Polymer-dispersed liquid crystal film

Abstract

A polymer-dispersed liquid crystal film according to an embodiment of the present invention comprises, in the stated order: a first transparent conductive film; a polymer-dispersed liquid crystal layer including a polymer matrix, and liquid crystal droplets dispersed in the polymer matrix; and a second transparent conductive film. The polymer-dispersed liquid crystal layer has a first region in which the liquid crystal droplets include a non-polymerizable liquid crystal component, a liquid crystal polymer, and a dichroic dye, and a second region in which the liquid crystal droplets include a non-polymerizable liquid crystal component, a polymerizable liquid crystal component, and a dichroic dye.

Description

Polymer dispersed liquid crystal film

[0001] The present invention relates to a polymer dispersed liquid crystal film.

[0002] BACKGROUND ART In recent years, light-control films that exhibit different appearances depending on the state of applied voltage have been applied to a variety of applications, such as displays such as advertisements and guide boards, and smart windows.

[0003] A PDLC film having a polymer dispersed liquid crystal (hereinafter, sometimes referred to as "PDLC") layer between a pair of transparent electrode layers is a type of light control film that can switch between a light scattering state (scattering state) and a light transmitting state (non-scattering state or transparent state) by switching between a voltage application state and a voltage non-application state. Specifically, the PDLC layer includes a polymer matrix and droplets of a liquid crystal component (liquid crystal droplets) dispersed in the polymer matrix. The liquid crystal droplets act as scattering particles, causing light scattering due to the difference in refractive index between the liquid crystal component in the liquid crystal droplets and the polymer matrix (see, for example, Patent Document 1).

[0004] The above-mentioned PDLC film generally has a cloudy appearance in the scattering state, and can therefore have two appearances: cloudy (scattering state) and transparent (non-scattering state). However, in consideration of design, there is a demand for a light-control film that can have other appearances.

[0005] Japanese Patent Application Laid-Open No. 2021-60521

[0006] The present invention has been made to solve the above-mentioned conventional problems, and its main object is to provide a polymer dispersed liquid crystal film that can have high designability, specifically, a polymer dispersed liquid crystal film that can be switched between a transparent state and a colored state in a desired pattern.

[0007] [1] According to one aspect of the present invention, there is provided a polymer-dispersed liquid crystal film comprising, in this order: a first transparent conductive film; a polymer-dispersed liquid crystal layer including a polymer matrix and liquid crystal droplets dispersed in the polymer matrix; and a second transparent conductive film, wherein the polymer-dispersed liquid crystal layer has a first region in which the liquid crystal droplets include a non-polymerizable liquid crystal component, a liquid crystal polymer, and a dichroic dye; and a second region in which the liquid crystal droplets include a non-polymerizable liquid crystal component, a polymerizable liquid crystal component, and a dichroic dye. [2] In the polymer-dispersed liquid crystal film described in [1] above, a change in transmittance at the absorption peak wavelength of the dichroic dye in the first region due to application of a voltage may be smaller than a change in transmittance in the second region. [3] In the polymer-dispersed liquid crystal film described in [1] or [2] above, the liquid crystal droplets may have an average particle size of 1 μm or less. [4] In the polymer dispersed liquid crystal film according to any one of [1] to [3] above, the content of the liquid crystal polymer in the first region may be 1 to 30 parts by weight relative to 100 parts by weight of the non-polymerizable liquid crystal component. [5] In the polymer dispersed liquid crystal film according to any one of [1] to [4] above, the content of the dichroic dye in the first region may be 0.1 to 10 parts by weight relative to 100 parts by weight of the non-polymerizable liquid crystal component. [6] In the polymer dispersed liquid crystal film according to any one of [1] to [5] above, the difference in haze between the first region and the second region may increase by application of a voltage. [7] In the polymer dispersed liquid crystal film according to any one of [1] to [5] above, the difference in haze between the first region and the second region may decrease by application of a voltage. [8] The polymer dispersed liquid crystal film according to any one of [1] to [7] above may further include a reflective layer on the side of the first transparent conductive film or the second transparent conductive film opposite to the side on which the polymer dispersed liquid crystal layer is disposed.

[0008] According to an embodiment of the present invention, the orientation of the liquid crystal component is regulated in the liquid crystal droplets containing the liquid crystal polymer, and the liquid crystal droplets contain a dichroic dye, so that changes in haze and color state due to changes in the applied voltage are suppressed. Therefore, by changing the applied voltage while the liquid crystal polymer is present in the liquid crystal droplets in a desired region, it is possible to change the haze and color state in the other regions while suppressing changes in the haze and color state in that region.

[0009] 1A is a schematic plan view of an example of a PDLC film according to an embodiment of the present invention, (b) is a schematic cross-sectional view illustrating the state of the PDLC film shown in (a) when no voltage is applied, and (c) is a schematic cross-sectional view illustrating the state of the PDLC film shown in (a) when a voltage is applied. 1A is a schematic plan view of another example of a PDLC film according to an embodiment of the present invention, (b) is a schematic cross-sectional view illustrating the state of the PDLC film shown in (a) when no voltage is applied, and (c) is a schematic cross-sectional view illustrating the state of the PDLC film shown in (a) when a voltage is applied. 1A and (b) are schematic cross-sectional views illustrating the states of another example of a PDLC film according to an embodiment of the present invention when no voltage is applied and when a voltage is applied, respectively. 1B are schematic diagrams illustrating an example of a method for manufacturing a PDLC film according to the present invention. 1C are schematic diagrams illustrating an example of a method for manufacturing a PDLC film according to the present invention.

[0010] Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. Furthermore, each embodiment can be combined as appropriate. In this specification, the term "to" indicating a numerical range includes the upper and lower limits. For clarity of explanation, the drawings may show the width, thickness, shape, etc. of each part more schematically than in the embodiments. However, these are merely examples and do not limit the interpretation of the present invention.

[0011] A. Polymer-Dispersed Liquid Crystal Film FIG. 1( a ) is a schematic plan view of an example of a polymer-dispersed liquid crystal (PDLC) film according to one embodiment (first embodiment) of the present invention; FIG. 1( b ) is a schematic cross-sectional view illustrating the state of the PDLC film shown in FIG. 1( a ) when no voltage is applied; and FIG. 1( c ) is a schematic cross-sectional view illustrating the state of the PDLC film shown in FIG. 1( a ) when a voltage is applied. The PDLC film 100 a includes, in this order, a first transparent conductive film 10, a PDLC layer 20 including a polymer matrix 22 and liquid crystal droplets 24 dispersed in the polymer matrix 22, and a second transparent conductive film 30. The PDLC layer 20 includes a first region A in which the liquid crystal droplets 24 include a non-polymerizable liquid crystal component 24 a, a liquid crystal polymer 24 c, and a dichroic dye 24 d, and a second region B in which the liquid crystal droplets 24 include the non-polymerizable liquid crystal component 24 a, a polymerizable liquid crystal component 24 b, and a dichroic dye 24 d.

[0012] As shown in FIG. 1B , in the PDLC film 100a, when no voltage is applied, the non-polymerizable liquid crystal component 24a, the liquid crystal polymer 24c, and the dichroic dye 24d in the liquid crystal droplets 24 in the first region A are all non-oriented. Furthermore, the non-polymerizable liquid crystal component 24a, the polymerizable liquid crystal component 24b, and the dichroic dye 24d in the liquid crystal droplets 24 in the second region B are all non-oriented. Therefore, in both the first region A and the second region B, scattering of transmitted light occurs due to the difference in refractive index between the polymer matrix and the liquid crystal component and / or the liquid crystal polymer, and absorption by the dichroic dye occurs. Therefore, both the first region A and the second region B may be in a colored / scattered state. As a result, the entire main surface of the PDLC film 100a may be in a colored / scattered state when no voltage is applied. In this specification, a compound being "non-oriented" means that the compound is not aligned with any regularity.

[0013] On the other hand, as shown in FIG. 1( c), in the PDLC film 100a, the non-polymerizable liquid crystal component 24a, the polymerizable liquid crystal component 24b, and the dichroic dye 24d in the liquid crystal droplets 24 in the second region B are all oriented in a predetermined direction (thickness direction in the illustrated example) when a voltage is applied. Therefore, scattering and absorption of transmitted light are suppressed in the second region B, resulting in low haze (transparent) and light coloration (colorless). Meanwhile, in the first region A, the presence of the non-oriented liquid crystal polymer 24c restricts the orientation of the non-polymerizable liquid crystal component 24a and the dichroic dye 24d, maintaining the non-oriented state. Therefore, scattering and absorption of transmitted light occur in the first region A, similar to when no voltage is applied. As a result, in the PDLC film 100a when a voltage is applied, the first region A may be in a colored / scattering state, and the second region B may be in a colorless / transparent state. However, the colorless / transparent state means lower haze and lighter color than the colored / scattering state, and does not necessarily mean completely colorless / transparent.

[0014] In the PDLC film 100a, the change in haze in the first region A due to the application of a voltage is smaller than the change in the second region B, and the difference between the haze in the first region A and the haze in the second region B increases due to the application of a voltage. Ａ The change in the transmittance T Ａ and the change in transmittance T Ａ and the transmittance T of the second region B Ａ The difference between these two increases with the application of voltage.

[0015] The haze of the region of the PDLC film corresponding to the first region when no voltage is applied (hereinafter, sometimes simply referred to as "the haze of the first region") is, for example, 50% to 100%, preferably 70% to 100%. The haze of the first region when a voltage is applied is, for example, 40% to 100%, preferably 60% to 100%. The change in haze of the first region due to the application of a voltage (|haze when no voltage is applied - haze when voltage is applied|) is, for example, 0% to 40%, preferably 0% to 30%.

[0016] The haze of the region of the PDLC film corresponding to the second region when no voltage is applied (hereinafter, sometimes simply referred to as "the haze of the second region") is, for example, 50% to 100%, preferably 70% to 100%. The haze of the second region when a voltage is applied is, for example, 1% to 20%, preferably 1% to 10%. The change in haze of the second region due to the application of a voltage (|haze when no voltage is applied - haze when voltage is applied|) is, for example, 30% to 99%, preferably 60% to 99%.

[0017] The difference between the amount of change in haze in the first region due to application of a voltage and the amount of change in haze in the second region due to application of a voltage is, for example, 10% to 99%, and preferably 30% to 99%.

[0018] The transmittance T in the region corresponding to the first region and the region corresponding to the second region of the PDLC film when no voltage is applied. Ａ can vary depending on the type and blending ratio of the dichroic dye, and can be appropriately set depending on the purpose.

[0019] The transmittance T of the region of the PDLC film corresponding to the first region when no voltage is applied Ａ (Hereinafter, simply “transmittance T of the first region Ａ The transmittance T of the first region when a voltage is applied is, for example, 40% to 90%, and preferably 40% to 70%. Ａ is, for example, 40% to 95%, preferably 40% to 70%. Ａ The change in transmittance when no voltage is applied (| Ａ -Transmittance T when voltage is applied Ａ |) is, for example, 0% to 10%, and also, for example, 0% to 5%.

[0020] The transmittance T of the region of the PDLC film corresponding to the second region when no voltage is applied Ａ (Hereinafter, simply “transmittance T of the second region Ａ The transmittance T of the second region when a voltage is applied is, for example, 40% to 90%, and preferably 40% to 70%. Ａ The transmittance T of the second region due to the application of a voltage is, for example, 45% to 95%, and preferably 60% to 95%.Ａ The change in transmittance when no voltage is applied (| Ａ -Transmittance T when voltage is applied Ａ |) is, for example, 5% to 30%, and also, for example, 5% to 20%.

[0021] Transmittance T of the first region by applying a voltage Ａ and the transmittance T of the second region due to the application of voltage Ａ The difference from the change amount is, for example, 5% to 25%, or, for example, 5% to 20%.

[0022] The voltage applied to the PDLC film during voltage application is a voltage capable of operating the PDLC film (operating voltage), and may be, for example, 5 V to 200 V, and preferably 10 V to 100 V. In this specification, "when a voltage is applied" refers to a state in which an operating voltage is applied to the PDLC film, and may be, for example, a state in which a voltage of 30 V is applied.

[0023] The thickness of the PDLC film is, for example, 30 μm to 250 μm, preferably 50 μm to 150 μm.

[0024] A-1. First Transparent Conductive Film The first transparent conductive film 10 typically includes a first transparent substrate 12 and a first transparent electrode layer 14 provided on one side thereof. The first transparent conductive film 10 may optionally include a hard coat layer on one or both sides of the first transparent substrate 12, and may also include a refractive index adjusting layer between the first transparent substrate 12 and the first transparent electrode layer 14.

[0025] The surface resistance value of the first transparent conductive film is preferably 1 Ω / □ to 1000 Ω / □, more preferably 5 Ω / □ to 300 Ω / □, and even more preferably 10 Ω / □ to 200 Ω / □.

[0026] The haze of the first transparent conductive film is preferably 20% or less, more preferably 10% or less, and even more preferably 0.1% to 10%.

[0027] The total light transmittance of the first transparent conductive film is preferably 30% or more, more preferably 60% or more, and even more preferably 80% or more.

[0028] The first transparent substrate can be formed using any appropriate material. Specifically, for example, a polymer substrate such as a film or a plastic substrate is preferably used. This is because it has excellent smoothness and wettability with respect to the transparent electrode layer-forming composition, and can significantly improve productivity by continuous production using a roll.

[0029] Typically, the first transparent substrate is a polymer film mainly composed of a thermoplastic resin. Examples of thermoplastic resins include polyester resins; cycloolefin resins such as polynorbornene; acrylic resins; polycarbonate resins; and cellulose resins. Of these, polyester resins, cycloolefin resins, and acrylic resins are preferred. These resins are excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, and the like. The above thermoplastic resins may be used alone or in combination of two or more.

[0030] The thickness of the first transparent substrate is preferably 200 μm or less, more preferably 3 μm to 100 μm, and even more preferably 5 μm to 70 μm. By setting the thickness of the first transparent substrate to 200 μm or less, the function of the PDLC layer can be fully exhibited.

[0031] The total light transmittance of the first transparent substrate is preferably 30% or more, more preferably 60% or more, and even more preferably 80% or more.

[0032] The first transparent electrode layer may be made of, for example, indium tin oxide (ITO), zinc oxide (ZnO), or tin oxide (SnO ２ The first transparent electrode layer may be formed using a metal oxide such as ZnO. In this case, the metal oxide may be an amorphous metal oxide or a crystallized metal oxide. The first transparent electrode layer may also be formed using metal nanowires such as silver nanowires (AgNW), carbon nanotubes (CNT), an organic conductive film, a metal layer, or a laminate thereof. Preferably, a transparent electrode layer containing ITO is formed. A transparent electrode layer containing ITO has excellent transparency. The first transparent electrode layer may be patterned into a desired shape depending on the purpose.

[0033] The total light transmittance of the first transparent electrode layer is preferably 85% or more, more preferably 87% or more, and even more preferably 90% or more. By using a transparent electrode layer having a total light transmittance in this range, a PDLC film having a high total light transmittance in the transparent state can be obtained. The higher the total light transmittance, the more preferable it is, and the upper limit is, for example, 99%.

[0034] The thickness of the first transparent electrode layer is, for example, 10 nm or more, preferably 15 nm or more, and for example, 50 nm or less, preferably 35 nm or less, more preferably 30 nm or less.

[0035] The first transparent electrode layer is formed on one surface of the first transparent substrate by, for example, sputtering. After forming the metal oxide layer by sputtering, it can be crystallized by annealing. Annealing is performed by, for example, heat treatment at 120°C to 300°C for 10 to 120 minutes.

[0036] The refractive index adjusting layer and the hard coat layer may have a structure well known in the art, and therefore detailed description of their structures will be omitted.

[0037] A-2. PDLC Layer The PDLC layer 20 includes a polymer matrix 22 and droplets of a liquid crystal component (liquid crystal droplets) 24 dispersed in the polymer matrix 22. As shown in Fig. 1, the PDLC layer 20 has a first region A and a second region B. The liquid crystal droplets 24 in the first region A include a non-polymerizable liquid crystal component 24a, a liquid crystal polymer 24c, and a dichroic dye 24d, while the liquid crystal droplets 24 in the second region B include a non-polymerizable liquid crystal component 24a, a polymerizable liquid crystal component 24b, and a dichroic dye 24d. The first region A and the second region B can be formed in any suitable pattern depending on the design desired for the PDLC film.

[0038] The polymer matrix may be composed of any appropriate resin. The resin for forming the polymer matrix may be appropriately selected depending on the light transmittance, the refractive index of the liquid crystal component, the adhesion to the transparent conductive film, etc. For example, water-soluble or water-dispersible resins such as urethane-based resins, polyvinyl alcohol-based resins, polyethylene-based resins, polypropylene-based resins, and acrylic-based resins may be preferably used. The polymer matrix-forming resins may be used alone or in combination.

[0039] As the non-polymerizable liquid crystal component, any non-polymerizable liquid crystal compound can be used alone or in combination of two or more depending on the birefringence, compatibility with the polymerizable liquid crystal component, etc. In the following description, the properties of the liquid crystal component (birefringence, dielectric constant, etc.) mean the properties of the liquid crystal component as a whole, which may contain multiple liquid crystal compounds.

[0040] The birefringence (Δn=refractive index of the liquid crystal component in the major axis direction, no=refractive index of the liquid crystal component in the minor axis direction) of the non-polymerizable liquid crystal component at a wavelength of 589 nm is preferably 0.05 to 0.50, more preferably 0.10 to 0.45.

[0041] In the illustrated example, a non-polymerizable liquid crystal component having positive dielectric anisotropy is used, but the dielectric anisotropy of the non-polymerizable liquid crystal component may be either positive or negative.

[0042] The non-polymerizable liquid crystal component may be, for example, a nematic, smectic, or cholesteric liquid crystal component. It is preferable to use a nematic liquid crystal component because it can achieve excellent transparency in the transparent state.

[0043] Examples of nematic liquid crystal compounds include biphenyl-based compounds, phenylbenzoate-based compounds, cyclohexylbenzene-based compounds, azoxybenzene-based compounds, azobenzene-based compounds, azomethine-based compounds, terphenyl-based compounds, biphenylbenzoate-based compounds, cyclohexylbiphenyl-based compounds, phenylpyridine-based compounds, cyclohexylpyrimidine-based compounds, cholesterol-based compounds, fluorine-based compounds, etc. These low-molecular-weight liquid crystal compounds may be used alone or in combination.

[0044] As the polymerizable liquid crystal component, any polymerizable liquid crystal compound can be used alone or in combination of two or more depending on the birefringence, compatibility with the non-polymerizable liquid crystal component, etc. The polymerizable liquid crystal compound may be a bifunctional or higher crosslinked type. Examples of the polymerizable liquid crystal compound include polymerizable mesogenic compounds described in, for example, JP-A-2002-533742 (WO 00 / 37585), EP 358208 (US 5,211,877), EP 66137 (US 4,388,453), WO 93 / 22397, EP 0,261,712, DE 19504224, DE 4408171, and GB 2,280,445. Specific examples of such polymerizable mesogenic compounds include LC242, a product name of BASF. Nematic liquid crystal monomers are preferred as the polymerizable liquid crystal compound.

[0045] The birefringence (Δn=refractive index in the long axis direction of the liquid crystal component, no=refractive index in the short axis direction of the liquid crystal component) of the polymerizable liquid crystal component at a wavelength of 589 nm is preferably 0.05 to 0.50, more preferably 0.10 to 0.45.

[0046] Liquid crystal polymers are typically polymerization products of the polymerizable liquid crystal components. Polymerization of the polymerizable liquid crystal components forms a polymer, and crosslinking can form a network structure, but these are non-liquid crystals. Therefore, in liquid crystal polymers, for example, the transition to a liquid crystal phase, glass phase, or crystalline phase due to temperature changes that is specific to liquid crystal compounds does not occur.

[0047] The liquid crystal polymer is typically present in a non-oriented state in the liquid crystal droplets. Because the liquid crystal polymer in the liquid crystal droplets is in a non-oriented state, the first region can maintain a high haze (for example, 40% to 100%, preferably 60% to 100%) even when a voltage is applied.

[0048] As the dichroic dye, any appropriate dichroic dye that is compatible with a non-polymerizable liquid crystal component and a polymerizable liquid crystal component (these may be collectively referred to as "liquid crystal components") can be used. The dichroic dye may have a positive or negative Δε. The dichroic dye itself may exhibit liquid crystallinity. Only one dichroic dye may be used, or two or more dichroic dyes may be used in combination.

[0049] Specific examples of dichroic dyes include azo dyes, anthraquinone dyes, naphthoquinone dyes, perylene dyes, quinophthalone dyes, tetrazine dyes, and benzothiadiazole dyes. Among these, from the viewpoints of absorption coefficient, solubility in liquid crystal components, light resistance, and the like, it is preferable that the dichroic dye contains an anthraquinone dye or an azo dye. For example, the azo dyes, anthraquinone dyes, or mixtures thereof described in "Liquid Crystal Device Handbook," edited by Committee 142 of the Japan Society for the Promotion of Science, published by the Japan Industrial Newspaper Co., Ltd. (1989), pages 192 to 196 and 724 to 730, can be used. Various dichroic dyes are commercially available, and these can be used as appropriate.

[0050] The content of the polymer matrix in the PDLC layer in both the first and second regions is, for example, 30 to 70% by weight, preferably 35 to 65% by weight, and more preferably 40 to 60% by weight. When the content of the polymer matrix is ​​within the above range, effects such as a good light control function at a moderate operating voltage, good mechanical strength, and prevention of liquid crystal leakage from the edges can be obtained.

[0051] The ratio of the content of the polymer matrix to the total content of the non-polymerizable liquid crystal component, the liquid crystal polymer, and the dichroic dye in the first region (former:latter (by weight)) is 30:70 to 70:30, preferably 35:65 to 65:35, and more preferably 40:60 to 60:40. The content of the liquid crystal polymer in the first region may be, for example, 1 to 30 parts by weight, preferably 5 to 20 parts by weight, relative to 100 parts by weight of the non-polymerizable liquid crystal component. The content of the dichroic dye in the first region may be, for example, 0.1 to 10 parts by weight, preferably 0.5 to 7 parts by weight, relative to 100 parts by weight of the non-polymerizable liquid crystal component. The total content of the polymer matrix, the non-polymerizable liquid crystal component, the liquid crystal polymer, and the dichroic dye in the first region may typically be 80 to 100% by weight, for example, 90 to 99.9% by weight, and preferably 95 to 99.9% by weight.

[0052] The ratio of the content of the polymer matrix to the total content of the non-polymerizable liquid crystal component, the polymerizable liquid crystal component, and the dichroic dye in the second region (former:latter (by weight)) is 30:70 to 70:30, preferably 35:65 to 65:35, and more preferably 40:60 to 60:40. The content of the polymerizable liquid crystal component in the second region may be, for example, 1 to 30 parts by weight, preferably 5 to 20 parts by weight, relative to 100 parts by weight of the non-polymerizable liquid crystal component. The content of the dichroic dye in the second region may be, for example, 0.1 to 10 parts by weight, preferably 0.5 to 7 parts by weight, relative to 100 parts by weight of the non-polymerizable liquid crystal component. The total content of the polymer matrix, the non-polymerizable liquid crystal component, the polymerizable liquid crystal component, and the dichroic dye in the second region may typically be 80 to 100% by weight, for example, 90 to 99.9% by weight, and preferably 95 to 99.9% by weight.

[0053] Unreacted polymerizable liquid crystal components may remain in the liquid crystal droplets in the first region. The content of unreacted polymerizable liquid crystal components in the first region is, for example, 3 wt % or less, preferably 1 wt % or less. Furthermore, it is preferable that the liquid crystal droplets in the second region are substantially free of liquid crystal polymer. The content of liquid crystal polymer in the second region is, for example, 3 wt % or less, preferably 1 wt % or less.

[0054] The PDLC layer may further contain any appropriate additives as needed. As described in detail in Section B, a PDLC layer having first and second regions can be formed by polymerizing a polymerizable liquid crystal component in a predetermined region of a PDLC layer containing liquid crystal droplets containing a non-polymerizable liquid crystal component, a polymerizable liquid crystal component, and a dichroic dye to form a liquid crystal polymer. In this case, the predetermined region becomes the first region, and the other regions become the second region. Therefore, the PDLC layer (more specifically, the liquid crystal droplets) may further contain a polymerization initiator. Other additives include a dispersant, a leveling agent, a crosslinking agent, a dispersion stabilizer, etc.

[0055] As the polymerization initiator, any appropriate photopolymerization initiator can be used depending on the purpose, desired properties, and the like. Specific examples of the photopolymerization initiator include 2,2-dimethoxy-2-phenylacetophenone, acetophenone, benzophenone, xanthone, 3-methylacetophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, benzoin propyl ether, benzil dimethyl ketal, N,N,N',N'-tetramethyl-4,4'-diaminobenzophenone, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-dipentoxyphenylphosphine oxide, bis(2,6-dimethoxy-benzoyl)-(2,4,4-trimethyl-pentyl)-phosphine oxide, and thioxanthone compounds. The photopolymerization initiators may be used alone or in combination of two or more. The content of the photopolymerization initiator is, for example, 0.1 to 10 parts by weight, and preferably 0.5 to 5 parts by weight, relative to 100 parts by weight of the polymerizable liquid crystal component.

[0056] Examples of the dispersant include anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc. The content of the dispersant in the PDLC layer is, for example, 1 to 15% by weight, and preferably 2 to 10% by weight.

[0057] Examples of the leveling agent include an acrylic leveling agent, a fluorine-based leveling agent, a silicone-based leveling agent, etc. The content of the leveling agent in the PDLC layer is, for example, 0.1% by weight to 10% by weight, and preferably 0.5% by weight to 5% by weight.

[0058] Examples of the crosslinking agent include an aziridine-based crosslinking agent, an isocyanate-based crosslinking agent, etc. The content of the crosslinking agent in the PDLC layer is, for example, 0.5% by weight to 20% by weight, and preferably 1% by weight to 10% by weight.

[0059] The average particle size of the liquid crystal droplets is typically 1 μm or less, for example, 0.5 μm or less. A PDLC layer containing liquid crystal droplets with a small particle size exhibits low scattering properties. Therefore, by setting the average particle size of the liquid crystal droplets to 1 μm or less, a PDLC film with high transparency in the transparent state (e.g., a PDLC film with high transparency in the second region B when a voltage is applied) can be obtained. From the viewpoint of achieving higher transparency, the average particle size of the liquid crystal droplets is preferably equal to or less than the wavelength of visible light. Specifically, the average particle size of the liquid crystal droplets is preferably less than 0.38 μm, more preferably less than 0.3 μm, even more preferably less than 0.2 μm, even more preferably 0.18 μm or less, even more preferably 0.15 μm or less, and even more preferably 0.12 μm or less. The lower limit of the average particle size of the liquid crystal droplets may be, for example, 0.01 μm or more or 0.05 μm or more. The average particle diameter of the liquid crystal droplets is the volume-average particle diameter of the liquid crystal droplets when viewed from a direction perpendicular to the main surface of the PDLC film, and can be determined, for example, by the following method. <Method for Measuring the Average Particle Diameter of Liquid Crystal Droplets in a PDLC Layer> The PDLC film is sliced ​​horizontally in a cooled environment, and the horizontal cross section of the exposed PDLC layer is smoothed using a microtome. Next, the horizontal cross section of the PDLC layer is observed using a scanning electron microscope (SEM) to obtain a cross-sectional SEM image. The area-equivalent circle diameter (Heywood diameter) is calculated from the cross-sectional area of ​​all liquid crystal droplets in a predetermined region (e.g., a 30 μm × 20 μm region) in the cross-sectional SEM image, and the volume-average particle diameter (median diameter) is calculated by taking statistics weighted by the estimated volume for each equivalent diameter.

[0060] The thickness of the PDLC layer is typically 2 μm to 40 μm, preferably 3 μm to 35 μm, and more preferably 4 μm to 30 μm.

[0061] A-3. Second Transparent Conductive Film The second transparent conductive film 30 typically includes a second transparent substrate 32 and a second transparent electrode layer 34 provided on one side thereof. The second transparent conductive film 30 may optionally include a hard coat layer on one or both sides of the second transparent substrate 32, and may also include a refractive index adjusting layer between the second transparent substrate 32 and the second transparent electrode layer 34.

[0062] The surface resistance value of the second transparent conductive film is preferably 1 Ω / □ to 1000 Ω / □, more preferably 5 Ω / □ to 300 Ω / □, and even more preferably 10 Ω / □ to 200 Ω / □.

[0063] The haze value of the second transparent conductive film is preferably 20% or less, more preferably 10% or less, and even more preferably 0.1% to 10%.

[0064] The total light transmittance of the second transparent conductive film is preferably 30% or more, more preferably 60% or more, and even more preferably 80% or more.

[0065] The second transparent substrate and the second transparent electrode layer can be described in the same manner as the first transparent substrate and the first transparent electrode layer, respectively. The second transparent conductive film may have the same configuration as the first transparent conductive film, or may have a different configuration.

[0066] A-4. Variation 1 Fig. 2(a) is a schematic plan view of an example of a PDLC film according to another embodiment (second embodiment) of the present invention, Fig. 2(b) is a schematic cross-sectional view illustrating the state of the PDLC film shown in Fig. 2(a) when no voltage is applied, and Fig. 2(c) is a schematic cross-sectional view illustrating the state of the PDLC film shown in Fig. 2(a) when a voltage is applied. The PDLC film 100b includes, in this order, a first transparent conductive film 10, a PDLC layer 20 including a polymer matrix 22 and liquid crystal droplets 24 dispersed in the polymer matrix 22, and a second transparent conductive film 30. The PDLC layer 20 has a first region A in which the liquid crystal droplets 24 include a non-polymerizable liquid crystal component 24a, a liquid crystal polymer 24c, and a dichroic dye 24d, and a second region B in which the liquid crystal droplets 24 include the non-polymerizable liquid crystal component 24a, a polymerizable liquid crystal component 24b, and a dichroic dye 24d.

[0067] As shown in FIG. 2B , in the PDLC film 100b, when no voltage is applied, the liquid crystal polymer 24c in the liquid crystal droplets 24 in the first region A is oriented in a predetermined direction (thickness direction in the illustrated example). The non-polymerizable liquid crystal component 24a and the dichroic dye 24d are also oriented in the same direction due to the orientation restriction imposed by the liquid crystal polymer 24c. Therefore, in the first region A, scattering and absorption of transmitted light are suppressed, resulting in low haze and light coloring. Meanwhile, in the second region B, the non-polymerizable liquid crystal component 24a, the polymerizable liquid crystal component 24b, and the dichroic dye 24d in the liquid crystal droplets 24 are all non-oriented. Therefore, in the second region B, scattering of transmitted light occurs due to the refractive index difference between the polymer matrix and the liquid crystal component, and absorption by the dichroic dye occurs. As a result, in the PDLC film 100b when no voltage is applied, the first region A may be colorless and transparent, and the second region B may be colored and scattered.

[0068] On the other hand, as shown in FIG. 2( c), in the PDLC film 100b, when a voltage is applied, the non-polymerizable liquid crystal component 24a, the liquid crystal polymer 24c, and the dichroic dye 24d in the liquid crystal droplets 24 in the first region A are all oriented in a predetermined direction (thickness direction in the illustrated example). Furthermore, the non-polymerizable liquid crystal component 24a, the polymerizable liquid crystal component 24b, and the dichroic dye 24d in the liquid crystal droplets 24 in the second region B are all oriented in a predetermined direction (thickness direction in the illustrated example). Therefore, in both the first region A and the second region B, scattering and absorption of transmitted light are suppressed, resulting in low haze and light coloring. As a result, the entire main surface of the PDLC film 100b can be colorless and transparent when a voltage is applied.

[0069] In the PDLC film 100b, the change in haze in the first region A due to the application of a voltage is smaller than the change in the second region B, and the difference between the haze in the first region A and the haze in the second region B decreases due to the application of a voltage. Ａ The change in the transmittance T Ａ and the change in transmittance T Ａ and the transmittance T of the second region B Ａ The difference between decreases with the application of voltage.

[0070] The haze of the first region when no voltage is applied is, for example, 1% to 20%, preferably 1% to 10%. The haze of the first region when a voltage is applied is, for example, 1% to 20%, preferably 1% to 10%. The amount of change in haze of the first region due to voltage application (|haze when no voltage is applied−haze when voltage is applied|) is, for example, 0% to 20%, preferably 0% to 10%.

[0071] The haze of the second region when no voltage is applied is, for example, 50% to 100%, preferably 70% to 100%. The haze of the second region when a voltage is applied is, for example, 1% to 20%, preferably 1% to 10%. The amount of change in haze of the second region due to voltage application (|haze when no voltage is applied−haze when voltage is applied|) is, for example, 30% to 99%, preferably 60% to 99%.

[0072] The amount of change in haze in the first region due to application of a voltage is smaller than the amount of change in haze in the second region due to application of a voltage, and the difference is, for example, 10% to 99%, preferably 30% to 99%.

[0073] Transmittance T in the region corresponding to the first region and the region corresponding to the second region of the PDLC film when no voltage is applied Ａ can vary depending on the type and blending ratio of the dichroic dye, and can be appropriately set depending on the purpose.

[0074] Transmittance T of the first region when no voltage is applied Ａ The transmittance T of the first region when a voltage is applied is, for example, 45% to 95%, and preferably 65% ​​to 95%. Ａ is, for example, 45% to 95%, preferably 65% ​​to 95%. Ａ The change in transmittance when no voltage is applied (| Ａ -Transmittance T when voltage is applied Ａ |) is, for example, 0% to 10%, and also, for example, 0% to 5%.

[0075] Transmittance T of the second region when no voltage is applied Ａ The transmittance T of the second region when a voltage is applied is, for example, 40% to 90%, and preferably 40% to 70%. Ａ The transmittance T of the second region due to the application of a voltage is, for example, 45% to 95%, and preferably 60% to 95%. Ａ The change in transmittance when no voltage is applied (| Ａ -Transmittance T when voltage is applied Ａ |) is, for example, 5% to 30%, and also, for example, 5% to 20%.

[0076] Transmittance T of the first region by applying a voltage Ａ and the transmittance T of the second region due to the application of voltage Ａ The difference from the change amount is, for example, 5% to 25%, or, for example, 5% to 20%.

[0077] The thickness of the PDLC film is, for example, 30 μm to 250 μm, preferably 50 μm to 150 μm.

[0078] Regarding the PDLC film of the second embodiment, the same explanations as for the first transparent conductive film and the second transparent conductive film in the PDLC film of the first embodiment can be applied to the first transparent conductive film and the second transparent conductive film, respectively. Furthermore, the same explanations as for the PDLC layer in the PDLC film of the first embodiment can be applied to the PDLC layer, except that the liquid crystal polymer contained in the liquid crystal droplets in the first region is oriented in a predetermined direction.

[0079] When no voltage is applied, the liquid crystal polymer contained in the liquid crystal droplets in the first region of the PDLC layer is oriented in a predetermined direction. Preferred examples of the orientation direction of the liquid crystal polymer include the thickness direction and a direction perpendicular to the thickness direction. The thickness direction may be at an angle of, for example, 90°±5°, preferably 90°±3°, relative to the main surface of the transparent conductive film 10 or 30.

[0080] A-5. Variation 2: A PDLC film according to another embodiment of the present invention further includes a reflective layer disposed on the side opposite the viewing side of the PDLC film (specifically, on the side opposite the side of the first or second transparent conductive film on which the PDLC layer is disposed). When a PDLC film having such a configuration is observed from the viewing side, light incident from the viewing side and reflected by the reflective layer while being suppressed from being absorbed (colored) and scattered by the PDLC layer can be observed in the colorless and transparent state region. Thus, the PDLC film can exhibit a clear appearance in the colorless and transparent state region. On the other hand, in the colored and scattering state region, light incident on the PDLC film and reflected by the reflective layer is absorbed (colored) and scattered by the PDLC layer. Thus, the PDLC film can exhibit a colored, opaque, matte appearance in the colored and scattering state region.

[0081] 3(a) and 3(b) are schematic cross-sectional views illustrating the state of an example of a PDLC film of this embodiment when no voltage is applied and when a voltage is applied, respectively. The PDLC film 100c includes a reflective layer 40, a first transparent conductive film 10, a PDLC layer 20, and a second transparent conductive film 30, in this order. In this case, the second transparent conductive film 30 side of the PDLC film 100c is the viewing side. The reflective layer 40 is laminated to the first transparent conductive film via an adhesive layer (not shown), such as an adhesive layer or a pressure-sensitive adhesive layer. In the PDLC film 100c, the PDLC layer 20 has a first region A in which the liquid crystal droplets 24 contain a non-polymerizable liquid crystal component 24a, a liquid crystal polymer 24c, and a dichroic dye 24d, and a second region B in which the liquid crystal droplets 24 contain a non-polymerizable liquid crystal component 24a, a polymerizable liquid crystal component 24b, and a dichroic dye 24d.

[0082] As shown in Figure 3(a), in the PDLC film 100c when no voltage is applied, both the first region A and the second region B of the PDLC layer 20 are in a colored and scattered state. Therefore, when the PDLC film 100c is observed from the viewing side when no voltage is applied, a colored, opaque, matte appearance can be observed across the entire surface. On the other hand, as shown in Figure 3(b), in the PDLC film 100c when a voltage is applied, the first region A of the PDLC layer 20 is in a colored and scattered state, and the second region B is in a colorless, transparent state. Therefore, when the PDLC film 100c is observed from the viewing side when a voltage is applied, a colored, opaque, matte appearance can be observed in the first region A, and a highly transparent, uncolored or lightly colored, clear appearance can be observed in the second region B.

[0083] The configuration of the PDLC layer 20 is not limited to the illustrated example. The PDLC layer 20 may have the same configuration as the PDLC layer 20 included in the PDLC film 100b, or may be configured using a liquid crystal component having negative dielectric anisotropy.

[0084] The reflective layer reflects light incident on the viewing side of the PDLC film. The reflective layer may be transmissive, i.e., may be a semi-transmissive reflective layer.

[0085] The total light reflectance of the reflective layer is, for example, 50% or more, preferably 60% or more, and more preferably 70% to 95%.

[0086] When the reflective layer has transparency, its total light reflectance may be, for example, 30% to 60%, preferably 40% to 50%, and its total light transmittance may be, for example, 40% to 70%, preferably 50% to 60%.

[0087] Any appropriate configuration can be adopted for the reflective layer. For example, the reflective layer may be a specular reflective layer or a diffuse reflective layer. The use of a specular reflective layer can enhance the change in appearance of the PDLC film when the PDLC layer is in a colorless, transparent state and a colored, scattering state. The specular reflectance of the reflective layer can be, for example, 25% or more, preferably 40% to 95%. Furthermore, the use of a reflective layer with metallic luster can impart a metallic luster to the appearance of the PDLC film.

[0088] Specific examples of the reflective layer include a resin sheet with high reflectivity (for example, an acrylic plate), a thin metal plate or metal foil of aluminum, stainless steel, or the like, a vapor-deposited sheet in which aluminum, silver, or the like is vapor-deposited on a substrate such as a resin film of polyester, or the like, a laminate of a substrate such as a resin film of polyester, or the like, and a metal foil of aluminum, or the like, and a resin film with holes (voids) formed inside.

[0089] The thickness of the reflective layer can be appropriately set depending on the application, etc. The thickness of the reflective layer is, for example, 20 μm to 300 μm, and preferably 30 μm to 100 μm.

[0090] B. Method for Manufacturing a Polymer-Dispersed Liquid Crystal Film The PDLC film described in Section A can be manufactured by any suitable manufacturing method. In one embodiment, the method for manufacturing a PDLC film includes: (Step A) applying a coating liquid containing a polymer matrix-forming resin, a non-polymerizable liquid crystal component, a polymerizable liquid crystal component, a dichroic dye, and a solvent to a first transparent conductive film to obtain a coating layer; (Step B) drying the coating layer to obtain a PDLC layer containing a polymer matrix and liquid crystal droplets containing the non-polymerizable liquid crystal component, the polymerizable liquid crystal component, and the dichroic dye dispersed in the polymer matrix; (Step C) laminating a second transparent conductive film on the PDLC layer; and (Step D) irradiating the PDLC layer with active energy rays in a predetermined pattern to form first regions containing liquid crystal droplets containing a liquid crystal polymer that is a polymerization product of the non-polymerizable liquid crystal component and the polymerizable liquid crystal component, and the dichroic dye. According to the above-described method for producing a PDLC film, a PDLC layer can be formed having a first region in which the liquid crystal droplets contain a non-polymerizable liquid crystal component, a liquid crystal polymer, and a dichroic dye, and a second region in which the liquid crystal droplets contain a non-polymerizable liquid crystal component, a polymerizable liquid crystal component, and a dichroic dye, and as a result, the PDLC film described in Section A can be suitably obtained.

[0091] In one embodiment, the active energy ray irradiation in step D is performed in a state where no voltage is applied between the first transparent conductive film and the second transparent conductive film. In another embodiment, the active energy ray irradiation in step D is performed in a state where a voltage is applied between the first transparent conductive film and the second transparent conductive film.

[0092] B-1. Step A In step A, a coating liquid containing a polymer matrix-forming resin, a non-polymerizable liquid crystal component, a polymerizable liquid crystal component, a dichroic dye, and a solvent is applied to a first transparent conductive film to obtain a coating layer.

[0093] The coating liquid is preferably an emulsion in which liquid crystal particles containing a non-polymerizable liquid crystal component, a polymerizable liquid crystal component, and a dichroic dye are dispersed in a solvent (hereinafter, this may be referred to as an "emulsion coating liquid"). In one embodiment, the coating liquid is an emulsion coating liquid in which polymer matrix-forming resin particles and liquid crystal particles containing a non-polymerizable liquid crystal component, a polymerizable liquid crystal component, and a dichroic dye are dispersed in a solvent. The emulsion coating liquid preferably further contains a polymerization initiator and may further contain any appropriate additives depending on the purpose.

[0094] The solvent is preferably water or a mixed solvent of water and a water-miscible organic solvent. Examples of the water-miscible organic solvent include C1-3 alcohol, acetone, and DMSO. The polymer matrix-forming resin, non-polymerizable liquid crystal component, polymerizable liquid crystal component, dichroic dye, and additives, as well as their content ratios, are as described in Section A.

[0095] The average particle size of the liquid crystal particles is typically 1 μm or less, for example, 0.5 μm or less, preferably less than 0.38 μm, more preferably less than 0.3 μm, even more preferably less than 0.2 μm, still more preferably 0.18 μm or less, still more preferably 0.15 μm or less, even more preferably 0.12 μm or less, and may be, for example, 0.01 μm or more or 0.05 μm or more. The average particle size of the liquid crystal particles is a volume average particle size.

[0096] The particle size of the liquid crystal particles preferably has a relatively narrow particle size distribution. The coefficient of variation (CV value) of the liquid crystal particles may be, for example, less than 0.4, preferably 0.35 or less, and more preferably 0.3 or less.

[0097] The average particle size of the resin particles for forming a polymer matrix is ​​preferably 10 nm to 500 nm, more preferably 30 nm to 300 nm, and even more preferably 50 nm to 200 nm. Two or more types of resin particles differing in type and / or average particle size may be used. The average particle size of the resin particles for forming a polymer matrix means the volume-average median size and can be measured using a dynamic light scattering particle size distribution analyzer.

[0098] The emulsion coating liquid can be prepared, for example, by mixing a resin emulsion or resin solution containing polymer matrix-forming resin particles, a liquid crystal emulsion containing liquid crystal particles, and optional additives. If necessary, a solvent may be added during mixing. Alternatively, the emulsion coating liquid can be prepared by adding a non-polymerizable liquid crystal component, a polymerizable liquid crystal component, a dichroic dye, polymer matrix-forming resin particles, and optional additives to a solvent and mechanically dispersing the mixture.

[0099] The resin emulsion and liquid crystal emulsion can be prepared by, for example, a mechanical emulsification method, a microchannel method, a membrane emulsification method, or the like. Among these, it is preferable to prepare the liquid crystal emulsion by the membrane emulsification method. The membrane emulsification method can suitably produce an emulsion with a uniform particle size distribution. For details of the membrane emulsification method, reference can be made to the disclosures of JP-A-4-355719, JP-A-2015-40994, and the like (these are incorporated herein by reference).

[0100] The solid content of the emulsion coating liquid may be, for example, 20% to 60% by weight, and preferably 30% to 50% by weight.

[0101] The viscosity of the emulsion coating liquid can be appropriately adjusted so that application to the first transparent conductive film is performed smoothly. The viscosity of the emulsion coating liquid during application is preferably 20 mPa·s to 400 mPa·s, more preferably 30 mPa·s to 300 mPa·s, and even more preferably 40 mPa·s to 200 mPa·s. If the viscosity is less than 20 mPa·s, solvent convection may become significant during drying, potentially resulting in an unstable PDLC layer thickness. Furthermore, if the viscosity exceeds 400 mPa·s, the beading of the emulsion coating liquid may become unstable. The viscosity of the emulsion coating liquid can be measured, for example, using an Anton Paar MCR302 rheometer. The viscosity used here refers to the shear viscosity value measured at 20°C and a shear rate of 1000 (1 / s).

[0102] The emulsion coating liquid is typically applied to the surface of the first transparent conductive film on the transparent electrode layer side. The first transparent conductive film is as described in Section A.

[0103] Any appropriate method can be used as the coating method. For example, roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, knife coating (comma coating, etc.), etc. can be mentioned. Among them, roll coating is preferred. For example, with regard to coating by roll coating using a slot die, the description in JP-A-2019-5698 can be referred to.

[0104] The thickness of the coating layer is preferably 3 μm to 40 μm, more preferably 4 μm to 30 μm, and even more preferably 5 μm to 20 μm. Within these ranges, a PDLC layer with excellent thickness uniformity can be obtained.

[0105] B-2. Step B In step B, the coating layer is dried to obtain a PDLC layer containing a polymer matrix and liquid crystal droplets containing a non-polymerizable liquid crystal component, a polymerizable liquid crystal component, and a dichroic dye dispersed in the polymer matrix. The solvent is removed from the coating layer by drying, forming a PDLC layer having a structure in which liquid crystal droplets are dispersed in a polymer matrix.

[0106] The coating layer can be dried by any appropriate method. Specific examples of the drying method include natural drying, heat drying, hot air drying, etc. When the emulsion coating liquid contains a crosslinking agent, a crosslinked structure of the polymer matrix can be formed during drying.

[0107] The drying temperature is preferably 20° C. to 150° C., more preferably 25° C. to 80° C. The drying time is preferably 1 minute to 100 minutes, more preferably 2 minutes to 10 minutes.

[0108] B-3. ​​Step C In step C, a second transparent conductive film is laminated on the PDLC layer, thereby obtaining a PDLC film having the first transparent conductive film, the PDLC layer, and the second transparent conductive film in this order.

[0109] The second conductive film is as described in Section A. The second transparent conductive film is laminated onto the PDLC layer so that the second transparent electrode layer faces the PDLC layer. From the viewpoint of obtaining sufficient adhesion, the lamination is preferably performed using a laminator while applying a lamination pressure of 0.006 MPa / m to 7 MPa / m, more preferably 0.06 MPa / m to 0.7 MPa / m.

[0110] B-4. Step D In step D, the PDLC layer is irradiated with active energy rays in a predetermined pattern to form first regions containing liquid crystal droplets containing a non-polymerizable liquid crystal component, a liquid crystal polymer (a polymerization product of a polymerizable liquid crystal component), and a dichroic dye. Specifically, in the regions irradiated with active energy rays (irradiated regions), the polymerizable liquid crystal component in the liquid crystal droplets polymerizes to form a liquid crystal polymer, resulting in the formation of liquid crystal droplets containing a non-polymerizable liquid crystal component, a liquid crystal polymer, and a dichroic dye. On the other hand, in the regions not irradiated with active energy rays (non-irradiated regions), the polymerizable liquid crystal component remains unreacted, resulting in the liquid crystal droplets containing a non-polymerizable liquid crystal component, a polymerizable liquid crystal component, and a dichroic dye. Thus, the irradiated regions of the PDLC layer become the first regions A, and the non-irradiated regions become the second regions B. The liquid crystal polymer contained in the liquid crystal droplets in the first regions A is a polymerization product of the polymerizable liquid crystal component contained in the liquid crystal droplets in the second regions B. In addition, the content ratio of the non-polymerizable liquid crystal component, the polymerizable liquid crystal component, and the dichroic dye in the liquid crystal droplets in the non-irradiated area can roughly correspond to the content ratio at the time when the liquid crystal droplets are first formed, i.e., the content ratio of the non-polymerizable liquid crystal component, the polymerizable liquid crystal component, and the dichroic dye in the coating liquid.

[0111] The active energy rays are irradiated through a photomask having a predetermined pattern. Examples of the active energy rays include ultraviolet rays, infrared rays, X-rays, α rays, β rays, γ rays, and electron beams. Among these, ultraviolet rays are preferred. Furthermore, the active energy rays are preferably collimated rays that have a high degree of linearity from the irradiation source.

[0112] The ultraviolet irradiation conditions can be appropriately set depending on the type of polymerizable liquid crystal component, the transmittance of the transparent conductive film, the absorption wavelength of the photopolymerization initiator, etc. The irradiation intensity is, for example, 0.1 mW / cm ２ ~1000mW / cm ２ , preferably 1 mW / cm ２ ~100mW / cm ２ The irradiation dose can be, for example, 10 mJ / cm ２ ~10000mJ / cm ２ , preferably 100 mJ / cm ２ ~5000mJ / cm ２ The irradiation temperature may be, for example, from -20°C to 80°C, preferably from -20°C to 60°C.

[0113] 4 and 5 are schematic diagrams illustrating an example of active energy ray irradiation in a method for producing a PDLC film according to an embodiment of the present invention. In the embodiment shown in FIG. 4, active energy ray irradiation is performed through a photomask 200 without applying a voltage between the first transparent conductive film 10 and the second transparent conductive film 30. According to this embodiment, in the liquid crystal droplets 24 in the irradiated region of the PDLC layer 20, the polymerizable liquid crystal component 24b is polymerized in a non-oriented state, and the resulting liquid crystal polymer 24c is also non-oriented. Therefore, according to this embodiment, the PDLC film 100a described in Section A can be suitably obtained.

[0114] In the embodiment shown in FIG. 5 , active energy ray irradiation is performed with a voltage applied between the first transparent conductive film 10 and the second transparent conductive film 30 via a photomask 200. According to this embodiment, in the liquid crystal droplets 24 in the irradiated region of the PDLC layer 20, the polymerizable liquid crystal component 24b is polymerized while oriented in a predetermined direction (thickness direction in the illustrated example) along the electric field, thereby forming a liquid crystal polymer 24c with this orientation fixed. Therefore, this embodiment can suitably obtain the PDLC film 100b described in Section A. The voltage applied during active energy ray irradiation is not limited as long as the desired orientation (in other words, the desired haze in the first region) is achieved, and can be, for example, 10 V to 200 V, preferably 20 V to 100 V.

[0115] In one embodiment, by irradiating the PDLC film with active energy rays using a photomask having a plurality of light-transmitting portions with different aperture ratios, the first regions can be formed in the regions corresponding to the light-transmitting portions at a ratio corresponding to the aperture ratios of the first regions, and therefore, in the resulting PDLC film, the regions corresponding to the light-transmitting portions can exhibit a haze corresponding to the aperture ratios of the first regions when viewed as a whole.

[0116] For example, by using a photomask whose aperture ratio increases continuously from the right end to the left end and irradiating with active energy rays without applying a voltage, a PDLC film can be obtained in which the entire surface is in a colored and scattered state when no voltage is applied, and the haze and color degree increase continuously from the right end to the left end when a voltage is applied.Furthermore, by using a photomask whose aperture ratio increases continuously from the right end to the left end and irradiating with active energy rays while applying a voltage, a PDLC film can be obtained in which the entire surface is in a colorless and transparent state when a voltage is applied, and the haze and color degree decrease continuously from the right end to the left end when no voltage is applied.

[0117] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring each property are as follows. Unless otherwise specified, "parts" and "%" in the examples and comparative examples are by weight.

[0118] (1) Thickness: Measured using a digital micrometer (manufactured by Anritsu Corporation, product name "KC-351C"). (2) Volume average particle diameter of liquid crystal particles in liquid crystal emulsion: The volume average particle diameter was calculated using a particle size distribution measuring device (manufactured by Microtrac, product name "MT3300EXII"). (3) Average particle diameter of resin particles: A measurement sample was prepared by adding a few drops of resin dispersion to 100 mL of water. Using a dynamic light scattering particle size distribution measuring device (manufactured by Microtrac, product name "Nanotrac150"), the measurement sample was placed in the measurement holder of the device, and measurements were performed after confirming on the device monitor that the concentration was measurable. (4) Haze: Measured using a haze meter (manufactured by Nippon Denshoku Co., Ltd., product name "NDH4000") in accordance with JIS K 7136. (5) Transmittance: Transmittance was measured in accordance with JIS K 7361 using an ultraviolet-visible-near infrared spectrophotometer (manufactured by Hitachi High-Tech Corporation, product name "UH4150").

[0119] [Example 1] (First and second transparent conductive films) An ITO layer was formed on one surface of a PET substrate (thickness: 50 μm) by a sputtering method to obtain a transparent conductive film having a structure of [transparent substrate / transparent electrode layer].

[0120] (Preparation of emulsion coating liquid) 53.7 parts of a non-polymerizable liquid crystal component (manufactured by JNC Corporation, product name "LX-153XX", birefringence Δn = 0.149 (ne = 1.651, no = 1.502), viscosity = 48.5 mPa s), 5.9 parts of a polymerizable liquid crystal component (manufactured by BASF Corporation, product name "PALIOCOLOR LC-242"), 0.1 parts of a dichroic dye (manufactured by Hayashibara Co., Ltd., product name "G470"), 0.1 parts of a photopolymerization initiator (manufactured by IGM, product name "OMNIRAD651"), 39.8 parts of pure water, and 0.5 parts of a dispersant (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., "Noigen ET159") were mixed and stirred with a homogenizer at 100 rpm for 10 minutes to prepare a liquid crystal emulsion. The average particle size of the liquid crystal particles in the obtained liquid crystal emulsion was 3.4 μm. 38.4 parts of the liquid crystal emulsion, 19.1 parts of a polyether-based polyurethane resin aqueous dispersion (manufactured by DSM, trade name "NeoRez R967", polymer average particle size: 80 nm, CV value = 0.27, solid content: 40 wt%), 17.0 parts of a polyester-based polyurethane resin aqueous dispersion (manufactured by Sanyo Chemical Industries, trade name "Eucoat C-102", polymer average particle size: 168 nm, CV value = 0.23, solid content: 45 wt%), 0.1 parts of a leveling agent (manufactured by DIC, product name "F-444"), 1.1 parts of a crosslinking agent (tris[3-(2-methylaziridin-1-yl)propionic acid]=propylidinetrimethyl), and 24.3 parts of pure water were mixed to obtain an emulsion coating liquid (solid content concentration: 40 wt%).

[0121] (Application and Drying of Emulsion Coating Liquid) The emulsion coating liquid was applied to the ITO layer surface of the first transparent conductive film to form a coating layer with a thickness of 20 μm. The coating was performed using a slot die at a line speed of 6 m / min. The coating layer was then dried at 25° C. for 8 minutes to form a PDLC layer with a thickness of 8 μm.

[0122] (Lamination of Second Transparent Conductive Film) Using a laminator, a second transparent conductive film was laminated on the PDLC layer with the ITO layer facing the PDLC layer under a lamination pressure of 0.4 MPa / m, thereby obtaining a PDLC film.

[0123] (Irradiation with active energy rays) On both sides of the PDLC film, a portion of the transparent conductive film was half-cut down to the transparent substrate to expose the transparent electrode layer, and the exposed portion was used as an extraction electrode. A photomask having a predetermined pattern was placed on the electrode-treated PDLC film, and the film was irradiated with 10 mW / cm irradiance under a UV-LED lamp (manufactured by Hamamatsu Photonics, product name "C11924-101", peak wavelength 365 nm) while applying a voltage of 50 V. ２ The resulting PDLC film was in a colorless and transparent state in the irradiated area and in a colored and scattering state in the non-irradiated area when no voltage was applied.

[0124] [Example 2] A PDLC film was obtained in the same manner as in Example 1, except that ultraviolet irradiation was performed without applying a voltage (applied voltage: 0 V). The obtained PDLC film was in a colored and scattering state in both the irradiated and non-irradiated regions when no voltage was applied.

[0125] The haze and transmittance were measured in the irradiated and non-irradiated areas of the PDLC films obtained in the examples when an AC voltage of 0 V to 50 V was applied to the PDLC films using an AC power supply "EC750SA" manufactured by NF Corporation.

[0126] As a result, in the PDLC film of Example 1, the haze and color state in the non-irradiated region were significantly reduced by application of voltage, and both the irradiated and non-irradiated regions became colorless and transparent. In addition, in the PDLC film of Example 2, the haze and color state in the non-irradiated region were significantly reduced by application of voltage, becoming colorless and transparent, while the irradiated region remained colored and scattered. From the above, it was confirmed that in all of the PDLC films obtained in the examples, the change in haze and the change in transmittance at the absorption peak wavelength (432 nm) of the dichroic dye due to application of voltage in the first region (irradiated region) were smaller than the change in the second region (non-irradiated region).

[0127] The PDLC film of the present invention is suitably used in various applications such as displays such as advertisements and guide boards, and smart windows.

[0128] 100 PDLC film 10 First transparent conductive film 20 PDLC layer 22 Polymer matrix 24 Liquid crystal droplets 24a Non-polymerizable liquid crystal component 24b Polymerizable liquid crystal component 24c Liquid crystal polymer 24d Dichroic dye 30 Second transparent conductive film

Claims

1. A polymer dispersed liquid crystal film comprising, in this order, a first transparent conductive film, a polymer dispersed liquid crystal layer containing a polymer matrix and liquid crystal droplets dispersed in the polymer matrix, and a second transparent conductive film, wherein the polymer dispersed liquid crystal layer has a first region in which the liquid crystal droplets contain a non-polymerizable liquid crystal component, a liquid crystal polymer, and a dichroic dye, and a second region in which the liquid crystal droplets contain a non-polymerizable liquid crystal component, a polymerizable liquid crystal component, and a dichroic dye.

2. The polymer dispersed liquid crystal film according to claim 1, wherein the change in transmittance at the absorption peak wavelength of the dichroic dye in the first region due to application of a voltage is smaller than the change in the transmittance in the second region.

3. The polymer dispersed liquid crystal film according to claim 1, wherein the average particle size of the liquid crystal droplets is 1 μm or less.

4. The polymer dispersed liquid crystal film according to claim 1, wherein the content of said liquid crystal polymer in said first region is 1 part by weight to 30 parts by weight per 100 parts by weight of said non-polymerizable liquid crystal component.

5. The polymer dispersed liquid crystal film according to claim 1, wherein the content of the dichroic dye in the first region is 0.1 to 10 parts by weight per 100 parts by weight of the non-polymerizable liquid crystal component.

6. The polymer dispersed liquid crystal film according to claim 1, wherein the difference between the haze of the first region and the haze of the second region increases with the application of a voltage.

7. The polymer dispersed liquid crystal film according to claim 1, wherein the difference between the haze of the first region and the haze of the second region is reduced by application of a voltage.

8. The polymer dispersed liquid crystal film of claim 1, further comprising a reflective layer on the side of the first transparent conductive film or the second transparent conductive film opposite to the side on which the polymer dispersed liquid crystal layer is disposed.

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