JP7260030B1 - dimmer - Google Patents

Abstract

A light control device capable of increasing contrast is provided. The light control sheet includes two light control sheets that reversibly change from transparent to opaque, one light control sheet is superimposed on the other light control sheet, and each light control sheet has a state of being opaque at the same time. In the light control device, the light control sheet includes a transparent polymer layer having voids, and a liquid crystal composition containing a liquid crystal compound and a dichroic dye and filling the voids. haze is 79% or more. [Selection drawing] Fig. 1

Description

TECHNICAL FIELD The present disclosure relates to a light control device having a light control sheet that reversibly changes from transparent to opaque.

A normal type light control sheet has a light control layer containing a liquid crystal compound. A driving signal for the light control sheet forms an electric field in the light control layer so as to align the long axis directions of the liquid crystal compounds. As a result, the normal type light control sheet reversibly changes from opaque when not driven to transparent when driven.

A reverse type light control sheet includes a light control layer containing a liquid crystal compound and an alignment layer that applies an alignment control force to the liquid crystal compound. An example of the alignment regulating force is to regulate the alignment of the liquid crystal compound so that the long axis direction of the liquid crystal compound is substantially perpendicular to the surface direction of the alignment layer when the light control sheet is not driven. A drive signal for the light control sheet forms an electric field against the alignment control force so that the major axis direction of the liquid crystal compound is substantially parallel to the plane direction of the alignment layer. As a result, the reverse type light control sheet reversibly changes from transparent when not driven to opaque when driven (see, for example, Patent Document 1).

JP 2019-194654 A

A light control sheet comprising a transparent polymer layer and particles of a liquid crystal composition interspersed in the transparent polymer layer achieves opacity through scattering of the particles. The addition of dichroic dyes in the granules adds color to opacity when actuated while achieving colorless transparency when not actuated.

On the other hand, excessively increasing the compounding ratio of the dichroic dye increases the degree of coloration in the opaque state, but weakens the dispersion of the particles and lowers the responsiveness of the liquid crystal compound. As a result, dimmers containing dichroic dyes in the liquid crystal composition, whether normal or reversed, can enhance the contrast of the dimmer, i.e. the difference in light transmission between transparent and opaque. There is a new demand to increase the

A light control device for solving the above problems includes two light control sheets that reversibly change from transparent to opaque, one said light control sheet is superimposed on the other said light control sheet, and each light control sheet is opaque at the same time, wherein the light control sheet contains a transparent polymer layer having voids, a liquid crystal compound and a dichroic dye, and a liquid crystal composition filling the voids and the haze when opaque is 79% or more.

As mentioned above, the contrast of a dimmer is the ratio of the total light transmission when clear to the total light transmission when opaque. The total transmitted light of each light control sheet constituting the light control device includes straight transmitted light that passes through the light control sheet without being scattered by the light control sheet and scattered light scattered by the light control sheet. The total light transmittance of the light control sheet depends on the sum of the amount of straight transmitted light and the amount of scattered light. The haze of a light control sheet is the ratio of diffuse transmittance to total light transmittance. That is, the haze of the light control sheet depends on the amount of scattered light with respect to the sum of the amount of straight transmitted light and the amount of scattered light. The total light transmittance and the haze are optical characteristics that can vary independently of each other, such that even if the sum of the amount of straight transmitted light and the amount of scattered light is constant, the amount of scattered light changes with respect to the sum.

Increasing the compounding ratio of the dichroic dye in the liquid crystal composition simply reduces the amount of scattered light. By increasing the compounding ratio of the dichroic dye, the total light transmittance is reduced by the amount of the decrease in the amount of scattered light, thereby making it possible to improve the contrast. However, the compounding ratio of the dichroic dye is actually set to approximately the upper limit within the range in which the responsiveness of the liquid crystal compound is obtained. Ultimately, increasing the compounding ratio of the dichroic dye has limitations in terms of increasing the contrast.

On the other hand, based on the dichroic ratio, dichroic dyes exhibit high absorbance for scattered light and low absorbance for straight transmitted light. The absorbance of such dichroic dyes increases steeply exponentially with the optical path length as a variable. Promoting the scattering of straight transmitted light in the light control sheet lowers the total light transmittance in the opaque state, thereby making it possible to improve the contrast. However, in order to sharply increase the light absorption by the dichroic dye, it is necessary not only to simply promote the scattering of the straight transmitted light, but also to reduce the light scattered at the interface between the transparent polymer layer and the liquid crystal composition to the dichroic dye. It is required to increase the scattering to the extent that .

The inventors of the present application, while earnestly studying the relationship between the contrast of the light control device and the optical characteristics of the light control sheet, found that the haze of the light control sheets stacked on each other has a range in which the contrast is sharply increased. I found Further, according to the above configuration, since the opaque haze of each light control sheet constituting the light control device is 79% or more, the contrast in the light control device can be greatly increased.

A light control device for solving the above problems includes two light control sheets that reversibly change from transparent to opaque, one said light control sheet is superimposed on the other said light control sheet, and each light control sheet is opaque at the same time, wherein the light control sheet contains a transparent polymer layer having voids, a liquid crystal compound and a dichroic dye, and a liquid crystal composition filling the voids and an absorbance difference, which is a value obtained by subtracting the average absorbance of the liquid crystal composition from the absorbance of the light control sheet in the opaque state, is 0.4 or more.

A light control device for solving the above problems includes two light control sheets that change from transparent to opaque, one said light control sheet is superimposed on the other said light control sheet, and each light control sheet is opaque at the same time. wherein the light control sheet includes a transparent polymer layer having voids, and a liquid crystal composition containing a liquid crystal compound and a dichroic dye and filling the voids. The absorbance difference, which is the value obtained by subtracting the horizontal absorbance of the liquid crystal composition from the absorbance of the light control sheet in the opaque state, is 0.1 or more.

As described above, the high absorbance of scattered light based on the dichroic ratio, the exponential increase in absorbance with the optical path length as a variable, and the long optical path length of the scattered light combine to promote the scattering of straight light. Allows for improved contrast. In this case, it is required to increase scattering to the extent that the light scattered at the interface between the transparent polymer layer and the liquid crystal composition reaches the dichroic dye.

Here, the absorbance of the opaque light control sheet reflects the fact that the light scattered at the interface between the transparent polymer layer and the liquid crystal composition is absorbed by the dichroic dye. On the other hand, the absorbance of the liquid crystal composition when opaque does not reflect the extension of the optical path length due to scattering, ie, the increase in absorption due to the extension of the optical path length. The absorbance difference, which is a value obtained by subtracting the absorbance of the liquid crystal composition that can be regarded as being opaque from the absorbance when opaque, indicates the amount of increase in absorption due to the extension of the optical path length.

The inventors of the present application, while earnestly studying the relationship between the contrast of the light control device and the optical characteristics of the light control sheet, have found that the contrast is sharply increased in the absorbance difference of the light control sheets stacked on each other. Found the range. Further, according to the above configuration, since the difference in absorbance between the absorbance of each light control sheet when opaque and the average absorbance of the liquid crystal composition is 0.4 or more, it is possible to greatly increase the contrast in the light control device. Become. In addition, according to the above configuration, since the difference in absorbance between the absorbance of each light control sheet when opaque and the horizontal absorbance of the liquid crystal composition is 0.1 or more, it is possible to greatly increase the contrast in the light control device. Become.

In the above light control device, the light control sheet may have a total light transmittance of 25% or less when the light control sheet is opaque. Further, in the light control device, the light control sheet may have a diffuse transmittance of 16% or less when the light control sheet is opaque. In the light control device, the light control sheet may have a parallel light transmittance of 5% or less when the light control sheet is opaque. In the light control device, the light control sheet may have a clarity of 95% or less when opaque. According to each of these configurations, the effectiveness of obtaining the effects described above is increased.

In the light control device, the light control sheet includes a first transparent electrode layer, a second transparent electrode layer, a first orientation layer positioned between the first transparent electrode layer and the transparent polymer layer, A second alignment layer positioned between the second transparent electrode layer and the transparent polymer layer may be provided, and the thickness of the light control sheet may be 10 μm or less.

A reverse type light control sheet that uses an orientation regulating force is thinner than a normal type light control sheet by the extent that the orientation regulating force is applied throughout the thickness direction. Such a reverse type light control sheet is strongly desired to have higher contrast than a normal type light control sheet. In this respect, according to the above configuration, it is also possible to increase the contrast in the light control device using the reverse type light control sheet.

According to the present disclosure, it is possible to increase the contrast of the dimmer.

FIG. 1 is a cross-sectional view showing the layered structure of the light control device. FIG. 2 is a cross-sectional view showing the layer structure of the light control sheet. FIG. 3 is a table showing the optical properties of the light control sheets of test examples. FIG. 4 is a table showing the optical properties of the light control sheets of test examples. FIG. 5 is a graph showing the relationship between haze and contrast. FIG. 6 is a graph showing the relationship between haze and contrast. FIG. 7 is a graph showing the relationship between absorbance difference and contrast. FIG. 8 is a graph showing the relationship between absorbance difference and contrast. FIG. 9 is a graph showing the relationship between transmittance and contrast.

An embodiment of a light control device will be described with reference to FIGS. 1 to 9. FIG.
A light control sheet that constitutes a light control device is attached to, for example, a window of a moving object such as a vehicle or an aircraft. Light control sheets are attached to, for example, windows of various buildings such as houses, stations, and airports, partitions installed in offices, show windows installed in stores, screens for projecting images, and the like.

The shape of the light control sheet may be planar or curved. The type of light control sheet may be a normal type that changes from opaque to transparent by inputting a drive signal, or a reverse type that changes from transparent to opaque by inputting a drive signal. The light control device includes one or more light control sheets. The light control sheet provided in the light control device may be a single layer body composed of one light control sheet, or may be a laminate in which one light control sheet is stacked on another light control sheet.

An example in which the light control sheet provided in the light control device is a laminate composed of two reverse type light control sheets will be described below.
[Dimmer]
An example of a light control device will be described with reference to FIGS. 1 and 2. FIG.

As shown in FIG. 1 , the light control device 10 includes a light control section 11 and a driving section 12 . The light control section 11 includes two reverse type light control sheets. One light control sheet comprises a light control layer 21 , a first alignment layer 22 , a second alignment layer 23 , a first transparent electrode layer 24 and a second transparent electrode layer 25 . The first alignment layer 22 and the second alignment layer 23 sandwich the light control layer 21 in the thickness direction of the light control layer 21 . The dimming layer 21 is located between the first alignment layer 22 and the second alignment layer 23 . The light control layer 21 is in contact with the first alignment layer 22 and the second alignment layer 23 . A pair of alignment layers 22 and 23 are sandwiched between the first transparent electrode layer 24 and the second transparent electrode layer 25 in the thickness direction of the light control layer 21 . The light modulating layer 21 is positioned between the transparent electrode layers 24 and 25 . The first transparent electrode layer 24 contacts the first alignment layer 22 . The second transparent electrode layer 25 contacts the second alignment layer 23 . The light control sheet comprises a first transparent substrate 26 supporting a first transparent electrode layer 24 . The light control sheet includes a second transparent substrate 27 supporting a second transparent electrode layer 25 .

The light control device 10 includes a first electrode 24A attached to a portion of the first transparent electrode layer 24 and a second electrode 25A attached to a portion of the second transparent electrode layer 25 . The light control device 10 includes a first wiring 24B connected to the first electrode 24A and a second wiring 25B connected to the second electrode 25A. The first electrode 24A is connected to the driving section 12 by a first wiring 24B. The second electrode 25A is connected to the driving section 12 by a second wiring 25B.

The light control device 10 includes two light control units. The two dimming units consist of a first dimming unit 11UN1 and a second dimming unit 11UN2. One light control unit includes one light control sheet, first electrode 24A, first wiring 24B, second electrode 25A, and second wiring 25B. One light control unit is a repeat unit in the thickness direction of the light control sheet in the light control device 10 .

The first dimming unit 11UN1 has the same structure as the second dimming unit 11UN2. The second transparent base material 27 of the second light control unit 11UN2 overlaps the first transparent base material 26 of the first light control unit 11UN1. The second transparent base material 27 of the second light control unit 11UN2 is adhered to the first transparent base material 26 of the first light control unit 11UN1 via an optical transparent adhesive. A light control device 10 composed of a plurality of light control units makes the optical path length of light entering the light control device 10 longer than that of the light control device 10 composed of one light control unit. .

The dimming device 10 may include two drive units 12 . One drive unit 12 inputs a drive signal to the first light control unit 11UN1 and the second light control unit 11UN2. The other driving section 12 inputs a driving signal to the second dimming unit 11UN2. The two drive units 12 make the first dimming unit 11UN1 and the second dimming unit 11UN2 opaque at the same time. The two drive units 12 make the first light control unit 11UN1 and the second light control unit 11UN2 transparent at the same time. The two drive units 12 may separately make the first dimming unit 11UN1 and the second dimming unit 11UN2 opaque. The dimming device 10 may have one drive unit 12 . One drive unit 12 inputs a drive signal to the first light control unit 11UN1 and inputs a drive signal to the second light control unit 11UN2. One driving section 12 makes the first dimming unit 11UN1 and the second dimming unit 11UN2 opaque at the same time. One driving section 12 makes the first light control unit 11UN1 and the second light control unit 11UN2 transparent at the same time. One driving section 12 may separately make the first dimming unit 11UN1 and the second dimming unit 11UN2 opaque.

[Light control sheet]
As shown in FIG. 2, the light control layer 21 includes a transparent polymer layer 21P and a liquid crystal composition 21LC.

The transparent polymer layer 21P has optical transparency to transmit visible light. The transparent polymer layer 21P has many voids 21D. The transparent polymer layer is a cured polymerizable composition. The transparent polymer layer may be a cured product of a photocurable compound or a cured product of a thermosetting compound. The liquid crystal composition 21LC fills the inside of the gap 21D.

An example of the optical compound forming the transparent polymer layer 21P is at least one selected from the group consisting of acrylate compounds, methacrylate compounds, styrene compounds, thiol compounds, and oligomers of these compounds. Acrylate compounds include monoacrylate compounds, diacrylate compounds, triacrylate compounds, and tetraacrylate compounds. Examples of acrylate compounds are butyl ethyl acrylate, ethylhexyl acrylate, cyclohexyl acrylate. Examples of methacrylate compounds are dimethacrylate compounds, trimethacrylate compounds, tetramethacrylate compounds. Examples of methacrylate compounds are N,N-dimethylaminoethyl methacrylate, phenoxyethyl methacrylate, methoxyethyl methacrylate, tetrahydrofurfuryl methacrylate. Examples of thiol compounds are 1,3-propanedithiol, 1,6-hexanedithiol. Examples of styrene compounds are styrene and methylstyrene.

The liquid crystal composition 21LC contains a liquid crystal compound LCM and a dichroic dye. The liquid crystal composition 21LC contains, in addition to the liquid crystal compound LCM and the dichroic dye, a polymerizable composition for forming the transparent polymer layer 21P, a plasticizer for reducing the viscosity of the liquid crystal composition 21LC, and the like. good too. The ratio of the mass of the liquid crystal composition 21LC to the total mass of the light control layer 21 may be 30% by mass or more and 60% by mass or less. Liquid crystal composition 21LC further contains a reactive mesogenic compound. When the liquid crystal compound LCM is vertically aligned, the reactive mesogenic compound is also vertically aligned. The vertical alignment of the liquid crystal compound LCM is facilitated by the networking of the vertically aligned reactive mesogenic compounds. That is, the alignment control force of the networked reactive mesogenic compound promotes vertical alignment of the liquid crystal compound LCM.

The type of the light control layer 21 is a polymer dispersion type. The polymer-dispersed light control layer 21 includes a transparent polymer layer 21P defining a large number of voids 21D. Liquid crystal composition 21LC is held in voids 21D dispersed in transparent polymer layer 21P. The polymer dispersion type light control layer 21 may be a polymer network type light control layer 21 or a capsule type light control layer 21 . The polymer network type light control layer 21 includes a transparent polymer layer 21P having a three-dimensional network structure, and holds a liquid crystal composition 21LC in interconnected network voids 21D. The capsule-shaped light control layer 21 holds the liquid crystal composition 21LC in the capsule-shaped voids 21D dispersed in the transparent polymer layer 21P.

Examples of liquid crystal compound LCM are Schiff base, azo, azoxy, biphenyl, terphenyl, benzoate, tolane, pyrimidine, cyclohexanecarboxylate, phenylcyclohexane, and dioxane. is at least one selected from the group

The NI point of the liquid crystal compound LCM is the temperature at which the liquid crystal compound LCM undergoes phase transition from the nematic phase (N phase) to the isotropic liquid phase (I phase). The NI point of the liquid crystal compound LCM indicates the degree to which the anisotropy of the liquid crystal compound LCM disappears at ambient temperature. The NI point of the liquid crystal compound LCM not a little reflects the degree of intermolecular interaction in the liquid crystal compound LCM. When the liquid crystal compound LCM is a combination of two or more kinds of compounds, the NI point of the liquid crystal compound LCM is the weighted average value of the NI points of each compound weighted by the compounding ratio of each compound. The NI point of the liquid crystal compound LCM can be increased or decreased depending on the composition of two or more types of liquid crystal compounds having mutually different NI points. When it is required to enhance the alignment order of the liquid crystal compound LCM at a high ambient temperature such as 100°C, the NI point is preferably 100°C or higher. When the polymerizable composition for forming the transparent polymer layer 21P and the liquid crystal compound LCM are required to be more uniform, the NI point is preferably 145° C. or lower.

The CN point of the liquid crystal compound LCM is the temperature at which the liquid crystal compound LCM undergoes a phase transition from the crystalline phase (C phase) to the nematic phase (N phase). The CN point of the liquid crystal compound LCM indicates the degree to which the fluidity of the liquid crystal compound LCM disappears at the ambient temperature. When the liquid crystal compound LCM is a combination of two or more types of compounds, the CN point of the liquid crystal compound LCM is lower than the weighted average value of the CN points of each compound weighted by the compounding ratio of each compound. The CN point of the liquid crystal compound LCM can be raised or lowered depending on the composition of two or more compounds having mutually different NI points. When it is required to improve the fluidity of the liquid crystal compound LCM at an ambient temperature as low as -20°C, the CN point is preferably 25°C or lower, more preferably 0°C or lower.

A refractive index difference Δn (Δn=abnormal refractive index ne−ordinary refractive index no) between the major axis direction and the minor axis direction of the liquid crystal compound LCM indicates the degree of attraction or repulsion in the liquid crystal compound LCM. The refractive index difference Δn of the liquid crystal compound LCM is the difference in the refractive index for visible light with a wavelength of 650 nm, and indicates the difference in the degree of scattering of the visible light between when the drive signal is supplied and when it is stopped. When the liquid crystal compound LCM is a combination of two or more compounds, the upper limit value of the refractive index difference Δn of the liquid crystal compound LCM is the upper limit value obtained from the refractive index differences Δn of all the compounds. The lower limit of the refractive index difference Δn of the liquid crystal compound LCM is the lower limit obtained from the refractive index differences Δn of all the compounds.

When it is required to improve the alignment controllability of the liquid crystal compound LCM at high ambient temperature, it is preferable that the lower limit of the refractive index difference Δn is high. If a high haze difference between transparent and opaque is required, a high lower limit for the refractive index difference Δn is preferred. When it is required to enhance the alignment controllability of the liquid crystal compound LCM at a high ambient temperature such as 100° C., the lower limit of the refractive index difference Δn of the liquid crystal compound LCM is preferably 0.05, and 0.1. It is more preferable to have When it is required to increase the haze difference, the lower limit of the refractive index difference Δn of the liquid crystal compound LCM is preferably 0.05, more preferably 0.1.

A dichroic dye increases the absorbance of visible light in the direction of the long molecular axis more than the absorbance of visible light in the direction of the short axis of the molecule. It is driven by a guest-host type with a liquid crystal compound LCM as a host. The dichroic dye reversibly changes from transparent to colored in accordance with the orientation change of the liquid crystal compound LCM. The liquid crystal composition 21LC contains one dichroic dye or a combination of two or more dichroic dyes. The combination of dichroic dyes is appropriately adjusted so that the color exhibited by the combination of dichroic dyes is the color exhibited when the light control sheet is opaque.

The color of the opaque light control sheet may be black or chromatic black. An example of a dichroic dye is to change the chromaticity a* of the CIE1976 (L*a*b*) color system in an opaque light control sheet to -15 or more and 15 or less, and the chromaticity b* to -15 or more and 15 or less. do. Chromaticity a* and chromaticity b* in the CIE1976 (L*a*b*) color system are CIE1976 (L*a*b* ) is specified according to the method of calculating the color coordinates of the color space. The ratio of the mass of the dichroic dye to the total mass of the dimming layer 21 is the compounding ratio of the dichroic dye. An example of the blending ratio of the dichroic dye is 1% by mass or more and 5% by mass or less. Increasing the compounding ratio of the dichroic dye increases the contrast of the light control device 10, but decreases the responsiveness of the liquid crystal compound LCM. From the viewpoint of increasing the contrast of the light control device 10, the compounding ratio of the dichroic dye is preferably the upper limit within the range in which the responsiveness of the liquid crystal compound LCM can be obtained.

A dichroic dye is driven by a guest-host type with a liquid crystal compound as a host, thereby exhibiting a specific color. The dichroic dye is at least one selected from the group consisting of polyiodine, azo compounds, anthraquinone compounds, naphthoquinone compounds, azomethine compounds, tetrazine compounds, quinophthalone compounds, merocyanine compounds, perylene compounds, and dioxazine compounds. A dichroic dye is a single compound or a combination of two or more compounds. When the total mass of the light control layer 21 is set to 100% by mass, the mass of the dichroic dye may be 1% by mass or more and 5% by mass or less, and be 1% by mass or more and 3.5% by mass or less. is preferred. When it is required to increase the light resistance and the dichroic ratio, the dichroic dye is at least one selected from the group consisting of an azo compound and an anthraquinone compound, more preferably an azo compound. be.

The light control layer 21 may contain a spacer. The spacers are distributed throughout the light modulating layer 21 . The spacer defines the thickness of the light control layer 21 around the spacer and makes the thickness of the light control layer 21 uniform. The spacers may be bead spacers or photospacers formed by exposure and development of a photoresist. The spacer may be colorless and transparent, or colored and transparent. When it is required to suppress the visibility of the spacer when the light control sheet is opaque, or to suppress the brightness of the color when the light control sheet is opaque, the color of the spacer is the same color as when the light control sheet is opaque. is preferably

An example of the thickness of the light control layer 21 is 2 μm or more and 30 μm or less. When it is required to strengthen the action of the alignment regulating force on the liquid crystal compound LCM, the thickness of the light control layer 21 is preferably 5 μm or more and 25 μm or less. When the transparent polymer layer 21P is formed by phase separation, the thickness of the light modulating layer 21 of 5 μm or more enables uneven distribution of the voids 21D having a diameter of 1 μm or less. Also, in the thickness direction of the light-modulating layer 21 , regions having different densities of the liquid crystal composition 21LC can be generated in the light-modulating layer 21 . Since the thickness of the light control layer 21 is 25 μm or less, when the coating liquid containing the liquid crystal compound LCM and the polymerizable composition is exposed to light during the manufacturing of the light control layer 21, the liquid crystal compound LCM and the transparent polymer Appropriate phase separation with layer 21P is possible.

The first alignment layer 22 exerts an alignment regulating force on the liquid crystal compound LCM from the surface of the light control layer 21 in contact with the first alignment layer 22 . The second alignment layer 23 exerts an alignment regulating force on the liquid crystal compound LCM from the surface of the light control layer 21 in contact with the second alignment layer 23 . The alignment layers 22 and 23 have optical transparency to transmit visible light. An example of the alignment layers 22, 23 is a vertical alignment layer. The alignment regulating force applied by the vertical alignment layer aligns the long axis direction of the liquid crystal compound LCM so that it is perpendicular to the plane of the alignment layers 22 and 23 that is in contact with the light control layer 21 . The alignment layers 22 and 23 are arranged such that the long axis of the liquid crystal compound LCM is tilted several degrees with respect to the vertical in the range where the long axis of the liquid crystal compound LCM is determined to be substantially perpendicular to the transparent electrode layers 24 and 25 . The LCM may be oriented. An example of the thickness of the alignment layers 22 and 23 is 0.02 μm or more and 0.5 μm or less.

Materials constituting the alignment layers 22 and 23 may be an organic compound, an inorganic compound, or an organic-inorganic composite material thereof. The material forming the first alignment layer 22 and the material forming the second alignment layer 23 may be the same or different. An example of the organic compound forming the alignment layers 22 and 23 is at least one selected from the group consisting of polyimide, polyamide, polyvinyl alcohol, and cyanide compounds. An example of the inorganic compound forming the alignment layers 22 and 23 is silicon oxide or zirconium oxide. The organic-inorganic composite material forming the alignment layers 22, 23 is silicone with an inorganic structure and an organic structure.

The first transparent electrode layer 24 and the second transparent electrode layer 25 form an electric field in the thickness direction of the light control layer 21 by inputting a drive signal. The transparent electrode layers 24 and 25 have optical transparency to transmit visible light. An example of the thickness of the transparent electrode layers 24 and 25 is 0.005 μm or more and 0.1 μm or less.

Materials constituting the transparent electrode layers 24 and 25 may be inorganic compounds, organic compounds, or organic-inorganic composite materials. An example of the inorganic compound forming the transparent electrode layers 24 and 25 is at least one selected from the group consisting of indium tin oxide, fluorine-doped tin oxide, tin oxide, and zinc oxide. An example of the organic compound forming the transparent electrode layers 24, 25 is poly(3,4-ethylenedioxythiophene). The organic-inorganic composite material forming the transparent electrode layers 24 and 25 is an organic compound containing metal nanowires.

A first transparent substrate 26 supports the first transparent electrode layer 24 . A second transparent substrate 27 supports the second transparent electrode layer 25 . The transparent substrates 26 and 27 may be flexible enough to follow the curved surface to which the light control sheet is attached, or may be a rigid body that does not deform under its own weight. At least one of the transparent substrates 26 and 27 is attached to an object to which the light control device 10 is applied. An example of the thickness of the transparent substrates 26 and 27 is 15 μm or more and 250 μm or less. When the transparent substrates 26 and 27 have a thickness of 15 μm or more, the mechanical durability of the light control sheet and the chemical durability of the light control layer 21 are enhanced. The fact that the thickness of the transparent substrates 26 and 27 is 250 μm or less enables roll-to-roll production of the light control sheet.

The material forming the transparent substrates 26 and 27 may be an organic compound or an inorganic compound. An example of the organic compound forming the transparent substrates 26, 27 is at least one selected from the group consisting of polyester, polyacrylate, polycarbonate, and polyolefin. An example of the inorganic compound forming the transparent substrates 26 and 27 is at least one selected from the group consisting of silicon dioxide, silicon oxynitride, and silicon nitride. The adhesive applied to the transparent substrates 26 and 27 is a transparent adhesive and insulating resin. The adhesive for the transparent substrates 26 and 27 is, for example, optical clear adhesive (OCA).

The electrodes 24A and 25A may be flexible printed circuit boards or metal tapes. The electrodes 24A, 25A may be attached to the transparent electrode layers 24, 25 by a conductive adhesive layer. The drive unit 12 inputs drive signals to the light control layer 21 through the transparent electrode layers 24 and 25 . The drive signal may be an AC voltage signal or a DC voltage signal.

The light control layer 21 changes the orientation of the liquid crystal compound LCM by changing the electric field formed between the two transparent electrode layers 24,25. A change in orientation in the liquid crystal compound LCM changes the degree of scattering, absorption, and transmission of visible light entering the light control layer 21 .

Each unit 11UN1, 11UN2 has an orientation regulating force of the orientation layers 22, 23, etc. when an electric field is formed in the light control layer 21, that is, when a potential difference is generated between the two transparent electrode layers 24, 25. drives the liquid crystal compound LCM against and has a relatively high haze. Each of the units 11UN1 and 11UN2 becomes cloudy, that is, opaque, due to scattering due to the refractive index difference between the transparent polymer layer 21P and the liquid crystal compound LCM when a voltage is applied to the light modulating layer 21. The dichroic dye follows the driving of the liquid crystal compound LCM and orients to increase the absorbance. As a result, when voltage is applied to the light control layer 21, the units 11UN1 and 11UN2 become black and opaque.

Each unit 11UN1, 11UN2 regulates the alignment of the alignment layers 22, 23, etc. when no voltage is applied to the light modulating layer 21, that is, when no potential difference is generated between the two transparent electrode layers 24, 25. It follows the force and has a lower haze than when a potential difference is present. Each of the units 11UN1 and 11UN2 reduces the refractive index difference between the transparent polymer layer 21P and the liquid crystal compound LCM when no voltage is applied to the light control layer 21, thereby scattering light in the light control layer 21. suppress. The dichroic dye follows the orientation of the liquid crystal compound LCM and is oriented so as to reduce the absorbance. As a result, when no voltage is applied to the dimming layer 21, the units 11UN1 and 11UN2 are colorless and transparent.

A state in which the units 11UN1 and 11UN2 are black and opaque is a dark state of the light control device 10 . The state in which the units 11UN1 and 11UN2 are colorless and transparent is the bright state of the light control device 10. FIG. The total light transmittance of the dimming device 10 in the dark state is lower than the total light transmittance of the dimming device 10 in the bright state. The light control device 10 may have translucence, in which the first light control unit 11UN1 is black and opaque, and the second light control unit 11UN2 is colorless and transparent. The light control device 10 may have translucence, in which the second light control unit 11UN2 is black and opaque, and the first light control unit 11UN1 is colorless and transparent.

[Optical Characteristics of Light Control Sheet]
Each light control sheet of the light control device 10 satisfies at least one of Condition 1 and Condition 2 below. Satisfying at least one of condition 1 and condition 2 may be satisfying condition 1, satisfying condition 2, or satisfying both condition 1 and condition 2. Furthermore, when it is required to increase the contrast of the light control device, each light control sheet of the light control device 10 preferably satisfies at least one of conditions 3 to 6 below. Satisfying at least one of conditions 3 to 6 may be one selected from conditions 3 to 6, or a combination of two or more selected from conditions 3 to 6. Each light control sheet of the light control device 10 may satisfy condition 8 below instead of or together with condition 2 below.

(Condition 1) Each light control sheet has a haze of 79% or more when opaque.
(Condition 2) The absorbance difference, which is the value obtained by subtracting the average absorbance of the liquid crystal composition 21LC from the absorbance of each light control sheet when opaque, is 0.4 or more.

(Condition 3) Each light control sheet has a total light transmittance of 25% or less when opaque.
(Condition 4) Each light control sheet has a diffuse transmittance of 16% or less when opaque.
(Condition 5) Each light control sheet has a parallel line transmittance of 5% or less when opaque.

(Condition 6) Each light control sheet has a clarity of 95% or less when opaque.
(Condition 8) The absorbance difference, which is the value obtained by subtracting the horizontal absorbance of the liquid crystal composition 21LC from the absorbance of each light control sheet in the opaque state, is 0.1 or more.

Haze is obtained by a measurement method according to ASTM D 1003-00. A haze measuring instrument is, for example, BYK haze-gard i indtrument (manufactured by BYK Gardner). The light rays included in the light flux incident on the light control sheet in haze measurement are rectilinear rays. The maximum angle between the light rays included in the luminous flux incident on the light control sheet and the optical axis of the luminous flux is less than 3°. The light control sheet is fixed so that the surface of the light control sheet and the luminous flux incident on the surface are substantially perpendicular to each other within ±2°.

Of the transmitted light that has passed through the light control sheet, light deviating from the light flux incident on the light control sheet by ±2.5° or more is wide-angle scattered light. Haze is the percentage of wide-angle scattered light due to forward scattering in the transmitted light that has passed through the light control sheet. The diffuse transmittance is the percentage of wide-angle scattered light due to forward scattering in the incident light incident on the light control sheet.

Of the transmitted light passing through the light control sheet, the light that deviates from the light flux incident on the light control sheet by less than ±2.5° is parallel transmitted light. The parallel light transmittance is the percentage of light transmitted through the light control sheet due to forward scattering of light incident on the light control sheet. Total light transmittance is the sum of diffuse transmittance and parallel line transmittance.

Of the transmitted light that passes through the light control sheet, the light that does not deviate from the luminous flux incident on the light control sheet is rectilinear transmitted light. Light that deviates from the straight transmitted light by less than ±2.5° is the parallel transmitted light described above. Clarity is calculated based on the following formula (1) from the light quantity LC of straight transmitted light and the light quantity LR of parallel transmitted light.

100 × (LR-LC) / (LR + LC) ... formula (1)
Total light transmittance, diffuse transmittance, parallel line transmittance, and clarity are obtained by measurements according to ASTM D 1003-00.

Absorbance is obtained by a measuring method using an absorptiometer based on JIS K 0115:2004. The light source of the absorption photometer is a white LED that emits visible light of 380 nm or more and 780 nm or less. The photometric part of the absorptiometer detects light intensity over the entire visible light range from 380 nm to 780 nm.

The contrast of the dimmer 10 is the ratio of the total light transmittance when clear to the total light transmittance when opaque. That is, the contrast of the dimmer 10 is the ratio of the total light transmittance in the bright state to the total light transmittance in the dark state. The total transmitted light of each light control sheet constituting the light control device 10 includes straight transmitted light passing through the light control sheet without being scattered by the light control sheet and scattered light scattered by the light control sheet. The total light transmittance of the light control sheet depends on the sum of the amount of straight transmitted light and the amount of scattered light. The haze of a light control sheet is the ratio of diffuse transmittance to total light transmittance. That is, the haze of the light control sheet depends on the amount of scattered light with respect to the sum of the amount of straight transmitted light and the amount of scattered light. Even if the sum of the amount of straight transmitted light and the amount of scattered light is constant, the total light transmittance and the haze are adjusted so that the amount of scattered light changes with respect to the sum of the amount of straight transmitted light and the amount of scattered light. is an optical property that can vary from one to another.

Increasing the compounding ratio of the dichroic dye in the liquid crystal composition 21LC simply reduces the amount of scattered light. By increasing the compounding ratio of the dichroic dye, the total light transmittance is lowered by the amount of the decrease in the amount of scattered light, thereby making it possible to improve the contrast. However, the compounding ratio of the dichroic dye is actually set to approximately the upper limit within the range in which the responsiveness of the liquid crystal compound LCM can be obtained. Ultimately, increasing the compounding ratio of the dichroic dye has limitations in terms of increasing the contrast of the light control device 10 .

On the other hand, as described above, the dichroic dye exhibits high absorbance for scattered light and low absorbance for straight transmitted light based on the dichroic ratio. The absorbance of such dichroic dyes increases steeply exponentially with the optical path length as a variable. Promoting the scattering of straight transmitted light in the light control sheet lowers the total light transmittance in the opaque state, thereby making it possible to improve the contrast. However, in order to steeply increase the light absorption by the dichroic dye, it is necessary not only to simply promote the scattering of straight transmitted light, but also to dichroically light scattered at the interface between the transparent polymer layer 21P and the liquid crystal composition 21LC. It is required to increase the scattering to the extent that it reaches the sexual pigment.

The inventors of the present application, while earnestly studying the relationship between the contrast of the light control device 10 and the optical characteristics of the light control sheets, have found that the contrast is sharply increased in the haze of the light control sheets that are superimposed on each other. Found the range. If the light control device 10 satisfies the condition 1 described above, the haze of each light control sheet when opaque is 79% or more, so the contrast in the light control device 10 is greatly increased.

The absorbance of the opaque light control sheet reflects the fact that the light scattered at the interface between the transparent polymer layer 21P and the liquid crystal composition 21LC is absorbed by the dichroic dye. On the other hand, the absorbance of the liquid crystal composition 21LC itself, which is regarded as being opaque, does not reflect the extension of the optical path length due to scattering, that is, the increase in absorption due to the extension of the optical path length. The absorbance difference, which is the value obtained by subtracting the absorbance of the liquid crystal composition considered to be opaque from the absorbance when opaque, indicates the increase in absorption due to the extension of the optical path length. The absorbance of the liquid crystal composition 21LC considered to be opaque may be any value that can simulate the absorbance of the liquid crystal composition 21LC when opaque. The absorbance of the liquid crystal composition 21LC considered to be opaque is, for example, the average value of the vertical absorbance and horizontal absorbance of the liquid crystal composition 21LC, which is considered to be the absorbance of the liquid crystal compound LCM when randomly aligned. Alternatively, the absorbance of the liquid crystal composition 21LC considered to be opaque may be, for example, the horizontal absorbance of the liquid crystal composition 21LC, since the liquid crystal compound LCM when opaque may have an intermediate orientation between random orientation and horizontal orientation.

The inventors of the present application, while earnestly researching the relationship between the contrast of the light control device 10 and the optical characteristics of the light control sheets, have found that the contrast is steep in the absorbance difference between the light control sheets that are superimposed on each other. I found a range to improve. If the light control device 10 satisfies the condition 2 described above, since the average absorbance difference between the light control sheets is 0.4 or more, the contrast in the light control device 10 is greatly increased. Further, if the light control device 10 satisfies the condition 8 described above, the horizontal absorbance difference in each light control sheet is 0.1 or more, so the contrast in the light control device 10 is greatly increased.

[Distribution of voids 21D]
The light control layer 21 may include a first high density portion 21H1, a second high density portion 21H2, and a low density portion 21L.

The density of the liquid crystal composition 21LC per unit thickness in the first high density portion 21H1 is higher than the density of the liquid crystal composition 21LC per unit thickness in the low density portion 21L. The number density of the voids 21D per unit thickness in the first high-density portion 21H1 is higher than the number density of the voids 21D per unit thickness in the low-density portion 21L. The first high-density portion 21H1 contacts the first alignment layer 22 .

The density of the liquid crystal composition 21LC per unit thickness in the second high density portion 21H2 is higher than the density of the liquid crystal composition 21LC per unit thickness in the low density portion 21L. The number density of voids 21D per unit thickness in the second high-density portion 21H2 is higher than the number density of voids 21D per unit thickness in the low-density portion 21L. The second high-density portion 21H2 contacts the second alignment layer 23 .

The density of the liquid crystal composition 21LC in the light modulating layer 21 is lowest in the middle of the light modulating layer 21 in the thickness direction. The middle portion of the light control layer 21 in the thickness direction is a portion closer to the center of the light control layer 21 than the pair of surfaces facing each other in the thickness direction of the light control layer 21 . The density of the liquid crystal composition 21LC per unit thickness in each portion of the light modulating layer 21 is calculated by dividing the volume of the liquid crystal composition 21LC included in each portion by the thickness of each portion. The density of the liquid crystal composition 21LC in the light modulating layer 21 may be lowest in a portion including the center in the thickness direction of the light modulating layer 21 .

The number density of the voids 21D in the transparent polymer layer 21P is lowest in the middle of the light modulating layer 21 in the thickness direction. The number density of voids 21D per unit thickness in each portion of the transparent polymer layer 21P is calculated by dividing the number of voids 21D included in each portion by the thickness of each portion. The number density of voids 21D in transparent polymer layer 21P may be lowest in a portion including the center in the thickness direction of light modulating layer 21 .

The uneven distribution of the liquid crystal compound LCM in the vicinity of the alignment layers 22 and 23 in the transparent polymer layer 21P enhances the effect of the alignment control force of the alignment layers 22 and 23 . Such uneven distribution of the liquid crystal compound LCM enhances light transmittance when the light control device 10 is transparent.

In the light control layer 21, for example, the thickness TH1 of the first high density portion 21H1, the thickness TH2 of the second high density portion 21H2, and the thickness TL of the low density portion 21L are substantially equal to each other. That is, an example of the thickness TH1 of the first high-density portion 21H1, the thickness TH2 of the second high-density portion 21H2, and the thickness TL of the low-density portion 21L is 1/3 of the thickness T21 of the light control layer 21. is. The thickness TL of the low density portion 21L may be thicker or thinner than the thicknesses TH1 and TH2 of the high density portions 21H1 and 21H2. Also, the thickness TH1 of the first high-density portion 21H1 may be equal to or different from the thickness of the second high-density portion 21H2.

In the cross section along the thickness direction of the light control layer 21, the percentage of the total area of the voids 21D included in the low density portion 21L with respect to the area of the low density portion 21L may be 10% or less. This makes it possible to reduce the ratio of the liquid crystal composition 21LC held by the gaps 21D of the low density portion 21L. It is possible to prevent the liquid crystal compound LCM contained in 21L from increasing the opacity of the light control sheet.

Furthermore, the low-density portion 21L may not have the voids 21D. In other words, the low density portion 21L may not contain the liquid crystal composition 21LC. As a result, all the liquid crystal compounds LCM contained in the light control layer 21 are easily aligned according to the alignment control force of the alignment layers 22 and 23 and the reactive mesogen compound, so that the voltage difference between the transparent electrode layers 24 and 25 is reduced. It is possible to further reduce the haze of the light control sheet in a state in which no haze has occurred.

Thus, in the low-density portion 21L, the total area SD of the voids 21D with respect to the area SL of the low-density portion 21L may be 10% or less, 5% or less, or 0%. In addition, the gap 21D is positioned within a range of 3.0 μm or less from the first alignment layer 22 and within a range of 3.0 μm or less from the second alignment layer 23 in a cross section along the thickness direction of the light control layer 21. may be located.

Each void 21D included in the first high-density portion 21H1 is preferably in contact with the first alignment layer 22 when it is required to increase the alignment regulating force acting on the liquid crystal compound LCM. Moreover, it is preferable that each void 21D included in the second high-density portion 21H2 is in contact with the second alignment layer .

In the light control sheet, the thickness T21 of the light control layer 21 may be 2 μm or more and 30 μm or less, and the diameter of the void 21D may be 0.1 μm or more and 2 μm or less. The diameter of the gap 21D is the diameter of a circle circumscribing the gap 21D in a cross section including the thickness direction of the light modulating layer 21 . When the thickness of the light control layer 21 is 2 μm or more and 30 μm or less and the diameter of the gap 21D is 0.1 μm or more and 2 μm or less, the gap 21D is formed at a position away from the alignment layers 22 and 23. is suppressed. When the size of the air gap 21D is 0.1 μm or more and 2 μm or less, the liquid crystal composition 21LC is held in the vicinity of the alignment layers 22 and 23 . Therefore, it is possible to increase the transparency of the light control sheet in a state where no voltage difference is generated between the transparent electrode layers 24 and 25 . When it is required to increase the degree of scattering by the gap 21D, the size of the gap 21D is preferably 2 μm or less. When it is required to suppress the degree of narrow-angle scattering by the air gap 21D, the size of the air gap 21D is preferably as small as 0.1 μm or more.

[Manufacturing method of light control sheet]
In manufacturing the light control sheet, first, transparent substrates 26 and 27 on which transparent electrode layers 24 and 25 are formed are prepared. Alignment layers 22 and 23 are then formed on the transparent electrode layers 24 and 25 . Next, a coating liquid is applied to the alignment layers 22 and 23 . The coating liquid contains a polymerizable composition for forming the transparent polymer layer 21P, a liquid crystal compound LCM, and a dichroic dye. A polymerizable composition is a monomer or oligomer that can be polymerized by irradiation with ultraviolet light. Next, the coating liquid is irradiated with ultraviolet rays through the transparent electrode layers 24 and 25 . As a result, a transparent polymer layer 21P having voids 21D is formed, and the liquid crystal compound LCM and the dichroic dye are retained in the voids 21D.

When the coating liquid is cured by irradiation with ultraviolet rays, the liquid crystal compound LCM and the liquid crystal composition 21LC containing the dichroic dye are distributed substantially uniformly in the polymerizable composition. Next, the polymerizable composition begins to harden in the vicinity of the alignment layers 22 and 23, and the liquid crystal composition 21LC separates from the polymer of the polymerizable composition. A part of the liquid crystal composition 21LC existing in the coating film is easily stabilized by uniting with the separated liquid crystal composition 21LC, and therefore moves toward the alignment layers 22 and 23 . Then, almost all of the polymerizable composition is cured to form a transparent polymer layer 21P having voids 21D surrounding the liquid crystal composition 21LC.

In addition, until the transparent polymer layer 21P is formed, the energy is stabilized by collecting the liquid crystal compositions 21LC separated from each other. When the curing speed of the polymerizable composition is high, or when the moving speed of the liquid crystal composition 21LC is high, the liquid crystal composition 21LC is encouraged to gather in a wide range, so the size of the gap 21D is large. Increasing the curing speed of the polymerizable composition can be achieved by increasing the temperature of the coating liquid when the coating liquid is irradiated. On the other hand, if the polymerizable composition has a wide range to be cured at the same time, the gap 21D is separated from the other gaps 21D before the liquid crystal composition 21LC is assembled. Widening the range in which the polymerizable composition is cured at the same time can be realized by increasing the illuminance of the ultraviolet rays with which the coating liquid is irradiated. Since there is a limit to the size that the voids 21D can grow, by further increasing the curing speed of the polymerizable composition, the range in which the voids 21D are formed tends to extend to the low-density portion 21L.

[Test example]
Specific test examples of the light control sheet are shown below.
Note that the light control sheets of Test Examples 1 to 10 are reverse type. The light control sheets of Test Examples 1 to 10 include alignment layers 22 and 23, transparent electrode layers 24 and 25, and transparent substrates 26 and 27. The light control sheets of Test Examples 1 to 10 contain a liquid crystal compound LCM, a dichroic dye, a reactive mesogen compound, an ultraviolet curable compound, a spacer 21S, and a polymerization initiator between the alignment layers 22 and 23. It was obtained by forming a coating film and polymerizing an ultraviolet curable compound in the coating film.

Further, the light control sheets of Test Examples 21 to 24 are normal type. Test Examples 21 to 24 include alignment layers 22 and 23 , transparent electrode layers 24 and 25 and transparent substrates 26 and 27 . The light control sheets of Test Examples 21 to 24 contain, between the alignment layers 22 and 23, a liquid crystal compound LCM, a dichroic dye, a reactive mesogen compound, an ultraviolet curable compound, a spacer 21S, and a polymerization initiator. It was obtained by forming a coating film and polymerizing an ultraviolet curable compound in the coating film. The normal-type alignment layers 22 and 23 exert an alignment regulating force on the dichroic dye and enhance light absorption due to the horizontal alignment of the dichroic dye.

Further, the light control sheets of Test Examples 25 to 37 have a configuration in which the orientation layers 22 and 23 are omitted, and include transparent electrode layers 24 and 25 and transparent substrates 26 and 27 . In the light control sheets of Test Examples 25 to 37, a liquid crystal compound LCM, a dichroic dye, a reactive mesogen compound, an ultraviolet curable compound, a spacer 21S, and a polymerization initiator are placed between the transparent electrode layers 24 and 25. obtained by forming a coating film containing and polymerizing an ultraviolet curable compound in the coating film.

Materials (a) to (h) common to the light control sheets of Test Examples 1 to 10 are shown below. Materials (c) to (h) are common to the light control sheets of Test Examples 21 to 37.
(a) Alignment layers 22, 23: vertical alignment films (b) Transparent electrode layers 24, 25: Indium tin oxide (c) Transparent substrates 26, 27: Polyethylene terephthalate film (d) Spacers 21S: Spherical particles made of silica (e) liquid crystal compound LCM: fluorine-based liquid crystal compound (f) polymerization initiator: photopolymerization initiator (Irgacure Oxe04: manufactured by BASF)
(g) Polymerizable composition: mixture of isobornyl acrylate, pentaerythritol triacrylate, and urethane acrylate (h) Dichroic dye: Azo compound mixed dye (product name: Irgaphor Black X12 DC, manufactured by BASF)
[Test Example 1]
The compounding ratios of the materials (e) to (h) with respect to the coating liquid for producing the light control sheet of Test Example 1 are shown below.
(e) liquid crystal compound LCM: 46% by mass
(f) polymerization initiator: 1% by mass
(g) polymerizable composition: 49% by mass
(h) Dichroic dye: 2% by mass
A coating film of Test Example 1 is formed by applying the coating liquid of Test Example 1 onto the first alignment layer 22 so as to arrange black spacers 21S having a particle size of 7 μm on the first alignment layer 22. bottom. Next, while the coating film of Test Example 1 was sandwiched between the first alignment layer 22 and the second alignment layer 23, the first transparent substrate 26 was irradiated with ultraviolet rays of 365 nm, and the thickness of the light control layer A light control sheet of Test Example 1 having a thickness of 7 μm was formed. At this time, the cumulative amount of UV light was set to 1380 mJ/cm ² .

[Test Example 2]
A light control sheet of Test Example 2 was obtained by the same manufacturing method as in Test Example 1.
[Test Example 3]
Dimming was performed in the same manner as in the manufacturing method of Test Example 1, except that the particle diameter of the spacer 21S was changed to 8 μm, the coating liquid of Test Example 1 was used, and the integrated amount of ultraviolet light was changed to 780 mJ/cm ² . A light control sheet of Test Example 3 having a layer thickness of 8 μm was obtained.

[Test Example 4]
A light control sheet of Test Example 4 was obtained by the same manufacturing method as in Test Example 3.
[Test Example 5]
The compounding ratios of materials (e) to (h) with respect to the coating liquid for producing the light control sheet of Test Example 5 are shown below.
(e) liquid crystal compound LCM: 50% by mass
(f) polymerization initiator: 1% by mass
(g) polymerizable composition: 45% by mass
(h) Dichroic dye: 2% by mass
A coating film of Test Example 5 is formed by applying the coating liquid of Test Example 5 onto the first alignment layer 22 so as to arrange black spacers 21S having a particle size of 8 μm on the first alignment layer 22. bottom. Next, with the coating film of Test Example 5 sandwiched between the first alignment layer 22 and the second alignment layer 23, the first transparent substrate 26 was irradiated with ultraviolet rays of 365 nm to form the light control layer. A light control sheet of Test Example 5 having a thickness of 8 μm was formed. At this time, the cumulative amount of UV light was set to 810 mJ/cm ² .

[Test Example 6]
A light control sheet of Test Example 6 was obtained by the same manufacturing method as in Test Example 5.
[Test Example 7]
Light control was performed in the same manner as in the manufacturing method of Test Example 1, except that the particle size of the spacer 21S was changed to 8 μm, the coating liquid of Test Example 1 was used, and the integrated amount of ultraviolet light was changed to 920 mJ/cm ² . A light control sheet of Test Example 7 having a layer thickness of 8 μm was obtained.

[Test Example 8]
Light control was performed in the same manner as in the manufacturing method of Test Example 1, except that the particle size of the spacer 21S was changed to 8 μm, the coating liquid of Test Example 1 was used, and the integrated amount of ultraviolet light was changed to 1380 mJ/cm ² . A light control sheet of Test Example 8 having a layer thickness of 8 μm was obtained.

[Test Example 9]
Test Example 9 in which the thickness of the light control layer is 8 μm in the same manner as in the manufacturing method of Test Example 5 except that the coating liquid of Test Example 5 is used and the integrated amount of ultraviolet light is changed to 840 mJ/cm ² . obtained.

[Test Example 10]
Test Example 10 in which the thickness of the light-modulating layer is 8 μm in the same manner as in the manufacturing method of Test Example 5, except that the coating liquid of Test Example 5 is used and the integrated amount of ultraviolet light is changed to 800 mJ/cm ² . obtained.

[Test Example 11]
The light control sheet of Test Example 2 was stacked on the light control sheet of Test Example 1 and joined together, whereby a light control device 10 of Test Example 11 was obtained. At this time, the light control sheet of Test Example 2 was attached to the light control sheet of Test Example 1 using an optically transparent adhesive.

[Test Example 12]
The light control sheet of Test Example 4 was stacked on the light control sheet of Test Example 3 and joined to obtain a light control device 10 of Test Example 12. At this time, the light control sheet of Test Example 4 was attached to the light control sheet of Test Example 3 using an optically transparent adhesive.

[Test Example 13]
The light control sheet of Test Example 6 was stacked on the light control sheet of Test Example 5 and joined to obtain a light control device 10 of Test Example 13. At this time, the light control sheet of Test Example 6 was attached to the light control sheet of Test Example 5 using an optically transparent adhesive.

[Test Example 14]
The light control sheet of Test Example 8 was stacked on the light control sheet of Test Example 7 and joined together, whereby a light control device 10 of Test Example 14 was obtained. At this time, the light control sheet of Test Example 8 was attached to the light control sheet of Test Example 7 using an optically transparent adhesive.

[Test Example 15]
The light control sheet of Test Example 10 was stacked on the light control sheet of Test Example 9 and joined to obtain a light control device 10 of Test Example 15. At this time, the light control sheet of Test Example 10 was attached to the light control sheet of Test Example 9 using an optical transparent adhesive.

[Test Example 21]
The compounding ratios of materials (e) to (h) with respect to the coating liquid for producing the light control sheet of Test Example 21 are shown below.
(e) liquid crystal compound LCM: 55% by mass
(f) polymerization initiator: 1% by mass
(g) polymerizable composition: 40% by mass
(h) Dichroic dye: 2.2% by mass
A coating film of Test Example 21 was formed by applying the coating solution of Test Example 21 on the first alignment layer 22 so as to arrange black spacers 21S having a particle size of 15 μm on the first alignment layer 22. bottom. Next, while the coating film of Test Example 21 was sandwiched between the first alignment layer 22 and the second alignment layer 23, the first transparent substrate 26 was irradiated with ultraviolet rays of 365 nm, and the thickness of the light control layer A light control sheet of Test Example 21 having a thickness of 15 μm was formed. At this time, the cumulative amount of UV light was set to 1200 mJ/cm ² .

[Test Example 22]
A light control sheet of Test Example 22 having a light control layer thickness of 15 μm was obtained in the same manner as in the manufacturing method of Test Example 21, except that the alignment layers 22 and 23 were subjected to rubbing treatment.

[Test Example 23]
A light control sheet of Test Example 23 having a light control layer with a thickness of 15 μm was obtained in the same manner as in Test Example 21.

[Test Example 24]
A light control sheet of Test Example 24 having a light control layer with a thickness of 15 μm was obtained in the same manner as in Test Example 22.

[Test Example 25]
The compounding ratios of the materials (e) to (h) with respect to the coating liquid for producing the light control sheet of Test Example 25 are shown below.
(e) liquid crystal compound LCM: 55% by mass
(f) polymerization initiator: 1% by mass
(g) polymerizable composition: 39% by mass
(h) Dichroic dye: 3.0% by mass
The coating liquid of Test Example 25 was applied on the first transparent electrode layer 24 so that black spacers 21S with a particle size of 15 μm were arranged on the first transparent electrode layer 24, and the coating film of Test Example 25 was obtained. formed. Next, while the coating film of Test Example 25 was sandwiched between the first transparent electrode layer 24 and the second transparent electrode layer 25, the first transparent substrate 26 was irradiated with ultraviolet rays of 365 nm to form a light control layer. A light control sheet of Test Example 21 having a thickness of 15 μm was formed. At this time, the cumulative amount of UV light was set to 1500 mJ/cm ² .

[Test Example 26] to [Test Example 29]
In the same manner as in Test Example 25, light control sheets of Test Examples 26 to 29 having a light control layer with a thickness of 15 μm were obtained.

[Test Example 30] to [Test Example 31]
The thickness of the light-modulating layer was 15 μm in the same manner as in the production method of Test Example 25, except that the blending ratio of the dichroic dye was changed to 4.0% by mass and the polymerizable composition was changed to 38% by mass. The light control sheets of Test Examples 30 to 31 were obtained.

[Test Example 32] to [Test Example 37]
The thickness of the light control layer was 15 μm in the same manner as in the manufacturing method of Test Example 25, except that the blending ratio of the dichroic dye was changed to 5.0% by mass and the polymerizable composition was changed to 37% by mass. The light control sheets of Test Examples 32 to 37 were obtained.

[Evaluation method]
For each of the light control sheets of Test Examples 1 to 10 and Test Examples 21 to 37, total light transmittance, diffuse transmittance, parallel line transmittance, and haze were measured by a method based on ASTM D 1003-00. , and clarity were measured. Total light transmittance, diffuse transmittance, parallel line transmittance, haze, and clarity were measured for each of the light control devices 10 of Test Examples 11 to 15 by measuring methods based on ASTM D 1003-00. An AC voltage, which is a rectangular wave of 40 V with a frequency of 50 Hz, was used as a drive signal for the light control sheet when measuring the optical characteristics. A haze meter (BYK haze-gard i indtrument: manufactured by BYK Gardner) was used as an instrument for measuring optical properties.

For each of the light control sheets of Test Examples 1 to 10 and Test Examples 21 to 37, the absorbance for visible light of 380 nm or more and 780 nm or less was measured by a measurement method based on JIS K 0115:2004. For each of the light control devices 10 of Test Examples 11 to 15, the absorbance for visible light of 380 nm or more and 780 nm or less was measured by a measurement method based on JIS K 0115:2004.

For the liquid crystal composition 21LC provided in the light control sheets of Test Examples 1 to 37, the horizontal absorbance, which is the absorbance at the time of horizontal alignment, for visible light of 380 nm or more and 780 nm or less, by a measurement method based on JIS K 0115:2004, and Average absorbance was measured. The average absorbance is the average value of the absorbance during horizontal alignment and the absorbance during vertical alignment of the liquid crystal composition 21LC. The absorbance of the liquid crystal composition 21LC was measured by placing the liquid crystal composition 21LC containing a dichroic dye in a cell for horizontal alignment with a thickness of 6 μm and a cell for vertical alignment with a thickness of 6 μm. Obtained.

For each of Test Examples 1 to 10 and Test Examples 21 to 37, the average absorbance difference was calculated by subtracting the average absorbance of the liquid crystal composition 21LC from the absorbance in the opaque state. For each of Test Examples 11 to 15, the average absorbance difference was calculated by subtracting the average absorbance of the liquid crystal composition 21LC from the absorbance of the light control device 10 when opaque.

For each of Test Examples 1 to 10 and Test Examples 21 to 37, the horizontal absorbance difference was calculated by subtracting the horizontal absorbance of the liquid crystal composition 21LC from the absorbance in the opaque state. For each of Test Examples 11 to 15, the horizontal absorbance difference was calculated by subtracting the horizontal absorbance of the liquid crystal composition 21LC from the absorbance of the light control device 10 in the opaque state.

For each of Test Examples 1 to 37, the ratio of the total light transmittance in the bright state to the total light transmittance in the dark state in the light control device 10 was calculated as the contrast. For each of Test Examples 11 to 15, the ratio of the contrast of the light control device 10 to the total contrast of the two light control sheets constituting the light control device 10 was calculated as an increase rate.

[Evaluation results]
The evaluation results of Test Examples 1 to 37 are shown in FIGS. 3 and 4 together with the configuration of each Test Example.
FIG. 5 is a graph showing the relationship between haze and contrast and the relationship between clarity and contrast for Test Examples 1 to 15. In FIG. FIG. 6 is a graph showing the relationship between haze and contrast for Test Examples 1 to 37. In FIG. 7 is a graph showing the relationship between horizontal absorbance difference and contrast and the relationship between average absorbance difference and contrast for Test Examples 1 to 15. FIG.

8 is a graph showing the relationship between the average absorbance difference and the contrast for Test Examples 1 to 15 and Test Examples 21 to 37. FIG. FIG. 9 is a graph showing the relationship between parallel line transmittance and contrast and the relationship between diffuse transmittance and contrast for Test Examples 1 to 15. In FIG.

As shown in FIGS. 3 and 5, in the evaluation results of Test Examples 1 to 10, when the haze of one light control sheet is 56% or more and 87% or less, the contrast of the light control sheet is 2.3. It was found to stop below. Further, in the evaluation results of Test Example 11, when the haze of one light control sheet is 50% or more and less than 79%, the contrast is 2.3 or less even in the light control device 10 in which two light control sheets are superimposed. was allowed to stop.

On the other hand, in the evaluation results of Test Examples 12 to 15, when the haze of one light control sheet is 79% or more, the contrast is steep in the light control device 10 in which the two light control sheets are superimposed. recognized to rise. In addition, in the evaluation results of Test Examples 11 to 15, when the haze of the two light control sheets is both 79% or more, the contrast increase rate in the light control device 10 in which the two light control sheets are overlapped is It was also found to be greater than or equal to 1.

In the evaluation results of Test Examples 1 to 10, when the clarity of one light control sheet was in the range of 86% to 99%, the contrast of the light control sheet remained at 2.3 or less. Further, in the evaluation results of Test Examples 11 to 15, the contrast of the light control device 10 in which two light control sheets are superimposed differs greatly among the clarity of one light control sheet of 95%±3%. was accepted. That is, no relation between the clarity of one light control sheet and the light control device 10 having high contrast was observed.

As shown in FIGS. 3, 4 and 6, in the evaluation results of Test Examples 21 to 37, when the haze of the light control sheet is less than 79%, the contrast is reduced as in the case of one reverse type light control sheet. It was found to be of the order of 3. On the other hand, in the evaluation results of Test Examples 21 to 37, when the haze of the light control sheet is 79% or more, the contrast sharply increases, and the contrast increases to 4 as if two reverse type light control sheets are superimposed. It was confirmed that a high contrast above a certain level can be obtained.

As shown in FIGS. 3 and 7, in the evaluation results of Test Examples 1 to 10, when the average absorbance difference of one light control sheet is 0.28 or more and 0.54 or less, the contrast of the light control sheet was found to remain below 2.3. In the evaluation results of Test Examples 1 to 10, when the horizontal absorbance difference of one light control sheet is 0.04 or more and 0.25 or less, the contrast of the light control sheet is found to be 2.3 or less. rice field.

Further, in the evaluation results of Test Example 11, when the average absorbance difference of one light control sheet is less than 0.4, the contrast is 2.3 or less even in the light control device 10 in which two light control sheets are superimposed. was allowed to stop. Further, in the evaluation results of Test Example 11, when the average absorbance difference of one light control sheet is less than 0.1, the contrast is 2.3 or less even in the light control device 10 in which the two light control sheets are superimposed. was allowed to stop.

On the other hand, in the evaluation results of Test Examples 12 to 15, when the average absorbance difference of one light control sheet is 0.4 or more, in the light control device 10 in which the two light control sheets are superimposed, the contrast was found to increase sharply. In the evaluation results of Test Examples 12 to 15, when the horizontal absorbance difference of one light control sheet is 0.1 or more, the contrast sharply increases in the light control device 10 in which the two light control sheets are superimposed. was recognized.

In addition, in the evaluation results of Test Examples 11 to 15, when the average absorbance of the two light control sheets is both 0.4 or more, the contrast is increased in the light control device 10 in which the two light control sheets are superimposed. A ratio of 1 or greater was also observed. Further, in the evaluation results of Test Examples 11 to 15, when the horizontal absorbances of the two light control sheets are both 0.1 or more, the contrast is increased in the light control device 10 in which the two light control sheets are superimposed. A ratio of 1 or greater was also observed.

Further, as shown in FIGS. 3, 4 and 8, in the evaluation results of Test Examples 1 to 37, when the average absorbance difference in the light control device 10 is less than 0.8, the contrast remains at about 3. was recognized. On the other hand, when the average absorbance difference in the light control device 10 was 0.8 or more, it was also recognized that the contrast increased more steeply.

As shown in FIGS. 3, 4 and 9, in the evaluation results of Test Examples 1 to 15, the dependence of contrast on diffuse transmittance was found to be sufficiently greater than the dependence of contrast on parallel line transmittance. was taken. That is, it was recognized that promoting the scattering of straight transmitted light in the light control sheet enhances the absorption of light by the dichroic dye and accelerates the improvement of the contrast.

As shown in FIG. 3, when the haze of one light control sheet is 79% or more and the total light transmittance is 25% or less, in the light control device 10 in which the two light control sheets are superimposed, the contrast can be increased to 4 or more. When the average absorbance difference of one light control sheet is 0.4 or more and the total light transmittance is 25% or less, the contrast is increased to 4 or more in the light control device 10 in which the two light control sheets are superimposed. was also recognized.

Further, when the haze of one light control sheet is 79% or more and the diffuse transmittance is 16% or less, the contrast is increased to 4 or more in the light control device 10 in which the two light control sheets are superimposed. It was also found that the accuracy was improved. When the average absorbance difference of one light control sheet is 0.4 or more and the diffuse transmittance is 16% or less, the contrast is increased to 4 or more in the light control device 10 in which the two light control sheets are superimposed. It was also found that the accuracy of

Further, when the haze of one light control sheet is 79% or more and the parallel line transmittance is 5% or less, the contrast is increased to 4 or more in the light control device 10 in which the two light control sheets are superimposed. It was also found that the accuracy of When the average absorbance difference of one light control sheet is 0.4 or more and the parallel line transmittance is 5% or less, the contrast is increased to 4 or more in the light control device 10 in which the two light control sheets are superimposed. It was also found that the accuracy of

Further, when the haze of one light control sheet is 79% or more and the clarity is 95% or less, the contrast is increased to 4 or more in the light control device 10 in which two light control sheets are superimposed. It was also found to be enhanced. When the average absorbance difference of one light control sheet is 0.4 or more and the clarity is 95% or less, the probability that the contrast is increased to 4 or more in the light control device 10 in which the two light control sheets are superimposed was also found to be enhanced.

As described above, according to the above embodiment, the following effects can be obtained.
(1) Since the opaque haze of each light control sheet constituting the light control device 10 is 79% or more, the contrast in the light control device 10 can be greatly increased.

(2) Since the average absorbance difference in each light control sheet constituting the light control device 10 is 0.4 or more, the contrast in the light control device 10 can be greatly increased.
(3) If the configuration satisfies condition 1 or at least one of condition 2 to condition 6 in addition to satisfying condition 2, it is possible to obtain the effects according to the above (1) and (2). Increased feasibility.

(4) In the case of the light control device 10 in which the reverse type light control sheets satisfying Condition 1 or Condition 2 are superimposed, the dark state is formed only by the alignment control force of the alignment layers 22 and 23 and the reactive mesogen compound. Even with the optical device 10, it becomes possible to obtain a high contrast.

In addition, the embodiment described above can be implemented with the following changes.
・In the light control layer 21, the voids 21D of the transparent polymer layer 21P may be dispersed throughout the thickness direction of the transparent polymer layer 21P, or may be uniformly distributed throughout the thickness direction of the transparent polymer layer 21P. may be dispersed.

LCM... liquid crystal compound 10... light control device 11... light control sheet 11UN1... first light control unit 11UN2... second light control unit 21... light control layer 21D... gap 21L... transparent polymer layer 21LC... liquid crystal composition 22... second 1 Orientation Layer 23 Second Orientation Layer 24 First Transparent Electrode Layer 25 Second Transparent Electrode Layer 26 First Transparent Substrate 27 Second Transparent Substrate

Claims (8)

Equipped with two light control sheets that reversibly change between a transparent state and an opaque state,
A light control device having a state in which one light control sheet is superimposed on another light control sheet and each light control sheet is simultaneously opaque,
The light control sheet is
a transparent polymer layer having voids;
A liquid crystal composition containing a liquid crystal compound and a dichroic dye and filling the voids,
The absorbance difference, which is the value obtained by subtracting the average absorbance of the liquid crystal composition from the absorbance in the opaque state of the light control sheet , is 0.4 or more,
The average absorbance is the average value of the absorbance during horizontal alignment of the liquid crystal composition and the absorbance during vertical alignment of the liquid crystal composition,
The absorbance at the time of horizontal alignment is the absorbance obtained by placing the liquid crystal composition containing the liquid crystal compound and the dichroic dye in a cell for horizontal alignment having a thickness of 6 μm,
The absorbance during vertical alignment is the absorbance obtained by placing the liquid crystal composition containing the liquid crystal compound and the dichroic dye in a vertical alignment cell having a thickness of 6 μm.
A light control device characterized by: Equipped with two light control sheets that reversibly change between a transparent state and an opaque state,
A light control device having a state in which one light control sheet is superimposed on another light control sheet and each light control sheet is simultaneously opaque,
The light control sheet is
a transparent polymer layer having voids;
A liquid crystal composition containing a liquid crystal compound and a dichroic dye and filling the voids,
The absorbance difference, which is the value obtained by subtracting the horizontal absorbance of the liquid crystal composition from the absorbance in the opaque state of the light control sheet , is 0.1 or more,
The horizontal absorbance is the absorbance at the time of horizontal alignment of the liquid crystal composition,
The absorbance during horizontal alignment is the absorbance obtained by placing the liquid crystal composition containing the liquid crystal compound and the dichroic dye in a cell for horizontal alignment having a thickness of 6 μm.
A light control device characterized by: The light control sheet has a haze of 79% or more when opaque.
The light control device according to claim 1 or 2. The light control device according to any one of claims 1 to 3, wherein the light control sheet has a total light transmittance of 25% or less when the light control sheet is opaque. The light control device according to any one of claims 1 to 3, wherein the light control sheet has a diffuse transmittance of 16% or less when the light control sheet is opaque. The light control device according to any one of claims 1 to 3, wherein the light control sheet has a parallel line transmittance of 5% or less when the light control sheet is opaque. The light control device according to any one of claims 1 to 3, wherein the light control sheet has a clarity of 95% or less when the light control sheet is opaque. The light control sheet is
a first transparent electrode layer;
a second transparent electrode layer;
a first alignment layer located between the first transparent electrode layer and the transparent polymer layer;
a second alignment layer positioned between the second transparent electrode layer and the transparent polymer layer;
The light control layer comprising the transparent polymer layer and the liquid crystal composition has a thickness of 10 μm or less,
The light control device according to claim 1 or 2.

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