JPH08160380A - Production of optical element - Google Patents

Abstract

PURPOSE: To provide a process for efficiently producing an optical element which consists of high-polymer liquid crystals as a thermosensitive recording layer and is improved in optical characteristics, durability, recording/erasing characteristics, etc., by executing a heat treatment for crosslinking the high- polymer liquid crystals under specific conditions. CONSTITUTION: After a surface protective layer is formed on the high-polymer liquid crystal layer formed on a sheet-like base material, the heat treatment for crosslinking the liquid crystal layer is executed or the heat treatment to crosslink the liquid crystal layer is executed in the state of taking up the sheet- like base material in a roll form in the process for crosslinking the high-polymer liquid crystals under a specific structure. The high-polymer liquid crystal layer is otherwise formed on the sheet-like base material and is subjected to the first heat treatment to control the multidomain structure of the high-polymer liquid crystals and thereafter, the surface protective film is formed on the liquid crystal layer and further, the second heat treatment for crosslinking the high- polymer liquid crystal compsn. is executed or thereafter, the second surface protective film is formed on the first surface protective layer.

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 an optical element having a polymer liquid crystal layer capable of reversibly controlling the light scattering property by an external action.

[0002]

2. Description of the Related Art In recent years, a reversible display recording element capable of reversibly recording and erasing an image has attracted attention, and a reversible display recording element is recorded and erased by using a heating element such as a thermal head. Thermosensitive reversible display recording materials have been developed. As these heat-sensitive recording materials, those using a polymer liquid crystal as a recording layer (JP-A-4-218024) and those using a composite film in which an organic low molecular weight compound is dispersed in a resin base material (special feature) Japanese Laid-Open Patent Publication No. 54-119377), using a leuco dye as a recording layer (JP-A-61-2).
37684) and a polymer film obtained by blending two kinds of polymers as a recording layer (Japanese Patent Laid-Open No. 60-1808).
No. 87) is proposed. Among these techniques, a thermoreversible display recording material using a polymer liquid crystal is particularly preferable because it has excellent optical characteristics and durability.

[0003]

By the way, conventionally, in the production method of forming the recording layer by coating and drying a polymer liquid crystal on a sheet-like substrate such as a film, the optical element has a viewpoint of production efficiency. A production method of applying a recording material to a film wound in a roll from a continuous coating device using a continuous coating device, drying the film, and then rewinding the film in which the recording layer is formed into a roll is adopted. The heat treatment for cross-linking is performed in a state where the film having the recording layer is wound into a roll. However, when the polymer liquid crystal layer is heat-treated in the form of a roll, the adhesiveness is improved by setting the heat treatment temperature at an efficient level, and the polymer liquid crystal layer is brought into contact with the roll of the polymer liquid crystal layer. There is a problem that the polymer liquid crystal layer may be peeled off or the film substrate may be broken or cut when the film having the recording layer formed is pulled out from the roll in the next step. It was Therefore, the present invention has been made in view of the above problems in the conventional technique. That is, an object of the present invention is to provide an optical element having a polymer liquid crystal as a heat-sensitive recording layer, by performing a heat treatment for crosslinking the polymer liquid crystal under specific conditions to obtain optical characteristics, durability and recording / recording properties. Provided is an efficient manufacturing method of an optical element having improved erasing characteristics and the like.

[0004]

The method for producing an optical element according to the present invention comprises cross-linking a polymer liquid crystal under a specific structure, which comprises forming a polymer liquid crystal layer formed on a sheet-like substrate. In order to crosslink the polymer liquid crystal after forming a surface protective layer thereon, heat treatment for crosslinking the polymer liquid crystal layer, or in a state where the sheet-shaped substrate is wound into a roll. Is characterized by performing the heat treatment of. Another method of manufacturing an optical element according to the present invention is to form a polymer liquid crystal layer on a sheet-shaped substrate, and perform the first heat treatment for controlling a multi-domain structure of the polymer liquid crystal, and then perform the polymer liquid crystal layer. Forming a surface protective layer thereon and then performing a second heat treatment for crosslinking the polymer liquid crystal composition, or thereafter forming a second surface protective layer on the first surface protective layer. Characterize. The heat treatment for cross-linking the polymer liquid crystal is preferably performed at a liquid crystal phase-isotropic phase transition temperature of the polymer liquid crystal or lower.

The optical element of the present invention comprises at least three of a sheet-shaped substrate, a recording layer made of a polymer liquid crystal and a surface protective layer.
It consists of two layers. First, the polymer liquid crystal material constituting the recording layer made of the polymer liquid crystal used in the present invention will be described. Generally, as the polymer liquid crystal, a main chain type polymer liquid crystal having a mesogenic group (a molecule exhibiting liquid crystallinity) in the main chain and a side chain type polymer liquid crystal having a mesogenic group bonded to a side chain are known. In the present invention, it is preferable to use a side chain type polymer liquid crystal. Further, in the present invention, as the polymer liquid crystal used for crosslinking, a compound containing a reactive group as one component of the main chain or the side chain is preferably used. In these compounds, the crosslinking can be carried out by utilizing a reactive group and adding a catalyst and a polyfunctional reactive compound, if desired. As the reactive group, a vinyl group, an acrylate group, a methacrylate group, a heterocyclic group such as an epoxy group and an addition or polymerizable group such as an isocyanate group, a hydroxyl group, an amino group, an acid amide group, a thiol group, a carboxyl group , Sulfonic acid group, phosphoric acid group, metal alcoholate group, magnesium halide group (Grignard reagent) and the like are preferable.

Next, a method for producing a polymer liquid crystal will be described. The above-mentioned side chain type polymer liquid crystal can be usually produced by polymerizing a polymerizable mesogenic monomer or by adding a mesogenic compound capable of addition reaction to a reactive polymer such as hydrogenated polysilicone. Such techniques are described in Makromol. Chem. , 179, p2
73 (1978), Eur, Polym. J. , 18,
p651 (1982) and Mol. Cryst. Li
q. Cryst. , 169, p167 (1989) and the like. The polymer liquid crystal used in the present invention can be produced in the same manner as the above method. Examples of the polymerizable mesogenic monomer and mesogenic 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 acrylic acid ester, methacrylic acid ester group and vinyl group are bonded to a rigid molecule (mesogen) such as cyclohexylbiphenyl type and terphenyl type, preferably through an alkyl spacer of a predetermined length. It can be listed as an example.

Representative structural examples of these compounds are shown below. These are typical structural examples, and the present invention is not limited to these. ^{_{CH 2 = C (R a)}} -COO- (CH 2) l -O-A CH 2 = C (R a) -COO-A CH 2 = CH- (CH 2) in _l -O-A (wherein, ( ^Ra represents hydrogen or a methyl group, l represents an integer selected from 1 to 30, and A represents a mesogenic group having the following structure.)

[0008]

Embedded image (In the formula, X and Y are each a single bond, -N = N-,
-N (→ O) = N-, -CH = N-, -N = CH-,-
COO-, -C (C = O)-, represents a group selected from an ethynylene group, R ¹ is an alkoxy group, a halogen atom,
It represents a group selected from a cyano group, a carboxyl group, and an alkyl group, p represents an integer selected from 1 to 5, and when p is 2 or more, each R ¹ may be different. )

The polymer liquid crystal of the present invention can be produced by copolymerizing or co-adding the above-mentioned compound having a reactive group in addition to the above mesogenic compound. As the compound having a reactive group used,
(Meth) acrylic acid, ω-carboxy-polycaprolactone-mono (meth) acrylate, vinyl sulfonate,
Hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2- (meth) acryloxyethyl acid phosphate, 2-hydroxy-3
-Phenoxypropyl (meth) acrylate, 2- (meth) acryloxyethyl succinate, mono (meth) acrylate phthalate, 2- (meth) acryloxyethyl (2-hydroxyethyl) phthalate, 4- (meth)
Acryloxyalkyloxy-benzoic acid,
Glyceryl (meth) acrylate, hydroxy group-substituted styrene, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, glycidyl (meth)
Acrylate, 2-propen-1-ol, 5-hexen-1-ol and the like can be mentioned.

Alternatively, the reactive group may be converted by introducing another reactive group after copolymerizing or co-adding these compounds to the above mesogenic compound. For example, a hydroxyl group introduced by copolymerizing hydroxyethyl (meth) acrylate can be reacted with (meth) acrylic acid or the like to introduce a polymerizable group into a polymer side chain. Further, vinyl acetate can be polymerized and then hydrolyzed to be converted into a hydroxyl group. The example illustrated here is 1
It is an example and is not limited in any way. In order to copolymerize the above compounds with mesogenic monomers or to co-add them to polymer liquid crystals, 0.1 to 70 mol% as a monomer unit is used.
It is preferable to use the above range. The weight average molecular weight of the polymer liquid crystal used in the present invention is in the range of 1,000 to 1,000,000, and particularly preferably 10,000 to 500,000. Also,
In the production of the polymer liquid crystal of the present invention, in addition to the above-mentioned two kinds of mesogenic compounds and compounds having a reactive group, various non-mesogenic compounds can be preferably copolymerized or co-added as the third component. . Examples of the compound that can be used as the third component include alkyl (meth) acrylate and its derivatives, styrene and its derivatives, (meth) acrylonitrile, vinyl chloride, vinylidene chloride, vinylpyrrolidone, 1-hexene and 1-
Octene and the like can be mentioned, and a plurality of types of each compound can be used. Using these compounds
Useful for controlling multi-domain structure and thermal properties.
The copolymerization ratio in the case of using the third component can be variously changed according to the desired characteristics, but the content of the mesogenic monomer is preferably in the range of 40 to 99% by weight, more preferably 60 to 99% by weight. It is a range. Further, these copolymerization reactions can take various known forms such as random copolymerization, graft copolymerization, alternating copolymerization, and are not particularly limited. A polymer liquid crystal having a reactive group is produced as described above, and in the present invention, a crosslinking reaction is performed using these polymer liquid crystals.

Next, it is preferable to use a catalyst and a polyfunctional reactive compound as the reactive compound added to accelerate the crosslinking reaction of the polymer liquid crystal. As the catalyst, it is preferable to use various ultraviolet polymerization initiators, thermal polymerization initiators and the like. As the polyfunctional reactive compound, it is preferable to use a polyfunctional isocyanate compound, a polyfunctional epoxy compound, a polyfunctional melamine compound, a polyfunctional aldehyde compound, a polyfunctional amine compound, a polyfunctional carboxyl compound, or the like. The crosslinking reaction catalyst and the polyfunctional reactive compound are preferably added in the range of 0.01 to 20% by weight with respect to the polymer liquid crystal. This cross-linking reaction is performed by applying heat to the polymer liquid crystal composition to which the various compounds described above are added, but light or electron beam may be applied together with heat.

Further, various components may be added to the above-mentioned polymer liquid crystal composition for the purpose of improving various properties of the polymer liquid crystal. 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 the contrast of recording, anthraquinone-based,
Various dichroic dyes such as styryl type, azomethine type and azo type may be added. Further, various fluorescent dyes may be added for the purpose of improving the light scattering property. Furthermore, in the case of recording using laser light, various laser light absorbing dyes (in the case of using a general semiconductor laser of 780 to 830 nm, near infrared absorbing dyes such as phthalocyanine, squarylium and azurenium can be used) Is preferably added. The various components listed above are preferably added in the range of 0.01 to 5% by weight to the composition containing the polymer liquid crystal. Furthermore, 1 to 2 low molecular weight liquid crystal compounds
It can also be added within the range of 0% by weight.

The polymer liquid crystal composition of the present invention has a multi-domain structure in the temperature range where the composition exhibits a liquid crystal phase. “Multi-domain structure” refers to a structure composed of a plurality of minute regions having different optical properties.
The domains that make up this multi-domain are
It is mainly formed by the difference in the orientation of the side chain liquid crystal molecules inside the domain. That is, inside one domain, liquid crystal molecules are aligned in substantially the same direction, and as a result of the alignment, one domain has optical anisotropy, and it can be optically distinguished from other domains. it can.
The multi-domain structure is an aggregate of domains exhibiting such optical anisotropy, and it is desirable that the orientation direction of each domain is random in order to improve the light scattering property of the polymer liquid crystal. Since this multi-domain structure is used as a light-scattering layer, it is desirable that the size of each domain is an aggregate having a size of about the wavelength of visible light. Specifically, the preferable size of the domain diameter is such that the maximum value of the number distribution of domains is 3 μm or less, preferably 1 μm or less, and more preferably 100 to 600 nm. Also,
Also in the domain diameter distribution range, it is desirable that the difference between the minimum domain diameter and the maximum domain diameter is approximately 3 μm or less, preferably 1 μm or less, and more preferably approximately 500 nm or less. A multi-domain structure having a size and a distribution range in this range is preferable because it strongly scatters the wavelength of visible light and increases the turbidity.

Next, a heat treatment method for controlling the multi-domain structure of the polymer liquid crystal composition of the present invention will be described. The multi-domain structure of the polymer liquid crystal composition can change the size and density of the domain according to the external temperature. That is, the multi-domain structure can be controlled by heat treatment and can be changed to a state having higher optical properties such as light scattering property. This heat treatment method for controlling the multi-domain structure is not limited to heat treatment at a single temperature for a certain period of time, but it is also possible to change the temperature continuously or change the temperature stepwise with time. It is preferably carried out. Specifically, heat treatment can be performed by holding the polymer liquid crystal composition in a constant temperature oven at a predetermined temperature for a predetermined time or controlling the constant temperature oven to change the temperature with time. Further, when the polymer liquid crystal layer is produced by the continuous coating method, hot air of a predetermined temperature is blown by a plurality of dryers (blast dryers) set at different temperatures, or a constant temperature oven provided in the middle of the line is passed. By doing so, heat treatment can also be performed.

As the cross-linking of the polymer liquid crystal composition progresses, the multi-domain structure is almost fixed by the structure before cross-linking, the domain size does not change, and it becomes difficult to control the multi-domain structure. Therefore, in order to improve the optical properties of the polymer liquid crystal composition, a heat treatment for controlling the multi-domain structure is performed before the initiation of the crosslinking reaction, that is, before the heat treatment for crosslinking the polymer liquid crystal composition. Is preferred. The heat treatment for controlling the multi-domain structure may be performed at a temperature at which the movement of the main chain of the polymer compound in the polymer liquid crystal composition becomes active, that is, a temperature range in which the polymer liquid crystal composition exhibits a liquid crystal phase. Most effective.
The temperature range in which the polymer liquid crystal composition exhibits a liquid crystal phase is a temperature range that is equal to or higher than the glass transition point and lower than the liquid crystal phase-isotropic phase transition point, and varies depending on the type of polymer liquid crystal composition used. Is usually 0 to 200 ° C., preferably 20 to 150
It is desirable that the temperature range is ° C. Further, it is preferable to perform the heat treatment at a temperature closer to the isotropic phase transition point because the viscosity is lowered and the multi-domain structure can be controlled at high speed. The multi-domain structure obtained by the above heat treatment can be retained by subjecting it to a heat treatment for crosslinking the polymer liquid crystal composition.
The polymer liquid crystal composition thus obtained is crosslinked to retain the multi-domain structure, whereby the optical properties are stable and the reproducibility is significantly improved even when it is repeatedly used.

Next, the heat treatment for crosslinking the polymer liquid crystal composition of the present invention will be described. The heat treatment method for crosslinking the polymer liquid crystal composition is not only heat treatment at a single temperature for a certain time, but also continuously changing the temperature,
A method of gradually changing the temperature with time can also be adopted. It is desirable that the heat treatment temperature in the initial stage of this heat treatment is less than the liquid crystal phase-isotropic phase transition temperature of the polymer liquid crystal composition to carry out the crosslinking reaction. This is because when the polymer liquid crystal composition is heat-treated at a temperature higher than the liquid crystal phase-isotropic phase transition temperature, the polymer liquid crystal composition undergoes a phase transition to an optically isotropic and uniform state, which is a controlled multi-phase. This is because the domain structure will be destroyed. The liquid crystal phase-isotropic phase transition temperature of the composition varies depending on the composition of the polymer liquid crystal used and the like, but the heat treatment for crosslinking the polymer liquid crystal composition is usually 200 ° C. or lower, preferably 150 ° C. or lower, and further The temperature is preferably 80 ° C. or lower. Also,
At the latter stage of the heat treatment, that is, at the time when the crosslinking is almost completed, it is preferable to complete the crosslinking by performing heat treatment at a temperature of the liquid crystal phase-isotropic phase transition temperature of the polymer liquid crystal composition or higher. The time required for this heat treatment varies depending on the heat treatment temperature and the kind of the polymer liquid crystal composition, but is selected in the range of 1 minute to 300 hours, preferably 1 hour to 48 hours.

The heat treatment temperature for controlling the above multi-domain structure is preferably higher than the heat treatment temperature for crosslinking the polymer liquid crystal composition. When this two-step heat treatment is performed, the heat treatment time for controlling the multi-domain structure is often shorter than the heat treatment time for crosslinking the polymer liquid crystal composition. Also, in general,
The size of the domain changes more at higher temperatures than at lower temperatures. From the above, when the heat treatment temperature for cross-linking is lower than the heat treatment temperature for controlling the domain structure, the domain structure heat-treated and set to a desired size is subjected to heat treatment for cross-linking for a long time. It does not change, and it is possible to obtain one having desired optical characteristics. Thus, in order to improve the optical characteristics of the optical element, the heat treatment temperature for controlling the multi-domain structure needs to be higher than the heat treatment temperature for crosslinking the polymer liquid crystal composition. In the present invention, by adopting the heat treatment method described above,
After forming a polymer liquid crystal composition having a multi-domain structure having a high light-scattering property, the polymer liquid crystal composition is cross-linked to stabilize the multi-domain structure and always show a stable high light-scattering property. An optical element can be obtained.

Next, in the present invention, a sheet-like base material as a support base material for an optical element will be described. As the sheet-shaped substrate, various polymer films such as polyvinyl chloride, polypropylene, polyester (PET, etc.) and polyimide, metal film, paper and the like can be used. Also PE
Colored film and PE in which pigment is dispersed in T film, etc.
It is also preferable to use a film in which a colored layer is provided on a T film or the like, or a vapor-deposited film in which a metal layer having a high reflectance is deposited on the surface of a substrate, and these layers are also used as a light absorbing layer, a colored layer and a light reflecting layer. can do. Furthermore, it is also possible to use a substrate with an electrode as the substrate. Light absorption layer,
The thickness of the coloring layer and the light reflecting layer is 0.001 to 100 μm.
It is selected from the range of m. The polymer liquid crystal layer can be formed on the sheet-shaped substrate by a general method such as a coating method using a solvent and a hot melt coating method. The thickness of the polymer liquid crystal layer is not particularly limited, but is preferably selected from the range of 1 to 100 μm, particularly preferably 2 to 50 μm.

Next, the surface protective layer of the present invention will be described. The properties required for the surface protective layer are abrasion resistance,
In addition to having various properties such as heat resistance, pressure resistance, surface friction and surface lubricity, the adhesiveness is low at the heat treatment temperature for crosslinking the polymer liquid crystal. Materials that meet these conditions include thermosetting resins such as ultraviolet curable resins and electron beam curable resins that have excellent mechanical strength such as pressure resistance, abrasion resistance and heat resistance. UV curable resin and electron beam curable resin form a film by the polymerization reaction of polyfunctional monomers and polyfunctional oligomers,
It is possible to form a tough surface protective layer having high mechanical strength.

Materials used for the surface protective layer of the present invention include polyester acrylate, polyester methacrylate, polyether acrylate, polystyryl methacrylate, polyether methacrylate, urethane acrylate, epoxy acrylate (particularly bisphenol A type, bisphenol F type). , An epoxy acrylate and a phenol novolac type epoxy acrylate each having a bisphenol S type skeleton), a polycarbonate, a polybutadiene acrylate, a silicone acrylate, a melamine acrylate, and the like, which have 1 to 10 functional groups. . In addition, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenoxyethyl acrylate,
Monofunctional monomers and polyfunctional monomers such as 1,6-hexadiol acrylate and tetraethylene glycol diacrylate are also preferred. It is also preferable to mix and use these materials in various combinations.

The surface protective layer can also be formed by laminating a plurality of layers having different compositions. In particular, in the case of a single-layer surface protective layer, it is difficult to simultaneously satisfy the adhesiveness and the lubricity of the surface of the optical element at the interface with the polymer liquid crystal layer. And the first
A plurality of surface protective layers having different functions, such as forming a surface protective layer for the optical element and then forming a second surface protective layer on the surface for the purpose of improving the lubricity of the optical element surface. Is also preferable. Further, since the above resin material has a property of low adhesiveness at the heat treatment temperature for crosslinking the polymer liquid crystal, the glass transition temperature (Tg)
Is preferably higher than the heat treatment temperature, and Tg is 80 ° C.
It is preferable that it is above. The thickness of the surface protective layer varies depending on the material used, but is in the range of 0.1 to 10 μm, preferably 0.2 to 5 μm, and more preferably 1 to 2 μm.

The method for forming the surface protective layer of the present invention includes:
In the case of an ultraviolet curable resin, a mixture of the above oligomer or monomer with a photopolymerization initiator in a proportion of preferably 2 to 5% by weight is dissolved in a solvent or the like on a recording layer made of a polymer liquid crystal composition. A method in which the viscosity is adjusted, the resulting solution is applied, heated if necessary, and cured by irradiating with ultraviolet rays can be applied. In addition, it is also preferable that the surface protective layer is formed into a plurality of surface protective layers by forming second and third surface protective layers on the surface protective layer if necessary.

In the production of the optical element of the present invention, first, the above-mentioned polymer liquid crystal layer is formed on a sheet-like base material which is a supporting base material by using a continuous coating machine or the like, and then a multi-domain structure is controlled. The first-step heat treatment step for next,
After forming a surface protective layer on the polymer liquid crystal layer, a second heat treatment step for crosslinking the polymer liquid crystal layer is performed. After finishing these steps, if necessary, it is possible to further form second and third surface protective layers on the surface protective layer. The heat treatment for cross-linking the polymer liquid crystal layer can improve the production efficiency of the optical element by performing the sheet-shaped substrate on which the polymer liquid crystal layer is formed in a roll shape. In this case, since the surface protective layer is formed on the polymer liquid crystal layer, the surface adhesiveness of the optical element can be reduced. Therefore, even if this optical element is wound in a roll, the surface on which the optical element is superposed adheres strongly to the back surface of the sheet-shaped base material in contact with the upper surface of the base material, and the surface of the base material coated with the polymer liquid crystal layer. The phenomenon of peeling from the surface does not occur. After finishing these steps, if necessary, on the surface protective layer,
Further, it is possible to form second and third surface protective layers. For example, the first surface protective layer is for cross-linking the polymer liquid crystal layer of the second stage to improve the surface releasability during heat treatment, and the second surface protective layer is for the heat resistance of the optical element. Further, by forming the third surface protective layer for improving the abrasion resistance of the optical element, it is possible to improve various characteristics of the optical element.

[0024]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. Example 1 190 g of 4-acryloxyhexyloxy-4'-cyano-biphenyl as a mesogenic monomer and 10 g of 2-hydroxyethyl acrylate as a non-mesogenic monomer having a reactive group, and azobisisobutyro as a polymerization initiator. Polymerization was performed using nitrile (AIBN) and tetrahydrofuran as a solvent. The obtained polymer solution was purified by repeating precipitation three times using ethyl alcohol as a precipitation solvent to obtain 190 g of a polymer liquid crystal represented by the following structural formula (1). The Ti (liquid crystal phase-isotropic phase transition temperature) of the obtained polymer liquid crystal was about 110 ° C.

Embedded image To 20 g of the above-mentioned polymer liquid crystal, 1.0 g of Coronate HX (manufactured by Nippon Polyurethane Co., Ltd.) which is a polyfunctional isocyanate compound as a crosslinking agent, and 60 g of methyl ethyl ketone as a solvent.
The solution added with is vapor-deposited with aluminum P having a thickness of 100 μm
The aluminum coating surface of the ET film is coated with a continuous coating device having a die coater head, and the solvent is dried and removed by using a dryer installed in the coating device, and then the condition is maintained at 85 ° C. for 2 minutes. The first-stage heat treatment for controlling the multi-domain structure was performed to form a polymer liquid crystal layer having a film thickness of about 6 μm with a width of 250 mm and a length of 10 m, and this was wound into a roll. This polymer liquid crystal layer was cloudy. Next, an ultraviolet curable composition (trade name: Aronix UV, manufactured by Toagosei Co., Ltd.) was applied as a surface protective layer using the above continuous coating device, and cured by irradiation with a metal halide lamp to give a film thickness of about 1 μm.
The surface protective layer of was formed on the polymer liquid crystal layer, and this was wound again into a roll shape. Then, as a second-stage heat treatment for crosslinking the polymer liquid crystal composition, reaction was carried out in an oven at 50 ° C. for 24 hours to perform crosslinking to produce an optical element.
After the heat treatment in the second stage, the film was pulled out from the roll form, but neither adhesion between the films nor offset to the back surface of the film occurred.

Example 2 After the first-stage heat treatment, a surface protective layer having a thickness of about 1 μm was formed on the polymer liquid crystal layer by using soluble nylon (trade name: CM4000, manufactured by Toray) as a material for the surface protective layer. Then
After the second stage heat treatment, an ultraviolet curable composition (trade name: Aronix UV, manufactured by Toagosei Co., Ltd.) is applied as a second surface protective layer on the surface of the soluble nylon surface protective layer and cured by irradiation with a metal halide lamp. Due to
An optical element was produced in the same manner as in Example 1 except that the second surface protective layer having a film thickness of about 1 μm was formed. In this case, the offset did not occur as in the case of Example 1.

Comparative Example 1 A polymer liquid crystal layer was formed in the same manner as in Example 1, heat treatment for controlling the multi-domain structure in the first step was performed, and this was wound into a roll to form a surface protective layer. The second stage heat treatment was performed without performing the above. After the second stage heat treatment for crosslinking the polymer liquid crystal composition, when the sheet was tried to be pulled out from the roll form, the films adhered to each other, and the polymer liquid crystal layer was detached and the film wrinkles occurred.

Example 3 A polymer liquid crystal layer was formed in the same manner as in Example 1, and the surface protective layer was formed by winding the polymer liquid crystal layer into a roll without heat treatment for controlling the multi-domain structure in the first step. Then, only the second stage heat treatment for crosslinking the polymer liquid crystal composition was performed. When the sheet was pulled out from the roll form, adhesion between the films and offset to the back surface of the film did not occur.

Example 4 The same as Example 1 except that the heat treatment for controlling the multi-domain structure of the first step was performed at a temperature of 30 ° C. and the heat treatment of the first step was lower than that of the second step. An optical element was produced. When the sheet was pulled out from the roll form, adhesion between the films and offset to the back surface of the film did not occur.

Example 5 The same procedure as in Example 1 was carried out except that the first step of heat treatment for controlling the multi-domain structure was carried out at a liquid crystal phase-isotropic phase transition temperature of the polymer liquid crystal of 130 ° C. or higher. A device was produced. The sheet was pulled out from the roll form, but neither adhesion between the films nor offset to the back surface of the film occurred.

The optical elements produced in the above examples and comparative examples were evaluated. (Offset performance) The state of the offset was measured by measuring the area of the liquid crystal layer attached to the back surface of the film when the obtained roll-shaped optical element was pulled out, and when the attached area was zero, it was determined that the offset did not occur. . From the results of comparison between Example 1 and Example 2 and Comparative Example 1, the optical element obtained by the manufacturing method of the present invention does not cause an offset, so that the production efficiency of the optical element is very high and the separation of the polymer liquid crystal is high. It was found that an optical element having a uniform film thickness with no defect can be manufactured. (Reproducibility of Light Scattering Control) In order to record information on an optical element, a thermal printer was used to provide a region (transparent state) with a small light scattering property. Further, the information was erased by returning to a state with a large light scattering property (light scattering state) using a heat roller set at 130 ° C. Regarding the optical element, the optical density immediately after fabrication and the reflection optical density in the cloudy state after recording / erasing 100 times are respectively X-rite 404 (X-rite).
(Manufactured by the company). Table 1 shows the results.

[0031]

[Table 1]

The following can be understood from the results of each of the above Examples, Comparative Examples and Table 1. That is, in the optical elements obtained in Examples 1 and 2, the surface protective layer was formed on the polymer liquid crystal layer as compared with the optical elements obtained in Comparative Example 1, and therefore the polymer liquid crystal compositions were cross-linked. Even if the heat treatment is performed in a roll state, there is an advantage that production can be efficiently performed without causing problems such as adhesion. In addition, in the examples, it is preferable to perform the heat treatment in two stages rather than in one stage because the optical density is lower and the white turbidity is more excellent (from the comparison between Examples 1 and 3). ). Further, it is preferable to set the heat treatment temperature of the first step higher than the heat treatment temperature of the second step because the white turbidity becomes more excellent (Examples 1 and 4).
From the comparison with). Further, it is preferable that the heat treatment temperature of the first step for controlling the multi-domain structure is performed within the temperature range in which the polymer liquid crystal composition shows the liquid crystal layer, because the white turbidity is more excellent (Example 1). (From the comparison with 5). Further, when the surface protective layer surface of the samples of Examples 1 and 2 after recording / erasing was repeated 100 times was observed under a microscope, Example 1 showed several cracks having a width of about 5 μm and a length of about 50 μm. In contrast to Example 2, no surface scratch was observed in Example 2. From the result, it can be seen that the strength of the surface protective layer is increased by stacking a plurality of surface layers.

[0033]

INDUSTRIAL APPLICABILITY According to the present invention, the surface of an optical element obtained by heat treatment for cross-linking the polymer liquid crystal in a state where a surface protective layer is formed on the surface of the polymer liquid crystal layer has no adhesiveness. Since it is suppressed, it is possible to prevent the phenomenon of adhering to the sheet-like base material such as the film in contact even if the heat treatment is performed in the form of being wound into a roll, thus improving the production efficiency of the optical element. be able to. Further, prior to cross-linking the polymer liquid crystal layer, a heat treatment for controlling the crystal structure is performed to produce an optical element exhibiting stable and high light stability and having improved durability and recording / erasing characteristics. The obtained optical element can be applied as a light control element, an optical recording medium, an optical modulation element and a reversible display recording element.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G02F 1/1333 G11B 7/26 7215-5D (72) Inventor Takashi Uematsu 1600 Takematsu, Minamiashigara City, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (7)

[Claims] 1. A method for producing an optical element, which comprises forming a surface protective layer on a polymer liquid crystal layer formed on a sheet-shaped substrate and then performing heat treatment for crosslinking the polymer liquid crystal layer. . 2. A polymer liquid crystal layer formed on a sheet-shaped substrate, a surface protective layer formed on the sheet-shaped substrate, and then crosslinked the polymer liquid crystal in a state where the sheet-shaped substrate is wound into a roll. A method for manufacturing an optical element, characterized in that the heat treatment is performed. 3. A polymer liquid crystal layer is formed on a sheet-shaped substrate, and after a first heat treatment for controlling the multi-domain structure of the polymer liquid crystal, a surface protective layer is formed on the polymer liquid crystal layer.
A method of manufacturing an optical element, which further comprises performing a second heat treatment for crosslinking the polymer liquid crystal composition. 4. The method for manufacturing an optical element according to claim 3, wherein the heat treatment temperature for controlling the multi-domain structure is higher than the heat treatment temperature for crosslinking the polymer liquid crystal composition. 5. The optical element according to claim 1, 2 or 3, wherein the heat treatment for cross-linking the polymer liquid crystal layer is performed at a liquid crystal phase-isotropic phase transition temperature of the polymer liquid crystal or lower. Manufacturing method. 6. The optical element according to claim 1, wherein the polymer liquid crystal layer comprises a composition containing a polymer liquid crystal containing a mesogenic monomer unit and a non-mesogenic monomer unit. Production method. 7. A polymer liquid crystal layer is formed on a sheet-shaped substrate, a first heat treatment for controlling a multi-domain structure of the polymer liquid crystal is performed, and a first surface protective layer is formed on the polymer liquid crystal layer. After the formation, a second heat treatment for cross-linking the polymer liquid crystal layer is performed, and then a second surface protection layer is formed on the first surface protection layer, which is a process for producing an optical element. Method.