JPH04371885A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material having excellent heat resistance, water resistance, chemical resistance, writing characteristics and characteristics hard to injure by improving the protective layer provided on a thermal recording layer. CONSTITUTION:A thermal recording material wherein a thermal recording layer is provided on a support is characterized by that a protective layer based on a polysiloxane compound is provided on the thermal recording layer.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a heat-sensitive recording material, and in particular, by providing a protective layer containing a polysiloxane compound as a main component on a heat-sensitive recording layer, heat resistance,
The present invention relates to a heat-sensitive recording medium with improved water resistance, writing characteristics, etc.

0002

[Prior Art] A heat-sensitive recording material having a heat-sensitive recording layer containing a leuco dye and a color developer has primary color development and does not require development.
The paper quality is similar to that of regular paper, the color density is high, and it is easy to handle, so it is widely used.In particular, this thermal recording material is used for facsimile, because the maintenance of the recording equipment is relatively easy. It is used in large quantities in various fields such as printers and ticket issuing machines.

However, since the leuco dye and color developer contained in the heat-sensitive recording layer are easily dissolved in various solvents, this heat-sensitive recording material is susceptible to ink when it comes into contact with inks such as water-based ink pens or oil-based ink pens, adhesives, glue, etc. There were drawbacks such as white areas becoming colored and printed areas disappearing. In order to eliminate such drawbacks, Japanese Patent Publication No. 44-27880, Japanese Patent Application Publication No. 48-30437, and Japanese Patent Application Publication No. 48-31958 disclose various binders made of organic polymer substances and the addition of a crosslinking agent to the binder. Disclosed is a heat-sensitive recording material in which a protective layer made of the above-mentioned material is provided on a heat-sensitive recording layer. However, these conventional protective layers are heat resistant, water resistant, chemical resistant,
There was also a problem of poor writing characteristics.

0004

[Problems to be Solved by the Invention] The present invention has improved heat resistance, water resistance, chemical resistance, writing characteristics, and scratch resistance by improving the protective layer provided on the heat-sensitive recording layer. The purpose is to provide a thermosensitive recording medium.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a heat-sensitive recording material having a heat-sensitive recording layer on a support, the heat-sensitive recording layer containing a polysiloxane compound as a main component. The object of the present invention is to provide a heat-sensitive recording material characterized by being provided with a protective layer. The protective layer of the present invention provided on the heat-sensitive recording layer is mainly composed of a polysiloxane compound, and is formed by applying a protective layer coating solution containing a hydrolyzate of alkoxysilane onto the heat-sensitive recording layer. do.

The protective layer coating solution of the present invention is prepared by mixing an alkoxysilane or a mixture of two or more alkoxysilanes, an acid and water, and hydrolyzing the alkoxysilane while making a uniform dispersion by high-speed stirring or the like. Prepare. Alkoxysilane or a mixture thereof is subjected to a hydrolysis reaction in the presence of an acid catalyst, and then applied to cause a polycondensation reaction to produce a polysiloxane compound, which is then cured at room temperature or by heating to form a protective layer. It is something that forms.

[0007] Normally, hydrolysis of alkoxysilane is carried out in an organic solvent such as alcohol, which is a common solvent for both alkoxysilane and water, in order to uniformly mix the two, but in the present invention, a common solvent is used. First, it is characterized by obtaining a uniform aqueous solution by high-speed stirring or the like. Therefore, the protective layer coating liquid of the present invention has a low organic solvent content, and in particular, a coater (coating machine) without an explosion-proof device can be used. The protective layer coating solution is unstable and tends to gel, so it is desirable to use it immediately after preparation.

The alkoxysilane used in the protective layer coating solution of the present invention is particularly suitable for those whose alkyl group has 1 to 4 carbon atoms.
Trialkoxysilanes in which alkoxy has 1 to 3 carbon atoms are preferred, and examples include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, and mixtures thereof.

The acids used in the protective layer coating solution of the present invention include inorganic acids such as nitric acid and hydrochloric acid, as well as formic acid, acetic acid, propionic acid, maleic acid, chloroacetic acid, citric acid, benzoic acid,
Organic acids such as dimethylmalonic acid, glutaric acid, glycolic acid, malonic acid, toluenesulfonic acid, and oxalic acid can be mentioned. The amount of such acid added is 0.01 to 3 parts by weight, preferably 0.5 to 1.5 parts by weight, per 100 parts by weight of the alkoxysilane. The reason for specifying this is that if the amount is less than 0.01 parts by weight, the hydrolysis of the alkoxysilane will be insufficient, while if it exceeds 3 parts by weight, the coating liquid will tend to gel.

[0010] Furthermore, the proportion of water in the protective layer coating solution used in the present invention is set to be at least the minimum amount required for complete hydrolysis of trialkoxysilane, which is calculated from the reaction formula for complete hydrolysis of trialkoxysilane. . For example, 0.4 g or more of water is used for 1 g of methyltrimethoxysilane, and 0.3 g or more of water is used for 1 g of methyltriethoxysilane.

Therefore, the amount of water in the protective layer coating solution is 500 to 3000 parts by weight per 100 parts by weight of alkoxysilane.
Parts by weight, preferably 800 to 1500 parts by weight. Furthermore, conventionally used fillers and lubricants can be added to the protective layer coating solution depending on the purpose. Further, an intermediate layer mainly composed of conventionally used organic polymeric substances may be provided between the main protective layer and the heat-sensitive layer.

[0012] Examples of the support used in the present invention include various papers such as wood-free paper, medium-quality paper, coated paper, and recycled paper including waste paper, various nonwoven fabrics, plastic films, synthetic papers, metal foils, etc. . When paper is used as the support, the basis weight of the paper is 20 to 400 g/m2, preferably 30 to 200 g/m2. For the heat-sensitive recording layer of the present invention, dye-type and pigment-type heat-sensitive recording layers can be used. Among them, leuco dyes used in dye-type heat-sensitive recording layers include triallylmethane dyes, thiazine dyes,
Examples include spiro dyes, lactam dyes and various fluoran compounds.

Further, in the present invention, the color developer used in combination with the leuco dye is not particularly limited, and has the property of being liquefied, vaporized, or dissolved by an increase in temperature, and is compatible with the leuco dye. These are various color developers that have the property of causing coloration upon contact. Examples of typical color developers include 4-tert.
- Aromatic carboxylic acids such as butylphenol, α-naphthol, 4-acetylphenol, hydroquinone monobenzyl ether, 4-hydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, terephthalic acid, and these phenolic compounds , organic acidic substances such as salts of aromatic carboxylic acids and polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel.

One of the materials used for the pigment type heat-sensitive recording layer is an organic acid heavy metal salt or an organic acid noble metal salt;
On the other hand, there are organic reducing agents, sulfur compounds, amino compounds, and the like. Coating liquids containing these are generally prepared by using water as a dispersion medium, and dispersing the leuco dye and color developer together or separately using a ball mill, attritor, sand grinder, or other stirring or crushing machine to prepare the coating liquid. do.

Such coating liquids usually contain starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene/maleic anhydride copolymer salt, styrene/butadiene copolymer as binders. Emulsions etc. are 2 to 40% by weight of total solids,
It is preferably used in a proportion of 5 to 25% by weight. Furthermore, various auxiliary agents can be added to the coating liquid as necessary. Examples include dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, other antifoaming agents, fluorescent dyes, and coloring dyes.

In the heat-sensitive recording material of the present invention, the method of forming the heat-sensitive recording layer is not particularly limited, and can be formed according to conventionally well-known and commonly used techniques. For example, in a method of applying a heat-sensitive coating liquid to a support, an appropriate coating device such as an air knife coater or a blade coater is used. The amount of the coating liquid to be applied is not particularly limited, but it is generally in the range of 2 to 15 g/m2, preferably 3 to 10 g/m2 in terms of dry weight.

Furthermore, an intermediate layer using an inorganic pigment such as calcined kaolin or silica or an organic pigment such as a plastic pigment may be provided between the support and the heat-sensitive recording layer.
Various known techniques in the field of thermosensitive recording materials can be added.

[0018]

EXAMPLES The present invention will be explained in detail below based on Examples, but the present invention is of course not limited to the scope of these Examples. Manufacture of thermosensitive recording material Liquids A and B having the following compositions were respectively prepared. Liquid A leuco dye 3-(N-ethyl-N-isoamyl)amino-6-
Methyl-7-anilinofluorane (Yamada Chemical S-
205) 10 parts by weight 12% polyvinyl alcohol aqueous solution
30 〃 Polystyrene ammonium acrylate 20% aqueous solution
2 Water

8 The above ingredients were dispersed using a sand grinder until the average particle size was 1 μm. B liquid bisphenol A

18 parts by weight m-terphenyl

22 〃 Polyvinyl alcohol 12% aqueous solution
50 〃 Polystyrene ammonium acrylate 20% aqueous solution
3 Water

57 The above ingredients were dispersed using a sand grinder until the average particle size was 1 μm.

The above was prepared by dispersing it in a homomixer for 10 minutes. Next, 50 parts by weight of liquid A, 150 parts by weight of liquid B, and 42 parts by weight of a 12% polyvinyl alcohol aqueous solution were mixed to prepare a heat-sensitive coating liquid. The heat-sensitive coating liquid prepared in this manner was coated on high-quality paper with a dry weight of 5 g/m2.
It was coated with a wire bar to give a coating thickness of m2 and dried in an oven at 50°C.

Example 1 0.5 g of acetic acid was added to 449.5 g of distilled water, and while stirring at high speed, 50 g of methyltrimethoxysilane was gradually added to dissolve completely, resulting in methyltrimethoxysilane with a solid content of about 5%. An aqueous solution of methoxysilane hydrolyzate was obtained. This aqueous solution was coated with a wire bar on the heat-sensitive layer prepared as described above so that the dry coating amount was 3 g/m2.
A thermosensitive recording material was obtained by drying at °C.

Example 2 Methyltriethoxysilane was used in place of methyltrimethoxysilane in Example 1 to obtain an aqueous solution with a solid content of about 4%. Using this aqueous solution, a thermosensitive recording material was obtained in the same manner as in Example 1. Comparative Example 1 Instead of the protective layer coating solution containing methyltrimethoxysilane used in Example 1, a polyvinyl alcohol aqueous solution (PV
A thermosensitive recording material was obtained in the same manner as in Example 1 except that a 5% solution of A-105 (manufactured by Kuraray) was used.

Comparative Example 2 Except that a 5% aqueous solution of starch was used instead of the protective layer coating solution containing methyltrimethoxysilane used in Example 1.
A thermosensitive recording material was obtained in the same manner as in Example 1. Comparative Example 3 A thermosensitive recording material was obtained in the same manner as in Example 1 except that a 5% aqueous solution of methyl cellulose was used instead of the protective layer coating solution containing methyltrimethoxysilane used in Example 1.

Comparative Example 4 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that a 5% aqueous casein solution was used instead of the protective layer coating solution containing methyltrimethoxysilane used in Example 1. . Comparative Example 5 Polyvinyl alcohol aqueous solution 700 used in Comparative Example 1
g, amorphous silica (Mizukasil P527 Mizusawa Chemical) 2
0g was gradually added, and a dispersion of zinc stearate (Hydrin D-523 manufactured by Chukyo Yushi Co., Ltd.: solid content 3) was added as a lubricant.
A thermosensitive recording material was obtained in the same manner as in Example 1, except that 33.3 g of 0%) was added and this mixed solution was used.

Comparative Example 6 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that phenyltrimethoxysilane was used instead of the protective layer coating solution containing methyltrimethoxysilane used in Example 1. The thermosensitive recording bodies obtained in Examples 1 to 2 and Comparative Examples 1 to 6 were
Calendar treatment was performed using a gloss calendar to obtain a heat-sensitive recording material with a recording surface having a Bekk smoothness of 1,000 seconds.

The heat-sensitive recording bodies obtained in Examples 1 to 2 and Comparative Examples 1 to 6 were evaluated, and the results are shown in Table 1. Printing: Printing was performed using a thermal tester TH-PMD (manufactured by Okura Electric) under the following conditions.・Thermal head: KJT-256-8HGF1 (manufactured by Kyocera) ・Applied voltage: 24.0V ・Pulse period: 2msec ・Pulse time: 1.2msec 1.8
The density of the msec recording section is measured using a Macbeth densitometer (RD-514).
). 1) Sticking resistance Using an image printer VP-35 (manufactured by Seiko Electronics), printing was performed at a coverage rate of 100%, and the coloring state and sticking sound were evaluated.

2) Pulse width 1.9 mse using chemical resistance heat sensitive tester TH-FMD
Acetone was dropped onto the area printed solidly in step c, and the recorded area was visually observed to examine chemical resistance. The evaluation was ``×'' if fogging occurred, and ``○'' if no fogging occurred.

2-1 Water resistance: immersed in water for 24 hours,
The recorded portion was visually evaluated. 2-2 Oil resistance: Soaked in salad oil for 24 hours,
The recording part was visually observed and evaluated. 2-3 Plasticizer resistance: Eraser (Tombow Homo PE-OI
A) was placed on the recording section, a load of 200 gf/cm2 was applied, and the recording section was left for 3 days, and then the recording section was visually evaluated.

2-4 Highlighter resistance: Highlighter pen (ZE
A line was drawn on the recording area using BRA PEN2), and visually evaluated one day later. Judgment ○: The recording section has hardly changed from before storage. Δ: The recording part is legible. x: Most of the recorded area is discolored.

[0029]

Effects of the Invention As is clear from the results of Comparative Examples 1 to 4 in Table 1, when a conventional aqueous solution of an organic polymer substance is used as a protective layer without adding pigment or lubricant, sticking is large and the printed area is White spots appear. On the other hand, as is clear from Comparative Example 5, sticking can be improved by adding a pigment or a lubricant, but in this case, the print density is significantly reduced.

On the other hand, as is clear from Examples 1 and 2 in Table 1, the heat-sensitive recording material of the present invention using a polysiloxane compound as the protective layer can be used without adding any pigment or lubricant to the protective layer. It has high heat resistance, so there is no sticking, and print density is high, and it also has excellent chemical resistance. Therefore, according to the present invention, a thermosensitive member having excellent heat resistance, water resistance, chemical resistance, and writing characteristics can be obtained.

[0031]

[Table 1]

Claims (1)

[Claims] 1. A heat-sensitive recording material having a heat-sensitive recording layer on a support, characterized in that a protective layer containing a polysiloxane compound as a main component is provided on the heat-sensitive recording layer.