of Comparative Example 3 was prepared in the same manner except that benzyl hydroxybenzoate was used.

The above heat-sensitive recording materials were tested for fading resistance, whitening, and background density of dynamic color sensitivity images. The results are shown in Table-2. The test method was performed as follows.

(1) Dynamic color development sensitivity: head power 0.4 using a thermal printing experimental device with a thin film head manufactured by Matsushita Electronic Components Co., Ltd.
The pulse width was set to 0.8, 1.0, 1.2, 1.4, 1.6, under the conditions of 5 W/dot, 1 line recording time of 20 IIls/Q, and scanning line density of 8 x 3.85 dots/mm. and 1,
Printed at 8m5ec, and the print density was Macbeth Densitometer R.
Measured with D-514 (T filter-1it-106).

(2) Image fading property...For the samples whose dynamic color development sensitivity was measured in (1), those with print density of 1.0 to 1.2 (this is referred to as DO), 40°C, 90% RH 24 below
The concentration after standing for hr was measured (this was designated as D), and the concentration was determined to decrease according to the following formula.

(3) Image whitening: The sample obtained in (1) was left at room temperature for 15 days, and visually evaluated as below.

0 Almost no white powder generation △ White powder generation, but no practical problem x Too much white powder generation, unusable (4) Skin density: The skin density after calendering was measured with a Macbeth densitometer RD-514.

Table 2 From the results shown in Table 2, it can be seen that the thermal recording material of the present invention has improved dynamic sensitivity compared to the material without an undercoat layer (Comparative Example 2), and also contains benzyl P-hydroxybenzoate. There is less whitening than when the bisphenol derivative of formula (III) is used (Comparative Example 3), and there is extremely less fogging on the background and less fading than when the bisphenol derivative of formula (III) is added to the heat-sensitive coloring layer (Comparative Example 1). I understand that.

Claims (1)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive color forming layer containing a leuco dye and a color developer as main components is provided on a support, the color developer is represented by the following general formulas ('I) and (■). At least one type of bisphenol derivative is used, and the following general formula (
1. A heat-sensitive recording material comprising an undercoat layer comprising a bisphenol derivative represented by m), a filler, and a binder. (In the formula, n represents 1 or 2) Xll XJ (In the formula, X is halogen, Y is -5O7- or -c (C
I+3) 2-1 Kamoh represents l or 2, and X of the left and right benzene rings is substituted at a symmetrical position with respect to Y) (In the formula, 2 is -5-1-C(CH -6)2-5-0]
-, R□, R7, R3 and R4 are H or CL-
(represents a C4 alkyl group)