JPH08187962A - Thermal reversible indication medium and its production - Google Patents

Abstract

PURPOSE: To increase durability for repeat, thermal characteristics and preservation stability by constituting a thermal recording layer of a composite material in which the interpenetrating polymer network of a side chain type polymer liquid crystal and an ultraviolet curing type resin or an electron beam curing type resin is formed. CONSTITUTION: This thermal reversible indication medium consists of a base material 1 and a thermal recording layer 2. The thermal recording layer 2 is constituted of a composite material in which the interpenetrating polymer network(IPN) of a polymer liquid crystal and an ultraviolet curing type resin or an electron beam curing type resin is formed. In the IPN, in order to mutually combine polymer compounds having bad compatibility, a network is formed and micromixing is forcedly performed and morphological control difficult in a simple blending system of the polymer compounds is enabled. The penetration type reversible thermal indication medium is produced by successively laminating the base material 1, the thermal recording layer 2 and a surface protective layer 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a heat-sensitive display medium for displaying and erasing records by controlling the application of heat, which has excellent display quality and can be used as a heat-sensitive paper or OHP sheet which is repeatedly used. The present invention relates to a thermosensitive display medium.

[0002]

2. Description of the Related Art Conventionally, paper has long been used as a medium for displaying and storing information excellent in an interface with humans, and even in the paperless era with the recent progress of OA, its use has been continued. The amount does not decrease,
Rather, it is increasing. This shows that paper has an excellent interface for humans in processing information even in an information-filled era. However, some of the information is used for temporary confirmation,
It contains a lot of transient information that is no longer needed,
Valuable paper resources are wasted because such information is treated and printed in the same manner as information that needs to be stored. In addition, the use of overhead projectors (OHP) and the like has been widely carried out for the transmission of information at recent conferences and academic conferences, and plastic films having toner images formed on polyester films used at that time are not widely used. It is usually not reused. In processing such information, consuming a large amount of paper or plastic is a problem because it wastes resources and deteriorates the environment.

Under such circumstances, a large number of reversible recording display materials which can be recorded and stored on a sheet and which can be repeatedly used have been proposed in various systems. Among these, a heat-sensitive recording method, which enables downsizing of a display device and does not discharge consumables, is drawing attention. As the heat-sensitive recording technique, a system in which a cloudy state and a transparent state are displayed by controlling heat applied to a recording layer in which a low molecular organic compound is dispersed in a high molecular compound base material (JP-A-54-54). 1
No. 19377), a recording layer formed by blending a plurality of polymer compounds is used to display by controlling the phase separation between the polymers by applying heat (JP-A-60-1).
No. 80887), a method of displaying a cloudy state and a transparent state by controlling heat applied to a recording layer made of a high-molecular liquid crystal compound (JP-A-2-117888), and a leuco dye and a color-reducing agent. A method of controlling the heat applied to the recording layer used to develop and decolor (Japanese Patent Laid-Open No. 58-58
No. 191190) is disclosed. Further, a technique of recording and erasing on a recording layer in which a polymer liquid crystal is dispersed in a resin in a granular form by using heat and an electric field (JP-A-3-284).
No. 988) is also known.

[0004]

However, in a reversible thermosensitive display medium having a recording layer comprising a film in which an organic low molecular compound is dispersed in a polymer compound base material and a film in which a plurality of polymers are blended, recording and There is a problem that the mixed components are deteriorated by repeated erasing, the contrast is lowered due to obscuring the boundary between the cloudy state and the transparent state, and the number of times of repetition is limited. Further, the contrast is still insufficient in the color forming / decoloring type reversible thermosensitive recording medium using a leuco dye, and there is a problem in the number of repetitions due to deterioration accompanying the color forming / decoloring reaction. Further, in the reversible display medium using the conventional polymer liquid crystal, the display contrast is low, and there are problems in storage stability of recording and heat-sensitive characteristics. Furthermore, when a display medium having a polymeric liquid crystal as a recording layer is produced, the polymeric liquid crystal is plastic, so that the recording layer surface is not deformed due to heat and printing pressure by the thermal head during recording. There was a problem that the number of repetitions was limited due to the occurrence. Further, in order to prevent the surface deformation of the recording layer by the thermal head, when a surface protective layer having high hardness and high heat resistance is laminated on the recording layer, the recording layer is oriented by the volume shrinkage of the protective layer during the formation of the surface protective layer. There was also the problem of becoming transparent. Therefore, the present invention has been made in view of the above-mentioned problems in the conventional technique. That is, an object of the present invention is to provide a reversible display medium which is excellent in durability against repeated use, heat-sensitive characteristics, display contrast and storage stability. Another object of the present invention is to
It is an object of the present invention to provide a heat-sensitive display medium which has excellent display quality for recording and erasing and can be used repeatedly as a heat-sensitive paper and an OHP sheet.

[0005]

The thermosensitive reversible display medium of the present invention comprises a thermosensitive reversible recording medium having a thermosensitive recording layer formed on a support by controlling heat application to reversibly repeat a transparent state and a cloudy state. In the heat-sensitive recording medium, the heat-sensitive recording layer comprises a side chain type polymer liquid crystal and an ultraviolet curable resin or an electron beam curable resin as an interpenetrating polymer.
And a composite material forming a network. Further, the method for producing a thermosensitive reversible display medium of the present invention comprises a solution of a composition comprising a side chain type polymer liquid crystal and an ultraviolet curable or electron beam curable oligomer or monomer or a mixture thereof on a support. A film is formed by coating, the composition is heated to a temperature at which the composition exhibits liquid crystallinity, cooled, and then irradiated with ultraviolet rays or electron beams to cause a crosslinking reaction of the resin, thereby producing a thermosensitive recording layer. Is formed.

The thermosensitive reversible display medium of the present invention comprises a substrate and a thermosensitive recording layer, and the thermosensitive recording layer comprises
It is composed of a polymer liquid crystal and a composite material in which an interpenetrating polymer network (hereinafter abbreviated as “IPN”) of an ultraviolet curable resin or an electron beam curable resin is formed. Therefore, first, the polymer liquid crystal used in the present invention will be described. As the polymer liquid crystal, a main chain type polymer liquid crystal having a mesogenic group (molecule exhibiting liquid crystallinity) in the main chain and a side chain type polymer liquid crystal in which a mesogenic group is bonded to a side chain are known. In the invention,
A side chain type polymer liquid crystal is used. The side chain type polymer liquid crystal of the present invention is, in addition to the side chain type polymer liquid crystal in which a mesogen group is bonded to the above side chain, a domain size distribution of a multi-domain structure constituting a cloudy state, printing characteristics and storage of records. For the purpose of controlling the thermal properties of polymer liquid crystals that determine temperature,
Further, copolymerization or co-addition of a non-mesogenic compound is also preferably carried out.

Specific examples of the above non-mesogenic compounds include alkyl (meth) acrylate and its derivatives, styrene and its derivatives, (meth) acrylonitrile,
Examples thereof include vinyl chloride, vinylidene chloride, imprene, vinylpyrrolidone, 1-hexene and 1-octene.
In addition, for the purpose of improving the heat resistance and mechanical strength of polymer liquid crystals,
Copolymerization or co-addition of a non-liquid crystal monomer having a hydrogen bonding group is also preferably carried out. Examples of the non-liquid crystal monomer component having such a hydrogen-bonding group include various hydroxyl group, carboxyl group, sulfonic acid group, phosphoric acid group, primary or secondary amino group, acid amide group, thiol group, and the like. Polymerizable monomers can be used. Specific examples thereof include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, and 2- (meth) acryloyloxy. Ethyl succinate, 2- (meth) acryloyloxyethyl phthalate, 2- (meth) acryloyloxyethyl-
2-hydroxyethyl phthalate, 2- (meth) acryloyloxyethyl hexahydrophthalate, 4-
((Meth) acryloxyalkyloxy) -benzoic acid, 2- (meth) acryloyloxyethyl acid phosphate, glyceryl (meth) acrylate, hydroxy-substituted styrene, (meth) acrylic acid, vinyl sulfonic acid, (meth) Typical examples are acrylamide, 2-propen-1-ol, 5-hexen-1-ol and the like. Among these, particularly, a polymerizable monomer having an acidic group such as a carboxyl group, a sulfonic acid group or a phosphoric acid group and a polymerizable monomer having an alcoholic or phenolic hydroxy group can obtain a high hydrogen bonding force. Therefore, it is preferably used. A plurality of types of the above-mentioned non-liquid crystal monomer compounds can be used.

The side chain type polymer liquid crystal can be usually produced by polymerizing a polymerizable mesogenic compound or adding a mesogenic compound capable of addition reaction to a reactive polymer such as hydrogenated polysilicon. . Such techniques are described in Makromol. Chem. , 179, p2
73 (1978), Eur. Polym. J. , 18,
p651 (1982), Mol. Cryst. Liq.
Cryst. , 169, p167 (1989) and the like. The side chain type polymer liquid crystal used in the present invention is
It can be manufactured in the same manner as the above method. The above-mentioned polymerizable mesogen compound and mesogen compound capable of addition reaction include biphenyl-based, phenylbenzoate-based, cyclohexylbenzene-based, azoxybenzene-based, azobenzene-based, azomethine-based, phenylpyrimidine-based, diphenylacetylene-based, biphenylbenzoate-based Typical examples include various compounds in which a acrylate ester, a methacrylate ester group, or a vinyl group is bonded to a rigid molecular structure such as a cyclohexylbiphenyl group or a terphenyl group, preferably through an alkyl spacer having a predetermined length. It can be mentioned as a thing.

Representative structural examples of these compounds are shown below. These are typical structural examples, and the present invention is not limited thereto. _{CH 2 = C (R) -COO-} (CH 2) m -O-A CH 2 = C (R) -COO-A CH 2 = CH- (CH 2) m -O-A ( wherein, R Represents hydrogen or a methyl group, m is 1 to 30
Represents an integer selected from the following, A is the following formula (a) ~
It represents a liquid crystal molecule (mesogenic group) represented by (k). )

[0010]

Embedded image (In the formula, X and Y are each a single bond, -N = N-,-
N (→ O) = N-, -CH = N-, -N = CH-, -C
Represents a group selected from OO-, -C (C = O)-, and -CH = CH- group, R ¹ is an alkoxy group, a halogen atom,
Represents a group selected from a cyano group, a carboxyl group and an alkyl group, n represents an integer selected from 1 to 5,
When n is 2 or more, R ¹ may be different from each other. ) Incidentally, a plurality of types of the above-mentioned mesogenic groups can be used.

The amount of the non-mesogenic compound copolymerized or co-added to the polymer liquid crystal of the present invention is 0.
The range of 1-80 mol% is preferable, and 1 is more preferable.
The range of ˜50 mol% is preferred. When the amount of copolymerization or co-addition is less than 0.1 mol%, the effect of copolymerization or co-addition is difficult to appear, and when it is more than 80 mol%, liquid crystallinity is not exhibited. The copolymerization reaction can take various forms such as random copolymerization, block copolymerization, graft copolymerization and alternating copolymerization. The weight average molecular weight of the polymer liquid crystal is 1,000 to 10
The range of 0,000 is preferable, and the range of 10,000 to 500,000 is particularly preferable.

The thermosensitive recording layer containing the polymer liquid crystal used in the present invention forms a multi-domain structure at room temperature. The multi-domain structure is a structure composed of a large number of minute regions having optical anisotropy, and the mesogenic groups are oriented in substantially the same direction inside one domain. In order to improve the light scattering property, it is desirable that the orientation direction of each domain is random. The size of each domain is preferably about the wavelength of visible light. Specifically, the maximum value of the domain diameter number distribution is 3μ.
m or less, preferably 1 μm or less, more preferably 10
It is in the range of 0 to 600 nm. Further, the difference between the minimum domain diameter and the maximum domain diameter is 3 μm or less, preferably 1 μm.
It is desirable that the thickness is substantially uniform to m or less, more preferably 500 nm or less. Those having a multi-domain structure having such a distribution range have a large white turbidity because they strongly scatter visible light wavelengths.

Next, the composite material forming the IPN of the ultraviolet curable resin or the electron beam curable resin used in the thermosensitive recording layer of the present invention will be described. The above-mentioned IPN, that is, an interpenetrating polymer network, means a state in which the networks of two or more polymer compounds form a structure in which they are intertwined with each other without chemically bonding, It is called an interpenetrating polymer network, an interpenetrating network structure or a multi-network polymer. IPN has an advantage that it is possible to control morphology, which is difficult in a simple blend system of polymer compounds, by forming a mesh and forcibly performing micromixing in order to combine polymer compounds having poor compatibility with each other. In the present invention, by using the reversible thermosensitive recording layer having such an IPN structure, the durability of the recording layer against mechanical stress is improved to prevent the irregular deformation during recording by the thermal head, and further Since it is possible to prevent transparency due to orientation during the formation of the protective layer, it is possible to use a surface protective layer having high hardness and high heat resistance temperature, and it is possible to greatly improve the durability in repetition.

In the method for forming the heat-sensitive recording layer having the above-mentioned IPN structure, the above side chain type polymer liquid crystal and a mixture of an ultraviolet ray curable or electron beam curable resin monomer or oligomer and a polymerization initiator are essential components. The solution containing is applied onto a base material to form a film, which is dried, and then heated to a temperature at which a liquid crystal polymer exhibits a liquid crystal phase, and an opacity is increased by growing a domain diameter by annealing,
Then, irradiation of ultraviolet rays or electron beams causes a crosslinking reaction of the resin to form IPN. As the polymerizable monomer or oligomer capable of forming IPN by irradiation with ultraviolet rays or electron beams, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, trimethylpropane triacrylate, hexanediol-1,6-diene are available. Methacrylate, triethylene glycol diacrylate, tricyclodecane dimethylol diacrylate, polypropylene glycol diacrylate, neopentyl glycol diacrylate, tris (acryloxyethyl)
Mention may be made of isocyanurate or mixtures thereof. The ratio of the above-mentioned ultraviolet curable resin or electron beam curable resin in the heat-sensitive recording layer is preferably in the range of 1 to 20% by weight, more preferably 3 to 10% by weight. If the amount is less than 1% by weight, sufficient repeated durability cannot be exhibited, and if the amount is more than 20% by weight, it is difficult to obtain a sufficient white turbidity.

Various components can be added to the heat-sensitive recording layer of the present invention for the purpose of improving its properties. For example, for the purpose of improving weather resistance, various antioxidants such as hindered amine and hindered phenol may be added, and for the purpose of improving display contrast, anthraquinone-based, styryl-based, azomethine-based, azo-based, etc. Various dichroic dyes may be added. Further, it is also preferable to add various infrared absorbing dyes such as phthalocyanine, squarylium, and azurenium in order to efficiently perform the thermal writing by the semiconductor laser. The addition amount of each of the components listed above is 0.0 in the thermal recording layer.
It is preferably added in the range of 1 to 5% by weight.

Next, a method of recording and erasing the phase change type on the thermosensitive reversible display medium of the present invention will be described. In the present invention, a transparent recording image is formed on the heat-sensitive recording layer in the white turbid state (light scattering state) in the initial stage. This transparent recorded image can be formed by applying heat, an electric field and a magnetic field alone or in combination to control the orientation state and order of the mesogenic groups on the side chains of the polymer. For example, by using a thermal head or a laser beam, a part of the cloudy state of the thermosensitive recording layer containing the polymer liquid crystal is heated to a temperature above the liquid crystal phase-isotropic phase transition temperature so that the polymer liquid crystal becomes transparent (such as It is fixed in the glass state in the isotropic state by converting it to an isotropic state) and then rapidly cooling it. In this state, the arrangement of the mesogenic groups on the side chains is random at the molecular level, so that the mesogenic group is transparent without scattering light. On the other hand, for erasing the recording, after heating the entire reversible thermosensitive display medium to a temperature above the liquid crystal phase-isotropic phase transition temperature using a heat roller or a hot stamp, and then slowly cooling it, the entire thermosensitive recording layer becomes cloudy. And will return to the initial cloudy state. The thermoreversible display medium of the present invention retains the durability of the thermosensitive recording layer even after repeating such recording and erasing 100 times or more.

The structure of the reversible thermosensitive display medium will be described. 1 and 2, 1 is a base material, 2 is a thermal recording layer, 3 is a surface protective layer, and 4 is a light reflecting layer. FIG.
Shows a structural example of a transmissive reversible thermosensitive display medium of the present invention, in which a substrate 1, a thermosensitive recording layer 2 and a surface protective layer 3 are sequentially laminated. FIG. 2 shows an example of the structure of the reflection type reversible thermosensitive display medium of the present invention, in which a substrate 1, a light reflecting layer 4, a thermosensitive recording layer 2 and a surface protective layer 3 are sequentially laminated. is there. As the above base material,
Various polymer films such as polyvinyl chloride, polyester, polypropylene and polyimide, paper, metal, ceramics and glass can be used, but when used as a transmissive reversible thermosensitive display medium, a transparent substrate is particularly preferable. Is preferable, and when used as a reflection type reversible thermosensitive display medium, it is preferable to use a colored substrate or a substrate that reflects light such as metal. Further, when it is used as a reflection type reversible thermosensitive display medium, it is preferable to interpose a light reflecting layer or a light absorbing layer between the substrate and the thermosensitive recording layer which repeats the cloudy state and the transparent state. In particular, when a light-absorbing layer is interposed or when a colored substrate is used, a heat-sensitive recording layer is further provided between the light-absorbing layer or the colored substrate and the heat-sensitive recording layer for the purpose of improving display contrast. It is also preferable to form a layer having a low refractive index. The thickness of the thermal recording layer is in the range of 1 to 50 μm, preferably 3 to 20 μm.
It is selected from the range of m. If the thickness is 1 μm or less, sufficient contrast cannot be obtained, and the thickness is 50 μm.
In the above case, the energy required for recording is increased, and the repeated durability is significantly reduced. As the surface protective layer, one having high heat resistance is desirable, and a fluorine-based polymer, a silicon-based polymer, a thermosetting polymer, an ultraviolet curable polymer, an electron beam curable polymer or the like can be used, and a plurality of protective layers are laminated depending on the purpose. May be. The thickness of the protective layer is
It is preferably selected from the range of 0.1 to 20 μm.

[0018]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto. (Recording / erasing on reversible thermosensitive display medium and evaluation) Aluminum vapor-deposited PET having a film thickness of 100 μm was used as a base material to obtain a reflective display medium. To record an image on a reversible thermosensitive display medium, a thermal head printer thermal recording evaluation device (with a resolution of 8 dots / mm, about 0.3 mJ / do) is used.
recorded at a sensitivity of t). The recorded portion of this image was transparent. On the other hand, this recorded image could be erased by passing it through a heat roller (125 ° C., 2 cm / sec). The reflection optical density (OD value) of the recorded image is X-rite 968 (X-r
(made by ITE Co., Ltd.)
The display medium of A4 size was used to observe the occurrence of defects such as cracks on the surface. The results are shown in each Example and Comparative Example.

Example 1 19 g of 4-acryloxyhexyloxy-4'-cyanobiphenyl as a mesogenic monomer, 1 g of cyclohexyl acrylate as a non-liquid crystalline monomer, and azobisisobutyronitrile (AIB) as a polymerization initiator.
N) 20 mg, tetrahydrofuran as solvent 30 ml
Was used for the polymerization. The obtained polymer solution was purified by repeating precipitation twice with ethyl alcohol as a precipitation solvent, and polymer liquid crystal (weight average molecular weight 50,000: polystyrene conversion by GPC, Tg = 35 ° C., Ti = 105 ° C.)
1.9 g was obtained. An ultraviolet-curing composition containing epoxy acrylate as a main component (trade name: Aronix UV3700, manufactured by Toagosei Co., Ltd.) per 1.0 g of the above-mentioned polymer liquid crystal.
A solution obtained by adding 05 g, 0.01 g of Darocur 1173 (manufactured by Ciba-Geigy Co., Ltd.) as a polymerization initiator, and 3.0 g of methyl ethyl ketone as a solvent was used for aluminum vapor deposition PET.
It was applied onto the film using a blade coater and dried to form a layer containing the polymer liquid crystal composition with a thickness of about 6 μm. Next, this layer is heat-treated at 80 ° C. for 2 minutes, cooled, and then cooled by a high pressure mercury lamp (with a heat ray filter, 50 mW).
A thermosensitive recording layer was formed by curing with. Further, the above ultraviolet curable composition was applied onto the thermosensitive recording layer and cured by using a high pressure mercury lamp to prepare a cloudy reversible thermosensitive display medium in which a surface protective layer having a film thickness of 2 μm was formed. When the obtained reversible thermosensitive display medium was measured using the above-mentioned apparatus, the O. D.
The value is 0.30, and the O.I. D. The value was 1.60. On the other hand, after the recording and erasing were repeated 100 times, the O. D. The value is 0.31 and the O.I.
D. The value was 1.58. From the comparison of these measured values, the display medium after recording and erasing 100 times was
Almost no deterioration was seen from the initial one. Also,
In this case, almost no cracks were observed in the surface protective layer of the A4 size display medium.

Example 2 The polymer liquid crystal synthesized in Example 1 was used, and an ultraviolet curable composition (trade name: Aronix UV37
A reversible thermosensitive display medium was produced in the same manner as in Example 1 except that the amount of the compound (00, manufactured by Toagosei Co., Ltd.) was 0.10 g. When measured in the same manner as in Example 1, the O. D. The value is 0.33, and the O.I. D. The value was 1.58. On the other hand, after the recording and erasing were repeated 100 times, the O. D. The value is 0.34, and the O.I. D. The value was 1.57. From the comparison of these measured values, the display medium after recording and erasing 100 times was hardly deteriorated from the initial one.
Also, in the display medium of A4 size, almost no cracks were observed in the surface protective layer.

Example 3 As the polymer liquid crystal, the one synthesized in Example 1 was used, and an ultraviolet curable composition (trade name: Aronix UV37
A reversible thermosensitive display medium was prepared in the same manner as in Example 1 except that the amount of the compound (00, manufactured by Toagosei Co., Ltd.) was 0.20 g. When measured in the same manner as in Example 1, the O. D. The value is 0.37, and the O.I. D. The value was 1.57. On the other hand, after the recording and erasing were repeated 100 times, the O. D. The value is 0.37, and the O.I. D. The value was 1.56, and almost no deterioration was observed compared to the initial stage. Moreover, cracks in the protective layer were scarcely observed in the display medium of A4 size.

Comparative Example A solution prepared by adding 3.0 g of methyl ethyl ketone as a solvent to 1.0 g of the polymer liquid crystal synthesized in Example 1 was applied on an aluminum vapor-deposited PET film using a blade coater and dried, A layer made of a polymer liquid crystal composition having a film thickness of 6 μm was formed. Next, a reversible heat-sensitive composition in which a surface protective layer having a film thickness of 2 μm was formed by applying an ultraviolet-curing composition (trade name: Aronix UV3700, manufactured by Toagosei Co., Ltd.) on the heat-sensitive recording layer and curing it using a high-pressure mercury lamp. A display medium was produced. When measured in the same manner as in Example 1, the O. D. The value is 0.33, and the O.I. D. The value was 1.60. On the other hand, when recording and erasing were repeated 10 times, cracks were generated in the surface protective layer, and the cracks grew, so that the recording image quality was significantly deteriorated.

[0023]

According to the present invention, since the reversible thermosensitive display medium has a thermosensitive recording layer having an IPN structure, the durability of the thermosensitive recording layer against mechanical stress is improved. Deformation can be prevented. In addition, since it is possible to prevent transparency due to the isotropic polymer liquid crystal when forming the surface protective layer, it is possible to use a surface protective layer having high hardness and a high heat resistance temperature, and therefore, it is possible to significantly improve the durability against repetition. Can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a configuration example showing a reversible thermosensitive display medium of the present invention.

FIG. 2 is a cross-sectional view of a configuration example showing another reversible thermosensitive display medium of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base material, 2 ... Thermal recording layer, 3 ... Surface protective layer, 4 ... Light reflection layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Uematsu 1600 Takematsu, Minamiashigara City, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (6)

[Claims] 1. A thermosensitive reversible display medium having a thermosensitive recording layer on a support, wherein a transparent state and a cloudy state are reversibly repeated by controlling the application of heat, wherein the thermosensitive recording layer is a side chain type. A thermosensitive reversible display medium comprising a polymer liquid crystal and a composite material of an ultraviolet curable resin or an electron beam curable resin forming an interpenetrating polymer network. 2. The thermosensitive reversibility according to claim 1, wherein the interpenetrating polymer network is formed by a crosslinking reaction of an ultraviolet curing type or electron beam curing type oligomer or monomer. Display medium. 3. The thermoreversible display medium according to claim 1, wherein the proportion of the ultraviolet curable resin or the electron beam curable resin in the thermosensitive recording layer is in the range of 1 to 20% by weight. 4. The heat-sensitive reversibility according to claim 1, wherein the side chain type polymer liquid crystal in the heat-sensitive recording layer is a copolymer of at least a liquid crystal group-containing monomer and a non-liquid crystal monomer. Display medium. 5. A thermosensitive reversible display medium according to claim 1, wherein a surface protective layer is formed on the thermosensitive recording layer. 6. A film is formed by applying a solution of a composition comprising a side chain type polymer liquid crystal and an ultraviolet ray curable or electron beam curable oligomer or monomer or a mixture thereof on a support to form a film. The composition is heated to a temperature at which it exhibits liquid crystallinity, cooled, and then irradiated with ultraviolet rays or electron beams to cause a crosslinking reaction of the resin to form a heat-sensitive recording layer, thereby forming a heat-sensitive reversible layer. Of producing a sex display medium.