WO2020203643A1 - Light diffusion film laminate for reflective display device, and reflective display device using same - Google Patents

Abstract

[Problem] To provide a light diffusion film laminate for a reflective display device having excellent display quality, the light diffusion film laminate being capable of improving the intensity of reflected light at various outside light incidence angles in the viewing-side front direction to thereby improve visibility. [Solution] This light diffusion film laminate for a reflective display device has diffuseness that changes according to a light incidence angle. The light diffusion film laminate is characterized by comprising at least an anisotropic light diffusion layer which has linear transmittance that changes according to the light incidence angle, and an isotropic light diffusion layer provided on one surface side of the anisotropic light diffusion layer, wherein the anisotropic light diffusion layer has therein a matrix region and a columnar region composed of a plurality of columnar structures, the scattering central axis angle of the anisotropic light diffusion layer is less than 6° with respect to the normal direction of the anisotropic light diffusion layer, the maximum linear transmittance of the anisotropic light diffusion layer is 15-85% inclusive, the maximum linear transmittance of the isotropic light diffusion layer is 35% or less, and the maximum linear transmittance of the light diffusion film laminate for a reflective display device is 10% or less.

Description

Light diffusing film laminate for reflective display device and reflective display device using this

The present invention relates to a light diffusing film laminate for a reflective display device, which is a display method for displaying an image by reflecting external light, and a reflective display device using the same.

In the conventional reflective display device, it is common to provide an isotropic light diffusion layer on the display screen for the purpose of reducing the metallic luster of the reflective layer that reflects external light. Further, there is a case in which an anisotropic light diffusing layer is used to diffuse (condense) the reflected light from the reflecting layer that reflects external light in a limited direction preferentially to obtain sufficient brightness (Patent Documents). 1).
Further, Patent Documents 2 and 3 each use an optical film in which a specific anisotropic diffusion layer and an isotropic diffusion layer are laminated, and an observer (viewer) can see the visibility according to the observation position and the observation angle. The invention that suppresses the change of is disclosed.

Japanese Unexamined Patent Publication No. 2014-142502 International Publication No. 2018/05/1639 International Publication No. 2018/051700

In many reflective display devices, the positional relationship between the external light and the display device often changes under the usage environment, and the angle of incidence of the external light on the display device is not constant. Specifically, in addition to when visually recognizing a display device in a moving vehicle or when visually recognizing a display device installed outdoors for a long time, a device such as a smartphone or tablet that is used by rotating the device vertically and horizontally. Can be mentioned. On the other hand, the angle at which the display device is visually recognized is generally the front direction of the display device.

First, consider the case where an isotropic light diffusion layer is provided. When the incident angle of external light is large (when light is incident from an angle), it is necessary to widen the diffusion range in order to increase the intensity of reflected light in the front direction, which is the viewing direction (for example, fine particles). If it is the isotropic light diffusion layer used, a method of adding a large amount of fine particles can be mentioned). On the other hand, when the incident angle of external light is small (when incident from an angle close to the front direction), if the diffusion range is wide, the reflected light intensity in the front direction becomes small, so it is necessary to narrow the diffusion range. There is (for example, in the case of an isotropic light diffusion layer using fine particles, a method of adding a small amount of fine particles can be mentioned). In this way, the isotropic light diffusion layer has a trade-off relationship in which the optimum scattering characteristics differ depending on the incident angle of external light.

Next, consider the case where an anisotropic light diffusion layer as described in Patent Document 1 is provided. First, in the case of a pillar structure, since it has the property of concentrating light in the direction in which the pillar extends, the pillar extends to an angle close to the normal direction of the layer plane when considering the condensing in the front direction, which is the viewing direction. It is preferable to be present. From this, considering the case where the extending direction of the pillar is close to the normal direction of the layer plane, the incident angle of the external light is the extending direction of the pillar (in the main plane of the anisotropic light diffusing layer, from one surface to the other. When it is smaller than the surface (direction in which the pillars are oriented) (when it is incident from an angle close to the normal direction of the layer plane), the reflected light intensity in the pillar extending direction is significantly increased due to the above-mentioned condensing action. improves. On the other hand, when the incident angle of the external light is larger than the extending direction of the pillars (when the incident light is incident from an angle away from the normal direction of the layer plane), the scattering characteristics are weak, so that the front direction The light condensing effect on the light is not sufficiently exerted, and the reflected light intensity becomes small.

Subsequently, in the case of the louver structure, since the light has a characteristic of diffusing and condensing the light in the direction orthogonal to the major axis of the louver cross section, the light is incident from a specific direction in the condensing in the front direction, which is the viewing direction. Only when the reflected light intensity is greatly improved. However, due to the above characteristics, the brightness is in the direction in which the louver extends (in the main plane of the anisotropic light diffusing layer, the direction in which the louver is oriented from one surface to the other surface, also referred to as the height direction in the present invention). Light interference is likely to occur due to sudden changes in. Also, as with the pillar structure, it has a characteristic that the scattering characteristics are weak against external light that forms an angle with the extending direction of the louver, so the light collecting effect in the front direction is not sufficiently exhibited, and this is also the case. The reflected light intensity becomes small. Therefore, it is difficult for the anisotropic light diffusing layer to sufficiently collect the external light forming an angle with the extending direction of the internal structure.

As described above, both the isotropic light diffusion layer and the anisotropic light diffusion layer had an external light incident angle at which the reflected light intensity became small.

Patent Documents 2 and 3 have the effect of widening the range of incident angles of external light in which the intensity of reflected light does not change, and make it possible to suppress changes in visibility depending on the observation position and observation angle. However, in Patent Documents 2 and 3, the relative reflection brightness for each observation angle with the front direction as 100% is only changed so as to be small in the vicinity of the front direction, and the reflection brightness for each observation angle itself. No effect has been shown to improve.
Further, Patent Documents 2 and 3 make it possible to suppress a change in visibility when the observation position is changed, but are not inventions in consideration of a change in the incident angle of external light.

The present invention has been made in view of the above circumstances, and an object of the present invention is a display capable of improving the reflected light intensity at various external light incident angles in the front direction on the viewing side and improving the visibility. An object of the present invention is to provide a light diffusing film laminate for a reflective display device having excellent quality.

In order to solve the above problems, the light diffusing film laminate for a reflective display device of the present invention is a light diffusing film laminated body for a reflective display device whose diffusivity changes depending on the incident angle of light, and the light diffusing The film laminate includes at least an anisotropic light diffusing layer whose linear transmittance changes depending on the incident angle of the light and an isotropic light diffusing layer provided on one surface side of the anisotropic light diffusing layer, and the anisotropic light diffusing body. The layer has a matrix region and a columnar region composed of a plurality of columnar structures inside the layer, and the scattering center axis angle of the anisotropic light diffusion layer is 6 with respect to the normal direction of the anisotropic light diffusion layer. The maximum linear transmittance of the anisotropic light diffusing layer is 15% or more and 85% or less, and the maximum linear transmittance of the isotropic light diffusing layer is 35% or less, for the reflective display device. The maximum linear transmittance of the light diffusing film laminate is 10% or less.

According to the present invention, in the light diffusion film laminate of the anisotropic light diffusion layer and the isotropic diffusion layer, the scattering central axis angle of the anisotropic light diffusion layer and the maximum linear transmittance of each layer are defined. It is possible to provide a light diffusing film laminate for a reflective display device having excellent display quality, which can improve the reflected light intensity at various external light incident angles in the front direction on the viewing side and improve the visibility. ..

It is a schematic diagram which shows the structure of the anisotropic optical film (anisotropic light diffusion layer) which has the columnar region of the pillar structure and the louver structure according to this embodiment, and an example of the state of transmitted light incident on these anisotropic optical films. is there. It is explanatory drawing which shows the evaluation method of the light diffusivity of the anisotropic optical film by this Embodiment. It is a graph which shows the relationship between the incident light angle to the anisotropic optical film (anisotropic light diffusion layer) of the pillar structure and the louver structure shown in FIG. 1 by this embodiment, and the linear transmittance. It is a graph for demonstrating the diffusion region and non-diffusion region by this embodiment. It is a schematic diagram which shows the structural example of the anisotropic light diffusion layer which has a pillar structure and a louver structure in the anisotropic optical film by this embodiment, (a) is a louver structure, and (b) is a pillar structure. It is a three-dimensional polar coordinate display for explaining the scattering center axis in the anisotropic light diffusion layer by this embodiment. It is explanatory drawing which shows the arrangement structure of the anisotropic optical film and the isotropic light diffusion layer by this embodiment. It is a figure which shows the measuring method of the diffuse reflection light intensity of the light diffusion film laminate or the anisotropic optical film obtained in an Example and a comparative example.

<<< 0. Definition of main terms >>>
Here, the main terms of the anisotropic optical film (anisotropic light diffusion layer) will be defined.
The "anisotropic optical film" is a case where the anisotropic light diffusing layer is a single layer (only one layer) or a case where two or more anisotropic light diffusing layers are laminated (at that time, the anisotropic light diffusing layer is an adhesive layer. Etc.) and the like are included. Therefore, for example, when the anisotropic light diffusing layer is a single layer, it means that the monolayer anisotropic light diffusing layer is an anisotropic optical film.

The "anisotropic optical film" has anisotropy and directivity in which the diffusion, transmission and diffusion distribution of light have an incident light angle dependence that changes depending on the incident angle of light (details will be described later). .. Therefore, it is different from a directional diffusion film, an isotropic diffusion film, and a diffusion film oriented in a specific direction, which are not dependent on the incident light angle.

The "low refractive index region" and the "high refractive index region" are regions formed by the local difference in the refractive index of the material constituting the anisotropic optical film according to the present invention, as compared with the other. It is a relative indicator of whether the refractive index is low or high. These regions are formed when the material forming the anisotropic optical film is cured.

The "scattering center axis" is a direction in which the light diffusivity matches the incident light angle of light having substantially symmetry with the incident light angle as a boundary when the incident light angle on the anisotropic optical film is changed. means. "Having substantially symmetry" means that the optical profile (described later) regarding light diffusivity is strict when the scattering center axis has an inclination with respect to the normal direction of the film (the film thickness direction). This is because it does not have symmetry. The scattering center axis observes the inclination of the columnar structure in the cross section of the anisotropic optical film with an optical microscope, and observes the projected shape of light through the anisotropic optical film by changing the incident light angle. It can be confirmed by.

Further, the "straight line transmittance" generally refers to the linear transmittance of light incident on a film, and is generally referred to as "linear transmitted light amount" which is the amount of transmitted light in the linear direction when incident from a certain incident light angle. It is a ratio with the "incident light amount" which is the light amount of the light, and is expressed by the following formula.
Linear transmittance (%) = (Linear transmitted light amount / Incident light amount) × 100

Further, in the present invention, both "scattering" and "diffusion" are used without distinction, and both have the same meaning. Further, the meanings of "photopolymerization" and "photocuring" are that the photopolymerizable compound undergoes a polymerization reaction by light, and both are used as synonyms.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in this specification and drawing, the constituent elements having the same reference numerals shall have substantially the same structure or function.

<<< 1. Structure and characteristics of anisotropic optical film >>>
As a premise for explaining the anisotropic optical film according to the present embodiment with reference to FIGS. 1 to 4, a single-layer anisotropic optical film according to the prior art (“anisotropic light diffusion layer” referred to in the present embodiment”. The structure and characteristics of the anisotropic optical film) when only one layer is used will be described.

FIG. 1 shows an example of the structure of a single-layer anisotropic optical film (anisotropic light diffusion layer) having columnar regions of a pillar structure and a louver structure, and the state of transmitted light incident on these anisotropic optical films. It is a schematic diagram. FIG. 2 is an explanatory diagram showing a method for evaluating the light diffusivity of the anisotropic optical film. FIG. 3 is a graph showing the relationship between the incident light angle of the pillar structure and the louver structure shown in FIG. 1 on the anisotropic optical film and the linear transmittance. FIG. 4 is a graph for explaining a diffusion region and a non-diffusion region.

<< 1-1. Basic structure of anisotropic optical film >>
An anisotropic optical film is a film in which a region having a refractive index different from that of the matrix region of the film is formed inside the film. The shape of the regions having different refractive indexes is not particularly limited, but for example, as shown in FIG. 1A, the anisotropy in which the columnar structures 13 having different refractive indexes are formed in the matrix region 11. As shown in FIG. 1 (b), there are an optical film 10 and an anisotropic optical film 20 in which a columnar structure 23 having a different refractive index is formed in a matrix region 21.
Here, the columnar structure 13 has a cross section whose normal direction is the extending direction (the direction in which the columnar structure 13 is oriented from one surface to the other surface in the anisotropic optical film main plane). , Circular, or a columnar (for example, rod-shaped) having a small aspect ratio (major axis / minor axis) between the minor axis and the major axis, and such a structure is referred to as a pillar structure. Further, the columnar structure 23 is in the extending direction (in the main plane of the anisotropic optical film, the direction in which the columnar structure 23 is oriented from one surface to the other surface, also referred to as the height direction in the present invention). It is a columnar structure (for example, substantially plate-like) having a large aspect ratio in the cross section with the normal direction, and such a structure is called a louver structure.

<< 1-2. Characteristics of anisotropic optical film >>
The anisotropic optical film having the above-mentioned structure is a light diffusing film having different light diffusivity depending on the incident light angle on the film, that is, a light diffusing film having an incident light angle dependence. The light incident on the anisotropic optical film at a predetermined incident light angle is the orientation direction of the plurality of columnar structures (for example, the extending direction of the plurality of columnar structures 13 in the pillar structure and the plurality of columnar structures in the louver structure). When it is substantially parallel to the height direction of the body 23), it shows high diffusivity, and when it is not parallel to the direction, it has low diffusivity.

Here, the light diffusivity of the anisotropic optical film will be described more specifically with reference to FIGS. 2 and 3. Here, the light diffusivity of the above-mentioned anisotropic optical film 10 having a pillar structure and the anisotropic optical film 20 having a louver structure will be described as examples.

The method for evaluating the light diffusivity is as follows. First, as shown in FIG. 2, the anisotropic optical films 10 and 20 are arranged between the light source 1 and the detector 2. In the present embodiment, the case where the irradiation light I from the light source 1 is incident from the normal direction of the anisotropic optical films 10 and 20 is defined as the incident light angle of 0 °. Further, the anisotropic optical films 10 and 20 are arranged so as to be arbitrarily rotated around the straight line V, and the light source 1 and the detector 2 are fixed.
That is, according to this method, the sample (anisotropic optical films 10 and 20) is arranged between the light source 1 and the detector 2, and the sample travels straight while changing the angle with the straight line V on the sample surface as the central axis. The amount of linearly transmitted light that is transmitted and enters the detector 2 can be measured.

The light diffusivity was evaluated for the anisotropic optical films 10 and 20 when the TD direction of FIG. 1 was selected as the straight line V at the center of rotation shown in FIG. 2, and the obtained evaluation results of the light diffusivity were evaluated. It is shown in FIG. FIG. 3 shows the incident light angle dependence of the light diffusivity (light scattering property) of the anisotropic optical films 10 and 20 shown in FIG. 1 measured by the method shown in FIG. The vertical axis of FIG. 3 shows the linear transmittance which is an index showing the degree of scattering, and the horizontal axis shows the angle of incident light on the anisotropic optical films 10 and 20. More specifically, in the equation of linear transmittance (%) = (linear transmitted light amount / incident light amount) × 100, the detected light amount of the detector 2 when there are anisotropic optical films 10 and 20 = "straight line transmission". The amount of light "and also. The amount of detected light of the detector 2 in the absence of the anisotropic optical films 10 and 20 = "incident light amount". The solid line in FIG. 3 shows the light diffusivity of the anisotropic optical film 10 having a pillar structure, and the broken line shows the light diffusivity of the anisotropic optical film 20 having a louver structure. The positive and negative of the incident light angle indicate that the directions in which the anisotropic optical films 10 and 20 are rotated are opposite.

As shown in FIG. 3, the anisotropic optical films 10 and 20 have a light diffusive incident light angle dependence in which the linear transmittance changes depending on the incident light angle. Here, the curve showing the light diffusivity depending on the incident light angle as shown in FIG. 3 is hereinafter referred to as an “optical profile”. The optical profile does not directly express the light diffusivity, but if it is interpreted that the diffusive transmittance increases (increases) due to the decrease in the linear transmittance, it is generally the light diffusivity. It can be said that it shows. Specifically, in the anisotropic optical films 10 and 20, compared with the linear transmittance when the plurality of columnar structures 13 and 23 are incident in the central axis direction (extending direction), that is, in the scattering central axis direction. , The linear transmittance once becomes the minimum value at the incident light angle of -20 ° to + 20 °, and the linear transmittance increases as the incident light angle (absolute value) increases, -60 ° to -30 ° or A valley-shaped optical profile with maximum linear transmittance at an incident light angle of + 30 ° to + 60 ° is shown. In this way, in the anisotropic optical films 10 and 20, the incident light is strongly diffused in the incident light angle range of -20 ° to + 20 ° near the scattering center axis direction, but the absolute value of the incident light angle is higher than that. In the large incident light angle range, the diffusion is weakened and the linear transmittance is increased.

Here, as shown in FIG. 3, in the property that the diffusivity increases with respect to the light (display light or external light) incident in a predetermined angle range and the linear transmittance shows the minimum value, that is, in the predetermined angle range. , It has the property of increasing the diffusivity of light, and further, as shown in FIG. 3, the diffusivity decreases with respect to the light (display light or external light) incident at an angle other than the predetermined angle range. The property that the linear transmittance shows the maximum value, that is, the property that the light diffusion is reduced except in a predetermined angle range is referred to as "anisometric". That is, it means that the diffusivity of light changes depending on the angle of incident light. As described above, the predetermined angle range in which the light diffusion increases is compared with the linear transmission rate when the light is incident in the direction of the scattering center axis (the incident light angle in this direction is 0 °). For example, it refers to a range of incident light angles of −20 ° to + 20 °. Further, other than the predetermined angle range in which the diffusion of light is reduced, as described above, it is compared with the linear transmittance in the case of incident in the direction of the scattering center axis (the incident light angle in this direction is 0 °). Then, for example, it refers to a range of incident light angles of −60 ° to −30 ° or + 30 ° to + 60 °.

Further, the property that the diffusion distribution of light differs depending on the diffusion angle is called "directivity". In the case of the present invention, the diffusion distribution of light not only differs depending on the diffusion angle but also changes depending on the incident light angle. It shows a diffusion distribution with further dependence. That is, the diffusion, transmission, and diffusion distribution of light have anisotropy and directivity having an incident light angle dependence that changes depending on the incident angle of light.

Further, hereinafter, the angular range of the two incident light angles with respect to the linear transmittance of the intermediate value between the maximum linear transmittance and the minimum linear transmittance is referred to as a diffusion region (the width of this diffusion region is referred to as "diffusion width"). The other incident light angle range is referred to as a non-diffuse region.

Here, the diffusion region and the non-diffusion region will be described by taking the anisotropic optical film 20 having a louver structure as an example with reference to FIG. FIG. 4 shows the optical profile of the anisotropic optical film 20 having the louver structure of FIG. As shown in FIG. 4, an intermediate value between the maximum linear transmittance (in the example of FIG. 4, the linear transmittance is about 77%) and the minimum linear transmittance (in the example of FIG. 4, the linear transmittance is about 7%). Between two incident light angles with respect to the linear transmittance (in the example of FIG. 4, the linear transmittance is about 42%) (inside the two incident light angles at the positions of the two black spots on the optical profile shown in FIG. 4). The incident light angle range is the diffused region, and the other incident light angle range (outside the two incident light angles at the positions of the two black spots on the optical profile shown in FIG. 4) is the non-diffuse region.

In the anisotropic optical film 10 having a pillar structure, as can be seen from the state of the transmitted light in FIG. 1A, the transmitted light has a substantially circular shape, and the light is substantially the same in the MD direction and the TD direction. It shows diffusivity. That is, in the anisotropic optical film 10 having a pillar structure, the diffusion is isotropic when viewed azimuthally. Further, as shown by the solid line in FIG. 3, even if the incident light angle is changed, the light diffusivity (particularly, the optical profile near the boundary between the non-diffusing region and the diffusing region) changes relatively slowly, so that the brightness is increased. It has the effect of not causing discomfort due to sudden changes. However, the anisotropic optical film 10 is characterized in that the linear transmittance in the non-diffuse region is low, as can be understood by comparing with the optical profile of the anisotropic optical film 20 having a louver structure shown by the broken line in FIG. There is. Further, the anisotropic optical film 10 having a pillar structure is characterized in that the width of the diffusion region is narrower than that of the anisotropic optical film 20 having a louver structure. It should be noted that the pillar structure does not have the directivity of diffusion depending on the azimuth angle, but has the characteristic of having directivity with respect to the distribution of diffusion.

On the other hand, in the anisotropic optical film 20 having a louver structure, as can be seen from the state of the transmitted light in FIG. 1 (b), the transmitted light has a substantially needle shape, and the transmitted light is emitted in the MD direction and the TD direction. Diffusivity is very different. That is, in the anisotropic optical film 20 having a louver structure, the diffusion has directivity in which the diffusion characteristics differ greatly depending on the azimuth angle. Specifically, in the example shown in FIG. 1B, the diffusion is wider in the MD direction than in the case of the pillar structure, but is narrower in the TD direction than in the case of the pillar structure. Further, as shown by the broken line in FIG. 3, when the incident light angle is changed, the light diffusivity (in particular, the optical profile near the boundary between the non-diffusing region and the diffusing region) becomes (in the case of the present embodiment, in the TD direction). Since the change is extremely steep, when the anisotropic optical film 20 is applied to the display device, it appears as a sudden change in brightness, which may cause a sense of discomfort. In addition, the anisotropic optical film having a louver structure tends to cause light interference (rainbow). However, the anisotropic optical film 20 has an effect that the linear transmittance in the non-diffusion region is high and the display characteristics can be improved. In particular, by matching the preferred diffusion direction (MD direction in FIG. 1B) with the direction in which the viewing angle is desired to be widened, it is possible to widen the viewing angle in a specific intended direction.

<<< 2. Composition of anisotropic optical film >>>
The configurations of the anisotropic optical films 100 and 150 according to the present embodiment will be described with reference to FIG.

<< 2-1. Overall configuration >>
As shown in FIG. 5, the anisotropic optical films 100 and 150 are anisotropic optical films having an anisotropic light diffusing layer 110 or 120 whose linear transmittance changes depending on the incident light angle.

The anisotropic light diffusing layer 110 has a matrix region 111 and a plurality of columnar structures 113 (columnar regions) having a refractive index different from that of the matrix region 111. The anisotropic light diffusing layer 120 has a matrix region 121 and a plurality of columnar structures 123 (columnar regions) having a refractive index different from that of the matrix region 121. Here, when simply expressed as a columnar region, the columnar region includes a pillar region having a pillar structure and a columnar region having a louver structure. Further, when simply expressed as a columnar structure, the columnar structure includes a pillar structure having a pillar structure and a columnar structure having a louver structure.
The plurality of columnar structures (113 and 123) are formed by orienting the plurality of columnar structures from one surface to the other surface in the main plane of the anisotropic light diffusion layer, and the orientation directions of the plurality of columnar structures. Has an aspect ratio of an average minor axis and an average major axis in a cross section whose normal direction is.

Hereinafter, the anisotropic optical films 100 and 150 having such an anisotropic light diffusion layer 110 or an anisotropic light diffusion layer 120 will be described in detail.

<< 2-2. Anisotropic light diffusion layer 110 >>
The anisotropic light diffusing layer 110 has the above-mentioned louver structure (similar structure to the anisotropic optical film 20 of FIG. 1B), and has anisotropy in which the linear transmittance changes depending on the incident light angle. are doing. Further, the anisotropic light diffusing layer 110 is made of a cured product of a composition containing a photopolymerizable compound, and as shown in FIG. 5A, the matrix region 111 and a plurality of regions having different refractive indexes from the matrix region 111. It has a columnar structure 113 (columnar region). The orientation direction (extending direction) P of the columnar structure 113 is parallel to the scattering center axis, and is appropriately determined so that the anisotropic light diffusing layer 110 has a desired linear transmittance and diffusivity. It should be noted that the fact that the central axis of scattering and the orientation direction of the columnar structure are parallel does not have to be exactly parallel as long as it satisfies the law of refractive index (Snell's law). Snell's law states that when light is incident from a medium having a refractive index n ₁ to the interface of a medium having a refractive index n ₂ , n ₁ sin θ ₁ = between the incident light angle θ ₁ and the refraction angle θ _2. The relationship of n ₂ sin θ ₂ is established. For example, assuming that n ₁ = 1 (air) and n ₂ = 1.51 (anisotropic optical film), when the incident light angle is 30 °, the orientation direction (refraction angle) of the columnar structure is about 19 °. However, even if the incident light angle and the refraction angle are different as described above, if Snell's law is satisfied, the concept of parallelism is included in the present embodiment.

The anisotropic light diffusion layer 110 may have an orientation direction of the columnar structure 113 that does not coincide with the film thickness direction (normal direction) of the film. In this case, in the anisotropic light diffusion layer 110, the incident light is strongly diffused in the incident light angle range (diffuse region) close to the direction inclined by a predetermined angle from the normal direction (that is, the orientation direction of the columnar structure 113). In the incident light angle range (non-diffuse region) beyond that, the diffusion is weakened and the linear transmittance is increased.

<2-2-1. Columnar structure 113>
The columnar structure 113 according to the present embodiment is provided as a plurality of columnar hardening regions in the matrix region 111, and each columnar structure 113 is oriented so that the orientation direction is parallel to the scattering center axis. It was formed.

The refractive index of the matrix region 111 may be different from the refractive index of the columnar structure 113, but the degree of difference in the refractive index is not particularly limited and is relative. When the refractive index of the matrix region 111 is lower than the refractive index of the columnar structure 113, the matrix region 111 becomes a low refractive index region. On the contrary, when the refractive index of the matrix region 111 is higher than the refractive index of the columnar structure 113, the matrix region 111 becomes a high refractive index region. Here, it is preferable that the refractive index at the interface between the matrix region 111 and the columnar structure 113 gradually changes. By gradually changing the light, the change in diffusivity when the incident light angle is changed becomes extremely steep, and the problem that glare is likely to occur is less likely to occur. By forming the matrix region 111 and the columnar structure 113 by phase separation accompanying light irradiation, the refractive index of the interface between the matrix region 111 and the columnar structure 113 can be gradually changed.

As shown in FIG. 5A, the cross-sectional shape of the columnar structure 113 perpendicular to the orientation direction has a minor axis SA and a major axis LA. The minor axis SA and the major axis LA can be confirmed by observing the anisotropic light diffusing layer 110 with an optical microscope (details will be described later). The cross-sectional shape of the columnar structure 113 is not particularly limited as long as it is within the range of the aspect ratio described later, but can be, for example, 2 or more and less than 50. In FIG. 5A, the cross-sectional shape of the columnar structure 113 is shown as an elliptical shape, but the cross-sectional shape of the columnar structure 113 is not particularly limited.

<< 2-3. Anisotropic light diffusion layer 120 >>
The anisotropic light diffusing layer 120 has a pillar structure (similar to the anisotropic optical film 10 of FIG. 1A) and has light diffusivity in which the linear transmittance changes depending on the incident light angle. There is. Further, as shown in FIG. 5B, the anisotropic light diffusing layer 120 is made of a cured product of a composition containing a photopolymerizable compound, and the matrix region 121 and the matrix region 121 have a plurality of refractive indexes different from each other. It has a columnar structure 123. The plurality of columnar structures 123 and the matrix region 121 have an irregular distribution and shape, but the optical characteristics (for example, linear transmittance) obtained by being formed over the entire surface of the anisotropic light diffusing layer 120 are omitted. It will be the same. Since the plurality of columnar structures 123 and the matrix region 121 have an irregular distribution and shape, the anisotropic light diffusion layer 120 according to the present embodiment is less likely to cause light interference (rainbow).

<2-3-1. Columnar structure 123>
The columnar structure 123 according to the present embodiment is provided as a plurality of columnar hardened regions in the matrix region 121, and each columnar structure 123 has an orientation direction parallel to the scattering center axis. Is. Therefore, the plurality of columnar structures 123 in the same anisotropic light diffusion layer 120 are formed so as to be parallel to each other.

The refractive index of the matrix region 121 may be different from the refractive index of the columnar structure, but the degree of difference in the refractive index is not particularly limited and is relative. When the refractive index of the matrix region 121 is lower than the refractive index of the columnar structure, the matrix region 121 becomes a low refractive index region. On the contrary, when the refractive index of the matrix region 121 is higher than the refractive index of the columnar structure, the matrix region 121 becomes a high refractive index region.

The cross-sectional shape of the columnar structure 123 perpendicular to the orientation direction has a minor axis SA and a major axis LA, as shown in FIG. 5 (b). The cross-sectional shape of the columnar structure 123 can have an aspect ratio range of less than 2, which will be described later. For example, in FIG. 5B, the cross-sectional shape of the columnar structure 123 is shown as a circular shape, but the cross-sectional shape of the columnar structure 123 is not limited to the circular shape, and is an elliptical shape, a polygonal shape, or the like. The shape is not particularly limited, such as an indefinite shape or a mixture of these.

<< 2-4. Aspect ratio of columnar structure 113 and columnar structure 123 >>
The plurality of columnar structures 113 have an aspect ratio (= average major axis / average minor axis) of 2 or more between the average value (average minor axis) of the minor axis SA and the average value (average major axis) of the major axis LA.

The plurality of columnar structures 123 have an aspect ratio (= average major axis / average minor axis) of less than 2 between the average value (average minor axis) of the minor axis SA and the average value (average major axis) of the average major axis LA.

The aspect ratio of the columnar structure is 1 or more, but the upper limit of the aspect ratio is not particularly limited, but for example, it is preferably less than 50, more preferably 25 or less, still more preferably 10 or less. When the aspect ratio is within such a range, unevenness due to light interference is unlikely to occur, and the display quality can be kept good.

<2-4-1. Average minor axis and average major axis of columnar structure 113 and columnar structure 123>
Further, the average value (average minor axis) of the minor axis SA of the plurality of columnar structures 113 is preferably 0.5 μm or more, more preferably 1.0 μm or more, and 1.5 μm or more. Is more preferable. On the other hand, the average value (average minor axis) of the minor axis SA of the plurality of columnar structures 113 is preferably 5.0 μm or less, more preferably 4.0 μm or less, and 3.0 μm or less. Is more preferable. The lower limit value and the upper limit value of the average minor axis of the plurality of columnar structures 113 can be appropriately combined.

Further, the average value (average major axis) of the major axis LA of the plurality of columnar structures 113 is preferably 0.5 μm or more, more preferably 1.0 μm or more, and 1.5 μm or more. Is even more suitable. On the other hand, the average value (average major axis) of the major axis LA of the plurality of columnar structures 113 is preferably 100 μm or less, more preferably 50 μm or less, and further preferably 30 μm or less. .. The lower limit value and the upper limit value of the average major axis of the plurality of columnar structures 113 can be appropriately combined.

Further, the average value (average minor axis) of the minor axis SA of the plurality of columnar structures 123 is preferably 0.5 μm or more, more preferably 1.0 μm or more, and 1.5 μm or more. Is more preferable. On the other hand, the average value (average minor axis) of the minor axis SA of the plurality of columnar structures 123 is preferably 5.0 μm or less, more preferably 4.0 μm or less, and 3.0 μm or less. Is more preferable. The lower limit value and the upper limit value of the average minor axis of the plurality of columnar structures 123 can be appropriately combined.

Further, the average value (average major axis) of the major axis LA of the plurality of columnar structures 123 is preferably 0.5 μm or more, more preferably 1.0 μm or more, and 1.5 μm or more. Is even more suitable. On the other hand, the average value (average major axis) of the major axis LA of the plurality of columnar structures 123 is preferably 8.0 μm or less, more preferably 5.0 μm or less, and 3.0 μm or less. Is even more suitable. The lower limit value and the upper limit value of the average major axis of the plurality of columnar structures 123 can be appropriately combined.

The anisotropic optical film 100 or 150 according to the present embodiment has a higher level by setting the average minor axis and the average major axis of the plurality of columnar structures 113 or the plurality of columnar structures 123 to the above-mentioned preferable ranges. An anisotropic optical film having various characteristics in a well-balanced manner can be obtained.

The average value of the minor axis SA (mean minor axis) and the average value of the major axis LA (mean major axis) of the plurality of columnar structures 113 and the plurality of columnar structures 123 in the present embodiment are those of the anisotropic light diffusion layer 120. A cross section with the extending direction (orientation direction) of the plurality of columnar structures in the columnar region as the normal direction is observed with a microscope, and the minor axis SA of 100 columnar structures 113 and columnar structures 123 arbitrarily selected. The major axis LA may be measured and the average value thereof may be obtained. Further, as the aspect ratio of the columnar structure, a value obtained by dividing the average value (average major axis) of the major axis LA obtained above by the average value (average minor axis) of the minor axis SA is used.

<< 2-5. Thickness of region where columnar structures 113 and 123 are formed >>
The thickness T of the plurality of columnar structures 113 and 123 is preferably 10 μm to 200 μm, more preferably 20 μm or more and less than 100 μm, and further preferably 20 μm or more and less than 50 μm. .. When the thickness T exceeds 200 μm, not only the material cost is higher, but also the cost for UV irradiation is increased, so that not only the cost is high, but also the increase in diffusivity in the thickness T direction causes image blurring and contrast reduction. It is easy to happen. Further, when the thickness T is less than 10 μm, it may be difficult to make the light diffusivity and light condensing property sufficient. In the present invention, by setting the thickness T within the specified range, the problem of cost is reduced, the light diffusing property and the light condensing property are excellent, and the light diffusing property is lowered in the thickness T direction, so that the image is imaged. Blurring is less likely to occur, and contrast can be improved.

<< 2-6. Properties of anisotropic optical films 100 and 150 >>
As described above, the anisotropic optical films 100 and 150 have an anisotropic light diffusion layer 110 or 120. More specifically, the anisotropic light diffusion layer 110 has a louver structure. The anisotropic light diffusing layer 120 has a pillar structure. Hereinafter, the properties of such anisotropic optical films 100 and 150 will be described.

<2-6-1. Linear transmittance>
Here, the linear transmittance of the light incident on the anisotropic optical film 100 or 150 (anisometric light diffusing layer 110 or 120) at the incident light angle at which the linear transmittance is maximized is defined as the "maximum linear transmittance". The anisotropic optical film 100 or 150 (anisometric light diffusing layer 110 or 120) has a maximum linear transmittance of 15% or more and 85% or less, preferably 15% or more and 80% or less, and more preferably 20%. It can be 75% or more and 75% or less. When the maximum linear transmittance of the anisotropic optical film 100 or 150 is within such a range, good diffusivity can be obtained, and image blurring and reduction in brightness due to excessive diffusion can be suppressed, and a reflective liquid crystal can be obtained. When used on the front side of the display device on the visible side, it is possible to improve the visibility in the front direction of the screen.

The linear transmittance of the light incident on the anisotropic light diffusing layer 110 or 120 at the incident light angle at which the linear transmittance is minimized can be defined as the "minimum linear transmittance". The minimum linear transmittance is not particularly limited, but can be 10% or less.

Here, the amount of linear transmitted light and the linear transmittance can be measured by the method shown in FIG.
That is, the straight line V shown in FIG. 2 is set as the rotation axis, and the amount of linear transmitted light is measured for each incident light angle so as to coincide with the CC axis shown in FIG. 5 (the normal direction is 0 °). An optical profile can be obtained from the obtained data, and the maximum linear transmittance and the minimum linear transmittance can be obtained from this optical profile.

Further, the maximum linear transmittance and the minimum linear transmittance in the anisotropic optical film 100 or 150 (anisotropic light diffusion layer 110 or 120) can be adjusted by design parameters at the time of manufacture. Examples of parameters include the composition of the coating film, the film thickness of the coating film, the temperature applied to the coating film at the time of structure formation, and the like. The composition of the coating film changes the maximum linear transmittance and the minimum linear transmittance by appropriately selecting and blending the constituent components. In terms of design parameters, the thicker the film thickness, the lower the maximum linear transmittance and the minimum linear transmittance tend to be, and the thinner the film thickness, the higher the maximum linear transmittance. The higher the temperature, the lower the maximum linear transmittance and the minimum linear transmittance tend to be, and the lower the temperature, the higher the maximum linear transmittance. By combining these parameters, it is possible to appropriately adjust each of the maximum linear transmittance and the minimum linear transmittance.

<2-6-2. Diffusion width>
By the above method, the maximum linear transmittance and the minimum linear transmittance of the anisotropic optical film 100 or 150 are obtained, and the linear transmittance of an intermediate value between the maximum linear transmittance and the minimum linear transmittance is obtained. The two incident light angles with respect to the linear transmittance of this intermediate value are read. In the optical profile, the normal direction is 0 °, and the incident light angle is shown in the minus direction and the plus direction. Therefore, the incident light angle and the incident light angle corresponding to the intersection may have a negative value.
If the value of the two intersections has a positive incident light angle value and a negative incident light angle value, the sum of the absolute value of the negative incident light angle value and the positive incident light angle value is the diffusion of the incident light. It is the diffusion width, which is the angular range of the region.
When the values of the two intersections are both positive, the difference between the larger value minus the smaller value is the diffusion width, which is the angular range of the incident light angle.
When the values of the two intersections are both negative, the absolute value of each is taken, and the difference obtained by subtracting the smaller value from the larger value is the diffusion width which is the angular range of the incident light angle.

<2-6-3. Scattering center axis>
Next, the scattering center axis P in the anisotropic light diffusion layer will be described with reference to FIG. FIG. 6 is a three-dimensional polar coordinate display for explaining the scattering center axis P in the anisotropic optical film 100 or 150 (anisotropic light diffusion layer).

The anisotropic light diffusing layer has at least one scattering central axis, and as described above, the scattering central axis has a light diffusivity when the incident light angle to the anisotropic light diffusing layer is changed. It means a direction that coincides with the incident light angle having substantially symmetry with the boundary. The incident light angle (scattering center axis angle) at this time is a substantially central portion (central portion of the diffusion region) having substantially symmetry in this optical profile by measuring the optical profile of the anisotropic light diffusion layer.

Further, according to the three-dimensional polar coordinate display as shown in FIG. 6, the scattering center axis has a polar angle θ and an azimuth angle when the surfaces of the anisotropic light diffusion layers 110 and 120 are xy planes and the normal is the z axis. It can be expressed by φ. That is, it can be said that Pxy in FIG. 6 is the length direction of the scattering center axis projected on the surface of the anisotropic light diffusion layer.

The scattering center axis angle is less than 6 ° with respect to the anisotropic optical films 100 and 150. When the scattering center axis angle is within such a range, the light collection property in the normal direction of the layer plane is exhibited, so that the reflection brightness in the front direction, which is the viewing direction, is improved and the visibility is improved. Is possible.

Here, each of the anisotropic light diffusion layers 110 and 120 may have a plurality of columnar region groups having different slopes (a set of columnar regions having the same slope) in a single layer. The absolute value of this difference in the scattering center axis angle is less than 12 °.

<2-6-4. Refractive index>
The anisotropic light diffusion layers 110 and 120 are obtained by curing a composition containing a photopolymerizable compound, and the following combinations can be used as this composition.
(1) A single photopolymerizable compound is used (2) A plurality of photopolymerizable compounds are mixed and used (3) A single or multiple photopolymerizable compounds and a polymer compound having no photopolymerizability What is used by mixing

In any of the above combinations, it is presumed that micron-order fine structures having different refractive indexes are formed in the anisotropic light diffusion layer 110 or 120 by light irradiation, whereby the peculiarity shown in the present embodiment is shown. It is considered that various anisotropic light diffusion characteristics are exhibited. Therefore, in (1) above, it is preferable that the change in refractive index before and after photopolymerization is large, and in (2) and (3), it is preferable to combine a plurality of materials having different refractive indexes. The change or difference in refractive index here is specifically, preferably 0.01 or more, more preferably 0.05 or more, and further preferably 0.10 or more. Is shown.

Here, when the refractive index of the matrix region 111 or 121 is higher than the refractive index of the columnar structure 113 or 123, the matrix region 111 or 121 becomes a high refractive index region, and the plurality of columnar structures 113 or 123 have a low refractive index. It becomes an area. The difference in refractive index between the matrix region 111 or 121 (high refractive index region) and the columnar structure 113 or 123 (low refractive index region) is not particularly limited, but is, for example, in the range of 0.01 to 0.50. The range is preferably 0.03 to 0.20. When the difference in refractive index is within such a range, good diffusivity is exhibited and backscattering can be suppressed, and when used in front of the visible side of a reflective liquid crystal display device, the screen thereof. It is possible to improve the visibility in the front direction.

<<< 3. Isotropic light diffusion layer 200 >>>
The isotropic light diffusing layer 200 (for example, FIG. 7) is a layer using a light-transmitting resin as a base material and containing fine particles that diffuse light due to a difference in refractive index from the base material. The isotropic light diffusing layer 200 diffuses light regardless of the incident angle of the light, and has no directionality in diffusivity. More specifically, when light is diffused by the isotropic light diffusing layer 200, the degree of diffusion of the light (diffused light) in a plane parallel to the isotropic light diffusing layer 200 in the diffused light (emitted light). The shape of the spread of light) has the property of not changing depending on the direction in the same plane.

<< 3-1. Resin base material >>
As the resin constituting the isotropic light diffusion layer 200, acrylic resin, polyester resin, epoxy resin, polyurethane resin, silicone resin and the like have been conventionally known, but they have high optical transparency. Acrylic resins are particularly preferable because they have good workability, have a refractive index close to that of a TAC film which is a protective film for a polarizing plate, and are relatively inexpensive. Further, the resin may be provided with adhesiveness so that the isotropic light diffusing layer 200 can be easily laminated with another member (for example, a reflective display device). In this case, the pressure-sensitive adhesive made of an acrylic resin is preferably used in the present embodiment because, in addition to the advantages of the acrylic resin, it is highly reliable and has a good track record as a pressure-sensitive adhesive for polarizing plates.

<< 3-2. Fine particles, other ingredients >>
Further, as the fine particles mixed and dispersed in the resin, those having a different refractive index from the resin as the base material and which are colorless or white are preferable in order to prevent coloring of transmitted light. For example, inorganic fine particles and white pigments. And resin fine particles and the like. Specific examples thereof include silica fine particles, alumina fine particles, zirconium fine particles, silicone fine particles, acrylic resin fine particles, polystyrene resin fine particles, styrene-acrylic copolymer resin fine particles, polyethylene resin fine particles, epoxy resin fine particles and the like. Further, if necessary, one or a mixture of two or more cross-linking agents such as metal chelate type, isocyanate type and epoxy type can be used in the resin.

Further, as other components for forming the isotropic light diffusion layer 200, in addition to an initiator such as a photoinitiator and a thermosetting initiator and a solvent, a thickener, a surfactant, a dispersant, if necessary, A plasticizer, a leveling agent, etc. can be added.

<< 3-3. Refractive index >>
The difference between the refractive index of the base resin (method B according to JIS K-7142) and the refractive index of the fine particles is preferably in the range of 0.01 to 0.10, and is 0.02 to 0.05. It is more preferable that it is in the range.

In this embodiment, it is preferable to use an acrylic pressure-sensitive adhesive and silicone resin fine particles. The refractive index of the silicone resin fine particles is 1.40 to 1.45, which is slightly lower than the refractive index of 1.45 to 1.55 of the acrylic pressure-sensitive adhesive. It has a high light transmittance, less backscattering and less depolarization, and is excellent for application to reflective display devices.

<< 3-4. Average particle size >>
The average particle size of the fine particles is not particularly limited, but can be, for example, 0.5 μm to 10.0 μm, and more preferably 1 μm to 5.0 μm. If the average particle size is less than 0.1 μm, the light diffusion performance is low and the metallic luster of the light reflector becomes visible, so that paper whiteness cannot be obtained. On the other hand, if the average particle size exceeds 10 μm, the particles are too coarse and a satin pattern or glare appears on the background of the screen, resulting in a decrease in contrast. The average particle size referred to here is measured by the Coulter counter method.

<< 3-5. Content >>
The content of the fine particles in the isotropic light diffusing layer 200 is preferably 5.0% by weight to 50.0% by weight, and more preferably 7.5% by weight to 45% by weight. If the content is less than 5.0% by weight, the light diffusivity is lowered, and if it exceeds 50.0% by weight, it becomes difficult to uniformly disperse the fine particles in the isotropic light diffusing layer 200, and the light diffusing property and the like. When the optical properties of the above are deteriorated or when the adhesive is used, the adhesive strength is lowered and peeling is likely to occur.

<< 3-6. Haze value >>
The haze value of the isotropic light diffusion layer 200 is preferably 80% or more, and more preferably 85% or more. The upper limit of the haze value is not particularly limited, but can be, for example, 95% or less. When the haze value is within such a range, the amount of light transmitted linearly can be reduced, and the visibility in front of the viewing side of the reflective liquid crystal display device can be improved. If it is less than 80%, sufficient diffusion cannot be obtained and the brightness decreases. Further, even if the haze value is 95% or more, the brightness is lowered and the image is easily blurred. Here, the haze value (Hz,%) is a value calculated by the following formula by measuring the diffusion transmittance (%) and the total light transmittance (%) in accordance with JIS K7105. Hz (%) = (diffusion transmittance / total light transmittance) × 100

<< 3-7. Linear transmittance >>
The maximum linear transmittance of the isotropic light diffusing layer 200 is 35% or less. The lower limit of the maximum linear transmittance of the isotropic light diffusing layer 200 is not particularly limited, but can be, for example, 15% or more. The minimum linear transmittance of the isotropic light diffusion layer 200 is not particularly limited, but can be 0.5% or more and 10% or less. When the maximum linear transmittance of the isotropic light diffusing layer 200 is within such a range, good diffusivity can be obtained, and when it is used on the front side of the viewing side of the reflective liquid crystal display device, the front direction of the screen. It is possible to increase the visibility of the.

The thickness of the isotropic light diffusion layer 200 is preferably 5 μm or more and less than 100 μm, more preferably 10 μm or more and less than 50 μm, and further preferably 10 μm or more and less than 25 μm. If the thickness is thick (for example, 100 μm or more), the image tends to be blurred, which is not suitable. Further, if the thickness is thin (for example, less than 5 μm), the adhesive force when the adhesive is used becomes insufficient, which is not preferable.

<<< 4. Arrangement configuration of anisotropic optical film 100 and isotropic light diffusion layer 200 (light diffusion film laminate 30) >>>
As shown in FIG. 7A, the light diffusion film laminate 30 according to the present embodiment is an anisotropic optical film (lamination) in which the above-mentioned anisotropic optical film 100 or 150 and the isotropic light diffusion layer 200 are laminated. Body). In the light diffusion film laminate 30, the anisotropic optical film 100 or 150 is arranged on a surface on which external light such as the sun is incident or on the visual side (front direction of the screen, outer surface side) of the viewer, and the anisotropic optical film 100 or 150 is arranged. It is preferable that the isotropic light diffusion layer 200 is arranged on the back surface of the film 100 or 150 (one surface opposite to the viewing side). With such an arrangement, the anisotropy of the anisotropic optical film 100 or 150 can be effectively used, and the brightness in the front direction of the screen is increased, the visibility is improved, and blurring is difficult. It becomes an image.

Further, with respect to the light diffusing film laminate 30 in which the anisotropic optical film 100 or 150 and the isotropic light diffusing layer 200 are laminated, the “maximum straight line” which is the linear transmittance at the incident light angle at which the linear transmittance is maximized. "Transmittance" is 10% or less. The lower limit of the maximum linear transmittance is not particularly limited, but may be 5% or more. The "minimum linear transmittance", which is the linear transmittance at the incident light angle at which the linear transmittance is minimized, is not particularly limited, but can be 2% or less, and the anisotropic optical film 100 or 150 can be used. It is preferable that the diffusivity of the incident light increases as the linear transmittance decreases.

In the case of a reflective display device (for example, a liquid crystal type) that requires a polarizing plate, the surface of the anisotropic optical film 100 or 150 (the side where the reflected light is visually recognized, the external light incident surface side, or the viewer). On the visual side), for example, a TAC film, a retardation film, a polarizing plate, or the like may be laminated via an adhesive. In the case of a reflective display device (for example, other than a liquid crystal) that does not use a polarizing plate, a PET film, a TAC film, or the like may be laminated on the outer surface of the anisotropic optical film 100 or 150, for example, via an adhesive. Good.

In this way, the light diffusing film laminate 30 in which the anisotropic optical film 100 or 150 and the isotropic light diffusing layer 200 are laminated is combined with the reflective layer 300 (for example, a reflective film, a reflective plate) shown in FIG. 7 (b). By applying it to a device having a device (for example, a reflective display device) that reflects light such as, the anisotropic optical film 100 or 150 at the time of incident external light and emitted reflected light. It is possible to minimize the hindrance of the effect, and in particular, it is possible to maintain the reflected brightness in the front direction of the screen of the reflective display device. Various functional layers such as an adhesive layer, a retardation film, a polarizing plate, a liquid crystal layer, and a transparent electrode layer may be present alone or a plurality between the light diffusing film laminate 30 and the reflective layer 300.

In the anisotropic optical films 100 and 150, the incident light is strongly diffused in the incident light angle range close to the scattering center axis direction, and exhibits light collecting property in the scattering center axis direction. However, in the incident light angle range beyond that, the diffusion is weakened and the light collecting property is lowered.
Here, the scattering central axis of the anisotropic optical films 100 and 150 is the normal direction of the main plane of the anisotropic optical films 100 and 150, and the diffusion region of the anisotropic optical films 100 and 150 is −20. It is assumed to be ° to + 20 °. When the incident light angle of the light with respect to the scattering center axis direction is 10 °, the incident light is incident in a range having high diffusivity, so that the light is condensed in the scattering center axis direction.
That is, the anisotropic optical films 100 and 150 diffuse and condense light at a predetermined incident angle (in the above assumption, −20 ° to + 20 °) in a predetermined direction (scattering center axis direction). It is possible to maintain a high intensity (brightness) of the light.

As described above, the isotropic light diffusing layer 200 uses light diffusing fine particles that diffuse light, and has the property of diffusing light regardless of the incident angle of light and having no directionality in diffusivity. Therefore, the anisotropic optical films 100 and 150 can also diffuse light from a direction having weak diffusivity.
That is, the isotropic light diffusing layer diffuses light from a direction that is difficult to diffuse and condense with the anisotropic light diffusing layer alone, so that the diffused light can be condensed by the anisotropic light diffusing layer.

The light emitted from the light diffusing film laminate 30 is reflected by the reflective layer 300. The reflected light is again incident on the light diffusing film laminate 30 and emitted. As a result, the reflected brightness of the reflective display device in the front direction (0 °) of the screen can be increased.

<<< 5. Reflective display device >>>
The reflective display device used in the present embodiment is not particularly limited as long as it has a reflective function. Specific examples of display methods include electronic powder and granular material, liquid crystal (cholesteric liquid crystal, bistable nematic liquid crystal, pixel memory liquid crystal, etc.), electrowetting method, electrochromic method, electrophoresis method (microcapsule, etc.). Etc., a reflective display device using a known technique can be applied.

Here, the laminated portion of the light diffusing film laminate of the present invention in the reflective display device is not particularly limited as long as it is a layer between the time when the light is reflected and the time when it is visually recognized, but it is preferable. On the side of the incident surface of external light (the side where the viewer sees the reflected light, the side where the reflected light is seen) in the reflective display device, the image forming part in each display method (for example, in the case of the electrophoresis method, the microcapsule portion and the electron powder granules A flat base material surface (outside) that is on the front side of the electronic powder and granular material encapsulation location in the method, the water and oil film encapsulation location in the electro-wetting method, and the liquid crystal layer in the liquid crystal method). It is laminated on the light incident surface side).

Here, the flat base material is specifically glass, a resin molded body, a film, or the like. The light diffusing film laminate of the present invention is laminated on a flat base material surface (external light incident surface side, side where reflected light is visually recognized), and at that time, the flat base material surface of the reflective display device is used. It is not limited whether the anisotropic optical film of the light diffusing film laminate or the isotropic light diffusing layer is laminated on the top. The external light incident surface side (the visible side of the viewer, the side that visually recognizes the reflected light) is the anisotropic optical film in the light diffusion film laminate, and the external light reflecting surface side, which is the opposite side to the external light incident surface, is. , It is preferable that the light diffusing layer is laminated on a flat base material surface.

At that time, if the isotropic light diffusing layer is laminated on the planar base material surface so that the external light reflecting surface side becomes an isotropic light diffusing layer, the isotropic light diffusing layer is directly applied as an adhesive when the isotropic light diffusing layer is an adhesive. If this is not the case, an isotropic light diffusing layer may be laminated via an adhesive. On the other hand, when laminating on a flat base material surface so that the external light reflecting surface side becomes an anisotropic optical film, laminating may be performed via a transparent adhesive of a known technique.

Further, if the external light reflecting surface side is laminated on the planar base material surface so as to be an anisotropic optical film, the surface of the isotropic light diffusion layer (the side where the reflected light is visually recognized, the external light incident surface side or the visual recognition). A TAC film, a retardation film, a polarizing plate, or the like may be laminated on the visible side of the person), if necessary, via, for example, an adhesive.

<<< 6. Example >>>
Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these examples.

According to the following method, the light diffusing film laminate of the present invention (anisotropic optical film and isotropic light diffusing layer, in this embodiment, the anisotropic optical film has an anisotropic light diffusing layer as a single layer) and A comparative example was prepared. The anisotropic light diffusing layer was prepared with reference to the existing methods shown below (for example, Japanese Patent Application Laid-Open No. 2006-119241 and International Publication No. WO2014 / 084361). The isotropic light diffusion layer was prepared with reference to the existing method shown below (for example, JP-A-2002-122714).

<< Anisotropic optical film >>
A partition wall having a height of 50 μm was formed of a curable resin using a dispenser around the entire edge of a PET film having a thickness of 100 μm (manufactured by Toyobo Co., Ltd., trade name: A4300). The following UV curable resin composition was added dropwise thereto, and the mixture was covered with another PET film.

<UV curable resin composition>
-Silicone urethane acrylate (refractive index: 1.460, weight average molecular weight: 5,890) 20 parts by weight (manufactured by RAHN, trade name: 00-225 / TM18)
-Neopentyl glycol diacrylate (refractive index: 1.450) 30 parts by weight (manufactured by Daicel Cytec, trade name: Ebecryl 145)
EO adduct diacrylate of bisphenol A (refractive index: 1.536) 15 parts by weight (manufactured by Daicel Cytec, trade name: Ebecil150)
・ Phenoxyethyl acrylate (refractive index: 1.518) 40 parts by weight (manufactured by Kyoeisha Chemical Co., Ltd., trade name: light acrylate PO-A)
・ 2,2-Dimethoxy-1,2-diphenylethane-1-one 4 parts by weight (manufactured by BASF, trade name: Irgacure 651)

An irradiation intensity of 30 mW / cm ^{2 was} applied to a liquid film having a thickness of 50 μm sandwiched between PET films on both sides from an irradiation unit for epi-illumination of a UV spot light source (manufactured by Hamamatsu Photonics, trade name: L2859-01). Eight kinds of anisotropic light diffusing layers with PET (anisometric optical film) having a thickness of 50 μm and having a large number of rod-shaped minute regions as shown in FIG. 1 or 5 by irradiating ultraviolet rays as parallel rays for 1 minute. Got The eight types of anisotropic light diffusing layers produced are shown in Table 1 below.

The maximum linear transmittance and the scattering center axis angle (relative to the normal direction of the anisotropic light diffusion layer), which are the optical characteristics of each anisotropic light diffusion layer, and the aspect ratio of each columnar structure are the ultraviolet curable resin composition. In addition to adjusting the heating temperature of the liquid film and the direction of the ultraviolet rays to be irradiated, a directional diffusion element capable of changing the aspect ratio of parallel rays is arranged between the anisotropic light diffusion layer and the irradiation unit for epi-illumination. By adjusting whether or not to do so, and when using a directional diffusing element, adjusting the arrangement of the directional diffusing element (approaching or moving away from the anisotropic light diffusing layer), as shown in Table 1. Eight kinds of anisotropic light diffusing layers having characteristics could be obtained.

The directional diffusion element imparts directivity to the incident parallel light rays, and in this embodiment, an directional diffusion element containing needle-like fine particles having a high aspect ratio was used. The aspect ratio of the columnar structure was formed in a form substantially corresponding to the aspect ratio of the parallel rays changed by the directional diffusion element.

<Measurement of the angle of the scattering center axis of the anisotropic light diffusion layer and the linear transmittance>
Anisotropic optics of the examples shown in Table 1 using a goniometer (manufactured by Genesia), a variable-angle photometer that can arbitrarily change the projection angle of the light source and the light-receiving angle of the detector as shown in FIG. The linear transmittance of the film (anisometric light diffusion layer) was measured. The detector was fixed at a position where it received straight light from the light source, and the anisotropic optical film obtained in the example was set in the sample holder between them. As shown in FIG. 2, the sample was rotated around the straight line V as the rotation axis, and the amount of linear transmitted light corresponding to each incident light angle was measured. By this evaluation method, it is possible to evaluate in what angle range the incident light is diffused. This axis of rotation is the same axis as the CC axis in the sample structure shown in FIG. For the measurement of the amount of linear transmitted light, the wavelength in the visible light region was measured using a luminosity factor filter. Based on the optical profile obtained as a result of the above measurement, the center between the maximum value (maximum linear transmittance) and the minimum value (minimum linear transmittance) of the linear transmittance and the minimum value in the optical profile. The maximum linear transmittance and the scattering center axis angle were obtained from the part (the central part of the diffusion region) and summarized in Table 1.

<Measurement of aspect ratio of columnar structure (surface observation of anisotropic light diffusion layer)>
Extending direction of a plurality of columnar structures in the columnar region of the anisotropic light diffusion layer of Examples and Comparative Examples (direction in which the columnar structures are oriented from one surface to the other surface in the main plane of the anisotropic light diffusion layer. ) Is the normal direction (however, the irradiation light side at the time of ultraviolet irradiation) is observed with an optical microscope, and the major axis LA and minor axis SA of the columnar structure in the columnar region are measured. For the calculation of the average major axis LA and the average minor axis SA, the average value among any 100 structures was used. In addition, the average major axis LA / average minor axis SA was calculated as an aspect ratio with respect to the obtained average major axis LA and average minor axis SA, and is summarized in Table 1.

<< Isotropic light diffusion layer >>
An acrylic pressure-sensitive adhesive (trade name: SK Dyne TM206, total solid content concentration 18. 8%, solvent: ethyl acetate, methyl ethyl ketone, manufactured by Soken Kagaku Co., Ltd. 0.5 parts of isocyanate-based curing agent (trade name: L-45, manufactured by Soken Kagaku Co., Ltd.) and epoxy-based curing agent (manufactured by Soken Kagaku Co., Ltd.) Product name: E-5XM, manufactured by Soken Kagaku Co., Ltd. Silicone resin fine particles (Tospearl 145, refractive index 1.43, particle diameter 4) as fine particles having a different refractive index from the above-mentioned adhesive to the base paint to which 0.2 part is added. Add a predetermined amount of .5 μm) and stir with an agitator for 30 minutes to disperse the fine particles, and apply four types of isotropic light diffusion layer paints so that the film thickness after solvent drying is 25 μm or 50 μm. Was dried to form an isotropic light diffusing layer, and then a 38 μm-thick release PET film (manufactured by Lintec Co., Ltd., trade name: 3801) was laminated to prepare four types of isotropic light diffusing layers with PET. The prepared isotropic light diffusion layer is shown in Table 2 below. For comparison, a transparent adhesive layer e blended without adding silicone resin fine particles as a transparent adhesive layer was also produced at the same time.

<Measurement of linear transmittance of isotropic light diffusion layer or transparent adhesive layer>
The maximum linear transmittances of the isotropic light diffusing layer and the transparent adhesive layer were measured in the same manner as the measurement in the anisotropic light diffusing layer shown above except that the rotation axis of the sample was arbitrary, and are summarized in Table 2.

<Measurement of haze>
The haze value (Hz) was measured using a haze meter manufactured by Nippon Denshoku Industries Co., Ltd., NDH-2000, and is summarized in Table 2.

(Example 1)
The above-mentioned anisotropic light diffusing layer 1 with PET and the isotropic light diffusing layer a with PET are laminated after peeling the PET film on each other's laminating surface, and is composed of two layers of an anisotropic optical film / isotropic light diffusing layer. The light diffusing film laminate of Example 1 was obtained.
Subsequently, the PET film on the anisotropic light diffusing layer 1 side was peeled off, and a highly transparent PET (Toyobo Cosmo Shine A4100 100 μm) was attached via the transparent adhesive layer e. Further, the PET film on the surface of the isotropic light diffusion layer a side was peeled off, and then bonded to a smooth specular reflector (reflectance of about 90%) to prepare a sample for evaluation of reflected brightness.
From the above, the configuration of the light diffusing film laminate of Example 1 is shown in Table 3.

(Examples 2 to 7, Comparative Examples 1 to 6)
Examples 2 to 7 were prepared in the same manner as in Example 1 except that the combination of the anisotropic light diffusing layer and the isotropic light diffusing layer in Table 3 was followed, and consisted of two layers of an anisotropic optical film / isotropic light diffusing layer. And the light diffusing film laminates of Comparative Examples 1 to 6 were obtained.
Subsequently, the PET film on the 2 to 8 side of the anisotropic light diffusing layer was peeled off, and a highly transparent PET (Toyobo Cosmo Shine A4100 100 μm) was attached via the transparent adhesive layer e. Further, the PET film on the isotropic light diffusion layer a to d side surface or the transparent adhesive layer e side surface was peeled off, and then attached to a smooth specular reflector (reflectance of about 90%) to prepare a sample for evaluation of reflection luminance.
From the above, the configurations of the light diffusing film laminates of Examples 2 to 7 and Comparative Examples 1 to 6 are shown in Table 3.

<< Evaluation method >>
The light diffusing film laminates produced in Examples 1 to 7 and Comparative Examples 1 to 6 described above were evaluated as follows. The evaluation results are shown in Table 4 below.

<Measurement of linear transmittance of light diffusing film laminate>
The linear transmittance of the light diffusing film laminate was measured in the same manner as the measurement in the anisotropic light diffusing layer shown above, except that the rotation axis of the sample was based on the anisotropic light diffusing layer in the light diffusing film laminate.

<Preparation of standard reflection brightness>
As a standard in the reflection brightness measurement, a reference sample was prepared in which the isotropic light diffusion layer b was bonded between a highly transparent PET (Toyobo Cosmo Shine A4100 100 μm) and a smooth specular reflector (reflectance of about 90%).

<Measurement of reflected brightness>
Using a Genesia goniometer as shown in FIG. 8, the reflection brightness of the reflection brightness evaluation samples obtained in each Example and Comparative Example was measured. Collimated light was irradiated from the light source of the halogen lamp through the collimating lens at an incident angle of 15 ° with respect to the normal direction of the sample (incident angle = 15 °). At this time, in the case of the sample using the anisotropic light diffusion layer, irradiation was performed from an azimuth direction (opposite azimuth angle) 180 ° different from the azimuth direction of the scattering central axis. The azimuth direction is arbitrary in the case of the reference sample that does not use the anisotropic light diffusion layer. The detector was installed in the normal direction of the sample and the reflected brightness was measured (measurement angle = 0 °). The ratio of the reflected brightness of the evaluation sample to the reflected brightness of the reference sample was used as the reflected brightness gain, and this was used as an index of the reflected light intensity.
Reflection brightness gain = (reflection brightness of sample ÷ reflection brightness of reference sample) × 100
Similarly, the reflection brightness when the incident angles were 30 ° and 45 ° was also measured.

<Criteria for judging reflected brightness gain>
The larger the incident angle, the more remarkable the difference in the reflected luminance gain appears. Therefore, the determination was made as follows according to the incident angle.
When the incident angle was 15 °, less than 0.90 was evaluated as x, 0.90 or more and less than 1.00 was evaluated as ◯, and 1.00 or more was evaluated as ⊚.
When the incident angle was 30 °, less than 0.90 was evaluated as x, 0.90 or more and less than 1.80 was evaluated as ◯, and 1.80 or more was evaluated as ⊚.
When the incident angle was 45 °, less than 0.90 was evaluated as x, 0.90 or more and less than 2.50 was evaluated as ◯, and 2.50 or more was evaluated as ⊚.

<< Evaluation result >>
As shown in Examples 1 to 7, the reflected luminance gain of the present invention using a predetermined anisotropic light diffusing layer (anisotropic optical film) and an isotropic light diffusing layer has an incident angle as compared with Comparative Examples 1 to 6. It is excellent regardless. Although Comparative Examples 1 to 3 were excellent in the reflected luminance gain at an incident angle of 30 ° or 45 °, the reflected luminance gain at an incident angle of 15 ° was low. On the contrary, in Comparative Examples 4 to 6, the reflected luminance gain at the incident angle of 15 ° was good, but the reflected luminance gain at the incident angles of 30 ° and 45 ° was low.

The present invention evaluates the present invention by supplementing the diffusion function of an anisotropic optical film by using a specific isotropic light diffusion layer together with a specific anisotropic optical film as a diffusion medium having specific diffusion characteristics. It is probable that the results could be obtained.

Therefore, when the light diffusing film laminate of the example is used in, for example, a reflective display device, the diffusivity of the anisotropic optical film (anisometric light diffusing layer) when the external light is incident and the reflected light is emitted. Since the diffusion effect of the isotropic light diffusion layer can be utilized even at a low angle, the reflected brightness gain in the front direction (that is, the reflected light intensity) is not deteriorated even under external light from all directions. ) Can be increased.

In the present embodiment, an example of applying the light diffusing film laminate to a reflective display device has been described. Specifically, the reflective display device includes, for example, a tabbed terminal such as a smartphone, a wristwatch, a game machine, or a notebook type. Examples include personal computers.

Although the preferred embodiment of the present invention has been described above with reference to the drawings, the present invention is not limited to the above-described embodiment. That is, it is understood that other forms or various modifications that can be conceived by those skilled in the art within the scope of the invention described in the claims also belong to the technical scope of the present invention.

10,20 Anisotropic optical film (anisotropic diffusion layer)
11 and 21 Matrix region 13 Columnar structure (pillar structure)
23 Columnar structure (louver structure)
30 Light diffusing film laminate 100, 150 Anisotropic optical film 110, 120 Anisotropic light diffusing layer 111, 121 Matrix region 113 Column structure (louver structure)
123 Columnar structure (pillar structure)
200 Isotropic light diffusion layer 300 Reflection layer P Scattering center axis

Claims (6)

1. A light diffusing film laminate for a reflective display whose diffusivity changes depending on the incident angle of light.
   The light diffusion film laminate is
   An anisotropic light diffusing layer whose linear transmittance changes depending on the incident angle of light,
   At least an isotropic light diffusion layer provided on one surface side of the anisotropic light diffusion layer is provided.
   The anisotropic light diffusion layer has a matrix region and a columnar region composed of a plurality of columnar structures inside thereof.
   The scattering center axis angle of the anisotropic light diffusion layer is less than 6 ° with respect to the normal direction of the anisotropic light diffusion layer.
   The maximum linear transmittance of the anisotropic light diffusing layer is 15% or more and 85% or less.
   The maximum linear transmittance of the isotropic light diffusion layer is 35% or less.
   A light diffusing film laminate for a reflective display device, characterized in that the maximum linear transmittance of the light diffusing film laminate for a reflective display device is 10% or less.
2. The light diffusion film laminate for a reflective display device according to claim 1, wherein the haze value of the isotropic light diffusion layer is 80% or more.
3. The plurality of columnar structures are configured to be oriented from one surface of the anisotropic light diffusion layer to the other surface, and the average minor axis and the average in the cross section in which the orientation direction of the plurality of columnar structures is the normal direction. The light diffusing film laminate for a reflective display device according to claim 1 or 2, wherein the aspect ratio with the major axis is less than 50.
4. The isotropic light diffusion layer contains fine particles inside, and the isotropic light diffusion layer contains fine particles.
   The light diffusing film laminate for a reflective display device according to any one of claims 1 to 3, wherein the average particle size of the fine particles is 0.5 μm to 10.0 μm.
5. The light diffusing film laminate for a reflective display device according to any one of claims 1 to 4,
   A reflective display device including a reflective layer provided on a side opposite to the visible side of the light diffusing film laminate for a reflective display device.
6. The fifth aspect of the present invention, wherein the light diffusing film laminate for a reflective display device is provided in the order of the anisotropic light diffusing layer and the isotropic light diffusing layer from the side where the reflected light is visually recognized. Reflective display device.

Images