JP2701694B2 - Method for producing reversible thermosensitive recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a reversible thermosensitive recording medium capable of recording and erasing information reversibly by heating.

[0002]

2. Description of the Related Art Conventionally, as a recording material capable of recording and erasing information reversibly, many photochromic materials which emit and decolor by irradiation with light, such as a spiropyran compound, have been studied. However, these materials have problems in light and heat stability and durability against repeated use.

On the other hand, as a light-resistant material that can be used repeatedly, it is a system in which organic crystal particles are dispersed in a matrix polymer. There are materials that record and display information in an efficient manner.

A reversible thermosensitive recording material obtained by dispersing the organic crystal particles in a matrix polymer can be recorded and erased by turning into a transparent state and an opaque state by two kinds of heating and cooling processes, respectively. FIG. 2 shows one recording characteristic of the reversible thermosensitive recording medium used in the present invention. After heating to a temperature T ₃ above the temperature, and cooled to T ₀ or less at room temperature, the organic crystal particles of the matrix in the polymer takes a polycrystalline state, the reversible thermosensitive recording medium becomes opaque state. This is because, when the organic crystal particles are in a polycrystalline state, incident light is scattered between the polycrystalline organic crystal particles. After heating to a temperature T _{1 to} T ₂ and then cooling to room temperature below T ₀ , the grain boundaries of the polycrystalline organic crystal particles are dissolved and the reversible thermosensitive recording medium becomes transparent.

On the other hand, as a method for producing a reversible thermosensitive recording material obtained by dispersing such organic crystal particles in a matrix polymer, a coating in which the matrix polymer and the organic crystal particles are dissolved in an organic solvent is applied to a support. However, a method of forming particles in a drying process has been generally used.

[0006]

The method used in the conventional manufacturing method has high transparency / opaque contrast and excellent recording resolution, but dissolves both the matrix polymer and the organic crystal particles. Organic solvent,
Solvents for forming a recording layer providing high contrast recording characteristics are extremely limited, and tetrahydrofuran has been mainly used as a suitable solvent.

However, when a reversible thermosensitive recording material is produced from a coating material using tetrahydrofuran, the stability of the coating material is poor and the odor is severe due to the high volatility of tetrahydrofuran. However, there is a problem that large exhaust equipment is required.

Accordingly, paints using general-purpose organic solvents having low volatility and low odor have been studied. However, almost no coating material capable of completely dissolving the matrix polymer and the organic crystal particles in such a general-purpose organic solvent has been found, and a high-contrast reversible thermosensitive recording material has not been obtained from a general-purpose organic solvent-based coating material. further,
There is also a need to reduce the amount of organic solvent used in the coating in consideration of environmental pollution, and it has been difficult to prepare a coating in which the matrix polymer and the organic crystal particles are completely dissolved.

As described above, in a coating material containing the matrix polymer or the organic crystal particles in an amount equal to or higher than the solubility, a part of the matrix polymer or the organic crystal particles is dispersed in the form of particles. When a reversible thermosensitive recording layer is formed from such a coating material, the dispersion state of the organic crystal particles is deteriorated, for example, the organic crystal particles are aggregated in the reversible thermosensitive recording layer, and the transparency / opaque contrast and the recording resolution are reduced. Such as poor visibility.

Accordingly, the present invention provides a transparent / opaque coating containing a matrix polymer, organic crystal particles, and an organic solvent, wherein at least one of the matrix polymer or the organic crystal particles is contained in a solubility or higher and dispersed in the form of particles. An object of the present invention is to provide a method for producing a reversible thermosensitive recording medium having high contrast and recording resolution and excellent visibility.

[0011]

According to the present invention, there is provided a method for producing a reversible thermosensitive recording medium, comprising a matrix polymer, organic crystal particles and an organic solvent, wherein at least one of the matrix polymer or the organic crystal particles is contained in a solubility or higher. After the application step of applying the coating material dispersed in a shape on a support to form a coating film, contacting the coating film with a solvent-containing material in which at least one of the matrix polymer and the organic crystal particles is soluble. The above object was achieved by performing a drying step after the step.

[0012]

The recording of the reversible thermosensitive recording medium used in the present invention.
The principle of erasure is that the light scattering state changes due to the change in the crystal state of the organic crystal particles. The transparency of this recording layer
The reversibility of the opaque two states depends on the crystallinity of the organic crystal particles and the interaction between the organic crystal particles and the matrix polymer, and the visibility is determined by the thickness of the recording layer, the average particle size of the organic crystal particles, It depends on the dispersion state of the organic crystal particles in the matrix polymer, the difference in the light scattering property of the organic crystal particles between the polycrystalline state and the single crystal state, the transparency of the matrix polymer, and the like.

In particular, the average particle size of the organic crystal particles and the state of dispersion of the organic crystal particles in the matrix polymer greatly affect the transparency / opaque contrast and the recording resolution. That is, when the organic crystal particles are finely dispersed in the matrix polymer with a small particle diameter, the area of the interface between the matrix polymer and the organic crystal particles increases, and the proportion of the organic crystal particles contributing to the opaque state increases. Therefore, it is possible to obtain a reversible thermosensitive recording medium having high transparency / opacity contrast and excellent recording resolution.

In the method for producing a reversible thermosensitive recording medium according to the present invention, a solvent contact step of bringing a coating film into contact with a solvent containing at least one of a matrix polymer and organic crystal particles is performed. Rapidly penetrates into the coating film, and at least one of the matrix polymer and the organic crystal particles is swollen or dissolved by a solvent component in which at least one of the permeated solvent-containing materials is soluble. After passing through the drying step, at least one of the matrix polymer or the organic crystal particles dissolved in the solvent-containing body can cause rearrangement or reprecipitation,
Organic crystal particles are dispersed in fine particles, the dispersion state in the reversible thermosensitive recording layer is improved, and a reversible thermosensitive recording layer with high visibility can be formed.

In other words, in the method for producing a reversible thermosensitive recording medium of the present invention, even if the dispersion state of the organic crystal particles in the coating film is poor, the solvent contact step causes a rearrangement or swelling through a swelling state or a dissolved state. Since the reprecipitation is performed, the dispersion state of the organic crystal particles can be relatively easily improved. As a result, the area of the interface between the matrix polymer and the organic crystal particles is increased, and the recording contrast can be improved, the transparent / opaque contrast is high, the recording resolution is excellent, and the reversible thermosensitive recording is excellent in visibility. The medium can be configured.

Further, since the solubility of the matrix polymer or the organic crystal particles in the solvent-containing substance or the rate of precipitation of the matrix polymer or the organic crystal particles from the solvent-containing substance is different, in the drying step after the solvent contacting step,
When the solvent-containing substance evaporates from the coating film from the swelling state or the dissolved state, voids may be formed between the matrix polymer and the organic crystal particles. In this void portion, since a large difference occurs in the refractive index between the organic crystal particles and the organic crystal particles, the scattered light obtained by irradiating the organic crystal particles in the cloudy state with light becomes more likely to be randomly reflected in the void portions, The scattering is emphasized, and the opacity of the opaque state is improved.

[0017]

FIG. 1 shows a typical configuration example of a reversible thermosensitive recording medium of the present invention. On a support 1, a reversible thermosensitive recording layer 5 composed of a matrix polymer 2, organic crystal particles 3, and a void 4 formed at an interface between the organic crystal particles 3 and the matrix polymer 2, and a protective layer 6 are sequentially laminated. .

As the matrix polymer 2 constituting the reversible thermosensitive recording layer 5 of the present invention, it is necessary that the organic crystal particles 3 are uniformly dispersed and maintained in the form of particles, and that they have a high transparency in a transparent state. Therefore, those having good film forming properties, excellent mechanical properties, and optically transparent properties are preferred.

As such a resin, polyvinyl chloride,
Polyvinyl acetate, polyvinylidene chloride, vinyl chloride / vinyl acetate copolymer resin, vinyl chloride / vinyl acetate / vinyl alcohol copolymer resin, vinyl chloride / vinyl acetate / maleic acid copolymer resin, vinyl chloride / acrylate copolymer resin, chloride Resins containing vinyl chloride as a repeating unit, such as vinyl / vinylidene chloride copolymer resin, vinylidene chloride / acrylonitrile copolymer resin, polyester resin, polyamide resin, polyacryl resin, polymethacryl resin, acryl / methacryl copolymer resin, butyral resin, etc. May be used alone or in combination of two or more.

Among them, vinyl chloride / vinyl acetate copolymer resin, vinyl chloride / partially saponified vinyl acetate copolymer resin, vinyl chloride / vinyl acetate / vinylamine copolymer resin, vinyl chloride / vinyl acetate / vinyl methanolamine copolymer resin, chloride Vinyl / vinyl acetate / vinyl ethanolamine copolymer resin, vinyl chloride / vinyl acetate / maleic acid copolymer resin, vinyl chloride / vinyl acetate / acrylate copolymer resin, vinyl chloride / vinyl acetate / acrylate ester / acrylic acid copolymer A copolymer or polyester resin having a vinyl chloride unit as a main repeating unit, such as a polymer resin, exhibits a preferable interaction with the organic crystal particles and is suitable for the present invention.

The organic crystal particles 3 constituting the reversible thermosensitive recording layer 5 of the present invention are compounds that exhibit the temperature characteristics as shown in FIG. 2 by being dispersed in the matrix polymer 2, and are transparent when selected. Temperature range (T ₁
~ T ₂ ), and the opacity temperature range (T ₃ or more) is selected.

The melting point of the compound of the organic crystal particles 3 is 3
The range is preferably from 0 ° C. to 200 ° C., and preferably from 50 ° C. to 150 ° C. in consideration of the allowance of the reversible thermosensitive recording.

Specific examples of the molecules constituting the organic crystal particles include alkanes, alkenes, alkynes, cycloalkanes, cycloalkenes, hydrocarbon molecules of cycloalkynes, alkylammonium salts, thioalcohols, thiocarboxylic acids or esters thereof, There are amides, ammonium salts, carboxylic acid esters of thioalcohols, and halides of these compounds. Molecules in the above-mentioned melting point range can be appropriately selected and used alone or as a mixture of two or more.

Among them, when a higher aliphatic compound having a hydrogen bonding functional group in the molecule is used for the organic crystal particles 3 of the present invention, the organic crystal particles 3 are visually recognized by the interaction between the hydrogen bonding group and the matrix polymer. It is preferable because the property is improved. That is, for example, -O- group, -OH group, -COOH group, -C
ONH- group, -NH- group, a compound containing a -NH ₂ group or the like, higher aliphatic alcohols, higher fatty acids, higher aliphatic dicarboxylic acids, oxycarboxylic acids, higher resin acid amide. These compounds are also used alone or as a mixture of two or more kinds. The number of carbon atoms of these compounds is 10 to 60, preferably 10 to 38 in consideration of the melting point, and particularly 10 to 38.
~ 30 is desirable.

The composition ratio of the matrix polymer 2 and the compound of the organic crystal particles 3 constituting the reversible thermosensitive recording layer 5 is desirably 0.5: 1 to 20: 1 by weight. When the composition ratio of the matrix polymer 2 is lower than 0.5, the amount of the organic crystal particles 3 increases, and it becomes difficult to form a uniform coating as the reversible thermosensitive recording layer 5. Conversely, matrix polymer 2
When the composition ratio exceeds 20, the amount of the organic crystal particles 3 decreases, making opacity difficult, and lowering the visibility.

As described above, since the voids 4 are formed by the solvent contacting step and the drying step of the manufacturing method of the present invention, the shape of the voids 4 is greatly affected by the material and the conditions of these steps. In the reversible thermosensitive recording medium of the present invention,
Since the presence of the interface between the voids 4 and the organic crystal particles 3 contributes to the improvement in the turbidity of the reversible thermosensitive recording medium, the visibility of the shape of the voids 4 is improved in any case. Particularly, the voids 4 are formed so as to surround the organic crystal particles, rather than being formed at a part of the interface between the matrix polymer and the organic crystal particles,
This is preferable because the area of the interface between the voids 4 and the organic crystal particles 3 becomes larger.

Here, the average void width of the voids 4 is preferably 1 μm or less, because if the average void width becomes large, the interaction between the matrix polymer and the organic crystal particles becomes small, and the visibility of recording deteriorates. Further, as described above, it is preferable that the voids 4 are formed so as to surround the organic crystal particles, since the interface between the voids 4 and the organic crystal particles becomes wider. When dispersed in the form of fine particles having a diameter of several μm or less, with respect to the organic crystal particles per unit volume,
The area of the interface with the gap 4 is increased, which is effective.

In order to improve visibility, it is also possible to form holes independently in the matrix polymer 2. In this case, the contaminant is dispersed in the coating film, and the contaminant is eluted by immersing the coating film in a solvent-containing substance in which the contaminant is soluble, or a nitrogen gas at a specific decomposition temperature,
It can also be formed by a method of mixing a blowing agent that releases carbon dioxide or the like.

The support 1 of the present invention is generally a sheet-like support, and its material is selected in consideration of conditions such as strength and rigidity. Nylon, cellulose acetate resin, polystyrene, polyethylene, polypropylene, polyester A plastic such as polyimide, polycarbonate, polyvinyl chloride or the like can be used alone or in combination. However, as the support 1, polyester or polyvinyl chloride is practical. In addition, paper, nonwoven fabric, or the like can be used as the support 1.

The thickness of the support 1 is appropriately selected in order to maintain the shape as a reversible thermosensitive recording medium or according to the application, and the thickness of the support 1 is 0.05 to 5
It is often used in the order of mm.

Further, an information recording layer such as a magnetic recording layer may be formed on the support 1 by a method other than thermal recording.

The protective layer 6 laminated on the reversible thermosensitive recording layer 5 of the present invention prevents the recording characteristics from being deteriorated due to the contamination of the reversible thermosensitive recording layer 5 from the surrounding atmosphere, and prevents the reversible thermosensitive recording layer 5 from being deteriorated. Since it has the function of improving the mechanical strength, it is formed as needed.

When a thermosetting resin such as an acrylic resin, an epoxy resin, or an unsaturated polyester resin is used as the resin forming the protective layer 6, a high hard coat effect can be obtained. In addition, when an acrylic ultraviolet radiation curable resin is used, it can be easily cured by irradiating ultraviolet rays after coating, and is excellent in transparency.

Next, a method for producing the reversible thermosensitive recording medium of the present invention will be described. In the present invention, the matrix polymer 2
And a coating material containing at least one of the matrix polymer 2 and the organic crystal particles 3 having a solubility or higher and dispersed in the form of particles containing the organic polymer particles 3 and the organic solvent to form a coating film. After the coating step, a drying step is performed after passing through a solvent contacting step in which the coating film is brought into contact with a solvent-containing substance in which at least one of the matrix polymer 2 and the organic crystal particles 3 is soluble, so that reversible heat sensitivity with excellent visibility is achieved. A recording medium can be obtained.

In particular, the solvent contacting step can be performed relatively easily by the following two methods, and the effect of the solvent contacting step is large.

(1-1) A production method in which the solvent contacting step is performed by immersing the coating film in a solvent-containing body that is a liquid in which at least one of the matrix polymer 2 and the organic crystal particles 3 is soluble.

(1-2) A production method in which the solvent contacting step is performed by bringing the coating film into contact with vapor of a solvent-containing substance in which at least one of the matrix polymer 2 and the organic crystal particles 3 is soluble.

In the solvent contact step in the production method (1-1), since the solvent-containing substance dissolves at least one of the matrix polymer 2 and the organic crystal particles 3,
Care must be taken when the immersion time is long, since a part of the coating film may be dissolved. If the coating film is immersed in the solvent-containing body in a short time, the effect of this step will appear without elution of the coating film. Further, a method of spraying a solvent-containing substance onto a coating film is also effective.

Further, it is effective to set the temperature of the solvent-containing body to an appropriate temperature and to carry out the solvent contacting step. This is because by setting the temperature of the solvent-containing body, the hardness of the coating film changes, so the penetration rate of the solvent-containing body into the coating film changes,
This is because the time of the solvent contact step can be controlled. When ultrasonic waves are simultaneously applied to the coating film during the solvent contact step, the solvent-containing substance easily penetrates into the coating film, which is effective. However, care must be taken when the ultrasonic wave is applied too strongly, because the coating film tends to peel off from the support 1.

In the vapor contact step in the production method (1-2), since only the vapor of the solvent-containing substance comes into contact,
A clean reversible thermosensitive recording layer 5 can be obtained without paying attention to elution of the coating film. The solvent contacting step can be easily performed by leaving the coating film in a cover box filled with the vapor of the solvent-containing material, and depending on the temperature in the cover box, the saturated vapor pressure of the solvent-containing material is reduced. And the time required for the solvent contacting step can be adjusted. further,
If the sheet impregnated with the solvent-containing substance is opposed to the coating film with a gap therebetween, the solvent-contacting step can be performed in a relatively short time, and the vapor of the solvent-containing substance is condensed. It can be brought into uniform contact with the surface of the coating film without the need. In this case, by changing the temperature of the sheet impregnated with the solvent-containing material, the evaporation rate of the solvent-containing material from the sheet changes, and the time required for the solvent contact step can be adjusted.

Next, the solvent-containing material used in the present invention is:
The solvent having the above-mentioned properties with respect to each material in the coating film is used as it is alone or as a mixture with another liquid. This solvent-containing material may be a homogeneous solution or a dispersion, but in the case of a dispersion, a colloidal solution is preferred from the viewpoint of dispersion stability.

In the method for producing a reversible thermosensitive recording medium of the present invention, the solvent-containing material used in the solvent contacting step includes:
Any organic solvent can be used as long as the matrix polymer 2 or the organic crystal particles 3 are soluble. However, it is effective if the solvent-containing substance is a good solvent for the matrix polymer 2 or the organic crystal particles 3. .

In particular, for a coating film in which the matrix polymer 2 is made of a copolymer or polyester resin containing vinyl chloride units as a main component, and the organic crystal particles 3 are made of a hydrogen-bonding high-resin compound. , A solvent-containing substance, acetone, methyl acetate, ethyl acetate, tetrahydrofuran,
It is effective to include at least one selected from methylene chloride since it is a good solvent for the matrix polymer 2 or the organic crystal particles 3. Above all, when the solvent-containing substance contains tetrahydrofuran, both the matrix polymer 2 and the organic crystal particles 3 are very well dissolved, which is particularly suitable.

When the solvent contact step is performed, water, alcohol, or the like, which is a poor solvent for the matrix polymer 2 and the organic crystal particles 3, is added to the solvent-containing material, so that the solvent-containing material in the coating film is added. Therefore, the time required for the solvent contact step can be appropriately adjusted.

If the coating containing the matrix polymer 2, the organic crystal particles 3, and the organic solvent further contains an organic solvent which is compatible with the solvent-containing substance in the solvent contact step, it remains in the coating film. The organic solvent is replaced by the solvent-containing substance in the solvent contacting step, so that the solvent-containing substance quickly permeates into the film, and has the effect of shortening the time of the solvent contacting step.

Further, when the coating material contains a high-boiling solvent having a boiling point near the drying temperature in the drying step, the high-boiling solvent tends to remain in the coating film, dissolving or swelling the matrix polymer 2, and In addition to keeping the film uncured, the solvent-containing substance in the solvent contact step quickly mixes with this high boiling point solvent, so that the coated film is quickly replaced with the solvent-containing substance,
The time required for the process is extremely short, which is preferable.

In particular, the high boiling point solvent is
And a good solvent for both the organic crystal particles 3
Of course, the effect of this step is the most efficient.

Since the high boiling point solvent needs to be removed in a drying step after the solvent contacting step, its boiling point is desirably near the drying temperature of the coating film.

In the coating step in the present invention, a coating means such as a gravure coating method, a roll coating method and an air knife method is not particularly selected. In addition, when the coating film is dried in the temporary drying step after the coating of the coating material, the coating film can be easily handled and the next solvent contacting step can be easily performed.

In the drying step of the present invention, the coating film after the solvent contacting step is dried to evaporate the organic solvent and the solvent-containing substance remaining in the coating film.
To form The drying temperature is set in consideration of the boiling point of the organic solvent or the solvent-containing substance, and is usually performed by hot air drying or by bringing the support 1 into contact with a hot plate.

Next, the paint used in the method for producing a reversible thermosensitive recording medium of the present invention will be described. The coating material used in the method for producing a reversible thermosensitive recording medium according to the present invention contains a matrix polymer 2, organic crystal particles 3, and an organic solvent, and contains at least one of the matrix polymer 2 and the organic crystal particles 3 at a solubility or higher. For example, the following two types of paints can be given.

(2-1) A coating material containing organic crystal particles 3 having a solubility or higher in a solution in which the matrix polymer 2 is dissolved in an organic solvent.

(2-2) A coating material containing organic crystal particles having a solubility or higher in an emulsion dispersion obtained by dispersing a matrix polymer swollen or dissolved in an organic solvent in another solvent.

(2-1) is the case where the organic crystal particles 3 are not completely dissolved in a large amount in the organic solvent to be used. Some of the organic crystal particles 3 insoluble in the organic solvent are In the form of particles. The dispersion of the organic crystal particles 3 into fine particles is performed by applying the paint to a pulverizer such as a sand mill, a ball mill, and an attritor.

As the organic solvent to be used, it is desirable to use a general-purpose organic solvent having low volatility and low odor in order to stably perform coating for a long time. In particular, when the matrix polymer 2 is a resin whose repeating unit is mainly composed of a vinyl oxide unit or a resin mainly composed of polyester, and the organic crystal particles 3 are a hydrogen-bonding higher aliphatic compound, alcohol, methyl ethyl ketone, An organic solvent containing one selected from toluene, ethylene glycol ether and the like is suitable.

(2-2) is a coating material in which a matrix polymer and organic crystal particles are dispersed in a solvent. Usually, the matrix polymer is swelled or dissolved in an organic solvent, and this is dispersed in another solvent to form a matrix. An emulsion dispersion of the polymer is made. Organic crystal particles are dispersed in the emulsion dispersion of the matrix polymer, and the resulting dispersion is applied to a pulverizer such as a sand mill, a ball mill, and an attritor to disperse the fine particles to produce a coating material. In this case, in order to disperse the organic crystal particles, a solvent dispersion of the organic crystal particles is prepared in advance, and this is mixed with the emulsion dispersion of the matrix polymer 2, so that the organic crystal particles 3 can be easily dispersed. Can be done.

Next, specific examples of the present invention will be described. (Example 1) A paint was prepared using 533 parts of a mixed solvent in which 100 parts of a vinyl chloride / vinyl acetate copolymer and 33 parts of erucamide were mixed in equal amounts of toluene and methyl ethyl ketone.

Since erucamide was not completely dissolved in a mixed solvent of toluene and methyl ethyl ketone, fine particles were dispersed by a ball mill.

This coating material is applied to a support 1 which is a transparent polyethylene terephthalate sheet having a thickness of 200 μm to perform a coating step, and is dried with hot air at 120 ° C. to form a coating film. , The solvent contacting step was performed by immersing the coating film in tetrahydrofuran. Thereafter, a drying step was performed on a hot plate at 150 ° C. to form a reversible thermosensitive recording layer 5 having a thickness of 10 μm. In the solvent contact step, when the coating film was partially immersed when immersed for 1 minute or more, the immersion time was set to 30 seconds.

Next, an acrylic UV curable resin having a thickness of 3 μm is formed on the reversible thermosensitive recording layer 5 as a protective layer 6 on the reversible thermosensitive recording layer 5 and cured by irradiation with ultraviolet rays as shown in FIG. A reversible thermosensitive recording medium was obtained.

In Examples 2 to 5 and Comparative Examples 1 and 2 described below, the support 1 and the protective layer 6 used were made of the same materials and conditions as in Example 1, respectively. The reversible thermosensitive recording medium was produced by changing the paint and the production conditions as follows.

(Example 2) For a coating film formed from the same paint as in Example 1, tetrahydrofuran / pure water (= 70/3) was used as a solvent-containing material.
The solvent contact step was performed by dipping the coating film in tetrahydrofuran / pure water using the mixed solution of 0). Then 15
A drying step was performed on a hot plate at 0 ° C. to form a reversible thermosensitive recording layer 5 having a thickness of 10 μm. In the solvent contact step, even if immersion was performed for 1 minute or more, the coating film was not dissolved, and the immersion time was set to 2 minutes in this example.

Example 3 The same coating film as in Example 1 was subjected to a solvent contacting step with saturated steam of tetrahydrofuran in a closed vessel at 20 ° C. using tetrahydrofuran as a solvent-containing substance.
A minimum of 3 minutes of contact was required. Thereafter, a drying step was performed on a hot plate at 150 ° C. to form a reversible thermosensitive recording layer 5 having a thickness of 10 μm.

Example 4 The same coating film as in Example 1 was subjected to a solvent contacting step with saturated vapor of ethyl acetate in a closed vessel at 20 ° C. using ethyl acetate as a solvent-containing substance. A minimum of 5 minutes of contact was required. Thereafter, a drying step was performed on a hot plate at 150 ° C. to form a reversible thermosensitive recording layer 5 having a thickness of 10 μm.

Example 5 A paint having a composition of 100 parts of vinyl chloride / vinyl acetate copolymer, 33 parts of erucamide, 467 parts of a mixed solvent of equal amounts of toluene and methyl ethyl ketone, and 66 parts of ethylene glycol monoethyl ether was prepared. did.

In the same manner as in Example 1, fine particles of erucamide were dispersed by a ball mill.

Using this coating material, a reversible thermosensitive recording layer 5 having a thickness of 10 μm was formed in the same manner as in Example 4. The time required for the solvent contact step could be reduced to 3 minutes.

In Examples 1 and 5, the corresponding coating material was applied to the support 1 and a drying step was performed at the corresponding temperature to form a reversible thermosensitive recording layer 5 having a thickness of 10 μm. , 2.

In Examples 1, 2, 3, 4, 5 and Comparative Examples 1 and 2 described above, the clearing temperature range of the reversible thermosensitive recording medium was 75 to 80 ° C.

Each of the reversible thermosensitive recording media produced in each of the examples and comparative examples was made transparent at 80 ° C.
To make it opaque, and use a reflection densitometer (Macbeth densitometer RD
-918), the transparent state and the opaque state of each reversible thermosensitive recording medium were measured as a colorimetric density on a black board as a reference. The results are shown in the following (Table 1).

However, the values measured by the reflection densitometer were such that the reference density of the black board itself as the reference was 1.78, the reflection density of the reference white board itself was 0.05, and The higher the value, the smaller the value, and the higher the transparency, the larger the value.

[0072]

[Table 1]

The cross section of the reversible thermosensitive recording medium of Example 1 and Comparative Example 1 was observed with a scanning electron microscope. In Comparative Example 1, the dispersed organic crystal particles had a particle size of about 3 μm. In Example 1, the particle size of the organic crystal particles was about 1 μm.

In Comparative Example 1, the matrix polymer 2
The voids 4 formed at the interface between the particles and the organic crystal particles 3 were observed only partially, but in Example 1, the void width was about 0.
Many voids 4 of about 1 μm could be observed.

Further, in Example 1 and Comparative Example 1 in the transparent state, a part was made opaque, and the boundary between the transparent part and the opaque part was observed with an optical microscope.
The resolution of Comparative Example 1 was inferior to that of Example 1.

[0076]

According to the present invention, there is provided a coating material comprising a matrix polymer, organic crystal particles and an organic solvent, wherein at least one of the matrix polymer and the organic crystal particles is contained in a solubility or higher and dispersed in the form of particles. After the application step of applying to form a coating film, at least one of the matrix polymer and organic crystal particles through a solvent contacting step of contacting the coating film with a solvent-containing body that is soluble, to perform a drying step Because it is a method for manufacturing a reversible thermosensitive recording medium,
An object of the present invention is to provide an excellent production method that enables production of a reversible thermosensitive recording medium having high transparency / opaque contrast and high recording resolution and excellent visibility.

In particular, since a reversible thermosensitive recording medium having excellent visibility can be produced from a coating containing at least one of the matrix polymer and the organic crystal particles in a solubility or higher, a wide range of organic solvents can be used, By using a paint having low odor and low odor, it is not necessary to provide a large-scale means for preventing volatilization, and it is possible to construct a manufacturing apparatus which is a simple manufacturing apparatus and has less influence of odor on the environment.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a reversible thermosensitive recording medium of the present invention.

FIG. 2 is a diagram showing recording characteristics of a reversible thermosensitive recording medium of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Support 2 Matrix polymer 3 Organic crystal particle 4 Void 5 Reversible thermosensitive recording layer 6 Protective layer

Claims (8)

(57) [Claims] 1. A coating material comprising a matrix polymer, organic crystal particles, and an organic solvent, wherein at least one of the matrix polymer and the organic crystal particles is contained in the organic solvent or more in amount. After a coating step of forming a coating film, at least one of the matrix polymer or the organic crystal particles is subjected to a solvent contacting step of contacting the coating film with a solvent-containing substance that is soluble, and a drying step is performed. A method for producing a reversible thermosensitive recording medium. 2. The method for producing a reversible thermosensitive recording medium according to claim 1, wherein the solvent contacting step comprises immersing the coating film in a solvent containing at least one of the matrix polymer and the organic crystal particles. 3. The method for producing a reversible thermosensitive recording medium according to claim 1, wherein the solvent contacting step comprises contacting the coating film with a vapor of a solvent-containing substance in which at least one of the matrix polymer and the organic crystal particles is soluble. . 4. The method for producing a reversible thermosensitive recording medium according to claim 1, wherein the organic solvent of the coating material is compatible with the solvent contained in the solvent-containing material. 5. The method for producing a reversible thermosensitive recording medium according to claim 4, wherein the organic solvent is a good solvent for the matrix polymer and the organic crystal particles and a high boiling point solvent. 6. An organic coating material comprising a matrix polymer of a resin containing vinyl chloride units as a main component or a resin containing a polyester resin as a main component, and a hydrogen-bonding higher aliphatic compound. 2. The method for producing a reversible thermosensitive recording medium according to claim 1, comprising a crystal particle and an organic solvent. 7. The method for producing a reversible thermosensitive recording medium according to claim 6, wherein the organic solvent contains at least one selected from alcohol, methyl ethyl ketone, toluene and ethylene glycol ether. 8. The matrix polymer is either a resin having a vinyl chloride unit as a main component of a repeating unit or a resin having a polyester resin as a main component, and the organic crystal particles are a hydrogen-bonding higher aliphatic compound. 7. The method for producing a reversible thermosensitive recording medium according to claim 1, wherein the solvent-containing substance contains at least one selected from acetone, methyl acetate, ethyl acetate, tetrahydrofuran, and methylene chloride.