JP2010002664A - Optical modulation element, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical modulation element capable of enhancing a strength of a light modulating layer without degrading display characteristics, and to provide a method for manufacturing the same. <P>SOLUTION: The optical modulation element has: a pair of substrates at least one of which has translucency, arranged to face electrodes provided on surfaces; and the light modulating layer provided between the paired substrates, and containing at least a liquid crystal drop or a liquid crystal microcapsule, a polymer binder, and a resin spacer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light modulation element and a method for manufacturing the same.

Consumption of a large amount of paper, especially in offices, has become a problem due to destruction of forest resources, which are raw materials for paper pulp, waste disposal, and environmental pollution caused by incineration. However, with the spread of personal computers and the development of the information society such as the Internet, the consumption of paper as a so-called short-lived document for the purpose of temporary browsing of electronic information tends to increase more and more. It is desired to realize a rewritable display medium that can replace the above.
By the way, the cholesteric light modulation element has a memory property that can hold a display with no power supply, a bright display can be obtained because a polarizing plate is not used, and a color display can be performed without using a color filter. That has attracted attention in recent years.

Cholesteric liquid crystals with liquid crystal molecules having a helical structure divide incident light into right and left circularly polarized light, and perform a selective reflection phenomenon that causes Bragg reflection of the circularly polarized light component that matches the twist direction of the spiral and transmits the remaining light. Wake up. The central wavelength λ of reflected light and the reflected wavelength width Δλ are expressed as λ = n · p and Δλ = Δn · p, respectively, where the helical pitch is p, the average refractive index is n, and the birefringence is Δn. The reflected light from the liquid crystal layer exhibits a vivid color depending on the helical pitch.
As shown in FIG. 9A, the cholesteric liquid crystal having positive dielectric anisotropy is in a planar state in which the helical axis is perpendicular to the cell surface and causes the selective reflection phenomenon described above with respect to incident light. As shown in FIG. 9B, the helical axis is almost parallel to the cell surface and the incident light is transmitted while being slightly scattered forward, and as shown in FIG. Shows three states: a homeotropic state in which the direction of the electric field is directed and the incident light is almost completely transmitted.

  Of the above three states, the planar state and the focal conic state can exist bistable without voltage. Therefore, the alignment state of the cholesteric liquid crystal is not uniquely determined with respect to the voltage applied to the liquid crystal layer. When the planar state is the initial state, the planar state, the focal conic state, When the focal conic state is the initial state, the focal conic state and the homeotropic state are changed in this order as the applied voltage increases. On the other hand, when the voltage applied to the liquid crystal layer is rapidly reduced to zero, the planar state and the focal conic state are maintained as they are, and the homeotropic state is changed to the planar state. Then, the three states can be shifted to each other depending on the magnitude of the applied pulse voltage.

This electro-optic response is shown in FIG. In FIG. 10, a curve A shows a case where the initial state is a planar state, and a curve B shows a case where the initial state is a focal conic state.
In FIG. 10, the region indicated by (a) is a planar state or focal conic state (selective reflection state or transmission state), the region indicated by (b) is a transition region, and the region indicated by (c) is a focal conic state (transmission state). ), A region indicated by (d) indicates a transition region, a region indicated by (e) indicates a homeotropic state, and when the voltage is set to 0 in the homeotropic state, the region changes to a planar state (selective reflection state). In addition, Vpf, 90, Vpf, 10, Vfh, 10, Vh, 90 are voltages at which the normalized reflectance is 90 or 10 before and after the two transition regions (the normalized reflectance is 90 or more). It means a selective reflection state and 10 or less is a transmission state).

  A reflective memory display using the planar state and the focal conic state can be realized by disposing at least a layer that absorbs light having the same wavelength as the selective reflection color on the back surface of the cholesteric liquid crystal layer.

  Cholesteric light modulators have a structure in which liquid crystal is encapsulated as a continuous phase between a pair of supporting substrates, PDLC (Polymer Dispersed Liquid Crystal) in which cholesteric liquid crystal is dispersed in a polymer binder in the form of drops, A display method called PDMLC (Polymer Dispersed Microencapsulated Liquid Crystal) in which liquid crystal microencapsulated liquid crystal is dispersed is known (for example, see Patent Documents 1 to 3 below).

  In order to suppress such a decrease in reflectance and saturation, a liquid crystal display element in which adjacent liquid crystal drops are brought into close contact with each other and the liquid crystal drops have a polyhedral structure is known (for example, see Patent Document 4).

Also disclosed is a method for producing a liquid crystal display element, in which a liquid crystal drop or liquid crystal microcapsule dispersed in a solution containing gelatin and a solvent is coated with a light control layer coating liquid, and the solvent in the light control layer is dried. (For example, refer to Patent Document 5).
Japanese Patent Publication No. 7-009512 Japanese Patent Laid-Open No. 9-236791 Japanese Patent No. 3178530 Japanese Patent Laid-Open No. 9-236791 JP 2005-258310 A

However, the cholesteric light modulators with PDLC structure and PDMLC structure have a problem that the brightness and color purity of the selective reflection color in the planar state is low and a beautiful color display cannot be performed, and the light transmittance in the focal conic state. However, for example, in a display element in which a black light absorption layer is provided on the back surface, there is a problem that black display becomes cloudy and the contrast becomes low.
Further, the PDLC structure having a high liquid crystal ratio in the light control layer is insufficient in strength, and the display characteristics may be deteriorated due to external pressing or the like. On the other hand, in a method in which spacers such as general ribs are provided in advance, display defects such as moire may occur due to the regular arrangement of ribs.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a light modulation element in which the intensity of the light control layer is increased without deteriorating display characteristics, and a method for manufacturing the light modulation element. It is.

The above-mentioned subject is achieved by the following present invention.
That is, in the invention according to claim 1 of the present invention, at least one of the substrates has translucency, and a pair of substrates arranged so that electrodes provided on the surface face each other,
A light modulation element provided between the pair of substrates and having a light control layer including at least a liquid crystal drop or a liquid crystal microcapsule, a polymer binder, and a resin spacer.

  The invention according to claim 2 is the light modulation element according to claim 1, wherein the resin spacer has a polygonal prism shape.

  The invention according to claim 3 is the light modulation element according to claim 1 or 2, wherein the liquid crystal drop or the liquid crystal microcapsule is also in a polygonal column shape.

  The invention according to claim 4 is the light modulation element according to any one of claims 1 to 3, wherein a maximum length difference between the liquid crystal drop or liquid crystal microcapsule and the resin spacer is within ± 50%.

  The invention according to claim 5 is the light modulation element according to any one of claims 1 to 4, wherein the liquid crystal drop or liquid crystal microcapsule and the resin spacer are arranged in a single layer and densely.

  The invention according to claim 6 is the light modulation element according to any one of claims 1 to 5, wherein a coating layer is provided on the light control layer.

According to a seventh aspect of the present invention, at least one has translucency and is provided between a pair of substrates disposed so that electrodes provided on a surface thereof are opposed to each other, and at least a liquid crystal drop or A light modulation layer comprising a liquid crystal microcapsule, a polymer binder and a resin spacer, and a step of providing the light modulation layer,
On the substrate, a coating step of coating a light control layer coating liquid in which liquid crystal drops or liquid crystal microcapsules and curable resin droplets are dispersed in a solution containing a polymer binder and a solvent;
The coating layer formed by the coated light control layer coating solution is predetermined in an atmosphere at a temperature higher than the freezing point of the polymer binder and the same as or close to the saturated vapor pressure of the solvent. Holding process for holding time;
A drying step of evaporating and drying the solvent in the coating layer at a temperature below the freezing point of the polymer binder;
Is a manufacturing method of a light modulation element having

  The invention according to claim 8 is the method for manufacturing a light modulation element according to claim 7, further comprising a covering layer forming step of forming a covering layer on the coating layer.

  The invention according to claim 9 is the method of manufacturing a light modulation element according to claim 7 or 8, wherein a difference in specific gravity between the liquid crystal and the curable resin is −0.5 or more and +0.5 or less.

According to the first aspect of the present invention, a light modulation element in which the intensity of the light control layer is increased without lowering the display characteristics can be obtained as compared with the case where the present configuration is not provided.
According to the second aspect of the present invention, the display characteristics are further improved as compared with the case where the present configuration is not provided.
According to the invention which concerns on Claim 3, compared with the case where it does not have this structure, stability of a display and intensity | strength is improved more.
According to the invention which concerns on Claim 4, compared with the case where it does not have this structure, stability of a display and intensity | strength is improved more.
According to the fifth aspect of the present invention, it is possible to obtain a light modulation element that retains the strength and further suppresses the deterioration of the display characteristics due to the introduction of the spacer as compared with the case where the present configuration is not provided.
According to the invention which concerns on Claim 6, compared with the case where it does not have this structure, the density of the liquid crystal droplet and spacer particle | grains in a light control layer is raised more, and a display characteristic improves more.
According to the seventh aspect of the present invention, it is possible to efficiently manufacture a light modulation element in which the intensity of the light control layer is increased without lowering the display characteristics as compared with the case where the present configuration is not provided.
According to the eighth aspect of the present invention, it is possible to manufacture a light modulation element in which the liquid crystal droplets and the resin spacer particles in the light control layer are more uniform than in the case without this configuration.
According to the ninth aspect of the invention, as compared with the case where this configuration is not provided, it is possible to manufacture a light modulation element that is not biased by the arrangement of liquid crystal droplets and resin spacer particles in the light control layer.

Hereinafter, the light modulation element of the present invention and the manufacturing method thereof will be described in detail with reference to embodiments.
The light modulation element of this embodiment has at least one light-transmitting property, a pair of substrates disposed so that electrodes provided on the surface face each other, and a pair of substrates disposed between the pair of substrates, and at least a liquid crystal drop Or a light control layer including a liquid crystal microcapsule, a polymer binder, and a resin spacer.

In order to increase the strength of the light control layer in the light modulation element described above, it is effective to provide ribs or the like in advance when the light control layer is formed. However, in the manufacturing method in which ribs and spacers are provided in advance before forming a layer, these behave like foreign substances with respect to the liquid crystal, and when a coating liquid containing liquid crystal droplets is poured, the liquid crystal droplets aggregate or on the spacer. It will accumulate.
In the present embodiment, it has been found that the layer formation and the spacer introduction can be performed simultaneously by the manufacturing method described later, and the light modulation element having the above characteristics has been obtained.

FIG. 1 shows a schematic cross-sectional view of an example of the light modulation element of the present embodiment. As shown in the figure, in the light modulation element 10 of the present embodiment, a pair of non-display surface substrates (substrates) provided to face each other. ) 13 and a display surface substrate (substrate) 20, a light control layer 30 including a liquid crystal drop 32 and a resin spacer 33 is provided. The non-display surface substrate 13 has a configuration in which the electrode 12 is laminated on the support substrate 11. The display surface substrate 20 has a configuration in which an electrode 22 is stacked on a support substrate 21. The non-display surface substrate 13 is provided with a light shielding layer 14, and the display surface substrate 20 is provided with a light control layer 30, which are stacked via an adhesive layer 16.
Although illustration is omitted, an adhesive layer may be provided between the electrode 22 and the light control layer 30 and between the electrode 12 and the light shielding layer 14. The light shielding layer 14 may be provided outside the non-display surface substrate 13, that is, on the side where the electrode 12 is not formed, or between the electrode 22 on the display surface substrate 20 side and the light control layer 30. The light control layer 30 includes a spherical liquid crystal drop 32 including a liquid crystal 32 a and a spherical resin spacer 33 arranged in gelatin (polymer binder) 34.

  In the light modulation element 10 configured as described above, when a voltage is applied to the opposing electrode 22 and the electrode 12, the orientation state of the cholesteric liquid crystal is controlled according to the applied voltage, and the incident light incident on the light control layer 30. Light is selectively reflected by the cholesteric liquid crystal.

  The light control layer 30 of the light modulation element 10 shown in FIG. 1 may include a liquid crystal microcapsule in a form in which the liquid crystal 32a is wrapped in a polymer shell, that is, a liquid crystal microcapsule, instead of the cholesteric liquid crystal as a drop. In the following description, when it is referred to as “liquid crystal drop” unless otherwise specified, the contents are similarly applied to the liquid crystal microcapsules.

Further, in the present embodiment, as shown in FIG. 2, it is desirable that the resin spacer 35 has a polygonal column shape, and it is also desirable that the liquid crystal drop 36 including the liquid crystal 36a has a polygonal column shape.
If the resin spacer 35 has a polygonal column shape, particularly a hexahedron shape, the resin spacer 35 can come into contact with the substrate having electrodes as shown in the figure, the arrangement of the spacer is stabilized, and the adjustment by introducing the spacer is possible. Occurrence of irregularities on the optical layer surface can also be suppressed. In addition, since the liquid crystal drops 36 are also in a polygonal column shape, similarly, the liquid crystal drops 36 can be densely aligned with the resin spacers 35 in the polygonal column shape, and the stability of display and strength is further improved. It is done.

Here, the “polygonal column shape” means that when the light control layer surface is observed with a microscope at a magnification of about 500 to 1000 times, the particle shape such as a liquid crystal drop is not a circle and has two or more corners in the outline. Means things. Also, at this time, for example, by changing the focus with a laser microscope or the like and examining the shape change in the direction perpendicular to the observation surface, confirming that the same shape continues in the depth direction, it may be a polygonal column shape It is judged clearly.
In the light modulation element, the resin spacer or the like having a polygonal column shape means that 50% by number or more of the entire resin spacer particles or the like to be observed have a polygonal column shape.

  Furthermore, it is desirable that the resin spacer and the liquid crystal drop have substantially the same size. Since the resin spacer and the liquid crystal drop are the same size, as shown in FIG. 2, for example, when the resin spacer 35 and the liquid crystal drop 36 are arranged in a single layer, a denser arrangement can be achieved.

Here, “substantially the same size” means that the maximum length difference between the two particles is within ± 50%, and the maximum length is obtained by image analysis of the photo of the light control layer surface observed by the microscope, and liquid crystal drop particles In addition, the maximum length is obtained for each of 1,000 or more resin spacer particles, and is obtained as a difference between the average values thereof.
The “dense arrangement” means that the resin spacers and the liquid crystal drops are closely arranged in parallel without leaving a gap of 100% or more of the maximum length.

  As the light modulation element of the present embodiment, the configuration shown in FIG. 3 in which a coating layer 40 is further provided on the light control layer 31 is more preferable. As will be described later, in order for the resin spacer and the liquid crystal drop to have a polygonal column shape, it is necessary to apply a light control layer coating solution to solidify gelatin once and then to gelatinize and hold the gelatin again. At this time, by forming a coating layer 40 that is a gelled film (a film that does not sol under the above-described holding process conditions) on the light control layer before solification, the polygonal column shape in the holding process is provided. Can be performed efficiently.

The covering layer 40 also has a function of protecting the light control layer 31 so that the light control layer 31 is not exposed to the outside when the light modulation element is manufactured. Disturbance is suppressed and display characteristics are improved.
The “gelled film” in the present embodiment is a film that is three-dimensionally hydrogen bonded and insoluble in a solvent, and can be confirmed by an ultrasonic viscosity measuring device.

  Further, in the present embodiment, for example, the light modulation element 10 shown in FIG. 1 is a light modulation element 24 having a configuration in which a photoconductive layer 50 is provided between the electrode 12 and the light shielding layer 14 as shown in FIG. Also good. According to the light modulation element 24 shown in FIG. 4, it is possible to control the alignment state of the cholesteric liquid crystal by applying a bias voltage between the electrode 12 and the electrode 22 and irradiating the photoconductive layer 50 with write light. it can.

  The support substrate 21 and the support substrate 11 correspond to the substrate in the present embodiment, the liquid crystal drop 32 and the liquid crystal microcapsule 36 each correspond to the liquid crystal drop and the liquid crystal microcapsule in the present embodiment, and the resin spacer 33. , 35 correspond to the resin spacer in this embodiment. Each of the electrode 12 and the electrode 22 corresponds to an electrode in the present embodiment, and the light modulation element 10, the light modulation element 23, and the light modulation element 24 correspond to a light modulation element in the present embodiment.

Next, each component used for the light modulation element described above will be described.
<Board>
The support substrate constituting the substrate is formed using glass and silicone or polymer films such as polyethylene terephthalate, polysulfone, polyethersulfone, polycarbonate, etc., which have insulating properties, and at least one of the supports that is particularly visible The substrate (supporting substrate constituting the display surface substrate) is formed of a material that is transmissive to incident light and reflected light. Moreover, you may form well-known functional films, such as a pollution protection film, an abrasion-resistant film | membrane, a light reflection prevention film, and a gas barrier film, on the surface of a support substrate as needed.

  The electrode provided on the support substrate is formed using a conductive metal thin film such as gold or aluminum, a metal oxide such as indium oxide or tin oxide, or a conductive organic polymer such as polypyrrole, polyacetylene, or polyaniline. In addition, at least the electrode on the display surface side is formed of a material that is transmissive to incident light and reflected light. Moreover, you may form well-known functional films, such as an adhesive force improvement film | membrane, a light reflection prevention film | membrane, and a gas barrier film, on the surface as needed.

<Light control layer>
The light control layer has a structure in which liquid crystal drops or liquid crystal microcapsules made of liquid crystals are dispersed and held in gelatin. If the layer thickness of the light control layer is too large, it is necessary to increase the driving voltage applied between the electrodes. If the layer thickness is too small, the contrast of the light modulation element is lowered, so that the driving voltage is lowered and the contrast is increased. It is preferable that they are 1 micrometer or more and 100 micrometers or less.
The light control layer in the light modulation device of the present embodiment may be formed of a single layer or a plurality of liquid crystal drops or liquid crystal microcapsules, but in order to suppress unevenness of the light control layer A single layer is preferable.

(liquid crystal)
As the liquid crystal material that can be used for the liquid crystal drop or the liquid crystal microcapsule in the light control layer, any liquid crystal material may be used as long as it has refractive index anisotropy and the orientation is changed by voltage application. However, cholesteric liquid crystals (including chiral nematic liquid crystals) are preferable.
The cholesteric liquid crystal material used in this embodiment is a steroid cholesterol derivative, or a Schiff base, azo, azoxy, benzoate, biphenyl, terphenyl, cyclohexylcarboxylate, or phenylcyclohexane. , Biphenylcyclohexane, pyrimidine, dioxane, cyclohexylcyclohexane ester, cyclohexylethane, cyclohexane, tolan, alkenyl, stilbene, condensed polycyclic nematic liquid crystals, smectic liquid crystals, or mixed liquid crystals thereof A material to which a chiral component made of an optically active material such as Schiff base, azo, ester, or biphenyl is added can be used.

(Resin spacer)
In the light control layer, a curable resin is preferably used as the resin spacer.
As the curable resin, a photocurable resin, a radiation curable resin, an electron beam curable resin, a thermosetting resin, or the like can be used. Among them, a photocurable resin and a thermosetting resin are preferably used. As the photocurable resin or thermosetting resin, a photocurable or thermosetting monomer, an oligomer, or a mixture of a monomer and an oligomer is preferably used. In addition, as curable resin used for this embodiment, since it disperse | distributes to the coating liquid for light control layers through the emulsification process mentioned later, it is desirable that it is not water-soluble.

  As said thermosetting resin, what is known as resin hardened | cured (insolubilized) when heated can be applied. For example, phenol-formaldehyde resin, urea-formaldehyde resin, melamine-formaldehyde resin, resin obtained by curing acrylic polyol with isocyanate, resin obtained by curing polyester polyol with melamine, or resin obtained by curing acrylic acid with melamine . Moreover, you may use combining the monomer which is a structural component of a thermosetting resin.

In addition, any thermoplastic resin that is cured by crosslinking and has heat resistance is included in the thermosetting resin. As such a thermosetting resin, for example, a thermosetting acrylic resin is preferably used. Thermosetting acrylic resin is obtained by crosslinking at least one acrylic monomer or a copolymer obtained by polymerizing acrylic monomer and styrene monomer with melamine compound or isocyanate compound. It is. Furthermore, a thermosetting silicone resin is also preferable.
In these, a thermosetting silicone resin can be used especially suitably.

Examples of the photocurable resin composition include a compound having a reactive double bond such as a vinyl group in a molecule (not only a low molecular weight substance but also a polymer), and a start necessary for photocuring. And the like mainly containing an agent.
Examples of the compound having a reactive double bond in the molecule include a (meth) acryloyl group, such as methyl (meth) acrylate, ethyl (meth) acrylate, benzyl (meth) acrylate, and 2-ethoxyethyl (meth). Monofunctional type such as acrylate, phenoxydiethylene glycol (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) Acrylate, trimethylpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc. There is a functional type. Further, there are oligomers such as polyester acrylate, polyurethane acrylate, epoxy acrylate, polyether acrylate, oligo acrylate, alkyd acrylate, polyol acrylate and the like. Furthermore, there are, for example, styrene monomer, α-methylstyrene, divinylbenzene, vinyl acetate, pentene, hexene and unsaturated compounds having a vinyl group or an allyl group. Furthermore, thiol polymerizable monomers and epoxy polymerizable monomers are also effective.
As the photocuring polymerization initiator, for example, benzoin alkyl ether-based, acetophenone-based, benzophenone-based, thioxanthone-based photoinitiators are preferably used.

As these curable resins, it is desirable that the curing time is not limited by heating or the like in the light control layer forming step described later, and from this viewpoint, a photocurable resin that can be arbitrarily cured by light irradiation is used. Is preferred.
In particular, as a resin spacer, it is desirable that the refractive index is close to the liquid crystal used in that it does not adversely affect the display characteristics. For example, NOA65 (manufactured by Norland), which is an ultraviolet curable thiol polymerizable monomer, is preferable. .

In the light control layer used in this embodiment, the resin spacer concentration (resin spacer volume ratio with respect to the total volume of the liquid crystal drop and the resin spacer) is desirably 0.01 volume% or more and 10 volume% or less, and 0.5 volume. % To 2.0% by volume is more preferable.
If the volume ratio is less than 0.01% by volume, it may not be possible to secure a strength that does not affect the display characteristics against external pressure or the like. If it exceeds 10% by volume, display characteristics such as a decrease in reflectance may be adversely affected.

  Note that the volume ratio is obtained by taking image data of 1000 or more particles from an observation photograph with a microscope on the surface of the light control layer, measuring the maximum diameter of each particle, and measuring the maximum diameter of each particle as a spherical particle. The total volume of the liquid crystal drop and the resin spacer was determined as the volume of.

(Polymer binder)
The polymer binder in the present embodiment holds the liquid crystal drop or liquid crystal microcapsule and suppresses the flow of the liquid crystal drop or liquid crystal microcapsule due to deformation of the light modulation element. The polymer binder is a polymer material that uses a liquid that does not dissolve in the liquid crystal material and is incompatible with the liquid crystal drop or the liquid crystal microcapsule, and has a strength that can withstand external force, and at least reflects light and incident light. The material is not particularly limited as long as the material has high permeability. For example, a water-soluble polymer material (for example, gelatin, polyvinyl alcohol, cellulose derivative, polyacrylic acid polymer, ethyleneimine, polyethylene oxide, polyacrylamide, polystyrene sulfone). Preferable examples include acid salts, polyamidines, isoprene-based sulfonic acid polymers), and materials that can be emulsified in water (for example, fluorine resins, silicone resins, acrylic resins, urethane resins, and epoxy resins).
Among these, gelatin is particularly preferable from the viewpoint that the surface unevenness can be reduced and a flat light control layer can be obtained.

As the gelatin, gelatin having a high jelly strength and a low sol viscosity is preferable.
As such gelatin, those having a high molecular weight β chain / γ chain, which is a polymer of α chains, and low molecular weight components in which the main chain of the α chain is cut off in the middle and having a large α chain remaining amount are suitable. Yes. A gelatin material produced by acid treatment of bovine bone is preferable because it satisfies this condition, and particularly has high jelly strength and low sol viscosity. Moreover, the 1st extract extracted first when hydrolyzing the collagen of a raw material is good. In order to prevent ionic contamination of the liquid crystal material, ionic components remaining in the gelatin may be removed using a known technique such as an ion exchange resin.

<Coating layer>
As the coating layer, a gelled film (gelated film) as described above is used. The gelled film is not particularly limited as long as it shows a sol-gel state depending on the temperature and has a property of not dissolving a liquid crystal drop or the like in the gelled state. In this embodiment, “gelate” and “become in a gel state” mean that when the saturated viscosity in a gel state is 100 and the saturated viscosity in a sol state is 0, the normalized viscosity Means that the value becomes 70 or more.

  As the colloidal particles that form the gelled film, natural polymer, synthetic polymer, or semi-synthetic polymer can be used, and agar, gelatin, cellulose, carrageenan, alginic acid, xanthan gum, pectin, seed gum, and far celeran. Exemplifying polymers such as curdlan, polyvinyl alcohol, polyacrylonitrile, polyethylene oxide and derivatives thereof, or mixtures thereof, or those mixed with polymers having no low-temperature gelation properties as a low-temperature gelling agent Can do. Of these, agar and its derivatives exhibiting large hysteresis in the sol-gel change behavior with respect to temperature change are preferable. As the physical properties of the polymer solution, those having high jelly strength and low sol viscosity are preferred.

  The thickness of the coating layer is desirably 0.1 μm or more and 5.0 μm or less, and more preferably 0.5 μm or more and 2.0 μm or less. If the layer thickness exceeds 5.0 μm, the voltage drop at the gelled film increases, causing a problem of increasing the drive voltage. If the layer thickness is less than 0.1 μm, the surface of the light control layer cannot be sufficiently covered. There are cases where the shape of the liquid crystal drop or the resin spacer becomes non-uniform or the diffusion of the liquid crystal cannot be suppressed.

<Photoconductive layer>
The photoconductive layer is composed of a-Si: H, a-Se, Te-Se, As ₂ Se ₃ , CdSe, CdS.
Inorganic photoconductors such as azo pigments, phthalocyanine pigments, perylene pigments, quinacridone pigments, pyrrolopyrrole pigments, indigo pigments, anthrone pigments, and charge transport materials such as arylamines, hydrazones, triphenylmethane, and PVK The organic photoconductor (OPC) is a combination of the two, and an OPC layer in which two charge generation layers and a charge transport layer are stacked is preferable.

  The charge generation layer is a layer having a function of absorbing address light and generating photocarriers. Mainly, the amount of light carriers that the charge generation layer flows from the electrode on the display surface side to the electrode on the writing surface side, and the amount of light carriers that the charge generation layer flows from the electrode on the writing surface side to the electrode on the display surface side. , Each has an influence. The charge generation layer is preferably one that absorbs address light to generate excitons and can be efficiently separated into free carriers within the CGL or at the CGL / CTL interface.

  The charge generation layer is formed of a charge generation material (for example, metal or metal-free phthalocyanine, squalium compound, azurenium compound, perylene pigment, indigo pigment, azo pigment such as bis and tris, quinacridone pigment, pyrrolopyrrole dye, polycyclic quinone pigment, dibromoanthanthrone. Such as fused-ring aromatic pigments, cyanine dyes, xanthene pigments, charge transfer complexes such as polyvinylcarbazole and nitrofluorene, kyosho complexes composed of pyrylium salt dyes and polycarbonate resins), or these charge generation materials A polymer binder (for example, polyvinyl butyral resin, polyarylate resin, polyester resin, phenol resin, vinyl carbazole resin, vinyl formal resin, partially modified vinyl acetal resin, carbonate resin, acrylic resin, A coating solution prepared by dispersing or dissolving it in an appropriate solvent together with a vinyl chloride resin, a styrene resin, a vinyl acetate resin, a vinyl acetate resin, a silicone resin, etc.) Can be formed.

The charge transport layer is a layer having a function of drifting in the direction of an electric field applied with a bias signal when photocarriers generated in the charge generation layer are injected.
In the charge transport layer, free carriers are efficiently injected from the charge generation layer (preferably close to the ionization potential of the charge generation layers 23 and 25), and the injected free carriers hop and move as fast as possible. Is preferred. In order to increase the dark impedance, it is preferable that the dark current due to the heat carrier is low.

  The charge transport layer comprises a low molecular weight hole transport material (for example, trinitrofluorene compound, polyvinylcarbazole compound, oxadiazole compound, hydrazone compound such as benzylamino hydrazone or quinoline hydrazone, stilbene compound, Phenylamine compounds, triphenylmethane compounds, benzidine compounds), or low molecular electron transport materials (for example, quinone compounds, tetracyanoquinodimethane compounds, furfreon compounds, xanthone compounds, benzophenone compounds) Dispersed or dissolved in an appropriate solvent together with a polymer binder (for example, polycarbonate resin, polyarylate resin, polyester resin, polyimide resin, polyamide resin, polystyrene resin, silicon-containing crosslinked resin, etc.) There may be formed by the hole transporting material and electron transport material were prepared are dispersed or dissolved in a suitable solvent polymerized material, then it was applied and dried.

<Light shielding layer>
The light shielding layer provided as necessary is an insulating cadmium-based, chromium-based, cobalt-based, manganese-based, carbon-based inorganic pigment, or azo-based, anthraquinone-based, indigo-based, triphenylmethane-based, nitro-based , Phthalocyanine, perylene, pyrrolopyrrole, quinacridone, polycyclic quinone, squalium, azurenium, cyanine, pyrylium, anthrone organic dyes and pigments, or these as polymer binders It is formed using a dispersed material, and is configured to have light absorptivity with respect to at least reflected light.

<Adhesive layer>
The adhesive layer provided as necessary uses a material that can adhere the light control layer and the light shielding layer by heat or pressure, such as urethane resin, epoxy resin, acrylic resin, or silicone resin. The position where the adhesive layer is inserted is not limited to this embodiment, and may be between the electrode and the light control layer, or between the electrode and the light shielding layer. In the case where an adhesive layer is formed between the electrode and the light control layer, the adhesive layer is formed of a material having transparency to at least incident light and reflected light.

  Next, a method for manufacturing the light modulation element of this embodiment will be described. Here, in order to simplify the explanation, as shown in FIGS. 1 and 2, a light control layer including a liquid crystal drop is provided between the non-display surface substrate and the display surface substrate which are provided to face each other. The case where it is possible will be described.

  In the light modulation element of the present embodiment, for example, a light shielding layer is laminated on a non-display surface substrate as a support substrate having electrodes on the surface, and a light control layer is provided on the display surface substrate as a support substrate having electrodes on the surface. After stacking, the electrode of the non-display surface substrate as the support substrate having the electrode on the side where the electrode was formed and the display surface substrate as the support substrate having the electrode on the surface were formed through the adhesive layer It is manufactured by overlapping and adhering so that the surfaces face each other.

  The light modulation element of the present embodiment is obtained by mixing a curable resin droplet that becomes a resin spacer in the light control layer forming step, or by deforming the liquid droplet. The process will be mainly described. The polymer binder used for the light control layer is a form using gelatin which is a suitable material.

In this embodiment, the step of providing the light control layer is performed by applying a light control layer coating liquid in which liquid crystal drops or liquid crystal microcapsules and curable resin droplets are dispersed in a solution containing gelatin and a solvent on the display surface substrate. And a coating layer formed by the coated light control layer coating solution at a temperature higher than the freezing point of gelatin and the same as or near the saturated vapor pressure of the solvent for a predetermined time. A holding step of holding, and a drying step of evaporating the solvent in the coating layer at a temperature below the freezing point of gelatin and drying.
In the present embodiment, the light control layer is formed by applying (1) a method of performing only the coating process of the light control layer forming coating solution, and (2) forming a coating layer that forms a coating layer in addition to the coating process. And the method of performing the process.

A. FIG. 5 is a schematic process diagram showing a case where the light control layer is formed only by the application process of the light control layer coating liquid.
The light control layer formation by this method is a step of applying a light control layer coating liquid (step (A1)), a step of holding the applied layer at a constant temperature (steps (A2, A3)), and a step of drying (step). (A4).

(Preparation of coating solution for light control layer)
First, preparation of the light control layer coating solution used for light control layer application will be described in detail.
The light control layer coating solution is prepared, for example, by dispersing liquid crystal drops or liquid crystal microcapsules and curable resin droplets serving as resin spacers in a solution containing gelatin and a liquid.
Hereinafter, a method for preparing a liquid crystal drop and a liquid crystal microcapsule will be described.

-Preparation of liquid crystal drop emulsion-
The liquid crystal drop emulsion is prepared by emulsifying and dispersing a dispersed phase composed of at least a cholesteric liquid crystal in a continuous phase incompatible with the dispersed phase, for example, an aqueous phase. As a means for emulsification, after mixing the dispersed phase and the continuous phase, a method of dispersing the dispersed phase as fine droplets by mechanical shearing force such as a homogenizer, or extruding the dispersed phase through the porous film in the continuous phase, For example, a film emulsification method in which fine droplets are dispersed can be used. In particular, the membrane emulsification method is preferable because liquid crystal drops having a uniform particle diameter can be formed because the dispersion of the particle diameters of the emulsified droplets is small. A small amount of a surfactant or protective colloid for stabilizing the emulsification may be mixed in the continuous phase during emulsification.

-Preparation of liquid crystal microcapsule slurry-
In preparing a liquid crystal microcapsule in which a cholesteric liquid crystal is encapsulated in a polymer shell, a known liquid crystal microencapsulation method such as a phase separation method, an interfacial polymerization method, or an in situ polymerization method can be used. Specifically, the liquid crystal drop produced as described above is dispersed in a solution containing a polymer shell material, or is thermoset according to the material to form a polymer shell around the liquid crystal drop. . Also, when making urethane / urea polymer shells, a polyisocyanate compound is added to the liquid crystal drop in advance, and the liquid crystal drop is added to a solution containing the polyhydric alcohol to generate a urethane / urea reaction. It is preferable to cause

  As the polymer shell, a material that does not dissolve in the encapsulated liquid crystal material is used. For example, gelatin, cellulose derivative, gelatin-gum arabic, gelatin-gellan gum, gelatin-peptone, gelatin-carboxymethylcellulose, polystyrene, polyamide, nylon, polyester, poly Examples include phenyl ester, polyurethane, polyurea, melamine formalin resin, phenol formalin resin, urea formalin resin, acrylic resin, and methacrylic resin.

  If the particle size of the liquid crystal microcapsules is too small, sufficient reflection characteristics cannot be obtained, which deteriorates display characteristics and lowers contrast. On the other hand, if the wall thickness of the liquid crystal microcapsule by the polymer shell is too thick, the amount of the liquid crystal material included in the liquid crystal microcapsule decreases, and if it is too thin, the strength decreases. Therefore, in order to suppress the decrease in strength with high contrast, the wall thickness of the liquid crystal microcapsule is set to 1% to 25%, preferably 3% to 21%, of the radius of the liquid crystal microcapsule.

The volume average primary particle size of the liquid crystal microcapsules and the liquid crystal drop is preferably 1 μm or more and 100 μm or less, more preferably 3 μm or more and 20 μm or less, and particularly preferably 10 μm or more and 15 μm or less. If the volume average primary particle size of the liquid crystal microcapsules and the liquid crystal drop exceeds 100 μm, the drive voltage increases, and if it is less than 1 μm, sufficient reflection characteristics may not be expected.
However, at this stage, it is desirable that the particle size of the liquid crystal drop or the like is substantially the same as the particle size of the curable resin droplet mixed as the light control layer coating liquid.

-Preparation of curable resin emulsion-
The curable resin emulsion is prepared by emulsifying and dispersing at least a dispersed phase composed of a curable resin in a continuous phase that is incompatible with the dispersed phase, for example, an aqueous phase. As the curable resin, a resin that can be sufficiently cured in the holding step described later and has excellent dispersibility is selected from the various resins.

  In particular, in the present embodiment, liquid crystal drops and curable resin droplets are uniformly dispersed and uniformly arranged when the gelatin layer is hardened after the light control layer coating solution is applied or when the gelatin layer is subsequently solated. From this point of view, it is desirable that the difference in specific gravity between the liquid crystal and the curable resin is small. Specifically, the difference in specific gravity between the liquid crystal and the curable resin used for the light control layer is preferably −0.5 or more and 0.5 or less, and more preferably −0.1 or more and 0.1 or less. It is.

The means for emulsifying is the same as in the case of the liquid crystal drop emulsion. The volume average primary particle size of the curable resin droplets is preferably 1 μm or more and 100 μm or less, more preferably 3 μm or more and 20 μm or less, and particularly preferably 10 μm or more and 15 μm or less. When the volume average particle size exceeds 100 μm, the thickness as a display element increases, which may be unfavorable for driving. When the volume average particle size is less than 1 μm, a sufficient spacer effect may not be obtained after sufficient curing.
However, at this stage, it is desirable that the particle diameter of the curable resin droplet is substantially the same as the particle diameter of the liquid crystal drop or the like mixed as the light control layer coating liquid, as described above.

-Concentration-
If the non-volatile concentration of the liquid crystal drop emulsion, liquid crystal microcapsule slurry, or curable resin emulsion after the above process is low and cannot be adjusted to the non-volatile concentration required for the light control layer coating liquid during coating, concentration is performed. Using liquid crystal drop or liquid crystal microcapsule, or difference in specific gravity between curable resin and continuous phase, settling by standing or centrifuging or removing continuous phase separated by settling or filtering with membrane filter Use methods.

A liquid crystal drop emulsion, a liquid crystal microcapsule slurry, or a curable resin emulsion obtained as described above is dispersed in a solution containing gelatin and a solvent to prepare a light control layer coating solution.
In this case, in order to apply a liquid crystal drop or the like on a support substrate in a single layer and densely, using a density meter or a hydrometer, the liquid crystal drop emulsion or liquid crystal microcapsule slurry, containing each component in the curable resin emulsion It is desirable to measure the amount and adjust the mixing ratio of gelatin, solvent, liquid crystal drop or liquid crystal microcapsule and curable resin in the light control layer coating solution.

The ratio (volume ratio) of the nonvolatile component volume to the coating liquid volume for the light control layer is Sr, the ratio (volume ratio) of the liquid crystal drop or liquid crystal microcapsule and the curable resin to the nonvolatile component volume is Lr, the liquid crystal drop or the liquid crystal micro When the average particle diameter (μm) of the capsule and the curable resin is D _L and the wet coating thickness (μm) on the non-display surface substrate is t _W , the ratio A of the coating area of the liquid crystal drop or the liquid crystal microcapsule to the coating area A _L is represented by the following formula (1).
A _L = (3/2) · (t _W · Sr · Lr / D _L ) (1)

Then, it is preferred that A _L is adjusted to the following formula (2) coating dimmer layer coating solution to be in the range.
0.8 <A _L <1.0 Formula (2)

  The Sr means Sr = Y / X when the non-volatile component remaining when the solvent is evaporated from the light control layer coating solution Xcc is Ycc, and a Zcc liquid crystal drop or liquid crystal microcapsule is included in the non-volatile component Ycc. If included, it means Lr = Z / Y.

In order to prevent breakage due to pressure or the like, the ratio (volume ratio) Lr of the volume of the liquid crystal drop or liquid crystal microcapsule to the nonvolatile component volume and the curable resin is preferably set to 0.9 or less.
Based on the calculated mixing ratio, the amount of gelatin and solvent mixed with the liquid crystal drop emulsion, the liquid crystal microcapsule slurry, or the curable resin is adjusted to prepare a coating liquid for coating light control layer. Here, you may add a trace amount of well-known coating liquid characteristic modifiers for light control layers, such as a thickener, a wettability improving agent, and a drying rate modifier.

  As the solvent contained in the light control layer coating liquid of the present embodiment, a solvent that dissolves gelatin, does not dissolve the curable resin, and does not dissolve liquid crystal in the case of a liquid crystal drop, uses a liquid crystal microcapsule. In this case, at least a liquid crystal microcapsule polymer shell that does not dissolve is used. Examples of such a solvent include pure water, ion exchange water, distilled water, tap water, and the like, water-soluble organic solvents, or liquids obtained by mixing water such as ion exchange water, distilled water, tap water, and water-soluble organic solvents. The water-insoluble organic solvent, the ionic liquid, and the like are appropriately selected according to the use and use conditions.

In the present embodiment, the solvent is preferably contained in an amount of 75% by mass to 95% by mass, and more preferably 80% by mass to 90% by mass with respect to the light control layer coating solution. When the content of the solvent is in the range of 75% by mass to 90% by mass, the viscosity can be adjusted to allow application of the light control layer coating solution.
The mixing mass ratio between the liquid crystal drop or the like and the curable resin (liquid crystal drop / curable resin) is determined by calculation from a necessary volume ratio.

(Process for applying light-control layer coating solution (process (A1)), application process)
The application of the light-adjusting layer coating solution with the concentration adjusted as described above to the display surface substrate is a known apparatus that can be applied to a desired wet thickness such as an applicator, edge coater, screen coater, roll coater, curtain coater, die coater. To do.
In FIG. 5, a coating liquid containing uncured curable resin droplets 72 a and liquid crystal drops 74 a is applied onto the substrate 60 having the electrodes 62 by the edge coater 64, thereby forming the coating layer 70.

  In the coating step, it is necessary to heat the gelatin of the light control layer coating solution to a temperature higher than the melting point to maintain a fluid sol state. Gelatin becomes sol when heated to a temperature above its melting point and gels and loses fluidity when lowered to a temperature below its freezing point. Although it varies depending on the concentration and pH of the gelatin aqueous solution, the freezing point of commercially available gelatin is 20 ° C. to 30 ° C., and the melting point is about 5 ° C. higher than that. For this reason, in the coating process, the light control layer coating liquid is preferably maintained at a temperature of the light control layer coating liquid of 20 ° C. to 80 ° C. as the temperature of the freezing point of 20 ° C. or higher, and the light control layer of 30 ° C. to 70 ° C. It is more preferable to maintain the coating solution temperature for the layer. If the temperature of the coating liquid for the light control layer is less than 20 ° C, the gelatin cannot be made into a suitable viscosity due to insufficient sol formation, and if it exceeds 80 ° C, the liquid crystal material may volatilize. And the composition ratio of the liquid crystal compound may change.

(Process for holding the applied layer at a constant temperature (process (A2, A3)), holding process)
In this step, the coating layer 70 formed on the display surface substrate by the coating step is held in a hermetically sealed container, and heating to the display surface substrate is continued to make the coating layer 70 higher than the freezing point of gelatin. The coating layer 70 is held under a condition of heating to a temperature of 40 ° C. to 60 ° C., and the coating layer 70 is the same as the saturated vapor pressure in the coating layer or the saturated vapor pressure of this solvent. Hold in an atmosphere close to 1 to 10 minutes.

As a heating device for heating, an oven, a hot air blowing device, a hot plate, or the like can be used. In order to make the atmosphere the same as or close to the saturated vapor pressure of this solvent in the coating layer, a method of holding the coating layer in a container with a volume as small as possible, a method of holding in the chamber having the above-mentioned generating part Alternatively, a method in which the saturated vapor pressure of the solvent is reduced to atmospheric pressure or the like can be used.
The coating layer temperature is preferably 35 ° C. or higher and 65 ° C. or lower, and particularly preferably adjusted to be 40 ° C. or higher and 60 ° C. or lower. If it exceeds 65 ° C., there is a problem that the composition ratio of the liquid crystal compound tends to change, and if it is less than 35 ° C., the fluidity in the coating layer is low and liquid crystal drops or liquid crystal microcapsules are difficult to arrange densely.

  In this case, as shown in FIG. 5 (A2), the coating layer becomes a coating layer 73 in a sol state. Thus, the coating layer 73 is applied to the coating layer 73 while maintaining the gelatin in the coating layer in the sol state. When held in an atmosphere that is the same as or close to the saturated vapor pressure of the solvent in the solvent for a predetermined time, as shown in FIG. 5 (A3), while suppressing drying of the coating layer 73, liquid crystal drops in the coating layer or Liquid crystal microcapsules are densely arranged by specific gravity difference. When the specific gravity of the liquid crystal drop or the liquid crystal microcapsule or the curable resin is exactly the same as that of the gelatin aqueous solution, dense arrangement does not occur. However, when the specific gravity of the liquid crystal drop or liquid crystal microcapsule or the curable resin is different from that of the gelatin aqueous solution, the liquid crystal drop 74a or the like or the curable resin droplet 74a naturally settles or floats on the substrate surface. The

The atmosphere in the heating device is in a state close to the saturated vapor pressure of the solvent due to the initial volatilization of the solvent in the coating layer 73. In this state, since the solvent does not rapidly evaporate from the coating layer 73, each curable resin droplet 72a and each liquid crystal drop 74a are not distorted by intense flow.
In addition, since it is in the state close | similar to the saturated vapor pressure of a solvent in a heating apparatus, it can suppress that the coating layer 73 is dried.

Needless to say, it is desirable that there is almost no difference in specific gravity between the liquid crystal and the curable resin during the natural sedimentation and alignment as described above.
Further, when a thermosetting resin is used as the curable resin, the curing may be almost completed at the stage where it is arranged on the substrate surface (curing step). In this case, since the curable resin droplets are cured in a spherical shape, the curable resin droplets do not have a polygonal column shape in a drying process described later, and become a light control layer including a spherical resin spacer as it is.

  When the movement of the liquid crystal drop 74a and the curable resin droplet 72a or the liquid crystal microcapsule is insufficient, the coating layer 73 is vibrated, for example, mechanical vibration by an ultrasonic vibrator or the like, in part or all of the holding process. If it adds, it can make it easy to arrange | position the liquid crystal drop 74a and the curable resin droplet 72a more densely.

(Step of drying the applied layer (step (A4)), drying step)
After the liquid crystal drops in the coating layer in which the gelatin is in the sol state are densely arranged in the coating layer by the holding step, in the drying step, first, the display surface substrate is naturally cooled at room temperature or forced using a cooling device. By cooling, the gelatin in the coating layer is cooled to a temperature below the freezing point of the gelatin and the solvent in the coating layer can be volatilized. As a cooling device for cooling the display surface substrate, a cooling oven, a cooling plate using a Peltier, a cold air blowing device, or the like can be used.
By setting the drying step to a temperature below the freezing point of gelatin, the drying mode of gelatin in the coating film changes from the sol state to the gel state. Under such a temperature below the freezing point of gelatin and at a temperature at which the solvent in the coating layer can be volatilized, the solvent in the coating layer is volatilized to dry the coating layer.

  Here, since gelatin is a heat-denatured product of collagen, the molecular structure of gelatin in the sol state is a random coil shape, but gelatin in the gel state has a part of the molecule's original collagen helical structure. Network is formed. Therefore, the volumetric shrinkage of gelatin accompanying the volatilization of the liquid in the coating layer is larger when the drying process is performed in the gel state than in the sol state. For this reason, the liquid crystal drops and curable resin droplets arranged densely in the holding step have a compressive force in the thickness direction and a compressive force in the plane direction as compared with drying in the sol state by bringing the drying step into a gel state. Since the pulling force is applied, the liquid crystal drop and the curable resin drop are deformed into a polygonal column shape.

Specifically, first, the substrate 60 on which the coating layer 73 in which the curable resin droplets 72a and the liquid crystal droplets 74a are densely arranged is formed by the holding step, the coating layer 73 has a temperature equal to or lower than the freezing point of gelatin. Thus, it cools with the cooling plate which abbreviate | omits illustration.
When the gelatin in the coating layer 73 is held at a temperature below the freezing point, a sol-gel change occurs and a drying mode in the gel state is set.

  In the drying step, the substrate 60 is held by the cooling plate so that the coating layer 73 has a temperature below the freezing point of gelatin and a temperature at which the solvent can be volatilized. Volatilize the solvent.

  Thus, in the drying process, the coating layer 73 containing gelatin changes in a sol-gel manner in a state where the liquid crystal drops 74a and the curable resin drops 72a are arranged so as to be dense. After that, as shown in FIG. 5 (A4), the gelatin has a larger volume shrinkage due to the volatilization of the liquid in the coating layer when the gelatin is dried in the gel state than in the sol state. As a result, the thickness of the coating layer when the solvent is volatilized becomes a thinner coating layer 75 than when performing the sol drying. As the gelatin shrinks in volume, a compressive force acts in the thickness direction and a tensile force acts in the surface direction, and each curable resin droplet 72a and liquid crystal drop 74a are in a gel state than when dried in a sol state. It is flattened when dry. At this time, since each curable resin droplet 72a and the liquid crystal drop 74a are densely arranged by the holding step, each curable resin droplet 72a and the liquid crystal drop 74a are shown in FIG. 5 (A4), the curable resin droplets 72b and the liquid crystal drops 74b are formed in a polygonal column shape in a densely arranged state.

  The gelatin material used in the present embodiment preferably has a low sol viscosity so as not to hinder the movement of liquid crystal drops or liquid crystal microcapsules or curable resin droplets in the holding step, and the liquid crystal droplets on the surface of the light control layer after the drying step. From the above viewpoint, gelatin that has been subjected to acid treatment using cow bone as a raw material is preferable.

  The reason why the liquid crystal drop and the curable resin droplet are formed into a polygonal column shape by the sol-gel change of gelatin has not been clarified precisely. However, since gelatin is a heat-denatured product of collagen, the molecular structure of gelatin dried in a sol state has a random coil shape. However, gelatin dried in a gel state has a part of the original collagen. A network is formed with a helical structure. Therefore, it is considered that volume shrinkage occurs when gelatin changes from a sol state to a gel state. Therefore, when the coating layer is dried in the sol state, the volumetric shrinkage of gelatin accompanying the volatilization of the liquid in the coating layer is low, so the liquid crystal drop or the liquid crystal microcapsule is flattened to form a polygonal column. Is considered difficult.

  On the other hand, in the manufacturing method of the present embodiment, in the coating step, a light control layer coating liquid in which liquid crystal drops or liquid crystal microcapsules are dispersed in a solution containing gelatin and a solvent is applied onto the display surface substrate, and the next holding step. In the drying process, after the coating layer is kept in an atmosphere equal to or close to the saturated vapor pressure of the solvent at a temperature equal to or higher than the freezing point of gelatin for a predetermined time, the solvent is volatilized at a temperature equal to or lower than the freezing point of gelatin in the drying step. As the liquid in the coating layer volatilizes, the volumetric shrinkage of the gelatin is large, and the liquid crystal drop or liquid crystal microcapsule is dried in a state where the gelatin in the coating layer densely arranged in gelatin is gelled. Along with the volatilization of the solvent contained in the gelatinous gelatin, a compressive force acts in the thickness direction and a tensile force acts in the surface direction. Drop and a curable resin droplets are flattened and eventually can be polygonal shaped.

Thereafter, it is necessary to cure the curable resin droplets to form a resin spacer, but the curing of the curable resin droplets is such that the gelled coating layer does not sol when the curable resin is thermosetting. You may carry out by heating at temperature, and when curable resin is photocurable, you may carry out by irradiating light with a predetermined light source.
The curing step in this embodiment may not be particularly after the drying step, and can be performed simultaneously with the holding step when the thermosetting resin is used as described above. Even when it is used, it may be cured by light irradiation in the middle of the process.

  However, in order to make the curable resin droplets into a polygonal column shape together with the liquid crystal drop in the drying step as described above, it is desirable that the curable resin droplets are not cured at least in the drying step. In order to avoid curing by heating in the holding step or the like, and liquid crystal drops etc. are densely arranged and then disturbing them by heating again, a photocurable resin is used as the curable resin. It is desirable to perform curing by light irradiation after the drying step.

In addition, after the drying step, it is included even after the final assembly as an element. However, particularly when the display surface substrate and the non-display surface substrate are laminated and laminated, pressure deformation is applied, so that light is applied thereafter. Curing by irradiation or the like is preferable because the height of the spacer does not vary due to liquid crystal droplets.
Note that an ultraviolet lamp, an ultraviolet LED, and an ultraviolet irradiation device can be used for the light irradiation, and a heating device such as an oven can be used for the heating.

B. When performing a coating layer forming step of forming a coating layer in addition to the coating step FIG. 6 shows a case where the light control layer is formed by adding the coating layer forming step to the coating step of the light control layer coating solution. It is a schematic process drawing.
The light control layer formation by this method includes the step of applying a light control layer coating liquid (step (B1)), the step of cooling the applied layer (step (B2)), and the step of forming a coating layer on the coating layer. (Step (B3)), a step of cooling the coating layer (step (B4)), a step of holding the coating layer at a constant temperature (step (B5)), and a step of drying (step (B6)). The Among these, since the light control layer coating liquid and the step (B1) to be used are the same as the step (A1), the subsequent steps will be described below.

(Step of cooling the coating layer (step (B2)))
In this step, the coating layer applied in the step (B1) is cooled to a temperature at which it becomes a gel state. FIG. 6 (B2) shows a state after the end of the operation in this step.

  As shown in FIG. 6 (B2), in this step, the coating layer 70 applied to the substrate surface is cooled to a temperature at which the coating layer 71 becomes a hard gel state. As a specific cooling method, if the gelation temperature (the maximum temperature that maintains the gel state) is equal to or higher than the environmental temperature, it can be simply left to cool down to the environmental temperature. It may be positively cooled by a cooling device such as a plate.

(Process for forming coating layer (process (B3))
In this step, the coating layer coating solution containing colloidal particles is applied onto the coating layer 71 at a temperature at which the coating solution is in a sol state and at a temperature at which the coating solution is in a gel state. FIG. 6B3 shows a state in which the edge coater 64 forms the sol-state coating layer 80 on the coating layer 71.
The details of the colloidal particles contained in the coating layer coating solution are as already described in the respective components of the light modulation element. The coating layer coating solution is used in the form of a solution or dispersion containing the colloidal particles. If necessary, known coating properties such as thickeners, wettability improvers, antifoaming agents, and drying rate modifiers can be used. A small amount of a quality agent may be added.

  As a method for applying the coating layer coating solution onto the coating layer 71 that has become a gel state on the substrate surface, the same coating method as exemplified in the step (A1) can be applied as it is. The minimum temperature at which the coating layer coating solution maintains the sol state cannot be generally specified depending on the material. For example, when agar is used as the colloidal particles, the coating layer coating solution temperature should be 30 ° C. to 70 ° C. Is preferred.

  In this step, the temperature variation within the range in which the sol-gel state of the coating layer and coating layer coating liquid is maintained is maintained while maintaining the cooled state in the coating layer cooling step (step (B2)). Coating layer coating solution is applied). As shown in FIG. 5 (B3), in this step, the coating layer 71 already applied to the substrate surface is gelled and hardened, and the coating layer 80 in a sol-like soft state is formed there. Laminated.

  In this step, the already applied coating layer 71 is in a low temperature state and is hard in a three-dimensionally cross-linked gel state, and the laminated coating layer 80 is in a high temperature state and is in a sol state and has application suitability. is doing. The coating layer 80 applied on the coating layer 71 being cooled changes from a state immediately after the application to a gel state. Therefore, there is a concern that the particle dispersion may flow due to the shearing force generated by applying the coating layer coating liquid at this stage and the film thickness becomes non-uniform, or the solid content of the coating layer 71 flows into the coating layer coating liquid side. Alternatively, the concern that the solid content of the coating layer coating solution flows into the coating layer 71 and the two layers are mixed is eliminated.

(Step of cooling the coating layer (step B4))
After the completion of the process, before the holding process of the next process, not only the already applied coating layer 71 but also the laminated coating layer 80 must be in a gel state and cured together. There is.

  As described above, since the coating layer 80 changes to the gel state immediately after application, if the coating layer 80 is sufficiently cooled to the gel state at the end of the step (B3)), the next step is performed as it is. However, when the temperature of the coating layer coating solution at the time of application is high, it is preferable to perform the operation of this step prior to the holding step. As a result, the sol state coating layer 80 becomes a completely gelled coating layer 81.

  As a specific cooling method in the coating layer cooling step, just as in step (B2), it is simply left to cool to the ambient temperature, or actively cooled by a cooling device such as a low-temperature oven, a cold air blow, or a cooling plate. It is possible to adopt a method such as a straightforward method. At this time, for example, when cooling by cold air blow, it is desirable to make the state of FIG. 6 (B4) as soon as possible, so it is preferable to apply cold air blow in conjunction with immediately after the coating operation.

(Step of holding the coating layer at a constant temperature (step (B5)), holding step)
In the holding step, the temperature of the coating layer 71 and the coating layer 81 applied to the substrate surface in the steps (B1) to (B4) is raised to a temperature at which the coating layer is in a gel state and the coating layer is in a sol state. FIG. 6 (B5) shows a state in which an operation according to this step is performed.

  As shown in FIG. 6 (B5), in this step, the temperature is first raised to a temperature at which the coating layer applied to the substrate surface is in a soft sol state and the coating layer laminated thereon is in a gel state. In this embodiment, the point is that the layered state is once changed to the state shown in FIG. 6 (B4) and then brought into the state shown in FIG. 6 (B5) by this step.

  Therefore, in the present embodiment, the coating layer coating solution is preferably a solution containing agar or a derivative thereof and a solvent exhibiting sol-gel characteristics, and the light control layer coating solution is gelatin or a derivative thereof and a solvent. It is preferable that it is a solution containing.

  In this step, as a heating device for heating (heating), a convection electric heat device such as an oven or a hot air blow; a conductive heat transfer device such as a hot plate or a heating drum; a radiant heat transfer device such as an infrared heater; be able to.

After the temperature rise, as in the step (A3), the liquid crystal drop 74a and the like and the curable resin droplet 74a naturally settle or float on the substrate surface in the sol-coated coating layer 73, so that they are densely arranged. . In this case, it goes without saying that it is desirable that there is almost no difference in specific gravity between the liquid crystal and the curable resin during the natural sedimentation and alignment as described above.
Further, when a thermosetting resin is used as the curable resin, the curing may be almost completed when the thermosetting resin is arranged on the substrate surface. In this case, similarly, since the curable resin droplets are cured in a spherical shape, the curable resin droplets do not have a polygonal column shape in a drying process described later, and become a light control layer including a spherical resin spacer as it is.

(Drying process (process (B6))
In the drying step, both the overcoated layers are dried and cured. The temperature condition at this time is a temperature at which the coating layer finally becomes a gel state while maintaining the gel state of the coating layer. Therefore, temperature fluctuations within a range where the coating layer is in a gel state and the coating layer particle dispersion is in a sol state are allowed.

  As the drying temperature, it is necessary to heat each layer to a temperature equal to or higher than the freezing point while satisfying the above temperature condition. For example, when gelatin is used as the material of the coating layer and agar is used as the material of the coating layer, 35 It is preferable that the temperature range be from 0C to 65C.

  At this time, since the upper coating layer is a hard gel that is three-dimensionally cross-linked, the solid content of the coating layer flows into the coating layer side, or the solid content of the coating layer flows into the coating layer side. Mixing is avoided. Also, since the lower coating layer is initially dried in a sol-like soft state, the particles in the uniformly dispersed particle dispersion gradually change the positional relationship with each other as the solvent evaporates. Changes naturally.

  At this time, as in the step (A4), an effect of flattening the particles in the coating layer with the gelation of the coating layer appears. Since the film is in a covered state, the action of pushing the particles in the coating layer at the time of drying and curing is promoted, and the film can be deformed into a polygonal column shape having a uniform shape for each particle. Further, since the curable resin droplets and the liquid crystal drops are densely arranged in the holding step, the curable resin drops 72a and the liquid crystal drops 74a are arranged more densely as shown in FIG. 6 (B6). The curable resin droplets 72b and the liquid crystal drops 74b are formed into polygonal column shapes.

  After that (it may be before this or not at the time of forming the light control layer), the curable resin droplets are cured to form a resin spacer as described above.

  As described above, in the method for manufacturing a light modulation element of the present embodiment, the step of providing the light control layer includes the coating step, the holding step, and the drying step, and therefore, without providing a rib or the like. Resin spacers can be introduced, and liquid crystal drops or liquid crystal microcapsules and curable resin drops can be formed into polygonal columns without applying mechanical pressure as in the past, with improved element strength The reflectance of the light control layer can be improved.

  Specifically, according to the method for forming a light control layer in the present embodiment, it is not necessary to provide ribs in advance, so that liquid crystal droplets are not aggregated or localized when the light control layer is formed. In addition, liquid crystal drops or liquid crystal microcapsules or curable resin drops can be formed into polygonal columns without mechanically applying pressure, and they can be arranged densely (resin spacer positions are random). Therefore, the reflectance and contrast can be improved without causing unnecessary increase of scattered light and without causing disturbance of the liquid crystal droplet arrangement due to the introduction of the spacer.

  In order to write an image into the light modulation element of the present embodiment, for example, as the light modulation element having the configuration shown in FIG. 4, it is appropriately controlled from a voltage application unit by a control circuit (not shown) based on image information from the outside. While applying a voltage between the electrodes 12 and 22, the light irradiation unit irradiates address light imagewise. At this time, the address light is irradiated by being controlled in an image-like manner for each planar portion as seen from the writing surface (for example, the lower surface in the drawing) of the light modulation element, or simultaneously by scanning each surface. By irradiating the image-like address light, an image is written on the light modulation element.

  The applied voltage is controlled so that the portion not irradiated with the address light does not exceed the phase change threshold of the cholesteric liquid crystal, and only the portion irradiated with the address light exceeds the phase change threshold. . The type of phase change can be freely selected according to the purpose.

  As mentioned above, although preferable embodiment was described in detail, this invention is not limited to the above embodiment. For example, in the above-described embodiments, the light modulation element for forming a monochromatic image having only one light control layer has been described as an example. However, the light control layer and other layers may be formed as a plurality of layers as necessary. A light modulation element capable of forming a color image may be used, and at this time, a light modulation element capable of forming a full color image may be formed by laminating light control layers capable of displaying at least three primary colors of blue, green, and red.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to a following example.
<Example 1>
(Preparation of coating solution for light control layer)
Nematic liquid crystal (trade name: E7, manufactured by Merck & Co., Inc.) 77.5% by mass, chiral agent 1 (trade name: CB15, manufactured by Merck & Co.) 18.8% by mass, chiral agent 2 (trade name: R1011, Merck & Co., Inc.) A cholesteric liquid crystal which selectively reflects green color light was prepared by mixing 3.7% by mass.

Using a membrane emulsification apparatus (trade name: Microkit, manufactured by SPG Techno Co., Ltd.) on which a ceramic porous membrane having an average pore size of 4.2 μm is set, a nitrogen pressure of about 11.8 kPa (0.12 kgf / cm ² ) Then, 2 g of the cholesteric liquid crystal was emulsified in 100 ml of a 0.25 mass% aqueous sodium dodecylbenzenesulfonate solution to obtain an emulsion.

  The obtained emulsion was arbitrarily sampled and photographed with a digital microscope (trade name: VHX-200, manufactured by Keyence Corporation), and about 2500 particles photographed were measured for particle size measurement software (trade name: A Image-kun, Asahi Kasei Engineering). The average particle size of cholesteric liquid crystal drops was 14.9 μm in number average, and the standard deviation of particle size was 1.32 μm, which was close to monodispersion.

  Next, the obtained emulsion was allowed to stand to settle the cholesteric liquid crystal drop, and the supernatant was removed to obtain a concentrated emulsion. It was 0.535 when the volume ratio of the cholesteric liquid crystal drop in a concentrated emulsion was measured using the density meter (brand name: DMA35n, Nihon Shibel Hegner company make).

On the other hand, an ultraviolet curable resin (trade name: NOA65, manufactured by Norland) was added to 0.25% by mass of dodecyl under the condition of nitrogen pressure of about 11.8 kPa (0.12 kgf / cm ² ) using the membrane emulsifier. An emulsion was obtained by emulsification in 100 ml of a sodium benzenesulfonate aqueous solution.
The particle diameter of the curable resin droplets in this emulsion was 15.2 μm in number average, and the standard deviation of particle diameter was 1.55 μm.

  Subsequently, the obtained emulsion was allowed to stand to settle curable resin droplets, and the supernatant was removed to obtain a concentrated emulsion. It was 0.510 when the volume ratio of the curable resin droplet in a concentrated emulsion was measured using the density meter (brand name: DMA35n, Nihon Shibel Hegner company make).

  Assuming that all the particles in the light control layer are liquid crystal drops, the ratio AL of the coating area of the liquid crystal drop to the coating area was set to 0.95, and the wet coating thickness was set to 90 μm. Using the average particle diameter (14.9 μm) of the cholesteric liquid crystal drop and the wet coating thickness (90 μm) on the display substrate, the volume ratio of the cholesteric liquid crystal drop (Sr × Lr) was determined to be 0.10 (10% by volume).

Mixed concentrated emulsion in which the concentrated emulsion of the liquid crystal drop and the concentrated emulsion of the curable resin droplet are mixed so that the volume ratio of the curable resin droplet to the total volume of the liquid crystal drop and the curable resin droplet is 0.811% by volume. Was prepared.
Using the above values as a guideline, 7.7 of acidic bone gelatin (jelly strength: 314 g, sol viscosity (60 ° C.): 3.2 mPa · s, manufactured by Nippi) per 1 part by mass of the above mixed concentrated emulsion. By adding 4 parts by mass of a mass% aqueous solution, the volume fraction of the nonvolatile content in the coating solution is about 0.15, and the volume fraction of the liquid crystal droplet and the curable resin droplet in the nonvolatile content is about 0.70. The light control layer coating solution was prepared.

  The viscosity change with respect to the temperature of the obtained light control layer coating solution is measured with a vibration viscometer (trade name: VM-10A-M, manufactured by CBC Materials), and the maximum temperature at which this coating solution can maintain a gel state. Was about 38 ° C.

(Preparation of coating solution for coating layer)
As a coating solution for a coating layer, a 1% by weight aqueous solution (a coating solution for a protective layer) of agar (manufactured by Wako Pure Chemical Industries, Ltd.) to which 0.05% by weight of a surfactant (sodium dodecylbenzenesulfonate, manufactured by Kanto Chemical Co., Inc.) is added. ) Was prepared.
The change in viscosity with respect to the temperature of the coating liquid for protective layer obtained was measured with a vibration viscometer (trade name: VM-10A-M, manufactured by CBC Materials), and this coating liquid can maintain a gel state when the temperature is raised. When the maximum temperature was determined, it was about 80 ° C., and the maximum temperature at which the sol state could be maintained when the temperature was lowered was about 45 ° C.

(Preparation of light control layer)
-Application process-
A 125 μm thick polyethylene terephthalate (PET) substrate (trade name: High Beam, manufactured by Toray Industries, Inc.) having an ITO transparent electrode (surface resistance: 300Ω / □) formed on one side is prepared as the display surface substrate. The coating liquid is heated to 50 ° C. to make the contained gelatin into a sol state, and the gap is adjusted so that the wet film thickness after coating is 90 μm on the surface on the ITO transparent electrode side as it is. The coated layer was formed by applying with an applicator with a micrometer (trade name: K paint applicator, manufactured by Matsuo Sangyo Co., Ltd.).
Next, the substrate after coating was allowed to stand at room temperature and gradually cooled to 25 ° C. to gelatinize the gelatin contained in the coating layer.

  Subsequently, the gap is adjusted so that the wet film thickness after coating is 100 μm on the coating layer already gelled at 60 ° C. in which the agar contained in the coating layer coating solution is in a sol state. The coating layer coating solution was applied with an applicator with a micrometer (trade name: K paint applicator, manufactured by Matsuo Sangyo Co., Ltd.) to form a coating layer. And the board | substrate after application | coating was left to stand at room temperature, and it annealed to 25 degreeC, and the agar contained in a coating layer was gelatinized.

-Holding process-
The substrate after laminating the coating layer and the coating layer was placed on a hot plate at 55 ° C. and held for 10 minutes. From the results of the viscosity measurement of the light control layer coating solution and the coating layer coating solution, the gelatin of the coating layer changed from the gel state to the sol state at the initial stage of drying, and the agar of the coating layer maintained the gel state. Presumed to be.

  The behavior of the coating layer in the holding process was photographed with a digital microscope (trade name: VHX-200, manufactured by Keyence Corporation), and the state of each time was observed. As the drying progressed, the cholesteric liquid crystal drop and the curable resin gradually increased. It was confirmed that the droplets changed into a dense state while gradually changing their positional relationship.

-Drying process-
The display surface substrate in which the cholesteric liquid crystal drop and the curable resin droplet in the light control layer coating solution were in a dense state was removed from the hot plate, and the solvent of the light control layer coating solution was volatilized at room temperature near 23 ° C.
At this time, when the coating film is similarly observed with a digital microscope, the volatile liquid crystal drops and curable resin droplets deformed into a polygonal column structure are densely arranged in a single layer when the solvent is further evaporated and completely dried. Was confirmed.

  About the photograph taken about the coating film after drying and curing, the image for each particle is taken into a Luzex image analyzer, the maximum length of 1000 particles of each of the resin spacer and the liquid crystal drop is obtained, and the average value is obtained and compared. As a result, the difference was 0.3 μm, which was almost the same size. In addition, as long as it confirmed with the said photograph, the resin spacer and the liquid crystal drop were arrange | positioned densely by the single layer.

  The thickness of the light control layer measured by a laser 3D microscope (trade name: VK-8500, manufactured by Keyence Corporation) is 12.6 μm, the thickness of the coating layer is 1.2 μm, and the cholesteric liquid crystal drop in the light control layer The number average particle diameter of the resin spacer was about 16.3 μm, and the number average particle diameter of the resin spacer was 16.6 μm.

(Production of light modulation element)
8. The same PET substrate as the substrate used in the application of the light control layer coating solution was used as a non-display surface base, and a carbon black pigment was dispersed at a rate of 23 g / l on the surface on the ITO transparent electrode side. A 0 mass% polyvinyl alcohol aqueous solution was spin-coated to a thickness of 1.3 μm to form a light shielding layer. Further, on the formed light shielding layer, a urethane-based laminating agent (LX719 / KY-90, manufactured by Dainippon Ink & Chemicals, Inc.) was spin-coated to a thickness of 1 μm to form an adhesive layer (laminate layer).

Next, the display surface substrate manufactured as described above and the non-display surface substrate are overlapped so that the coating layer and the adhesive layer face each other, and are bonded through a laminator at 100 ° C. Finally, ultraviolet light is emitted from a high-pressure mercury lamp. Irradiation was performed to cure the curable resin droplets to form a resin spacer, whereby the light modulation element 1 was obtained. The irradiation conditions were irradiation intensity: 25 mW / cm ² (365 nm) and irradiation time: 120 seconds.

<Example 2>
In the preparation of the light control layer coating solution of Example 1, the mixing ratio of the concentrated emulsion of liquid crystal drop and the concentrated emulsion of curable resin droplets was set such that the volume ratio of the curable resin droplets to the entire volume was 2.00% by volume. Except for the above, a coating solution was prepared in the same manner as in Example 1, and the light modulation element 2 was produced in the same manner as in Example 1 using this.

  The liquid crystal drops and resin spacers in the light modulation layer of the light modulation element 2 were the same in particle size, size, arrangement state, and the like as those of the light modulation element 1 of Example 1.

<Example 3>
In the preparation of the light control layer coating solution of Example 1, the mixing ratio of the liquid crystal drop concentrated emulsion and the curable resin droplet concentrated emulsion was such that the volume ratio of the curable resin droplet to the total volume was 3.93 vol%. A coating solution was prepared in the same manner as in Example 1 except that the light modulation element 3 was produced in the same manner as in Example 1.

  The particle size, size, arrangement state, and the like of the liquid crystal drop and the resin spacer in the light control layer of the light modulation element 3 were the same as those of the light modulation element 1 of Example 1.

<Example 4>
Example 1 except that a spherical resin spacer (particle size: 10 μm) whose surface was modified with a carboxyl group was mixed with a concentrated emulsion of liquid crystal drop so that the volume ratio of the resin spacer to the total volume was 2.00% by volume. Similarly, the light modulation element 4 was obtained.

  When the light control layer was formed in the light modulation element 4, the surface of the coating film after the drying process was confirmed with the digital microscope. As a result, a resin spacer having a spherical number average particle diameter of about 10 μm was confirmed.

<Comparative Example 1>
In the preparation of the light control layer coating liquid of Example 1, except that the curable resin emulsion was not used, and only the concentrated emulsion of liquid crystal drop was used as the concentrated emulsion, and the liquid crystal volume fraction in the nonvolatile content was about 0.70. Prepared a light control layer coating solution in the same manner as in Example 1, and applied, held and dried in the same manner as in Example 1 to obtain a comparative light modulation element 5.
The particle size and the thickness of each layer of the liquid crystal drop in the light modulation element 5 were the same as those in the light modulation element 1 of Example 1.

(Measurement of display characteristics)
-Peak wavelength reflectance-
About each obtained light modulation element, the display characteristic in a planar state and a focal conic state was measured using the integrating sphere type | mold spectrocolorimeter (CM2002 type | mold, Minolta company make). Specifically, the reflectivity in the state (d8 / SCE condition) in which the specularly reflected light was removed under diffuse illumination was determined with the reflectivity of the complete diffuser as 100%. The reflectance at the peak wavelength in the planar state obtained from the reflection spectrum is shown together in FIG.

-Black reflectance after pressurization-
On the other hand, the luminous reflectance Y value (black reflectance) when pressed for 5 seconds at a pressure of 0.1 MPa (10 N / cm ² ) from the display side with a rectangular parallelepiped rubber of 10 mm square and then brought into the focal conic state. It was measured. Next, the operation of electrically resetting the liquid crystal to the focal conic state and measuring the black reflectance after pressing was performed by increasing the pressure by 0.1 MPa from 0.2 MPa to 0.6 MPa.
The results of measurement for the light modulation elements of Examples 1 and 2 and Comparative Example 1 are collectively shown in FIG.

  As shown in FIG. 7, the reflectance tends to decrease as the resin spacer concentration increases, which is considered to be due to a decrease in the liquid crystal ratio contributing to reflection. However, even in the light modulation element of Example 3 in which the resin spacer ratio was about 4% by volume, the reflectivity was not at a level causing a problem in actual use.

Further, as shown in FIG. 8, in the light modulation element of Comparative Example 1 in which the light control layer does not include the resin spacer, the black reflectance greatly increases (changes white) when the pressing force is 0.5 MPa (50 N / cm ² ). On the other hand, in the light modulation element of Example 1 in which the light control layer includes a resin spacer of about 0.8% by volume, the change in the black reflectance is not observed even when the pressing force is increased. Similar results were obtained in other examples having a high ratio.
Although not shown, the light modulation element 4 of Example 4 including a spherical resin spacer did not change without any problem. However, there was a difference when pressed with the pen tip, which did not change with the spacer of the present application, but changed white with a spherical spacer. It is estimated that a spherical spacer is not aligned with the display layer, so that partial deflection is likely to occur and local pressure is applied.

It is a schematic structure sectional view showing an example of a light modulation element of an embodiment. It is a schematic structure sectional view showing other examples of a light modulation element of an embodiment. It is a schematic structure sectional view showing other examples of a light modulation element of an embodiment. It is a schematic structure sectional view showing other examples of a light modulation element of an embodiment. It is a schematic diagram which shows an example of each process which forms a light control layer, (A1) shows an application | coating process, (A2) and (A3) show a holding process, (A4) shows a drying process, respectively. It is a schematic diagram which shows another example of each process which forms a light control layer, (B1) is a coating process, (B2) is a cooling process, (B3) and (B4) are the processes of forming a coating layer. , (B5) shows a holding step, and (B6) shows a drying step. It is a figure which shows the relationship between the resin spacer density | concentration and peak wavelength reflectance of the light modulation element of an Example. It is a figure which shows the relationship between the pressing force of the light modulation element of an Example, and a black reflectance. It is a schematic diagram which shows the arrangement | sequence state of a cholesteric liquid crystal, (A) shows a planar state, (B) shows a focal conic state, (C) shows a homeotropic state. It is a graph which shows the electro-optic response of the cholesteric liquid crystal which has positive dielectric anisotropy.

Explanation of symbols

10, 23, 24 Light modulation element 11, 21 Support substrate 12, 22 Electrode 13 Non-display surface substrate 14 Light shielding layer 16 Adhesive layer 20 Display surface substrate 30, 31 Light control layer 32, 36, 74 Liquid crystal drop 33, 35 Resin spacer 34 Gelatin (polymer binder)
60 Substrate 62 Electrode 64 Edge coater 70, 71, 73, 75 Coating layer 72 Curable resin droplets 80, 81, 84 Coating layer

Claims (9)

A pair of substrates arranged such that at least one of them has translucency and electrodes provided on the surface thereof are opposed to each other;
A light modulation element comprising a light control layer provided between the pair of substrates and including at least a liquid crystal drop or a liquid crystal microcapsule, a polymer binder, and a resin spacer.   The light modulation element according to claim 1, wherein the resin spacer has a polygonal column shape.   The light modulation element according to claim 1, wherein the liquid crystal drop or the liquid crystal microcapsule is also in a polygonal column shape.   4. The light modulation element according to claim 1, wherein a maximum length difference between the liquid crystal drop or the liquid crystal microcapsule and the resin spacer is within ± 50%.   5. The light modulation element according to claim 1, wherein the liquid crystal drop or the liquid crystal microcapsule and the resin spacer are arranged in a single layer and densely.   The light modulation element according to claim 1, wherein a coating layer is provided on the light control layer. A pair of substrates disposed so that at least one of them has a light-transmitting property and electrodes provided on the surface thereof are opposed to each other; and provided between the pair of substrates; at least a liquid crystal drop or a liquid crystal microcapsule; a polymer binder; A light modulation layer comprising a resin spacer, and a step of providing the light modulation layer,
On the substrate, a coating step of coating a light control layer coating liquid in which liquid crystal drops or liquid crystal microcapsules and curable resin droplets are dispersed in a solution containing a polymer binder and a solvent;
The coating layer formed by the coated light control layer coating solution is predetermined in an atmosphere at a temperature higher than the freezing point of the polymer binder and the same as or close to the saturated vapor pressure of the solvent. Holding process for holding time;
A drying step of evaporating and drying the solvent in the coating layer at a temperature below the freezing point of the polymer binder;
A method for manufacturing a light modulation element, comprising:   Furthermore, the manufacturing method of the light modulation element of Claim 7 which has a coating layer formation process which forms a coating layer on the said application layer.   The method for manufacturing a light modulation element according to claim 7, wherein a difference in specific gravity between the liquid crystal and the curable resin is −0.5 or more and +0.5 or less.

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