JP6567466B2 - Transparent light guide plate and transmissive display device using the same - Google Patents

Description

  The present invention relates to a transparent light guide plate and a transmissive display device using the same.

  As a transmissive display device, for example, one disclosed in Patent Document 1 below is known. In the transmissive display device of Patent Document 1, a surface light source is used as a backlight.

  Here, the surface light source supplies light to the liquid crystal plate or the like by, for example, emitting light incident from the side surface of the light guide plate in the thickness direction of the light guide plate. By using a surface light source as a backlight, the transmissive display device can be made thinner than when a fluorescent lamp, an LED array, or the like is used.

  As the surface light source, for example, one disclosed in Patent Document 2 below is known. In Patent Document 2, a large number of spherical light reflecting protrusions (light reflecting dots in Cited Document 2) are formed on the back surface of the light guide plate using an inkjet printing technique. Then, light incident from the side surface of the light guide plate is scattered in the light guide plate, and part of the light reaches the inner spherical surface of the light reflection protrusion to be reflected, thereby obtaining light emitted in the thickness direction of the light guide plate. (See FIG. 1 etc. of Cited Document 2).

International Publication No. 2014/010585 JP, 2015-76124, A

  In such a transparent light guide plate, in order to increase the luminous intensity of the emitted light, it is desirable to make the pitch of the light reflecting protrusions as small as possible.

  However, when the pitch of the light reflection protrusions is narrowed to match the pitch of each sub-pixel of the transmissive display device (small pixel that carries RGB of each pixel), interference fringes are generated on the screen of the transmissive display device. End up.

  Similarly, in the case of a monochrome transmissive display device, if the pitch of the pixels of the transmissive display device matches, interference fringes are generated on the screen of the transmissive display device.

  In order to avoid such a drawback, the pitch of the light reflecting protrusions may be set so as not to coincide with the pitch of the sub-pixel (or pixel) of the transmissive display device. However, it is not easy to control the pitch of the light reflecting portions with high accuracy, particularly when the ink jet printing technique is used.

  It is an object of the present invention to provide a transparent light guide plate that does not generate interference fringes on the screen of a transmissive display device and a transmissive display device using the transparent light guide plate.

In order to solve this problem, a transparent light guide plate according to the invention of claim 1 has a substantially rectangular flat plate shape in plan view, and a light-transmitting light guide base material on which light is incident from a side surface, and the light guide. A plurality of light reflecting protrusions that are affixed to the back surface side of the base material and reflected from the inner spherical surface of the light incident from the side surface of the light guide base material and emitted from the surface are embossed. in the light reflecting member formed, a transparent light guide plate having a plurality of light reflecting projection is a two-dimensional direction along the x and y directions perpendicular to each other, regularly in a predetermined arrangement pattern The light reflecting member is affixed to the light guide base so that both the x direction and the y direction are inclined with respect to the side surface of the light guide base. It is characterized by that.

According to a second aspect of the present invention, in addition to the configuration of the first aspect , the light reflecting protrusions are arranged at equal intervals in a staggered pattern or a matrix shape along the x direction and the y direction. To do.

The invention of claim 3 is characterized in that, in addition to the configuration of claim 1 or 2 , the light guide base material and the light reflecting member are flexible.

According to a fourth aspect of the present invention, in addition to the configuration according to any one of the first to third aspects, a part of the light incident on the side surface of the light guide base material is emitted from the back surface.

A transmissive display device according to a fifth aspect of the present invention is a transmissive display device using the transparent light guide plate according to any one of the first to fourth aspects as a backlight, and two transmissive display devices along the X and Y directions perpendicular to each other. A plurality of pixels or sub-pixels arranged in a dimensional direction, wherein the x-direction and the y-direction which are the arrangement directions of the light reflecting protrusions are the X-direction and the Y-direction which are the arrangement directions of the pixels or sub-pixels It is a direction inclined with respect to the direction.

  According to the first aspect of the present invention, since the arrangement direction of the light reflecting protrusions is inclined, it is difficult to generate interference fringes in the transmissive display device, thereby improving the image quality of the transmissive display device. Can do.

In addition, according to the invention of claim 1 , it is possible to make it difficult for interference fringes to be generated simply by inclining and pasting the light reflecting member on which the light reflecting protrusions are formed with respect to the light guide base material. Therefore, manufacture is easy.

According to the invention of claim 2 , since the light reflecting protrusions are arranged at equal intervals in a staggered pattern or a matrix pattern, the manufacturing is easy.

According to the third aspect of the present invention, by making the light guide base material and the light reflecting member flexible, the display screen can be used as a transparent light guide plate of a transmissive display device having a curved surface.

According to the fourth aspect of the present invention, the transparent display device of the present invention can be applied to a transmissive display device in which a part of the light incident on the side surface from the light source is emitted from the back surface so that the display screen and the background are superimposed. A light guide plate can be used.

According to the invention of claim 5 , it is possible to provide a transmissive display device that does not generate interference fringes on the screen.

It is sectional drawing which shows notionally the structure of the transparent light-guide plate which concerns on Embodiment 1 of this invention. It is a top view which shows notionally the structure of the transparent light-guide plate which concerns on the said Embodiment 1. FIG. It is a conceptual fragmentary sectional view for demonstrating the principle of the transparent light-guide plate which concerns on the said Embodiment 1. FIG. It is a conceptual top view for demonstrating the manufacturing method of the transparent light-guide plate which concerns on the said Embodiment 1. FIG.

  Embodiment 1 of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically showing the structure of the transparent light guide plate according to the first embodiment.

  As shown in FIG. 1, the transparent light guide plate 100 includes a light guide base 110, an adhesive layer 120, and a light reflecting member 130.

  The light guide substrate 110 is a plate-like substrate having translucency. As the light guide base 110, a flat plate having a rectangular shape in plan view is used. The light guide substrate 110 may be a rigid plate or a flexible sheet. As a material for forming the light guide base 110, for example, acrylic is suitable, but other materials may be used. The planar dimensions of the light guide substrate 110 are arbitrary, and may be determined according to the screen dimensions of the transmissive display device to be used. Moreover, although the thickness of the light guide base material 110 is also arbitrary, it is about 2 mm, for example. In the first embodiment, the refractive index n0 of the light guide base 110 is set to 1.49.

  For example, a transparent optical adhesive film (OCA) can be used as the adhesive layer 120. However, as long as it has sufficient translucency and adhesive performance, you may use another kind of adhesive sheet, an adhesive agent, etc. The thickness of the adhesive layer 120 is, for example, 0.1 mm. In the first embodiment, the refractive index n1 of the adhesive layer 120 is set to 1.4857.

  The light reflecting member 130 is attached to the back surface of the light guide base 110 using the adhesive layer 120. As the light reflecting member 130, for example, a flat plate having a planar dimension substantially the same as that of the light guide base 110 is used. The light reflecting member 130 may be a rigid plate or a flexible sheet.

  The light reflecting member 130 may have a single layer structure or a multilayer structure. In the example of FIG. 1, the light reflecting member 130 is formed by laminating a base layer 131 and a light reflecting layer 132. These layers 131 and 132 are both light-transmitting layers.

  Here, as a forming material of the base layer 131, for example, PET (that is, polyethylene terephthalate) can be used, but other materials may be used. In the first embodiment, the refractive index n2 of the base layer 131 is set to 1.48. Further, the thickness of the base layer 131 is, for example, 0.05 mm. Since the color temperature of the emitted light tends to increase as the base layer 131 becomes thicker, it is desirable to make the base layer 131 as thin as possible within a range in which the durability of the light reflecting member 130 can be secured.

  As the light reflecting layer 132, for example, an ultraviolet curable resin can be used, but it may be formed of other materials. In the first embodiment, the refractive index n3 of the light reflecting layer 132 is set to 1.5785. Moreover, the thickness of this light reflection layer 132 is 0.012 mm, for example.

  A large number of light reflecting protrusions 132 b are formed on the outer surface 132 a side of the light reflecting layer 132.

  The light reflecting protrusion 132b preferably has a spherical shape. By adopting such a shape, the inner spherical surface of these light reflecting protrusions 132b acts as a concave mirror to reflect a part of the light inserted from the light guide base 110 into the light reflecting member 130, so that the light guide base It can be led to the surface side of the material 110.

  The dimensions of the light reflecting protrusion 132b are, for example, a diameter of 30 to 60 μm and a height of 3 to 5 μm (preferably 3.3 to 4.67 μm).

  As shown in the plan view of FIG. 2, these light reflecting protrusions 132 b are arranged on the outer surface 132 a of the light reflecting layer 132 in the x direction and the y direction (that is, the vertical and horizontal directions of the light reflecting member 130). They are arranged in a two-dimensional direction along the predetermined arrangement pattern at a predetermined pitch. In the example of FIG. 2, the light reflecting protrusions 132b are arranged in a staggered pattern, but a normal matrix shape may be used. In FIG. 2, the vertical and horizontal pitch A is, for example, 0.16 to 0.24 mm, and the diagonal pitch B is, for example, 0.11 to 0.17 mm. Further, the angles θa, θb, and θc of the triangle formed by the three adjacent light reflecting protrusions 132b are arbitrary, but in the first embodiment, θa = θb = θc = 60 ° (that is, a regular triangle). .

  As will be described later, in this embodiment, the light reflecting member 130 is attached to the light guide base 110 so as to be inclined from the vertical and horizontal side surfaces of the light guide base 110. Thereby, the arrangement direction (x direction and y direction) of the light reflecting protrusions 132b of the transparent light guide plate 100 can be inclined with respect to the arrangement direction of the pixels (or sub-pixels) of the transmissive display device. Interference fringes can be made difficult to occur on the screen of the transmissive display device.

  Next, the optical principle of the transparent light guide plate 100 according to the first embodiment will be described with reference to the conceptual partial sectional view of FIG.

  As shown in FIG. 3, light is incident on the transparent light guide plate 100 from the side surface in a direction parallel to the front and back surfaces of the transparent light guide plate 100. As described above, for example, a white LED (not shown) or the like is used as the light source of this light.

  A part of the light incident on the transparent light guide plate 100 reaches the boundary surface 301 between the light guide base 110 and the adhesive layer 120. Then, a part of the light is reflected at the boundary surface 301, and the remaining light is refracted and enters the adhesive layer 120.

  The light incident on the adhesive layer 120 reaches the boundary surface 302 between the adhesive layer 120 and the base layer 131. Then, a part of the light is reflected at the boundary surface 302 and the remaining light is refracted and is incident on the base layer 131.

  Further, the light incident on the base layer 131 reaches the boundary surface 303 between the base layer 131 and the light reflecting layer 132. A part of the light is reflected at the boundary surface 303, and the remaining light is refracted and is incident on the light reflecting layer 132.

  A part of the light incident on the light reflecting layer 132 reaches the light reflecting protrusion 132b and is reflected by the light reflecting protrusion 132b.

  The light reflected by the light reflecting protrusion 132 b reaches the boundary surface 303, a part of which is reflected, and the rest is refracted and enters the base layer 131.

  The light incident on the base layer 131 reaches the boundary surface 302, a part of which is reflected, and the rest is refracted and incident on the adhesive layer 120.

  Furthermore, the light incident on the adhesive layer 120 reaches the boundary surface 301, a part of which is reflected, and the rest is refracted and incident on the light guide substrate 110.

  A part of the light incident on the light guide base 110 is emitted from the surface of the light guide base 110 (the lower side in FIG. 3).

  Here, as is well known, when light reaches the substance B (refractive index is nb) from the substance A (refractive index is na), the reflectance R at the boundary surface is expressed by the following equation (1). (For normal incidence).

R = (na−nb) ² / (na + nb) ² (1)
As shown in this equation (1), the smaller the difference between the refractive indexes na and nb of the substances A and B, the smaller the reflectance R, and thus the greater the transmittance of light reaching the substance B from the substance A.

  In the first embodiment, as described above, the refractive index n0 of the light guide base 110 is 1.49, the refractive index n1 of the adhesive layer 120 is 1.4857, and the refractive index n2 of the base layer 131 is 1.48. The refractive index n3 of the light reflecting layer 132 is 1.5785.

  That is, in the first embodiment, the difference (0.0043) between the refractive index n0 of the light guide base 110 and the refractive index n1 of the adhesive layer 120, and the refractive index n1 of the adhesive layer 120 and the refractive index n2 of the base layer 131. Since the difference (0.0057) is small, the light transmittance is high at the boundary surfaces 301 and 302 of these portions 110, 120, and 131. Therefore, most of the light incident from the side surface of the light guide base 110 reaches the base layer 131.

  On the other hand, the difference (n3−n2 = 0.0985) between the refractive index n3 of the light reflecting layer 132 and the refractive index n2 of the base layer 131 is large. Is smaller than that of the boundary surfaces 301 and 302 (therefore, the reflectance is larger than that of the boundary surfaces 301 and 302).

  On the other hand, since n3> n2, total reflection of light reaching the boundary surface 303 from the base layer 131 side does not occur.

  Therefore, a sufficient amount of light can be guided from the base layer 131 into the light reflecting layer 132.

  Here, as is well known, the greater the incident angle θ1 when reaching the boundary surface 303, the higher the light reflectance. For this reason, a large amount of light having a small incident angle θ1 (that is, light having a small angle with respect to the thickness direction of the transparent light guide plate 100) is incident on the light reflecting layer 132.

  A part of the light incident on the light reflecting layer 132 is reflected by the light reflecting protrusion 132b as described above. As described above, the refractive index n3 of the light reflecting layer 132 is 1.5785, which is sufficiently larger than the refractive index outside the light reflecting layer 132 (usually air), and is therefore reflected by the light reflecting protrusion 132b. The amount of light to be generated is sufficiently large (see the above formula (1)).

  Then, the light reflected in the light reflecting layer 132 reaches the boundary surface 303 again. As described above, the greater the incident angle when the boundary surface 303 is reached, the higher the light reflectance. Further, since this light is incident on a medium having a high refractive index (light reflecting layer 132) and entering a medium having a low refractive index (base layer 131), total reflection is caused for light having an incident angle θ2 larger than a predetermined value. Occur. Therefore, a large amount of light having a small incident angle θ2 (that is, light having a small angle with respect to the thickness direction of the transparent light guide plate 100) is incident on the base layer 131.

  At this time, a part of the light reflected by the boundary surface 303 is scattered in the light reflection layer 132, and becomes incident on the base layer 131 as light having a small incident angle θ2 to the boundary surface 303. Become.

  As described above, a part of the light incident on the base layer 131 passes through the adhesive layer 120 and the light guide base 110 and exits from the surface of the light guide base 110 (the lower side in FIG. 3). . As described above, the difference in refractive index between the base layer 131 and the adhesive layer 120 (n2-n1) and the difference in refractive index between the adhesive layer 120 and the light guide substrate 110 (n0-n1) are small. The transmittance of is sufficiently large.

  As described above, in the first embodiment, the light reflecting member 130 is configured such that the upper layer (that is, the light reflecting layer 132) has a higher refractive index. Since a large amount of light with a small angle can be extracted and thereby the directivity of the emitted light can be increased, the amount of light irradiated on the irradiated surface (for example, a liquid crystal panel of a transmissive display device) can be increased.

  Next, a method for manufacturing the transparent light guide plate 100 according to the first embodiment will be described.

  First, the sheet-like light reflecting member 130 is produced as follows.

  First, an ultraviolet curable resin in a liquid state is applied to the back surface of the base layer 131 (for example, PET).

  Next, the light reflecting protrusion 132b is formed on the ultraviolet curable resin by a stamping process. The method of pressing is not limited, and a direct pressing transfer method in which a flat plate is pressed against the ultraviolet curable resin may be used. However, in order to manufacture the light reflecting member 130 having a large area, a rotary roller type is used. It is desirable to use the roller transfer method used.

  Subsequently, the ultraviolet curable resin is cured by irradiating with ultraviolet rays.

  Thereafter, the light reflecting member 130 is cut into a desired size. The size of the light reflecting member 130 is determined based on the size of the irradiated surface (for example, a liquid crystal panel of a transmissive display device).

  Thus, the sheet-like light reflecting member 130 is completed.

  Next, a step of attaching the light reflecting member 130 to the light guide base 110 is performed as follows.

  First, the adhesive layer 120 is formed on the back surface of the light guide substrate 110. As described above, the method of forming the adhesive layer 120 may be a method of applying a transparent optical adhesive film (OCA), or a method of applying a liquid adhesive or the like to the back surface of the light guide substrate 110. There may be.

  Thereafter, a sheet-like light reflecting member 130 is attached to the back surface of the adhesive layer 120. At this time, in the first embodiment, as shown in the conceptual plan view of FIG. 4, the light reflecting member 130 is attached to the light guide substrate 110 while being inclined. For this reason, the arrangement direction (x direction and y direction) of the light reflecting protrusions 132 b is inclined with respect to each side of the transparent light guide plate 100.

  Thus, the transparent light guide plate 100 is completed.

  Subsequently, a transmissive display device (not shown) is assembled. In this assembly process, the transparent light guide substrate 100 is used as a backlight of a transmissive display device.

  Here, in the transmissive display device, pixels or sub-pixels (for example, liquid crystal elements such as a liquid crystal panel) are arranged in a two-dimensional direction (not shown). Here, the arrangement directions are the X direction and the Y direction. The X direction and the Y direction are directions parallel to the sides of the screen. In addition, the pitch of the pixels or sub-pixels is substantially the same as the pitch of the light reflecting protrusions 132b.

  In this assembly process, each side of the screen of the transmissive display device is made parallel to each side surface of the transparent light guide plate 100.

  Here, as described above, the arrangement direction (x direction and y direction) of the light reflecting protrusions 132 b of the light reflecting member 130 is inclined with respect to each side of the transparent light guide plate 100.

  Accordingly, the arrangement direction of the light reflecting protrusions 132b is inclined with respect to the arrangement direction of the pixels or sub-pixels of the transmissive display device.

  Accordingly, it is possible to prevent the image quality from being deteriorated due to the generation of interference fringes in the transmissive display device, although the pitch of the pixels and sub-pixels is substantially the same as the pitch of the light reflecting protrusions 132b.

  The inclination angle varies depending on the pitch value of the light reflecting protrusions 132b, the arrangement pattern, and the like, but is about 3 to 5 °, for example.

  Here, the light reflecting member 130 is attached while being inclined. However, when the light reflecting member 130 is manufactured, the light reflecting protrusion 132b is formed so as to be inclined with respect to the vertical and horizontal side surfaces of the light reflecting member 130. You may decide. When the light reflecting protrusion 132b is formed to be inclined, the light reflecting member 130 may be attached so that the vertical and horizontal side surfaces of the light reflecting member 130 are parallel to the vertical and horizontal side surfaces of the light guide base 110.

  As described above, according to the first embodiment, it is possible to make it difficult to generate interference fringes of the transmissive display device by inclining the arrangement direction of the light reflecting protrusions 132b.

  Furthermore, since the light reflection member 130 on which the light reflection protrusion 132b is formed can be made difficult to generate interference fringes only by being inclined and attached to the light guide base 110, the manufacture is easy. .

  According to the first embodiment, the light guide base 110 and the light reflecting member 130 are made flexible, so that the display screen can be used as a transparent light guide plate of a transmissive display device having a curved surface.

  In the first embodiment, the case where the transparent light guide plate 100 according to the present invention is used for a liquid crystal display or the like has been described as an example. However, the display screen, the background, It is also possible to use it for a transmissive display device of a type that displays images in a superimposed manner. In this case, light transmitted through the light reflecting member 130 and reflected by the object on the back side is transmitted through the light reflecting member 130, the adhesive layer 120, and the light guide substrate 110.

  In the first embodiment, the case where the light reflecting member 130 is affixed to the light guide substrate 110 has been described as an example. However, for example, the light reflecting protrusion is directly applied to the light guide substrate by an inkjet printing method or the like. Of course, the present invention can also be applied to the formation. In this case, the light reflection protrusions may be arranged so that the arrangement direction of the arrangement pattern of the light reflection protrusions is inclined with respect to each side surface of the light guide base material.

DESCRIPTION OF SYMBOLS 100 Transparent light guide plate 110 Light guide base material 120 Adhesive layer 130 Light reflection member 131 Base layer 132 Light reflection layer 132a Outer side surface 132b Light reflection protrusion 301-303 Boundary surface

Claims (5)

A light-transmitting light-guiding base material that has a substantially rectangular flat plate shape in plan view and receives light from a side surface;
A plurality of light reflecting protrusions that are attached to the back surface side of the light guide base material and reflect at least a part of the light incident from the side surface of the light guide base material on the inner spherical surface and exit from the surface. A light reflecting member formed by embossing ,
A transparent light guide plate having
The plurality of light reflecting protrusions are regularly formed in a predetermined arrangement pattern in a two-dimensional direction along the x direction and the y direction orthogonal to each other.
The light reflecting member is affixed to the light guide base so that both the x direction and the y direction are inclined with respect to the side surface of the light guide base .
A transparent light guide plate characterized by that. 2. The transparent light guide plate according to claim 1, wherein the light reflecting protrusions are arranged at equal intervals in a staggered pattern or a matrix pattern along the x direction and the y direction . The transparent light guide plate according to claim 1, wherein the light guide base material and the light reflecting member are flexible . 4. The transparent light guide plate according to claim 1, wherein a part of light incident on a side surface of the light guide base material is emitted from the back surface. 5. A transmissive display device using the transparent light guide plate according to claim 1 as a backlight,
A plurality of pixels or sub-pixels arranged in a two-dimensional direction along the X and Y directions orthogonal to each other;
The x direction and the y direction, which are the arrangement directions of the light reflecting protrusions, are directions inclined with respect to the X direction and the Y direction, which are the arrangement directions of the pixels or subpixels.
A transmissive display device .

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