JP2014029417A - Light guide plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide plate capable of suppressing a change in color tone of light penetrating through the light guide plate and suppressing lowering of transmissivity, and provide a surface light source device and a transmissive image display device which include the light guide plate, and an optical sheet.SOLUTION: A transmissive image display device 1 comprises a light guide plate 30, a light source part 22 and a transmissive image display part 10. The light guide plate 30 is composed of translucent resin, and comprises: a side surface 31a into which light is made incident; a reflection surface 31d which intersects with the side surface 31a and includes reflection dots 32 for reflecting light; an emission surface 31c opposite to the reflection surface 31d and emitting light. The light guide plate has an ultraviolet absorber having an addition amount of 50 mass ppm or less for the translucent resin. The light source part 22 is arranged facing the side surface 31a of the light guide plate 30 and supplies light to the side surface 31a. The transmissive image display part 10 is arranged on an emission surface 31c side of the light guide plate 30 and is irradiated with the emission light from the light guide plate 30 to thereby display an image.

Description

  The present invention relates to a light guide plate, a surface light source device and a transmissive image display device including the same, and an optical sheet.

  2. Description of the Related Art A transmissive image display device such as a liquid crystal display device generally includes a surface light source device that is disposed on the back side of a transmissive image display unit such as a liquid crystal display panel and supplies light to the transmissive image display unit. As such a surface light source device, an edge light type surface light source device is known. The edge light type surface light source device includes a light-transmitting light guide plate and a light source disposed on the side of the light guide plate for supplying light to the side surface of the light guide plate. In a light guide plate formed of a light-transmitting resin, an ultraviolet absorber is added to suppress deterioration due to ultraviolet rays emitted from a light source or the like (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2004-144813

  However, when an ultraviolet absorber is added to the translucent resin forming the light guide plate, the light guide plate becomes yellowish depending on the color of the ultraviolet absorber itself. In the light guide plate in the transmissive image display device and the surface light source device, the light emitted from the light source enters the end surface of the light guide plate, and the optical path from the light exiting surface becomes longer. For this reason, the light which permeate | transmits a light-guide plate becomes easy to receive to the influence of yellowishness, and there exists a possibility that the change of a hue may arise. Moreover, there exists a possibility that the transmittance | permeability may fall with the ultraviolet absorber added to translucent resin.

  Accordingly, a main object of the present invention is to provide a light guide plate capable of suppressing a change in hue of light transmitted through the light guide plate and suppressing a decrease in transmittance, a surface light source device including the light guide plate, and a transmissive image display. An apparatus and an optical sheet are provided.

  The light guide plate according to the present invention is a light guide plate made of a translucent resin, and is an incident surface on which light is incident and a surface that intersects the incident surface, and is provided with a reflecting portion that reflects light And a light-exiting surface that is opposite to the reflecting surface and emits light, and the amount of the ultraviolet absorber added to the translucent resin is 50 ppm by mass or less.

  A surface light source device according to the present invention includes the light guide plate described above, and a light source unit that is disposed to face an incident surface of the light guide plate and supplies light to the incident surface.

  A transmissive image display device according to the present invention is arranged above the light guide plate described above, an incident surface of the light guide plate, a light source unit that supplies light to the incident surface, and an output surface side of the light guide plate And a transmissive image display unit that is illuminated by light emitted from the light guide plate and displays an image.

  In the light guide plate, the surface light source device, and the transmissive image display device configured as described above, the light incident from the incident surface of the light guide plate propagates while totally reflecting inside the light guide plate. When light propagating in the light guide plate is incident on the reflection portion provided on the reflection surface, the light is reflected by the reflection portion under conditions different from the total reflection conditions. Therefore, the light reflected by the reflecting portion is emitted from the emission surface. In the light guide plate, since the amount of the ultraviolet absorber added to the translucent resin is 50 ppm by mass or less, the influence of the yellow color received from the time when it enters the light incident surface until it is emitted to the light output surface is suppressed. . Thereby, while suppressing the change of the hue of the light which permeate | transmits a light-guide plate, the fall of the transmittance | permeability can be suppressed. In the surface light source device including the light guide plate, light having a natural hue and high luminance can be supplied to the transmissive image display unit. In the transmissive image display apparatus supplied with such light, the image displayed on the transmissive image display unit can be of higher quality.

  In the light guide plate according to the present invention, the length of the diagonal line on the exit surface can be 50 cm or more.

  In the light guide plate to which the ultraviolet absorber is added, the longer the diagonal length of the reflecting surface, the longer the optical path length of the light transmitted through the light guide plate, and the yellowishness of the emitted light becomes conspicuous. In this invention, the influence of the yellowishness by the ultraviolet absorber itself which was conspicuous with the large sized light-guide plate can be suppressed.

  In the light guide plate according to the present invention, the translucent resin can be a polystyrene resin or a methyl methacrylate / styrene copolymer resin.

  Since the polystyrene resin or the methyl methacrylate / styrene copolymer resin has a relatively low hygroscopic property, a change in shape due to moisture absorption is suppressed. Thereby, a favorable emission state can be maintained. In addition, in manufacturing the light guide plate, the cost for the material can be reduced.

  The light guide plate according to the present invention can be used as a light guide plate for a white light emitting diode in which light from a white light emitting diode as a light source is incident on an incident surface.

  The wavelength of ultraviolet light that causes deterioration of the translucent resin is 290 to 400 nm. For this reason, in order to reduce deterioration of translucent resin, it is desired to cut the light whose upper limit of wavelength is about 410 nm. On the other hand, the wavelength of light emitted from the white light emitting diode is 400 nm or more. Therefore, in the conventional light guide plate in which measures against deterioration due to ultraviolet rays are taken, light in the wavelength region of 400 nm to 410 nm included in the light emitted from the white light emitting diode is also cut. As a result, it has been found that the emission intensity is reduced by about 5%, which causes a further reduction in luminance. In the light guide plate having the above configuration, even when light from the white light emitting diode is incident, light having a wavelength in the region of 400 nm to 410 nm peculiar to the white light emitting diode is not cut. The effect of suppressing the decrease is further increased.

  In the light guide plate according to the present invention, the amount of the fluorescent whitening agent added to the translucent resin can be 0 mass ppm or more and 10 mass ppm or less.

  According to the light guide plate having this configuration, since the ultraviolet absorber is added as described above, it is possible to reduce the amount of the fluorescent whitening agent for suppressing yellowing due to the ultraviolet absorber. Thereby, since the fall of the transmittance | permeability by adding a fluorescent whitening agent is suppressed, the brightness | luminance of the light radiate | emitted from a light-guide plate can be improved.

  The light guide plate according to the present invention can be used as a light guide plate for a color liquid crystal display device that illuminates a color liquid crystal display panel as a transmissive image display unit with light emitted from an emission surface.

  According to the light guide plate having this configuration, the transmissive image display is irradiated with light in which the influence of yellowishness is suppressed. As a result, the image displayed on the transmissive image display unit can be of higher quality.

  An optical sheet according to the present invention is an optical sheet made of a light-transmitting resin and used for a light guide plate, and is an incident surface on which light is incident, a surface intersecting the incident surface, and a reflecting part that reflects light And a light-exiting surface on the side opposite to the reflective surface, and the amount of the ultraviolet absorber added to the translucent resin is 50 mass ppm or less.

  The optical sheet having the above configuration functions as a light guide plate by providing a reflection portion on one surface (reflection surface) of the optical sheet. At this time, the light incident from the incident surface of the optical sheet propagates while being totally reflected in the optical sheet. When the light enters the reflection portion, the light is reflected by the reflection portion under conditions different from the total reflection conditions. Therefore, the light reflected by the reflecting portion is emitted from the emission surface. In the optical sheet, since the amount of the UV absorber added to the translucent resin is 50 ppm by mass or less, it is possible to suppress the influence of the yellow color that is received between the incident on the incident surface and the emergence on the emitting surface. Can do. Moreover, since the addition amount of the ultraviolet absorber with respect to translucent resin is 50 mass ppm or less, it can suppress that a light transmittance falls.

  According to the light guide plate, the surface light source device and the transmissive image display device including the same, and the optical sheet according to the present invention, the influence of yellowishness on the light transmitted through the light guide plate is suppressed, and the decrease in luminance is suppressed. It becomes possible to do.

It is a schematic diagram which shows schematic structure of the transmissive image display apparatus to which one Embodiment of the light-guide plate which concerns on this invention is applied. It is the schematic block diagram which showed one Embodiment of the manufacturing apparatus which manufactures the light-guide plate original plate used as the light-guide plate shown in FIG. It is the schematic block diagram which showed one Embodiment of the manufacturing apparatus which forms a reflection part in the light-guide plate original plate manufactured with the manufacturing apparatus shown in FIG. It is the graph which showed the spectrum distribution of the light which white LED radiate | emits, and the area | region of the wavelength which an ultraviolet absorber cut | disconnects, and the graph which expanded and showed the light intensity in the wavelength vicinity of 400 nm.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or an equivalent element, and the overlapping description is abbreviate | omitted. Further, the dimensional ratios in the drawings do not necessarily match those described. Further, in the description, words indicating directions such as “up” and “down” are convenient words based on the state shown in the drawings. FIG. 1 is a schematic diagram showing a schematic configuration of a transmissive image display device to which an embodiment of a light guide plate according to the present invention is applied, and shows the transmissive image display device in an exploded manner.

  The transmissive image display device 1 includes a transmissive image display unit 10 and a surface light source device 20 that outputs planar light to be supplied to the transmissive image display unit 10. Hereinafter, for convenience of explanation, as shown in FIG. 1, the direction in which the transmissive image display unit 10 is arranged with respect to the surface light source device 20 is referred to as a Z-axis direction or a front direction. Two directions orthogonal to the Z-axis direction are referred to as an X-axis direction and a Y-axis direction. The X-axis direction and the Y-axis direction are orthogonal to each other.

  The transmissive image display unit 10 displays an image by being illuminated with planar light emitted from the surface light source device 20. An example of the transmissive image display unit 10 is a color liquid crystal display panel as a polarizing plate bonding body in which polarizing plates 12 and 13 are disposed on both surfaces of a liquid crystal cell 11. In this case, the transmissive image display device 1 is a color liquid crystal display device (or color liquid crystal television). As the liquid crystal cell 11 and the polarizing plates 12 and 13, those used in a transmissive image display device such as a conventional liquid crystal display device can be used. Examples of the liquid crystal cell 11 are a TFT (Thin Film Transistor) type liquid crystal cell, an STN (Super Twisted Nematic) type liquid crystal cell, and the like.

  The surface light source device 20 is an edge light type backlight unit that supplies light to the transmissive image display unit 10. The surface light source device 20 includes a light guide plate 30 and a light source unit 22 arranged to face one side surface (incident surface) 31 a of the light guide plate 30.

  The light source unit 22 may be a plurality of point light sources arranged in a line shape (arranged in the Y-axis direction in FIG. 1). An example of the point light source is a white light emitting diode (hereinafter also referred to as “white LED”). The light source unit 22 may include a reflector 23 as a reflection unit that reflects light on the side opposite to the direction in which the light guide plate 30 is disposed in order to efficiently make light incident on the side surface 31 a of the light guide plate 30. Good. The light source unit 22 may be a linear light source such as a cold cathode fluorescent lamp (CCFL).

  The light source of the surface light source device 20 is not limited to a white LED (Light Emitting Diode) but may be other LEDs. Further, as the light source of the surface light source device 20, a plurality of LEDs may be arranged in one place to constitute one light source unit. For example, as one light source unit, LEDs of three colors different in red, green, and blue may be arranged close to each other. And the light source unit which has several LED is discretely arrange | positioned according to the arrangement | positioning direction mentioned above. In such a case, it is preferable that different LEDs are arranged as close as possible.

  As white LED used as the light source part 22, what has various light emission distribution can be used. It is preferable that the light intensity distribution in the normal direction is the maximum and the light emission distribution has a full width at half maximum of 40 degrees or more and 80 or less. Specific examples of the LED type include a Lambertian type, a shell type, and a side emission type.

  The transmissive image display device 1 may have a configuration in which various optical members 40 are disposed between the light guide plate 30 and the transmissive image display unit 10. Examples of the various optical members 40 include a reflective polarization separation sheet, a light diffusion sheet, a brightness enhancement sheet, a microlens sheet, a lenticular lens sheet, a prism sheet, and the like. Or they can be arranged in combination.

  The surface light source device 20 may include a reflection plate 25 located on the opposite side of the light transmission plate 30 from the transmissive image display unit 10. The reflection plate 25 is for causing the light emitted from the light guide plate 30 to the reflection plate 25 side to enter the light guide plate 30 again. The reflector 25 may be in the form of a sheet as shown in FIG. Further, the reflection plate 25 may be a bottom surface of the housing of the surface light source device 20 that houses the light guide plate 30 and that is mirror-finished.

  The light guide plate 30 is used to emit light emitted from the light source unit 22 toward the transmissive image display unit 10. The light guide plate 30 is formed in a plate shape. Examples of the planar view shape of the light guide plate 30 include a substantially rectangular shape and a substantially square shape. The size of the planar view shape of the light guide plate 30 is selected so as to match the target screen size of the transmissive image display unit 10. The size of the light guide plate 30 is usually 270 mm × 480 mm or more and 1250 mm × 2220 mm or less, and preferably 390 mm × 700 mm or more. Further, the length of the diagonal line of the light guide plate 30 is usually 50 cm or more and 250 cm or less, and preferably 80 cm or more. Further, the thickness T of the light guide plate 30 is usually 0.5 mm or more and 4.0 mm or less, and can be set to 2 mm, for example.

  The light guide plate 30 is mainly composed of a translucent resin (or transparent resin). Examples of the refractive index of the translucent resin are 1.46 to 1.62. Examples of the translucent resin material are polystyrene (PS) resin (refractive index: 1.59), MS resin (methyl methacrylate-styrene copolymer) resin (refractive index: 1.56-1.59), poly Methyl methacrylate (PMMA) resin (refractive index: 1.49), polycarbonate resin (refractive index: 1.59), AS resin (acrylonitrile-styrene copolymer resin) (refractive index: 1.56-1.59) An acrylic ultraviolet curable resin (refractive index: 1.46 to 1.58), a cycloolefin resin (refractive index: 1.51 to 1.55), and the like. As the translucent resin material, polystyrene resin and MS resin are more preferable from the viewpoint of hygroscopicity and cost.

  The light guide plate 30 is added with an ultraviolet absorber for reducing deterioration due to ultraviolet rays. In this embodiment, there is one feature in the addition amount of the ultraviolet absorber. That is, the addition amount of the ultraviolet absorber with respect to the translucent resin constituting the light guide plate 30 is 50 mass ppm or less, preferably 10 mass ppm or less. For example, in the case of a light guide plate 30 for a 40-inch display having a size of 514 mm × 904 mm and a diagonal length of 104 cm, the addition amount of the ultraviolet absorber relative to the translucent resin can be 0 mass ppm. .

  Examples of the ultraviolet absorber added to the translucent resin include, for example, a benzotriazole ultraviolet absorber, a benzophenone ultraviolet absorber, a cyanoacrylate ultraviolet absorber, a malonic ester ultraviolet absorber, and an oxalic anilide ultraviolet absorber. Agents, triazine ultraviolet absorbers, and the like, preferably benzotriazole ultraviolet absorbers and triazine ultraviolet absorbers.

  Moreover, since the ultraviolet absorber is used as the above-mentioned addition amount, the addition amount of the fluorescent whitening agent for suppressing the yellowness due to the ultraviolet absorber can be reduced. Thereby, since the fall of the transmittance | permeability by adding a fluorescent whitening agent is suppressed, the brightness | luminance of the light radiate | emitted from a light-guide plate can also be improved.

  Further, additives such as an antistatic agent, an antioxidant, a processing stabilizer, a flame retardant, and a lubricant can be added to the light guide plate 30 without departing from the spirit of the present invention. These additives can be used alone or in combination of two or more.

  When there is an additive added to the translucent resin, such as the above-mentioned additive, the addition amount of the ultraviolet absorber is a combination of the translucent resin constituting the light guide plate 30 and the other additive. It is determined with respect to the mass, and the addition amount is 50 mass ppm or less. The same applies to the concept of the amount of fluorescent brightener added.

  As shown in FIG. 1, the light guide plate 30 is opposite to the optical member 40 and has a light-emitting surface 31 c formed substantially flat and a back surface (reflective surface) on which a plurality of reflective dots (reflective portions) 32 described later are formed. ) 31d and four side surfaces 31a, 31b, 31e, and 31f intersecting the exit surface 31c and the back surface 31d. In FIG. 1, two side surfaces 31a and 31b facing each other in the X-axis direction are shown, and two side surfaces 31e and 31f facing each other in the Y-axis direction are shown. FIG. 1 shows a state in which the side surface 31a and the side surface 31b are substantially orthogonal to the output surface 31c and the back surface 31d as an example of the arrangement relationship between the side surface 31a and the side surface 31b and the output surface 31c and the back surface 31d. In the present embodiment, the other side surfaces 31e and 31f of the light guide plate 30 are also orthogonal to the exit surface 31c and the back surface 31d.

  Reflective dots 32 that diffusely reflect light are formed on the back surface 31 d of the light guide plate 30. The reflective dots 32 are arranged in a predetermined dot pattern. In the dot pattern, the arrangement is such that the distance between the adjacent reflective dots 32 becomes closer as the distance from the light source unit 22 increases, or the size (diameter) of the reflective dots 32 increases as the distance from the light source unit 22 increases. Is included. In FIG. 1, the example of arrangement | positioning of the reflective dot 32 formed so that a diameter may become large as it distances from a light source is shown. Further, examples of the shape of the reflective dot 32 include a substantially circular shape, a substantially dotted shape, and a substantially rectangular shape.

  The method of forming the reflective dots 32 includes, for example, a method of performing ink jet printing, a method of screen printing, or a method of depositing ink having diffusion particles that diffuse light.

  The exit surface 31c of the light guide plate 30 is a flat surface. Note that the light exit surface 31c of the light guide plate 30 may have a slight surface layer diffusion to reduce moire and the like.

[Production method of light guide plate]
Next, an example of the manufacturing method of the light-guide plate which concerns on this embodiment is demonstrated using FIG.2 and FIG.3. FIG. 2 is a schematic configuration diagram showing an embodiment of an apparatus for manufacturing a light guide plate original plate to be a light guide plate. FIG. 3 is a schematic configuration diagram showing an embodiment of an apparatus for forming reflective dots on a light guide plate original plate manufactured by the manufacturing apparatus shown in FIG. The light guide plate 30 as shown in FIG. 1 is manufactured by forming the reflective dots 32 by the device 70 on the light guide plate original plate (optical sheet) 30A manufactured by the device 60 shown in FIG. First, an apparatus (light guide plate original plate manufacturing apparatus) 60 for manufacturing a light guide plate original plate 30A to be the light guide plate 30 will be described.

  As shown in FIG. 2, the light guide plate original plate manufacturing apparatus 60 includes a resin inlet 61 for introducing a thermoplastic resin as a raw material, an extruder 62 for heating and melting the thermoplastic resin, and an extruder 62. A die 63 for extruding the supplied molten resin into a sheet shape, and a first pressing roll 64, a second pressing roll 65, and a third pressing roll 66 for forming a sheet-shaped resin sheet 80 extruded from the die 63. And a cutter 68 for cutting the resin sheet 80 into a predetermined size along the width direction (direction orthogonal to the extrusion direction).

  As for the 1st press roll 64, the 2nd press roll 65, and the 3rd press roll 66, the rotating shaft of each roll is arrange | positioned substantially parallel. The 1st press roll 64 and the 2nd press roll 65, the 2nd press roll 65, and the 3rd press roll 66 are mutually spaced apart in the thickness direction of the resin sheet 80, and the interval between each peripheral surface is as follows. It is set according to the thickness of the resin sheet 80. The peripheral surfaces 64a to 66a of the first to third pressing rolls 64 to 66 are mirror surfaces.

  In such a light guide plate original plate manufacturing apparatus 60, for example, a polystyrene resin as a thermoplastic resin and a benzotriazole-based compound as an ultraviolet absorber are charged into the resin inlet 61. Next, the polystyrene resin mixed with the ultraviolet absorber is melt-kneaded in the extruder 62 and supplied to the die 63. In the die 63, the molten resin supplied from the extruder 62 is extruded as a resin sheet 80. Next, the resin sheet 80 is sandwiched and pressed between the first pressing roll 64 and the second pressing roll 65, and then the resin sheet 80 is sandwiched and pressed between the second pressing roll 65 and the third pressing roll 66. As a result, the resin sheet 80 having a flat surface and a desired thickness is formed. Then, by cutting to a desired size by the cutter 68, the light guide plate original plate 30A having a desired thickness and size is obtained. In the thus formed light guide plate original plate 30A, the reflective dots 32 are formed on the back surface.

  Next, an apparatus (reflective dot forming apparatus) 70 that forms the reflective dots 32 on the surface that becomes the back surface of the light guide plate original plate 30A will be described. The reflective dot forming apparatus 70 shown in FIG. 3 includes a transport unit 71 that transports the light guide plate original plate 30A, an inkjet head 72 that drops ink onto the light guide plate original plate 30A, and a UV lamp 73 that cures the dropped ink. ing.

  In such a reflective dot forming apparatus 70, the light guide plate original plate 30 </ b> A is continuously or intermittently conveyed along the direction A by the conveying means 71. On the surface S of the light guide plate original plate 30A, ink droplets are printed in a dot pattern by the inkjet head 72 supported by the support portion 72A. For example, as shown in FIG. 1, the pattern printing can be performed so that the diameter of the reflective dot 32 increases as the distance from the side surface 31 a serving as the incident surface increases.

  The ink used to form the reflective dots 32 can be an ultraviolet curable ink containing a pigment, a photopolymerizable component, and a photopolymerization initiator. A photoinitiator can be suitably selected from what is normally used in the field | area of an ultraviolet curable resin. The printed ink is cured in the region 73B by the UV lamp 73 supported by the support portion 73A. Thereby, the reflective dots 32 made of the cured ink are formed. In this way, the light guide plate 30 is manufactured.

  Next, the operation and effect of the light guide plate 30 will be described by taking as an example the case where the surface light source device 20 including the light guide plate 30 is applied to the transmissive image display device 1 as shown in FIG. In the light guide plate 30, the surface light source device 20, and the transmissive image display device 1 of the above-described embodiment, the light (arrows in FIG. 1) incident from the side surface 31 a that is the incident surface of the light guide plate 30 is totally reflected in the light guide plate 30. Propagate while. When light propagating in the light guide plate 30 enters the reflective dots 32 provided on the back surface 31d, the light is reflected by the reflective dots 32 under conditions different from the total reflection conditions. Therefore, the light reflected by the reflective dots 32 is emitted from the emission surface 31c. Thus, since the light passing through the light guide plate has a long optical path length, even a slight coloration of the resin is easily affected. Therefore, it is necessary not to make the yellowish appearance of the light guide plate a problem, but to make the yellowishness received by the transmitted light a problem. The inventors of the present application paid attention to this problem and found the amount of the ultraviolet absorber added to the translucent resin. That is, in the light guide plate 30, since the amount of the ultraviolet absorber added to the translucent resin is 50 ppm by mass or less, it is affected by the yellow color that is received between the incident on the side surface 31 a and the emitted surface 31 c. Is suppressed. Thereby, while suppressing the change of the hue of the light which permeate | transmits the light-guide plate 30, the fall of the transmittance | permeability can be suppressed. The surface light source device 20 including the light guide plate 30 can supply light having a natural hue and high brightness to the transmissive image display unit 10. In the transmissive image display device 1 to which such light is supplied, the image displayed on the transmissive image display unit 10 can be of higher quality.

  Furthermore, in the transmissive image display device 1 having the above-described configuration, when a white LED is applied as the light source unit 22, that is, when the light from the white LED is incident on the light guide plate 30, the effect becomes large. This will be described with reference to (a) and (b). 4A is a graph showing the spectral distribution of the light emitted from the white LED and the wavelength region blocked by the UV absorber, and FIG. 4B shows the light intensity with the wavelength around 400 nm enlarged. It is a graph.

  The wavelength of ultraviolet light that causes deterioration of the translucent resin is 290 to 400 nm. For this reason, as shown in FIG. 4, it is desired to cut light having an upper limit of wavelength up to about 410 nm in order to suppress deterioration of the translucent resin forming the light guide plate 30. On the other hand, the wavelength of light emitted from the white LED is 400 nm or more as shown in FIG. Therefore, in the conventional light guide plate in which measures against deterioration by ultraviolet rays are taken, light in the wavelength region of 400 nm to 410 nm included in the light emitted from the white LED is also cut. As a result, it has been found that the emission intensity is reduced by about 5%, which further reduces the luminance. In this regard, in the light guide plate 30 of the above-described embodiment, even when light from the white LED is incident, light having a wavelength in the region of 400 nm to 410 nm unique to the white LED is not cut. Therefore, the effect of suppressing the decrease in luminance is further increased.

  As mentioned above, although one Embodiment and one Example of this invention were demonstrated, this invention is not limited to the said embodiment and Example, A various change is possible in the range which does not deviate from the meaning of invention.

  In the said embodiment, although the example of light-guide plate original plate 30A manufacture by extrusion molding was given and demonstrated using the manufacturing apparatus as shown in FIG. 2, this invention is not limited to this. For the light guide plate original plate 30A, a method of obtaining a light guide plate original plate 30A having an arbitrary shape by filling a mold or a mold with a resin using a hot press molding machine, an injection molding machine, or the like.

  In the said embodiment, although the ink was dripped at the back surface 31d used as the reflective surface of light-guide plate original plate 30A, the example which forms the reflective dot (reflective part) 32 by hardening the said ink was demonstrated, this invention is described. It is not limited to this. For example, the reflecting portion can be formed by cutting the light guide plate original plate 30A manufactured by extrusion molding or drawing a dot using a laser. In the manufacturing apparatus as shown in FIG. 2, for example, a transfer mold in which a recess is formed on the peripheral surface of the second pressing roll 65 is provided, and the shape of the transfer mold is transferred to one surface of the resin sheet 80. Good. Thereby, a convex portion as a reflective portion is formed on one surface of the resin sheet 80.

  In the above-described embodiment, an example in which dots are formed as reflecting portions for irregularly reflecting light has been described. However, the present invention is not limited to this, and for example, a concave portion or a convex portion may be formed in a stripe shape. it can.

  In the above embodiment, the example in which the light source unit 22 is disposed at a position facing the one side surface 31a of the light guide plate 30 has been described. However, the present invention is not limited to this. For example, the light source unit 22 may be disposed at a position facing each of the two side surfaces 31 a and 31 b facing each other in the light guide plate 30. In this case, based on the distance from the side surfaces 31a and 31b where light is incident from the light source unit 22, the reflection unit is appropriately arranged.

  DESCRIPTION OF SYMBOLS 1 ... Transmission type image display apparatus, 10 ... Transmission type image display part, 11 ... Liquid crystal cell, 12, 13 ... Polarizing plate, 20 ... Surface light source device, 22 ... Light source part, 23 ... Reflector, 25 ... Reflecting plate, 30 ... Light guide plate, 30A ... Light guide plate original plate, 31a ... Side surface (incident surface), 31b, 31e, 31f ... Side surface, 31c ... Exit surface, 31d ... Back surface (reflective surface), 32 ... Reflective dots (reflective portion), 40 ... Optical 60, light guide plate manufacturing apparatus, 61 ... resin inlet, 62 ... extruder, 63 ... die, 64 ... first pressing roll, 65 ... second pressing roll, 66 ... third pressing roll, 68 ... cutter, 70: reflective dot forming device, 71: conveying means, 72: inkjet head, 73: UV lamp, 80: resin sheet.

Claims (9)

A light guide plate made of translucent resin,
An incident surface on which light is incident;
A reflecting surface provided with a reflecting portion that is a surface intersecting the incident surface and reflects the light;
An exit surface that is opposite to the reflecting surface and emits the light;
With
The amount of the ultraviolet absorber added to the translucent resin is 50 mass ppm or less,
Light guide plate. The length of the diagonal line on the exit surface is 50 cm or more,
The light guide plate according to claim 1. The translucent resin is a polystyrene resin or a methyl methacrylate / styrene copolymer resin.
The light guide plate according to claim 1 or 2. Used as a light guide plate for a white light emitting diode, in which light from a white light emitting diode as a light source is incident on the incident surface.
The light-guide plate as described in any one of Claims 1-3. The amount of fluorescent brightener added to the translucent resin is 0 mass ppm or more and 10 mass ppm or less.
The light-guide plate as described in any one of Claims 1-4. Used as a light guide plate for a color liquid crystal display device, which illuminates a color liquid crystal display panel as a transmissive image display unit with light emitted from the emission surface.
The light guide plate according to any one of claims 1 to 5. The light guide plate according to any one of claims 1 to 6,
A light source section that is disposed to face the incident surface of the light guide plate, and that supplies light to the incident surface;
A surface light source device. The light guide plate according to any one of claims 1 to 6,
A light source section that is disposed to face the incident surface of the light guide plate, and that supplies light to the incident surface;
A transmissive image display unit that is disposed on the light exit surface side of the light guide plate and is illuminated by light emitted from the light guide plate and displays an image;
A transmissive image display device. An optical sheet made of a translucent resin and used for a light guide plate,
An incident surface on which light is incident;
A reflecting surface for providing a reflecting portion that is a surface that intersects the incident surface and reflects the light;
An exit surface that is opposite to the reflecting surface and emits the light;
With
The amount of the ultraviolet absorber added to the translucent resin is 50 mass ppm or less,
Optical sheet.

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