Diffusion film and light diffusion device

Abstract

A diffusion film according to the present invention includes a diffusion layer including a polymer matrix and diffused particles that are dispersed in the polymer matrix and each include a liquid crystal polymer that is a polymer of a polymerizable liquid crystal component and a non-polymerizable liquid crystal component as an optional component. The diffusion layer has an A1 region that exhibits a maximum straight transmitted light intensity at an incident angle of θ° (where θ>0), and a B1 region that exhibits a maximum straight transmitted light intensity at an incident angle of 0°. In the A1 region and the B1 region, the respective orientation states and / or content ratios of the liquid crystal polymer in the dispersed particle are different from each other.

Description

Diffusion film and light diffusion device

[0001] The present invention relates to a diffusion film and a light diffusion device.

[0002] A polymer dispersed liquid crystal (hereinafter, sometimes referred to as "PDLC") layer containing a polymer matrix and droplets of a liquid crystal component dispersed therein (hereinafter, sometimes referred to as "liquid crystal droplets") can cause light scattering because the liquid crystal droplets act as scattering particles due to the difference in refractive index between the polymer matrix and the liquid crystal component.

[0003] By utilizing the light scattering effect, the PDLC film can be used as a diffusion film. For example, Patent Document 1 proposes using a PDLC film as a diffusion film for a direct backlight.

[0004] JP 2011-008005 A

[0005] A diffusion film may be required to have a predetermined light distribution pattern, but it is difficult to control the light distribution in a diffusion film using the PDLC layer.

[0006] The primary object of the present invention is to provide a diffusion film with controlled light distribution, and a further object is to provide a diffusion film with patterned light distribution.

[0007] [1] According to one aspect of the present invention, there is provided a diffusion film including a polymer matrix and a diffusion layer including dispersed particles dispersed in the polymer matrix, the dispersed particles including a liquid crystal polymer, which is a polymer of a polymerizable liquid crystal component, and an optional non-polymerizable liquid crystal component. The diffusion layer has an A1 region showing the maximum intensity of straight-transmitted light at an incident angle of θ° (where θ > 0), and a B1 region showing the maximum intensity of straight-transmitted light at an incident angle of 0°. The orientation state and / or content ratio of the liquid crystal polymer contained in the dispersed particles in the A1 region and the B1 region are different from each other. [2] The diffusion film described in [1] above may include the liquid crystal polymer in which the dispersed particles are oriented in a predetermined direction in the A1 region. [3] In the diffusion film described in [2] above, the predetermined direction may be the thickness direction or a direction perpendicular to the thickness direction. [4] The diffusion film described in any one of [1] to [3] above may be configured such that the average ordinary refractive index of the polymerizable liquid crystal component and the non-polymerizable liquid crystal component is no ａ , the average extraordinary refractive index is ne ａ When the refractive index of the polymer matrix is ​​np, no ａ <np<ne ａ [5] The diffusion film according to the above item [4] may satisfy the relationship: 0.01≦np−n ａ and / or 0.01≦ne ａ -np。 [6] In the diffusion film according to any one of [1] to [5] above, the content ratio of the liquid crystal polymer to the total content of the liquid crystal polymer and the non-polymerizable liquid crystal component in the A1 region may be 5 wt % or more. [7] According to another aspect of the present invention, the diffusion film includes a diffusion layer including a polymer matrix and dispersed particles that are dispersed in the polymer matrix and contain a liquid crystal polymer that is a polymer of a polymerizable liquid crystal component and a non-polymerizable liquid crystal component as an optional component, and the average ordinary refractive index of the polymerizable liquid crystal component and the non-polymerizable liquid crystal component is no ａ , the average extraordinary refractive index is ne ａ When the refractive index of the polymer matrix is ​​np, no ａ <np<ne ａ

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0040]

[0038]

[0041]

[0039]

[0042]

[0043]

[0044]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0070]

[0071]

[0072]

[0073]

[0074]

[0080]

[0081]

[0082]

[0083]

[0084]

[0090]

[0091]

[0092]

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

[0099]

[100]

[0099]

[110]

[111]

[0099]

[0099]

[0099]

[0100]

[0099]

[0099]

[0099]

[0101]

[0099]

[0099]

[0099]

[0099]

[0102]

[0099]

[0099] [009

[0008] According to the present invention, a diffusion film can be provided that has a region exhibiting a light distribution characteristic in which the rectilinear transmitted light intensity of light incident from an oblique direction is higher than the rectilinear transmitted light intensity of light incident from a front direction. The diffusion film can further have a region exhibiting a light distribution characteristic in which the rectilinear transmitted light intensity of light incident from a front direction is higher than the rectilinear transmitted light intensity of light incident from an oblique direction. Furthermore, these regions can be formed in a desired pattern.

[0009] FIG. 1A is a schematic top view of an example of a diffusion film according to an embodiment of the present invention. FIG. 1B is a schematic cross-sectional view illustrating the configuration of the diffusion film shown in FIG. 1A. FIG. 2 is a schematic view illustrating the light distribution of the diffusion film shown in FIGS. 1A and 1B. FIGS. 3(a) and 3(b) are schematic views illustrating step III of an example of a method for manufacturing a diffusion film. FIG. 4 is a schematic cross-sectional view illustrating the configuration of another example of a diffusion film according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view illustrating the configuration of another example of a diffusion film according to an embodiment of the present invention. FIG. 6 is a schematic cross-sectional view showing the configuration of a light diffusion device according to one embodiment of the present invention. FIG. 7 is a graph showing the results of measuring the light distribution of a diffusion film.

[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. Diffusion Film Figures 1A and 1B are a schematic top view and a schematic cross-sectional view, respectively, illustrating the configuration of an example of a diffusion film according to an embodiment of the present invention. Figure 2 is a schematic view illustrating the light distribution of the diffusion film shown in Figure 1.

[0012] The diffusion film 100A shown in FIGS. 1A and 1B includes a diffusion layer 110, a first support substrate 120 disposed on one side of the diffusion layer 110, and a second support substrate 130 disposed on the other side. The diffusion layer 110 has an A1 region including a polymer matrix 10 and dispersed particles 20 containing a liquid crystal polymer 22, which is a polymer of a polymerizable liquid crystal component, and a non-polymerizable liquid crystal component 26, dispersed in the polymer matrix 10; and a B1 region including the polymer matrix 10 and dispersed particles 20 containing a polymerizable liquid crystal component 24 and a non-polymerizable liquid crystal component 26, dispersed in the polymer matrix 10. The liquid crystal polymer 22 is a polymer of a polymerizable liquid crystal component and is non-liquid crystal. That is, the liquid crystal polymer 22 does not undergo, for example, a transition to a liquid crystal phase, glass phase, or crystalline phase due to temperature changes, which is typical of liquid crystal compounds. The non-polymerizable liquid crystal component 26 is an optional component, and the dispersed particles 20 do not necessarily contain the non-polymerizable liquid crystal component 26.

[0013] As shown in FIGS. 1A and 1B , in the A1 region, the dispersed particles 20 contain a liquid crystal polymer 22 oriented in a predetermined direction (the thickness direction in the illustrated example). Meanwhile, in the B1 region, the dispersed particles 20 contain a polymerizable liquid crystal component 24 in a non-oriented state. The content of the liquid crystal polymer 22 in the B1 region is lower than the content of the liquid crystal polymer 22 in the A1 region. For example, the dispersed particles 20 in the B1 region may be substantially free of the liquid crystal polymer 22. Furthermore, in the A1 region, the non-polymerizable liquid crystal component 26 in the dispersed particles 20 is oriented along the orientation of the liquid crystal polymer 22, while in the B1 region, the non-polymerizable liquid crystal component 26 in the dispersed particles 20 is present in a non-oriented state, similar to the polymerizable liquid crystal component 24. In this specification, with respect to compounds such as liquid crystal polymers and liquid crystal components, the term "non-oriented state" refers to a state in which the molecules of the compound are not aligned with a certain regularity. Furthermore, with respect to the diffusion layer or diffusion film, the "thickness direction" may include a direction that forms an angle of, for example, 90°±2° or, for example, 90°±3° with respect to the principal surface thereof.

[0014] As will be described later, the polymerizable liquid crystal component 24, the non-polymerizable liquid crystal component 26, and the polymer matrix 10 are typically ａ <np<ne ａ (no ａ is the average ordinary refractive index of the polymerizable liquid crystal component and the non-polymerizable liquid crystal component, and ne ａ is the average extraordinary refractive index of the polymerizable liquid crystal component and the non-polymerizable liquid crystal component, and np is the refractive index of the polymer matrix. The liquid crystal polymer 22 is a polymer of the polymerizable liquid crystal component 24, and exhibits the same refractive index characteristics as the polymerizable liquid crystal component 24. Therefore, in the A1 region of the diffusion layer 110, the incident light from the front direction is reflected by the difference between the refractive index of the polymer matrix 10 and the refractive index of the dispersed particles 20 (specifically, no ａ and the difference between np or ne ａand np), scattering occurs. On the other hand, light incident at an angle where the difference between the refractive index of the polymer matrix 10 and the refractive index of the dispersed particles 20 is small is suppressed from scattering, and can exhibit a higher straight-line transmission intensity than the straight-line transmission intensity of light incident at an incident angle of 0°. Therefore, as shown in FIG. 2, in the diffusion film 100A (more specifically, the diffusion layer 110), in the A1 region, light incident at a predetermined incident angle θ° (where θ > 0) exhibits the maximum straight-line transmission intensity, while the straight-line transmission intensity of light incident from the front direction (incident angle 0°) is lower. On the other hand, in the B1 region, the dispersed particles 20 contain non-oriented polymerizable liquid crystal components 24 and non-polymerizable liquid crystal components 26, allowing the incident light to be uniformly dispersed. Therefore, the straight-line transmission intensity decreases with the optical path length, and the straight-line transmission intensity of light incident from the front direction is the highest. Conventional PDLC layers are generally made using a liquid crystal component and a polymer matrix that satisfy the relationship np≒no<ne, and do not achieve a light distribution like that of the A1 region. The angle θ can be adjusted depending on the purpose, for example, from 10° to 80°, from 15° to less than 45°, or from 20° to 40°, or from more than 45° to 75° or from 50° to 70°. The angle θ can be adjusted to control the light distribution by, for example, changing the difference between the refractive index of the polymer matrix and the refractive index of the liquid crystal component.

[0015] The haze of the region of the diffusion film corresponding to the A1 region of the diffusion layer in plan view (hereinafter sometimes referred to as the A1 region of the diffusion film) and the haze of the region of the diffusion layer corresponding to the B1 region of the diffusion layer (hereinafter sometimes referred to as the B1 region of the diffusion film) can each be appropriately set according to the purpose. The haze of the A1 region of the diffusion film can be, for example, 30.0% to 99.9%, or may be 40.0% to 70.0%, or 60.0% to 90.0%. The haze of the B1 region of the diffusion film can be, for example, 20.0% to 99.9%, or may be 30.0% to 70.0%, or 60.0% to 99.9%.

[0016] The total light transmittance of the A1 region and the total light transmittance of the B1 region of the diffusion film can each be appropriately set depending on the purpose. The total light transmittance of the A1 region of the diffusion film can be, for example, 40% to 95%, and may be 60% to 80%, or 70% to 90%. The total light transmittance of the B1 region of the diffusion film can be, for example, 40% to 95%, and may be 60% to 80%, or 70% to 90%. The total light transmittance can be measured, for example, in accordance with JIS K 7361.

[0017] When the incident angle at which the maximum straight-transmitted light intensity is obtained in the A1 region of the diffusion film is defined as θ°, the ratio of the straight-transmitted light intensity at an incident angle of 0° to the straight-transmitted light intensity at an incident angle of θ° can be appropriately set depending on the purpose, and may be, for example, 0.05 to 0.9, 0.2 to 0.9, or 0.1 to 0.4.

[0018] The thickness of the diffusion film is, for example, 30 μm to 250 μm, preferably 40 μm to 150 μm, and more preferably 50 μm to 120 μm.

[0019] The shapes and arrangement patterns of the A1 and B1 regions can be appropriately set depending on the purpose. For example, the A1 and B1 regions may each have any shape (circular, elliptical, rectangular, polygonal, etc.). Alternatively, the A1 region may be arranged so as to surround the outside of the B1 region, or the B1 region may be arranged so as to surround the outside of the A1 region.

[0020] 1B has an A1 region including a polymer matrix 10 and dispersed particles 20 that are dispersed in the polymer matrix 10 and include a liquid crystal polymer 22, which is a polymer of a polymerizable liquid crystal component, and a non-polymerizable liquid crystal component 26, and a B1 region including a polymer matrix 10 and dispersed particles 20 that are dispersed in the polymer matrix 10 and include a polymerizable liquid crystal component 24 and a non-polymerizable liquid crystal component 26. As described above, the non-polymerizable liquid crystal component is an optional component, but when the dispersed particles further include a non-polymerizable liquid crystal component, the alignment of the liquid crystal polymer and the polymerizable liquid crystal component can be more suitably controlled.

[0021] 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 polymerizable liquid crystal component or non-polymerizable liquid crystal component, the adhesion to the support substrate, and the like. 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 resin for forming the polymer matrix may be used alone or in combination.

[0022] The refractive index of the polymer matrix is, for example, 1.50 to 1.75, preferably 1.525 to 1.725, and more preferably 1.55 to 1.70.

[0023] The content of the polymer matrix in the diffusion layer in both the A1 region and the B1 region is, for example, 30% to 70% by weight, preferably 35% to 65% by weight, and more preferably 40% to 60% by weight. If the content of the polymer matrix is ​​within this range, good mechanical strength can be obtained, and effects such as prevention of liquid crystal leakage from the edges can be obtained.

[0024] As described above, the liquid crystal polymer contained in the A1 region is a polymer of a polymerizable liquid crystal component, and the polymerizable liquid crystal component constituting the liquid crystal polymer is the same liquid crystal component as the polymerizable liquid crystal component contained in the B1 region.

[0025] In the dispersed particles in the A1 region, the liquid crystal polymer is typically oriented in a predetermined direction, preferably the thickness direction of the diffusion layer and a direction parallel to the thickness direction.

[0026] As the polymerizable liquid crystal component, any polymerizable liquid crystal compound can be used alone or in combination of two or more depending on birefringence, compatibility with the non-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.

[0027] The dielectric anisotropy of the polymerizable liquid crystal component may be positive or negative. The polymerizable liquid crystal component may contain a bifunctional or higher crosslinked liquid crystal compound. As the polymerizable liquid crystal component, for example, polymerizable mesogen compounds described in 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, GB 2,280,445, etc. can be used. As the polymerizable liquid crystal component, for example, a nematic liquid crystal monomer is preferred.

[0028] 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. The dielectric anisotropy of the non-polymerizable liquid crystal component may be positive or negative. 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 high linear transmitted light intensity in the aligned state.

[0029] 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 liquid crystal compounds may be used alone or in combination.

[0030] Typically, the polymerizable liquid crystal component, the non-polymerizable liquid crystal component, and the polymer matrix are ａ <np<ne ａ Here, no ａ is the average ordinary refractive index of the polymerizable liquid crystal component and the non-polymerizable liquid crystal component, and ne ａis the average extraordinary refractive index of the polymerizable liquid crystal component and the non-polymerizable liquid crystal component, and np is the refractive index of the polymer matrix. The average ordinary refractive index and the average extraordinary refractive index are each calculated as a weighted average taking into account the blending ratio of the polymerizable liquid crystal component and the non-polymerizable liquid crystal component. When the dispersed particles do not contain a non-polymerizable liquid crystal component, no ａ corresponds to the ordinary refractive index of the polymerizable liquid crystal component, and ne ａ corresponds to the extraordinary refractive index of the polymerizable liquid crystal component. When the polymerizable liquid crystal component, the non-polymerizable liquid crystal component, and the polymer matrix satisfy the above relationship, a diffusion layer having a region where incident light from an oblique direction exhibits the maximum intensity of straight transmitted light can be suitably obtained.

[0031] In one embodiment, the polymerizable liquid crystal component, the non-polymerizable liquid crystal component, and the polymer matrix preferably have a molecular weight of 0.01≦np−n0 ａ More preferably, 0.01≦np−no ａ ≦0.25, more preferably 0.02≦np−no ａ ≦0.25 (for example, 0.03≦np−no ａ ≦0.25, 0.04≦np-no ａ ≦0.25, or 0.05≦np-no ａ In one embodiment, the polymerizable liquid crystal component, the non-polymerizable liquid crystal component, and the polymer matrix preferably satisfy the relationship 0.01≦ne ａ -np, more preferably 0.01≦ne ａ -np≦0.35, more preferably 0.02≦ne ａ -np≦0.35 (for example, 0.03≦ne ａ -np≦0.35, 0.04≦ne ａ -np≦0.35, or 0.05≦ne ａ When the polymerizable liquid crystal component, the non-polymerizable liquid crystal component, and the polymer matrix satisfy the above relationship, it is possible to sufficiently increase the difference between the intensity of the rectilinear transmitted light of incident light from an oblique direction and the intensity of the rectilinear transmitted light of incident light from the front direction.

[0032] The birefringence Δn (=ne−no) of the polymerizable liquid crystal component at a wavelength of 589 nm is preferably 0.05 to 0.35, more preferably 0.1 to 0.3.

[0033] The birefringence Δn of the non-polymerizable liquid crystal component at a wavelength of 589 nm is preferably 0.05 to 0.35, more preferably 0.1 to 0.3.

[0034] The total content of the liquid crystal polymer and the non-polymerizable liquid crystal component in the A1 region (the content of the liquid crystal polymer when the dispersed particles do not contain a non-polymerizable liquid crystal component) is, for example, 30% to 70% by weight, preferably 35% to 65% by weight, and more preferably 40% to 60% by weight. The ratio of the liquid crystal polymer content to the total content of the liquid crystal polymer and the non-polymerizable liquid crystal component in the A1 region is, for example, 5% by weight or more, preferably 7% by weight or more, and more preferably 10% by weight or more, and may be, for example, 100% by weight or less, preferably 80% by weight or less, and more preferably 50% by weight or less. The total content of the polymer matrix, liquid crystal polymer, and non-polymerizable liquid crystal component in the A1 region may be, for example, 80% by weight or more, preferably 90% to 99.9% by weight, and preferably 95% to 99.9% by weight.

[0035] The total content of the polymerizable liquid crystal component and the non-polymerizable liquid crystal component in the B1 region (the content of the polymerizable liquid crystal component when the dispersed particles do not contain a non-polymerizable liquid crystal component) is, for example, 30% to 70% by weight, preferably 35% to 65% by weight, and more preferably 40% to 60% by weight. The ratio of the polymerizable liquid crystal component to the total content of the polymerizable liquid crystal component and the non-polymerizable liquid crystal component in the B1 region is, for example, 5% by weight or more, preferably 7% by weight or more, and more preferably 10% by weight or more, and may be, for example, 100% by weight or less, preferably 80% by weight or less, and more preferably 50% by weight or less. The total content of the polymer matrix, polymerizable liquid crystal component, and non-polymerizable liquid crystal component in the B1 region may be, for example, 80% by weight or more, preferably 90% to 99.9% by weight, and preferably 95% to 99.9% by weight.

[0036] The diffusion layer may further contain any appropriate additives as necessary. Examples of such additives include a polymerization initiator, a dispersant, a leveling agent, a crosslinking agent, and a dispersion stabilizer. The total content of the additives in the diffusion layer may be, for example, 20% by weight or less, preferably 0.1 to 10% by weight, and more preferably 0.1 to 5% by weight.

[0037] The average particle diameter of the dispersed particles can be, for example, 0.2 μm to 15 μm, preferably 0.3 μm to 12 μm. If the average particle diameter of the dispersed particles is too small, the dispersed particle size is smaller than the wavelength of light, so light passes through the dispersed particles without being scattered, which can result in a problem of insufficient haze being obtained. If the average particle diameter is too large, the dispersed particle size is too large compared to the wavelength of light, which can result in a problem of insufficient haze being obtained. Note that the average particle diameter of the dispersed particles in the diffusion layer is the volume average particle diameter of the dispersed particles when viewed from a direction perpendicular to the main surface of the diffusion layer.

[0038] The thickness of the diffusion layer is, for example, 3 μm to 60 μm, preferably 5 μm to 55 μm, and more preferably 8 μm to 50 μm.

[0039] <Supporting substrate> The first supporting substrate and the second supporting substrate (hereinafter, collectively referred to as "supporting substrate") each include a substrate body. The supporting substrate may have a functional layer on one or both sides of the substrate body as necessary. Examples of the functional layer include a hard coat (HC) layer, a refractive index adjustment layer, a transparent electrode layer, etc. The first supporting substrate and the second supporting substrate may have the same configuration (material and thickness of the substrate body, presence or absence or type of functional layer, etc.) or different configurations. One or both of the first supporting substrate and the second supporting substrate may be omitted depending on the purpose, etc.

[0040] The haze of the supporting substrate is preferably 20% or less, more preferably 10% or less, and even more preferably 0.1% to 10%.

[0041] The total light transmittance of the supporting substrate is preferably 30% or more, more preferably 60% or more, and even more preferably 80% or more.

[0042] The substrate body may be formed using any suitable material. Specific examples include glass films and polymer films. Polymer films are preferred because they have excellent smoothness and can be continuously produced using rolls, greatly improving productivity.

[0043] The substrate body is typically a polymer film primarily composed of a thermoplastic resin. Examples of thermoplastic resins include polyester resins; cycloolefin resins such as polynorbornene; acrylic resins; polycarbonate resins; and cellulose resins. Among 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 thermoplastic resins may be used alone or in combination of two or more. Optical films used in polarizing plates, such as low-retardation substrates, high-retardation substrates, retardation plates, absorptive polarizing films, and polarized selective reflection films, can also be used as the substrate body.

[0044] The thickness of the substrate body is preferably 200 μm or less, more preferably 3 μm to 100 μm, and even more preferably 5 μm to 70 μm.

[0045] The hard coat layer, the refractive index adjusting layer, and the transparent electrode layer may have structures well known in the art, and therefore detailed descriptions thereof will be omitted. The transparent electrode layer can be suitably used when aligning and polymerizing the polymerizable liquid crystal component.

[0046] The thickness of the supporting substrate is preferably 200 μm or less, more preferably 3 μm to 100 μm, and even more preferably 5 μm to 70 μm.

[0047] <Method for Producing Diffusion Film> The diffusion film can be produced by any appropriate method. In one embodiment, the method for producing the diffusion film includes: (Step I) applying a coating liquid containing a solvent, a polymer matrix-forming resin, a polymerizable liquid crystal component, and an optional non-polymerizable liquid crystal component to a first substrate to obtain a coating layer; (Step II) drying the coating layer to obtain a polymer-dispersed liquid crystal (PDLC) layer containing a polymer matrix and liquid crystal droplets containing the polymerizable liquid crystal component and the non-polymerizable liquid crystal component dispersed in the polymer matrix; and (Step III) applying an active energy ray to a predetermined region of the PDLC layer while applying a voltage to the PDLC layer to polymerize the polymerizable liquid crystal component. Step III can produce a diffusion layer containing a polymer matrix and dispersed particles dispersed in the polymer matrix, the liquid crystal polymer being a polymer of the polymerizable liquid crystal component and the optional non-polymerizable liquid crystal component. The method for manufacturing the diffusion film may further include, as necessary, placing a second substrate on the side of the PDLC layer or the diffusion layer opposite the side where the first substrate is provided (step IV) before or after step III. According to the method for manufacturing the diffusion film, in the irradiated region irradiated with active energy rays, the polymerizable liquid crystal component is polymerized in a state where it is aligned in a predetermined direction, thereby producing a liquid crystal polymer with a fixed alignment state. Meanwhile, in the non-irradiated region not irradiated with active energy rays, the polymerizable liquid crystal component does not polymerize and remains in a non-aligned state when no voltage is applied. As a result, the resulting diffusion layer has an irradiated region containing a liquid crystal polymer in which dispersed particles are aligned in a predetermined direction and a non-irradiated region containing a polymerizable liquid crystal component in which dispersed particles are non-aligned, with the irradiated region being the A1 region and the non-irradiated region being the B1 region.

[0048] (Step I) In step I, a coating liquid containing a solvent, a polymer matrix-forming resin, a polymerizable liquid crystal component, and an optional non-polymerizable liquid crystal component is applied to a first substrate to obtain a coating layer.

[0049] The coating liquid is preferably an emulsion containing, as a dispersoid, liquid crystal particles containing a polymerizable liquid crystal component and, optionally, a non-polymerizable liquid crystal component (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 polymerizable liquid crystal component and, optionally, a non-polymerizable liquid crystal component 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.

[0050] As the solvent, water or a mixed solvent of water and a water-miscible organic solvent can be preferably used. Examples of the water-miscible organic solvent include C1-3 alcohol, acetone, and DMSO. The polymerizable liquid crystal component, the non-polymerizable liquid crystal component, and the resin for forming the polymer matrix are as described above. Optional additives include a dispersant, a leveling agent, and a crosslinking agent.

[0051] The content of the liquid crystal component in the solid content of the coating liquid (the total content of the polymerizable liquid crystal component and the non-polymerizable liquid crystal component, if present) may be, for example, 30% by weight to 70% by weight, preferably 35% by weight to 65% by weight, and more preferably 40% by weight to 60% by weight.

[0052] The weight ratio of the polymerizable liquid crystal component to the non-polymerizable liquid crystal component in the coating liquid (polymerizable liquid crystal component:non-polymerizable liquid crystal component) can be, for example, 5:95 to 100:0, preferably 7:93 to 80:20, and more preferably 10:90 to 50:50.

[0053] The content of the polymer matrix-forming resin in the solid content of the coating liquid may be, for example, 30 to 70% by weight, preferably 35 to 65% by weight, and more preferably 40 to 60% by weight.

[0054] The weight ratio of the content of the liquid crystal component in the coating solution (the total content of the polymerizable liquid crystal component and, if present, the non-polymerizable liquid crystal component) to the content of the polymer matrix-forming resin (liquid crystal component:polymer matrix-forming resin) can be, for example, 30:70 to 70:30, preferably 35:65 to 65:35, and more preferably 40:60 to 60:40. The total content of the polymer matrix-forming resin and the liquid crystal component in the solid content of the coating solution can be, for example, 80% by weight or more, preferably 90% by weight to 99.9% by weight, and more preferably 95% by weight to 99.9% by weight.

[0055] The average particle size of the liquid crystal particles is preferably 0.3 μm or more, more preferably 0.4 μm or more. The average particle size of the liquid crystal particles is preferably 15 μm or less, more preferably 12 μm or less. If the average particle size of the liquid crystal particles is within this range, the average particle size of the dispersed particles in the diffusion layer can be set within a desired range. The average particle size of the liquid crystal particles is a volume-average particle size.

[0056] The particle size of the liquid crystal particles preferably has a relatively narrow particle size distribution. The coefficient of variation (CV value) of the particle size of the liquid crystal particles may be, for example, less than 0.40, preferably 0.35 or less, and more preferably 0.30 or less. In one embodiment, an emulsion coating liquid may be used that is substantially free of liquid crystal particles having a particle size of less than 0.3 μm or more than 15 μm (for example, an emulsion coating liquid in which the volume ratio of liquid crystal particles having a particle size of less than 0.3 μm or more than 15 μm to the total volume of liquid crystal particles is 10% or less).

[0057] 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 400 nm, and even more preferably 50 nm to 300 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 diameter and can be measured using a dynamic light scattering particle size distribution analyzer.

[0058] As the polymerization initiator, any appropriate polymerization initiator can be used depending on the purpose, and the polymerization initiator is preferably a photopolymerization initiator. 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 polymerization initiators may be used alone or in combination of two or more. The content of the polymerization initiator is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the polymerizable liquid crystal component.

[0059] Examples of dispersants include anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc. The content of the dispersant is preferably 1 to 15 parts by weight, more preferably 2 to 10 parts by weight, per 100 parts by weight of the solid content of the coating liquid.

[0060] 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 is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, relative to 100 parts by weight of the solid content of the coating liquid.

[0061] Examples of the crosslinking agent include an aziridine-based crosslinking agent, an isocyanate-based crosslinking agent, etc. The content of the crosslinking agent is preferably 0.5 to 20 parts by weight, more preferably 1 to 10 parts by weight, relative to 100 parts by weight of the solid content of the coating liquid.

[0062] 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 containing a liquid crystal component and a polymerization initiator, and optional additives (e.g., dispersants, leveling agents, crosslinking agents). If necessary, a solvent may be added during mixing. Alternatively, the emulsion coating liquid can be prepared by adding the liquid crystal component, polymer matrix-forming resin, polymerization initiator, and optional additives to a solvent and mechanically dispersing them.

[0063] 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).

[0064] The solid content of the coating liquid may be, for example, 20% to 60% by weight, preferably 30% to 50% by weight.

[0065] The viscosity of the coating liquid can be appropriately adjusted so that coating onto the first substrate is performed smoothly. The viscosity of the coating liquid during coating 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 becomes significant when the solvent is dried, which may cause the thickness of the PDLC layer (and consequently the diffusion layer) to become unstable. Furthermore, if the viscosity exceeds 400 mPa·s, the bead of the coating liquid may become unstable. The viscosity of the coating liquid can be measured, for example, using an Anton Paar MCR302 rheometer. The viscosity used here is the shear viscosity value at 20°C and a shear rate of 1000 (1 / s).

[0066] Any appropriate substrate can be used as the first substrate. By using the first supporting substrate as the first substrate, a diffusion film having the first supporting substrate and the diffusion layer can be suitably obtained. Depending on the purpose, the first substrate may be peeled off and removed from the diffusion layer after completion of step III.

[0067] Any appropriate method can be adopted 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 of JP-A-2019-5698 can be referred to.

[0068] The thickness of the coating layer is preferably 3 μm to 100 μm, more preferably 4 μm to 80 μm, and even more preferably 5 μm to 50 μm. Within such a range, a PDLC layer (and consequently a diffusion layer) with excellent thickness uniformity can be obtained.

[0069] (Step II) In Step II, the coating layer is dried to obtain a PDLC layer containing a polymer matrix and liquid crystal droplets containing a polymerizable liquid crystal component and a non-polymerizable liquid crystal component dispersed in the polymer matrix. By removing the solvent from the coating layer through drying, a PDLC layer having a structure in which liquid crystal droplets are dispersed in a polymer matrix is ​​formed.

[0070] 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.

[0071] 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.

[0072] (Step III) In Step III, while a voltage is applied to the PDLC layer, active energy rays are irradiated to a predetermined region to polymerize the polymerizable liquid crystal component. Step III can produce a diffusion layer containing a polymer matrix and dispersed particles dispersed in the polymer matrix, the dispersed particles containing a liquid crystal polymer, which is a polymer of the polymerizable liquid crystal component, and an optional non-polymerizable liquid crystal component. The active energy rays can be irradiated, for example, through a photomask having openings of a predetermined pattern.

[0073] Examples of active energy rays that can be used include ultraviolet rays, infrared rays, X-rays, α rays, β rays, γ rays, and electron beams. Of 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.

[0074] The ultraviolet irradiation conditions can be appropriately set depending on the type of polymerizable liquid crystal component, the transmittance of the substrate, 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 / cm２ , 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.

[0075] 3(a) and (b) are schematic diagrams illustrating one embodiment of step III. In the embodiment shown in FIG. 3(a) and (b), step IV is performed before step III, and a first support substrate 120 as a first substrate is disposed on one side of the PDLC layer 110a, and a second support substrate 130 as a second substrate is disposed on the other side. Unlike the illustrated example, at least one surface of the PDLC layer may be exposed.

[0076] The PDLC layer 110a includes a polymer matrix 10 and liquid crystal droplets 20a dispersed in the polymer matrix 10, and the liquid crystal droplets 20a include a polymerizable liquid crystal component 24 and a non-polymerizable liquid crystal component 26. A first electrode 210 is disposed on the outer side of the first support substrate 120 (the side opposite to the side on which the PDLC layer is disposed), and a second electrode 220 that is transmissive to active energy rays is disposed on the outer side of the second support substrate 130 (the side opposite to the side on which the PDLC layer is disposed).

[0077] In FIG. 3A, a voltage is applied to the electrodes 210 and 220 from a power source 230, generating an electric field between them. Therefore, the polymerizable liquid crystal component 24 and the non-polymerizable liquid crystal component 26 in the liquid crystal droplet 20a are aligned in the thickness direction. Preferably, the alignment state of the polymerizable liquid crystal component 24 and the non-polymerizable liquid crystal component 26 is uniform throughout the entire PDLC layer. In this state, the PDLC layer is irradiated with active energy rays (ultraviolet rays in the illustrated example) through a photomask 240 having openings in a predetermined pattern. This polymerizes the polymerizable liquid crystal component 24 in the irradiated areas, producing a liquid crystal polymer 22.

[0078] 3(b), after irradiation with active energy rays, the dispersed particles 20 in the diffusion layer 110 contain liquid crystal polymer 22 and non-polymerizable liquid crystal component 26 oriented in the thickness direction in the irradiated region, and contain non-oriented polymerizable liquid crystal component 24 and non-polymerizable liquid crystal component 26 in the non-irradiated region. Therefore, the irradiated region can correspond to region A1 where light incident at a predetermined incident angle θ° (where θ>0) exhibits the maximum straight-transmitted light intensity, and the non-irradiated region can correspond to region B1 where light incident from the front direction exhibits the maximum straight-transmitted light intensity.

[0079] The voltage applied during polymerization is not limited as long as the polymerizable liquid crystal component exhibits the desired alignment, and can be appropriately set depending on the haze desired for the diffusion film, the distance between the electrodes, etc. For example, by using a substrate with a transparent electrode layer as the first substrate and / or the second substrate, there is no need to prepare separate electrodes, and the distance between the electrodes can be reduced to reduce the applied voltage.

[0080] 3(a) and (b) show an example in which a liquid crystal component with positive dielectric anisotropy is used, but a diffusion layer can also be produced in the same manner when a liquid crystal component with negative dielectric anisotropy is used. In this case, as shown in FIG. 4, in the A1 region (irradiated region) of the diffusion film 100B, the liquid crystal polymer 22 and non-polymerizable liquid crystal component 26 contained in the dispersed particles 20 are typically oriented in a direction perpendicular to the electric field direction (thickness direction). When a liquid crystal component with negative dielectric anisotropy is used, a diffusion layer with high haze in the A1 region can be preferably obtained.

[0081] (Step IV) In Step IV, a second substrate is placed on the side of the PDLC layer or the diffusion layer opposite to the side on which the first substrate is provided. Any appropriate substrate may be used as the second substrate, and the above-mentioned second support substrate may be preferably used. Step IV may be performed before Step III, i.e., before polymerizing the polymerizable liquid crystal component, or after Step III, i.e., after polymerizing the polymerizable liquid crystal component.

[0082] According to the method for manufacturing a diffusion film including step IV, by using a first supporting substrate and a second supporting substrate as the first substrate and the second substrate, respectively, a diffusion film having the first supporting substrate and the second supporting substrate and a diffusion layer directly sandwiched therebetween can be obtained.

[0083] In order to obtain sufficient adhesion, the second substrate is preferably laminated on the PDLC layer or the diffusion layer 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.

[0084] <<Variation 1>> Fig. 5 is a schematic cross-sectional view illustrating the configuration of another example of a diffusion film according to an embodiment of the present invention. The diffusion film 100C shown in Fig. 5 includes a diffusion layer 110, a first support substrate 120 disposed on one side of the diffusion layer 110, and a second support substrate 130 disposed on the other side. The diffusion layer 110 has an A1 region including a polymer matrix 10 and dispersed particles 20 containing a liquid crystal polymer 22 and a non-polymerizable liquid crystal component 26 that are dispersed in the polymer matrix 10 and oriented in a predetermined direction (the thickness direction in the illustrated example), and a B1 region including the polymer matrix 10 and dispersed particles 20 containing the liquid crystal polymer 22 and the non-polymerizable liquid crystal component 26 in a non-oriented state. The diffusion film 100C differs from the diffusion film 100A in that the dispersed particles 20 in the B1 region contain the liquid crystal polymer 22 in a non-oriented state. In the diffusion film 100C, the alignment states of the liquid crystal polymer 22 contained in the dispersed particles 20 are different between the A1 region and the B1 region.

[0085] The diffusion film 100C has a mechanism similar to that of the diffusion film 100A, in which in the A1 region, light incident at a predetermined incident angle θ° (where θ>0) exhibits the maximum straight-through transmitted light intensity, and in the B1 region, light incident from the front direction exhibits the maximum straight-through transmitted light intensity.

[0086] The diffusion film 100C can be produced, for example, in the above-described method for producing a diffusion film, by irradiating the non-irradiated region (region B1) with active energy rays in a state where no voltage is applied (resulting in the polymerizable liquid crystal component being in a non-oriented state) after producing region A1, thereby polymerizing the polymerizable liquid crystal component.

[0087] <<Variation 2>> The diffusion film according to an embodiment of the present invention may include a diffusion layer having only the above-mentioned region A1. Specifically, the entire region of the diffusion layer may include a polymer matrix and dispersed particles that are dispersed in the polymer matrix and include a liquid crystal polymer oriented in a predetermined direction (e.g., the thickness direction or a direction perpendicular to the thickness direction) and an optional non-polymerizable liquid crystal component. Such a diffusion film can be produced by irradiating the entire region of the PDLC layer with active energy rays while aligning the polymerizable liquid crystal component in the liquid crystal droplets in the predetermined direction, thereby polymerizing the polymerizable liquid crystal component.

[0088] B. Light Diffusion Device A light diffusion device according to an embodiment of the present invention includes the diffusion film described in Section A and a light source unit. Figure 6 is a schematic cross-sectional view showing the configuration of a light diffusion device according to one embodiment of the present invention. Light diffusion device 300 includes a light source unit 350 and a diffusion film 100 disposed thereon.

[0089] The light source unit 350 includes, for example, a reflective layer 310, a plurality of point light sources 320 provided on one side of the reflective layer 310, and a sealing unit 330 that seals the point light sources 320. The reflective layer may include, for example, a metal layer or a foamed resin layer. The plurality of point light sources are, for example, arranged two-dimensionally in a predetermined pattern. For example, LED elements may be used as the point light sources. The sealing unit 330 is made of, for example, a thermosetting resin such as silicone resin or epoxy resin.

[0090] In one embodiment, the diffusion film 100 has an A1 region formed in a pattern corresponding to the arrangement pattern of the point light source and a B1 region formed surrounding the A1 region. The diffusion film 100 can be stacked on the light source unit 350 so that the A1 region is positioned above the point light source. With this configuration, the high-haze region (A1 region) located directly above the A1 region can highly diffuse light emitted from the point light source in an oblique direction, while the B1 region surrounding the A1 region can transmit light reflected from the reflective layer upward. Since the B1 region is not directly above the LED, it tends to be dark, so a low haze is required. Therefore, rather than controlling the light distribution, it is possible to achieve low haze in the B1 region and brighten the brightness of the B1 region by designing the average refractive index of the liquid crystal component when unoriented to be equal to the refractive index of the polymer matrix-forming resin. A light diffusion device having the above configuration can achieve excellent in-plane brightness uniformity and high light utilization efficiency.

[0091] 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.

[0092] <Thickness> Measured using a digital micrometer (manufactured by Anritsu Corporation, product name "KC-351C"). <Volume average particle diameter of liquid crystal particles in liquid crystal emulsion> The volume average particle diameter was calculated using a particle size distribution analyzer (manufactured by Microtrac, "MT3300EXII"). <Haze> Measured using a haze meter (manufactured by Nippon Denshoku Industries, product name "NDH4000") in accordance with JIS K 7136. <Refractive index of polymer matrix> Measured using a prism coupler (manufactured by Melitcon, product name "2010 / M"). Specifically, the following was performed. 3 g of an aqueous dispersion of a polymer matrix-forming resin was dropped onto a PET film and dried at room temperature for 3 days to obtain a 1.5 mm thick resin film. This resin film was peeled from the PET film, and the peeled surface was adhered to a prism. 594 nm laser light was irradiated from the prism surface opposite the resin film at 25°C. The refractive index of the polymer matrix was measured by measuring the reflected light intensity when the incident angle of the laser light was changed. <Refractive index of the liquid crystal component> Measurement was performed using an Abbe refractometer (manufactured by Atago Co., Ltd., product name "NAR-4T"). Specifically, the procedure is as follows. Liquid crystal heated to an isotropic state was dropped onto the prism surface that had been subjected to an alignment treatment, and the liquid crystal was cooled to room temperature (25°C). With the liquid crystal aligned perpendicular to the prism surface, the angle of the polarizing plate placed above the eyepiece of the refractometer was changed to measure no and ne. The sodium D line (589.3 nm) was used as the measurement wavelength.

[0093] Example 1 Preparation of emulsion coating liquid 52.8 parts of a non-polymerizable liquid crystal component (manufactured by JNC Corporation, product name "JC-5240XX", positive liquid crystal, birefringence Δn=0.252 (ne=1.766, no=1.514), viscosity=75 mPa·s), 52.8 parts of a polymerizable liquid crystal component (manufactured by BASF Corporation, product name "PALIOCOLOR" LC-242" (birefringence Δn=0.131 (ne=1.654, no=1.523)), 5.9 parts of a photopolymerization initiator (manufactured by IGM, product name "OMNIRAD651"), 0.1 parts of pure water, 40.0 parts of pure water, and 1.2 parts of a dispersant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., product name "Noigen ET159") were mixed and stirred with a homogenizer at 100 rpm for 10 minutes to obtain a crude dispersion. The crude dispersion was passed through a separation membrane (manufactured by SPG Techno Co., Ltd., product name "SPG Pumping Connector", pore size 10 μm) with a uniform particle size distribution at room temperature from the outside to the inside of the membrane at a flow rate of 80 mL / min / cm. ２ This operation was repeated five times. The volume average particle diameter of the liquid crystal particles in the liquid crystal emulsion obtained was 3.0 μm. An emulsion coating liquid was obtained by mixing 30.8 parts of the above liquid crystal emulsion, 61.1 parts of an aqueous dispersion (solid content 29.0%) of acrylic-styrene copolymer resin (refractive index 1.56), 0.2 parts of a leveling agent (manufactured by DIC Corporation, product name "F-444"), 1.3 parts of a crosslinking agent (tris[3-(2-methylaziridin-1-yl)propionic acid]=propylidinetrimethyl), and 5.2 parts of pure water. Note that the no of the polymerizable liquid crystal component and the non-polymerizable liquid crystal component ａ is 1.515, and ne ａ was 1.755.

[0094] <Preparation of Supporting Substrate> An ITO layer was formed by sputtering on one surface of a PET substrate (thickness: 50 μm) to prepare a supporting substrate having a structure of [substrate body / transparent electrode layer (surface resistance: 100 Ω)], which was used as a first supporting substrate and a second supporting substrate.

[0095] <Production of PDLC Film> The emulsion coating liquid was applied to the transparent electrode layer side surface of the first supporting substrate using a wire bar to form a 30 μm thick coating layer. The coating layer was then dried at 25°C for 60 minutes to form an 8 μm thick PDLC layer. The resulting PDLC layer exhibited a uniform haze (haze (front direction): 90%) across the entire main surface. Next, a second supporting substrate was laminated onto the PDLC layer using a laminator while applying a lamination pressure of 0.4 MPa / m, thereby obtaining PDLC film 1. The second supporting substrate was laminated so that the transparent electrode layer side surface faced the PDLC layer.

[0096] <Preparation of Diffusion Film> While applying a voltage of 100 V between the transparent electrode layers of the PDCL film 1, UV irradiation was performed from the second supporting substrate side through a photomask having a predetermined pattern. Specifically, UV irradiation was performed using a UV-LED lamp (manufactured by Hamamatsu Photonics, product name "C11924-101", peak wavelength 365 nm) at 20 mW / cm. ２ The film was then exposed to light at 25°C for 3 minutes. This polymerized the polymerizable liquid crystal component in the irradiated area, resulting in a diffusion film 1 having a structure of [first supporting substrate / patterned diffusion layer / second supporting substrate]. In the resulting diffusion film 1, the haze (front direction) of the irradiated area (area A1) was 38%.

[0097] Example 2 Preparation of emulsion coating liquid 52.8 parts of a non-polymerizable liquid crystal component (negative liquid crystal, birefringence Δn=0.149 (ne=1.633, no=1.484)), 5.9 parts of a polymerizable liquid crystal component (manufactured by BASF, product name "PALIOCOLOR LC-242", birefringence Δn=0.131 (ne=1.654, no=1.523)), 0.1 parts of a photopolymerization initiator (manufactured by IGM, product name "OMNIRAD651"), 40.0 parts of pure water, and 1.2 parts of a dispersant (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name "NOIGEN ET159") were mixed and stirred with a homogenizer at 100 rpm for 10 minutes to obtain a crude dispersion. The crude dispersion was passed through a separation membrane with a uniform particle size distribution (manufactured by SPG Techno Co., Ltd., product name "SPG Pumping Connector", pore size 10 μm) at room temperature from the outside to the inside of the membrane at a flow rate of 80 mL / min / cm. ２This operation was carried out five times. The volume average particle diameter of the liquid crystal particles in the obtained liquid crystal emulsion was 3.0 μm. An emulsion coating liquid was obtained by mixing 30.8 parts of the above liquid crystal emulsion, 61.1 parts of an aqueous dispersion (solid content 29.0%) of acrylic-styrene copolymer resin (refractive index 1.56), 0.2 parts of a leveling agent (manufactured by DIC Corporation, product name "F-444"), 1.3 parts of a crosslinking agent (tris[3-(2-methylaziridin-1-yl)propionic acid]=propylidinetrimethyl), and 5.2 parts of pure water. Note that the no of the polymerizable liquid crystal component and the non-polymerizable liquid crystal component ａ is 1.488, and ne ａ was 1.635.

[0098] PDLC film 2 was produced in the same manner as in Example 1, except that the above emulsion coating liquid was used, and then diffusion film 2 was produced. In PDLC film 2, the PDLC layer exhibited a uniform haze (haze (front direction): 77%) across the entire main surface. In diffusion film 2, the haze (front direction) of the irradiated area (area A1) was 82%.

[0099] Comparative Example 1 Preparation of emulsion coating liquid 52.8 parts of a non-polymerizable liquid crystal component (birefringence Δn=0.367 (ne=1.882, no=1.514)), 52.8 parts of a polymerizable liquid crystal component (manufactured by BASF, product name "PALIOCOLOR" LC-242" (birefringence Δn=0.131 (ne=1.654, no=1.523)), 5.9 parts of a photopolymerization initiator (manufactured by IGM, product name "OMNIRAD651"), 0.1 parts of pure water, 40.0 parts of pure water, and 1.2 parts of a dispersant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., product name "Noigen ET159") were mixed and stirred with a homogenizer at 100 rpm for 10 minutes to obtain a crude dispersion. The crude dispersion was passed through a separation membrane (manufactured by SPG Techno Co., Ltd., product name "SPG Pumping Connector", pore size 10 μm) with a uniform particle size distribution at room temperature from the outside to the inside of the membrane at a flow rate of 80 mL / min / cm. ２The liquid crystal particles in the obtained liquid crystal emulsion had a volume average particle size of 3.0 μm. An emulsion coating liquid was obtained by mixing 30.8 parts of the above liquid crystal emulsion, 44.3 parts of an aqueous dispersion of polyether-based polyurethane resin (manufactured by DSM, product name "NeoRez R967", refractive index 1.49, polymer average particle size: 80 nm, solid content: 40 wt%), 0.2 parts of a leveling agent (manufactured by DIC, product name "F-444"), 1.3 parts of a crosslinking agent (tris[3-(2-methylaziridin-1-yl)propionic acid]=propylidinetrimethyl), and 22.0 parts of pure water. Note that the no of the polymerizable liquid crystal component and the non-polymerizable liquid crystal component ａ is 1.515, and ne ａ was 1.859.

[0100] A PDLC film C1 was produced in the same manner as in Example 1, except that the above emulsion coating liquid was used, and then a diffusion film C1 was produced. In the PDLC film C1, the PDLC layer exhibited a uniform haze (haze (front direction): 80%) across the entire main surface. In the diffusion film C1, the haze (front direction) of the irradiated area (area A1) was 9%.

[0101] <Light Distribution Measurement> Light distribution measurements were performed on the diffusion films obtained in the Examples and Comparative Examples using a goniophotometer (manufactured by Nikka Densoku Co., Ltd., product name "GP-4"). Specifically, light distribution was evaluated by measuring the intensity of straight transmitted light in the illuminated area (area A1) and non-illuminated area (area B1) of the diffusion film while varying the angle of incidence in 5° increments. The results are shown in Figure 7. In the figure, the vertical axis represents the ratio of each straight transmitted light intensity to the maximum straight transmitted light intensity.

[0102] 7, the diffusion film of Example 1 exhibited maximum straight-transmitted light intensity at an incident angle of approximately 30° in region A1, and maximum straight-transmitted light intensity at an incident angle of 0° in region B1. The diffusion film of Example 2 exhibited maximum straight-transmitted light intensity at an incident angle of approximately 60° in region A1, and maximum straight-transmitted light intensity at an incident angle of 0° in region B1. On the other hand, the diffusion film of Comparative Example 1 exhibited maximum straight-transmitted light intensity at an incident angle of 0° in both regions A1 and B1.

[0103] The diffusion film of the present invention is suitably used in light diffusion devices and the like.

[0104] REFERENCE SIGNS LIST 10 polymer matrix 20 dispersed particles 22 liquid crystal polymer 24 polymerizable liquid crystal component 26 non-polymerizable liquid crystal component 100A-C diffusion film 110 diffusion layer 120 first supporting substrate 130 second supporting substrate 300 light diffusion device

Claims

1. A diffusion film comprising a diffusion layer including a polymer matrix and dispersed particles dispersed in the polymer matrix, the dispersed particles including a liquid crystal polymer, which is a polymer of a polymerizable liquid crystal component, and an optional non-polymerizable liquid crystal component, wherein the diffusion layer has an A1 region that exhibits a maximum straight-transmitted light intensity at an incident angle of θ° (where θ>0), and a B1 region that exhibits a maximum straight-transmitted light intensity at an incident angle of 0°, and the orientation state and / or content ratio of the liquid crystal polymer contained in the dispersed particles are different in the A1 region and the B1 region.

2. The diffusion film according to claim 1, wherein the A1 region contains the liquid crystal polymer in which the dispersed particles are oriented in a predetermined direction.

3. The diffusion film according to claim 2, wherein the predetermined direction is a thickness direction or a direction perpendicular to the thickness direction.

4. The average ordinary refractive index of the polymerizable liquid crystal component and the non-polymerizable liquid crystal component is no ａ , the average extraordinary refractive index is n e ａ When the refractive index of the polymer matrix is ​​np, no ａ <np<ne ａ The diffusion film according to claim 1 , which satisfies the following relationship:

5. 0.01≦np-no ａ and / or 0.01≦ne ａ The diffusion film according to claim 4, which satisfies the relationship -np.

6. The diffusion film according to claim 1, wherein the content of said liquid crystal polymer in said A1 region is 5% by weight or more relative to the total content of said liquid crystal polymer and said non-polymerizable liquid crystal component.

7. A diffusion layer including a polymer matrix and dispersed particles that are dispersed in the polymer matrix and include a liquid crystal polymer that is a polymer of a polymerizable liquid crystal component and a non-polymerizable liquid crystal component as an optional component, and the average ordinary refractive index of the polymerizable liquid crystal component and the non-polymerizable liquid crystal component is no ａ , the average extraordinary refractive index is n e ａ When the refractive index of the polymer matrix is ​​np, no ａ <np<ne ａ Meet the relationship of the diffusion film.

8. The diffusion film according to claim 7, wherein said diffusion layer has a region containing said liquid crystal polymer in which said dispersed particles are oriented in a predetermined direction and said non-polymerizable liquid crystal component as an optional component.

9. The diffusion film according to claim 8, wherein the predetermined direction is a thickness direction or a direction perpendicular to the thickness direction.

10. The diffusion film of claim 1 or 7, further comprising a supporting substrate disposed on one or both sides of the diffusion layer.

11. A light diffusion device comprising a light source unit and the diffusion film according to claim 1 or 7.

12. The light diffusing device according to claim 11, wherein the light source section includes a plurality of point light sources.

Images