JPWO2020066312A1 - A light guide laminate using an anisotropic optical film and a planar illumination device for display devices using the light guide laminate. - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a light source when the surrounding environment is dark and to have the same emission characteristics (diffusivity) as when the light guide plate alone is used, and when the surrounding environment is bright, the light source is not used. Also, a light source laminate having sufficiently bright (high visibility) characteristics and a planar illumination device for a display device using the same. A light guide laminate including a light guide plate and at least one anisotropic optical film, wherein the light guide plate has an incident surface that allows light to enter the inside of the light guide plate and the incident surface. The anisotropic optical film has an exit surface in which light incident from is reflected and refracted in the light guide plate and is emitted, and the anisotropic optical film has an angle at which light is incident on the anisotropic optical film. A film having a variable linear transmittance, which is the amount of incident light transmitted in the linear direction / the amount of incident light transmitted, and the anisotropic optical film is laminated directly on the exit surface or via another layer. The anisotropic optical film includes a matrix region and a structural region including a plurality of structures, and the light emitted in the direction in which the emission intensity of the light from the emission surface is maximized is the light emitted from the emission surface. A light guide laminate characterized in that the linear transmittance of the anisotropic optical film when incident on the anisotropic optical film is more than 30%. [Selection diagram] Fig. 1

Description

The present invention relates to a light guide laminate using an anisotropic optical film used in a transmission type display device, a reflection type display device, and the like, and a planar light source illumination device for a display device using the light guide laminate.

In recent years, there is a strong demand for a display device having a built-in lighting device to be thin, lightweight, and have low power consumption. As such a display device, a type provided with a light guide plate for making the illumination light from the light source uniform in the brightness and the irradiation direction in the display panel surface is becoming widespread.

Among the display device lighting devices in which the light source and the light guide plate are combined, the display device lighting device in which the light source is provided on the end face portion of the display panel (including the light guide plate) and is used as the illumination light of the display panel is an edge type. It is called the light method, and it is easy to make it thinner and lighter. Further, even if the number of light sources is reduced for the purpose of reducing power consumption, there is an advantage that the dark part between the light sources does not become a dark part in the display surface of the display panel. The edge type light system having such an advantage is often used as a lighting device for a display device of a liquid crystal display device.

Further, the edge type light method includes an edge type front light and an edge type backlight. In the edge type front light, the light guide plate is arranged on the visible side of the display panel, and in the edge type backlight, the light guide plate is arranged on the back side of the display panel (opposite to the visible side of the display panel). ing.

An edge-type light type lighting device for a display device has a light source such as an LED on the end surface of a light guide plate made of transparent acrylic resin or the like, and a surface opposite to the light emitting surface (the surface facing the display panel) of the light guide plate. A light reflecting film is provided on the (light deflecting surface), and a light diffusing film and a condensing film are provided on the emitting surface. The light incident on the end surface of the light guide plate and propagating in the light guide plate is taken out from the light emitting surface by changing the propagation direction of the light by the light deflection element formed on the light deflection surface.

The light deflection element includes a method of printing white ink in dots (Patent Document 1), a method of forming a microlens by an inkjet method (Patent Document 2), and a method of forming a dent by a laser ablation method (Patent Document 1). It is known that it is formed by Document 3), a method of forming irregularities using a mold (Patent Document 4), and the like.

The light incident on the inside of the light guide plate from the linear light source is (1) light emitted directly from the emitting surface, (2) reflected by the light deflecting element, and reflected by (3) the light deflecting element. Instead, the light is reflected by the light-reflecting film, returns to the light guide plate, and then emits light from the exit surface. Of these, the lights (2) and (3) are diffusely reflected and cause uneven brightness of the display panel.

A light diffusion film is provided for the purpose of alleviating the uneven brightness by scattering and diffusing light and making the illuminance of light on the surface of the display panel uniform. Further, in order to improve the front luminance in the normal direction (front direction of the display panel) of the surface of the light guide plate, a condensing sheet is used. The light collecting sheet is a transparent sheet in which a large number of prism structures, wave structures, pyramid structures and other concavo-convex structures are formed on the surface, and one layer or two layers are used.

A method of laminating a light diffusing film on the surface of a light guide plate has been proposed in order to improve the brightness of an edge-type light type lighting device for a display device and reduce the size and weight (Patent Document 5).

Further, in a reflective display device, a light diffusing film is generally used for expanding the viewing angle.

Japanese Unexamined Patent Publication No. 1-241590 Japanese Unexamined Patent Publication No. 2013-185040 International 2015/178391 Japanese Unexamined Patent Publication No. 5-210014 Japanese Unexamined Patent Publication No. 8-227273

For example, when an edge type front light is used as a surface lighting device for a display device in order to ensure visibility in a dark place for a reflective display device, it is generally used for a reflective display device. There is a problem that the isotropic light diffusing film changes the original emission characteristics of the light guide plate.

The present invention has been made in view of the above circumstances, and an object of the present invention is to combine a light source plate having specific optical characteristics and an anisotropic optical film having specific optical characteristics (1). When the surrounding environment is dark, the light source is used to have the same emission characteristics (diffusivity) as when the light guide plate is used alone. It is an object of the present invention to provide a light guide laminate having sufficiently bright (high visibility) characteristics.

As a result of diligent studies by the present inventors on the above-mentioned problems, a light guide plate having an incident surface and an exit surface and a linear transmittance of more than 30% when light in the direction of maximum emission intensity is incident. The present invention has been completed by discovering that a light guide laminate obtained by laminating the anisotropic optical film, which is the above-mentioned, directly or through another layer, solves the above-mentioned problems.
That is,
The present invention (1)
A light guide laminate including a light guide plate and at least one anisotropic optical film.
The light guide plate has an incident surface that allows light to enter the inside of the light guide plate, and
The light incident from the incident surface has an exit surface that is reflected and refracted in the light guide plate and emitted.
The anisotropic optical film is a film in which the linear transmittance, which is the amount of transmitted light in the linear direction of the incident light / the amount of incident light, changes depending on the angle at which the light is incident on the anisotropic optical film.
The anisotropic optical film is laminated on the exit surface directly or via another layer.
The anisotropic optical film includes a matrix region and a structural region including a plurality of structures.
The linear transmittance of the anisotropic optical film when the light emitted from the exit surface in the direction in which the emission intensity of the light is maximized is incident on the anisotropic optical film is more than 30%. It is a light guide laminate as a feature.
The present invention (2)
The light guide laminate according to the invention (1), characterized in that the angle formed by the direction of the scattering center axis of the plurality of structures and the direction of maximizing the emission intensity of the light is more than 20 °. ..
The present invention (3)
The invention (1) or (2), characterized in that the angle formed by the direction in which the emission intensity of the light emitted from the emission surface is maximized and the normal direction of the emission surface is less than 20 °. It is a light guide laminate.
The present invention (4)
The invention (1), wherein the light deflection surface, which is a surface opposite to the exit surface, has a plurality of concave light deflection elements having a size of 50 μm or less and a depth of 50 μm or less. The light guide laminate according to (3).
The present invention (5)
The invention (1), characterized in that a plurality of convex light deflection elements having a size of 50 μm or less and a height of 50 μm or less are provided on a light deflection surface which is a surface opposite to the emission surface. The light guide laminate according to (3).
The present invention (6)
The light guide laminate according to the inventions (1) to (5), wherein the other layer contains at least one of a polarizing plate and a retardation plate.
The present invention (7)
A planar illumination device for a display device, which comprises the light guide laminate according to any one of the inventions (1) to (6) and a light source.

According to the present invention, when the ambient environment is dark, the light source is used, and the light source has the same emission characteristics (diffusivity) as when the light guide plate is used alone. When the ambient environment is bright, the light source is not used. Even so, it is possible to provide a light source laminate having sufficiently bright (high visibility) characteristics and a planar illumination device for a display device using the light source laminate.

It is sectional drawing which shows the structural example of the light guide laminated body which concerns on this invention. It is a schematic diagram which shows the progress of light in a light guide plate. It is an enlarged view which shows the surface structure of a light guide plate. It is the top view and the cross-sectional view which illustrated the shape of the concave dot structure. It is a schematic diagram which shows the distribution example of the dot structure in a light guide plate. It is a schematic diagram which shows an example of the structure of the anisotropic optical film which has each of a plurality of structures of a pillar structure and a louver structure, and the state of the transmitted light incident on these anisotropic optical films. It is explanatory drawing which shows the evaluation method of the light diffusivity of an anisotropic optical film. 6 is a graph showing the relationship between the incident light angle of the pillar structure and the louver structure shown in FIG. 6 on the anisotropic optical film and the linear transmittance. It is a graph (optical profile) for explaining a diffusion region and a non-diffusion region in an anisotropic optical film. It is a three-dimensional polar coordinate display for explaining the scattering center axis in an anisotropic optical film.

1. 1. Definitions of main terms In the present specification, the expression "the angle between the direction in which the emission intensity of light emitted from the emission surface is maximized and the normal direction of the emission surface" is used without any notice. It may be expressed as "the angle at which the emission intensity is maximized".

Further, in the present specification, the expressions "a plurality of structures contained in an anisotropic optical film" and "a structural region including a plurality of structures contained in an anisotropic optical film" are not allowed. Instead, it may be expressed as "plurality of structures" or "structural area".

The "linear transmittance" generally refers to the linear transmittance of light incident on an anisotropic optical film, and refers to the amount of transmitted light in the linear direction of the incident light when the light is incident from a certain incident light angle. It is the ratio of the incident light to the amount of light, and is expressed by the following formula.
Linear transmittance (%) = (Linear transmitted light amount / Incident light amount) × 100

The "pillar structure" refers to an anisotropic optical film having an aspect ratio of 1 or more and less than 2 which is the ratio of the major axis (major axis) and the minor axis (minor axis) of the cross-sectional shapes of a plurality of structures. show. The cross-sectional shape is a cross-sectional shape of the plurality of structures on a plane orthogonal to the orientation direction of the plurality of structures.
In the present invention, when the cross-sectional shape has a major axis (major axis) and a minor axis (minor axis), the major axis / minor axis is set as the aspect ratio, and the cross-sectional shape is substantially circular, and the major axis and the minor axis are significantly significant. If the above cannot be specified, both the major axis and the minor axis shall correspond to the diameter of the circle, and the aspect in this case shall be 1.

The "louver structure" refers to an anisotropic optical film having an aspect ratio of 2 or more, which is the ratio of the major axis (major axis) and the minor axis (minor axis) of the cross-sectional shapes of a plurality of structures. The cross-sectional shape is the same as in the case of the "pillar structure".

2. Light guide laminate 2-1. Structure of Light Guide Laminated Body The light guide laminated body according to the present invention includes a light guide plate and at least one anisotropic optical film. In order to adjust the optical characteristics of the light guide laminate, a plurality of anisotropic optical films having different light diffusivity can be used in combination.

The anisotropic optical film is laminated directly or via another layer on the exit surface of the light guide plate described later.

The other layers are not particularly limited as long as the effects of the present invention are not impaired. Examples of the other layer include an adhesive layer for joining the light guide plate and the anisotropic optical film, a polarizing plate, a retardation plate, and the like, and they can be used alone or in combination of two or more. .. Structural examples of the light guide laminate are shown in FIGS. 1 (a) to 1 (e). Although not shown, the pressure-sensitive adhesive layer can be laminated between the layers.

The material and thickness of the pressure-sensitive adhesive layer are not particularly limited as long as the effects of the present invention are not impaired. It suffices if the light guide plate 2 and the anisotropic optical film 3 can be fixed, and one suitable for the adherend such as the light guide plate can be selected. Further, the pressure-sensitive adhesive layer may be an adhesive.

The polarizing plate 4 is a plate that allows the emitted light emitted from the light guide plate 2 to pass only the light polarized or polarized in a specific direction. For example, the liquid crystal display device using the light guide laminate according to the present invention. It is used when it is used as a plane lighting device. The polarizing plate 4 used in the present invention is not particularly limited and can be selected according to the desired optical characteristics of the light guide laminate 1.

The retardation plate 5 is a material used for optical compensation of a liquid crystal display, for example, and prevents the occurrence of viewing angle dependence such as optical distortion due to birefringence and display coloring caused by modulation in the viewing angle direction. It is used for the purpose of The retardation plate 5 used in the present invention is not particularly limited and can be selected according to the desired optical characteristics of the light guide laminate 1.

Further, a sealing layer 6, a reflection plate, or the like can be laminated on the light deflection surface 25 which is the surface opposite to the emission surface of the light guide plate 2.

The sealing layer 6 seals, for example, the light deflecting element 22 on the surface of the light deflecting surface. The sealing layer 6 can prevent the optical characteristics of the light guide laminate 1 from being deteriorated due to damage to the light deflection element 22 or adhesion of dust or the like.

2-1-1. Light guide plate 2-1-1-1. Structure of light guide plate The light guide plate according to the present invention has one or more incident surfaces that allow light emitted from at least one light source to enter the inside of the light guide plate. Further, the incident light propagates in the light guide plate and has at least one exit surface emitted from the light guide plate. In the case of the edge type light system, the incident surface is the end surface of the light guide plate.

The number of incident surfaces is not limited to one, and a plurality of incident surfaces may be provided, and a plurality of light sources can be arranged for the purpose of increasing the emission intensity of the light guide plate.

The light guide plate and the light source may be arranged adjacent to each other or may be arranged at intervals. From the viewpoint that the light emitted from the light source is not easily attenuated and the display device is miniaturized, it is preferable that the light source and the light guide plate are arranged adjacent to each other.

Further, the light emitted from the light source may be directly incident on the light guide plate, or may be indirectly incident on the light guide plate or the like through a mirror or a light guide material.

The light guide plate reflects light incident from a light source inside the light guide plate and emits light outside the light guide plate, and light propagating inside the light guide plate is reflected and refracted in the direction of the light emitting surface and is reflected from the exit surface. It has a light deflecting element for emitting light. The light propagating inside the light guide plate is reflected and refracted in the direction of the exit surface by the light deflection element, and is emitted from the exit surface.

The position where the light deflection element is provided is not limited as long as the light propagating in the light guide plate is reflected toward the exit surface and the function as the light guide plate is not impaired. In the case of a liquid crystal display device in which a light guide plate is used, it is preferable that the intensity of the emitted light over the entire wide emission surface is uniform. It is preferably provided on the surface.

FIG. 2A shows the progress of light in the plate when the light source 10 is adjacent to the end surface of the transparent plate 7 made of the material used for the light guide plate and the light is incident. The light incident on the plate travels while being reflected by total reflection inside the transparent plate 7, and is emitted from the end face on the opposite side of the light source 10. Since the light is totally reflected on the inner surface of the plate, it cannot be emitted from the main surface 71 of the light guide plate.

Subsequently, the light deflection element 22 will be described with reference to FIG. 2 (b).
Light incident on the light guide plate 2 from the light source 10 installed on the side surface of the light guide plate (the end surface 26 of the light guide plate in FIG. 2B) travels in the light guide plate while repeating total internal reflection on the inner surface of the light guide plate. The light guide plate 2 is provided with a plurality of light deflection elements 22 that change the reflection angle when the light is totally reflected (in FIG. 2B, light having a concave structure as an example of the light deflection element 22). The light whose reflection angle has been changed by the light deflection element 22 (which is provided with a deflection element) is emitted to the outside from the emission surface 21. The light deflection element 22 is provided on one of the main surfaces of the light guide plate 2, that is, the light deflection surface 25 which is a surface opposite to the exit surface.

The light guide plate is composed of a transparent member such as a plate or a film, or a laminate of these members. The material of the light guide plate may be a transparent member, and examples thereof include transparent resin and glass. A transparent resin is preferable, and a highly transparent thermoplastic resin is more preferable. Examples of the highly transparent thermoplastic resin include polyolefin-based resins, vinyl-based resins, acrylic-based resins, polyamide-based resins, polyester-based resins, polycarbonate resins, polyurethane-based resins, and polyether-based resins. Of these, polycarbonate resins, acrylic resins, and urethane resins having no wavelength absorption region in the visible light region are preferable from the viewpoint of transparency.

The structure of the light deflection element that changes the light reflection angle in the light guide plate is not particularly limited, but it is preferable to have a plurality of dot structures having a concave or convex structure, and the concave dot structure is preferable. More preferred. These structures may be used alone or in combination of a plurality of structures. The concave shape indicates a concave shape with respect to the surface of the light guide plate, and the convex shape indicates a convex shape with respect to the surface of the light guide plate. FIG. 3A is an example showing a concave dot structure, in which a plurality of hemispherical concave light deflection elements 23 are provided with respect to the surface of the light deflection surface 25, which is a surface opposite to the exit surface 21 of the light guide plate 2. It is formed. FIG. 3B is an example showing a convex dot structure, in which a plurality of hemispherical convex light deflecting elements 24 are formed on the surface of the light deflecting surface 25 of the light guide plate 2.

The light deflection element preferably has a concave or convex dot structure having a size of 50 μm or less and a height or depth of 50 μm or less, and a concave dot structure having a size and depth of 50 μm or less. More preferably. By doing so, when the light guide laminate according to the present invention is used as a front light, it is possible to prevent the light deflection element structure from being visually recognized.

The ratio of the area of the light deflecting element to the area of the light deflecting surface of the light guide plate is preferably 30% or less, more preferably 20% or less, and further preferably 10% or less. When the ratio of the area of the light deflection element is 30% or less, the visibility of the planar lighting device for a display device is not hindered.

The case where the structure of the light deflection element is a concave dot structure which is a preferable example will be described in detail below.

As described above, the concave dot structure preferably has a size and a depth of 50 μm or less.

Examples of the shape of the concave dot structure are shown in FIGS. 4 (a) to 4 (g). The concave dot structure is not limited to these. By making the concave dot structure in this way, it is possible to easily diffuse the light, so that the uniformity of the light in the exit surface can be improved. These shapes, sizes and depths may be unified into one type, or a plurality of them may be combined.

In the concave dot structure shown in FIGS. 4 (a) to 4 (g), the light deflecting surface of the light guide plate is a concave dot structure, but a convex dot structure may be used.

Here, the size of the concave dot structure can be X, which is the length shown in FIGS. 4 (a) to 4 (g). X indicates the length of the concave dot structure facing the traveling direction of light, and contributes to the performance of the concave dot structure with respect to light. Further, the depth of the concave dot structure can be the distance from the plane AA having the concave dot structure to the deepest position of the concave dot structure.

Here, in the case of the convex dot structure, the "depth" of the concave dot structure is the "height". In this case, the height can be the distance from the plane having the convex dot structure to the highest position of the convex dot structure.

Further, the size and depth of the concave dot structure can be changed according to the distance from the light source, up to 50 μm each. For example, the size and depth of the concave dot structure can be continuously increased as the distance from the light source increases. In this case, the amount of light emitted from the exit surface is small at a position close to the light source and the light is strong, and the amount of light emitted increases as the distance from the light source member increases, so that the uniformity of the amount of emitted light can be improved.

Further, a concave dot structure having a large size may be used only in a portion where light is to be emitted more strongly, or a dot structure having a structure in which only a part is different may be used so that only a part has a different appearance.

The dot structure can be randomly and plurally arranged on the surface of the light guide plate, or the dot structure is arranged so that the distribution density of the dot structure increases as the distance from the side closer to the light source 10 of the light guide plate 2 increases. {Fig. 5 (a)}. For example, the distribution density can be ^{about 50 pieces / mm 2 in the region closest to the light source 10 and about 300 pieces / mm 2 in} the region farthest from the light source. By doing so, it is possible to improve the emission uniformity of the light in the emission surface.
When the light source 11 is also installed on another side of the light guide plate 2, {FIG. 5 (b)}, the uniformity of light emission in the emission surface can be improved. The distribution density can be adjusted as appropriate.

2-1-1-2. Characteristics of the light guide plate Since it is assumed that a general display device is visually recognized from the normal direction of the surface on the viewing side of the display device, the light emitted from the light guide plate in the emission surface of the light guide plate in the present invention is emitted. _{The angle θ LGmax} formed by the direction in which the emission intensity is maximized and the normal direction of the emission surface is preferably less than 20 °.

2-1-1-3. Manufacturing method of light guide plate A light deflection element that changes the reflection angle of light is formed on any surface of the light guide plate. The method for producing the light deflection element is not particularly limited, and a known method can be used. For example, processing methods such as ultrasonic processing, heat processing, laser processing, cutting processing, and processing by nanoimprint can be mentioned. For example, when the concave dot structure is manufactured by ultrasonic processing, an ultrasonic processing horn in which the convex dot structure having a shape obtained by inverting the concave dot structure is arranged on the tip surface is applied to the light guide plate material. By pressing vertically, the shape of the dot structure is transferred and a concave dot structure can be formed.

The dot structure can also be produced by screen printing, silk printing, or the like.

As for the dot structure, a concave shape or a convex shape may be formed at the same time as the light guide plate is formed by using a mold or the like prepared so that the dot structure can be formed.

2-1-2. Anisotropic optical film 2-1-2-1. Structure of Anisotropic Optical Film The anisotropic optical film according to the present invention is laminated directly on the emission surface of the light guide plate or via another layer, and the light emitted from the light guide plate is incident on a specific incident surface. It has the function of diffusing at the light angle. That is, the anisotropic optical film is characterized in that the diffusivity of light changes depending on the angle of incident light.

The diffusivity of the anisotropic optical film according to the present invention is defined as the linear transmittance, which is the amount of incident light transmitted in the linear direction / the amount of incident light depending on the angle at which the light is incident on the anisotropic optical film. Can be shown. That is, when the linear transmittance is high, the light incident on the anisotropic optical film has many components of light transmitted linearly and has low diffusivity. When the linear transmittance is low, the incident light has few components that transmit linearly and has high diffusivity.

The anisotropic optical film according to the present invention includes a matrix region and a structural region including a plurality of structures. The structure will be described in detail below with reference to FIGS. 6 to 9.

FIG. 6 shows the structure of an anisotropic optical film having a structural region composed of a plurality of structures having a pillar (substantially columnar) structure and a louver (substantially plate-like) structure, and transmitted light incident on these anisotropic optical films. It is a schematic diagram which shows an example of the state of. FIG. 7 is an explanatory diagram showing a method for evaluating the light diffusivity of the anisotropic optical film. FIG. 8 is a graph showing the relationship between the incident light angle on the anisotropic optical film having the pillar structure and the louver structure shown in FIG. 6 and the linear transmittance. FIG. 9 is a graph (optical profile) for explaining a diffused region and a non-diffused region.

An anisotropic optical film is a film in which a structural region composed of a plurality of structures having a refractive index different from that of the matrix region of the film is formed in the film thickness direction.

The structural region may be formed over the entire region from one surface to the other surface of the anisotropic optical film, or may be formed partially or intermittently.

The cross-sectional shape of the structure is not particularly limited, but for example, as shown in FIG. 6A, a substantially columnar shape (for example, a rod shape) having a small major axis and a minor axis aspect ratio is formed in the matrix region 31a. ), And an anisotropic optical film (anisotropic optical film 3a having a pillar structure) in which a pillar structure 32a having a refractive index different from that of the matrix region is formed, and as shown in FIG. 6 (b). Anisotropic optical film (anisotropic optical film 3b having a louver structure) in which a louver structure 32b having a refractive index different from that of the matrix region is formed in the matrix region 31b in a substantially plate shape having a large aspect ratio. There is.

The shape of these structural regions may be composed of only a single shape, or may be used in combination of a plurality of shapes. For example, the pillar structure and the louver structure may be mixed. By doing so, the optical characteristics of the optical film, particularly the linear transmittance and diffusivity, can be widely adjusted.

2-1-2-2. 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 angle is the orientation direction of regions having different refractive indices (for example, the extending direction (orientation direction) of the pillar structure 32a in the pillar structure and the louver structure in the louver structure). When it is substantially parallel to the height direction of 32b), diffusion is prioritized, and when it is not parallel to the direction, transmission is prioritized.

Here, the light diffusivity of the anisotropic optical film will be described more specifically with reference to FIGS. 7 and 8. Here, the light diffusivity of the above-mentioned anisotropic optical film 3a having a pillar structure and the anisotropic optical film 3b having a louver structure will be described as an example.

The method for evaluating the light diffusivity is as follows. First, as shown in FIG. 7, the anisotropic optical films 3a and 3b are arranged between the light source 40 and the detector 41. In the present embodiment, the case where the irradiation light I from the light source 40 is incident from the normal direction of the anisotropic optical films 3a and 3b is defined as an incident light angle of 0 °. Further, the anisotropic optical films 3a and 3b are arranged so as to be arbitrarily rotated around the straight line L, and the light source 40 and the detector 41 are fixed. That is, according to this method, a sample (anisometric optical film 3a, 3b) is arranged between the light source 40 and the detector 41, and the sample is moved straight while changing the angle with the straight line L on the sample surface as the central axis. By measuring the amount of linearly transmitted light that is transmitted and enters the detector 41, the linear transmittance for each incident angle can be calculated.

The light diffusivity when the anisotropic optical films 3a and 3b were selected as the straight line L at the center of rotation shown in FIG. 7 in the TD direction (width direction of the anisotropic optical film) of FIG. 6 was evaluated and obtained. The evaluation result of the light diffusivity obtained is shown in FIG.

FIG. 8 shows the incident light angle dependence of the light diffusivity (light scattering property) of the anisotropic optical films 3a and 3b shown in FIG. 6 measured by the method shown in FIG. The vertical axis of FIG. 8 is the linear transmittance which is an index showing the degree of scattering {In this embodiment, when the irradiation light of a predetermined amount of light is incident from the normal direction of the anisotropic optical films 3a and 3b, it is incident. The ratio of the amount of light emitted in the same direction as the direction, more specifically, the linear transmittance = (the amount of linear transmitted light / different, which is the amount of light detected by the detector 41 when there are anisotropic optical films 3a and 3b). The incident light amount) × 100}, which is the detected light amount of the detector 41 in the absence of the square optical films 3a and 3b, is shown, and the horizontal axis indicates the incident light angle on the anisotropic optical films 3a and 3b.

The solid line in FIG. 8 shows the light diffusivity of the anisotropic optical film 3a having a pillar structure, and the broken line shows the light diffusivity of the anisotropic optical film 3b having a louver structure. The positive and negative of the incident light angle indicate that the directions in which the anisotropic optical films 3a and 3b are rotated are opposite.

As shown in FIG. 8, the anisotropic optical films 3a and 3b 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 of the incident light angle dependence as shown in FIG. 8 is 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 due to the decrease in the linear transmittance, it generally shows the light diffusivity. It can be said that there is.

Further, in the optical profile, when the incident light angle to the anisotropic optical film is changed, the light diffusivity (linear transmissivity) is the incident light angle of light having substantially symmetry with the incident light angle as a boundary. The direction of coincidence is referred to as "scattering center axis direction", and this axis of symmetry is referred to as "scattering center axis". It should be noted that "having substantially symmetry" means that when the scattering center axis has an inclination with respect to the normal direction of the anisotropic optical film, the optical profile, which is an optical characteristic, is strictly symmetric. This is because it does not have. The incident light angle at this time is a substantially central portion (central portion of the diffusion region) sandwiched between the minimum values in the optical profile by measuring the optical profile of the anisotropic optical film.

The orientation direction (extending direction) of the plurality of structures in the structural region is preferably formed so as to be parallel to the scattering central axis direction, and the anisotropic optical film has desired linear transmittance and diffusivity. It can be determined as appropriate. It should be noted that the direction of the central axis of scattering and the direction of orientation of the columnar region are parallel as long as they satisfy the law of refractive index (Snell's law), and do not have to be exactly parallel.

Snell's law states that when light is incident from a medium having a refractive index n1 to the interface of a medium having a refractive index n2, the relationship of n1sin θ1 = n2sinθ2 is established between the incident light angle θ1 and the refraction angle θ2. Is. For example, if n1 = 1 (air) and n2 = 1.51 (anisometric optical film), the orientation direction (refraction angle) of the structural region is about 19 ° when the incident light angle is 30 °. Even if the incident light angle and the refraction angle are different as described above, if Snell's law is satisfied, the present invention includes the concept of parallelism.

Next, the scattering center axis P in the anisotropic optical film will be further described with reference to FIG. FIG. 10 is a three-dimensional polar coordinate display for explaining the scattering center axis P in the anisotropic optical film.

According to the three-dimensional polar coordinate display as shown in FIG. 10, the scattering center axis is represented by a polar angle θ and an azimuth angle φ, where the surface of the anisotropic optical film is the xy plane and the normal is the z axis. can do. That is, it can be said that Pxy in FIG. 10 is the length direction of the scattering center axis P projected on the surface of the anisotropic optical film.

Here, the normal of the anisotropic optical film (z-axis shown in FIG. 10) and the orientation direction (orientation direction) of the plurality of structures are included in the concept of being parallel to the scattering center axis direction as described above. The polar angle θ (−90 ° <θ <90 °) formed with (if any) is defined as the scattering center axis angle in the present invention. The orientation direction of the plurality of structures can be adjusted to a desired angle by changing the direction of the light rays irradiating the composition containing the sheet-shaped photopolymerizable compound at the time of producing them.

When the anisotropic optical film according to the present invention includes a plurality of scattering center axes, the anisotropic optical film may include the plurality of structures in which each of the plurality of scattering center axes and the orientation direction are in a parallel relationship. preferable.

In contrast to the optical profile, a normal isotropic light diffusing film shows a mountain-shaped optical profile with a peak near 0 °. On the other hand, in the anisotropic optical films 3a and 3b, as shown in FIG. 8, the angle of the pillar structure 32a and the louver structure 32b in the scattering center axis direction with respect to the normal direction of the anisotropic optical film is 0 ° (this). In this case, as shown in FIG. 6, assuming that the orientation directions of the plurality of structures are also 0 °), the linear transmittance is small at the incident light angle near 0 ° (-20 ° to + 20 °), and the incident light angle (absolute value). Shows a valley-shaped optical profile in which the linear transmittance increases as the value increases.

As described above, the anisotropic optical film has a property that the incident light is strongly diffused in the incident light angle range close to the scattering center axis, but the diffusion is weakened and the linear transmittance is increased in the incident light angle range beyond that. .. 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, and the other incident light angle range is referred to as a non-diffuse region (transmission region). Refer to.

Here, with reference to FIG. 9, the diffusion region and the non-diffusion region will be described by taking the anisotropic optical film 3a having a louver structure as an example. FIG. 9 shows the optical profile of the anisotropic optical film 3b having the louver structure of FIG. 8, and as shown in FIG. 9, the maximum linear transmittance (in the example of FIG. 9, the linear transmittance is about about. 78%) and the minimum linear transmittance (in the example of FIG. 9, the linear transmittance is about 6%) and the intermediate value of the linear transmittance (in the example of FIG. 9, the linear transmittance is about 42%). The incident light angle range between the light angles (inside the two incident light angles at the positions of the two black spots on the optical profile shown in FIG. 9) is the diffuse region, and the others (two on the optical profile shown in FIG. 9). The incident light angle range (outside the two incident light angles at the position of the black spot) is the non-diffusing region.

In the present invention, since the anisotropic optical film is used in combination with the light guide plate, the angle range of the incident light at which the linear transmittance is 30% or less (the two linear transmittances on the optical profile are 30% or less). The range between each incident light angle value) is treated as a "diffuse range", which is a range with high diffusivity. That is, the anisotropic optical film of the present invention has a linear transmittance of more than 30% when it is incident from the direction in which the emission intensity on the emission surface of the light guide plate is maximized. It can be said that it has low diffusivity with respect to light from the direction in which the emission intensity on the surface is maximized.

In the anisotropic optical film 3a having a pillar structure, as can be seen from the state of the transmitted light in FIG. 6A, 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 3a having a pillar structure, the diffusion of light is isotropic.

Further, as shown by the solid line in FIG. 8, even if the incident light angle is changed, the change in light diffusivity (particularly, the optical profile near the boundary between the non-diffusing region and the diffusing region) is relatively gradual, so that the brightness is increased. It has the effect of not causing sudden changes or glare.

However, the anisotropic optical film 3a is displayed because the linear transmittance in the non-diffuse region is low, as can be seen by comparing with the optical profile of the anisotropic optical film 3b having a louver structure shown by the broken line in FIG. There is also a problem that the characteristics (brightness, contrast, etc.) are slightly deteriorated.

Further, the anisotropic optical film 3a having a pillar structure has a problem that the width of the diffusion region is narrower than that of the anisotropic optical film 3b having a louver structure.

On the other hand, in the anisotropic optical film 3b having a louver structure, as can be seen from the state of the transmitted light in FIG. 6 (b), the transmitted light has a substantially needle shape and is emitted in the MD direction and the TD direction. Diffusivity is very different. That is, in the anisotropic optical film 3b having a louver structure, the diffusion of light has anisotropy.

Specifically, in the example shown in FIG. 6, 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. 8, when 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 (in the case of this embodiment, in the TD direction). When the anisotropic optical film 3b is applied to a display device, it may appear as a sudden change in brightness or glare, which may reduce visibility.

Further, the anisotropic optical film having a louver structure has a problem that light interference (rainbow) is likely to occur.

On the other hand, the anisotropic optical film 3b has an effect that the linear transmittance in the non-diffusion region is high and the display characteristics can be improved.

As described above, the optical characteristics of the anisotropic optical film change depending on the aspect ratio of the plurality of structures in the anisotropic optical film. That is, the optical characteristics of the anisotropic optical film can be adjusted by adjusting the aspect ratio.

Here, the aspect ratio is the major axis / minor axis when the cross-sectional shape of the plurality of structures in a plane whose normal direction is the orientation direction of the plurality of structures has a major axis (major axis) and a minor axis (minor axis). If the minor axis is the aspect ratio and the cross-sectional shape is almost circular and the major axis and minor axis cannot be significantly defined, then both the major axis and minor axis are assumed to correspond to the diameter of the circle, and the aspect in this case is 1. And.

The diameter can be measured by a known method. As a measuring method, for example, each diameter can be measured by observing the cross-sectional shapes of 10 randomly selected structures with a scanning electron microscope or the like, and the aspect ratio can be determined from the average diameter thereof.

The aspect ratio is not particularly limited, but as the aspect ratio increases, a sudden change in brightness and glare may occur. Therefore, the aspect ratio is preferably 1 or more and less than 50, and more preferably 1 or more and 10 or less. It is preferable, and it is more preferably 1 or more and 5 or less. By setting the aspect ratio in such a range, a sudden change in brightness and glare are suppressed, and the diffusivity and light condensing property of light are improved.

Further, the anisotropic optical film has a linear transmittance of more than 30% with respect to the incident light at an angle at which the emission intensity in the emission surface of the light guide plate is maximized. That is, since the diffusivity is low and the linear transmittance of the incident light can be passed in a high state, the illuminance in the light guide plate emission direction can be maintained. As a result, when the light guide laminate of the present invention is used as the front light of the display device, when the surrounding environment is dark, the light source is used to obtain the same emission characteristics (diffusivity) as when the light guide plate alone is used. It becomes possible to have.

Further, the scattering central axis direction of the plurality of structures of the anisotropic optical film preferably has an angle of more than 20 ° with the direction in which the emission intensity of the light guide plate is maximized. By doing so, the light emitted from the main light guide plate emission surface is less diffused in the anisotropic optical film, and the emission characteristics (diffusivity) of the light guide plate are less likely to be impaired.
Further, in the incident angle range of the light guide plate emitted light having the angle of 20 ° or less, the diffusivity is increased and the linear transmittance may be lowered.

The orientation direction of the plurality of structures of the anisotropic optical film is preferably an angle of more than 13 ° with the direction in which the emission intensity of the light guide plate is maximized. By doing so, the light emitted from the main light guide plate emission surface is less diffused in the anisotropic optical film, and the emission characteristics (diffusivity) of the light guide plate are less likely to be impaired.
Further, in the incident angle range of the light guide plate emitted light having the angle of 13 ° or less, the diffusivity is increased and the linear transmittance may be lowered.

2-1-2-3. Method for Producing Anisotropic Optical Film The anisotropic optical film according to the present invention can be produced by a known method and is not particularly limited. As a preferable method for producing the anisotropic optical film according to the present invention, for example, WO2015 / 111523 is published for an anisotropic optical film having a pillar structure, and Japanese Patent Application Laid-Open No. 10 for an anisotropic optical film having a louver structure. The production method disclosed in Japanese Patent Application Laid-Open No. 2015-12789 can be used.

2-1-2-4. Method for manufacturing a light guide laminate In the light guide laminate according to the present invention, the above-mentioned light guide plate and an anisotropic optical film are laminated directly or via another layer. As the laminating method, a known method can be used. For example, a method of bonding with a roller performed on a flat plate, a method of bonding through a gap between two rollers, and the like can be mentioned. When a pressure-sensitive adhesive layer or the like is included, a method of heating and laminating can be used as needed.

2-1-2-5. Application of light guide laminate The light guide laminate can be used as a planar illumination device for an edge-type light type display device by installing a light source on a side surface (end surface) of the light guide plate. The light source can be installed on one or more side surface portions (end faces) of the light guide plate. When the light sources are installed on a plurality of side surface portions, the distribution density of the dot structure on the surface of the light guide plate can be adjusted as described above. From the viewpoint of reducing the size of the device, it is preferable to install the light source on one side surface.

A known light source can be used, and the light source is not particularly limited. Examples include rod-shaped cold cathode tubes and LEDs. An LED light source is preferable from the viewpoint of size saving and power consumption.

The planar lighting device can be used as a front light for a display device.

The planar illumination device for a display device is used for a transmissive display device and a reflective display device.

2-1-2-6. Optical action by the light guide laminate when used as a surface lighting device for display devices The light guide laminate of the present invention is outside sunlight, lighting, etc. when a light source is installed to make a surface lighting device for display devices. When the ambient environment is bright due to light, it is not necessary to use a light source for the planar illumination device for the display device, but after the external light enters from the light deflection surface side of the light guide plate, it differs in the anisotropic optical film. Since light is diffused and condensed around the scattering center axis direction of the square optical film and the orientation direction of a plurality of structures, it is sufficiently bright (high visibility) even when only external light is used. ) A light guide laminate having characteristics and a lighting device for a display device using the same can be used.

Further, when the surrounding environment is dark, a light source is used, but when the light emitted in the direction in which the emission intensity of the light from the light guide plate emission surface is maximized is incident on the anisotropic optical film. Since the linear transmittance of the anisotropic optical film is more than 30%, the difference between the scattering central axis direction of the anisotropic optical film and the orientation direction of the plurality of structures and the emission direction of the light guide plate is large. Therefore, the light diffusivity of the maximum light emitted from the light guide plate in the anisotropic optical film is low, and the incident light incident on the anisotropic optical film from the light guide plate is passed through and emitted in a state of high linear transmittance. Therefore, it is possible to maintain the illuminance in the light guide plate emission direction, and it is possible to obtain the same emission characteristics (diffusivity) as when the light guide plate alone is used.

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.

(Manufacturing of light guide plate)
The light guide plate used in the present invention is a PMMA sheet having a main surface of 130 mm × 90 mm and a thickness of 2 mm, using a known nanoimprint technique, and has a size of about 10 μm in both vertical and horizontal directions and a depth of about 10 μm in FIG. 4 (f). The concave dot structure having the shape shown in () ^{exists at a density of about 100 pieces / mm 2} and is used as the light guide plate 1.
Further, the light guide plate 2 was manufactured in the same manner as the light guide plate 1 except that the concave dot structure has the shape shown in FIG. 4 (a).

(Manufacturing of light guide plate surface lighting device)
An optical PET film (A4100, manufactured by Toyobo Co., Ltd.) was attached to the light emitting surface side of the light guide plate produced above via a transparent silicon adhesive film (NSA-50, manufactured by Nipper Co., Ltd.).
Subsequently, five LED light sources (200 mW) were installed at intervals of 15 mm on the 90 mm side edge of the light guide plate to form a light guide plate surface lighting device.

(Evaluation of optical characteristics of light guide plate surface lighting device)
The LED light source of the light guide plate surface lighting device is turned on, and the illuminance (emission intensity) of the light emitted from the light emitting surface on the light emitting side of the light guide plate or near the center of the light deflection surface is measured by the goniophotometer. The optical characteristics of the light guide plate were evaluated by measuring with (manufactured by Genesia Co., Ltd.). When measuring the illuminance, in order to avoid the influence of light from the surface (exit surface or light deflection surface) opposite to the surface to be measured, a black felt sheet (FU-714, FU-714) having a thickness of 2 mm is opposed to the surface on the opposite side. Waki Sangyo Co., Ltd.) was brought into close contact with the measurement.
In this measurement, the angle formed by the emission light direction indicating the maximum value of the illuminance of the light on the emission surface (maximum value of the emission intensity) and the normal direction of the emission surface was _defined as θ LGmax.
Subsequently, HWHM (Half With Half Maximum) in the graph of the measured value of light illuminance on the exit surface (emission light profile) was used as the diffusion width which is an index of light diffusivity (however, in this embodiment, the emission intensity is the maximum). Since the emission light angle is far from 0 °, which is the normal direction of the emission surface, if only one emission angle, which is 1/2 of the emission intensity, can be confirmed within the measurement range of the graph. The absolute value of the difference between the emission light angle at which the emission intensity is maximized and the identifiable 1 angle of the emission light angle at which the emission intensity is halved is defined as the diffusion width which is HWHM).
As described above, Table 1 shows the evaluation results of the optical characteristics when the light guide plate surface lighting device is used.

(Preparation of anisotropic optical film)
Regarding the method for producing the anisotropic optical film (LCF1 to 13), first, the anisotropic optical film having a pillar structure is published internationally WO2015 / 111523, and then the anisotropic optical film having a louver structure is described in JP-A-2015. Anisotropic optical films (LCF1 to 13) having the structures shown in Table 2 and having a thickness of 40 μm were prepared by shaking various conditions with reference to 127819.

(Characteristic evaluation of anisotropic optical film)
The characteristic evaluation of the produced anisotropic optical film (LCF1 to 13) was carried out as follows.

(Thickness of anisotropic optical film)
The thickness of the anisotropic optical film (LCF1 to 13) was measured by observing a cross section of the anisotropic optical film in the thickness direction with an optical microscope.

(aspect ratio)
The surface (ultraviolet irradiation side at the time of manufacture) of the anisotropic optical film (LCF1 to 13) is observed with an optical microscope, and the diameters (diameter or major axis and minor axis) of any 10 structures are measured, and each of them is measured. After calculating the average value, the aspect ratio (average major axis / average minor axis when having a major axis and a minor axis, and 1 when only the diameter is used) was calculated based on the calculated diameter.

(Orientation angle)
The angles (orientation angles) of the plurality of structures of the anisotropic optical films (LCF1 to 13) in the orientation direction were measured by observing the thickness direction cross sections of the anisotropic optical films.

(Scattering center axis angle, linear transmittance)
The optical characteristics of the anisotropic optical films of Examples and Comparative Examples were evaluated using a variable angle photometer Goniophotometer (manufactured by Genesia Co., Ltd.) as shown in FIG. The detector was fixed at a position where it received straight light from the fixed light source, and a sample of anisotropic optical film (LCF1 to 13) was set in the sample holder between them. As shown in FIG. 7, the sample is rotated around the straight line (L) as the rotation axis, and the straight line transmission corresponding to each incident light angle (including 0 ° in which the straight line light is the normal direction of the anisotropic optical film plane). The amount of light was measured and the linear transmittance was obtained. Here, the straight line (L) shown in FIG. 7 is the same axis as the TD direction in each structure shown in FIG. The amount of linearly transmitted light was measured at a wavelength in the visible light region using a luminosity factor filter.
An optical profile is created based on the above linear transmittance, and the incident light angle having substantially symmetry is defined as the scattering center axis angle (θ _LCF ) from the optical profile, and the emission intensity obtained by evaluating the optical characteristics of the light guide plate. The linear transmittance at the emission light angle showing the maximum value (−5 ° and + 55 °) was obtained.

Table 2 shows the characteristics evaluation results of the anisotropic optical films (LCF1 to 13) produced as described above.

(Preparation of isotropic scatterer)
An isotropic scatterer for comparison was prepared as follows.
Silicone resin fine particles (Tospearl 145, manufactured by Momentive Performance Materials Co., Ltd.) are appropriately used as fine particles having a refractive index different from that of the pressure-sensitive adhesive composition with respect to 100 parts by mass of the following acrylic pressure-sensitive adhesive composition having a refractive index of 1.47. It was added to adjust the desired haze value. At that time, the mixture was stirred with an agitator for 30 minutes to prepare a fine particle dispersion coating liquid. Using a comma coater, the coating liquid is applied onto a release PET film 1 (Therapeutics BX8A, manufactured by Toray Film Processing Co., Ltd.) so that the film thickness after solvent drying is 40 μm, and the coating solution is dried. An isotropic scatterer with PET was prepared. Further, the surface of the scatterer is laminated with a release PET film 2 (Cerapeel BXE, manufactured by Toray Film Processing Co., Ltd.) having a thickness of 38 μm, which has a higher peeling force than the release PET film 1, and isotropic with double-sided PET. An isotropic scatterer (DA1), which is a sex diffusion adhesive layer, was prepared.
Acrylic adhesive composition ・ Acrylic adhesive (total solid content concentration 18.8%, solvent: ethyl acetate, methyl ethyl ketone) 100 parts by mass (manufactured by Soken Kagaku Co., Ltd., trade name: SK Dyne TM206)
-Isocyanate-based curing agent 0.5 parts by mass (manufactured by Soken Chemical Co., Ltd., trade name: L-45)
-Epoxy-based curing agent 0.2 parts by mass (manufactured by Soken Chemical Co., Ltd., product name: E-5XM)

(Evaluation of haze value of isotropic scatterer)
The haze value was measured in accordance with JIS K7136 using a haze meter manufactured by Nippon Denshoku Co., Ltd., NDH-2000.
Table 3 shows the evaluation results of the haze value of the prepared isotropic scatterer (DA1).

(Manufacturing of light guide laminate)
A transparent silicon adhesive film (NSA-50, manufactured by Nipper Co., Ltd.) is attached to the exit surface of the obtained light guide plates (light guide plates 1 and 2), and then to the surface of the attached adhesive film. By laminating an anisotropic optical film (LCF1 to 13) or an isotropic scatterer (DA1), the light guide laminates (laminates 1 to 5, comparative laminates 1 to 10) shown in Table 4 were obtained. ..
For each of the produced light guide laminates, the light guide plate used, the emission light angle (θ _LGmax ) at which the emission intensity of the light guide plate shows the maximum value, the anisotropic optical film used, and the name of the isotropic scatterer. , The difference between the scattering center axis angle (θ _LCF ) of the anisotropic optical film, the linear transmittance of the anisotropic optical film at the emission light angle indicating the maximum value of the light guide plate emission intensity, and θ _LGmax and θ _LCF . The absolute values of θ _LGmax −θ _LCF are summarized in Table 4.

(Manufacturing of light guide laminated body surface lighting device and evaluation of optical characteristics of light guide laminated body surface lighting device)
In the production of the light guide laminated body planar lighting device, instead of the light guide plate and the transparent silicon adhesive film in the production of the light guide plate planar lighting device, the light guide laminated body (laminates 1 to 5, comparative laminate) produced above is used. The light guide laminated body surface lighting devices (Examples 1 to 5 and Comparative Examples 1 to 10) shown in Table 5 were obtained in the same manner except that the bodies 1 to 10) were used.
Further, in the evaluation of the optical characteristics of the light guide laminated body surface lighting device, instead of the light guide plate surface lighting device, the light guide laminated body surface lighting device (Examples 1 to 5 and Comparative Examples 1 to 10) produced above is used. In addition to the above-mentioned evaluation on the emission surface of the light guide plate surface lighting device, the light guide laminated body surface lighting device is evaluated by replacing it with an anisotropic optical film or a surface on the isotropic scatterer side. The optical characteristics of the light guide plate surface lighting device were evaluated in the same manner as in the evaluation.

(Evaluation of reflected brightness)
A smooth mirror-reflecting plate (reflectance of about 90%) is attached to the surface of the anisotropic optical film or the isotropic scatterer side of the light guide laminate planar illumination device via a transparent adhesive layer. It was used as a sample for evaluation of reflection brightness.
The reflection brightness of the above-mentioned reflection brightness evaluation sample was measured using a variable-angle photometer Gonio Photometer (manufactured by Genesia Co., Ltd.) (at that time, the light source of the planar illumination device was not turned on during the evaluation). Specifically, collimated light was emitted from a halogen lamp light source via a collimated lens from the light deflection surface side at an incident angle of −30 ° with respect to the normal direction of the evaluation sample. At this time, in the case of the sample using the anisotropic optical film, the collimated light was irradiated from the azimuth direction (opposite azimuth angle) 180 ° different from the azimuth direction of the scattering center axis. In the case of a sample that does not use an anisotropic optical film, the azimuth direction is arbitrary. The detector was installed in the normal direction of the sample (measurement angle was + 15 °), and the reflected brightness was measured. The reflection brightness was measured in advance with a standard white plate at an incident angle of −30 ° and a measurement angle of + 30 °, and the reflection brightness gain was calculated by the following formula.
Reflected brightness gain = (Reflected brightness of sample ÷ Reflected brightness of standard white plate) x 100

As described above, Table 5 below shows the relationship between the light guide laminates used in the light guide laminate surface illumination device, and the evaluation results of the optical characteristics and the reflected brightness when the light guide laminate surface illumination device is used. Further, the diffusion width and the reflection brightness were evaluated according to the following evaluation criteria, and are shown in Table 5.

(Diffusion width evaluation criteria)
◯: The diffusion width is a value within the range of -10% to + 10% with respect to the diffusion width of each light guide plate surface illumination device used ×: The diffusion width is each light guide plate surface illumination device used. A value that is less than -10% or greater than + 10% with respect to the diffusion width of

(Reflective brightness evaluation standard)
◯: The reflection brightness is 10 or more, and the reflection brightness is sufficient (bright and good visibility).
X: Reflected brightness is less than 10, reflected brightness is insufficient (dark, poor visibility)

(Evaluation results)
As shown in Table 5, Examples 1 to 5 of the present invention maintain a diffusion width close to (within a range of -10% to + 10%) the diffusion width of the light guide plate surface lighting device as compared with Comparative Examples 1 to 10. However, the reflected brightness is sufficiently good, that is, when the planar lighting device for a display device is used, the surrounding environment is dark, and even when a light source is used, the emission characteristics are the same as when the light guide plate is used alone (diffusivity). ) It can be seen that the ambient environment is bright and the property is sufficiently bright (high visibility) even when a light source is not used.
On the other hand, Comparative Examples 1 and 9 using the isotropic scatterer DA1 having a haze value of 85% and the linear transmittance of the anisotropic optical film at the emission light angle at which the light emission intensity of the light guide plate is maximized. Comparative Examples 2 to 8 and 10 using LCFs 4 to 10 and 13 having a rate of 30% or less have a value having a large difference from the diffusion width of the light guide plate surface illuminating device (less than -10% or more than + 10%). Is also a large value), and it can be seen that the characteristics of the light guide plate are impaired. This is due to the isotropic light diffusivity of the isotropic scatterer at the emission light angle at which the light emission intensity of the light guide plate is maximized, and the high diffusivity of the anisotropic optical film. Was speculated.
Further, in Comparative Example 3, in addition to impairing the characteristics of the light guide plate, LCF5 having a scattering center axis angle and an orientation angle of 0 ° of the anisotropic optical film is used, so that external light is used. The result was that the reflected brightness value for only light was low and the visibility was poor.

As described above, the present invention has the same emission characteristics (diffusivity) as when the light guide plate alone is used when the ambient environment is dark, and when the ambient environment is bright, the light source is not used. Even so, it is possible to provide a light source laminate having sufficiently bright (high visibility) characteristics and a planar illumination device for a display device using the light source laminate.

1: Light guide laminate 2: Light guide plate 3: Anisometric optical film 3a: Anisotropic optical film with pillar structure 3b: Anisotropic optical film with louver structure 4: Polarizing plate 5: Phase difference plate 6: Sealing Layer 7: Transparent plates 10, 11: Light source 21: Emission surface 22: Light deflection element 23: Concave light deflection element 24: Convex light deflection element 25: Light deflection surface 26: Light guide plate end faces 31a, 31b: Matrix region 32a: Pillar structure 32b: Louver structure 40: Light source 41: Detector 71: Main surface

Claims (7)

A light guide laminate including a light guide plate and at least one anisotropic optical film.
The light guide plate has an incident surface that allows light to enter the inside of the light guide plate, and
The light incident from the incident surface has an exit surface that is reflected and refracted in the light guide plate and emitted.
The anisotropic optical film is a film in which the linear transmittance, which is the amount of transmitted light in the linear direction of the incident light / the amount of incident light, changes depending on the angle at which the light is incident on the anisotropic optical film.
The anisotropic optical film is laminated on the exit surface directly or via another layer.
The anisotropic optical film includes a matrix region and a structural region including a plurality of structures.
When the light emitted in the direction in which the emission intensity of the light from the emission surface is maximized is incident on the anisotropic optical film, the linear transmittance of the anisotropic optical film is more than 30%. A light guide laminate. The direction of the scattering center axis of the plurality of structures of the anisotropic optical film and
The light guide laminate according to claim 1, wherein the angle formed by the direction in which the light emission intensity of the light guide plate is maximized is more than 20 °. The light guide according to claim 1 or 2, wherein the angle formed by the direction in which the emission intensity of the light emitted from the emission surface is maximized and the normal direction of the emission surface is less than 20 °. Laminated body. The light guide plate is characterized by having a plurality of concave light deflection elements having a size of 50 μm or less and a depth of 50 μm or less on the light deflection surface which is a surface opposite to the emission surface. The light guide laminate according to any one of claims 1 to 3. The light guide plate is characterized by having a plurality of convex light deflection elements having a size of 50 μm or less and a height of 50 μm or less on the light deflection surface which is a surface opposite to the emission surface. , The light guide laminate according to any one of claims 1 to 3. The light guide laminate according to any one of claims 1 to 5, wherein the other layer contains at least one of a polarizing plate and a retardation plate. A planar lighting device for a display device, comprising the light guide laminate according to any one of claims 1 to 6 and a light source.

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