JPH01156095A - Thermal recording material - Google Patents

Abstract

PURPOSE:To improve heat response characteristics of a thermal recording paper, by sequentially providing a first intermediate layer comprising a urea-formaldehyde resin or the like, a second intermediate layer comprising a pigment and a thermal recording layer comprising a dye precursor and a color developer, on a base. CONSTITUTION:A first intermediate layer comprising a mixture of a urea-formaldehyde resin and other pigment is provided on a base, and a second intermediate layer which is an under coat layer comprising a pigment is provided thereon. Next, a thermal recording layer comprising a dye precursor and a color developer for developing the precursor into a color when being heated is provided on the second intermediate layer to produce a thermal recording material. The other pigment to be mixed with the urea-formaldehyde resin is preferably an inorganic pigment, and the amount thereof is preferably at least 10wt.% based on the resin. The pigment used for the second intermediate layer is preferably a pigment having an oil absorption of at least 70ml/100g.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a heat-sensitive recording material that is excellent in thermal responsiveness and has little deposits on the thermal head.

(B) Conventional technology Heat-sensitive recording materials generally have a heat-sensitive recording layer on a support, the main components of which are an electron-donating, usually colorless or light-colored dye precursor and an electron-accepting color developer. By heating with a head, heat vent, laser beam, etc., the dye precursor and color developer react instantaneously and a recorded image is obtained. Disclosed. Such heat-sensitive recording materials have the advantages of being able to record with a relatively simple device, being easy to maintain, and not producing U-sound, and are suitable for measurement recorders.

fax machines, printers, computer terminals,
It is used in a wide range of fields such as labels and ticket vending machines. Particularly in the field of facsimile, the demand for heat-sensitive methods has increased significantly, and along with this, efforts have been made to increase speed to reduce transmission costs and to reduce energy consumption by making facsimiles smaller to achieve lower prices. ing. In response to such higher speed and lower energy facsimiles, there has been a demand for higher sensitivity thermal recording materials. On the other hand, the dot density of conventional thermal heads is 8
Book/11! +1 was common, but for example 16/am
The density has been increased and the dot surface roughness has also become smaller, as shown in -
With the need to print small characters with high image quality, gradation printing using the dither method is now required2゛ Good printing performance, that is, the ability to obtain images that faithfully reproduce the dots on the head, is now more than ever required. It has become.

In order to achieve these demands, if the recording paper is strongly treated with a super calender to improve its adhesion to the thermal head, disadvantages such as so-called background fogging, which reduces whiteness, occur.

Japanese Unexamined Patent Publication No. 56-27394 proposes to provide an underlow 1-layer between the heat-sensitive layer and the base paper, which makes it possible to create high-density images with small applied energy without the need for strong supercalendering. As a result, it has become possible to make the fovea more sensitive than before. Application of this undercoat layer is thought to be effective in smoothing the surface after application of the heat-sensitive coating layer by filling in the irregularities of the support and creating a smoother surface.

In this way, higher sensitivity has been achieved by applying an undercoat layer than before, but in recent years, demands for even higher sensitivity and improvements in dot reproducibility have been met by the use of undercoating for the sole purpose of smoothing the surface. It is no longer possible to simply apply a coating layer.

(C) Problems to be Solved by the Invention The present invention provides a thermal paper with good thermal responsiveness in response to the demands for higher sensitivity and improved dot reproducibility, which could not be solved by the conventional techniques. The purpose is to provide.

(D) Means for Solving the Problems To summarize the structure of the present invention, as an undercoat layer provided between the support and the heat-sensitive coating layer, a urea-formaldehyde resin is used as a powder in the second layer and mixed with other pigments. It is characterized by having a two-layer undercoat layer on which a pigment layer is coated as a second layer.

In other words, the coating of the urea-formaldehyde resin powder in combination with other pigments in the second layer simply fills the irregularities of the support and makes it smoother, just like an undercoat layer coated with pigments. In addition to exhibiting the effect of reducing the surface area, the small thermal conductivity of the urea-formaldehyde resin and the air retention properties of the porous urea-formaldehyde resin powder combine to exhibit an insulating effect, and the thermal energy from the thermal head is transferred to the outside of the system. This is thought to show the effect of preventing thermal energy from escaping and allowing thermal energy to act more effectively on the heat-sensitive layer.

However, when a heat-sensitive layer is provided directly on the urea-formaldehyde resin powder layer, the colored components dissolved by the thermal energy from the heat-sensitive head are sucked into the porous urea-formaldehyde resin layer, resulting in a colored image. The pigment layer is hidden and the image density is reduced on the contrary.For this reason, coating a pigment layer as a second layer on top of the urea-formaldehyde resin powder layer prevents this and also prevents the coating of the second layer. This is thought to have the effect of making the already smooth surface even smoother.

Thermal paper produced in this way can maximize the heat insulation effect of the urea-formaldehyde resin alone and achieve the desired improvement in printability, but the porosity of the urea-formaldehyde resin Poor adhesion, which is believed to be due to A problem occurred with the powder accumulating inside the machine. The problem with this problem is that although the adhesive strength increases as the amount of adhesive used increases, depending on the amount used, the heat insulating properties of the urea-formaldehyde resin deteriorate. As a result of studying to solve this problem, we added 10% of other pigments to the urea-formaldehyde resin.
It has been found that the problem can be solved by using the above in combination to form the second layer. However, if a large amount of other pigments are used in combination with the urea-formaldehyde resin, the heat-insulating properties of the urea-formaldehyde resin will be reduced, so the amount of other pigments used in combination will vary depending on the desired effect, but it should be between 1O and 50% by weight. It is preferable that there be.

Pigments used in combination with the urea-formaldehyde resin in the second layer of the present invention include organic pigments other than the urea-formaldehyde resin, such as fine particles of polyethylene, polystyrene, and ethylene-vinyl acetate, and ordinary coated paper. Inorganic surfaces R4 used in More than urea seeds
Can be used in combination with formaldehyde resin.

Examples of pigments used in the second layer of this side are:
Calcium carbonate, kaolin, rll cacao, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, silicon oxide, and other non-TR1 ingredients can be used alone or in combination, and in some cases, urea. - Organic pigments such as fine particles of formaldehyde resin, polyethylene, polystyrene, ethylene-vinyl acetate, etc. can be used alone, in combination of two or more, or in combination with inorganic pigments. Among them, pigments with an oil absorption fi of 70 ml/100 g or more, especially calcined kaolin and silicon oxide, have the above-mentioned effects and can also adsorb heated and melted heat-sensitive coating components without the concealing effect of urea-formaldehyde crumbling powder. It is a preferable pigment because it also has the effect of reducing the adhesion of dross to the heat exchanger.

In the present invention, if the coating amount of the first layer is 1 g/g or more, it will be effective, but if too much is coated, it will affect the paper's properties rather than its heat-sensitive properties.For example, the coating layer will become thicker. If you make the base paper thinner and make the thickness of the smear paper the same, you will have problems with the strength of your back, so 3 to 15g.
The coating amount of the pigment for the second layer is preferably 1 to 10 g/rn' in order to function as the second layer without impairing the effect of the second layer.
If the amount of the second layer applied is too large, heat transfer may deteriorate and the heat retention/insulation effect of the second layer may not be fully utilized.

By providing a heat-sensitive layer on the undercoat coated in this way, the desired properties can be obtained.The dye precursor used in the present invention is generally used for pressure-sensitive recording paper or heat-sensitive recording paper. There are no particular restrictions as long as the
Specific examples include (1) triarylmethane compounds 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (crystal violet lactone thylaminophenyl) phthalide, 3-(p-dimethyl aminophenyl)-3-(1,2-dimethylindole-
3-yl)phthalide, 3-(p-dimethylaminophenyl')-3-(2-methylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3
-(2-phenylindol-3-yl)phthalide,
3,3-bis(1,2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3-bis(
1,2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis(9-nitylrubazol-3-yl)-5-dimethylaminophthalide,
3.3-bis(2-phenylindol-3-yl)-
5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(1-methylvirol-2-yl)
-6-dimethylaminophthalide, etc.

(2) Diphenylmethane compound 4, 4'-bis-dimethylaminophenylbenzhydryl benzyl ether 2 N-halophenyl leucoolamine, N-2. 4. 5-trichlorophenylleucoauramine, etc.

(3) Xanthine compound Rhodamine B anilinolactam, Rhodamine B-p-
Chloroanilinolactam, 3-diethylamino-7-
Dibenzylaminofluorane.

3-diethylamino-7-octylaminofluorane,
3-diethylamino-7-phenylfluorane, 3
-diethylamino-7-chlorofluoran, 3-diethylamino-6-chloro-7-methylfluoran, 3
-diethylamino-7-(3,4-dichloroanilino)
Fluorane.

3-diethylamino-7-(2-chloroanilino)fluorane, 3-diethyla, mino-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-1-lyl)amino-6-methyl-7 -anilinofluorane, 3
-piperidino-6-methyl-7-anilinofluorane,
3-(N-ethyl-N-1lyl)amino-6-methyl-7-phenethylfluorane, 3-diethylamino-7-(4-nitroanilinofluorane, 3-dibutylamino-6-methyl-7- Anilinofluorane.

3-(N-methyl-N-propyl)amino-6-methyl-7-anilinofluorane, 3-(N-ethyl-N
-isoamyl)amino-6-methyl-7-anilinofluorane, 3-(N-methyl-N-cyclohexyl)amino-6-methyl-7-anilinofluorane, 3
-(N-ethyl-N-tetrahydrofuryl)amino-6
-Methyl-7-anilinofluorane, etc.

(4) Thiazine compounds benzoylleucomethylene blue, p-nitrobenzoylleucomethylene blue, etc.

(5) Spiro-based compounds 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3.3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3
-Methylnaphtho-(3-methoxybenzo)spiropyran, 3-propylspilobenzopyran, etc.

These can be used alone or in combination of two or more.

As the color developer used in the present invention, an electron-accepting substance generally used in thermal paper is used.

In particular, phenol derivatives, aromatic carboxylic acid derivatives or their metal compounds, N,N'-diarylthiourea derivatives, etc. are used. Among these, phenol derivatives are particularly preferred.

1.1-bis(p-hydroxyphenyl)propane,
2,2-bis(p-hydroxyphenyl)propane,
2.2-bis(p-hydroxyphenyl)butane,
2.2-bis(p-droxyphenyl)hexane,
Bisphenol sulfone, bis(3-allyl-4-
hydroxyethyl) sulfone, 4-hydroxy-
Examples include 4'-isopropyloxydiphenylsulfone, 4-dihydroxy-4'-methyldiphenylsulfone, diphenol ether, benzyl p-hydroxybenzoate, propyl p-hydroxybenzoate, p-hydroxybenzoate, butyl acetate, etc. It will be done.

Other heat-sensitive coating layers include pigments, sensitizers, and antioxidants.

Anti-sticking agents and the like are added as necessary.

In the present invention, a dye precursor, a color developer, an additive thereof,
Various commonly used adhesives can be used as the adhesive for the urea-formaldehyde resin-pigment mixture used in the undercoat layer, the pigment for the second layer, and the like. for example.

Starches. Hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate.

Acrylic amide/acrylic ester copolymer Acrylic amide/acrylic ester/methacrylic acid ternary copolymer, alkali salt of styrene/maleic anhydride copolymer, alkali salt of ethylene/maleic anhydride copolymer,
water-soluble adhesives such as

Polyvinyl acetate, polyurethane, polyacrylic ester, styrene/butadiene copolymer. Examples include latex such as acrylonitrile/butadiene copolymer, methyl acrylate/butadiene copolymer, and ethylene/vinyl acetate copolymer.

As the support used in the present invention, paper is mainly used, but nonwoven fabrics and plastic films are also used.

Synthetic paper, gold ash foil, etc., or a composite sheet of a combination of these may be used as desired.

(E) Examples Next, the present invention will be explained in more detail by way of examples.

Note that all parts and percentages shown below are based on weight. In addition, the values indicating the smear amount are the smear H after drying unless otherwise specified.
It is.

Example 1 ■Liquid A manufactured by rJFJ (coating liquid for the first layer) A mixture consisting of the following formulation was stirred and used as the coating liquid for the first layer. I made it.

Uniseal (urea-formaldehyde fat disintegration manufactured by Ciba Geigy) 15 parts Ansilex (calcined kaolin manufactured by Engelhard) 5 parts Styrene-butadiene copolymer latex (50% water dispersion product)
6 parts water
80 parts Preparation of liquid B (coating liquid for second layer) A mixture having the following composition was stirred to prepare a coating liquid for second layer.

Ansilex 100 parts styrene-butadiene copolymer latex (50% water dispersion product)
24 parts MS4600 (phosphate esterified starch manufactured by Nippon Shokuhin) (10% aqueous solution) 6
0 parts water
52 parts - Preparation of heat-sensitive coating solution [Liquid C] and [Liquid D] were prepared by pulverizing and dispersing mixtures of the following formulations using a sand mill until the average particle size was approximately 1 μm.

[Liquid C] 3-(N-methyl-N-cyclohexyl)amino-6-
Methyl-7-anirite fluorane
40 parts 10% polyvinyl alcohol aqueous solution
20 parts water
40 parts [Liquid D] Bisphenol A 50 parts Benzyloxynaphthalene 50 parts 10% polyvinyl alcohol aqueous solution 50 parts Water
100 parts ccm] [Liquid D] was used to prepare a heat-sensitive coating liquid according to the following formulation.

[CMl 50 parts [Liquid D]
250 parts zinc stearate (
40% dispersion) 25 parts 10% polyvinyl alcohol aqueous solution 21616 parts Calcilum carbonate
50 parts water
417 parts Each of the coating solutions thus prepared was smeared on a base paper having a basis weight of 40 g/m' using a Meyer bar in the following smearing amounts to prepare heat-sensitive recording materials.

Layer 3 3 g/rr? The second layer 3 g/ is a heat sensitive layer! 5-5 g/ is Examples 2 to 4 Heat-sensitive recording materials were prepared in the same manner as in Example 1 except that 7 g, 10 g, and 14 g/rrP were smeared instead of the 13 g/rr smear of the first calendar in Example 1. did. Examples 5 to 7 Instead of the smear amount of the first layer of 3 g/rrf in Example 1, 7 g In1'' was smeared, and the second layer was applied on top of that with Ig, 6 g.
.

A heat-sensitive recording material was prepared in the same manner as in Example 1 except that 9 g/rrf' was smeared.

Example 8 In the preparation of liquid B (coating liquid for second layer) in Example 1, 100 parts of Ultra White-90 (Kaolin for illumination by Engelhard Co., Ltd.) was used instead of 100 parts of Anterex.
Solution B was prepared in the same manner as in Example 1, except that 1 part was used.
Liquid] A heat-sensitive recording material was prepared by applying the heat-sensitive coating liquid to a base paper of 140 g/rn'' with a Meyer bar to the following drying amount.

Stone 7 g/rIf' Second layer 3 g/rr? Heat Sensitive 1N 5.5 g/Example 9 In the preparation of Solution A (coating solution for the first layer) in Example 1, 15 parts of urea-formaldehyde resin was used.

Solution A was prepared in the same manner as in Example 1 using 12 parts of urea-formaldehyde resin and 8 parts of Ansilex instead of 5 parts of Ansilex. lI
] and [Liquid B (heat-sensitive coating liquid) prepared in Example 1 were applied to a base paper of 140 g/ba with a Meyer bar to the following drying amount to prepare a heat-sensitive recording material. .

-th layer 7 g/+n' Second layer 3 g/G heat-sensitive layer 5.5 g/ru Department.

A heat-sensitive recording material was prepared in the same manner as in Example 1, except that 8 parts of urea-formaldehyde resin and 12 parts of Ansirex were used instead of 8 parts of Antellex.

Example 11 In the preparation of liquid A (coating liquid for the first layer) in Example 1, Ultra White-9 was used instead of 5 parts of Ansilex.
A heat-sensitive recording material was prepared in the same manner as in Example 1, except that 5 parts of Kaolin 0 (kaolin for coating manufactured by Engelhard) was used.

Specific gravity 2 Saturation I 1 Coating for the first layer of the coating liquid prepared in Example 1: smear 8 g/g of the coating liquid for the second layer directly on the base paper without smearing the thorns, and then apply the heat-sensitive coating liquid on top of it. A heat-sensitive recording material for comparison was prepared by smearing 5.5 g/rn2.

Comparative Example 2 Of the coating solution prepared in Example 1, 7 g of the coating solution for the second layer was smeared directly onto the base paper without coating the coating solution for the second layer, and then the coating solution for the second layer was applied again. 3 g/l of the solution was smeared to form an undercoat, and then 5.5 g/r of heat-sensitive 1ji'ja was smeared thereon to prepare all heat-sensitive recording materials for comparison.

Comparative Example 3 A heat-sensitive recording material for comparison was prepared by applying 7 g/rIf1 of the coating liquid for the first layer in Example 1 and then directly applying the heat-sensitive coating liquid in the same manner as in Example 1 without applying the second layer. .

Comparative Example 4 In Example 9, 12 parts of urea-formaldehyde resin and 8 parts of Antellex were replaced with 20 parts of urea-formaldehyde resin, and AM(
A comparative heat-sensitive recording material was prepared in the same manner as in Example 9, except that the coating liquid for the second layer was prepared.

Comparative Example 5 Each of the coating liquids prepared in Example 1 was smeared onto a base paper at the following smear length in the same manner as in Example 1 to prepare a comparative heat-sensitive recording material.

No.-rgi7g/rII! The heat-sensitive recording material thus prepared was treated with a supercalender to a Beck smoothness of 400 to 500 seconds, and Recording density, printability, and degree of scum adhesion were compared using a testing machine. The test machine was Daikin'C machine fxi (
A thermal head with a dot density of 8 dots/mm (TH-PMD) and a head resistance of 185 Ω was used, and printing was carried out at a head voltage of 11×2 and current application times of 0°5 ms and 0.8 ms. Please note! The density was measured using a Macbeth RD-514 reflection densitometer (type 0), and the adhesion was written on the coated surface of the heat-sensitive recording material prepared using a pencil. The extent of paint peeling was observed. These results are shown in Table 1.

(Left below) Table 1 (F) Effect As is clear from the results in Table 1, the heat-sensitive recording material of the present invention has 1JX old in the second layer, which is used in combination with urea-formaldehyde resin and other pigments. However, a heat-sensitive coating layer is coated on top of the undercoat layer, which had a coating layer made of a plate material in the second generation, and does not cause peeling of the coating layer or powder falling, and is more durable than conventional heat-sensitive recording materials. Thermal response was improved, and improved sensitivity and dot reproducibility were achieved without increasing head adhesion.

Claims (1)

[Scope of Claims] 1. In a heat-sensitive recording material containing a dye precursor and a color developer that causes the dye precursor to develop color when heated, a urea-formaldehyde resin is provided as a first layer between the support and the heat-sensitive recording layer. 1. A heat-sensitive recording material characterized by having an undercoat layer coated with a mixture of and other pigments and further coated with a pigment as a second layer thereon. 2. The heat-sensitive recording material according to claim 1, wherein the other pigment mixed with the urea-formaldehyde resin is an inorganic pigment. 3. The heat-sensitive recording material according to claim 1 or 2, wherein the other pigment mixed with the urea-formaldehyde resin accounts for 10% by weight or more of the urea-formaldehyde resin. 4. The heat-sensitive recording material according to claim 1, 2 or 3, wherein the pigment used as the second layer of the undercoat layer has an oil absorption amount of 70 ml/100 g or more. 5. The heat-sensitive recording material according to claim 4, wherein the pigment having an oil absorption of 70 ml/100 g or more is calcined kaolin or silicon oxide.