JPH0618859A - Production of thermosensitive recording medium - Google Patents

Abstract

PURPOSE:To provide the method which can easily produce the thermosensitive recording medium improved in the adhesion between a recording layer contg. a high-molecular liquid crystal and a base or an intervening layer provided thereon. CONSTITUTION:This process for production of the reloadable thermosensitive recording medium which has the recording layer contg. the high-molecular liquid crystal on the base or the intervening layer and forms recording images by heating a part of this recording layer to the recording set temp. of a glass transition point (Tg) or above and cooling the liquid crystalline state generated by this heating to the glass transition point (Tg) or below to solidify this state consists in applying a monomer coating liquid consisting essential of a liquid crystal monomer polymerizable by irradiation with light or electron rays on the base or the intervening layer to form a coating film and irradiating this coating film with the light or electron rays to polymerize the liquid crystal monomer in the coating film, thereby forming the recording layer contg. the high-molecular liquid crystal. The better coatability than with the conventional method using the coating liquid dissolved with the high-molecular liquid crystal is obtd. and the adhesion of the recording layer to the base, etc., is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rewritable heat-sensitive recording medium provided with a recording layer containing a polymer liquid crystal on a support or an intervening layer provided on the support, and particularly to a rewritable thermal recording medium. The present invention relates to a method for easily producing a thermosensitive recording medium having improved adhesion between a recording layer containing a molecular liquid crystal and the support or the intervening layer.

[0002]

2. Description of the Related Art A polymer liquid crystal undergoes reversible phase transition behavior from a solid phase to a liquid crystal phase (glass transition temperature: Tg) and from a liquid crystal phase to an isotropic phase (isotropic phase transition temperature: Tcl) upon application of heat energy. The point that is significantly different from the low-molecular liquid crystal is that it has a glass transition point.

Since it has this glass transition point, it can be fixed by rapidly cooling the liquid crystal state which appears by the temperature rise to below the glass transition temperature (Tg). That is, the immobilization of this liquid crystal state in the solid is nothing but the expression of the memory property.

The rewritable thermosensitive recording medium utilizes the thermal characteristics of the polymer liquid crystal. That is, this type of heat-sensitive recording medium is provided with a recording layer containing a polymer liquid crystal on a support or on an intervening layer such as a light absorbing layer or an underlayer provided on this support, and the above-mentioned recording is carried out if necessary. A protective layer for improving the durability of the recording layer is provided on the layer. The glass transition temperature (Tg) of the polymer liquid crystal is then applied to a part of the recording layer by a thermal printing means such as a thermal printer.
By heating to the above recording set temperature and rapidly cooling the liquid crystal state that appears due to this heating to a temperature below the glass transition temperature (Tg) to fix it, a desired recorded image is formed, while the formed recorded image is erased. Is a means for heating the entire recording layer to a temperature above the isotropic phase transition temperature (Tcl) of the polymer liquid crystal so that the recording layer is in a transparent state.

[0005]

In the heat-sensitive recording medium of this type, conventionally, a polymer (polymer liquid crystal) exhibiting liquid crystallinity is synthesized by heat-polymerizing a monomer, and the polymer liquid crystal is appropriately used as a solvent. After being dissolved to prepare a polymer liquid crystal coating liquid, the coating liquid is applied onto the support or the intervening layer and dried to form a recording layer containing the polymer liquid crystal, and if necessary. It was manufactured by providing a protective layer on this recording layer.

However, in such a conventional method, when the coating liquid is applied to form the recording layer, the polymer liquid crystal in the coating liquid is apt to agglomerate uniformly on the support or the intervening layer. There is a drawback that it is difficult to apply, and there is a problem that the adhesion between the recording layer formed with this and the support or the intervening layer deteriorates.

In this type of heat-sensitive recording medium, the recording layer changes from the solid state to the liquid state every time the rewriting process is performed, and the state repeats again to the solid state. Therefore, the recording layer and the support or the intervening layer are changed. If the adhesiveness with the recording layer is poor, there is a problem that the recording layer is easily peeled off from the support or the like due to the rewriting process and the durability thereof is poor.

The present invention has been made by paying attention to such a problem, and its object is to improve the adhesion between the recording layer containing a polymer liquid crystal and the support or the intervening layer. It is to provide a simple manufacturing method of a thermal recording medium.

[0009]

That is, the invention according to claim 1 comprises a recording layer containing a polymer liquid crystal on a support or on an intervening layer provided on the support, and one of the recording layers is provided. A part is heated to a recording preset temperature above the glass transition temperature (Tg) of the polymer liquid crystal, and the liquid crystal state developed by this heating is cooled below the glass transition temperature (Tg) and fixed to form a recorded image. Based on the premise of the method for producing a rewritable heat-sensitive recording medium in which the entire recording layer is heated to the isotropic phase transition temperature (Tcl) of the polymer liquid crystal or higher to make the recording layer transparent and the recorded image is erased, On the body or on the intervening layer,
A liquid crystal monomer that is radically polymerizable by light irradiation and a monomer coating liquid containing a photopolymerization initiator as a main component are applied to form a coating film, and this coating film is irradiated with light to remove the liquid crystal monomer in the coating film. The above recording layer containing a polymer liquid crystal is formed by polymerization, while the invention according to claim 2 is the rewritable thermosensitive recording medium as described above, which is similar to the invention according to claim 1. On the premise of the production method of 1., a coating film is formed by applying a monomer coating liquid containing a liquid crystal monomer radically polymerizable by electron beam irradiation as a main component on a support or an intervening layer to form a coating film, and The liquid crystal monomer in the coating film is polymerized by irradiating it with an electron beam to form the recording layer containing a polymer liquid crystal.

The invention according to claim 3 is premised on the method for manufacturing a thermosensitive recording medium according to claim 1 or 2.
The liquid crystal monomer is composed of a mixture of a cholesteric monomer and a nematic monomer having a composition ratio of 5 mol% or more and 50 mol 5 or less.

In such technical means, a liquid crystal monomer which can be radically polymerized by light irradiation or electron beam irradiation is a nematic monomer and a collectic monomer having radically polymerizable unsaturated bonds by light or electron beam irradiation. Mixtures can be applied.

As the above nematic monomer,

[Chemical 1] And the like, and as the cholesteric monomer,

[Chemical 2] Etc. can be applied.

The polymer liquid crystal polymerized and formed by irradiation with light or electron beam has a structure in which a nematic monomer polymerized portion and a cholesteric monomer polymerized portion are bonded, and as an example of the nematic monomer polymerized portion, Is in a state where the above chemical formula (1) is polymerized with each other,

[Chemical 3] However, as an example of the cholesteric monomer polymerization part, the above chemical formula (2) is in a state of being polymerized with each other,

[Chemical 4] Is mentioned.

However, in the above chemical formulas (1) to (4), X
Is either -O- or -NH-. Further, in chemical formulas (3) and (4), α and β are integers indicating the degree of polymerization of each monomer.

In the above chemical formulas (1) to (4), R ₁
Is a hydrogen atom or a methyl group, and R ₃ is

[Chemical 5] Or

[Chemical 6] Is.

In the chemical formulas (1) to (4), R ₂ is

[Chemical 7] Or

[Chemical 8] And in the above chemical formula (7), R ₄ is any of a methyl group, an ethyl group, and a propyl group.

Further, the chemical formulas (5) and (7) to (8)
In the above, m and n indicating the number of methylene groups are integers of 1 to 14, preferably 4 to 6.

This polymethylene group-(CH ₂ ) _n -,-
Specific examples of (CH ₂ ) _m − include a methylene group, a dimethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, an octamethylene group, a nonamethylene group, a decamethylene group, an untadecamethylene group,
Examples thereof include a tetradecamethylene group.

In the invention according to claim 1,
The above-mentioned liquid crystal monomer, and 0.1% by weight to 20% by weight, preferably 1% by weight to the total weight of the liquid crystal monomer.
A monomer coating solution was prepared with a photopolymerization initiator added at 10% by weight and a solvent added as necessary, and the monomer coating solution was applied by bar coating, blade coating, air knife coating, gravure coating, roll. After coating on the support or the intervening layer by a coating means such as coating to form a coating film, the liquid crystal monomer in the coating film is radically polymerized by irradiating light such as ultraviolet rays to contain a polymer liquid crystal. The recording layer is formed. As the photopolymerization initiator, any material can be applied as long as it is a substance that generates radicals by light irradiation and induces radical polymerization of liquid crystal monomers.
Examples include the materials shown in the following examples.

Further, in the invention according to claim 2, a monomer coating solution is prepared by using the above-mentioned liquid crystal monomer and a solvent which is added if necessary, and the monomer coating solution is supported by the same coating means as above. After coating on the body or the intervening layer to form a coating film, the coating film is irradiated with an electron beam to radically polymerize liquid crystal monomers in the coating film to form a recording layer containing a polymer liquid crystal. is there.

As described above, in the inventions according to claims 1 and 2, a monomer coating liquid containing a liquid crystal monomer as a main component is used instead of the conventional method using a coating liquid in which a polymer liquid crystal is dissolved. Its coating suitability is improved and a uniform coating film can be formed on the above-mentioned support or intervening layer, and along with this, the adhesion between the support or intervening layer and the recording layer containing the polymer liquid crystal is improved. It has the advantage that it can be improved. Moreover, since the liquid crystal monomer is radically polymerized to generate a polymer liquid crystal only by irradiating the coating film formed by coating with light or an electron beam, the polymer liquid crystal is polymerized by heating and polymerizing the monomer as in the conventional method. There is an advantage that the step of synthesizing in advance can be omitted.

The composition ratio of the liquid crystal monomer is 5 mol%.
When it is composed of a mixture of cholesteric monomer and nematic monomer in an amount of 50 mol% or less, the polymer liquid crystal polymerized by irradiation with light or electron beam is 40
Since the selective reflection ability is provided in the visible region of 0 nm to 700 nm, there is an advantage that color liquid crystal states of various hues can be set depending on the setting of the color development temperature.

Here, examples of the support applicable in the inventions according to claims 1 to 3 include not only paper such as high-quality paper, but also plastic films and sheets such as polyester sheets for prepaid cards. Further, the light absorbing layer formed on the support, if necessary, is an appropriate resin layer in which carbon black or the like is dispersed, and the resin constituting the underlayer or the protective layer is a polyurethane resin or the like.

The recording process using the heat-sensitive recording medium manufactured as described above is performed as follows.

There is a slight difference in the recording operation between the case where the polymer liquid crystal has a selective reflection ability (when it has a chiral component) and the case where it does not have a selective reflection ability. Each of these will be described below.

However, the recording method described below is only one example of the recording method using this thermal recording medium, and a recording method different from the recording method described below using the thermal recording medium to which the above-mentioned polymer liquid crystal is applied. Of course, it is possible to take it.

(1) When the Polymer Liquid Crystal Does Not Have Selective Reflectivity First, the entire recording layer containing the polymer liquid crystal is once heated to an isotropic phase transition temperature (Tcl) or higher to make it transparent, and history information is recorded. After erasing, the liquid crystal is cooled to a temperature below the glass transition temperature (Tg) to fix the polymer liquid crystal in a substantially transparent or cloudy liquid crystal state for an initialization process. The method of setting the liquid crystal state to either substantially transparent or cloudy is as follows.
It can be selectively set by appropriately adjusting a pressure means, for example, by adjusting the pressure when inserting between a pair of heating rollers.

Then, a part of the recording layer of the initialized thermal recording medium is heated by a thermal printing means such as a thermal printer to an appropriate recording set temperature higher than the glass transition temperature (Tg) so as to be in a transparent or cloudy liquid crystal state. Further, this is cooled to a temperature below the glass transition temperature (Tg) to immobilize the polymer liquid crystal in the heated region, and differentiated from the base region which is the unheated region to form a recorded image. In this case, whether the polymer liquid crystal in the heated region is in a transparent or cloudy liquid crystal state is arbitrarily set within a range that can be differentiated from the liquid crystal state in the base region which is the non-heated region. Incidentally, the method of selectively setting the polymer liquid crystal at the heated portion to a transparent or cloudy liquid crystal state is the same as in the case of the above-mentioned initialization processing, and is arbitrarily set by the recording set temperature and the set pressure when pressurizing the recording layer. it can.

On the other hand, in order to erase this recorded image, first the entire recording layer on which this recorded image is formed is heated again to the isotropic phase transition temperature (Tcl) or higher to bring it into a transparent state. It is processed and used for writing again.

(2) When the polymer liquid crystal has selective reflection ability When the above-mentioned polymer liquid crystal has a chiral component, the polymer liquid crystal comes to have selective reflection ability and can form recorded images of various hues. Have advantages.

First, the entire recording layer containing the above-mentioned polymer liquid crystal is once heated to an isotropic phase transition temperature (Tcl) or higher to make it transparent so that history information is erased and the glass transition temperature (T
g) It is cooled below to fix the polymer liquid crystal in a substantially transparent liquid crystal state.

Next, the entire recording layer is heated to a color-developing temperature not lower than the isotropic phase transition temperature (Tcl) and not lower than the glass transition temperature (Tg) to be an appropriate color liquid crystal state. When cooled below (Tg), the liquid crystal state can be fixed by performing the above-mentioned pressure treatment, and the base state of the specific color, that is, the initialization process is performed.

In this case, if the polymer liquid crystal has a selective reflection ability, it is possible to set the color liquid crystal state of various hues due to the difference in the setting of the color development temperature, so that the hue of the base state can be arbitrarily set. Can be set. Therefore, it is possible to form recorded images of various hues by arbitrarily setting the base state, so that there is an advantage that the variation of the recorded images can be expanded.

As in the case of the polymer liquid crystal not having the selective reflection ability, it is natural that the history information erasing process and the initializing process may be performed in one operation.

Then, a part of the recording layer of the initialized thermal recording medium is heated by a thermal printing means such as a thermal printer to a recording set temperature higher than the glass transition temperature (Tg), and the liquid crystal state developed by the heating is heated. By cooling to below the glass transition temperature (Tg) and immobilizing, it is possible to differentiate from the base region which is a non-heated portion and obtain a recorded image. in this case,
By setting the recording set temperature to a temperature higher than the glass transition temperature (Tg) and lower than the isotropic phase transition temperature (Tcl), the liquid crystal color state peculiar to the temperature can be fixed, and the recording set temperature is isotropic. By setting the phase transition temperature (Tcl) or higher, a substantially transparent liquid crystal state can be fixed.

On the other hand, in order to erase the recorded image, first, the entire recording layer on which the recorded image is formed is heated again to the isotropic phase transition temperature (Tcl) or higher to bring it into a transparent state. It is processed and used for writing again.

The image forming or image erasing means according to the present invention is based on heat, and can be carried out by using, for example, a thermal printer, a thermal reflection copying machine, a hot stamper, a thermal roll and the like.

[0038]

According to the invention of claims 1 and 2, instead of the conventional method of applying a coating liquid in which a polymer liquid crystal is dissolved, a monomer coating liquid containing a liquid crystal monomer and a photopolymerization initiator as main components is used. Alternatively, since a monomer coating liquid containing a liquid crystal monomer as a main component is used, its coating suitability is improved and a uniform coating film can be formed on a support or an intervening layer. The adhesion between the recording layer and the recording layer can be improved.

Further, since the polymer liquid crystal is polymerized and formed only by irradiating the coating film containing the liquid crystal monomer with light or an electron beam, the monomer is preliminarily heated and polymerized to synthesize the polymer liquid crystal as in the conventional method. It is also possible to omit the step of performing.

Further, according to the invention of claim 3, the liquid crystal monomer is composed of a mixture of a cholesteric monomer and a nematic monomer having a composition ratio of 5 mol% or more and 50 mol% or less, and is irradiated with light or an electron beam. Since the polymer liquid crystal polymerized and formed has a selective reflection ability in the visible region of 400 nm to 700 nm, it is possible to form recorded images of various hues by changing the cholesteric pitch.

[0041]

EXAMPLES Next, examples of the present invention will be described in detail.

In the examples, the compound 1 represented by the following chemical formula (9) was used as the cholesteric monomer, and the compound 2 represented by the chemical formula (10) and the compound 3 represented by the chemical formula (11) were used as the nematic monomers. Also, as a photopolymerization initiator, the following chemical formula (1
2-Hydroxy-2-methyl-1-phenyl-propan-1-one represented by 2) (trade name Darocure 1173 ..., Compound 4 manufactured by Merck & Co., Inc.) was used.

[0043]

[Chemical 9]

[Chemical 10]

[Chemical 11]

[Chemical 12] Example 1 With respect to 1 part by weight of a liquid crystal monomer, a mixture of 33 mol% of the cholesteric monomer (compound 1) represented by the chemical formula (9) and 67 mol% of the nematic monomer (compound 2) represented by the chemical formula (10) was used. The photopolymerization initiator (compound 4) represented by the above chemical formula (12) was added to 0.1.
05 parts by weight and 10 parts by weight of toluene were added to prepare a monomer coating liquid, and the monomer coating liquid was applied by a Meyer bar onto a support (polyester sheet) on which a light absorbing layer was formed, And it dried and formed the coating film. The monomer coating liquid had better coating suitability than the conventional coating liquid in which the polymer liquid crystal was dissolved, so that a uniform coating film could be easily formed on the light absorbing layer.

Next, the coating film was sufficiently irradiated with ultraviolet rays to polymerize the liquid crystal monomer in the coating film to form a recording layer containing a polymer liquid crystal on the light absorbing layer. A thermal recording medium was manufactured. Since the coating film was uniformly formed on the light absorbing layer, the adhesion between the light absorbing layer and the recording layer containing the polymer liquid crystal was remarkably improved as compared with the conventional case.

The thermal recording medium thus produced was inserted between a pair of heating rollers for 1 second to initialize the thermal recording medium. The temperature of the heating roller is set to a coloring temperature at which the base color tone of the thermosensitive recording medium becomes blue, and the contact thickness is set to 0.1 kg / cm ₂ .

Then, the recording layer of the initialized thermal recording medium is selectively heated using a thermal simulator manufactured by Toshiba to make it transparent, and the heated portion is rapidly cooled to a glass transition temperature (Tg) or lower. Then, the polymer liquid crystal was fixed in a substantially transparent liquid crystal state, and a printed image was obtained by differentiating from the blue base portion which is the non-heated portion.

The thermal recording medium printed to erase the printed image is heated at 130 ° C. for 2 seconds to make it transparent so that the history information is erased and the glass transition temperature (T
g) After being rapidly cooled below to fix the polymer liquid crystal in a transparent liquid crystal state, the above initialization treatment was performed to restore the original recording layer state.

Then, the printing process, the erasing process, and
When the initialization process was repeated, it was confirmed that there was reproducibility and the properties were excellent as a rewritable thermal recording medium.

Further, it was confirmed that the adhesion between the recording layer and the light absorbing layer was good, so that the recording layer was hardly peeled from the light absorbing layer and the rewriting resistance thereof was also good.

Example 2 33 mol% of the cholesteric monomer represented by the chemical formula (9) (Compound 1) and the nematic monomer represented by the chemical formula (11) (Compound 3)
The manufacturing method is substantially the same as that in Example 1 except that a liquid crystal monomer composed of a 67 mol% mixture is applied. However,
Since the configuration of the liquid crystal monomer is changed, the heating condition for erasing the history information after forming the printed image is set to 140.
℃, changed to 2 seconds.

Then, the thermal recording medium thus manufactured was subjected to the same printing, erasing and initializing treatments as in Example 1 to obtain a reproducible and rewritable thermal recording medium. It was confirmed that the characteristics were excellent, and that the repeated rewriting resistance was also good.

Example 3 33 mol% of the cholesteric monomer represented by the chemical formula (9) (Compound 1) and the nematic monomer represented by the chemical formula (10) (Compound 2)
A monomer coating solution was prepared by adding 10 parts by weight of toluene to 1 part by weight of a liquid crystal monomer composed of a 67 mol% mixture, and the monomer coating solution was prepared by a Meyer bar to form a support (polyester). It was coated on a sheet and dried to form a coating film.

Next, the coating film was sufficiently irradiated with an electron beam to polymerize the liquid crystal monomer in the coating film to form a recording layer containing a polymer liquid crystal on the light absorbing layer. Such a thermal recording medium was manufactured.

The thermal recording medium thus produced was inserted between a pair of heating rollers for 1 second to initialize the thermal recording medium. As in Example 1, the temperature of the heating roller is set to a coloring temperature such that the base color tone of the thermosensitive recording medium is blue, and the contact thickness is 0.1.
It is set to kg / cm ₂ .

Then, the recording layer is selectively heated to a transparent state by using a thermal simulator manufactured by Toshiba with respect to the initialized thermal recording medium, and the heated portion is rapidly cooled to the glass transition temperature (Tg) or lower. Then, the polymer liquid crystal was fixed in a substantially transparent liquid crystal state, and a printed image was obtained by differentiating from the blue base portion which is the non-heated portion.

The heat-sensitive recording medium printed to erase the printed image is heated at 130 ° C. for 2 seconds to make it transparent so that the history information is erased and the glass transition temperature (T
g) After being rapidly cooled below to fix the polymer liquid crystal in a transparent liquid crystal state, the above initialization treatment was performed to restore the original recording layer state.

Then, the printing process, the erasing process, and
When the initialization process was repeated, it was confirmed that there was reproducibility and the properties were excellent as a rewritable thermal recording medium.

Further, it was confirmed that the adhesion between the recording layer and the light absorbing layer was good and the recording layer was not easily peeled from the light absorbing layer, and the rewriting resistance thereof was also good.

Example 4 33 mol% of the cholesteric monomer represented by the chemical formula (9) (Compound 1) and the nematic monomer represented by the chemical formula (11) (Compound 3)
The manufacturing method is substantially the same as the manufacturing method according to Example 3 except that a liquid crystal monomer composed of a 67 mol% mixture is applied. However,
Since the configuration of the liquid crystal monomer is changed, the heating condition for erasing the history information after forming the printed image is set to 140.
℃, changed to 2 seconds.

Then, the thermosensitive recording medium thus manufactured was subjected to the same printing, erasing and initializing processes as in Example 3 to obtain a rewritable and rewritable thermal recording medium. It was confirmed that the characteristics were excellent, and that the repeated rewriting resistance was also good.

[0061]

According to the inventions of claims 1 and 2, instead of the conventional method of applying a coating liquid in which a polymer liquid crystal is dissolved,
Since a monomer coating liquid containing a liquid crystal monomer and a photopolymerization initiator as a main component or a monomer coating liquid containing a liquid crystal monomer as a main component is used, its coating suitability is improved and a uniform coating is provided on the support or the intervening layer. A film can be formed and the adhesion between the support or the intervening layer and the recording layer can be improved.

Therefore, peeling of the recording layer from the support or the intervening layer is less likely to occur, so that the thermal recording medium having excellent rewriting resistance can be provided.

Further, the polymer liquid crystal is polymerized and formed only by irradiating the coating film containing the liquid crystal monomer with light or an electron beam, so that the step of preliminarily synthesizing the polymer liquid crystal can be omitted as compared with the conventional method. Has the effect of reducing

According to the third aspect of the invention, since it is possible to form recorded images of various hues by changing the cholesteric pitch, there is an effect that the variations of the recorded images can be expanded.

Claims (3)

[Claims] 1. A recording layer containing a polymer liquid crystal is provided on a support or on an intervening layer provided on this support, and a part of this recording layer is at or above the glass transition temperature (Tg) of the polymer liquid crystal. A recording image is formed by heating to the recording set temperature of (1) and fixing the liquid crystal state developed by this heating to a glass transition temperature (Tg) or less, while the entire recording layer is an isotropic phase of polymer liquid crystal. A method for producing a rewritable heat-sensitive recording medium in which the recording image is erased by heating the recording layer to a transparent state by heating to a transition temperature (Tcl) or higher. Contains a polymer liquid crystal by applying a monomer coating liquid containing a liquid crystal monomer and a photopolymerization initiator as a main component to form a coating film, and irradiating the coating film with light to polymerize the liquid crystal monomer in the coating film. Characterized by forming the above recording layer And a method for manufacturing a thermal recording medium. 2. A recording layer containing a polymer liquid crystal is provided on a support or on an intervening layer provided on this support, and a part of this recording layer is at or above the glass transition temperature (Tg) of the polymer liquid crystal. A recording image is formed by heating to the recording set temperature of (1) and fixing the liquid crystal state developed by this heating to a glass transition temperature (Tg) or less, while the entire recording layer is an isotropic phase of polymer liquid crystal. A method for producing a rewritable heat-sensitive recording medium in which the recording image is erased by heating the recording layer above a transition temperature (Tcl) to produce a rewritable thermosensitive recording medium, wherein radical polymerization can be performed on the support or the intervening layer by electron beam irradiation. Containing a polymer liquid crystal by coating a monomer coating liquid containing a liquid crystal monomer as a main component to form a coating film, and irradiating the coating film with an electron beam to polymerize the liquid crystal monomer in the coating film. Characterized by forming a recording layer Method for manufacturing a thermal recording medium. 3. The thermosensitive recording medium according to claim 1, wherein the liquid crystal monomer is composed of a mixture of a cholesteric monomer and a nematic monomer having a composition ratio of 5 mol% or more and 50 mol% or less. Production method.