JP2013044799A - Transmission type image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission type image display device which can realize a larger effective display screen.SOLUTION: A transmission type image display device 1 includes: a light guide plate 30 for emitting light incident from an incident surface 33 from an emission surface 31 crossing the incident surface; a plurality of point light sources 22 arranged lateral to the incident surface for outputting light to be supplied to the incident surface; a transmission type image display part 10 arranged on a front face side relative to the light guide plate and irradiated by light emitted from the emission surface; and a casing part 40 for storing the light guide plate, the plurality of point light sources, and the transmission type image display part. On the incident surface, there are formed a plurality of convex parts extending in a thickness direction of the light guide plate. The plurality of convex parts is arranged in parallel in a direction orthogonal to a thickness direction. The casing part includes a front surface frame part 70 for defining an opening to allow the surface of the transmission image display part to be exposed. The front surface frame part includes a concealment part 71a for concealing an end part at the incident surface side of the light guide plate.

Description

  The present invention relates to a transmissive image display apparatus.

  The transmissive image display device generally includes a surface light source device that emits planar light, a transmissive image display unit that displays an image by being illuminated by the planar light emitted from the surface light source device, and a surface. And a housing unit that houses the light source device and the transmissive image display unit (see, for example, Patent Document 1). An example of the transmissive image display unit is a liquid crystal panel. In this case, the transmissive image display device is a so-called liquid crystal display device. An opening is formed on the front side of the housing so as to expose the transmissive image display.

  As the surface light source device, as described in Patent Document 1, an edge light type surface light source device in which a light source is disposed at an end portion of a light guide plate has begun to be adopted. As the light source provided in the surface light source device, the use of a point light source such as a light emitting diode (LED) is increasing.

JP 2008-145876 A

  When a point light source is used, usually, a plurality of point light sources are disposed along a direction orthogonal to the thickness direction of the light guide plate while facing the incident surface of the light guide plate. Light from each point light source spreads radially as the distance from the point light source increases. When light from an adjacent point light source enters the light guide plate from the incident surface, the light from the adjacent point light source intersects after having propagated from the incident surface to some extent. Therefore, the amount of light is reduced in the region between the adjacent point light sources at the end on the incident surface side of the light guide plate. As a result, in the transmissive image display device, the vicinity of the end portion on the incident surface side of the light guide plate becomes dark.

  Therefore, in the transmissive image display device, the light guide plate is incident on the housing portion that accommodates the surface light source device and the transmissive image display portion by a frame portion that defines an opening for exposing the transmissive image display portion. The vicinity of the end on the surface side is concealed. However, in this case, the opening is small. As a result, the effective display screen, which is an area where the image can be visually recognized by the user, tends to be reduced by being exposed through the opening in the display screen of the transmissive image display section.

  SUMMARY An advantage of some aspects of the invention is that it provides a transmissive image display device capable of realizing a larger effective display screen.

  The transmissive image display device according to the present invention outputs a light that is incident on an incident surface and is output from an exit surface that intersects the incident surface, and light that is disposed on the side of the incident surface and is supplied to the incident surface. A plurality of point light sources, a transmissive image display unit disposed on the front side with respect to the light guide plate and illuminated by light emitted from the exit surface, the light guide plate, the plurality of point light sources, and the transmissive image A housing portion that houses the display portion. A plurality of convex portions extending in the thickness direction of the light guide plate are formed on the incident surface. The plurality of convex portions are arranged in parallel in a direction orthogonal to the thickness direction. The casing includes a front frame that defines an opening for exposing the surface of the transmissive image display. The front frame portion has a concealing portion that conceals the end portion on the incident surface side of the light guide plate.

  In this configuration, light from a plurality of point light sources arranged to face the incident surface of the light guide plate enters from the incident surface of the light guide plate and exits from the output surface. The light emitted from the exit surface of the light guide plate illuminates the transmissive image display unit, so that an image is displayed on the transmissive image display unit. Since the said housing | casing part is equipped with the front frame part and the front frame part has defined the opening part, an image can be visually recognized through an opening part. In the above configuration, since a plurality of convex portions extending in the thickness direction of the light guide plate are formed on the incident surface of the light guide plate in a direction orthogonal to the extending direction of the convex portion, the light incident from the incident surface Is spread over a wider range in the direction orthogonal to the extending direction of the convex portion. Thereby, the area | region where the brightness of the edge part (side surface vicinity) by the side of the entrance plane of a light-guide plate is insufficient in front view can be reduced. As a result, the width of the concealing portion can be narrowed at the end portion on the incident surface side of the light guide plate included in the front frame portion, so that the opening becomes larger. Therefore, the effective display screen as the surface of the transmissive image display unit exposed from the opening can be made larger.

  In one embodiment, in the cross section of the convex part orthogonal to the extending direction of the convex part, the apex angle of the top part of the convex part may be 50 ° or more and 150 ° or less.

  In one embodiment, the plurality of point light sources are arranged along the arrangement direction of the plurality of convex portions, the arrangement pitch of the plurality of point light sources is u (mm), and the width of the concealing portion is v ( mm), and l / u ≦ 0.30 and v / u ≦ 1 when the distance from the top of the convex portion to the position where the light output from two adjacent point light sources intersects is l (mm) .10.

  In one embodiment, the point light source may be an LED light source. In this form, in the luminous intensity distribution of the LED light source, the normal direction of the light emitting surface of the LED light source becomes the maximum luminous intensity, and the half width of the luminous intensity distribution can be 40 ° or more and 80 ° or less.

  In one embodiment, the housing portion may include a first housing portion that houses a plurality of point light sources and a light guide plate, and a second housing portion that houses a transmissive image display portion. In this form, the front frame part can be provided at the end of the second housing part opposite to the first housing part.

  In this case, the second housing portion is located on the front side with respect to the first housing portion. Since the front frame part can be provided at the end opposite to the first housing part in the second housing part, the image displayed on the transmissive image display part through the opening defined by the front frame part. In addition to being visible, the concealing portion of the front frame portion can conceal the end portion on the incident surface side of the light guide plate from the front side.

  According to the present invention, it is possible to provide a transmissive image display device capable of realizing a larger effective display screen.

1 is an exploded perspective view schematically showing a configuration of a transmissive image display apparatus according to an embodiment of the present invention. It is a top view of the transmissive image display apparatus shown in FIG. FIG. 3 is an end view taken along line III-III in FIG. 2. It is a graph which shows an example of the light emission distribution of a LED light source. It is a perspective view which shows typically the structure of an example of a light-guide plate. It is a perspective view which shows typically the structure of the other example of a light-guide plate. It is drawing which shows typically the incident state of the light when light injects from the LED light source to the light-guide plate in which the convex-shaped part is not formed. 6 is a diagram schematically showing an incident state of light when light is incident on the light guide plate shown in FIG. 5 from an LED light source. It is a graph which shows the evaluation result of an Example and a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or corresponding elements are denoted by the same reference numerals, and redundant description is omitted. The dimensional ratios in the drawings do not necessarily match those described.

  FIG. 1 is an exploded perspective view schematically showing a configuration of a transmissive image display apparatus according to an embodiment of the present invention. FIG. 2 is a plan view of the transmissive image display apparatus shown in FIG. FIG. 3 is an end view taken along line III-III in FIG.

  The transmissive image display device 1 includes a transmissive image display unit 10 and a backlight unit 20 that is disposed on the back side of the transmissive image display unit 10 in FIG. 1 and emits planar light. In the following description, as shown in FIG. 1, the arrangement direction of the backlight unit 20 and the transmissive image display unit 10 is referred to as the z direction, and the two directions orthogonal to the z direction and orthogonal to each other are the x direction. And the y direction. The side on which the transmissive image display unit 10 is disposed with respect to the backlight unit 20 is also referred to as a front side. The transmissive image display device 1 may include at least one optical sheet S between the backlight unit 20 and the transmissive image display unit 10. Examples of the optical sheet S include a light diffusion sheet and a brightness enhancement sheet. When a plurality of optical sheets S are used, different types of optical sheets (for example, a light diffusion sheet and a brightness enhancement sheet) can be used in combination.

  The transmissive image display unit 10 is illuminated by the planar light emitted from the backlight unit 20 and displays the image I (see FIG. 2) on the display screen D. Examples of the transmissive image display unit 10 include a liquid crystal display panel in which linearly polarizing plates 12 and 12 are disposed on both surfaces of a liquid crystal cell 11. In this case, the transmissive image display device 1 is a liquid crystal display device (or a liquid crystal television). As the liquid crystal cell 11 and the polarizing plates 12 and 12, those used in the transmissive image display device 1 such as a conventional liquid crystal display device can be used. Examples of the liquid crystal cell 11 include known liquid crystal cells such as TFT type and STN type.

  The backlight unit 20 includes a light guide plate 30 and a plurality of LED light sources (point light sources) 22 arranged to face the side surface 33 of the light guide plate 30.

  The LED light source 22 functions as a point light source of the backlight unit 20. As shown in FIG. 2, the plurality of LED light sources 22 are arranged to face the side surfaces 33, 33 extending in the y direction of the light guide plate 30 (direction perpendicular to the thickness direction of the light guide plate 30). The plurality of LED light sources 22 are discretely arranged along the longitudinal direction of the side surface 33 (y direction in the embodiment illustrated in FIGS. 1 and 3). The arrangement interval u of the LED light sources 22 is usually 5 mm to 150 mm. The arrangement interval of the LED light sources 22 is a distance between corresponding portions (for example, corresponding side surfaces) of the LED light sources 22 in the arrangement direction of the adjacent LED light sources 22 (y direction in FIGS. 1 and 3). 1 and 3, the distance between the corresponding side surfaces of each of the two adjacent LED light sources 22 in the y direction is shown as an arrangement interval. Hereinafter, the arrangement interval u of the LED light sources 22 is also referred to as an arrangement pitch u. An example of the distance between the LED light source 22 and the side surface 33 is 0 mm to 2 mm. Here, the distance between the LED light source 22 and the side surface 33 may be a distance between the LED light source 22 and a plane connecting the tops of a plurality of convex portions 36 a described later formed on the side surface 33.

  The LED light source 22 may be a white LED, and 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 the LED light source 22, those having various light emission distributions can be used, but the light intensity distribution in the normal direction of the LED light source 22 is maximum, and the half value width of the light intensity distribution is not less than 40 degrees and not more than 80 degrees. Those having are preferred. Specific examples of the LED light source 22 include a Lambertian type, a shell type, and a side emission type. The normal direction of the LED light source 22 may be the normal direction of the light emitting surface of the LED light source 22. In the form shown in FIGS. 1 to 3, the normal direction of the LED light source 22 corresponds to the x direction.

  FIG. 4 is a graph showing an example of the light output distribution of the LED light source. The relationship between the emission angle φ and the emission light intensity is shown with the emission light intensity in the normal direction (emission angle φ = 0 °) of the LED light source 22 being 1.0 (reference). In the LED light source 22 having the light emission distribution shown in FIG. 4, the full width at half maximum is about 60 °. The light output distribution of the LED light source 22 is not limited to that shown in FIG. 4 as described above. In other words, as the LED light source 22, an LED light source having other light output distribution may be used.

  The configuration of the light guide plate 30 will be described with reference to FIGS. As shown in FIG. 1, the light guide plate 30 has a rectangular shape, and the size of the plan view shape is selected so as to match the size of the display screen D of the target transmissive image display device 1, but is usually 250 mm. × 440 mm or more, preferably 1020 mm × 1800 mm or less. The planar view shape of the light guide plate 30 is not limited to a rectangle but may be a square, but in the following, it will be described as a rectangle unless otherwise specified. In FIG. 2, the size of the planar view shape of the light guide plate 30 is the same as the size of the planar view shape of the transmissive image display unit 10.

  The light guide plate 30 is formed of a translucent resin that transmits light and has a plate shape. The light guide plate 30 may be a sheet or a film.

  The light guide plate 30 includes a pair of main surfaces (31, 32) facing in the z direction (thickness direction), a pair of side surfaces 33, 33 facing in the x direction, and a pair of side surfaces 34, 34 facing in the y direction. ing. The side surfaces 33, 33, 34, and 34 intersect with a pair of main surfaces (31, 32). In the present embodiment, as illustrated in FIGS. 1 to 3, the side surfaces 33, 33, 34, 34 are orthogonal to the pair of main surfaces (31, 32). Since the pair of side surfaces 33 and 33 face the LED light source 22, they are incident surfaces on which light from the LED light source 22 enters the light guide plate 30.

  One main surface (31) of the pair of main surfaces facing each other in the z direction functions as an emission surface 31 that emits planar light. The emission surface 31 is disposed on the transmissive image display unit 10 side, and the other main surface (back surface 32) is disposed on the opposite side to the transmissive image display unit 10. A plurality of reflective dots 35 (see FIG. 2) can be formed on the back surface 32 as a reflective portion for emitting light propagating through the light guide plate 30 from the light exit surface 31. An example of the reflective dot 35 is white ink. The plurality of reflection dots 35 can be arranged so that the luminance of light emitted from the emission surface 31 is substantially uniform within the emission surface 31. The plurality of reflective dots 35 can be formed by, for example, screen printing or ink jet printing. In the present embodiment, a plurality of reflective dots 35 are illustrated as the reflective portion. However, the reflective portion is limited to the reflective dots 35 as long as it has a function of emitting light propagating through the light guide plate 30 from the emission surface 31. Not.

  FIG. 5 is a perspective view schematically showing the configuration of the light guide plate. A plurality of convex portions 36 that are convex outward in the x direction are formed on the side surface 33 of the light guide plate 30. Since the plurality of convex portions 36 are formed on the side surface 33, the side surface 33 has an uneven shape. The convex portions 36 extend in the thickness direction (z direction) of the light guide plate 30, and a plurality of the convex portions 36 are arranged in parallel in the longitudinal direction (x direction) of the side surface 33. The cross-sectional shape orthogonal to the extending direction (z direction) of the plurality of convex portions 36 is substantially uniform. An example of the arrangement pitch P of the plurality of convex portions 36 is 0.03 mm or more and 10.0 mm or less. The arrangement pitch P of the plurality of convex portions 36 may be the distance between the apexes 36a, 36a of the two adjacent convex portions 36, 36. A specific example of the arrangement pitch P of the convex portions 36 within the above exemplified range is 0.4 mm.

  As shown in FIG. 5, the convex portion 36 preferably has a prism shape. When the convex portion 36 has a prism shape, in the cross section orthogonal to the z direction, an example of the angle (vertical angle) θ of the top portion 36a of the convex portion 36 is 50 ° or more and 150 ° or less, and 60 ° or more and 100. It can be below. In the present embodiment, the apex angle θ of the prism shape is, for example, 120 °. The plurality of prism shapes have a function of diffusing light from the LED light source 22 in the longitudinal direction (y direction) of the side surface 33.

  In FIG. 5, the ends of the two adjacent convex portions 36 are in the same position in the y direction. However, as shown in FIG. 6, a flat portion 38 having a certain width may be formed between two adjacent convex portions 36.

  The light guide plate 30 is made of a translucent resin. The refractive index of the translucent resin is usually 1.49 to 1.59. As the translucent resin used for the light guide plate 30, methacrylic resin is mainly used.

  Examples of the methacrylic resin include monomers having methyl methacrylate as a main component. Specifically, the methacrylic resin may be a polymer obtained by polymerizing a monomer containing 50% by mass or more of methyl methacrylate. Further, it may be methyl polymetalate obtained by polymerizing methyl methacrylate alone, or a copolymer of 50% by mass or more of methyl methacrylate and 50% by mass or less of a monomer copolymerizable therewith. May be.

  Examples of monomers copolymerizable with methyl methacrylate include ethyl methacrylate, propyl methacrylate, butyl methacrylate, benzyl methacrylate, 2-ethylhexyl acrylate, cyclohexyl methacrylate, bornyl methacrylate, adamantyl methacrylate, methacrylic acid. Methacrylic acid esters such as cyclopentanedienyl, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, bornyl acrylate, adamantyl acrylate, acrylic Acrylic esters such as cyclopentadienyl acid, unsaturated calculates such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride, etc. Acid and its anhydride, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl acrylate, acrylic acid, monoglycerol acrylate, 2-hydroxyethyl methacrylate, 2-hydroxy methacrylate Hydroxyl group-containing monomers such as propyl and monoglycerol methacrylate, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, diacetone acrylamide, nitrogen-containing monomers such as dimethylaminoethyl methacrylate, allyl glycidyl ether, glycidyl acrylate, Examples thereof include epoxy group-containing monomers such as glycidyl methacrylate, and styrene monomers such as styrene and α-methylstyrene.

  The translucent resin is not limited to the above, and other resins may be used, for example, styrene resin, polyethylene resin, polypropylene resin, cyclic olefin polymer resin, acrylonitrile-butadiene-styrene resin, polyethylene terephthalate resin, Examples include polycarbonate resin.

  In applying the light guide plate 30 to the transmissive image display device 1 such as a liquid crystal display device, additives such as a light diffusing agent, an ultraviolet absorber, a heat stabilizer, and a photopolymerization stabilizer are added to the light guide plate 30. Also good.

  An example of a method for manufacturing the light guide plate 30 will be described. When manufacturing the light guide plate 30, first, an optical sheet is produced by extrusion molding, cast molding, injection molding, or the like. This optical sheet is a sheet-like flat plate. The thickness of the optical sheet corresponds to the distance between the exit surface 31 and the back surface 32 of the light guide plate 30. The thickness of the optical sheet is not particularly limited, but is preferably set in the range of 1.0 mm to 10.0 mm, particularly preferably 1.5 mm to 8.0 mm, and further 2. It is preferable that it is 0 mm-4.0 mm. Next, the light guide plate 30 is obtained by forming a plurality of reflective dots 35 and convex portions 36 as reflective portions on the optical sheet. The reflective dots 35 can be formed by screen printing or ink jet printing as described above.

  The convex portion 36 can be formed by applying, for example, a hot press molding method. By performing hot press molding using an opposite mold having a shape paired with the convex portion 36 as a plate, the convex portion 36 is formed on the side surface of the optical sheet to be the side surface 33 of the light guide plate 30. This corresponds to forming an uneven shape on the side surface 33.

  An injection molding method may be applied as a method for processing the convex portion 36. When the injection molding method is employed, it is preferable that the inner wall of the injection mold is provided with an opposite mold having a shape that is paired with the convex portion 36. In addition, it is also preferable that the non-shaped surface side of the lens film, on which the convex portion 36 has already been applied, be bonded to the side surface side of the optical sheet that should become the side surface 33 of the light guide plate 30 via an adhesive layer. is there.

  Examples of the convex portion 36 include a lenticular lens shape, a trapezoidal shape, and a rectangular shape in addition to the prism shape described above. In particular, in the case of a prism shape, the prism apex angle θ may be set between 50 ° and 150 °, and may be set between 60 ° and 100 °.

  Returning to FIGS. 1 to 3, the configuration of the transmissive image display apparatus 1 will be further described. As shown in FIGS. 1 to 3, the transmissive image display device 1 includes a housing unit 40 that houses the transmissive image display unit 10 and the backlight unit 20. The housing unit 40 includes a back side housing unit 50 that houses the plurality of LED light sources 22 and the light guide plate 30, a front side housing unit 60 that houses the transmissive image display unit 10, and a front frame unit 70. The planar view shape of the housing unit 40 is a shape corresponding to the planar view shape of the transmissive image display unit 10 (or the planar view shape of the light guide plate 30). The example of the planar view shape of the housing | casing part 40 contains a rectangle and a square.

  The back side accommodating portion 50 is configured such that four side walls 52, 52, 53, 53 are erected on a bottom wall 51. The side walls 52 and 52 are opposed to each other in the x direction. The side walls 53 are opposed to each other in the y direction. The example of the material of the back side accommodating part 50 is a polycarbonate. The inner surface of the bottom wall 51 of the back side housing part 50 may be mirror-finished. Thereby, since the light leaked from the back surface 32 side of the light guide plate 30 is returned into the light guide plate 30, the light from the LED light source 22 can be used efficiently. From the viewpoint of effectively using the light from the LED light source 22, a reflective sheet may be provided between the bottom wall 51 and the light guide plate 30 instead of mirroring the inner surface of the bottom wall 51. The side walls 52, 52, 53, 53 may be formed with support portions for supporting the light guide plate 30 and the plurality of LED light sources 22. In the case where an optical sheet is provided, the side walls 52, 52, 53, 53 can also be formed with support portions for supporting them.

  The front side of the back side housing part 50, that is, the side opposite to the bottom wall 51 is open so that light emitted from the emission surface 31 of the light guide plate 30 enters the transmissive image display unit 10. In other words, the opening 54 for allowing the light emitted from the light guide plate 30 to pass through is formed on the front side of the back side housing portion 50. In the form shown in FIGS. 1 to 3, the opening 54 is defined by the end of the side walls 52, 52, 53, 53 on the bottom wall 51 side, but provided with an opposing wall that faces the bottom wall 51. An opening may be formed in the opposing wall.

  A front side accommodating portion 60 is connected to the front side of the rear side accommodating portion 50. The front side accommodating part 60 can be connected to the back side accommodating part 50 by, for example, screwing. The front-side accommodation unit 60 is configured with four side walls 62, 62, 63, 63 standing on a bottom wall 61. The bottom wall 61 can function as a support unit that supports the transmissive image marking unit 10. The side walls 62 and 62 are opposed to each other in the x direction. The side walls 63 and 63 are opposed to each other in the y direction. The example of the material of the front side accommodating part 60 is a polycarbonate, and the front side accommodating part 60 may be comprised from the material same as the material of the back side accommodating part 50. FIG. The bottom wall 61 functions as a support unit that supports the transmissive image display unit 10. The bottom wall 61 is formed with an opening 64 through which light emitted from the emission surface 31 of the light guide plate 30 passes.

A plate-like front frame portion 70 is provided at the front side end of the front side housing portion 60, that is, at the end opposite to the bottom wall 61 of the side walls 62, 62, 63, 63. The front frame part 70 can be fixed to the front side accommodating part 60 by, for example, screwing. The front frame portion 70 is a frame portion in the transmissive image display device 1. The front frame part 70 has four side parts 71, 71, 72, 72. The side parts 71 and 71 are opposed in the x direction. The side parts 72 and 72 are opposed to each other in the y direction. The display screen D of the transmissive image display unit 10 exposed from the region surrounded by the four sides 71, 71, 72, 72 is a screen region that can be viewed by the user. This screen area is referred to as an effective display screen _DE .

  Of the four side portions 71, 71, 72, 72, the two side portions 71, 71 corresponding to the side surface 33 of the light guide plate 30 have a concealing portion 71a. The concealing portion 71a conceals the end portion 37 where the convex portion 36 is formed in the light guide plate 30 when viewed from the front direction. In other words, as shown in FIGS. 2 and 3, the concealing portion 71a is a region that overlaps the end portion 37 of the light guide plate 30 in the side portion 71 when viewed from the front direction (hereinafter also referred to as an overlapping region). . The hatching in FIG. 2 is for showing the concealing part 71a. The width v of the concealing portion 71a is the length in the direction from the side surface 33 toward the opposite side surface 33 (the length in the x direction in FIGS. 1 to 3). As illustrated in FIG. 1 to FIG. 3, when the bottom wall 61 of the front-side accommodation unit 60 has a region protruding inward from the side wall 62, the concealing unit 71 a also conceals that region. Usually, the width of the region protruding inward from the side wall 62 in the bottom wall 61 of the front side accommodation portion 60 is narrower than the width of the concealing portion 71a.

  1 to 3 exemplify a form in which the bottom wall 61 of the front side accommodating portion 60 has a region protruding inward from the side wall 63, the width of the region where the side wall 63 is provided in the bottom wall 61. (For example, the width in the y direction in FIGS. 1 and 2) may be the same as the width of the side wall 63. In this case, the distance between the side portions 72 and 72 may be the same as the length of the light guide plate 30 in the y direction.

    Next, functions and effects of the transmissive image display device 1 will be described.

  In the transmissive image display device 1, when the plurality of LED light sources 22 output light, the light from the plurality of LED light sources 22 enters from the side surface 33. The light incident from the side surface 33 propagates while being totally reflected in the light guide plate 30. When the light propagating in the light guide plate 30 is reflected by the reflection dots 35, it is reflected under conditions other than the total reflection condition, and thus the light reflected by the reflection dots 35 is emitted from the emission surface 31. Since part of the light propagating in the light guide plate 30 is emitted from the emission surface 31, planar light is emitted from the emission surface 31.

  The planar light emitted from the emission surface 31 passes through the openings 54 and 64 and illuminates the transmissive image display unit 10. As a result, an image can be displayed on the transmissive image display unit 10.

  In the transmissive image display device 1 of the present embodiment, the convex portions 36 are formed at the end portion 37 on the side surface 33 side of the light guide plate 30, thereby reducing the widths of the side portions 71 and 71 of the front frame portion 70. it can. This point will be described in comparison with a case where the convex portion 36 is not formed. FIG. 7 is a drawing schematically showing an incident state of light when light is incident from an LED light source on a light guide plate on which no convex portion is formed. The configuration of the light guide plate 80 shown in FIG. 7 is the same as the configuration of the light guide plate 30 except that a convex portion is not formed on the side surface facing the LED light source 22. Therefore, in the light guide plate 80, elements other than the side surface 81 facing the LED light source 22 are denoted by the same reference numerals as those of the light guide plate 30. FIG. 8 is a drawing schematically showing an incident state of light when light is incident on the light guide plate shown in FIG. 5 from an LED light source.

  As shown in FIG. 7, the light from each LED light source 22 enters the light guide plate 80 from the substantially flat side surface 81 and propagates in the light guide plate 80 while spreading further radially. Light from two adjacent LED light sources 22, 22 intersect after light has propagated a certain distance from the side surface 81 of the light guide plate 80. If this intersection is designated as an intersection p for convenience, the amount of light in the area between the intersection p and the side surface 81 decreases. Therefore, when an image is displayed on the transmissive image display unit 10, the region corresponding to the end portion on the side surface 81 side of the light guide plate 80 tends to be dark. Therefore, in the transmissive image display device 1 such as a liquid crystal television, the frame portion is used to conceal the end portion on the side surface 81 side of the light guide plate 80.

  In the light guide plate 30 of the present embodiment, since the convex portion 36 is formed on the side surface 33, the light incident from the side surface 33 of the light guide plate 30 is refracted by the convex portion 36, as shown in FIG. , In the y direction. As a result, it is possible to reduce a region where the brightness is insufficient at the end portion 37 on the side surface (incident surface) 33 side of the light guide plate 30. That is, the distance l between the intersection point p of the two lights and the apex 36a of the convex portion 36 can be shortened. In this case, the concealment part 71a becomes small in the front frame part 70 which is a frame part. For example, in the transmissive image display device 1 employing the light guide plate 30, the arrangement pitch u of the LED light sources 22, the width v of the concealing portion 71 a, and the distance l are 1 / u ≦ 0.30 and v / u ≦ 1. 10 can be satisfied.

When the distance l is shortened, the concealing portion 71a is reduced in the front frame portion 70 which is a frame portion, and as a result, the width of the side portion 71 can be shortened. By reducing the width of the side portion 71, the area of the effective display screen _DE that can be viewed by the user on the display screen D is increased.

(Example)
Hereinafter, with reference to an Example, the point which can narrow the width | variety of a concealing part by employ | adopting the light-guide plate in which the convex-shaped part was formed in the side surface is demonstrated.

  An evaluation unit including the light guide plate according to Examples 1 to 5 and an evaluation unit including the light guide plate according to Comparative Examples 1 and 2 were produced, and an evaluation test was performed on these. Hereinafter, Examples 1 to 5 will be described using the same reference numerals as those used in the description of the embodiments illustrated in FIGS. 1 to 3, 4, and 5.

(Evaluation unit of Example 1)
The light guide plate 30 according to Example 1 was produced as follows. An optical sheet A having a rectangular shape in plan view was produced using Sumipec E011 (trade name, manufactured by Sumitomo Chemical Co., Ltd., PMMA) as the translucent resin. The thickness of the optical sheet A was 4 mm, and in the planar view shape of the optical sheet A, the length of the vertical (short side) was 210 mm, and the length of the horizontal (long side) was 300 mm.

  By arranging a plurality of convex portions 36 extending in the thickness direction (z direction) on the side surface on the short side of the optical sheet A in parallel in the longitudinal direction (y direction in FIG. 1) of the side surface (incident surface). An uneven shape was formed on the side surface of the short side of the sheet A. The convex portion 36 was formed by laser processing. The arrangement pitch (distance between the top portions 36a) P of the plurality of convex portions 36 was 0.4 mm. In Example 1, as shown in FIG. 5, the flat part 38 was provided between the adjacent convex parts 36. As shown in FIG. The width of the flat portion 38, that is, the distance between the end of one convex portion 36 and the end of the other convex portion 36 in two adjacent convex portions 36 was 0.2 mm. The cross-sectional shape orthogonal to the extending direction of the convex portion 36 is a prism shape, and the apex angle θ is 60 °.

  The light guide plate 30 of Example 1 was obtained by bringing a white tape (TRUSCO's TRT-50 double-sided tape) into close contact with the entire surface of one main surface of the optical sheet A on which the convex portion 36 was formed. Specifically, only the protective tape on the side facing the optical sheet A of the white tape was peeled off to expose the adhesive surface, and the white tape was adhered to the main surface of the optical sheet A. The main surface of the optical sheet A to which the white tape is attached corresponds to the back surface 32 of the light guide plate 30. The white tape functions as a reflective portion that reflects the light propagating through the light guide plate 30 so as to be emitted from the emission surface 31 (surface opposite to the back surface 32), instead of the reflective dots 35 in FIG.

  A plurality of LED light sources (120 ° Lambertian type; NSSW 123B) are arranged at a predetermined arrangement pitch u so as to face the side surface 33 on which the convex portion 36 of the light guide plate 30 of Example 1 is formed. Was used as an evaluation unit. The LED light source 22 was disposed in contact with the light guide plate 30. In Example 1, the arrangement pitch u of the plurality of LED light sources was 8 mm.

(Evaluation unit of Example 2)
The light guide plate 30 according to Example 2 was produced as follows. After producing the same optical sheet A as in Example 1, the light guide plate of Example 2 is the same as in Example 1 except that the uneven shape formed by the plurality of convex portions 36 is different. 30 was produced. The uneven shape which is a difference from the first embodiment will be described. In Example 2, the arrangement pitch (distance between the tops 36a) P of the plurality of convex portions 36 was set to 0.4 mm as in the case of Example 1. In Example 2, as shown in FIG. 4, no flat portion was provided between adjacent convex portions 36. The cross-sectional shape orthogonal to the extending direction of the convex portion 36 is a prism shape, and the apex angle θ is 90 °.

  Next, an evaluation unit of Example 2 was produced in the same manner as in Example 1 except that the light guide plate 30 of Example 2 was used instead of the light guide plate 30 of Example 1.

(Evaluation unit of Example 3)
The light guide plate 30 according to Example 3 was produced as follows. After producing the same optical sheet A as in Example 1, the light guide plate of Example 3 is the same as in Example 1 except that the uneven shape formed by the plurality of convex portions 36 is different. 30 was produced. The uneven shape which is a difference from the first embodiment will be described. In Example 3, the arrangement pitch (distance between the tops 36a) P of the plurality of convex portions 36 was set to 0.4 mm as in the case of Example 1. In Example 3, as in Example 1, a flat portion 38 was provided between adjacent convex portions 36. The width of the flat part 38 was 0.4 mm. The cross-sectional shape orthogonal to the extending direction of the convex portion 36 is a prism shape, and the apex angle θ is 130 °.

  Next, an evaluation unit of Example 2 was produced in the same manner as in Example 1 except that the light guide plate 30 of Example 3 was used instead of the light guide plate 30 of Example 1.

(Evaluation unit of Example 4)
The light guide plate 30 according to Example 4 was produced as follows. After producing the same optical sheet A as in Example 1, the light guide plate of Example 4 is the same as in Example 1 except that the uneven shape formed by the plurality of convex portions 36 is different. 30 was produced. The uneven shape which is a difference from the first embodiment will be described. In Example 4, the arrangement pitch (distance between the tops) of the plurality of convex portions 36 was set to 0.4 mm as in Example 1. In Example 4, as in Example 1, a flat portion was provided between adjacent convex portions 36. The width of the flat part was 0.2 mm. The cross-sectional shape orthogonal to the extending direction of the convex portion 36 is a prism shape, and the apex angle θ is 60 °.

  Next, in the case of Example 1, except that the light guide plate 30 of Example 4 is used instead of the light guide plate 30 of Example 1 and the arrangement pitch u of the plurality of LED light sources is 8.8 mm. In the same manner, an evaluation unit of Example 4 was produced.

(Evaluation unit of Example 5)
The light guide plate 30 according to Example 5 was the same as the light guide plate of Example 2. The evaluation unit of Example 5 was the same as the evaluation unit of Example 2 except that the arrangement pitch u of the LED light sources was 8.8 mm in the evaluation unit of Example 2.

(Evaluation unit of Example 6)
The light guide plate 30 according to Example 6 was the same as the light guide plate of Example 3. The evaluation unit of Example 6 was the same as the evaluation unit of Example 3 except that the arrangement pitch u of the LED light sources was 8.8 mm in the evaluation unit of Example 3.

(Evaluation unit of Comparative Example 1)
In Comparative Example 1, a backlight unit mounted on “EX710 32V” (liquid crystal television) manufactured by Sony Corporation was used as an evaluation unit. That is, the light guide plate and LED light source mounted on “EX710 32V” were used. Also in Comparative Example 1, the LED light source was disposed so as to be in contact with the light guide plate. In Comparative Example 1, the arrangement pitch u of the plurality of LED light sources was 8.8 mm. As shown in FIG. 7, the light guide plate had a flat side surface as an incident surface. Therefore, for convenience of explanation, the light guide plate mounted on “EX710 32V” will be referred to as a light guide plate 80 and will be described with the same reference numerals as those of the light guide plate 80 of FIG.

(Evaluation unit of Comparative Example 2)
In Comparative Example 2, the LED light source of the evaluation unit in Comparative Example 1 is changed to the LED light source 22 used in Example 1, and the arrangement pitch u of the plurality of LED light sources 22 is set to 8.0 mm. Two evaluation units were prepared.

(Evaluation method)
In each evaluation unit of Examples 1 to 5, with the LED light source 22 turned on, the distance l from the top of the convex portion 36 to the point p where light of adjacent LED light sources intersects with the naked eye was measured. Further, in each evaluation unit of Comparative Examples 1 and 2, the distance l from the side surface 81 to the point p where the lights of the adjacent LED light sources intersect with each other was measured with the LED light sources turned on. The width v of the concealing part in Examples 1 to 5 and Comparative Examples 1 and 2 was defined as follows. For Comparative Example 1, the width of the concealing portion of “EX710 32V” (the overlapping region with the end portion on the side surface 81 side of the light guide plate 80) was actually measured to obtain the width v of the concealing portion. The width v of the concealing portion in Comparative Example 1 was 10 mm. The width v of the concealing part for the evaluation units of Examples 1 to 5 and Comparative Example 2 is only the difference between the distance l measured in Comparative Example 1 and the distance l measured in Examples 1 to 5 and Comparative Example 2. The value of 10 mm, which is the width v of the concealing portion of Comparative Example 1, was changed.

(Evaluation results)
The evaluation results are shown in FIG. FIG. 9 is a chart showing evaluation results of Examples and Comparative Examples. In FIG. 9, the shape of the side surfaces 33 and 81 of the light guide plate 30 of Examples 1 to 5 and the light guide plates 80 and 80 of Comparative Examples 1 and 2, and the evaluation units of Examples 1 to 5 and Comparative Examples 1 and 2 The arrangement pitch u of the plurality of LED light sources in FIG. From FIG. 9, comparing Examples 1 to 3 and Comparative Example 2 in which the arrangement pitch of the LED light sources is 8 mm, the distance l to the intersection point p is shorter in Examples 1 to 3 than in Comparative Example 2. As a result, the width v of the concealing portion can be set narrower. Similarly, when Examples 4 to 6 and Comparative Example 1 in which the arrangement pitch u of the LED light sources is 8.8 mm are compared, the distance l to the intersection point p is shorter in Examples 4 to 6 than in Comparative Example 1. Yes. As a result, the width v of the concealing portion can be set narrower. In Examples 1 to 6, as shown in FIG. 9, p / u ≦ 0.30 and v / u ≦ 1.10.

Thus, by forming the convex portion 36 on the side surface 33 facing the LED light source 22, the width of the concealing portion 71 a can be set narrow in the light guide plate 30 whose side surface 33 has an uneven shape. As a result, the effective display screen _DE becomes wider.

  As mentioned above, although this invention was concretely demonstrated based on the embodiment and an Example, this invention is not limited to the said embodiment. For example, the housing unit 40 includes a back side housing unit 50 as a first housing unit and a front side housing unit 60 as a second housing unit, but the housing unit 40 includes the front frame unit 70. It is only necessary to include a housing for housing the transmissive image display unit 10, the plurality of LED light sources 22, and the light guide plate 30. For example, the accommodating part that accommodates the transmissive image display unit 10, the plurality of LED light sources 22, and the light guide plate 30 may be a box-like body whose front side is open.

  In the form illustrated in FIGS. 1 to 3, the LED light source 22 is disposed with respect to the side surface 33 and the side surface 33. However, the point light source such as the LED light source 22 may be disposed only on one of the side surfaces 33 facing each other. The point light source may be arranged with respect to the side surfaces 34 and 34. In this case, the side surfaces 34 and 34 are incident surfaces. Even when a point light source is arranged with respect to the side surface 34, the point light source only needs to be arranged on one of the opposing side surfaces 34, 34.

  In the description using the form illustrated in FIGS. 1 to 3, the side surface serving as the incident surface is the side surface 33, and therefore the longitudinal direction of the side surface serving as the incident surface is the y direction. However, as described above, when the side surface 34 functions as the incident surface, the longitudinal direction of the side surface serving as the incident surface is the x direction. Moreover, it is preferable that the convex portions are arranged at equal intervals with an arrangement pitch P of 0.03 mm to 10.0 mm in the longitudinal direction of the incident surface. Good.

  DESCRIPTION OF SYMBOLS 1 ... Transmission type image display apparatus, 10 ... Transmission type image display part, 20 ... Back light unit, 22 ... LED light source (point light source), 30 ... Light guide plate, 31 ... Output surface, 33 ... Side surface (incident surface), 36 ... convex part, 37 ... end part, 40 ... housing part, 50 ... back side accommodation part (first accommodation part), 54 ... opening part, 60 ... front side accommodation part (second accommodation part), 70: Front frame part, 71: Side part, 71a ... Concealment part.

Claims (5)

A light guide plate that emits light incident from an incident surface from an exit surface that intersects the incident surface;
A plurality of point light sources arranged on the side of the incident surface and outputting light supplied to the incident surface;
A transmissive image display unit disposed on the front side with respect to the light guide plate and illuminated with light emitted from the emission surface;
A housing that houses the light guide plate, the plurality of point light sources, and the transmissive image display;
With
A plurality of convex portions extending in the thickness direction of the light guide plate are formed on the incident surface,
The plurality of convex portions are arranged in parallel in a direction orthogonal to the thickness direction,
The housing part has a front frame part that defines an opening for exposing the surface of the transmissive image display part,
The front frame portion has a concealing portion that conceals an end portion on the incident surface side of the light guide plate.
Transmission type image display device. In the cross section of the convex part perpendicular to the extending direction of the convex part, the apex angle of the top part of the convex part is 50 ° or more and 150 ° or less,
The transmissive image display apparatus according to claim 1. The plurality of point light sources are arranged along the arrangement direction of the plurality of convex portions,
The arrangement pitch of the plurality of point light sources is u (mm), the width of the concealing portion is v (mm), and the convex portions up to the position where the light output from the two adjacent point light sources intersects each other. When the distance from the top is 1 (mm), 1 / u ≦ 0.30 and v / u ≦ 1.10.
The transmissive image display device according to claim 1. The point light source is an LED light source,
In the luminous intensity distribution of the LED light source, the normal direction of the light emitting surface of the LED light source is the maximum luminous intensity, and the half value width of the luminous intensity distribution is 40 ° or more and 80 ° or less.
The transmissive image display apparatus as described in any one of Claims 1-3. The housing portion is
A first accommodating portion that accommodates the plurality of point light sources and the light guide plate;
A second accommodating portion for accommodating the transmissive image display portion;
With
The front frame portion is provided at an end of the second housing portion opposite to the first housing portion.
The transmissive image display apparatus as described in any one of Claims 1-4.

Images