JP5423145B2 - Surface light source device, backlight unit, and display device - Google Patents

Description

  The present invention relates to a surface light source device, a backlight unit, and a display device used for illumination light path control, and more particularly to a surface light source device used for illumination light path control in an image display device typified by a flat panel display. The present invention relates to a backlight unit and a display device.

  In recent large-sized liquid crystal televisions, a direct-type backlight unit in which a plurality of cold cathode tubes and LEDs (Light Emitting Diodes) are arranged is employed. This direct type backlight unit includes a surface light source device that emits light from a light source scattered by a light diffusion plate and an optical sheet that collects the light emitted from the surface light source device. This light diffusing plate is formed by forming a transparent resin in which light diffusing particles are dispersed and mixed into a plate shape, and has a very strong light scattering property. Thereby, the light emitted from the light source is diffused so that a light source image such as a cold cathode tube or an LED as a light source is not visually recognized.

This light diffusing plate suppresses the light source from being visually recognized as described above, but also has a demerit that the image display of the liquid crystal display device is darkened because the light is diffused in all directions by the light diffusing effect. . Further, in this light diffusion plate, in order to maintain a high light scattering property, the plate thickness is usually set to about 1 to 5 mm, and the light transmitted through the light diffusion plate is absorbed by this thickness. The LCD screen display becomes dark.
Furthermore, liquid crystal televisions tend to be thinner year by year, and a thinner light diffusing plate is required, and further improvement of light diffusibility is required.

  On the other hand, the light diffusing plate used in the direct type backlight diffuses light emitted from the cold cathode tube, which is a light source, and reduces luminance unevenness (lamp image) due to the light source being visually recognized. Although it is arranged for the purpose, it is difficult to completely erase the lamp image even with the light diffusion plate. That is, when the addition amount of diffusing particles imparting light diffusibility is increased only for the purpose of extinguishing the lamp image, the total light transmittance is excessively lowered, causing a decrease in luminance. On the other hand, if the addition amount of the diffusing particles is reduced so as not to lower the total light transmittance, a sufficient diffusion effect cannot be obtained.

  In order to cope with this problem, Patent Documents 1 to 3 disclose a lens in which a lens shape is added to an exit surface of a light diffusion plate. In such a light diffusing plate, it is necessary to design the lens shape in accordance with the arrangement of the light sources and determine the alignment of the lens, so that the manufacturing process may be complicated and complicated. Further, by adding this lens shape separately, the reflected light from the lens increases, so that the total light transmittance of the light diffusing plate is lowered and the liquid crystal display screen may be darkened. Furthermore, there may be a case where moire interference fringes are generated from the lens sheet and the liquid crystal pixels arranged on the light diffusion plate.

  As an improvement measure for reducing the total light transmittance as described above, as an optical sheet disposed on the exit surface side of the surface light source device, a brightness enhancement film (Brightness Enhancement Film, which is a registered trademark of 3M USA) A method using (referred to as BEF) is known.

  The BEF is configured by periodically arranging unit prisms having a triangular cross section in one direction on a light-transmitting substrate, and the unit prisms have a size (pitch) larger than the wavelength of light. It is formed to become. In BEF, light from “off-axis” is collected and directed to the viewer “on-axis” or “recycle”. "can do. In other words, the BEF has a function of increasing the on-axis brightness as the off-axis brightness is lowered when the display is used. Note that “on-axis” is a direction that coincides with the viewing direction of the viewer, and generally indicates a normal direction to the display screen.

  However, when this BEF is used, a phenomenon occurs in which a light component due to reflection / refractive action is emitted in the lateral direction without proceeding in the visual direction of the viewer. In other words, when BEF is used, the light intensity in the axial direction is maximized, while a small light intensity peak (side lobe) occurs in the vicinity of the viewing angle ± 90 °, and light that is wasted from the lateral direction is wasted. It will increase.

  In order to solve such a problem of BEF, it is effective to dispose a diffusion film having both diffusion and condensing functions between the BEF and the liquid crystal control panel. As a result, the occurrence of the side lobes can be suppressed, and furthermore, moire interference fringes generated between regularly arranged lenses and liquid crystal pixels can be prevented. On the other hand, if the diffusing film is disposed between the light diffusing plate and the BEF, the diffused light emitted from the light diffusing plate can be efficiently collected and the light source that cannot be extinguished only by the light diffusing plate can be visually recognized. It is also possible to suppress the sex.

  However, when the diffusion film is used, the number of parts increases, and the work at the time of assembling the display device becomes complicated, and there arises a problem that the manufacturing cost increases. In order to solve such a problem, for example, Patent Document 4 does not use an optical film in which only unit prisms are formed as an optical film in place of BEF, but arranges light deflection lenses at a constant pitch in a two-dimensional direction. A backlight unit using an optical film having an array structure is disclosed. By using this optical film, generation of side lobes can be suppressed.

JP 2007-103321 A JP 2007-12517 A JP 2006-195276 A JP 2007-213035 A

By the way, in recent years, display devices are required to be thinner than the current state, and in order to meet this requirement, it is necessary to further reduce the thickness of the light diffusion plate in the surface light source device of the backlight unit.
However, if the light diffusing plate is thinned, its light scattering characteristic is deteriorated. Therefore, in order to prevent the visual recognition of the lamp image and the luminance unevenness, it is necessary to have a certain thickness or more. On the other hand, it may be possible to improve the light scattering property per unit thickness by increasing the amount of light diffusing particles contained in the light diffusing plate. However, in this case, the total light transmittance is significantly reduced, and the screen display is extremely low. It will be too dark.

  The present invention has been made in view of such a problem, and is capable of eliminating the uneven brightness of the screen while improving the brightness of the screen display. An object is to provide a backlight unit and a display device.

In order to solve the above problems, the present invention proposes the following means.
That is, the surface light source device according to the present invention is formed into a corrugated plate shape in which a trough that projects to the back side and a crest that projects to the front side are alternately formed, and the plate surface facing the back side is incident. A wave diffusing portion made of a transparent resin having a plate surface facing the front side and an emission surface, a light diffusing plate disposed on the front side of the wave diffusing portion, and the wave diffusing portion A reflector disposed on the back side;
Wherein a light source disposed between the waveform diffusion portion and the reflecting plate, along with the waveform the valleys of the exit surface of the diffusion section the peaks and the Rukoto light deflection elements are formed It is a feature.

In the surface light source device having such a feature, the light emitted from the light source directly enters the waveform diffusing unit or enters the waveform diffusing unit via a reflector disposed on the back side of the light source. Here, since the corrugated diffuser has a corrugated plate shape in which valleys and peaks are alternately continuous, the light incident on the corrugated diffuser is incident and exited according to the shape of the peaks and troughs. Refracts in various directions on the surface. Thereby, light scattering can be given to the light which passes a waveform diffusion part. And the light inject | emitted from this waveform diffusion part is further diffused by the light diffusing plate, and is inject | emitted to the front side.
As described above, since the light emitted from the light source can be effectively diffused by the waveform diffusing unit, the light emitted from the surface light source device should be highly light scattering even if the light diffusion plate is formed thin. Can do. Moreover, since the waveform diffusion part is made of a transparent resin, light passing through the waveform diffusion part is hardly absorbed into the waveform diffusion part, and light with high luminance can be emitted.
Further, the light incident at an angle close to the incident surface of the waveform diffusing unit, that is, the light incident at a small incident angle with respect to the incident surface is transmitted to the light source side by the light deflection element formed on the exit surface. Total reflection is possible. Then, the totally reflected light is reflected by the reflecting plate and is incident on the incident surface of the waveform diffusing section with an inclination from the vertical direction, that is, incident with an increased incident angle. Refracted greatly at the surface and the exit surface. Thereby, the light passing through the waveform diffusing unit can be further diffused, and the emitted light without unevenness in brightness can be emitted.

In the surface light source device according to the present invention, each of the troughs of the waveform diffusing unit is in contact with the reflecting plate, and the light source is disposed in a space between the peak of the waveform diffusing unit and the reflecting plate. It is characterized by being.
With such a configuration, the surface light source device itself can be made compact, and the surface light source device can be made thin.

  In the surface light source device according to the present invention, the light deflection element is formed by arranging a plurality of long unit lenses in parallel, and the unit lenses are arranged in a direction in which the valley and the peak are continuous. It is characterized by extending.

  According to the surface light source device having such a feature, each unit lens receives light incident at an angle close to perpendicular to the incident surface of the waveform diffusing unit, that is, light incident at a small incident angle with respect to the incident surface. In addition, the reflected light is reflected by the reflector and re-enters the incident surface of the waveform diffusion unit from an inclined angle. It is possible to refract light in a direction in which the part is continuous and improve the diffusibility of light in the direction. As a result, it is possible to effectively reduce luminance unevenness due to a difference in viewing angle in a direction in which the valley portion and the peak portion of the waveform diffusion portion are continuous.

  Moreover, in the surface light source device according to the present invention, the light deflection element includes a plurality of long unit lenses arranged in parallel, and the unit lens has the valley portion and the peak portion continuous. It extends in the direction orthogonal to the direction.

  According to the surface light source device having such a feature, each unit lens receives light incident at an angle close to perpendicular to the incident surface of the waveform diffusing unit, that is, light incident at a small incident angle with respect to the incident surface. In addition, the reflected light is reflected by the reflector and re-enters the incident surface of the waveform diffusion unit from an inclined angle. Light can be refracted in a direction orthogonal to the direction in which the part is continuous, and the light diffusibility in that direction can be further improved. As a result, it is possible to effectively reduce luminance unevenness due to a difference in viewing angle in a direction orthogonal to a direction in which valleys and peaks of the waveform diffusing unit are continuous.

In the surface light source device according to the present invention, the unit lens preferably has a prism shape or a lenticular lens shape.
This ensures that each unit lens reflects light incident at an angle close to the incident surface of the waveform diffusing unit, that is, light incident at a small incident angle to the incident surface toward the light source side. Therefore, it is possible to reliably improve the diffusibility of light passing through the waveform diffusing unit.

  In the surface light source device according to the present invention, the light deflection element may be formed by arranging a plurality of unit lenses in a lattice shape.

  According to the surface light source device having such a feature, each unit lens receives light incident at an angle close to perpendicular to the incident surface of the waveform diffusing unit, that is, light incident at a small incident angle with respect to the incident surface. Then, the light is reflected by the reflecting plate and re-entered from the angle inclined to the incident surface of the waveform diffusing unit, so that the light is refracted in the arrangement direction of the unit lenses, It becomes possible to improve the diffusibility of light. Thereby, it is possible to effectively reduce luminance unevenness due to a difference in viewing angle in the arrangement direction of the unit lenses.

In the surface light source device according to the present invention, it is preferable that the unit lenses arranged in a lattice form have a substantially hemispherical or substantially elliptical hemispherical microlens shape or a polygonal pyramid shape.
Also by this, each unit lens reliably totally reflects light incident at an angle close to the incident surface of the waveform diffusing unit, that is, light incident at a small incident angle with respect to the incident surface toward the light source side. Therefore, it is possible to reliably improve the diffusibility of light passing through the waveform diffusing unit.

  The backlight unit according to the present invention is characterized in that at least one optical sheet is laminated on the front side of the surface light source device.

  According to the backlight unit having such characteristics, light having high luminance and diffusibility that has passed through the waveform diffusing unit and the light diffusing plate is condensed and emitted to the front side by the optical sheet. Thereby, the brightness | luminance of the light inject | emitted from a backlight unit can further be improved.

  The display device according to the present invention is characterized in that an image display element that displays an image by transmitting or blocking light in units of pixels is laminated on the front side of the backlight unit.

  According to the display device having such a feature, the provision of the backlight unit makes it possible to improve luminance, reduce luminance unevenness, and reduce the thickness of the device itself.

  According to the surface light source device, the backlight unit, and the display device of the present invention, the light emitted from the light source passes through the waveform diffusing unit and enters the light diffusing plate, thereby improving the brightness of the screen display. The luminance unevenness of the screen can be eliminated while achieving the plan, and the thickness can be reduced.

It is a longitudinal cross-sectional view of the display apparatus which concerns on embodiment. It is a perspective view of the waveform spreading | diffusion part in FIG. 1, a light source, and a reflecting plate. It is a perspective view of the waveform spreading | diffusion part in FIG. It is an A direction arrow directional view in FIG. It is a B direction arrow line view in FIG. It is a perspective view at the time of making the waveform spreading | diffusion part in FIG. 1 into flat form. It is a schematic diagram explaining the optical effect | action by a waveform spreading | diffusion part. It is a schematic diagram explaining the optical effect | action in the flat light-guide plate in which the light deflection element was formed in the output surface. It is a perspective view of a lens sheet in which a triangular prism is formed on the exit surface. It is a perspective view of a lens sheet in which triangular prisms orthogonal to each other are formed on the exit surface and the entrance surface. FIG. 6 is a perspective view of a lens sheet in which a quadrangular pyramid unit lens is formed on an exit surface. It is a perspective view of a lens sheet in which a unit lens having a microlens shape is formed on the exit surface. It is a longitudinal cross-sectional view of the backlight unit provided with the waveform spreading | diffusion part which makes the front-end | tip of a peak part and a trough part sharp, and the inclined part which connects these peak part and trough part forms a linear form. It is a longitudinal cross-sectional view of the backlight unit provided with the waveform spreading | diffusion part which the front-end | tip of a peak part and a trough part makes flat shape, and the inclination part which connects these peak part and trough part makes linear form. FIG. 15 is a longitudinal sectional view when the light source is CCF1 in the backlight unit shown in FIG. 14. It is a longitudinal cross-sectional view of a backlight unit in the case where the waveform diffusing portion has a substantially cycloid shape. FIG. 17 is a longitudinal sectional view when the light source is CCF1 in the backlight unit shown in FIG. 16. It is a perspective view of the waveform diffusion part in which the light deflection element is not formed in the trough, the light source, and the reflector. FIG. 5 is a perspective view of a wave diffusing unit, a light source, and a reflecting plate in which a light deflecting element having a prism shape extends in a direction orthogonal to the extending direction of a peak and a valley. FIG. 5 is a perspective view of a wave diffusing unit, a light source, and a reflecting plate in which light deflecting elements having a prism shape extend in a direction in which peaks and valleys extend.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a longitudinal sectional view of the display device of this embodiment. In FIG. 1, the reduced scale of each component does not match the actual one. Further, the upper side in FIG. 1 is referred to as the front side or the front direction, and the lower side is referred to as the back side.

  As shown in FIG. 1, the display device 22 is a liquid crystal display device configured by overlapping an image display element 15 on the front side of a backlight unit 21 that emits light in the front direction. An image is displayed by emitting display light whose display is controlled by an image signal from the element 15 toward the viewer.

  The image display element 15 includes two polarizing plates (polarizing filters) 16 and 16 and a liquid crystal panel 17 sandwiched between them. The liquid crystal panel 17 is configured, for example, by filling a liquid crystal layer between two glass substrates, and the light emitted from the backlight unit 21 is liquid crystal via the polarizing filter 16 on the front side. The light enters the panel 17 and exits in the front direction through the polarizing filter 16 on the back side.

The image display element 15 is preferably an element that transmits / shields light in pixel units and displays an image, thereby displaying an image with high image quality.
The image display element 15 is preferably a liquid crystal display element. This liquid crystal display element is a representative element that transmits / shields light in pixel units and displays an image. Compared with other display elements, this liquid crystal display element can improve image quality and reduce manufacturing cost. be able to.

  The backlight unit 21 includes an optical sheet 14 for controlling an illumination light path disposed so as to face the polarizing filter 16 on the light incident side of the image display element 15, that is, the back side, and a surface light source that irradiates the optical sheet 14. The apparatus 20 is comprised.

  The optical sheet 14 is configured, for example, by integrally forming a lens array on a surface facing the back side of a translucent substrate that is formed in a film shape and has light transmissivity, that is, an emission surface. This lens array is configured by arranging, for example, a plurality of lenses such as a plurality of prisms and lenticular lenses. In the backlight unit 21 of the present embodiment, a plurality of such optical sheets 14 may be laminated or a single one.

  The lens array may be molded on a translucent substrate using UV or radiation curable resin. For example, PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), Using a COP (cycloolefin polymer), an acrylonitrile styrene copolymer, etc., it may be integrally formed with the translucent substrate by a known extrusion molding method, injection molding method or hot press molding method.

  The surface light source device 20 includes a light source 11, a reflecting plate 10, a waveform diffusing unit 12, and a light diffusing plate 13.

As shown in FIGS. 1 and 2, a point light source capable of emitting light radially is employed as the light source 11. In this embodiment, the light source 11 as the point light source is light in the surface light source device 20. Are arranged in a matrix in a two-dimensional direction along the exit surface. A reflector 10 configured in a rectangular box shape with an upper opening is provided so as to cover the back side and the side of the light source 11 arranged in a matrix. That is, the light source 11 is arrayed and fixed to the bottom of the box shape formed by the reflecting plate 10, whereby the surface light source device 20 constitutes a so-called direct type light emitting device that emits light toward the front side. .
In addition, the reflecting plate 10 should just be a member which can reflect light with high efficiency, for example, a general reflecting film, a reflecting plate, etc. can be used.

The light source 11 as the point light source is composed of, for example, an LED (light emitting diode). Examples of the LED include color LEDs such as red (R), green (G), and blue (B), and white LEDs. As the white LEDs, the R, G, and B color chips are unitized. Multi-chip type, single-chip type that obtains white color with blue, purple, ultraviolet, near-ultraviolet LED and one or more phosphors.
In addition, as a point light source, for example, a normal fluorescent lamp, a halogen lamp, a semiconductor laser, or the like may be used.

  The light source 11 may be a linear light source. Examples of the linear light source include a lamp light source such as a fluorescent lamp, a cold cathode fluorescent lamp (CCFL), or an EEFL. These linear light sources are parallel to each other along a box-shaped bottom portion formed by the reflector 10. The array is fixed so that

  As shown in FIGS. 1 to 5, the waveform diffusing unit 12 has a corrugated plate shape in which a crest 121 projecting to the front side and a trough 122 projecting to the back are alternately continuous. These peak portions 121 and valley portions 122 each extend in one direction (the depth direction in FIG. 1 in the drawing). Therefore, the waveform diffusing portion 12 in this embodiment is an extension of the peak portions 121 and the valley portions 122. It has a wave shape that meanders to the front side and the back side in a direction orthogonal to the current direction.

  Moreover, the height difference of the adjacent peak part 121 and the trough part 122 is made the same, and, thereby, the plane in contact with each peak part 121 and the plane in contact with each trough part 122 are parallel. Furthermore, the part which connects the peak part 121 and the trough part 122 is made into the inclined part 123, and in this embodiment, the peak part 121 and the trough part 122 are rounded, respectively. And the valley part 122 is smoothly connected by the inclined part 123, thereby forming a shape in which a sine curve is drawn in a cross section orthogonal to the peak part 121 and the valley part 122.

  The plate surface facing the back side of the waveform diffusing unit 12 is an incident surface 12a on which light emitted from the light source 11 is incident, and the plate surface facing the front side is an emission surface on which light incident from the incident surface 12a is emitted. A light deflection element 124 (not shown in FIGS. 1 and 4) is formed on the latter exit surface 12b.

In the present embodiment, the light deflection element 124 includes a plurality of long unit lenses 125 extending in the direction in which the crests 121 and the troughs 122 are alternately continued, that is, in the direction along the sine curve. It is comprised by arranging. Thereby, the plurality of unit lenses 125 are arranged in the extending direction of the peak portion 121 and the valley portion 122. Further, in this embodiment, a lenticular lens having a lens surface having an arc shape in a cross-sectional view orthogonal to the extending direction of the unit lens 125 is used as the unit lens 125.
That is, as shown in FIG. 6, the waveform diffusing unit 12 has a shape obtained by forming a flat lens sheet 100 in which a plurality of lenticular lenses 100a extending in one direction are arranged in parallel into a corrugated shape. -ing
The period of the sine curve of the waveform diffusing unit 12 is determined according to the arrangement distance of the light source 11.

  As shown in FIGS. 1 and 2, such a waveform diffusing unit 12 is arranged such that each valley 122 is in contact with the reflector 10, that is, the box-shaped bottom of the reflector 10. At this time, each light source 11 is located between the waveform diffusing unit 12 and the reflecting plate 10, whereby each light source 11 is located on the back side of the peak 121 of the waveform diffusing unit 12, and the light source 11 is covered with the waveform diffusing section 12.

  Further, as shown in FIG. 1, the side of the waveform diffusing portion 12 is covered with a box-shaped side plate portion of the reflecting plate 10. At this time, the upper end of the side plate portion and each peak portion 121 of the waveform diffusing portion 12 are located on the same plane, that is, the upper end of the side plate portion of the reflector plate 10 with respect to the bottom portion of the reflector plate 10. The height and the height of each peak 121 of the waveform diffusing unit 12 are configured to be the same.

When manufacturing such a waveform diffusing section 12, first, the light deflection element 124 is formed on one surface of a sheet-like base material formed from a light-transmitting transparent resin.
Examples of the transparent resin forming the base material include acrylic resin, polystyrene (PS) resin, methacryl styrene copolymer (MS) resin, polycarbonate (PC) resin, acrylonitrile styrene copolymer (AS) resin, and cycloolefin. A polymer (COP) or the like, a copolymer containing these as components, or a mixture of these resins is used.
The light deflection element 124 is made of a thermoplastic resin well known in the art using PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), COP (cycloolefin polymer), or the like. It may be integrally formed with the above-mentioned base material by the press molding or extrusion molding used, the casting method or the injection method, or an ultraviolet curing molding method in which an ultraviolet-curing resin is disposed on one surface of the base material, that is, It may be formed by a UV curing method. When producing by this UV curing method, a UV curable resin is applied on one surface of the substrate, a mold having a desired shape is pressed, and then UV irradiation is performed to form the light deflection element.
Next, the sheet-like material in which the light deflection element 124 is formed on the substrate in this way is bent into a corrugated shape. At this time, a mold for drawing a sine curve may be used, or a support member for supporting a wave shape may be used. Then, the corrugated diffuser 12 having a corrugated shape can be obtained by heating the sheet-like material bent into a corrugated shape in an oven at 100 ° C. and then cooling it.

  Further, the thickness of the waveform diffusing unit 12 is preferably 0.2 × d or more and 1.0 × d or less, where the distance between the light sources 11 is a parameter d. When the thickness is less than 0.2 × d, the light diffusive effect is thin and the rigidity is also small. On the other hand, when the thickness exceeds 1.0 × d, the reduction in thickness is hindered, and the necessity of providing light diffusibility using the waveform diffusing portion 12 becomes thin, and the flexibility to withstand the processing is obtained. Because there is no.

  The light diffusing plate 13 is configured by forming a transparent resin plate shape in which light diffusing regions are dispersed into a plate shape, and a plate surface facing the back side of each wave diffusing portion 12 has a peak 121 and a reflection. It is in contact with the upper end of the side wall of the plate 10. As a result, the waveform diffusing unit 12 is sealed with the light diffusing plate 13 and the reflecting plate 10.

  As the transparent resin, which is the material of the light diffusion plate 13, a thermoplastic resin, a thermosetting resin, or the like can be used. For example, a polycarbonate resin, an acrylic resin, a fluorine acrylic resin, a silicone acrylic resin, an epoxy acrylate Resins, polystyrene resins, cycloolefin polymers, methylstyrene resins, fluorene resins, polyethylene terephthalate (PET), polypropylene, acrylonitrile styrene copolymers, acrylonitrile polystyrene copolymers, and the like can be used.

The light diffusion region is preferably made of light diffusion particles. This is because suitable diffusion performance can be easily obtained. As the light diffusing particles, transparent particles made of an inorganic oxide or a resin can be used. As the transparent particles made of an inorganic oxide, for example, silica, alumina or the like can be used. The transparent particles made of resin include acrylic particles, styrene particles, styrene acrylic particles and cross-linked products thereof, melamine / formalin condensate particles, PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy resin), FEP (tetrafluoroethylene). Fluoropolymer particles such as fluoroethylene / hexafluoropropylene copolymer), PVDF (polyfluorovinylidene), and ETFE (ethylene / tetrafluoroethylene copolymer), silicone resin particles, and the like can be used.
Moreover, you may use combining 2 or more types of transparent particles from the transparent particle mentioned above. Furthermore, the size and shape of the transparent particles are not particularly defined.

When light diffusing particles are used as the light diffusing region, the thickness of the light diffusing plate 13 is preferably 0.1 to 5 mm.
When the thickness of the light diffusion plate 13 is 0.1 to 5 mm, optimum diffusion performance and brightness can be obtained. On the other hand, if the thickness is less than 0.1 mm, the diffusion performance is insufficient, and if it exceeds 5 mm, the amount of resin is large and the luminance is reduced due to absorption.

  In the case where a thermoplastic resin is used as the transparent resin, air bubbles may be used as the light diffusion region. The internal surface of the bubble formed inside the thermoplastic resin causes diffused reflection of light, and a light diffusing function equivalent to or higher than that when light diffusing particles are dispersed can be expressed. Therefore, it becomes possible to make the film thickness of the light diffusing plate 13 thinner.

  Specific examples of such a light diffusion plate 13 include white PET and white PP. White PET is obtained by dispersing fillers such as resin incompatible with PET, titanium oxide (TiO2), barium sulfate (BaSO4), and calcium carbonate in PET, and then stretching the PET by a biaxial stretching method. Thus, bubbles are generated around the filler.

  In addition, the light diffusing plate 13 made of a thermoplastic resin only needs to be stretched in at least one axial direction. This is because bubbles can be generated around the filler by stretching in at least one axial direction.

  Examples of the thermoplastic resin include polyethylene terephthalate (PET), polyethylene-2, 6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, cyclohexanedimethanol copolymer polyester resin, isophthalic acid copolymer polyester resin, sporoglycol copolymer polyester. Resins, polyester resins such as fluorene copolymer polyester resins, polyolefin resins such as polyethylene, polypropylene, polymethylpentene, and alicyclic olefin copolymer resins, acrylic resins such as polymethyl methacrylate, polycarbonate, polystyrene, polyamide, polyether , Polyester amide, polyether ester, polyvinyl chloride, cycloolefin polymer, and copolymers containing these as components Also it can be used like a mixture of these resins are not particularly limited.

When bubbles are used as the light diffusion region, the thickness of the light diffusion plate 13 is preferably 25 to 500 μm.
When the thickness of the light diffusing plate 13 is less than 25 μm, it is not preferable because the sheet is insufficiently squeezed and wrinkles are easily generated in the manufacturing process and display. In addition, when the thickness of the light diffusion plate 13 exceeds 500 μm, there is no particular problem in optical performance, but since the rigidity is increased, it is difficult to process into a roll shape and the slit cannot be easily formed. Since the advantage of the thinness obtained by comparison becomes small, it is not preferable.

  By each member as described above, the surface light source device 20 in the present embodiment is formed into a corrugated plate shape in which a trough portion 122 projecting to the back side and a crest portion 121 projecting to the front side are alternately continuous, A wave diffusing portion 12 made of a transparent resin having a plate surface facing the back surface as the entrance surface 12a and a plate surface facing the front side as the exit surface 12b, and light disposed on the front side of the wave diffusing portion 12 The configuration includes a diffusing plate 13, a reflecting plate 10 disposed on the back side of the waveform diffusing unit 12, and a light source 11 disposed between the waveform diffusing unit 12 and the reflecting plate 10.

  And the backlight unit 21 of this embodiment is comprised by laminating at least one optical sheet 14 on the front side of such a surface light source device 20, and on the front side of the backlight unit 21, The display device 22 of the present embodiment is configured by stacking the image display elements 15.

Next, the optical action of the display device 22 will be described.
The light emitted from the light source 11 is directly incident on the incident surface 12 a of the waveform diffusing unit 12, or incident on the waveform diffusing unit 12 through reflection on the reflection plate 10 disposed on the back side of the light source 11. The light enters the surface 12a, passes through the inside of the waveform diffusing unit 12, and is emitted from the exit surface 12b. At this time, the light is refracted at the interface between the incident surface 12a and the air and the interface between the exit surface 12b and the air of the waveform diffusing unit 12.

The light emitted from the exit surface 12 b of the waveform diffusing unit 12 is incident on the light diffusion plate 13 disposed on the front side of the waveform diffusing unit 12. In addition, about the location where the waveform diffusion part 12 and the light diffusion plate 13 are contacting, light injects directly into the light diffusion plate 13 from the waveform diffusion part 12, and the said light is light from these waveform diffusion parts 12 and light. The light is refracted at the interface with the diffusion plate 13.
The light incident on the light diffusing plate 13 is appropriately given a scattering effect in the light diffusion region dispersed and mixed in the light diffusing plate 13 and is emitted to the front side.

  The light emitted from the light diffusing plate 13 enters the optical sheet 14, is condensed on the front side, and then is emitted toward the image display element 15. Thereafter, the light emitted from the optical sheet 14 passes through the polarizing filter 16, the liquid crystal panel 17, and the polarizing filter 16 of the image display element 15, and the light is transmitted as display light from a predetermined pixel region. An image having a viewing angle is displayed.

  Here, in the present embodiment, since the waveform diffusing unit 12 has a corrugated plate shape in which the crests 121 and the troughs 122 are alternately continuous, the light incident on the waveform diffusing unit 12 The light is refracted in various directions on the entrance surface 12a and the exit surface 12b according to the shape of the 122 trough. That is, light refracting can be imparted to the light passing through the waveform diffusing unit 12 by refracting the light by the incident surface 12a and the exit surface 12b having these wave shapes. Then, the light imparted with a certain amount of light scattering in the waveform diffusing unit 12 is further diffused by the light diffusing plate 13 and emitted to the front side.

  Thus, since the light emitted from the light source 11 can be diffused by the waveform diffusing unit 12, the light emitted from the surface light source device 20 can have high light scattering properties. That is, in the present embodiment, diffusibility is imparted to the light emitted from the light source 11 by two steps of the waveform diffusing unit 12 and the light diffusing plate 13. This has the following advantages compared to simply imparting diffusibility only by the light diffusion plate 13.

That is, when it is attempted to impart diffusibility to the light from the light source 11 using only the light diffusing plate 13 without using the waveform diffusing unit 12, the light diffusing plate can be used to maintain a high diffusing effect. It is necessary to set the thickness of 13 to at least about 1 mm. When the thickness is set in this way, light absorption is large in the process of passing through the light diffusion plate 13, and light with high luminance cannot be emitted toward the front side.
In this regard, since the waveform diffusing portion 12 is molded from a transparent resin, light passing through the waveform diffusing portion 12 is hardly absorbed. Therefore, the light passing through the waveform diffusing unit 12 is emitted with a certain degree of diffusibility while maintaining high brightness. Therefore, by imparting diffusibility to light by the waveform diffusing unit 12, even if the light diffusing plate 13 is thinly formed, the diffusibility of light emitted from the surface light source device 20 may be sufficiently high. It can be done.

  Therefore, in the surface light source device 20 of this embodiment, the screen is improved while improving the brightness of the screen display by imparting diffusibility to the light from the light source 11 by two steps of the waveform diffusing unit 12 and the light diffusing plate 13. Brightness unevenness can be eliminated, and the surface light source device 20 itself can be made thinner.

  Moreover, in this embodiment, each trough part 122 and the reflecting plate 10 of the waveform diffusion part 12 contact | abut, and the light source 11 is arrange | positioned in the space between the peak part 121 and the reflecting plate 10 of the waveform diffusion part 12. Therefore, the surface light source device 20 can have a compact configuration.

  Furthermore, as described above, in the present embodiment, the light deflection element 124 is formed on the exit surface 12 b of the waveform diffusing unit 12. As a result, as shown in the schematic diagram corresponding to the waveform of the waveform diffusing unit 12 in FIG. 7, the light L1a and L1b incident on the incident surface 12a of the waveform diffusing unit 12 at an angle close to perpendicular, that is, the incident angle is reduced. Incident light L1a and L1b can be totally reflected to the light source 11 side. Such lights L1a and L1b are totally reflected by entering the interface between the light deflection element 124 and air at an angle exceeding the critical angle.

  Then, the totally reflected light is reflected by the reflecting plate 10 and is re-incident on the incident surface 12a of the waveform diffusing section 12 while being re-incident from the vertical direction, that is, incident again with a larger incident angle. Then, the light is refracted by the incident surface 12a and the exit surface 12b of the waveform diffusing unit 12 and emitted. That is, by forming the light deflection element 124, it is possible to further diffuse the light passing through the waveform diffusing unit 12 and to emit the emitted light with no uneven brightness.

Such an effect can be exhibited only when the waveform diffusing unit 12 has a wave shape and the light deflection element 124 is formed on the exit surface 12b. In this regard, for example, as shown in FIG. 8, in the flat light guide plate 101 in which the light deflection element 101a is formed on the emission surface, the light L1 emitted to the front side when viewed from the light source 11 is the light deflection element 101a. The light L2 and L3 emitted in the direction inclined from the front direction are not totally reflected, but are totally reflected by being incident on the interface between the air and the air exceeding the critical angle. It is refracted to the side or goes straight and injected. Therefore, the light diffusibility cannot be improved.
On the other hand, in the present embodiment, light from the light source 11 is incident on the incident surface 12a of the waveform diffusing unit 12 having a wave shape at an angle close to vertical, and this light is totally reflected to be reflected by the reflecting plate 10. By re-entering the waveform diffusing section 12 through reflection again, the light is effectively refracted and the light diffusibility can be improved.

  In addition to the above functions, the waveform diffusing unit 12 has a function of supporting the light diffusing plate 13 and the optical sheet 14. Conventionally, a support member such as a pin is required to support the light diffusing plate 13 and the optical sheet 14, but the crest 121 of the corrugated diffusing portion 12 having a wave shape contacts the light diffusing plate 13. By doing so, the light diffusion plate 13 and the optical sheet 14 laminated thereon can be supported.

  Furthermore, the use of the waveform diffusing unit 12 can prevent the light diffusing plate 13 from being bent. Conventionally, in order to prevent the light diffusion plate 13 from being bent, the thickness of the light diffusion plate 13 must be increased. However, when the plurality of peaks 121 of the waveform diffusion unit 12 come into contact with the light diffusion plate 13, Even if the diffusion plate 13 is formed thin, it is possible to prevent the occurrence of bending. That is, by using the waveform diffusing unit 12, it is possible to simultaneously reduce the thickness of the light diffusing plate 13 and prevent the deflection.

  As described above, the embodiments of the present invention have been described in detail. However, the present invention is not limited to these embodiments, and some design changes can be made without departing from the technical idea of the present invention.

  For example, the waveform diffusing unit 12 in the embodiment has a shape obtained by forming a flat lens sheet 100 in which a plurality of lenticular lenses 100a extending in one direction are arranged in parallel into a corrugated shape. However, it may have the following shape.

  For example, as shown in FIG. 9, the waveform diffusing unit 12 has a shape obtained by forming a flat lens sheet 102 in which a plurality of triangular prisms 102a extending in one direction are arranged in parallel into a corrugated shape. It may be a thing.

  In addition, as shown in FIG. 10, the waveform diffusing unit 12 is arranged in parallel with a plurality of triangular prisms 103a extending in one direction on the exit surface side (upper side in FIG. 10). A flat lens sheet 103 in which a plurality of triangular prisms 103b extending in a direction orthogonal to the extending direction of the triangular prism 103a is arranged in parallel on the lower side of FIG. 10 is formed into a corrugated shape. It may be a thing.

  Further, as shown in FIG. 11, the waveform diffusing unit 12 causes the flat lens sheet 104 in which a plurality of unit lenses 104 a having a quadrangular pyramid shape are arranged in a lattice shape on the exit surface side (upper side in FIG. 11) You may make the shape shape | molded in the type | mold.

  Furthermore, as shown in FIG. 12, the waveform diffusing unit 12 includes a flat lens sheet 105 in which a plurality of unit lenses 105a having a microlens shape are arranged in a lattice shape on the exit surface side (upper side in FIG. 12). It may be formed into a wave shape.

Note that any shape of the light deflection element 124 may be formed not only on the exit surface 12b side but also on the entrance surface 12a side. Furthermore, when the light deflection element 124 has a shape extending in one direction, it may extend in a direction in which the incident surface 12a side and the exit surface 12b side intersect or may extend in parallel. .
Further, the shape, pitch and height of the lenses constituting the light deflection element 124 may be different.
Thereby, the diffusion effect by the light deflection element 124 can be appropriately enhanced.

  On the other hand, in the surface light source device 20 described above, the waveform diffusing unit 12 has a corrugated shape that draws a sine curve. Instead, for example, as shown in FIG. The tip portion may have a sharp shape, and the inclined portion 123 that connects the peak portion 121 and the valley portion 122 may have a linear shape.

Moreover, as shown in FIG. 13, in the waveform shape in which the said inclination part 123 makes | forms linear shape, the front-end | tip of the peak part 121 and the trough part 122 may make a parallel flat shape, respectively. Such a shape can be easily obtained by pressing a portion that can be a peak 121 and a portion that can be a valley 122 with a plate-like member to form a flat shape after heating in an oven and forming a wave shape. Can be molded.
Thus, when the peak part 121 and the trough part 122 make flat shape, the reflecting plate 10, the light diffusing plate 13, and the waveform diffusion part 12 can be firmly fixed and integrated.
In this case, as shown in FIG. 14, the light source 11 is a columnar CCF1 extending in the depth direction of the paper surface, and the light source 11 is connected to the peak portion 121 on the back side of the peak portion 121 of the waveform diffusing portion 12. You may arrange | position in the middle with the reflecting plate 10. FIG.

Further, for example, as shown in FIG. 16, the peak 121 of the waveform diffusing section 12 forms a smooth convex arc shape, and the valley section 122 forms a convex shape that is narrowed by the convex arc shapes of the peak sections 121 contacting each other. The waveform diffusing unit 12 having a substantially cycloid curve shape may be provided.
Also in this case, as shown in FIG. 17, the light source 11 is a columnar CCF1 extending in the depth direction of the paper surface, and the light source 11 is located on the back side of the peak 121 of the waveform diffusing unit 12. 121 and the reflector 10 may be arranged in the middle.

  As shown in FIG. 18, in the waveform diffusing unit 12 having the light deflection element 124 in which a plurality of lenticular lenses are arranged, the light deflection element 124 may not be formed in the valley portion 122. Since the valley 122 of the waveform diffusing unit 12 is located close to the reflecting plate 10, there is little light incident from the back side through the reflection of the reflecting plate 10, and further, it is located away from the light diffusing plate 13. This is because there is little influence on luminance unevenness.

  In addition, the waveform diffusion part 12 which shape | molded the lens sheet 102 in which the triangular prism 102a as shown in FIG. As shown in FIG. 19 or FIG.

In FIG. 19, the extending direction of the crest 121 and the trough 122 and the extending direction of the triangular prism 102a are orthogonal to each other, that is, the light deflection element 124 extends along the waveform.
In this case, light incident on the incident surface 12a of the waveform diffusing unit 12 at an angle close to perpendicular, that is, light incident at a small incident angle with respect to the incident surface 12a is incident on the light source side by the light deflection element 124 formed of a triangular prism. Then, the light is further reflected by the reflector and re-enters the incident surface 12a of the waveform diffusing unit 12 from an inclined angle, so that the waveform diffusing unit 12 is arranged in the arrangement direction of the triangular prisms 102a. Light can be refracted in a direction orthogonal to the direction in which the valley portion 122 and the mountain portion 121 are continuous, and the light diffusibility in that direction can be further improved. Thereby, it is possible to effectively reduce luminance unevenness due to a difference in viewing angle in a direction orthogonal to a direction in which the valley 122 and the peak 121 of the waveform diffusing unit 12 are continuous.

In FIG. 20, the extending direction of the crest 121 and the trough 122 and the extending direction of the triangular prism 102a coincide, that is, the light deflection element 124 extends so as to be orthogonal to the waveform. .
In this case, in the same manner as described above, the light is refracted in the direction in which the valley 122 and the peak 121 of the waveform diffusing unit 12 are arranged, which is the arrangement direction of the triangular prisms 102a. Can be further improved. Therefore, it is possible to effectively reduce luminance unevenness due to a difference in viewing angle in a direction in which the valley 122 and the peak 121 of the waveform diffusing unit 12 are continuous.

Example 1
The waveform diffusion part 12 of Example 1 was produced using the prism sheet produced with the ultraviolet curing resin for PET base material. In the waveform diffusing unit 12, the lens pitch of the prism array is 50 μm and the apex angle is 90 °. Further, the prism sheet is bent in the prism shape direction, that is, in the extending direction of the light deflection element 124 to form a sine curve in which the crests 121 and the troughs 122 are alternately continued, and is placed in an oven at about 100 ° C. I put it.
The waveform diffusion part 12 (see FIG. 19) thus produced has a pitch of about 30 mm between the nearest peak part 121 and the peak part 121, and a distance between the peak part 121 and the valley part 122 is about 15 mm. It was.

  The light diffusing plate 13 was produced by melt extrusion molding of a polycarbonate resin. In order to give light diffusibility, a resin filler is mixed in the polycarbonate resin. The total light transmittance of the light diffusion plate 13 was set to 55% and the thickness was set to 3 mm. The light diffusing plate 13 was disposed on the light exit surface side of the waveform diffusing unit 12 and disposed on the light source 11.

(Example 2)
The waveform diffusion part 12 of Example 2 was produced using the prism sheet produced with the ultraviolet curing resin for PET base material. In the waveform diffusing unit 12, the lens pitch of the prism array is 50 μm and the apex angle is 90 °. Further, the prism sheet is bent in a direction orthogonal to the prism shape direction, that is, a direction orthogonal to the extending direction of the light deflection element 124 to form a sine curve in which the peak portions 121 and the valley portions 122 are alternately continuous, It was placed in an oven at about 100 ° C.
The waveform diffusion part 12 (see FIG. 20) thus produced has a pitch of about 30 mm between the nearest peak part 121 and the peak part 121, and a distance between the peak part 121 and the valley part 122 is about 15 mm. It was.

  The light diffusing plate 13 was produced by melt extrusion molding of a polycarbonate resin. In order to give light diffusibility, a resin filler is mixed in the polycarbonate resin. The total light transmittance of the light diffusion plate 13 was set to 55% and the thickness was set to 1.5 mm. The light diffusing plate 13 was disposed on the light exit surface side of the waveform diffusing unit 12 and disposed on the light source 11.

(Comparative Example 1)
A light diffusing plate having a total light transmittance of 55% and a haze value of 92% was prepared as Comparative Example 1. A light diffusing plate was placed on the light source 11.

(Comparative Example 2)
On a light diffusion plate having a total light transmittance of 55% and a haze value of 92%, a diffusion sheet (total light transmittance of 65%, haze value of 87%), prism sheet, prism sheet, diffusion sheet (total light transmittance of 65%) , Haze value 87%) was sequentially laminated as Comparative Example 2. The two prism sheets were arranged so that the extending directions of the prisms were orthogonal to each other. This laminate was placed on the light source 11.

(Luminance unevenness observation test)
In Examples 1 and 2 and Comparative Examples 1 and 2, using an LED arranged with an interval of 30 mm as the light source 11, the distance between the exit surface of the LED and the valley 122 of the waveform diffusing unit 12 is changed, The degree of occurrence of luminance unevenness was evaluated.
At the time of evaluation, whether or not luminance unevenness was observed when the light exit surface was observed from the front direction and the direction inclined by 60 ° with respect to the front direction was confirmed.

  In the case of Examples 1 and 2, the brightness unevenness could be completely eliminated by increasing the distance between the light source 11 and the light diffusion plate to 20 mm. When the interval was further reduced, luminance unevenness was visually recognized. On the other hand, when observed from the front direction and the direction inclined from the front direction, there was almost no difference in luminance unevenness depending on the direction.

  In the case of Comparative Example 1, the luminance unevenness could be completely eliminated by widening the distance between the light source 11 and the light diffusion plate to 30 mm. However, when the interval was further reduced, the luminance unevenness was visually recognized. On the other hand, in Comparative Example 2, the luminance unevenness could be completely eliminated by widening the interval to 25 mm, but when the interval was reduced more than that, the luminance unevenness was visually recognized.

  From the above, it was confirmed that a high luminance unevenness reduction effect can be obtained by arranging the waveform diffusing unit 12 and the light diffusing plate 13 on the light source 11.

DESCRIPTION OF SYMBOLS 10 Reflecting plate 11 Light source 12 Waveform diffuser 12a Incident surface 12b Ejecting surface 13 Light diffusing plate 15 Image display element 16 Polarizing plate (polarizing filter)
17 Liquid crystal panel 21 Backlight unit 22 Display device 12 Waveform diffusion part 121 Mountain part 122 Valley part 123 Inclination part 124 Light deflection element 125 Unit lens

Claims (9)

A plate that is formed into a corrugated plate shape in which valleys that project to the back side and peaks that project to the front side are alternately formed, and the plate surface facing the back side is the entrance surface and faces the front side A wave diffusing portion made of a transparent resin whose surface is an emission surface;
A light diffusing plate disposed on the front side of the waveform diffusing section;
A reflector disposed on the back side of the waveform diffusing section;
A light source disposed between the waveform diffusing unit and the reflector ;
Wherein said waveform diffusing portion along the exit surface the valleys of the peaks and the surface light source device light deflection element, characterized in Rukoto molded. Each of the troughs of the wave diffusing part and the reflecting plate abut,
The surface light source device according to claim 1, wherein the light source is disposed in a space between the peak portion of the waveform diffusion portion and the reflection plate. The light deflection element comprises a plurality of long unit lenses arranged in parallel,
Each unit lens is, the valley and the surface light source device according to claim 1 or 2 wherein the peaks and is characterized in that extending in a direction continuously. The light deflection element comprises a plurality of long unit lenses arranged in parallel,
Each unit lens is, the valley and the surface light source device according to claim 1 or 2 wherein the peaks and is characterized by extending in a direction perpendicular to the direction in which successive. The surface light source device according to claim 3 , wherein the unit lens has a prism shape or a lenticular lens shape. The light deflection element, the surface light source device according to claim 1 or 2, characterized in that by arranging the unit lens to multiple grid pattern. The surface light source device according to claim 6 , wherein the unit lens has a substantially hemispherical or substantially elliptical hemispherical microlens shape or a polygonal pyramid shape. On the front side of the surface light source device according to any one of claims 1 to 7, a backlight unit, wherein at least one optical sheet are layered. 9. A display device, wherein an image display element that displays an image by transmitting or blocking light in pixel units is laminated on the front side of the backlight unit according to claim 8 .

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