JPH04107183A - Transparent thermal recording material - Google Patents

Abstract

PURPOSE:To improve heat sensitivity, image density and transparency and to also make gradation properties sufficient, in a thermal recording material having a thermal layer formed by a applying a coating solution containing an electron donating colorless dye precursor and an electron acceptive compound on a transparent support to dry the coated support, by setting the particle size distribution of all of the materials dispersed in the thermal layer to a specific range. CONSTITUTION:For example, 3,3-bis(p-dimethylaminophenyl)-6- dimethylaminophthalide is roughly dispersed in a polyvinyl alcohol aqueous solution as an electron donating colorless dye precursor and further dispersed. Next, for example, bisphenol A is roughly dispersed in a polyvinyl alcohol aqueous solution as a developer to be further dispersed and both dispersions are blended. In this case, it is pref. to use the developer in an amount of 50-800% by wt. of the electron donating colorless dye precursor and the particle size distribution of all of the materials dispersed in a thermal layer is set to the range of D50<=1.0 and D90/D10>=5.0 wherein D10, D50 and D90 are % particle sizes calculated from cumulative volume distribution.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a heat-sensitive recording material with excellent transparency, and in particular has a heat-sensitive layer with high image density and excellent gradation and transparency.
This invention relates to a transparent thermosensitive recording material suitable for medical use.

(Prior art) Thermal recording methods (1) do not require development, (2) when the support is paper, the paper quality is similar to that of ordinary paper, (3) it is easy to handle, and (4) the color density is low. (5) The recording device is simple and inexpensive, and (6) There is no noise during recording, so it has rapidly become popular in the field of facsimiles and printers in recent years, and the use of thermal recording is also expanding. ing.

Against this background, in recent years, in order to adapt to multicolorization, overhead projectors (O
Transparent heat-sensitive recording materials that can be directly recorded with a thermal head have been developed for use in JP-A-63-45084 and JP-A-63-26.
No. 5682).

(Problems to be Solved by the Invention) Furthermore, there has recently been a desire to develop a transparent thermosensitive recording material that can be directly recorded with a thermal head for recording medical digital images such as ultrasound, CT, and X-rays. It is desired that heat-sensitive recording materials used in such applications have high density and gradation properties equivalent to those of silver halide films, but the above-mentioned transparent heat-sensitive recording materials develop color rapidly and are not suitable for recording with gradation. Not only was it unsuitable, but the image density was also insufficient.

Therefore, an object of the present invention is to provide a medical transparent thermosensitive recording material that has good transparency, high density, excellent gradation, and is suitable for recording with a thermal head.

(Means for Solving the Problems) The above-mentioned object of the present invention is to provide a thermal layer formed by coating and drying a coating solution containing an electron-donating colorless dye precursor and an electron-accepting compound on a transparent support. This was achieved by a transparent heat-sensitive recording material characterized in that the particle size distribution of all the materials dispersed in the heat-sensitive layer is in the following range; D90≦1° O D90/D10 ≧5.0 In the above formula, Dl. , DSo, and D90 are the % particle diameters determined from the cumulative volume distribution, and D90 is the maximum particle diameter (μm) when the cumulative volume is 10%, and D90 is the maximum particle diameter when the cumulative volume is 50%. The particle size (μm) and D90 are the maximum particle size (μm) when the cumulative volume is 90%.

The above D90 represents the median diameter, and D90 is 1.0 μm
If it is larger, sufficient transparency cannot be obtained, so it is particularly preferable that Dl6 is 0.7 μm or less.

D90/D+. represents how regular the particle size distribution is. In this case, the larger the value of D90/D90, the broader the particle size distribution, and the particle size distribution of the material dispersed in the heat-sensitive layer is The wider it is, the softer the F# key characteristic becomes. This is because particles much smaller than the median diameter develop color with low energy, whereas particles larger than the median diameter do not develop color unless energy is high.

Next, a typical method for producing a heat-sensitive color forming layer according to the present invention will be described, but the present invention is not limited thereto.

The electron-donating dye precursor, the electron-accepting compound (hereinafter referred to as a developer), and the sensitizer added as necessary are:
Generally, particles of several microns or less, preferably 1.0 microns or less, are dispersed in an aqueous solution of a water-soluble polymer binder such as polyvinyl alcohol using a ball mill, sand mill, or the like.

The sensitizer may be added to either the electron-donating dye precursor and the developer, or to both. After that, it may be mixed and dispersed.

Electron-donating colorless dye precursors that can be used in the present invention include triphenylmethane phthalide compounds, fluoran compounds, phenothiazine compounds, indolyl phthalide compounds, leucoauramine compounds, and rhodamine lactam compounds. , triphenylmethane compounds, triazene compounds, spiropyran compounds, and fluorene compounds.

Specific examples of phthalides are given in U.S. Reissue Patent Specification 23.02.
4, U.S. Patent No. 3,491,111, U.S. Patent No. 3
, No. 491,112, No. 3,491.116, and No. 3,509,174.

Specific examples of fluorans are given in U.S. Pat. No. 3,624.
No. 107, No. 3,627,787, No. 3,641
, No. 011, No. 3,462,828, No. 3,68
No. 1,390, No. 3.920.510 and No. 3.
No. 959,571.

Specific examples of spiropyrans are given in U.S. Patent Specification No. 3.971.
．． No. 808, pyridine and pyrazine compounds are described in U.S. Patent Nos. 3,775,424 and 3,853.
, No. 869 and No. 4,246.318, and specific examples of fluorene compounds are described in Japanese Patent Application No. 61-240989.

In the present invention, among these electron-donating dye precursors, black-forming 2-arylamino-3H-halogenoalkyl or alkoxy-6-substituted aminofluorane is particularly effective.

Specific examples include 2-anilino-3-methyl-6
-diethylaminofluorane, 2-anilino-3-methyl-6-N-cyclohexyl-N-methylaminofluorane, 2-p-chloroanilino-3-methyl-6-sibutylaminofluorane, 2-anilino- 3-methyl-6
-thioctylaminofluorane, 2-anilino-3-chloro-6-diethylaminofluorane, 2-anilino3
-Methyl-6-dibutylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-Nisoamylaminofluorane, 2-anilino-3-methyl-6-N-
Ethyl-N-dodecylaminofluorane, 2-anilino-3-methoxy-6-sibutylaminofluorane, 2-
0-chloroanilino-6-sibutylaminofluorane,
2-pchloroanilino-3-ethyl-6-N-ethyl-
N-isoamylaminofluorane, 2-0-chloroanilino-6-p-butylanilinofluorane, 2-anilino-3-pentadecyl-6-diethylaminofluorane, 2-anilino-3-ethyl-6-sibutylamino Fluoran, 2-anilino-3-methyl-6-sibutylaminofluoran, 2-o-)cyidino-3-methyl-6-
Diitubropylaminofluorane, 2-anilino-3-
Methyl-6-N-isobutyl-N-ethylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N
-tetrahydrofurfurylaminofluorane and 2-anilino-3-chloro-6-N-ethyl-N-isoamylaminofluorane. Two or more of these can also be used in combination.

The coating amount of these electron-donating dye precursors was 0°5 g/
m" or more, preferably 0.8 g/m" or more.

The color developer used in the present invention includes phenol derivatives, metal salts of aromatic carboxylic acids, acid clay, bentonite, novolac resins, metal-treated novolac resins, metal complexes, and the like.

Specific examples of these are given in Japanese Patent Publications No. 40-9309 and No. 45-1.
No. 4039, JP-A-52-140483, JP-A No. 48-5
No. 1510, No. 57-210886, No. 58-870
No. 89, No. 59-11286, No. 60-176795
No. 61-95988, etc.

To give some examples of these, phenolic compounds include 2,2'-bis(4-hydroxyphenyl)propane, 4-phenylphenol, and 1.1-bis(3-chloro-4-hydroxyphenyl)cyclohexane. , 1.1
-bis(4-hydroxyphenyl)cyclohexane, l
,■-bis(3-chloro-4-hydroxyphenyl)-
2-Ethylbutane, 4.4"-5ec-isooctylidene diphenol, 4.4'-5ec-butylidene diphenol, 4-P-methylphenylphenol, 4,4
゛-Methylcyclohexylidenephenol, 4.4'
-Isopentylidenephenol, bis(3-aryl-
4-hydroxyphenyl) sulfone, 4-hydroxyphenyl-3', 4'' dimethylphenyl sulfone, 4-(
4-isopropoxyphenylsulfonyl)phenol,
Examples include bis[2-(4-hydroxyphenylthio)ethoxycomethane, benzyl P-hydroxybenzoate, and the like.

Examples of salicylic acid derivatives include 4-pentadecylsalicylic acid, 3,5-di(α-methylbenzyl)salicylic acid, 3,
5-di(ter-octyl)salicylic acid, 5-α-
(p-α-methylbenzylphenyl)ethylsalicylic acid, 3-α-methylbenzyl-5-ter-octylsalicylic acid, 5-tetradecylsalicylic acid, 4-hexyloxysalicylic acid, 4-cyclohexyloxysalicylic acid, 4-decyl Among these, bisphenols include oxysalicylic acid, 4-dodecyloxysalicylic acid, 4-pentadecyloxysalicylic acid, 4-octadecyloxysalicylic acid, and their zinc, aluminum, calcium, and copper salts. preferable.

These color developers are electron-donating colorless dye precursors with 50 to 8
It is preferable to use 00% by weight, particularly preferably,
It is 100 to 500% by weight. If it is less than 50% by weight, color development will not be sufficient, and if it is added in an amount of 800% by weight or more, no further effect can be expected, which is not preferable.

In addition, in the present invention, as a sensitizer, for example, JP-A-58-57989 and JP-A-5B-87094 may be used as a sensitizer.
Compounds such as aromatic ethers, esters, aliphatic amides, or ureides disclosed in the above-mentioned publications can also be used in combination in the heat-sensitive coloring layer.

Specific examples of preferred sensitizers include benzyl P-benzyloxybenzoate, β-naphthyl-benzyl ether,
4-ethoxyphenyl-4'chlorobenzyl ether,
Stearic acid amide, stearyl urea, p-benzylbiphenyl, di(2-methylphenoxy)ethane, di(2
-methoxyphenoxy)ethane, β-naphthol-(p
-methylbenzyl) ether, α-naphthylbenzyl ether, 1,4-butanediol-p-methylphenyl ether, 1,4-butanediol-p-isopropylphenyl ether, 1,4-butanediol-p-te
rt-octylphenyl ether, 1-phenoxy-2
-(4-ethylphenoxy)ethane, 1-phenoxy-
2-(4-chlorophenoxy)ethane, 1,4-butanediol phenyl ether, diethylene glycol-bis(4-methoxyphenyl)ether, 1゜2-bis-
(4-methoxyphenoxy)bronoman, 1,2-bis-(4-ethoxyphenoxy)propane, 1-(4-methoxyphenoxy)-2-(4-ethoxyphenoxy)
Propane, 1-(4-ethoxyphenoxy)-2-(4
-methoxyphenoxy)propane, 1,2-bis-(2
-methoxyphenoxy)propane, 1-(4-methoxyphenoxy)-2-(2-methoxyphenoxy)propane, 1-(4-methoxyphenoxy)-2-phenoxypropane, 1-(4-methoxyphenoxy)-2- (4
-Methylthiophenoxy)propane, 1-(4-methoxyphenoxy)-2-(4-chlorophenoxy)propane, 1-(4-methoxyphenoxy)-2-(4-fluorophenoxy)propane, 1,2-bis- (3-methoxyphenoxy)phenoxypropane, 4-chlorobenzyl-4'-methoxyphenyl ether, 4-methoxybenzyl-4'-chlorophenyl ether, 4-chlorobenzyl-4'-ethoxyphenyl ether, 4-ethoxybenzyl- 4'-chlorophenyl ether, 4-propoxybenzyl-4'-chlorophenyl ether, 4-
Chlorobenzyl-2'-propoxyphenyl ether,
Examples include 4-butoxybenzyl-4'-chlorophenyl ether.

The sensitizers may be used alone or in combination, but
In order to obtain sufficient thermal responsiveness, it is preferably used in an amount of 10 to 200% by weight, particularly preferably 20 to 150% by weight, based on the electron-accepting compound.

These dispersions are mixed with each other, and if necessary, a binder, a surfactant, a wax, a metal soap, a pigment, an antioxidant, an ultraviolet absorber, etc. are added to form a heat-sensitive coating solution.1.The resulting heat-sensitive coating solution After coating on a transparent support such as a plastic film and drying, smoothness is imparted by calendering to obtain the desired heat-sensitive recording material.

The heat-sensitive recording material of the present invention includes Japanese Patent Application Laid-Open No. 60-255478
A protective layer as described in No. 1, etc. may be provided.

The binder used in the present invention is preferably a compound that dissolves at least 5% by weight in water at 25°C. (including polyvinyl alcohol), methylcellulose, carboxymethylcellulose, starch [(including modified starch), gelatin, gum arabic, casein, styrene]
Examples include hydrolyzed maleic anhydride copolymer, polyacrylamide, and saponified vinyl acetate-polyacrylic acid copolymer. These binders are used not only for dispersion but also for
Used to improve coating strength. For the purpose of improving coating strength, synthetic polymer latexes such as styrene-butadiene copolymer, vinyl acetate copolymer, acrylonitrile-butadiene copolymer, methyl acrylate-butadiene copolymer, and polyvinylidene chloride are used. It is also possible to use a binder of the same type. Also, depending on the type of binder used, a crosslinking agent suitable for the binder may be added, and the amount of these binders used must be 20% by weight or more of the total solid content of the coated and dried heat-sensitive layer. is preferred.

As the pigment, calcium carbonate, barium sulfate, lithopone, waxite, kaolin, silica, amorphous silica, etc. are used.

Examples of the wax include paraffin wax, polyethylene wax, carnauba wax, microcrystalline wax, camphoria wax, montan wax, fatty acid amide wax, and the like.

As the metal soap, higher fatty acid metal salts are used, such as zinc stearate, calcium stearate, aluminum stearate, and the like.

Furthermore, surfactants, antistatic agents, ultraviolet absorbers, antioxidants, antifoaming agents, conductive agents, fluorescent dyes, coloring dyes, etc. may be added as necessary.

In addition, in order to prevent decoloring of the image-printed area and to harden the generated image, a decoloring inhibitor may be added to the heat-sensitive coloring layer. Dophenol compounds are effective. The amount of the phenolic compound to be used is preferably 1 to 200% by weight, more preferably 5 to 50% by weight based on the color developer.

The coated heat-sensitive recording material is dried and subjected to a process such as a calender before being used.

Further, a protective layer may be provided on the heat-sensitive recording layer if necessary, and any material known as a protective layer for heat-sensitive recording materials can be used as the protective layer. Further, an intermediate layer made of a water-soluble binder may be provided between the heat-sensitive layer and the protective layer.

As the transparent support on which the heat-sensitive layer is coated, a film of polyester such as polyethylene terephthalate or polybutylene terephthalate, a cellulose triacetate film, a polypropylene film, a film of polyolefin such as polyethylene, etc. are used.

In the present invention, an undercoat layer can be provided between the transparent support and the heat-sensitive layer in order to enhance adhesion between the two layers. Gelatin, synthetic polymer latex, nitrocellulose, etc. are used as the material for the undercoat layer. The coating amount of the undercoat layer is 0.
It is preferably in the range of 1 g/m" to 2.0 g/m", particularly 0.0 g/m". A range of 2 g/m" to 1.0 g/m" is preferred.

If it is less than 0.1 g/m", the adhesion between the support and the heat-sensitive layer will not be sufficient (and even if it is increased to 2.0 g/m or more, the adhesion between the support and the heat-sensitive layer will reach saturation. Therefore, it is disadvantageous in terms of cost.

(Effects of the Invention) In the heat-sensitive layer of the heat-sensitive recording material of the present invention, a small particle size material with high sensitivity and a large particle size material with low sensitivity are appropriately dispersed. It has good transparency and sufficient upper gradation, and is particularly suitable for medical use.

(Example) The present invention will be explained in more detail with reference to Examples below.
The present invention is not limited to these.

Example 1 [Preparation of heat-sensitive recording material] 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide 40 as an electron-donating dye precursor
g to 100 g of 5% polyvinyl alcohol (Kuraray P
VA105) prepared 5 pieces roughly dispersed in an aqueous solution, and a sand grinder (manufactured by Shinmaru Enterprises)
Dynomill KDP) was dispersed 2 times, 4 times, 6 times, 8 times, and 10 times, respectively, and then all of them were blended. When the particle size of the dispersion of this liquid was measured using a particle size distribution measuring device (■ LA-500 manufactured by Horiba), Dss was 0.82.
μm, 090/DI6 was 9.6. 6 Next, as a color developer, 5 pieces of roughly dispersed 40 g of bisphenol A in 100 g of polyvinyl alcohol (Kuraray PVAl05) aqueous solution were prepared and dispersed in the same manner as the electron-donating dye precursor. Then blended.

When the particle size of the dispersion of this liquid was measured, I)sa was 7
．． 0 gm, and Dqo/Die was 8.3. Among the dispersions prepared as above, 10 g of electron-donating dye precursor dispersion, 20 g of color developer dispersion, and 10% polyvinyl alcohol (Kuraray PVAl05) aqueous solution. 20 g was added to obtain a heat-sensitive coating liquid.

This heat-sensitive coating liquid was coated on one side of a 75 μ thick transparent polyethylene terephthalate (PET) support with a solid content of 6.0 g.
/ryl and dried to form a heat-sensitive layer.

[Preparation of protective layer]

A protective layer (2.5 g/n) having the following solid content composition was further formed on the above heat-sensitive layer to obtain a heat-sensitive recording material.

Polyvinyl alcohol (Kuraray PVA124) 2 parts by weight Kaobrite (Thiele) 4 parts by weight Boric acid 0. 1 part by weight Zn stearate Rug 0.2 parts by weight Sodium lauryl sulfate 0.05 parts by weight Example 2゜ On the same heat-sensitive layer as in Example 1, an intermediate layer of only polyvinyl alcohol (Kuraray PVA124) was added at 2゜0g/ rri
A heat-sensitive recording material was obtained in exactly the same manner as in Example 1 except that the material was formed.

Example 3 [Preparation of heat-sensitive recording material] 2-anilino-3-methyl-6-N-ethyl-5ec-butylaminofluorane 40 as an electron-donating dye precursor
g to 100 g of 5% polyvinyl alcohol (Kuraray P
VA105) Five pieces roughly dispersed in an aqueous solution were prepared and dispersed in the same manner as in Example 1.

The particle size of the dispersion of this liquid was measured [)i.

was 7.4 gm, and D*a/D+o was 10.5.

Next, add 20 g of bisphenol A as a color developer and 20 g of β-naphthylbenzyl ether as a sensitizer to 100 g of 5
% polyvinyl alcohol (Kuraray PVA105) aqueous solution were prepared, and dispersed in the same manner as in Example 1.Among the dispersions prepared as above, the electron-donating dye precursor dispersion 10g, developer/sensitizer dispersion 4Og, 10% polyvinyl alcohol (Kuraray PV
A105) 38 g of an aqueous solution was added to obtain a heat-sensitive coating liquid.

This heat-sensitive coating liquid was prepared using the same support as in Example 1, with a solid content of 7.0.
g/rd and dried to form a heat-sensitive layer.

On top of the above heat-sensitive layer, 2.5 g /
A heat-sensitive recording material was obtained by forming a protective layer of rrr.

Comparative Example 1 The procedure of Example 1 was repeated except that the crude dispersions of the electron-donating dye precursor and the polyvinyl alcohol aqueous solution of the color developer used in Example 1 were each dispersed 10 times with a sand grinder.
A heat-sensitive layer and a protective layer were formed in exactly the same manner as above to obtain a heat-sensitive recording material. When we measured the particle size of each,
The DS of the electron-donating dye precursor is 0.53μ, D90/
D90 is 3°0, D90 of color developer is 0.47μ, D90
/D90 was 2°7.

Comparative Example 2゜Electron-donating dye precursor and color developer used in Example 3/
A heat-sensitive recording material was obtained by forming a heat-sensitive layer and a protective layer in exactly the same manner as in Example 3, except that each crude dispersion of an aqueous solution of polyvinyl alcohol as a sensitizer was dispersed 10 times using a sand grinder.

When the respective particle diameters were measured, the electron-donating dye precursor had a D90 of 0.61, D90/DI0 was 2.3, and the developer/sensitizer had a D90 of 0.73, D90/D+. was 0.55.

Each sample prepared in this way was transferred to a thermal imager.
Table 1 shows the results of printing with FTI210 (manufactured by Fuji Photo Film Co., Ltd.) and measuring the transmission density with a transmission densitometer (manufactured by Macbeth) to examine the relationship between the current application time during printing and the image density. Ta.

The results in Table 1 demonstrate that the heat-sensitive recording material of the present invention provides images with excellent gradation.

Claims (1)

[Scope of Claims] A heat-sensitive recording material having a heat-sensitive layer formed by coating and drying a coating solution containing an electron-donating colorless dye precursor and an electron-accepting compound on a transparent support, wherein the heat-sensitive layer contains: A transparent heat-sensitive recording material characterized in that the particle size distribution of all dispersed materials is in the following range;
are the % particle diameters determined from the cumulative volume distribution, D_1_0 is the maximum particle diameter (μm) when the cumulative volume is 10%, and D_5_0 is the maximum particle diameter when the cumulative volume is 50%. (μm) and D_9_0 are the maximum particle diameters (μm) when the cumulative volume is 90%.