JPH02307784A - Thermally sensitive recording material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a thermal recording paper, and more specifically to a high-sensitivity thermal recording paper that has good thermal responsiveness and a low amount of lees (=J deposit) on the thermal head. It's about paper.

[Prior Art] Thermosensitive recording paper is generally made up of a support such as paper, plastic film, synthetic paper, etc., with a single or multilayer thermosensitive coloring layer mainly composed of a binder or a thermochromic substance. be.

Thermosensitive recording paper is widely used as a variety of information recording paper because it can produce colored images simply by heating it, and the recording device can be made relatively simple and compact. .

Particularly in recent years, improvements have been made in the equipment of thermal facsimile machines and thermal printers that use such thermal recording bodies, and high-speed recording, which was difficult in the past, has become possible.

As the speed of such equipment and hardware increases, the thermal recording paper used is required to have improved recording sensitivity, and many proposals have been made in this regard.

Hitherto, it has been thought that it is effective to smooth the support and provide it with heat insulating properties using an undercoat layer in order to improve the recording sensitivity of thermal recording paper.

As a method, hydrophobic polymer particles having lower thermal conductivity than inorganic pigments are contained in the undercoat layer (Japanese Patent Laid-Open No. 59-2
04595, JP-A No. 60-2397), hollow fine particles are included in the undercoat layer to further add air insulation properties (JP-A-59-171885, JP-A-59-225987). (Public Notice) is proposed. However, although these methods are effective in improving recording sensitivity, they are insufficient techniques in terms of lees adhesion to the thermal head, which is as important as recording sensitivity in practice.

Therefore, it has been proposed to provide a layer of highly oil-absorbing silicon oxide in combination with hydrophobic polymer particles as an undercoat layer to prevent dregs from adhering to the thermal head (Japanese Patent Application Laid-Open No. 81-818).
9883). However, when such highly oil-absorbing silicon oxide is added, a large amount of the color-forming molten component of the heat-sensitive color-forming layer is absorbed into the undercoat layer, resulting in image distortion.

[Problems to be Solved by the Invention] Therefore, the present invention has high recording sensitivity and also has a high recording sensitivity.
To provide a heat-sensitive recording paper which can effectively prevent J-color and also prevent image blurring when colored with high energy.

[Means for Solving the Problems] The present invention provides a heat-sensitive recording sheet in which a heat-sensitive recording layer containing an electron-donating colorless dye and an electron-accepting compound is provided on a support. The present invention relates to a heat-sensitive recording material characterized in that it is provided with an undercoat layer containing polystyrene and a pigment with an oil absorption of less than 100 m1/100 g.

As a result of research, the present inventors have found that by forming an undercoat layer under the heat-sensitive coloring layer and using polystyrene as a filler in the undercoat layer, higher recording sensitivity can be obtained than when inorganic pigments are used as the filler. I learned that. However, when polystyrene is used alone, it lacks lees absorbency and cannot be said to be a desirable heat-sensitive recording material. Therefore, by mixing an inorganic pigment in order to improve the lees absorption property, a desirable heat-sensitive recording material having high recording sensitivity and high lees absorption property could be obtained.

Polystyrene has high thermal conductivity and can provide high recording sensitivity. It is preferable to use polystyrene in the form of fine particles with an average particle diameter of 5 μm or less, preferably 0.5 to 2 μm. If the particle size exceeds 5 μm, a highly smooth undercoat layer cannot be formed. Note that it must be taken into consideration that particles with a particle size smaller than 0.5 μm tend to further reduce the lees absorbency.

The pigment that should be mixed with polystyrene in the undercoat layer must have an oil absorption of less than 100 m1/'long (JIS K5
101). Examples of such pigments include:
Examples include fired clay, clay, talc, calcium carbonate, magnesium carbonate, and the like. In this case, when the oil absorption amount is 100u+1'/100g or more, the lees absorption property improves, but when printing with high energy, the printing density decreases and it is not possible to pour properly.

Polystyrene and oil absorptionffl' 100ml/400
The pigments weighing less than 1 gram are generally used in a mixture in a range of 1:4 to 4:1 (weight ratio). Oil absorption ft'L than 1:4
If the amount of pigment is increased below OOml'/100g, high recording sensitivity cannot be maintained, and if the amount of polystyrene is increased beyond 4:1, high lees absorbency cannot be maintained.

When forming an undercoat layer consisting of polystyrene and pigment with an oil absorption of less than 100 m1/100 g, an adhesive is used. The amount of adhesive used is 1 to 20 parts (weight ratio) to the total amount i00 parts of polystyrene and pigment.

As the adhesive used, generally known water-soluble polymer aqueous emulsions are used, and specific examples include those shown below.

Polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, starch, starch derivatives, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyamide, SBR latex, polystyrene-acrylic acid ester emulsion, polyvinyl acetate emulsion, etc.

Polystyrene as described here, oil absorption 1'OOm
A coating liquid is prepared by dispersing and mixing less than 1/100 g of pigment and an adhesive in an aqueous medium in any order, and this coating liquid is applied onto a support in an amount of 1 to 15 g/rrf as dry weight. Coat to form an undercoat layer. Coating can be performed using a common coating machine.

The support can be selected from suitable materials such as paper, plastic film, synthetic paper, and metal foil.

A thermosensitive coloring layer is formed on the undercoat layer thus provided.

The thermosensitive coloring layer may be formed by a conventional method. The following colorless or light-colored electron-donating dyes can be used.

Crystal violet lactone 3- (N-ethyl-
N-isopentylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-(0゜p-dimethylaniline) 3-(N-ethyl-p-)-luidino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-dibutylamino-6 -Methyl-7-anilinofluorane, 3-(N-cyclohexine-N-methylamino)-6
-Methyl-7-anilinofluoran, 3-diethylamino-7-(O-taloloanilino)fluoran, 3-diethylamino-7-(m-trifluoromethylanilino)fluoran, 3-diethylamino-6-methyl-chlorofluoran Orane, 3-diethylamino-6-methylfluorane, 3-cyclohexylamino-6-chlorofluorane, Representative examples of electron-accepting compounds (color developers) include the following compounds.

Bisphenol A1 benzyl p-hydroxybenzoate, loobyl di(4-hydroxyphenyl)acetate, bisphenol 51 4-hydroxy, 4'-isopropyloxydiphenyl sulfone, 1.1-di(4-hydroxyphenyl)cyclohexine, 1. In addition to 7-di(hydroxyphenylthio)-3,5-di-oxaheptane, other substances that can be normally included in the heat-sensitive coloring layer may be optionally included. For example, as a so-called sensitizer, a known thermofusible organic compound having a melting point of 50 to L50'C is generally used, and the following representative examples can be listed.

p-hydroxynaph I/technical acid phenyl ester, p-benzylbiphenyl, benzyl naphthyl ether, benzyl terephthalate, benzyl p-benzyloxybenzoate, diphenyl carbonate, ditrilyl carbonate, and organic or inorganic pigments such as oil-absorbing pigments, etc. There are no restrictions on the following, such as calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay,
In addition to inorganic fine powders such as talc, surface-treated nocolsium carbonate and silica, urea-formalin resin, styrene/
Methacrylic Acid Copolymerization 9. Organic fine powder such as polystyrene resin may be used as necessary.

These four types of waxes can be contained as necessary. Known waxes such as paraffin, amide wax, bisimide wax, and metal salts of higher fatty acids may be used.

In addition, adhesives include polyvinyl alcohol of various molecular weights, starch and its derivatives, methoxycellulose,
Cellulose derivatives such as carboxymethylcellulose, methylcellulose, and ethylcellulose, polyacrylic acid sorter, polyvinylpyrrolidone, acrylic amide/acrylic ester copolymer, acryl amide/acrylic ester/methacrylic acid ternary copolymer, styrene/maleic anhydride In addition to water-soluble polymers such as acid copolymer alkali salts, polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, and styrene/
Use latex such as butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer, polybutyl methacrylate, ethylene/vinyl acetate copolymer, styrene/butadiene/acrylic copolymer, etc. I can do it.

[Example] Next, the present invention will be explained using a specific example. Further, unless otherwise specified, parts and percentages in the examples indicate parts by weight and percentages by weight, respectively.

Example-1 Water 10
After dispersing 40 parts of a polystyrene particle dispersion (Asahi Kasei L 8801, solid content 48%) for 5 minutes with a homogenizer, 10% polyvinyl It was mixed with 50 parts of alcohol (GH17 manufactured by Nippon Gosei) to prepare an undercoat layer coating liquid. 50g/r of this undercoat layer coating liquid
The amount of coating on 'r'1' high quality paper is 7g/rr? It was coated and dried so that

On the other hand, as a coating liquid for a heat-sensitive coloring layer, the following is used:
Methyl-7-anirite fluorane 20 parts Polyvinyl alcohol 10% solution 10 parts Water
70 parts of this composition was ground to an average particle size of 2 μm using a sand grinder.

■Dispersion B Benzyl p-hydroxybenzoate 20 parts Polyvinyl alcohol 10% solution 10 parts Water

This composition was ground with a sand grinder to an average particle size of 2ρ.

■ Formation of thermosensitive coloring layer 75 parts of solution A, 125 parts of solution B, 30 parts of calcium carbonate, 1
A coating liquid was prepared by mixing and stirring 200 parts of a 0% polyvinyl alcohol aqueous solution, 17 parts of a 30 part rough-in dispersion, and 17 parts of a 30 part zinc stearate dispersion. The obtained coating liquid was applied onto the undercoat layer formed as described above so that the coating amount after drying was 4.5.
The coating was applied and dried to give a heat-sensitive recording paper of g/rrr.

Example-2 Water 1
00 parts light calcium carbonate (Callite SA manufactured by Shiroishi Chuuken oil absorption 60ml/100g) 2
After dispersing 40 parts of 0 parts polystyrene particle dispersion (Asahi Kasei L 8801, solid content 48%) for 5 minutes using a homogenizer, it was mixed with 50 parts of 10% polyvinyl alcohol (Nippon Gosei GH17) to form an undercoat layer coating solution. did. 50g/of this undercoat layer coating liquid
It was applied and dried on rrf' high-quality paper at a coating amount of 7 g/rrf.

A heat-sensitive coloring layer was provided on this undercoat layer in the same manner as in Example 1 to produce heat-sensitive recording paper.

Comparative example-1 Water 10
0 parts synthetic silica (Tokuyama Soda Solex CM oil absorption 1
After dispersing 40 parts of polystyrene particle dispersion (Asahi Kasei L 8801, solid content 48%) for 5 minutes using a homogenizer, an undercoat layer coating solution was prepared in the same manner as in Example-1, and the mixture was coated on the same support. An undercoat layer was provided by coating in the same manner as above. A thermosensitive coloring layer similar to that in Example 1 was provided on this undercoat layer.

Comparative example-2 Water
After dispersing 40 parts of 100-on Doancilex with a homogenizer for 5 minutes, an undercoat coating solution was prepared in the same manner as in Example 1, and coated on the same support in the same manner to form an undercoat layer.

A heat-sensitive coloring layer similar to that in Example 1 was provided on this undercoat layer to obtain heat-sensitive recording paper.

Comparative example-3 Water 1
After dispersing 82 parts of polystyrene particle dispersion (Asahi Kasei L 8801, solid content 48%) for 5 minutes using a homogenizer, an undercoating solution was prepared in the same manner as in Example-1, and coated on the same support in the same manner. Then, an undercoat layer was provided. A heat-sensitive coloring layer similar to that in Example-1 was provided on this undercoat layer.

The thermal recording papers obtained in Examples 1 and 2 and Comparative Examples 1 and 3 were subjected to Al1 determination with respect to sensitivity, lees, and 1 stone, and the results are shown in Table 1.

Table 1 Color development 7a Degree of lees adhesion 0.44 田J 0.54 田J Example-L L, 25 1.25 02
1.23 1.23 0 Comparative example-11,25
1,150 21,151,150 B 1.25 1.25 .44 It is shown that it shows an excellent color density as in the case of J, and it also shows that it gives good results in terms of lees adhesion. Wide applied energy, ■5- Maintaining a constant color density in the energy range (0.1 mJ or more) is an extremely desirable property for mechanical design such as printers and for good image quality of thermal recording paper. I can say it.

On the other hand, Comparative Example 1 is an example in which a highly oil-absorbing pigment is used, but it shows that the image density decreases when a high applied energy of 0.54 J is applied. Comparative Example 2 is a case where polystyrene is not used, and the color density is low. Comparative example-3
is an example using only polystyrene. Although it showed favorable color density over a wide range of applied energy, it could not be put to practical use due to the degree of lees adhesion.

These measurements were performed as follows.

(1) Sensitivity Measurements were made using an actual thermal facsimile machine modified for testing purposes. The pulse width was modulated under the conditions of one line recording time of 10 m5ec/line, scanning line density of 8 x 8 dots h/mm, and the applied energy per dot was adjusted to 0.44 and 0.54 den J, and 64 lines were recorded. was printed.

-,,1116- The color density at that time was measured using a Macbeth densitometer RD-514, and was taken as a value representative of recording sensitivity.

(2) Degree of lees adhesion The lees on the thermal head were visually inspected.
= There is J's wear, but there is almost no problem in practical use.

[Effects of the Invention] According to the present invention, it is possible to provide a thermal recording paper that has good thermal response and high sensitivity, has no image distortion when coloring is performed with high energy, and has almost no shaft attachment Mm to the thermal head. It became.

Claims (1)

[Claims] In a heat-sensitive recording paper in which a heat-sensitive color forming layer containing a colorless or light-colored electron-donating dye and an electron-accepting compound is provided on a support, an undercoat layer containing polystyrene and a pigment with an oil absorption of less than 100 ml/100 g is used as the support. A heat-sensitive recording material characterized by being provided between a heat-sensitive coloring layer.