JP3300823B2 - Method for producing reversible thermosensitive recording material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive layer (reversible thermosensitive layer).
Method for producing a reversible thermosensitive recording materials for recording and erasing by using a reversible transparency change due to temperature.

[0002]

2. Description of the Related Art Many reversible thermosensitive recording materials have been proposed, and a typical example thereof is that a low-molecular organic substance such as a higher fatty acid is contained in a resin base material such as a vinyl chloride resin. A reversible thermosensitive recording material having a dispersed thermosensitive layer is known (JP-A-54-119377;
JP-A-55-154198, etc.). Image formation and erasing with this type of recording material utilize reversible changes in the transparency of the heat-sensitive layer with temperature, but the temperature at which the opaque portion is transparent is generally low, and there are some differences depending on the higher fatty acid used. Of about 65 to 72 ° C., and the width of the transparentizing temperature range is as narrow as 2 to 4 ° C. For this reason, use in a high-temperature environment is limited, and there is a problem in that at least a part of the entire opaque recording material is made transparent, or a temperature control when forming a transparent image on the entire opaque recording material is difficult. There was a practical problem.

In consideration of these points, the present inventors have previously described Japanese Patent Application Laid-Open Nos. 63-39378 and 63-13-13.
Japanese Patent Application Laid-Open No. 0380, JP-A-1-123788, etc., it is possible to obtain a transparent material by containing a certain kind of organic low-molecular substance (fatty acid ester, thioether or plasticizer, etc.) and a substance which is eutectic with the organic low-molecular substance. It was shown that the temperature range to be changed can be expanded. Further, Japanese Unexamined Patent Application Publication No.
No. 538 discloses that a recording material in which the content of an organic low-molecular substance in the reversible thermosensitive layer increases from the surface side to the support side is excellent in repeated printing durability. .

[0004] However, with the expansion of the application field of the reversible thermosensitive recording material, a thermal head is often used for clouding and transparency. In such a case, it has become necessary to control the transparency or cloudiness with the energy applied to the thermal head from the so-called static temperature control. In particular, there has been a demand for a reversible thermosensitive recording material which is sensitive to the energy applied to the thermal head in order to shorten the writing time. In addition, the characteristics of the whitening sensitivity by the above thermal head may be changed by a slight difference in the manufacturing conditions even if the same material composition is used, and it is suitable for high-speed printing with the thermal head simply and stably. There has been a demand for a method for producing a reversible thermosensitive recording material.

[0005]

The object of the present invention is to solve the above are those to eliminate the disadvantages, drawbacks, suitable for high-speed printing by the thermal head, provides a method for producing a reversible thermosensitive recording materials having excellent sensitivity It is.

[0006]

This onset bright [Means for solving problem] A solution containing a resin matrix and an organic low-molecular material is coated on a support, in the manufacturing method of the reversible thermosensitive recording material is dried, graded the dried Alternatively, the process is performed by continuously moving from a low temperature to a high temperature.

Hereinafter, the present invention will be described in more detail. The reversible thermosensitive recording material according to the present invention utilizes the change in transparency (transparent state, cloudy opaque state) as described above, and the difference between this transparent state and cloudy opaque state is presumed as follows. That is, in the case of (I) transparent, the particles of the organic low molecular substance dispersed in the resin base material are composed of large particles of the organic low molecular substance, and the light incident from one side is not scattered. (II) In the case of cloudiness, the particles of the organic low-molecular-weight substance are composed of polycrystals in which fine crystals of the organic low-molecular-weight substance are aggregated. This is because light entering from one side is refracted many times at the interface of the crystal of the organic low-molecular-weight material particles because the axes are oriented in various directions, and is scattered and looks white.

In FIG. 1 (representing a change in transparency due to heat), a reversible thermosensitive layer mainly composed of a resin base material and an organic low-molecular substance dispersed in the resin base material has, for example, T ₀ or less. At room temperature, it is cloudy and opaque. This became clear when heated to a temperature T _2, which remains also clear again returned to the normal temperature of T ₀ or less in this state. This may be because the crystalline low-molecular organic material before reaching the T ₀ or less from the temperature T ₂ is between the single crystal from a polycrystalline via a semi-molten state grows. Upon further heating to T ₃ or more temperature becomes translucent state intermediate between the maximum transparency and the maximum opacity. Next, when the temperature is lowered, the state returns to the original cloudy and opaque state without taking the transparent state again. This after low-molecular organic material is melted at a temperature T ₃ or more, presumably because the polycrystals precipitated by being cooled. When the opaque state is heated to a temperature between T _{1 and} T ₂ and then cooled to room temperature, that is, a temperature lower than T ₀ , an intermediate state between transparent and opaque can be obtained. Also, by returning to room temperature After heating to be again T ₃ or more temperature which became clear at the normal temperature, the flow returns to cloudy opaque state again. That is, both opaque and transparent forms at room temperature and intermediate states thereof can be taken. Therefore, by selectively applying heat, the reversible thermosensitive layer can be selectively heated to form a cloudy image on a transparent ground and a transparent image on a cloudy ground, and the change can be repeated many times. is there.

However, as described above, the recording / erasing of the reversible thermosensitive recording material originates from whether or not each domain of the organic low molecular weight substance wrapped in the resin contributes to light scattering. The strength of the cloudy state as a recording material is related to how much of the domain in the reversible thermosensitive layer can be made to scatter light, and the transparent state is to how much can be made to be transparent. I have.

Generally, heating by a thermal head gives a high energy for a very short time, so that a temperature distribution is formed in the heat-sensitive layer of the reversible thermosensitive recording material. The temperature near the surface heated by the thermal head becomes high, and the temperature near the substrate (support) becomes low. Therefore, it is important to control the energy of the thermal head how much the particles in the reversible thermosensitive layer change from transparent to cloudy or from cloudy to transparent in terms of the temperature distribution thus formed.

As described in JP-A-5-8538, a reversible thermosensitive recording material in which the content of an organic low-molecular substance is gradually increased from the surface side to the support side has a low durability. In order to realize such a composition distribution inside the reversible thermosensitive layer, the particle size distribution is such that particles near the surface in the reversible thermosensitive layer (organic low molecular weight material particles) are small and those near the support are large. It is desirable to satisfy to some extent.

[0012] In order to form such a particle size distribution, the drying process is controlled. Depending on the material used and the nature of the solvent, when drying is performed at a constant temperature in a general hot-air dryer, the particle size distribution near the surface and near the support is greatly different, and the particle size distribution is formed. Is done. This is due to the drying process, and drying proceeds from near the evaporation surface of the applied reversible thermosensitive layer forming liquid,
At this time, the layer is sequentially formed from the vicinity of the surface, and the evaporation of the solvent is hindered. Therefore, in general, it is more difficult to dry on the substrate side than on the surface. On the other hand, the formed particles have a relationship that the smaller the drying speed is, the smaller the drying speed is and the smaller the drying speed is, the larger the particles are. Is done.

When comparing large particles and small particles of fatty acids (low-molecular organic substances), it is generally found that the state of the large particles is changed (the transparent state is changed to a cloudy state or vice versa). The energy required is greater than changing small ones. This simply means that the amount of heat required to melt a certain amount of fatty acids is constant, but it takes a longer time to melt a large lump than a small lump of fatty acid. It is thought to be due to.

However, for the above reasons, the distribution of particle diameter generally tends to be small on the surface and large near the substrate, so that the fatty acid particles on the surface to which more energy is heated by the thermal head are given. Both the heating method and the recording material itself arise from the fact that the fatty acid particles in the vicinity of the substrate that are easy to change and give less energy are harder to change. In other words, the thermal head energy suitable for changing the fatty acid particles near the surface is insufficient to change the fatty acid particles near the substrate, and conversely, when the energy sufficient to change the domain near the base material is applied, the thermal head energy near the surface is low. In this case, the energy becomes excessive and the overall transparency and turbidity decrease. Further, the deterioration of the reversible thermosensitive layer may proceed rapidly due to overheating. From this, the fatty acid particles are small near the surface,
The structure that is large near the base is considered to be one factor that hinders high-speed printing by the thermal head.

The inventors of the present invention have made various angles regarding how far the size (average particle diameter) of the organic low molecular weight substance in the reversible thermosensitive layer should be between the vicinity of the surface and the vicinity of the support. As a result of investigations, if the particle size distribution of the organic low-molecular substance in the reversible thermosensitive layer is in the vicinity of the support, if it is set not to exceed 1.5 times the size in the vicinity of the surface, Since the energy required for the transparency and turbidity of the fatty acid particles near the surface and the fatty acid particles near the substrate does not greatly change, it is easy to make the whole evenly transparent or opaque even by the clarification or opacity operation by the thermal head. In addition, it has been confirmed that printing can be performed with lower energy, and that the deterioration becomes slow and advantageous even in repeated printing, thereby completing the present invention.

The manufacturing method of the present onset Ming reversible thermosensitive recording material is achieved by devising the solvent structure, and drying conditions. It is known that when dried at the time of forming the reversible thermosensitive layer, small fatty acid particles are formed by performing fast drying, and large fatty acid particles are obtained by performing slow drying. The drying is also for the progresses gradually to base side progresses from the surface, with the progress of the drying is first formed particles from the surface side, it is gradually formed toward the base side. That is, the fatty acid particles on the surface are formed relatively early in the drying, and the domain on the substrate side can be formed after a certain period of time.

However, when general drying is performed, firstly, since the formed film on the surface hinders the evaporation of the solvent, and the temperature of the liquid film increases in the later stage of drying, the amount of heat transfer decreases. Drying is slowed and the particles on the substrate side become large. For this reason, for example, by increasing the temperature of the hot-air dryer in the later stage of drying, it is possible to speed up the drying in the latter stage, but since the heat transfer efficiency is originally low, the accurate amount of heat transfer can be reduced. There are inconveniences that the control is difficult and that the apparatus is complicated and expensive in order to finely control the heat transfer amount.

The production method of the present invention is efficient because at least part of the drying is performed by heat transfer due to contact with the substrate. The amount of heat transfer can be easily controlled by controlling the temperature of the members in contact with each other or by using members having different heat transfer performances. Further, the structure of the device is simple and the cost is low.

FIGS. 2, 3 and 4 show three embodiments of the method of the present invention. FIG. 2 shows a non-rotating cylindrical heating element 1 having a gradient in the surface temperature in a stepwise or continuous manner, and a support (film) 22 having a reversible thermosensitive layer forming liquid 21 applied to the heating surface. That is, the support 22 is moved so as to be in contact therewith. In FIG. 2, part A on the surface of the cylindrical heating element 1 is, for example, 30 ° C., part B is 80 ° C.
The support 22 coated with a solution (reversible thermosensitive layer forming liquid)
Is, for example, 40 mm / sec.

FIG. 3 shows an example in which a non-rotating cylindrical heating element 3 having a function similar to that of FIG. 2 and having a gradually changing surface temperature is used. here,
The heating section (C ₁ , C ₂ , C ₃ ) is divided into three sections, and a film (coated film) 4 in which a reversible thermosensitive layer forming liquid 21 is applied to a support (film) 22 is in close contact with the transporting film 6. Then, the transfer film 6 is moved while being brought into contact with the cylindrical heating element 3. In FIG. 3A, the temperature of the side surface at the heating portions C ₁ , C ₂ and C ₃ is, for example, as shown in FIG.
(B), as shown in FIG. 3 (c) and FIG. 3 (d), the thickness is adjusted by the degree or thickness of the cloth stuck or in contact with the surface of the heated stainless steel cylinder 1 '.

FIG. 4 shows a long rotating cylindrical heater 5 having a surface temperature gradient gradually or continuously in the axial direction, and a coating film 4 is spirally wound on the surface of the heating device. It is intended to be moved and heated and dried. In the drawing, part A is at 30 ° C., for example, and part D is at 90 ° C., for example.

In the production method of the present invention, there is a method in which at least two or more kinds of organic solvents having different vapor pressures are used when dissolving the two components of the resin base material and the organic low-molecular substance.
Various selections can be made depending on the types of the resin base material and the organic low molecular weight substance, and examples thereof include tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, and benzene.

The resin used as the resin base material of the reversible thermosensitive layer can form a film or sheet and has good transparency.
Mechanically stable resins are preferred. Examples of such a resin include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-acrylate copolymer. Vinylidene chloride-based copolymers such as polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, and vinylidene chloride-acrylonitrile copolymer; polyesters; polyamides; styrene-butadiene copolymers; Polyacrylate or polymethacrylate or acrylate-methacrylate copolymer; silicone resin, and the like. These may be used alone or as a mixture of two or more.

On the other hand, the organic low-molecular substance may be any substance that changes from polycrystal to single crystal by heat in the reversible thermosensitive layer (a substance that changes in the temperature range of T _{1 to} T ₃ shown in FIG. 1). , Generally a melting point of 30-200 ° C, preferably 50-150.
A temperature of about ° C is used. Such organic low molecular weight substances include alkanol; alkane diol; halogen alkanol or halogen alkane diol; alkylamine; alkane; alkene; alkyne; halogen alkane; halogen alkene; halogen alkyne; cycloalkane; cycloalkene; cycloalkyne; Unsaturated mono- or dicarboxylic acids or esters thereof,
Amides or ammonium salts; saturated or unsaturated halogen fatty acids or their esters, amides or ammonium salts; aryl carboxylic acids or their esters, amides or ammonium salts; halogen allyl carboxylic acids or their esters, amides or ammonium salts; thioalcohols Thiocarboxylic acids or their esters;
Amines or ammonium salts; carboxylic acid esters of thioalcohols and the like. These may be used alone or in combination of two or more. The carbon number of these compounds is 1
0-60, preferably 10-38, particularly preferably 10-30. The alcohol group in the ester may be saturated or unsaturated, and may be halogen-substituted. In any case, the organic low molecular weight substance contains at least one kind of oxygen, nitrogen, sulfur and halogen in the molecule, for example,-
OH, -COOH, -CONH-, -COOR, -NH
_{-, - NH 2, -S -} , - S-S -, - O-, it is preferably a compound containing a halogen and the like.

More specifically, these compounds include lauric acid, dodecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, henicosanoic acid, tricosanoic acid, lignoceric acid, pentacosanoic acid, serotinic acid, montanic acid, melicic acid, stearic acid. acid, behenic acid, nonadecanoic acid, alginic acid, higher fatty acids such as oleic acid; methyl stearate, tetradecyl stearate, octadecyl stearate, octadecyl laurate, tetradecyl palmitate, esters of higher fatty acids dodecyl behenate and the like; and the next Ethers such as the compounds shown in Table 1 of
Thioether and the like.

[Table 1] Higher fatty acid in the present invention among, in particular palmitic acid, heneicosanoic acid, tricosanoic acid, lignoceric acid, pentadecanoic acid, nonadecanoic acid, arachidic acid, stearic acid,
Higher fatty acids having 16 or more carbon atoms such as behenic acid are preferred,
Higher fatty acids having 16 to 24 carbon atoms are more preferred.

In order to widen the range of temperatures at which transparency can be achieved, the organic low-molecular substance described in this specification is appropriately combined, or such an organic low-molecular substance is combined with another material having a different melting point. I just need. These are disclosed in, for example, JP-A-63-39378 and JP-A-63-130380, JP-A-1-140109, and Japanese Patent Application No. 2-139.
Although disclosed in the specification such as No. 1363, the present invention is not limited thereto.

The ratio between the organic low-molecular substance and the resin base material in the heat-sensitive layer is preferably about 2: 1 to 1:16 by weight.
1: 2 to 1: 8 are more preferred. When the ratio of the resin base material is less than this, it is difficult to form a film in which the organic low-molecular substance is retained in the resin base material, and when the ratio is more than this, it is difficult to make the film opaque because the amount of the organic low-molecular substance is small. become.

In addition to the above components, additives such as a surfactant and a high-boiling solvent can be added to the heat-sensitive layer in order to facilitate formation of a transparent image. Specific examples of these additives are as follows. Examples of high boiling solvents: tributyl phosphate, tri-2-ethylhexyl phosphate,
Triphenyl phosphate, tricresyl phosphate, butyl oleate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, di-n-octyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, phthalate Dioctyldecyl acid, diisodecyl phthalate, butylbenzyl phthalate, dibutyl adipate, di-n-hexyl adipate, di-2-adipate
Ethylhexyl, di-2-ethylhexyl azelate, dibutyl sebacate, di-2-ethylhexyl sebacate, diethylene glycol dibenzoate, triethylene glycol di-2-ethyl butyrate, methyl acetyl ricinoleate, methyl acetyl ricinoleate, butyl phthalyl Butyl glycolate, tributyl acetyl citrate.

Examples of surfactants and other additives; polyhydric alcohol higher fatty acid ester; polyhydric alcohol higher alkyl ether; polyhydric alcohol higher fatty acid ester, higher alcohol, higher alkylphenol, higher fatty acid higher alkylamine, higher fatty acid amide Lower olefin oxide adducts of fats and oils or polypropylene glycol; acetylene glycol; Na, Ca, Ba or Mg salts of higher alkylbenzene sulfonic acids; higher fatty acids, aromatic carboxylic acids, higher fatty acid sulfonic acids, aromatic sulfonic acids, monoesters of sulfuric acid Or Ca, Ba or Mg salts of phosphoric acid mono- or di-esters; low sulfated oils; poly long chain alkyl acrylates; acrylic oligomers;
Poly long chain alkyl methacrylate; long chain alkyl methacrylate-amine-containing monomer copolymer; styrene-maleic anhydride copolymer; olefin-maleic anhydride copolymer.

The thickness of the heat-sensitive layer is preferably 1 to 30 μm,
2-20 μm is more preferred. When the heat-sensitive layer is too thick, heat distribution in the heat-sensitive layer occurs, and it is difficult to make the heat-sensitive layer transparent uniformly. On the other hand, if the heat-sensitive layer is too thin, the turbidity decreases and the contrast decreases. Further, the turbidity can be increased by increasing the amount of the organic low-molecular substance in the heat-sensitive layer.

As a support of the reversible thermosensitive recording material, a plastic film, a metal plate or the like is used, and it is particularly preferable to use a plastic film.

In the reversible thermosensitive recording material according to the present invention , a light reflecting layer can be provided on the back surface of the thermosensitive layer in order to improve the image contrast. In this case, high contrast can be obtained even if the thickness of the heat-sensitive layer is reduced. To specifically form the light reflection layer, Al, Ni, Sn, Au, Ag
And the like (described in JP-A-64-14079). When the support is made of a material having poor adhesion to a resin, such as an Al vapor-deposited layer, an adhesive layer may be provided between the support and the heat-sensitive layer (JP-A-3-7377). Alternatively, a method of providing low refraction of air or the like between the heat-sensitive layer and the coloring layer or the light reflecting layer may be used to improve the contrast.

Further, a protective layer is provided on the reversible thermosensitive layer according to the present invention in order to prevent the surface from being deformed by the heat and pressure of the heating means by a writing method such as a thermal head and the transparency of the transparent portion being reduced. May be. As the material of the protective layer (0.1 to 10 μm in thickness) laminated on the reversible thermosensitive layer, silicone rubber or silicone resin (Japanese Patent Application Laid-Open No. 63-221087) is used.
And polysiloxane graft polymers (described in JP-A-63-317385) and ultraviolet-curable resins or electron beam-curable resins (described in JP-A-2-566). Furthermore, the surface may be roughened by a method such as adding an inorganic or organic filler to the protective layer in order to prevent dust and dirt from adhering to the thermal head (described in JP-A-4-85077). . In any case, a solvent is used when applying the protective layer forming solution or the like,
It is desirable that the solvent does not easily dissolve the resin of the reversible thermosensitive layer and the organic low-molecular substance. Examples of the solvent that hardly dissolves the resin and the organic low-molecular substance in the reversible thermosensitive layer include n-hexane, methyl alcohol, ethyl alcohol, and isopropyl alcohol. Particularly, an alcohol-based solvent is desirable in terms of cost.

Further, an intermediate layer can be provided between the protective layer and the reversible thermosensitive layer in order to protect the reversible thermosensitive layer from a solvent, a monomer component and the like of the protective layer forming solution (Japanese Patent Laid-Open No. 1-1).
No. 3378). As the material of the intermediate layer, the following thermosetting resins and thermoplastic resins can be used in addition to those listed as the resin base material in the reversible thermosensitive layer. That is, polyethylene, polypropylene, polystyrene, polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin, phenol resin, polycarbonate, polyamide and the like can be mentioned. The thickness of the intermediate layer varies depending on the application, but is preferably about 0.1 to 2 μm. If the thickness is less than this, the protective effect is reduced, and if it is more than this, the heat sensitivity is reduced. It is also possible to provide a magnetic recording layer and use it as a card (Japanese Utility Model Laid-Open No. 2-3876, Japanese Unexamined Patent Application Publication No. 3-1).
No. 30188).

[0035]

Next, the present invention will be described more specifically with reference to examples. All parts and percentages here are on a weight basis.

Example 1 6 parts of behenic acid 4 parts of eicosane diacid 40 parts of vinyl chloride-vinyl acetate copolymer (Denka Vinyl # 1000GK, manufactured by Denki Kagaku Kogyo KK) diisodecyl phthalate on a transparent polyester film having a thickness of about 50 μm A solution consisting of 3 parts, 148 parts of tetrahydrofuran and 49 parts of toluene was applied with a wire bar. Next, the back surface of the coated film is moved at a speed of 40 mm / s while making contact with a cylindrical member as shown in FIG. 2 on a heating surface having a temperature distribution from 30 ° C. to 80 ° C. I let it.
Subsequently, this was heated and dried in a temperature drier maintained at 120 ° C. for 1 minute to evaporate the residual solvent. In this manner, a reversible thermosensitive layer having a thickness of about 15 μm is provided, and further thereon, 10 parts of a 75% butyl acetate solution of a urethane acrylate ultraviolet curable resin (Dainippon Ink Chemical Co., Ltd., Unidick C7-157) isopropyl alcohol A solution consisting of 10 parts was applied with a wire bar, dried in a hot air drier at 100 ° C. for 60 seconds, and then cured with an ultraviolet lamp of 80 w / cm to form a protective layer having a thickness of about 2 μm to prepare a reversible thermosensitive recording material. did.

Example 2 After applying the same heat-sensitive recording layer forming liquid as in Example 1 to a support film, a part of the surface of the cylindrical member kept at 80 ° C. as shown in FIG. ), The surface of which had been adjusted in heat transfer amount was moved at a speed of 40 mm / s while the back surface of the support film was in contact with the film through a film of about 50 μm to form a reversible heat-sensitive layer. Thereafter, a reversible thermosensitive recording material was prepared in the same manner as in Example 1.

Example 3 The same reversible thermosensitive layer forming liquid as in Example 1 was applied to a support film, and then a long rotating member as shown in FIG. The film was moved while being spirally wound with the back surface of the film in contact with the surface of the film having the distribution. At this time, the time from when the support film came into contact with the member until it came out was 40 seconds.
Thereafter, a reversible thermosensitive recording material was prepared in the same manner as in Example 1.

Example 4 A reversible thermosensitive recording material was obtained in the same manner as in Example 1 except that the cylindrical member as shown in FIG. 2 had a temperature distribution from 30 ° C. to 90 ° C.

Example 5 A cylindrical heating element as shown in FIG.
A reversible thermosensitive recording material was produced in the same manner as in Example 1 except that the temperature distribution was given.

Comparative Example 1 The same reversible thermosensitive layer forming liquid as in Example 1 was applied to a support film, and dried with a hot air drier at 100 ° C. for 60 seconds to form a reversible thermosensitive layer. A reversible thermosensitive recording material was prepared.

Comparative Example 2 The same reversible thermosensitive layer forming liquid as in Example 1 was applied to a support film, and the back surface of the film was brought into contact with the surface of a cylindrical member kept at 65 ° C. for 40 seconds to form a reversible thermosensitive layer. did. Thereafter, a reversible thermosensitive recording medium was produced in the same manner as in Example 1.

Comparative Example 3 After applying the same reversible thermosensitive layer forming liquid as in Example 1 to a support film, the back surface of the support film was brought into contact with the surface of the cylindrical member kept at 95 ° C. for 40 seconds, to thereby form the reversible thermosensitive layer. Was formed. Thereafter, a reversible thermosensitive recording medium was produced in the same manner as in Example 1.

Here, a method for measuring the particle size distribution in the reversible thermosensitive layer will be described. First, the sample is cut perpendicular to the layer with a single-edged trim razor. This is immersed in ethanol heated to 60 ° C., and the fatty acid in the cross section is eluted in an ultrasonic cleaner for 7 minutes. Next, this is dried in a vacuum dryer at 40 ° C. for 2 hours. Further, gold is vapor-deposited on this to obtain a sample for a scanning electron microscope. For observation, a scanning electron microscope S-2400 manufactured by Hitachi, Ltd. is used. Observe at an acceleration voltage of 20 KV and a working distance of 15 mm at a magnification of 5,000 and take a photograph. From the photograph, calculate the average particle diameter of each part obtained by dividing the thickness of the reversible thermosensitive layer into four equal parts. The ratio between the particle diameter on the surface side and the particle diameter on the most substrate side is determined.

Each of the prepared reversible thermosensitive recording materials is made transparent at a predetermined temperature in advance, and is made opaque by a thermal head using a printing schlater (manufactured by Yagi Electric Co., Ltd.). The thermal head is a thin film type having an average resistance value of 1420Ω, and the printing conditions are a line cycle of 4 ms, a printing speed of 29 mm / s, and a pulse width of 1 ms. The image density of each part where the head energy is changed is measured. Image density measurement is Macbeth reflection densitometer R
D-914 and printed black at that time (OD =
1.9) is measured with the back side. Thermal energy sensitivity is O.D. The voltage at the point where D = 0.6 is determined. In a cross-sectional photograph taken with a scanning electron microscope, the particles of the example had a relatively uniform particle size from the vicinity of the surface to the vicinity of the substrate, whereas the comparative example had a tendency to be small near the surface and large near the substrate. Is seen. Table 2 shows the above results.

[0046]

[Table 2] * Comparative Example 3 had surface irregularities due to boiling of the solvent during drying, and a uniform film could not be obtained.

[0047]

The reversible thermosensitive recording material obtained according to the present invention has excellent heat sensitivity.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating that the transparency of a reversible thermosensitive layer according to the present invention changes depending on temperature.

FIG. 2 is an explanatory diagram of a method for producing a reversible thermosensitive recording material of the present invention.

FIG. 3 is an explanatory view of another method for producing the reversible thermosensitive recording material of the present invention.

FIG. 4 is an explanatory view of still another method for producing the reversible thermosensitive recording material of the present invention.

[Explanation of symbols]

 1,3,5 Cylindrical heating element 4 Coating film 6 Transport film 21 Reversible thermosensitive layer forming liquid 22 Support (substrate)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-299179 (JP, A) JP-A-5-8538 (JP, A) JP-A-5-85046 (JP, A) JP-A-6-85046 344660 (JP, A) JP-A-6-247044 (JP, A) JP-A-6-106847 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/36

Claims (3)

(57) [Claims] In a method for producing a reversible thermosensitive recording material, a solution containing a resin base material and an organic low-molecular substance is applied on a support and dried, the drying is stepwise or continuously moved from a low temperature to a high temperature. A method for producing a reversible thermosensitive recording material. 2. A method of applying a solution containing a resin base material and an organic low-molecular substance on a support and drying the same to form a heat-sensitive layer, the surface temperature of which is increased stepwise or continuously along the circumferential direction. on the surface of the cylindrical heating body is, method for producing a reversible thermosensitive recording material according to claim 1, wherein by traveling while contacting the support surface coated with the solution to dry the heat-sensitive layer. 3. A method for applying a solution containing a resin base material and an organic low-molecular substance on a support and drying the same to form a heat-sensitive layer by increasing the surface temperature stepwise or continuously along the axial direction. and the surface of the cylindrical heating body long, reversible thermosensitive recording of the solution to be coated was the support surface by traveling along with the rotation of the heating body while wound spirally to dry the heat-sensitive layer according to claim 1, wherein Material manufacturing method.