JP2014149967A - Light guide plate, backlight unit and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide plate capable of efficiently raising light entered from a light source and suppressing increase in yellow tinge in emission light, and a backlight unit and an image display device having high luminance with less increase in the yellow tinge in emission light.SOLUTION: In a light guide plate 14 for guiding light entered from a light incident surface 13c so that it is emitted from a light emission surface 13a, a plurality of reflection recess parts 11 configured by denting in a thickness direction of a light transmissive base material 13 from a light reflection surface 13b are formed over the entire surface of the light reflection surface 13b. On an inner surface of each reflection recess part 11 and on the light reflection surface 13b excluding the reflection recess parts 11, a blue colored light reflection layer 12 having light scattering reflectivity is formed.

Description

  The present invention relates to a light guide plate, a backlight unit using the same, and an image display device.

In recent years, liquid crystal display devices using TFT (Thin Film Transistor) type liquid crystal panels and STN (Super Twisted Nematic) type liquid crystal panels have been commercialized mainly for color notebook personal computers in the OA field.
The backlight unit used in this type of backlight system is roughly divided into a light source lamp such as a cold cathode fluorescent lamp (CCFL) and a flat plate made of acrylic resin having excellent light transmittance. There are two types: “light guide plate light guide method” (so-called edge light method) that makes multiple reflections within the light guide plate, and “direct type” that directly illuminates with light from a light source lamp such as CCFL without using the light guide plate There is a method.

As a liquid crystal display device equipped with an edge light type backlight unit, for example, the one shown in FIG. 1 is generally known.
As shown in FIG. 1, this type of liquid crystal display device includes a backlight unit and a liquid crystal panel 2 that is disposed at the top of the backlight unit and sandwiches both front and back surfaces of polarizing plates 1 and 3. Prepare.

  The backlight unit includes a light guide plate 7 that is disposed on the lower surface side of the back surface side polarizing plate 3 of the liquid crystal panel 2 and is made of a transparent base material such as an acrylic resin having a substantially rectangular plate shape. A diffusion film (diffusion layer) 4 is provided on the upper surface, that is, the light exit surface. Further, a scattering reflection pattern portion (not shown) is printed on the lower surface of the light guide plate 7 so that the light introduced into the light guide plate 7 is efficiently scattered and reflected toward the liquid crystal panel 2. And a reflection film (reflection layer) 8 is provided below the scattering reflection pattern portion.

Further, a light source lamp 6 is disposed opposite to the short side surface portion of the light guide plate 7 and further covers the back side of the light source lamp 6 so that the light from the light source lamp 6 is efficiently incident on the light guide plate 7. A high-reflectance lamp reflector 5 is provided.
The scattering reflection pattern portion is a mixture of white titanium dioxide (titania) powder mixed with a transparent adhesive solution or the like, printed in a predetermined pattern, for example, a dot pattern, dried, and formed. A directivity is given to the light incident on the light plate 7 and guided to the light exit surface of the light guide plate 7, and a device for increasing the brightness is made.

Recently, a liquid crystal display device as shown in FIG. 2 is known in order to improve the light utilization efficiency and further increase the brightness.
In this type of liquid crystal display device, high brightness can be achieved by providing prism films (prism layers) 9 and 10 having a light condensing function between the diffusion film 4 and the liquid crystal panel 2. The prism films 9 and 10 are for condensing the light emitted from the light exit surface of the light guide plate 7 and diffused by the diffusion film 4 on the effective display area of the liquid crystal panel 2 with high efficiency.
2, the same reference numerals as those in FIG. 1 represent the same components as those in FIG. 1.

  In addition, as an attempt to improve front luminance and uniformity as a surface light source, metallization is performed on a wedge-shaped light guide plate that becomes thinner as it moves away from the light source, or on a light-emitting surface with a predetermined shape. In order to maintain the image quality, it is necessary to use an optical sheet together. ing.

  On the other hand, the direct type, which easily illuminates the entire surface evenly compared to the edge light method, has been widely used in large displays, but the structure of laminating various optical sheets on the light source has been developed in recent years. In recent years, the edge light system has become mainstream even in large displays (see, for example, Patent Documents 1 to 8).

  Furthermore, as it leads to cost reduction by reducing not only the thickness but also the number of members, the same effect as laminating optical sheets can be obtained by giving predetermined uneven shapes on both the light emitting surface and the anti-light emitting surface. Targeted light guide plates have also been developed. As a method for producing these light guide plates, laser cutting or injection molding has been generally employed in order to accurately form a desired shape. Further, in order to raise the light passing through the surface opposite to the light emitting surface to the light emitting surface side, a method of covering the entire surface or a predetermined shape by printing or vapor deposition of a reflective material is employed.

JP-A-8-212388 JP 2002-109931 A JP 2002-113751 A JP-A-10-28296 JP-A-11-174439 JP 2006-66128 A JP2009-134989A WO2010 / 073726

However, the above-mentioned method cannot cope with an increase in the size of the display, luminance unevenness occurs, and one step for installing the light reflecting portion is necessary after the light guide plate is manufactured, in terms of performance and manufacturing efficiency. It's not enough.
Further, when the screen is enlarged and the light guide distance is increased, there is a problem that the yellowishness of the light emitted from the light guide plate increases.

  The present invention has been made to solve the above-described problems, and can be manufactured with a small number of steps, can efficiently and uniformly start up incident light, and increase the yellowness of emitted light even when the screen is enlarged. An object is to provide a light guide plate that can be suppressed, a backlight unit using the same, and an image display device.

In order to achieve the above object, the invention of claim 1 is characterized in that one surface in the thickness direction is a light emitting surface, the other surface in the thickness direction is a light reflecting surface, and an edge of the light emitting surface is provided. A light-transmitting substrate having at least a part of an end face connecting the edge of the light reflecting surface as a light incident surface, so that light incident from the light incident surface is emitted from the light emitting surface; A light guide plate for guiding light to
A plurality of reflective recesses are formed on the light reflecting surface over the entire surface of the light reflecting surface,
A blue colored light reflecting layer having light scattering reflectivity is formed on the inner surface of each reflecting recess and on the light reflecting surface excluding each reflecting recess.

  According to a second aspect of the present invention, in the light guide plate according to the first aspect, the reflective concave portions are arranged such that the vertical and horizontal pitches of the reflective concave portions decrease as the distance from the light incident surface increases. .

  According to a third aspect of the present invention, in the light guide plate according to the first or second aspect, each of the reflection recesses has an elliptical shape in plan view, and each of the reflection recesses having the elliptical shape in plan view has a long axis of the ellipse having the light axis. It is arranged so that it may become parallel to an entrance plane.

  According to a fourth aspect of the present invention, in the light guide plate according to any one of the first to third aspects, the thickness of the blue colored light reflecting layer is smaller than the depth dimension of the reflective recess.

  According to a fifth aspect of the present invention, in the light guide plate according to any one of the first to fourth aspects, the thickness of the blue colored light reflecting layer is 0.03% or more of the thickness of the light transmissive substrate. .3% or less.

  According to a sixth aspect of the present invention, in the light guide plate according to any one of the first to fifth aspects, a blue colorant is added to the blue colored light reflecting layer at an addition concentration of 10 ppm or more and 200 ppm or less. It is characterized by.

  A seventh aspect of the present invention is the light guide plate according to any one of the first to sixth aspects, wherein the blue colored light reflecting layer has a total light transmittance of 80% or more.

  The invention of claim 8 is characterized in that, in the light guide plate according to any one of claims 1 to 7, a light scattering reflection element is kneaded in the blue colored light reflection layer.

  According to a ninth aspect of the present invention, in the light guide plate according to any one of the first to eighth aspects, an optical path control element for controlling a direction of emitted light is provided on the light emitting surface. .

  The invention of claim 10 is a backlight unit, comprising: the light guide plate according to at least one of claims 1 to 9; and a light source disposed to face the light incident surface of the light guide plate. It is characterized by providing.

  The invention of claim 11 is an image display device comprising the backlight unit according to claim 10 and an image display panel disposed opposite to the light emission side of the backlight unit.

  According to the present invention, a light guide plate that can efficiently start up light incident from a light source than a conventional light guide plate and suppress an increase in yellowness of the emitted light even when the size of the light guide plate is increased, and the emitted light with higher luminance than the conventional light guide plate. It is possible to provide a backlight unit and an image display device that can suppress an increase in yellowness.

It is a cross-sectional schematic diagram which shows an example of the conventional display apparatus. It is a cross-sectional schematic diagram which shows the other example of the conventional display apparatus. It is a cross-sectional schematic diagram which shows an example of the light-guide plate which concerns on this invention. It is the bird's-eye view schematic diagram which looked at the light-guide plate of this invention shown in FIG. 3 from the back surface. It is a cross-sectional schematic diagram which shows the other example of the light-guide plate which concerns on this invention. It is a schematic diagram of the backlight unit which uses the light-guide plate which concerns on this invention. It is a schematic diagram of an image display device using a backlight unit according to the present invention. It is a schematic diagram which shows the example of the light guide in the light guide plate of this invention. It is a schematic diagram which shows the example of the light guide path in the light guide plate which raises light only using refraction. It is a schematic diagram which shows the example of the light guide path in the light guide plate which raises light only using scattered reflection. It is the schematic diagram which showed the spreading | diffusion of light in case a light-scattering reflection layer is thicker than the hollow depth. It is a table | surface which shows the result list of the Example for showing the effect of the light-guide plate which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. The shape will be described with reference to the drawings, but the same reference numerals are given to the constituent elements that exhibit the same or similar functions throughout all the drawings, and redundant descriptions are omitted. Moreover, each figure is a schematic diagram, and the scale of each part does not correspond with the actual.

The light guide plate 14 shown in the present embodiment is a light guide plate used in a display device having an edge type light source, and the light guide plate 14 is adjusted to the contour of the display device as shown in FIGS. A light-transmitting base material 13 having a certain thickness is provided, which has a rectangular shape and is formed of an extruded product made of a thermoplastic resin.
The light transmissive substrate 13 has a light emitting surface 13a on one surface in the thickness direction, a light reflecting surface 13b on the other surface in the thickness direction, and an edge of the light emitting surface 13a. A light incident surface 13c is provided on at least a part of the end face connecting the edge of the light reflecting surface 13b, and light incident from the light incident surface 13c is emitted from the light emitting surface 13a. .

  As shown in FIGS. 3 and 4, the light reflecting surface 13 b of the light transmissive substrate 13 has a plurality of reflections formed by being recessed from the light reflecting surface 13 b in the thickness direction of the light transmissive substrate 13. A recess 11 is formed over the entire surface of the light reflecting surface 13b. And the blue colored light reflection layer 12 which has light-scattering reflectivity is formed in the light reflection surface 13b except the inner surface of each reflection recessed part 11, and each reflection recessed part 11 so that these may be covered.

As shown in FIGS. 3 and 4, the reflective recesses 11 are arranged such that the pitches in the vertical and horizontal directions of the reflective recesses 11 decrease sequentially as the distance from the light incident surface 13 c increases. Furthermore, as shown in FIGS. 3 and 4, the pitches of the reflective concave portions 11 are arranged so that the vertical and horizontal pitches are gradually reduced as the distance from the light incident surface 13c increases, and the depth of the reflective concave portions 11 is the light intensity. It is preferable to have a structure that increases sequentially as the distance from the incident surface 13c increases.
Further, as shown in FIG. 4, each reflecting recess 11 has an elliptical shape in plan view, and each reflecting recess 11 having the elliptical shape in plan view has a major axis of the ellipse parallel to the light incident surface 13c. Is arranged.
In addition, the thickness dimension of the blue colored light reflecting layer 12 is formed to be smaller than the depth dimension of the reflecting recess 11.

  The reason why the blue colored light reflecting layer 12 is provided in the light guide plate 14 configured as described above is that the light incident through the light incident surface 13c from the light source disposed opposite to the side surface of the light guide plate is opposite to the light exit surface 13a. This is because the light that goes in the direction, that is, the light reflecting surface 13b side and does not participate in the luminance of the image display device is directed to the light emitting surface 13a side while adjusting the color.

As shown in FIG. 8, the light that has entered the light-reflecting surface 13 b and has reached the blue-colored light-reflecting layer 12 among the light that has entered from the light-incident surface 13 c and traveled in the direction of the light-reflecting surface 13 b A light that is totally reflected at the interface between the light source 12 and the air and travels away from the light source, a light that is scattered and reflected by the light reflecting element in the blue colored light reflecting layer 12 and is emitted from the light emitting surface 13a, and a light reflecting surface. 13b is broadly divided into those that pass out of the light guide plate 14 through the blue colored light reflecting layer 12.
Further, the light that has been totally reflected and traveled away from the light incident surface 13c is totally reflected at the interface between the blue colored light reflecting layer 12 constituting the light guide plate 14 and the air on the light emitting surface 13a and the light reflecting surface 13b. Repeatedly, the light path is divided into one that advances in the light guide plate 14 and one that changes the optical path in the direction of emission from the light emission surface 13a side by total reflection at the reflection recess 11 provided on the light reflection surface 13b.

  On the other hand, the light that has passed out of the light guide plate 14 is reflected by a reflective film (see FIG. 6 or FIG. 7) provided inside the housing and returned to the light guide plate 14 direction. Thus, by combining the reflection and the scattering, the light from the light source is emitted from the light exit surface 13a, so that the light path changing element provided on the inner surface of each reflection recess 11 and the light reflection surface 13b excluding each reflection recess 11 It is possible to realize the start-up of light with less brightness unevenness than selecting only one of the reflective recess 11 and the light scattering / reflecting element, which are convex on the exit surface 13a side, and eliminate the brightness unevenness of the image display device. Connected.

Moreover, by making the above-mentioned light scattering reflection layer a blue colored light reflection layer, the light toward the light exit surface 13a is bluish, and the increase in the yellowness of the emitted light when the light guide distance is extended is suppressed. Is possible.
Further, as a method of providing the blue colored light reflecting layer 12, when the light guide plate 14 is formed, the light reflecting elements are mixed and formed into a multi-layered integrated structure, so that the blue colored light reflecting layer is formed by printing or vapor deposition after the light guide plate is formed. The number of processes can be reduced as compared with the provision, and the production efficiency can be improved.

  On the other hand, as in the light guide plate 21 shown in FIG. 9, the light is raised only by reflection by the reflective concave portion 11 formed on the light reflecting surface 13b of the light transmissive base 13 and projecting toward the light emitting surface 13a. If it is attempted, the directivity is too strong, leading to uneven brightness, or if the light is launched only with the scattering reflection layer 121 having no reflective recess 11 as in the light guide plate 22 shown in FIG. It is disadvantageous in that it spreads too much and leads to a decrease in front brightness.

  Further, the depth dimension of the reflective recess 11 formed on the light reflecting surface 13b of the light transmissive substrate 13 is smaller than the thickness dimension of the blue colored light reflecting layer 12, that is, the reflective recess 11 reflects the blue colored light. When buried in the layer 12, as shown in the enlarged view of FIG. 11, the light directed toward the reflective recess 11 and the light reflected at the interface of the reflective recess 11 to have directivity are colored blue. The light scattering / reflecting element in the light reflecting layer 12 is diffused too much as indicated by reference numeral 12a, and the light path adjusting function expected for the reflective recess 11 is not fully utilized and the amount of light directed toward the light exit surface 13a is reduced. Since it is disadvantageous in that the luminance is lowered, it is desirable that the depth dimension of the reflective recess 11 is larger than the thickness dimension of the blue colored light reflecting layer 12.

  In this case, the shape and arrangement of the reflective recesses 11 can be arbitrarily set according to a desired luminance distribution. As shown in FIG. 4, the shape of the light transmissive substrate 13 may be an elliptical shape in a concave shape in the thickness direction, or may be a circular shape or a rectangular shape (not shown). It may be a groove shape with As shown in FIGS. 3 and 4, it is desirable that the reflective recesses 11 be arranged so as to become denser as the distance from the light source increases.

  The thickness of the blue colored light reflecting layer 12 needs to be thinner than the depth of the reflecting recess 11 in order to effectively use the optical path change having directivity by the reflecting recess 11 and is sufficient to a position away from the light source. In order to guide light, it is necessary to cause total reflection at the interface between the blue colored light reflection layer 12 constituting the light guide plate 14 and the air. For this purpose, since it is necessary to secure the amount of light that passes through the blue colored light reflecting layer 12, the thickness dimension of the blue colored light reflecting layer 12 is the thickness of the light transmissive substrate 13 (the entire light guide plate 14). The total light transmittance of the blue colored light reflecting layer 12 is desirably 80% or more.

When the thickness of the blue colored light reflecting layer 12 is less than 0.03% of the thickness of the light-transmitting substrate 13, the scattering reflection that changes the optical path on the light exit surface side does not occur sufficiently, and luminance unevenness is not eliminated. It is disadvantageous in terms. Further, when the thickness of the blue colored light reflecting layer 12 exceeds 0.3% of the thickness of the light transmissive substrate 13, the reflective concave portion 11 is buried in the blue colored light reflecting layer, or the light guide plate and the air This is disadvantageous in that the total amount of reflection at the interface is reduced too much, and the amount of light reaching the place far from the light incident surface is reduced, leading to a reduction in luminance and luminance unevenness.
Further, when the total light transmittance of the blue colored light reflecting layer 12 is less than 80%, the blue colored light reflecting layer 12 constituting the light guide plate 14 and air, as in the case where the blue colored light reflecting layer 12 is too thick. This is disadvantageous in that the amount of light guided using the total reflection at the interface of the film becomes insufficient, leading to a decrease in brightness and uneven brightness.

  Furthermore, in the blue coloring of the blue colored light reflecting layer 12 that leads to the adjustment of the color of the emitted light, it is desirable to add a blue colorant to an additive concentration of 10 ppm to 200 ppm. This is for the purpose of blue coloring to suppress the yellowness increase of the emitted light, and if the addition concentration is within the above range, the blueness of the light reflected by the blue colored light reflecting layer 12 will enter the light guide plate. This is because, in combination with the color change that the yellowish color becomes stronger as the light travels, it leads to whitening of the emitted light. If the additive concentration is less than 10 ppm, the influence of yellowishness cannot be canceled out, and if the additive concentration is more than 200 ppm, the emitted light is disadvantageous in that it becomes too blue. Examples of the blue colorant include copper phthalocyanine.

  About the light emission surface 13a of the light transmissive base material 13 which comprises a light-guide plate, it is sufficient to shape | mold to a substantially flat surface and to use the usage which laminates | stacks various optical sheets as needed. For example, as shown in FIG. 5, an optical path control element 15 having an arbitrary shape is provided on the light emission surface, for example, an optical path control element 15 made of a lenticular lens or the like is provided on the light emission surface of the light transmissive substrate 13. You may provide the optical path change function from which desired optical performance is obtained. Further, an optical path control element having an arbitrary shape may be provided on the light emission surface, and an optical sheet may be further laminated to supplement the function.

  In addition, from the viewpoint of cost reduction, reduction of the backlight unit and image display device thickness, and reduction of the number of members that lead to reduction of assembly work load of the backlight unit and image display device, the optical path control having an optical path changing function on the light emission surface It is preferred to provide additional elements and provide additional optical sheets only when necessary to meet the desired optical performance.

  Examples of the material of the light guide plate according to the present invention include acrylic resin, polystyrene (PS) resin, methacryl styrene copolymer (MS) resin, polycarbonate (PC) resin, acrylonitrile styrene copolymer (AS) resin, cyclohexane. An olefin polymer (COP) can be used.

Next, an embodiment in which a backlight unit is configured using the edge light type light guide plate 14 configured as described above will be described with reference to FIG.
As shown in FIG. 6, the backlight unit 18 includes a light guide plate 14 having an optical path control element 15, and a light source disposed so as to face the light incident surface 13 c of the light-transmitting base material 13 constituting the light guide plate 14. 16 and a housing 17 that houses the light guide plate 14 and covers the light source 16 so as to cover the outer periphery of the light guide plate 14 except for the light exit surface side of the optical path control element 15. A reflection film (not shown) is provided on the inner surface of the housing 17.
As the light source, a linear light source such as CCFL may be used, or a point light source such as an LED (Light Emitting Diode) may be used side by side.

Next, an embodiment in which the image display device 20 is configured using the backlight unit configured as described above will be described with reference to FIG.
As shown in FIG. 7, the image display device 20 includes the backlight unit 18 shown in FIG. 6 and the optical path control element 15 of the light guide plate 14 in the opening 17 a of the casing 17 that constitutes the backlight unit 18. And an image display panel 19 disposed opposite to each other.

  In order to show the effect of the present invention, PMMA resin was used for extrusion molding to produce a light guide plate having a thickness of 3 mm and a size of 40 inches. In this case, the light exit surface is substantially flat, and the light incident surface of the light guide plate is formed with a lenticular lens extending in a direction perpendicular to the light incident surface, and the light reflection surface of the light guide plate is formed. A reflection concave portion having an elliptical shape in plan view in which the major axis is arranged in parallel with the light incident surface is formed to a depth of 20 μm.

  A multilayer extruder is used to extrude the light guide plate, and the inner surface of the reflective recess and the light reflecting surface excluding this are made of titanium dioxide as a light reflecting element and added with a blue colorant (PMMA resin). The blue colored light-scattering / reflecting layer to be formed was integrally formed by an embossing method using a mold. In this case, various conditions were examined using the concentration of the blue colorant and the thickness of the light reflecting layer as variable parameters.

  The light guide plate thus produced was replaced with a light guide plate mounted on an existing liquid crystal television, and each sample was compared. Each evaluation at this time was performed according to the following criteria.

Luminance: ◯ if a luminance higher than the front luminance of the light guide plate (backside dot printing) mounted on the existing television is obtained, Δ if it is equivalent to the light guide plate mounted on the existing television, and × if not obtained.
Luminance unevenness: ◯ when light / dark unevenness is not visually recognized on the entire screen, Δ when light / dark unevenness is confirmed to be weak, and × when visually recognized.
Color change: Yes, if the yellow light is suppressed more than the light emitted from the light guide plate installed on the existing TV. △ (1) when there is no, △ (2) when there is a bluish but suppressed yellow, x if equal or more.

As is clear from the table shown in FIG. 12, the blue colored light reflection having a thickness that is thinner than the depth of the depression and the depression and is within the range of 0.03% to 0.3% of the total thickness on the reflection light exit surface of the light guide plate. By providing the layer, it is possible to provide a display which exhibits uniform and high luminance. Furthermore, it was confirmed that an increase in yellowness of the emitted light can be suppressed by adding a blue colorant to the blue colored light reflecting layer at a concentration in the range of 10 ppm to 200 ppm.
This tendency was the same regardless of whether the light exit surface was a substantially flat surface or a lenticular lens shape, but the effect of improving the luminance and avoiding luminance unevenness was higher when the lenticular lens shape was provided on the surface.

By using the light guide plate according to the present invention, it is possible to efficiently raise the light incident from the edge light type light source and the light whose color is adjusted with directivity to the light exit surface side, It is possible to provide an image display that is more uniform and has a higher luminance than a conventional one and a change in color tone is suppressed.
In addition, since the blue colored light reflecting layer is integrally formed, there is no need to add a blue colored light reflecting layer by printing or vapor deposition after the light guide plate is formed, leading to a reduction in the number of manufacturing processes, which can improve manufacturing efficiency. Become.

DESCRIPTION OF SYMBOLS 1 ... Polarizing plate, 2 ... Liquid crystal panel, 3 ... Polarizing plate, 4 ... Diffusing film, 5 ... Reflector, 6 ... Light source lamp, 7 ... Light guide plate, 8 ... Reflecting film, 9 ... Prism film (stretching direction side), 10 DESCRIPTION OF SYMBOLS ... Prism film (stretching direction vertical | vertical), 11 ... Reflection recessed part, 12 ... Blue colored light reflection layer, 13 ... Light transmissive base material, 13a ... Light emission surface, 13b ... Light reflection surface, 13c ... Light incident surface, 14 ... Light guide plate, 15 ... optical path control element, 16 ... light source, 17 ... housing, 18 ... backlight unit, 19 ... image display panel.

Claims (11)

One surface in the thickness direction is a light emitting surface, the other surface in the thickness direction is a light reflecting surface, and at least one of end surfaces connecting the edge of the light emitting surface and the edge of the light reflecting surface A light guide plate having a light transmissive substrate having a light incident surface as a part, and guiding light so that light incident from the light incident surface is emitted from the light emitting surface,
A plurality of reflective recesses are formed on the light reflecting surface over the entire surface of the light reflecting surface,
A blue colored light reflecting layer having light scattering reflectivity is formed on the inner surface of each reflecting recess and the light reflecting surface excluding each reflecting recess,
A light guide plate characterized by that.   The light guide plate according to claim 1, wherein the reflective recesses are arranged such that a pitch in the vertical and horizontal directions of the reflective recesses decreases as the distance from the light incident surface increases.   Each of the reflecting recesses has an elliptical shape in plan view, and each of the reflecting recesses having the elliptical shape in plan view is arranged so that the major axis of the ellipse is parallel to the light incident surface. Item 3. The light guide plate according to Item 1 or 2.   The light guide plate according to any one of claims 1 to 3, wherein a thickness dimension of the blue colored light reflecting layer is smaller than a depth dimension of the reflective recess.   The thickness of the blue colored light reflecting layer is 0.03% or more and 0.3% or less of the thickness of the light transmissive base material, according to any one of claims 1 to 4. Light guide plate.   The light guide plate according to any one of claims 1 to 5, wherein a blue colorant is added to the blue colored light reflecting layer at an addition concentration of 10 ppm or more and 200 ppm or less.   The light guide plate according to claim 1, wherein a total light transmittance of the blue colored light reflecting layer is 80% or more.   The light guide plate according to any one of claims 1 to 7, wherein a light scattering reflection element is kneaded in the blue colored light reflection layer.   The light guide plate according to any one of claims 1 to 8, wherein an optical path control element for controlling a direction of emitted light is provided on the light emitting surface. The light guide plate according to claim 1, and a light source disposed to face the light incident surface of the light guide plate.
Backlight unit characterized by that. The backlight unit according to claim 10, and an image display panel disposed to face the light emission side of the backlight unit.
An image display device characterized by that.

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