JPS6027590B2 - heat sensitive recording material - Google Patents

Description

[Detailed description of the invention] The present invention relates to a so-called thermosensitive recording medium.

More specifically, the present invention relates to a heat-sensitive recording material particularly excellent in responsiveness to high-speed heat pulses. Printers, plotters, facsimile machines, etc. have made remarkable advances in recent years in order to meet the recent demands of society to output large amounts of information as hard copies as quickly as possible.

Among these, thermal recording methods, so-called heat-sensitive methods, are increasingly being adopted as recording means.

Among such thermal recording methods, methods using a thermal head have recently attracted particular attention.

In this recording method, as illustrated in FIG. 1, a recording paper 3 is composed of a support 1 made of paper, plastic, etc., and a heat-sensitive recording layer 2 formed by coating or impregnating the support. On the other hand, passion is inputted from the thermal head 4, and a colored image is formed on the recording paper 3. That is, first, a signal generated from the power supply unit 5 is transmitted to the thermal head 4 via an electric circuit (not shown). Here, a resistor included in the thermal head 4 generates heat, and an image 6 corresponding to the signal is obtained in the heat-sensitive recording layer 2. The advantages of the thermal recording method explained above are:
Use of primary color recording material, ■ Maintenance free, ■ Recording material is inexpensive and easy to handle, ■ The device can be miniaturized, and ■ Non-impact, so it is noiseless. (2) The recording system including the device can be obtained at low cost.

However, on the other hand, the following drawbacks have been pointed out in the conventional heat-sensitive recording method. The biggest drawback of the thermal recording methods known up to now is that the printing speed is extremely slow compared to other recording methods.

For example, commonly used heat pulses are on the order of 10 to 20 milliseconds, and even particularly fast pulses are no more than 5 to 6 milliseconds long. In this way, conventionally,
Two factors can be pointed out to make high-speed printing impossible with thermal recording. The first was that there was no thermal head that could withstand rapid temperature changes (rising and falling), and the second was that there was no thermal recording material that was highly sensitive and had a satisfactory shelf life. That's true.

In consideration of the above factors, research is currently underway to improve thermal heads and thermal recording materials in order to achieve a high-speed thermal recording system. Therefore, the main object of the present invention is to provide a heat-sensitive recording medium that is compatible with a high-speed heat-sensitive recording system that is not available in other conventional methods.

At the same time, it is also an object of the present invention to provide a thermal recording medium that has a low background density and good adhesion to a thermal head. Furthermore, it is another object of the present invention to provide a heat-sensitive recording material with improved responsiveness to heat pulses. In short, the present invention that achieves the above-mentioned object includes a recording layer whose basic composition is a heat-sensitive coloring component and a binder, and a support made of a loose material, and a glass layer is provided between the recording layer and the support. Transition point is 60
This heat-sensitive recording material is characterized in that the surface of the recording layer is smoothed to a Bekk smoothness of 100 or more of silica sand by interposing an intermediate layer made of a film-forming polymer material having a qC or less. According to various studies conducted by the present inventors, this method has hardly been put to practical use in the field of thermal recording.

For example, when using a heat pulse of 1 millisecond or less, it is necessary to devise ways to improve the adhesion between the head and the recording material so that the heat conduction from the thermal head to the recording material is better than in conventional methods. For this reason, the surface of the recording material is required to have a high level of smoothness, for example, 100 mm or more (Beck smoothness). It has also been found that in order to increase the color development sensitivity by imprint heating, it is necessary to increase the density of the color development component contained in the recording layer. Based on the above findings, if the recording layer paint containing high-density color-forming components is applied to paper and then the recording paper is passed between mirror-polished pressure rollers in order to increase the surface smoothness, the background density of the recording paper will decrease. As a result, the contrast with the recorded image decreases, and the color development sensitivity itself becomes extremely low. In the present invention, the above-mentioned disadvantages can be overcome by providing a predetermined intermediate layer between the recording layer and the support (for example, paper).

In other words, as shown in FIG. 2, the present invention provides a bond between a support 201 such as paper or a resin film and a recording layer 2.02 formed of a thermosensitive coloring component and a binder resin as its basic composition. This is a heat-sensitive recording material comprising an intermediate layer 20.3 made of a film-forming polymer having a glass transition point of about 6000 or less. The intermediate layer 203 of the present invention exhibits rubber-like elasticity during the smoothing treatment (for example, passing between pressure rolls) on the surface of the recording layer 202 in the recording medium, thereby dispersing the pressure or heat applied to the recording layer. This serves to prevent the background density from increasing in the recording layer 202. In addition, when such an intermediate layer 203 is present, the recording layer paint does not penetrate the paper that is the support, so the amount of coating is less than that of the conventional method, which is economical, and the recording paper is It has the advantage that the feeling is not impaired.

Furthermore, it is easy to increase the smoothness of the intermediate layer 203 itself at the coating stage, and the recording layer 2 coated thereon
Another advantage is that smoothing of the 02 surface can be performed more easily and accurately than in the past. Here, the present invention will be further explained in detail by giving specific examples.

In the present invention, the material forming the intermediate layer is preferably a polymer having a glass transition point of 60:00 or lower, and exhibits rubber-like elasticity under normal usage conditions. Specifically, for example, polygenes such as natural rubber (polysoprene), neoprene, polybutadiene, polybentenylene, etc., polyalkenes such as polybutene, polyethylene, polyisobutylene, polymethylene, polypropylene, etc., polybutyl acrylate, poly2- Polyacrylic acid and polyacrylic acid esters such as cyanoethyl acrylate, polycyclohexyl acrylate, polyethyl acrylate, polymethyl acrylate, polymethylbutyl acrylate, polypropyl acrylate, polybutyl methacrylate, poly(2-ethylhexyl methacrylate, poly Polymethacrylic acid and polymethacrylic acid esters such as (isobutyl methacrylate), polyoctadecyl methacrylate, etc., polyvinyl ethers such as polyptoxyethylene, polybutylthioethylene, polyethoxyethylene, polypropoxyethylene, etc. and polyvinyl halides, including polyvinyl thioethers, poly(1,1-dichloroethylene) polytrifluoroethylene, polyvinyl fluoride, polyvinyl acetate, polycyclohexylacetoxyethylene, polyformyloxyethylene, polyformyloxyethylene, etc. Polyvinyl esters such as tyrene, poly(5-fromo2-isobentylstyrene)
, polystyrenes such as poly(4dodecylstyrene), polyoxides such as polyoxybutadiene and polyoxypropylene, polyesters, polyurethanes, polysiloxanes, polysulfides such as thiocol, It is selected from polyamides such as nylon 6 and nylon 4,6, and polymers such as styrene-butadiene and butadiene-methyl methacrylate. The above-mentioned polymers may be used alone or in combination of two or more. Moreover, it is also possible to stack two or more layers. These polymers can be applied in the form of a solution in a solvent or in the form of an emulsion. In addition, for the intermediate layer, the coating conditions may be changed, the surface adhesion may be adjusted, and other additives may be added as appropriate.

In the present invention, the layer thickness of such an intermediate layer is 0.5 to 8 μm (
. . . dry film thickness), and 1 to 3 peaks is a practical range.

The recording layer of the present invention provided on this intermediate layer mainly contains a thermosensitive coloring component and a binder, and further contains additives (a writability improver,
(anti-blocking agent, whitening agent, etc.). As the heat-sensitive coloring component, a colorless or flame-colored coloring compound and a phenolic compound are usually used in combination.

For example, examples of the former include 3,3-bis(P-dimethylaminophenyl)-6-dimethylaminophthalide (crystal violet lactone), 3,3-bis(P-dimethylaminophenyl) phthalide (malachite green lactone), etc. Triphenylmethane derivatives such as 3-cyclohexylamino-6-chlorofluoran 3-diethylamino-6-methyl-7-P-n butylphenylamino-fluoran 3-diethylamino-6-methyl-7-chlorofluoran , 3-diethylamino-6-methyl-7-anilinofluorane, 3,6-bis-(N,N-diethylamino)fluoran, etc.; ) Naphthalide 3-(3'-methyl-4'-dimethylaminophenyl)-3-(3''-methyl-4''-dimethylaminophenyl)-6 (or 7) Naphthalide derivatives 3 such as nitronaphthalide -(4'-diethylaminophenyl)-31(4'-dimethylaminophenyl)17-azaphthalide31(4'-dibenzylamino-2-methoxyphenyl)131(4') Azaphthalides 31 (p-dimethylaminophenyl) 13-(1-methylpyrrole-2-yl) 16-dimethylaminofluoride 31 ( p-dimethylaminophenyl)-3-(1.
Heterocyclic allyldiphenylmethane derivatives cis-3,5-bis-(p-diethylaminophenyl)-3,5-bis-(1,2- Pyromellitic anhydride derivatives, such as dimethylindol-3-yl)pyromellitide; diphenylmethane derivatives, such as phenyl-0-rupoxyphenylhydroxymethane lactone; 9-paranitroanilino-3,6-pis- Color-forming lactam compound 3, exemplified by the lactam of (diethylamino)-9-xanthenyl-orthobenzoic acid
,6-bis(diethylamino)-9-hydroxy-9
1,3,3-trimethylindolino-8-methoxybenzopyrylspirane 1,3,3-trimethylindolino-8-methoxybenzopyrylspirane,
Color-forming spiropyran compounds such as 3-trimethyl-5-chloroindolino-8'-ethoxyspiran, tris-(p-dimethylaminophenyl)methane, bis(p-dimethylaminophenyl)p-dimethylal Color-forming leucotriphenylmethane compounds such as minnow 0-lupoxyphenylmethane Color-forming leukodiphenylmethane compounds such as bis(p-dimethylaminophenyl)methane, tryptophan, leukoolamine, etc. 3, Color-forming acylphenothiazine compounds include 7-bis-dimethylamino-10-acetylphenothiazine, 2-methyl-3-amino-7-dimethylamino-10-p-methoxybenzoylphenothiazine, and the like.

Phenolic compounds that react with the above compounds include bisphenol A, 2,2-bis(4-hydroxyphenyl)n-heptane 1,1-dis(4-hydroxyphenyl)cyclohexane, Q naphthol, 8-naphthol, 4- Examples include tertiary butyl phenol and novolac type phenol resin. Among these, phenolic compounds having many hydroxyl groups in one molecule are desirable. As a binder, starch, sodium alginate, gum arabic, dextrin, gelatin, casein, albumin, methylcellulose, ethylcellulose, hydroxyethylcellulose, acrylamide, carboxymethylcellulose, hydroxymethylcellulose, dialdehyde starch, polyvinyl alcohol, polyester sodium acrylate,
Polyethylene oxide, polyvinylpylene.

In addition to water-soluble polymers such as lydone, polyvinyl methyl ether, and polyvinylethyl ether, polyvinyl acetate, styrene-butadiene copolymer, vinyl chloride-vinylidene chloride copolymer, and styrene-acrylonite copolymer Emulsions of single or tertiary copolymer polymers such as the following can also be used. Furthermore, emulsions of other water-soluble resins can also be used, and these emulsion-based binders and water-repellent resins can also be used in combination. The heat-sensitive recording material of the present invention can be manufactured generally by the following method.

First, a recording layer paint is prepared as follows. The above-mentioned color-forming compound, binder (dispersant, antifoaming agent, brightener, etc. may be added from the beginning or during the process), and a solvent are sufficiently dispersed and kneaded. Further, the phenolic compound, binder and solvent are sufficiently dispersed and kneaded. Separately, a paint containing one or more of the above-mentioned stiffening polymers is applied onto a support (for example, paper) by a method such as roll coating, bar coating, spray coating, dipping, etc. form an intermediate layer.

At this time, pigments and other additives may be included in the paint as necessary. After drying the intermediate layer, a recording layer paint containing a mixture of the color-forming compound liquid and the phenolic compound liquid is applied thereon. After the above is dried (further, a wax liquid or the like may be applied as a protective film), the surface of the recording medium is smoothed by passing it between pressure rollers whose surface has been mirror-polished. The degree of smoothing is adjusted by appropriately selecting the smoothness of the roller surface and the degree of pressure between the rollers. The present invention described above will be explained in more detail by way of Examples.

The effects of the present invention will be more clearly understood based on the following examples. Example 1 A coloring liquid was prepared with the following composition.

Next, a phenolic compound was prepared with the following composition.

Each liquid was sufficiently kneaded using a ball mill. Next, the thickness is 70
A pile of high-quality paper was prepared, and a styrene-butadiene copolymer emulsion (20% concentration) was applied thereto using a coating rod bar and dried.

(...This is the sample of the present invention.) Also, 8U, untreated high-quality paper (...comparative sample No. 1), high-quality paper coated with polyacrylamide (...comparative sample No. 2), high-quality paper Applying polyvinyl alcohol to paper (...comparative sample M.3)
, polystyrene coating on high-quality paper (...comparative sample M.4)
I prepared what I did. All of the above coating films were made into two layers (after drying). A 1:1 mixed solution of the above-mentioned color developing solution and phenolic compound solution was applied onto each sample to a film thickness of 5 μm, and dried. Next, as a smoothing treatment, each sample was passed through mirror-finished stainless steel rollers with a linear pressure of about 20 kg/skin a predetermined number of times, and the skin density of each sample after the treatment was measured (manufactured by Macbeth Co., Ltd.). ) Measured using a spectrodensitometer.
The results were as shown in Table 1. From the results shown in Table I, it can be seen that the recording paper according to the present invention does not significantly increase the background density during the smoothing process.

Among the above samples, the present invention sample and comparative sample No. 1
The relationship between the number of roller treatments and surface smoothness was investigated.

The smoothness was determined by Beck smoothness (in seconds). The results are shown in Table 2. Table 2 The intermediate layer of the present invention also contributes to improving the surface smoothness of recording paper.

Examples 2 to 13 After coating a high-quality paper with a thickness of 70 mm with the polymers shown in Table 3 below, the same recording layer paint as shown in Example 1 was applied and dried. , each passed between mirror-finished stainless steel rollers having a linear pressure of about 20k9/arc.

Background density and surface smoothness of recording paper after processing (...
The Bekk smoothness) was as shown in Table 3. Table 3 Example 14 Printing was carried out by applying a thermal head to each of the recording papers obtained in Examples 1 to 13 and subjected to surface smoothing treatment.

The printing conditions are; head size: 0.2 ribs xo. 2 skins, stamping energy 3 melon hJ/Kyo, 100 msec pulse, 4 pieces/skin. As a result, a clear colored image was formed on each recording paper according to the size of the head without uneven printing.

[Brief explanation of drawings]

FIG. 1 is a schematic drawing for explaining the outline of a thermal recording method using a thermal head, and FIG. 2 is a schematic cross-sectional view showing an example of the structure of a thermal recording medium of the present invention. In the figure, 1,201...Support, 2,20
2... Recording layer, 203... Intermediate layer.
Little brother l figure 2

Claims (1)

[Scope of Claims] 1. A recording layer basically composed of a heat-sensitive coloring component and a binder, and a support made of paper, with a glass transition temperature of 60° C. or less between the recording layer and the support. 1. A heat-sensitive recording material, characterized in that the surface of the recording layer is smoothed to a Beck smoothness of 1000 seconds or more by interposing an intermediate layer made of a film-forming polymeric substance. 2. The heat-sensitive recording material according to claim 1, wherein the intermediate layer has a layer thickness in the range of 0.5 to 8 μm. 3. The heat-sensitive recording material according to claim 1, wherein the intermediate layer exhibits rubber-like elasticity.