JP7245004B2 - Light diffusion control laminate and reflective display - Google Patents

Description

The present invention relates to a light diffusion control laminate and a reflective display. In particular, the present invention relates to a light diffusion control laminate and a reflective display that exhibit good light diffusion characteristics even when light from a front light enters the light diffusion film at a large angle.

As a display device for displaying visual information such as characters and images as an image, a transmissive display device using an internal light source (backlight) incorporated in the display device, especially a transmissive liquid crystal display device is often used. ing.

In a transmissive liquid crystal display device, light from a backlight is transmitted through a liquid crystal layer or blocked by the liquid crystal layer to form an image to be displayed, which is viewed by an observer as display light. However, when the image is displayed outdoors, light (external light) from an external light source such as sunlight is incident toward the backlight. There is a problem that the visibility is lowered.

On the other hand, if the light from the backlight is increased in order to improve the visibility of the display light, the visibility improves to some extent, but there is a problem that the power consumption increases.

Therefore, in order to improve the visibility of display light outdoors, a reflective display device or a semi-transmissive semi-reflective (liquid crystal) display device is used. As reflective display devices, reflective liquid crystal display devices, electronic paper, digital signage, and the like are known.

In a reflective liquid crystal display device, external light incident on a display portion is reflected by a reflector provided inside the display portion to obtain reflected light. This reflected light is transmitted through the liquid crystal layer or blocked by the liquid crystal layer to form an image to be displayed, which is viewed by an observer as display light.

Since the visibility of display light in a reflective display device depends on the amount of outside light, the visibility of the display light is reduced when the outside light is low. A reflective display device is known that includes a front light that illuminates a display section from the direction of incidence of external light in order to prevent deterioration in the visibility of display light when there is little external light.

By the way, since light travels straight, in the reflective display device described above, a sufficient viewing angle cannot be obtained with only a display portion such as a liquid crystal layer and a reflective layer. Therefore, a light diffusion layer is required so that the display area can obtain a uniform and bright viewing angle. The light diffusion layer may be formed from various materials such as a film having unevenness formed on the surface by fine particles, a film having a smooth surface and having fine particles inside, and a film having an uneven shape transferred to the surface. However, these films suffer from surface scattering and backscattering of incident light, resulting in whitish images or insufficient reflected light.

On the other hand, when a light diffusing film having a refractive index distribution inside the light diffusing layer is used, surface scattering and back scattering of incident light can be prevented, and a bright image with excellent contrast can be obtained.

As a light diffusion film having such a refractive index distribution inside, a film in which a plurality of high refractive index regions and low refractive index regions are alternately present and each region extends in the thickness direction is preferably used. mentioned.

As a light diffusion film having a refractive index distribution inside, for example, light diffusion films as shown in Patent Documents 1 to 3 are known. For example, there is known a light diffusion film having a so-called louver structure, in which plate-like regions with a high refractive index and plate-like regions with a low refractive index are alternately arranged in parallel in the plane direction of the film. Also known is a light diffusion film having a so-called columnar structure, which is a structure in which a plurality of columns with a relatively high refractive index stand in a region with a relatively low refractive index along the thickness direction of the film. ing.

Patent Literature 1 discloses a light diffusion film used in a reflective or transflective liquid crystal display device. This light diffusion film has a louver structure. In Patent Document 1, a light diffusion film having a louver structure is arranged in a liquid crystal display device, and diffuses light incident on the light diffusion film from the outside, and the reflected light reflected inside the liquid crystal display device is reflected by the light diffusion film. It is described that the reflected light is transmitted when incident on the .

Patent Document 2 discloses a reflective liquid crystal display device with a front light. As a light diffusion layer used for this, a structure in which a film having a louver structure and a film having a column structure are laminated is mentioned. Patent Literature 2 describes that incident light passes through the light diffusion layer as it is, is reflected inside the liquid crystal display device, and is diffused by reentering the light diffusion layer.

Patent Document 3 discloses a light diffusion film for use in a reflective or transflective liquid crystal display device with external illumination. This light diffusion film has a louver structure or a column structure. Further, in the light diffusion film, the inclination angles of the plate-like regions forming the louver structure or the columnar structures forming the column structure continuously change in the in-plane direction.

JP-A-2004-126606 Japanese Patent Application Laid-Open No. 2011-186002 Japanese Patent No. 5818719

However, although Patent Document 1 discloses a reflective liquid crystal display device having a front light, it does not describe diffusing light emitted from the front light with a light diffusion film.

Further, although Patent Document 2 also discloses a reflective liquid crystal display device having a front light, the front light described in Patent Document 2 has a configuration in which a light source is provided in front of the display area. . Therefore, the light from the front light does not enter the light diffusion film in a large angle range.

The large-angle region means a region in which the normal to the surface of the light diffusion film forms a large angle with the incident light.

In addition, since the incident light from the external illumination provided in the reflective or transflective liquid crystal display device described in Patent Document 3 directly enters the display section from the light source, it has an incident angle distribution in the display section. are doing. Therefore, it is different from light emitted from a normal front light having a light guide plate.

The present invention has been made in view of such circumstances, and its object is to provide a front light and a light diffusion film that have good light diffusion characteristics even when the light emitted from the front light is incident on the light diffusion film at a large angle. It is to provide a combination with a diffusion film.

Aspects of the present invention include:
[1] having a front light section and a first light diffusion section into which light emitted from the front light section is incident;
The first light diffusing part alternates plate-shaped objects with a relatively high refractive index along an arbitrary direction along the main surface of the first light diffusing part in the region with a relatively low refractive index. It has a louver structure arranged in parallel,
When the angle formed by the normal line of the surface of the first light diffusion portion and the incident light to the first light diffusion portion is defined as the first incident angle, the range of the first incident angle is 40° or more and less than 90°. can be,
the range of incident angles in which the emitted light from the first light diffusing part is obtained as diffused light includes the range of the first incident angles;
The plate-like region is inclined with respect to the normal to the surface of the first light diffusing portion, and the angle formed by the normal to the surface of the first light diffusing portion and the plate-like region closest to the front light portion is defined as the first angle. The light diffusion control layered product is characterized in that the first tilt angle is 15° or more and 50° or less when one tilt angle is set.

Note that the incident angle and the tilt angle are determined by the incident light from the front light portion and The angle formed with the normal to the surface of the first light diffusing portion is positive, and the opposite inclination is negative.

[2] In the first light diffusing part, the inclination angle formed by the normal to the surface of the first light diffusing part and the plate-like region is the surface on the opposite side of the surface of the first light diffusing part facing the front light part. The light diffusion control layered product according to [1], characterized in that it increases toward .

[3] The light diffusion control laminate has a reflective portion that reflects light and a second light diffusing portion that receives the light reflected by the reflective portion,
The second light diffusing part has a columnar structure in which a plurality of columnar objects with a relatively high refractive index stand in a region with a relatively low refractive index in the thickness direction of the second light diffusing part,
The range of the second incident angle when the angle formed by the normal to the surface of the second light diffusing part and the reflected light on the surface of the second light diffusing part opposite to the front light part is the second incident angle overlaps the range of incident angles in which the emitted light from the second light diffusing section is obtained as diffused light,
The columnar object has an inclined portion that is inclined with respect to the normal to the surface of the second light diffusing portion, and the inclination formed by the normal to the surface of the second light diffusing portion and the inclined portion that is closest to the reflecting portion. The light diffusion control laminate according to [1] or [2], characterized in that the angle is −30° or more and less than 0°.

[4] In the second light diffusing section, the inclination angle formed by the normal to the surface of the second light diffusing section and the inclined section is from the surface of the second light diffusing section on the side of the reflecting section to the surface on the side of the front light section. The light diffusion control layered product according to [3], wherein the light diffusion control layered product increases toward the surface.

[5] The light diffusion control layered product according to [3] or [4], wherein the total thickness of the first light diffusion section and the second light diffusion section is 1 mm or less.

[6] The light diffusion control layered product and the reflector according to [1] or [2], or the light diffusion control layered product according to any one of [3] to [5], and the reflector having the display portion It is a type indicator.

FIG. 1 is a schematic cross-sectional view of a reflective display according to this embodiment. FIG. 2 is a schematic cross-sectional view of a reflective liquid crystal display device as an example of a reflective display. FIG. 3 is a diagram for explaining the configuration and light diffusion characteristics of the light diffusion control laminate according to this embodiment. FIG. 4A is a plan view for explaining the positional relationship between the plate-like region of the louver structure and the front light portion. FIG. 4B is a cross-sectional view taken along line IVB-IVB in FIG. 4A. FIG. 5A is a diagram for explaining the incident light angle dependence and anisotropy in the louver structure. FIG. 5B is a schematic cross-sectional view of the first light diffusing portion for explaining the light diffusing properties of the louver structure. FIG. 6A is a diagram showing an example of a louver structure that a first light diffusion section has; FIG. 6B is a diagram showing an example of a louver structure that the first light diffusion section has. FIG. 6C is a diagram showing an example of a louver structure that the first light diffusion section has. FIG. 7A is a plan view for explaining the positional relationship between the pillars of the column structure and the front light portion. FIG. 7B is a cross-sectional view along line VIIB-VIIB in FIG. 7A. FIG. 8A is a diagram for explaining incident light angle dependence and anisotropy in a column structure. FIG. 8B is a schematic cross-sectional view of a second light diffusing section for explaining the light diffusing properties of the column structure. FIG. 9A is a diagram illustrating an example of a column structure of a second light diffusion section; FIG. 9B is a diagram illustrating an example of a column structure of the second light diffusion section; FIG. 9C is a diagram illustrating an example of a column structure of the second light diffusion section;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

(1. Reflective display)
The reflective display body according to the present embodiment is a display body that can be visually recognized by an observer as display light, which is reflected light obtained by reflecting external light incident inside. Examples of such a reflective display include a reflective liquid crystal display, electronic paper, and digital signage.

Further, the reflective display body according to the present embodiment has a front light section provided on the observer side (front side) with respect to the display body. Since the reflective display has a front light, even when the external light is weak and the display light using the reflected light is dark and difficult to see, the light from the front light is used as the reflected light. The display light can be sufficiently visually recognized.

(1.1. Configuration of Reflective Display)
A reflective display 1 according to this embodiment includes a front light section 20, a light diffusion film 10, a display section 30, and a reflecting section 40, as shown in FIG. A predetermined layer may be formed between each component. In FIG. 1, the X-axis, the Y-axis and the Z-axis are orthogonal to each other, the X-axis and the Y-axis are the axes in the main plane of the light diffusion film 10, and the Z-axis is the main plane of the light diffusion film 10. Let the axis be perpendicular to the plane. In addition, in the Z-axis, the direction toward the observer side is defined as the Z-axis positive direction, and the direction toward the reflector side is defined as the Z-axis negative direction. The same applies to the figures after FIG. 2 .

The light diffusion film 10 has a first light diffusion portion 11 and a second light diffusion portion 12 as described later. The light diffusing film 10 may have a structure in which a first film comprising the first light diffusing portion 11 and a second film comprising the second light diffusing portion 12 are laminated, or may be a single film. The first light diffusing portion 11 and the second light diffusing portion 12 may be formed in the film. In the light diffusion film 10, a member such as a polarizing plate may be arranged between the first light diffusion section 11 and the second light diffusion section 12. The thickness of the light diffusion film 10 is preferably 1 mm or less from the viewpoint of suppressing image blur.

In the present embodiment, as shown in FIG. 1, the light diffusion film 10 has a structure in which a first film made up of the first light diffusion portion 11 and a second film made up of the second light diffusion portion 12 are laminated. have.

The reflecting section 40 is not particularly limited as long as it has a function of reflecting external light and light emitted from the front light toward the viewer (positive direction of the Z-axis in FIG. 1).

When the reflective display 1 according to this embodiment is a reflective liquid crystal display device 100, it has a configuration as shown in FIG. In FIG. 2, the display section 30 is a liquid crystal display section 31 . The liquid crystal display section 31 has a structure in which a liquid crystal layer 32 containing liquid crystal molecules is enclosed between a pair of substrates 33 and 34 . In the liquid crystal layer, an electrode corresponding to each pixel is arranged in order to control the liquid crystal molecules on a pixel-by-pixel basis. This electrode has a mirror-like surface so as to reflect externally incident light. That is, in the reflective liquid crystal display device 100, the electrode 40 arranged in the liquid crystal layer also serves as a reflective portion. Moreover, when performing a color display, you may provide a color filter.

Further, in the reflective liquid crystal display device 100, a predetermined layer is provided between the front light section 20 and members arranged below the front light section 20, such as a light diffusion film, a display section, a reflection section, and the like. 60 may be arranged. Such a layer may be an air layer or a layer filled with resin or the like.

(2. Light diffusion control laminate)
In this embodiment, the front light section 20 and the light diffusion film 10 constitute a light diffusion control laminate 50 . FIG. 3 is a diagram for explaining the configuration and light diffusion characteristics of the light diffusion control laminate 50. As shown in FIG. In FIG. 3, the light diffusion control laminate 50 is shown as a schematic exploded cross-sectional view, and components other than the front light section and the light diffusion film are omitted. In addition, in FIG. 3, the normal lines of the main surfaces of the first light diffusion portion 11, the second light diffusion portion 12, and the reflection portion 40 are the same and parallel to the Z axis.

(2.1. Front light section)
The front light section 20 has a light source section 21 and a light guide section 22 . In the reflective display 1 according to the present embodiment, the light source section 21 is not provided so as to face the reflecting section 40, but is normally provided at the periphery of the display area as shown in FIG. . In this embodiment, the light from the front light section is emitted mainly in the positive direction of the X-axis. Therefore, the emitted light from the front light portion has a small amount of light toward the reflecting portion (the amount of light in the negative direction of the Z axis), and the amount of light that contributes to the display light is small. Therefore, the light emitted from the light source section 21 is guided to the reflecting section 40 by the light guide section 22 . As shown in FIG. 3 , the light emitted from the light source section 21 enters the light guide section 22 , changes its traveling direction while being reflected inside the light guide section 22 , and is guided to the reflection section 40 .

The light guide section 22 is not particularly limited as long as it is configured to guide the light from the light source section 21 to the reflecting section 40 side. For example, unevenness forming a prism may be provided inside, or a reflective material containing particles that reflect light may be applied.

However, in the normal configuration of the light guide section 22, it is difficult for the light emitted from the light guide section 22 to travel toward the reflection section in a state where the incident angle with respect to the normal line of the reflection section 40 is small. Although the traveling direction of the light entering the light guide section 22 from the light source section 21 can be changed to the reflecting section side by the light guide section 22, the direction of the light emitted from the light guide section 22 is different from the normal line of the reflecting section 40. It has a predetermined angle range, and the angle is large. That is, most of the light emitted from the light guide section 22 is normally inclined by 40° or more with respect to the normal line of the reflecting section. Specifically, the amount of light emitted from the light guide section 22 whose angle with respect to the normal to the reflecting section is 40° or more and less than 90° is 70% or more.

The light emitted from the light guide section 22 is positioned closer to the reflection section 40 than the light guide section 22 directly or through a predetermined layer such as an air layer or an optical film such as a polarizing film or a retardation film. The light enters the light diffusion film 10 .

(2.2. Light diffusion film)
In this embodiment, as shown in FIG. 3, in the light diffusion film 10, the first light diffusion portion 11 is arranged on the front light portion 20 side, and the second light diffusion portion 12 is arranged on the reflection portion 40 side. ing.

The light diffusing film according to the present embodiment guides most of the light, such as the light emitted from the light guide section 22, which is incident in a large angle region to the reflecting section, and finally converts it into display light with a wide viewing angle.

Therefore, in order to make the entire display area have a uniform brightness and to enlarge the area visible to the observer (widen the viewing angle), the reflected light reflected by the reflective portion passes through the light diffusion film. It is necessary to have a diffusion region (diffusion region) in the vicinity of the normal line of the light diffusion film, and to obtain a wide angular range in which the diffused light is obtained.

However, when the emitted light from the light guide section 22 is incident on the light diffusion film at a large angle, it is very difficult to achieve the above light diffusion characteristics with a single light diffusion region. Therefore, the light diffusing film is composed of a first light diffusing portion and a second light diffusing portion having different light diffusion characteristics.

(2.3. First light diffusion part)
The first light diffusing section has a role of guiding most of the light incident on the first light diffusing section to the second light diffusing section as diffused light in order to effectively utilize light incident at a large angle. ing.

As shown in FIG. 3, the light emitted from the light guide section 22, that is, the incident light L1 to the first light diffusion section 11 enters the first light diffusion section 11 at a first incident angle θ1in, and the first light The diffused light passes through the diffusion portion 11 and is emitted at a first emission angle θ1out.

In the present embodiment, the first incident angle θ1in is 40° or more and less than 90°, preferably 80° or less.

(2.3.1. Internal structure of the first light diffusion section)
In this embodiment, the first light diffusion section 11 has a louver structure. As shown in FIGS. 4A and 4B, the louver structure has a plate-like region with a relatively high refractive index (high refractive index portion 13) and a plate-like region with a relatively low refractive index (low refractive index portion 14). , are alternately arranged in parallel along the main surface direction of the first light diffusing portions.

In addition, in FIG. 4A, the front light portion is also illustrated in order to show the positional relationship between the front light portion and the plate-like region of the louver structure.

When the front light portion has a rectangular shape, in the first light diffusion portion 11, one side of the plate-like region of the louver structure is arranged parallel to one side of the front light portion on the light source portion arrangement side. preferably. In other words, the first light diffusing portion 11 is arranged such that the plate-like region of the louver structure is inclined toward the front light portion (negative direction of the X-axis) and parallel to the width direction of the front light. (in the Y-axis direction).

As shown in FIGS. 5A and 5B, light L1 incident on the first light diffusion portion 11 at a first incident angle θ1in (40° or more and less than 90°) is diffused by the first light diffusion portion, The light L1′ incident at an angle outside the range of the angle θ1in is transmitted without being diffused by the first light diffusion section. That is, there is an angle-of-incidence dependence on the transmission and diffusion of incident light.

The light diffused by the first light diffusion section and emitted from the surface on the side of the reflection section spreads in a specific direction on a plane parallel to the surface of the first light diffusion section. Specifically, as shown in FIG. 5A, the diffused light spreads in a direction perpendicular to the direction in which the plate-like area extends along the plane of the first light diffusing portion, and a rod-like diffusion area AD is obtained. In other words, an anisotropic diffusion region AD is obtained in the in-plane direction of the first light diffusion portion.

On the other hand, since the light transmitted through the first light diffusing portion and emitted is not diffused, the emitted light does not spread in any direction on the plane parallel to the surface of the first light diffusing portion. Specifically, as shown in FIG. 5A, a dotted transmissive region T is obtained.

As shown in FIG. 5B, if the angle formed by the normal to the surface of the first light diffusing portion 11 and the plate-like region is defined as a first tilt angle φ1, then in this embodiment, the first tilt angle φ1 is usually 15°. 50° or less, preferably 18° or more and 45° or less, and more preferably 23° or more and 40° or less.

Other parameters that define the plate-shaped region are not particularly limited as long as most of the light incident on the first light diffusing section can be guided to the second light diffusing section. preferably.

The difference in refractive index between plate-shaped regions with different refractive indices, that is, the refractive index of the plate-shaped region with a relatively high refractive index (high refractive index portion) and the refractive index of the plate-shaped region with a relatively low refractive index (low refractive index portion) It is preferable that the difference from the refractive index of the index part) is set to a value of 0.01 or more. Although it is preferable that the difference between the refractive index of the high refractive index portion and the refractive index of the low refractive index portion is large, the upper limit is considered to be about 0.3 from the viewpoint of selecting a material capable of forming a louver structure.

Also, the refractive index of the high refractive index portion is preferably a value within the range of 1.5 to 1.7. On the other hand, the refractive index of the low refractive index portion is preferably a value within the range of 1.4 to 1.5.

The width S1 of the high refractive index portion and the width S2 of the low refractive index portion are each preferably a value within the range of 0.1 to 15 μm, more preferably 0.5 to 10 μm, and 1 to 5 μm. It is particularly preferred to have In addition, the thickness of the louver structure (the length of the high refractive index portion and the low refractive index portion in the direction normal to the film surface) is preferably a value within the range of 5 to 495 μm, and is 30 to 300 μm. is more preferable, and 50 to 150 μm is particularly preferable.

In addition, it is preferable that the louver structure forming the first light diffusing section changes the inclination angle of the plate-like region from the viewpoint of further diffusing the incident light from the front light section. Furthermore, it is more preferable to change the tilt angle so that the tilt angle after the change increases toward the reflecting portion (in the negative direction of the Z-axis). Examples of the louver structure in which the inclination angle changes include a structure having a bent portion in the middle of the thickness direction of the louver structure, or a structure having an overlapping structure in which the louver structures are overlapped.

As shown in FIG. 6A, the louver structure having a bent portion means that the high refractive index portion 13 and the low refractive index portion 14 are continuous in the thickness direction without discontinuity, and the inclination angle is between the upper side and the lower side of the bent portion. It means something that is changing.

Further, the louver structure having an overlapping structure means that, as shown in FIG. 6B, a louver structure having a different inclination angle is formed in the middle of the first light diffusion part 11 in the thickness direction, and the louver structure on the upper side in the thickness direction is formed. The lower end and the upper end of the louver structure on the lower side in the thickness direction form an intricate overlapping structure.

When using the first light diffusing part composed of a louver structure having a bent part or overlapping structure, the inclination angle of the upper side (front light part side) of the louver structure is the same as the above-described louver structure without such a structure. is preferably That is, the upper tilt angle preferably satisfies the range of φ1.

On the other hand, the inclination angle of the lower side of the louver structure having such a structure is preferably larger than the upper inclination angle (φ1) by 1° or more, more preferably by 3° or more, and more preferably by 5° or more. is particularly preferred. Thereby, light diffusion can be spread more.

The angle of inclination of the lower side of the louver structure having such a structure is preferably 20° or less, more preferably 10° or less, and 8° or less from the angle of inclination of the upper side. It is particularly preferred to have As a result, diffused light overlaps between the upper louver structure and the lower louver structure, so that diffused light with a greater amount of light can be guided to the second light diffusion section.

Furthermore, a louver structure with bends and a louver structure with overlapping structures may be combined. Such a structure is exemplified by the louver structure shown in FIG. 6C. In FIG. 6C, the lower end of the louver structure on the upper side in the thickness direction and the upper end of the louver structure on the lower side in the thickness direction are intertwined with each other, and the louver structure on the lower side in the thickness direction has a bent portion. .

(2.3.2. Light Diffusion Characteristics of First Light Diffusion Portion)
In the present embodiment, by setting the first tilt angle φ1 within the above range, if the first incident angle θ1in of incident light to the first light diffusing section is within the above range, the light from the first light diffusing section Emitted light is obtained as diffused light. Moreover, the output angle (first output angle: θ1out) of the diffused light can be easily set to, for example, 25° or more and less than 90°, and more preferably 30° or more and 80° or less.

Further, by constructing the first light diffusing portion with a louver structure and setting the first inclination angle φ1 within the above range, the light emitted from the front light portion can be guided to the reflecting portion as diffused light. .

(2.4. Second light diffusion section)
The second light diffusion section has a role of emitting the reflected light guided to the surface of the second light diffusion section opposite to the front light section as isotropic diffused light from the surface on the front light section side. . Moreover, this isotropic diffused light has a diffusion region near the normal line of the light diffusion film, and the width of the diffusion region is wide.

As shown in FIG. 3, the reflected light Lr specularly reflected by the reflecting portion is incident on the surface of the second light diffusing portion 12 on the reflecting portion side at a second incident angle θ2in. The incident light is diffused by the second light diffusing portion 12 and emitted from the surface of the second light diffusing portion 12 on the front light portion side at the second emission angle θ2out.

(2.4.1. Internal structure of the second light diffusion section)
In this embodiment, the second light diffusion section 12 has a column structure. As shown in FIGS. 7A and 7B, the column structure has a plurality of pillars 16 with a relatively high refractive index standing in a region 17 with a relatively low refractive index in the thickness direction of the second light diffusion section. It is a structure that becomes

In addition, in FIG. 7A, the front light part is also illustrated in order to show the positional relationship between the front light part and the pillars of the column structure.

When the front light portion has a rectangular shape, in the second light diffusing portion 12, the pillars of the column structure stand in parallel with one side of the front light portion on the side where the light source portion is arranged, and are perpendicular to the one side. It is preferably arranged obliquely in the direction. In other words, the second light diffusing portion 12 is arranged so that the columnar structure of the column structure is inclined in the direction away from the front light portion (positive direction of the X axis) and parallel to the width direction of the front light. It is preferably arranged (in the Y-axis direction).

Since the second light diffusing portion 12 has a column structure, the reflected light Lr is diffused in the second light diffusing portion and is incident at an angle other than the range of the second incident angle, as shown in FIGS. 8A and 8B. The light Lr' passes through the second light diffusion portion without being diffused much. That is, there is an angle-of-incidence dependence on the transmission and diffusion of incident light.

The light emitted from the front light portion side surface of the second light diffusion portion spreads isotropically in a plane parallel to the surface of the second light diffusion portion. Specifically, as shown in FIG. 8A, a circular isotropic diffusion region ID is obtained in a plane parallel to the plane of the second light diffusion portion.

However, since the incident angle dependence of the column structure is weaker than the incident angle dependence of the louver structure, even if the light is incident in an incident angle range in which isotropic diffusion regions ID cannot be obtained, the second light Slightly diffused by the diffuser. In such a case, a crescent-shaped transmission region T in which the emitted light is diffused in a specific direction is obtained instead of the dot-shaped transmission region T as shown in FIG. 4A.

In addition, in FIG. 8A, the upper side is the reflecting section side, and the lower side is the front light section side.

As shown in FIG. 8B, it is preferable that the inclination direction of the columnar object is opposite to the inclination direction of the plate-like region that constitutes the louver structure of the first light diffusing section 11 . In the present embodiment, when the angle formed by the normal to the surface of the second light diffusing portion 12 and the columnar object is the second tilt angle φ2, the second tilt angle φ2 is preferably −30° or more and less than 0°. , −20° or more and −1° or less, and particularly preferably −10° or more and −3° or less. This makes it easy to isotropically diffuse the reflected light from the reflecting section without diffusing the emitted light from the first light diffusing section 11 by the second light diffusing section 12 .

Other parameters that define the columnar object are not particularly limited as long as the reflected light can be diffused by satisfying the second tilt angle φ2, but the following is preferable, for example.

It is preferable that the difference between the refractive index of the columnar object 16 having a relatively high refractive index and the refractive index of the area (medium object 17) having a relatively low refractive index be 0.01 or more. It is preferable that the difference between the refractive index of the columnar object and the refractive index of the medium is as large as possible.

Also, the maximum diameter of the columnar article in cross section is preferably 0.1 to 15 μm, more preferably 0.5 to 10 μm, and particularly preferably 1 to 5 μm. Although the cross-sectional shape of the columnar object is not particularly limited, it is preferably circular, elliptical, polygonal, odd-shaped, or the like, for example.

In addition, the length (thickness) of the pillars in the direction normal to the film is preferably in the range of 5 to 495 μm, more preferably in the range of 50 to 350 μm, and more preferably in the range of 100 to 250 μm. Values within the range are particularly preferred. In addition, the column structure does not have to be formed to reach both main surfaces in the film thickness direction of the second light diffusing section.

In addition, the distance between the pillars, that is, the space P between adjacent pillars is preferably 0.1 to 15 μm, more preferably 0.5 to 10 μm, particularly preferably 1 to 5 μm. .

In addition, in the column structure forming the second light diffusing section, it is preferable to change the inclination angle of the columnar structure from the viewpoint of diffusing the reflected light from the reflecting section over a wider range. Furthermore, it is more preferable to change the tilt angle so that the changed tilt angle increases toward the front light portion (in the positive direction of the Z-axis). Examples of the column structure in which the inclination angle changes include a structure having a bending portion in the middle of the thickness direction of the columns of the column structure, or a structure having an overlapping structure in which the columns overlap.

A column structure having a bend means a structure in which the columns 16 are continuous in the thickness direction without discontinuity and the inclination angle changes between the upper and lower sides of the bend, as shown in FIG. 9A.

9B, a column structure having an overlapping structure is formed by forming a column structure with a different inclination angle in the middle of the thickness direction of the second light diffusing part 12, and forming a columnar structure on the upper side in the thickness direction. The lower end and the upper end of the pillar on the lower side in the thickness direction form an intricate overlapping structure.

In the case of using the second light diffusion section composed of a column structure having a bent portion or an overlapping structure, the inclination angle of the lower side (reflecting portion side) of the column structure is the same as the above-described column structure without such a structure. is preferably That is, it is preferable that the tilt angle of the lower side satisfies the range of φ2.

On the other hand, the tilt angle of the upper side (front light portion side) of the column structure having such a structure is preferably 1° or more, more preferably 2° or more, than the tilt angle (φ2) of the lower side. , is more preferably greater than 3°. The angle of inclination of the upper side is preferably increased by 30° or less from the angle of inclination of the lower side, more preferably 20° or less, and particularly preferably 10° or less.

Furthermore, a column structure having bends and a column structure having overlapping structures may be combined. Such a structure is exemplified by the column structure shown in FIG. 9C. In FIG. 9C, the lower end of the column structure on the upper side in the thickness direction and the upper end of the column structure on the lower side in the thickness direction are intertwined with each other, and the column structure on the lower side in the thickness direction has a bent portion. .

(2.4.2. Light Diffusion Characteristics of Second Light Diffusion Portion)
In the present embodiment, by setting the second tilt angle φ2 within the above range, isotropic diffused light can be obtained in the second light diffusion section within the range of the second incident angle θ2in of the reflected light on the second light diffusion section. can be overlapped with the range of incident angles that As a result, it becomes easy to set the output angle (second output angle: θ2out) of the diffused light to, for example, −90° or more and 45° or less. Therefore, a wide viewing angle can be achieved in the vicinity of the normal to the second light diffusing portion.

(3. Manufacturing method of light diffusion film)
The light diffusion film described above is manufactured by a known method. A method for producing the light diffusion film will be briefly described below. First, a composition for a light diffusion film is prepared. This composition for a light diffusion film contains at least two polymerizable compounds having different refractive indices and a photopolymerization initiator. Depending on the structure of the louver structure and column structure to be formed, the composition for a light diffusion film may contain an ultraviolet absorber.

Subsequently, the composition for a light diffusion film is applied to a given sheet by a given method to form a coating layer. The formed coating layer is irradiated with an energy beam to form a louver structure and a column structure. By controlling the energy beam irradiation method and irradiation conditions, it is possible to form the plate-like regions that form the louver structure and the pillars that form the column structure. Furthermore, plate-like regions and pillars having bends can also be formed. Through such steps, the light diffusion film described above can be manufactured.

A detailed description of the method for producing the light diffusion film is not described in the present embodiment, but is disclosed in, for example, Japanese Patent Application Laid-Open No. 2012-141593, International Publication No. 2013/108539, and International Publication No. 2014/156421. You can use the existing content.

Further, the light diffusion control layered product according to the present embodiment is obtained by bonding the light diffusion film produced above and the front light section via a transparent adhesive or the like. The predetermined layer described above may be formed between the light diffusion film and the front light section.

Furthermore, the reflective display body according to the present embodiment is obtained by bonding the light diffusion control layered body, the display section, and the reflective section via a transparent adhesive or the like.

(4. Effects of this embodiment)
In this embodiment, the light diffusion film is composed of a first light diffusion section having a louver structure and a second light diffusion section having a column structure, and light from the front light section is diffused by the first light diffusion section. I'm trying The first light diffusing portion, on which the light from the front light portion is incident at a large angle, becomes diffused light including a region where the emission angle of the emitted light is smaller than the incident angle of the light from the front light portion. That is, the inclination angle of the plate-like region is controlled so that the light can be sufficiently guided to the reflecting portion. Since the first light diffusion section has such a configuration, most of the light from the front light can be guided to the second light diffusion section.

In the second light diffusing portion, the inclination direction of the pillars forming the column structure is opposite to the inclination direction of the plate-like regions forming the louver structure. That is, the inclination angle of the plate-like region is positive, but the inclination angle of the columnar object is negative. As a result, the light emitted from the front light portion becomes reflected light, and the light emitted from the surface of the second light diffusion portion on the front light portion side can be isotropic diffused light.

By making the inclination direction of the columnar object and the inclination direction of the plate-shaped area opposite to each other, the light emitted from the first light diffusion section enters outside the diffusion area of the second light diffusion section. When the light emitted from the diffusing section is emitted from the second light diffusing section, the light is transmitted with some light diffusion as shown in FIG. 8A. The light emitted from the second light diffusing section is specularly reflected by the reflecting section, becomes reflected light, and enters the second light diffusing section again.

Since the reflected light enters the diffusion region of the second light diffusion section, isotropic diffused light is obtained when the reflected light is emitted from the second light diffusion section, as shown in FIG. 8A.

Although this isotropic diffused light again enters the first light diffusing section, it enters outside the diffusion region of the first light diffusing section. Penetrates and faces the observer.

Therefore, the light diffusion film having the first light diffusion section and the second light diffusion section diverts most of the light from the front light to near the front of the reflective display (near the normal line of the light diffusion film) or below it. It can be used as reflected light diffusely emitted (in the direction opposite to the light source section). As a result, the display light can be made brighter, and the visible angle (viewing angle) can be widened.

In addition, the light from the front light section is utilized by making the first light diffusion section, which is used to guide the light from the front light section to the reflecting section side, a louver structure having a predetermined tilt direction and tilt angle. If the outside light is used instead, the outside light is transmitted without being diffused, so that the outside light can be isotropically diffused by the second light diffusing portion. In addition, when the first light diffusing part has a column structure, the emitted light (isotropic diffused light) from the second light diffusing part is slightly diffused to form a crescent-shaped diffused light as shown in FIG. 8A. This is not desirable.

Therefore, the reflective display including the light diffusion control layered body having the above-described configuration can effectively utilize sunlight and indoor light from a large angle range even in bright daytime hours when the front light is not used. Therefore, even if the reflective display member is in a state nearly perpendicular to the top surface, sufficient reflected light can be obtained and a clear image can be visually recognized.

By the way, when a reflective display is used as a display unit of a smartphone, an outdoor television, etc., even if the viewing angle is narrow, the display unit can be adjusted to an angle at which an observer can easily see the display light. Narrowness is not fatal.

On the other hand, when a reflective display is used for digital signage, the display is fixed and it is difficult for the observer to adjust the viewing angle. Furthermore, in signage applications, it is necessary for a large number of people to view the displayed content, and a wide viewing angle is essential.

Therefore, the reflective display body according to the present embodiment is suitable not only for a reflective liquid crystal display device, electronic paper, etc., but also as a display section for signage applications. By using the reflective display body according to this embodiment, the visibility of the display light is good regardless of whether the external light is used or the front light is turned on.

Although the embodiments of the present invention have been described above, the present invention is by no means limited to the above embodiments, and may be modified in various ways within the scope of the present invention.

EXAMPLES The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

(Experimental example 1)
[Brightness evaluation of reflected light in the front direction]
Light from a fluorescent lamp light source is made incident at an incident angle of 50° on the light diffusion film produced in each example described later from the inclined direction of the louver structure of the first light diffusion part, and the front direction of the sample (light diffusion The normal direction of the film) was photographed, and the brightness of the sample in the front direction was measured with a brightness meter (manufactured by Konica Minolta, trade name "LS-110"). The incident angle of incident light was calculated from the distance relationship between the position of the fluorescent light source and the sample. The light diffusing film of Comparative Example 1, which does not have the louver structure of the first light diffusing portion, was arranged so that the arrangement of the column structure was the same as in Example 1, and the measurement was performed. In addition, since the light diffusion film of Comparative Example 2 does not have a louver structure and a column structure, light was similarly incident from an arbitrary direction at an incident angle of 50° and measured in the same manner. The results are shown in Table 1.

[Evaluation of image blur]
A sample of a reflective display obtained in each example described later was set on an optical microscope, and blurring of an image when light was incident from various directions in a dark place was observed and compared for each sample. A case where no blurring of the image was observed when light was incident from any direction was rated as ◯, and a case where blurring was observed when light was incident from at least one direction was rated as x. Results are shown in Table 1.

[Example 1]
A 100 μm thick OHP sheet with 4-point printing was attached to the aluminum deposition surface of a JDSU mirror (BV2, 1.1 mm thick) via a transparent adhesive so that the printed surface faces the sheet. , to prepare a printed layer. That is, the printed layer was composed of an OHP sheet and an adhesive layer, and the total thickness, that is, the distance from the mirror surface to the surface in contact with the second light diffusion portion was 200 μm.

A light diffusion film (second light diffusion portion) having a thickness of 200 μm and having a column structure shown in FIG. 9C was laminated on the printed layer via a transparent adhesive having a thickness of 25 μm. Furthermore, on the light diffusion film having a column structure, a light diffusion film having a thickness of 130 μm and having a louver structure (first light diffusion film) shown in FIG. Part) was laminated via a transparent adhesive having a thickness of 25 μm to obtain a sample of the reflective display body according to Example 1.

Here, the cross-sectional shapes of the light diffusion film having the column structure and the light diffusion film having the louver structure were observed with an optical microscope. As a result, the light diffusion film having the column structure had a cross-sectional shape as shown in FIG. 9C, and columnar objects were present even in the vicinity of both surfaces. The tilt angle of the portion closest to the mirror (reflector) was −6.4°, and the tilt angle of the portion closest to the light source (front light) was 0°.

On the other hand, the light diffusion film having the louver structure had the cross-sectional shape shown in FIG. 4B, plate-like regions were formed near both surfaces, and the inclination angle was 25°.

Also, the maximum diameter of the pillars in the column structure and the space were both 1.5 μm. Both the width and space of the plate-like region in the louver structure were 1.5 μm. The above evaluation was performed on the obtained reflective display. Table 1 shows the results.

[Example 2]
The light diffusion film (first light diffusion portion) having a louver structure of Example 1 was changed to a light diffusion film having a louver structure having a cross-sectional shape shown in FIG. 4B, a thickness of 130 μm, and an inclination angle of 45°. A sample of the reflective display body according to Example 2 was produced in the same manner as in Example 1, except for the above. The above evaluation was performed on the obtained reflective display. Table 1 shows the results.

[Example 3]
In the same manner as in Example 1, except that the light diffusion film (first light diffusion portion) having a louver structure of Example 1 was changed to a light diffusion film having a thickness of 150 μm and having a louver structure shown in FIG. 6A. , a sample of a reflective display according to Example 3 was produced. The light diffusion film having the louver structure had an inclination angle of 25° on the light source (front light) side and an inclination angle of 32° on the mirror (reflector) side. The above evaluation was performed on the obtained reflective display. Table 1 shows the results.

[Comparative Example 1]
A sample of a reflective display member according to Comparative Example 1 was produced in the same manner as in Example 1, except that the light diffusion film (first light diffusion portion) having the louver structure of Example 1 was not formed. The above evaluation was performed on the obtained reflective display. Table 1 shows the results.

[Comparative Example 2]
100 parts by mass of an acrylic pressure-sensitive adhesive and 4 parts by mass of styrene particles with an average particle size of 4.5 μm are diluted with ethyl acetate, mixed well with stirring, and then coated and dried on a release sheet to form a light diffusion layer with a thickness of 200 μm. A light diffusion film having an adhesive layer was produced.

A reflective display was produced in the same manner as in Example 1 except that the release sheet of the light diffusion film was removed and a light diffusion film having a first light diffusion portion and a second light diffusion portion was used instead. was evaluated. Table 1 shows the results.

From Table 1, it was confirmed that the displayed image was dark when the light diffusion film did not have the first light diffusion portion and when the fine particle diffusion system light diffusion film was used. It was also confirmed that the light diffusion film having the first light diffusion portion and the second light diffusion portion is more excellent in preventing blurring of images than the fine particle diffusion type light diffusion film.

REFERENCE SIGNS LIST 1 reflective display 10 light diffusion film 11 first light diffusion part 12 second light diffusion part 20 front light part 30 display part 40 reflection part 50 light diffusion control laminate

Claims (6)

A front light section including a layered light guide section and a light source section disposed on the periphery of the light guide section ; and a layered first light diffusion section into which light emitted from the front light section is incident. ,
The light guide section and the first light diffusion section are laminated such that the normals of the main surfaces of the light guide section and the first light diffusion section are aligned,
The first light diffusing part has a plate-like region with a relatively high refractive index along an arbitrary direction along the main surface of the first light diffusing part in the region with a relatively low refractive index. It has a louver structure that is alternately arranged in parallel,
The range of the first incident angle is 40° or more and less than 90° when the angle formed by the normal to the surface of the first light diffusion portion and the incident light to the first light diffusion portion is defined as the first incident angle. and
The range of incident angles in which the emitted light from the first light diffusion part is obtained as diffused light includes the range of the first incident angles,
The plate-shaped region is inclined toward the light source unit with respect to a normal line to the surface of the first light diffusion unit , and the normal line to the surface of the first light diffusion unit and the front light unit A light diffusion control layered product, wherein the first inclination angle is 15° or more and 50° or less, where the angle formed by the plate-like region closest to is defined as a first inclination angle. In the first light diffusing portion, the inclination angle formed by the normal to the surface of the first light diffusing portion and the plate-like region is on the opposite side of the front light portion side surface of the first light diffusing portion. 2. The light diffusion control layered product according to claim 1, wherein the light diffusion control layered product increases toward the surface of . The light diffusion control laminate has a layered reflecting portion that reflects light, and a layered second light diffusion portion that receives the light reflected by the reflecting portion ,
The light guiding section, the first light diffusing section, the second light diffusing section, and the reflecting section are laminated such that the normals of the main surfaces thereof are aligned,
The second light diffusing part has a column structure in which a plurality of columnar objects with a relatively high refractive index stand in a region with a relatively low refractive index in the thickness direction of the second light diffusing part. death,
When the angle formed by the normal to the surface of the second light diffusing section and the reflected light toward the surface of the second light diffusing section opposite to the front light section is defined as a second incident angle, the second the range of incident angles overlaps with the range of incident angles in which the emitted light from the second light diffusing section is obtained as diffused light;
The columnar object has an inclined portion that is inclined with respect to a normal to the surface of the second light diffusing portion, and the inclined portion that is closest to the normal to the surface of the second light diffusing portion and the reflecting portion. 3. The light diffusion control layered product according to claim 1, wherein the inclination angle between the two is -30° or more and less than 0°. In the second light diffusing portion, the inclination angle formed by the normal to the surface of the second light diffusing portion and the inclined portion is such that the surface of the second light diffusing portion on the side of the reflecting portion is closer to the front light portion. 4. The light diffusion control layered product according to claim 3, which increases toward the surface of the . 5. The light diffusion control layered product according to claim 3, wherein the total thickness of said first light diffusion portion and said second light diffusion portion is 1 mm or less. A reflective display body comprising the light diffusion control layered product according to claim 1 or 2 and a reflective portion, or the light diffusion control layered product according to any one of claims 3 to 5, and a display portion.

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