JP2010032781A - Optical device, optical diffusion device, optical sheet, back light unit and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical device that further reduces a lamp image, and further improves the display quality of an image display, and to provide an optical diffusion device, an optical sheet, a back light unit and a display device using the optical device. <P>SOLUTION: The optical device 24, which controls the optical path of light rays emitted from a light source 41 and emits the light rays to a viewer side, is composed of: an optical propagation layer 23; and a plurality of optical deflection lenses 28 arranged at the face of the light source side in the optical propagation layer at a fixed pitch. The optical deflection lenses 28 diffuse the light made incident in almost parallel to the normal line direction of the face of the optical propagation layer 23, further deflect the obliquely incident light made incident with an incidence angle ϕ of ≥20° to the normal line direction toward the normal line direction, and control the light intensity peak by the deflected light of the obliquely incident light to the range of ±10° to the normal line direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical device, a light diffusing device, an optical sheet, a backlight unit, and a display device used for illumination light path control, and particularly used for illumination light path control in an image display device typified by a flat panel display. The present invention relates to an optical device, a light diffusion device, an optical sheet, a backlight unit, and a display device.

In recent large-sized liquid crystal televisions, a direct-type backlight having a plurality of cold cathode tubes and LEDs (Light Emitting Diodes) is employed.
In this direct type backlight, a resin plate having a high light scattering property is used as a light diffusion plate between the image display element and the light source, so that a cold cathode tube or an LED as a light source is not visually recognized. Has been.

This light diffusing plate suppresses the light source from being visually recognized as described above, but also diffuses light in all directions by the light diffusing effect, so that the image display of the liquid crystal display device is darkened. Have.
Moreover, in the said light diffusing plate, in order to support the optical film comprised on a light diffusing plate while improving light scattering property, the board thickness is shape | molded by the thickness of about 1-5 mm normally. Therefore, the light transmitted through the light diffusing plate is absorbed by this thickness, so that the liquid crystal screen display becomes dark.
Further, liquid crystal televisions tend to be thinner year by year, and accordingly, light diffusing plates are required to be thinner, and further light diffusibility is required to be improved.

Conventionally, the light diffusing plate used in direct type backlights diffuses the light emitted from the cold-cathode tube, which is the light source, and aims to reduce luminance unevenness (lamp image) due to the light source being visually recognized. However, even with the light diffusing plate, it is difficult to completely erase the lamp image.
That is, when the amount of the diffusing particles that impart light diffusibility is increased only for the purpose of completely erasing 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 emission surface of a light diffusion plate.
In such a 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 diffusion plate.

  As a measure to improve the reduction of the total light transmittance as described above, the brightness is improved by using a brightness enhancement film (Brightness Enhancement Film, hereinafter referred to as BEF) which is a registered trademark of 3M USA, and the liquid crystal display screen is improved. A method of brightening is known.

  FIG. 14 is a schematic cross-sectional view showing an example of the BEF arrangement, and FIG. 15 is a perspective view of the BEF. The BEF 185 is an optical film in which unit prisms 187 having a triangular cross section are periodically arranged in one direction on a member 186, and the unit prisms 187 have a size (pitch) larger than the wavelength of light. Is formed.

  The BEF 185 collects light from “off-axis” and redirects this light “on-axis” or “recycle” toward the viewer. Has the function of In other words, the BEF 185 can increase the on-axis luminance by reducing the off-axis luminance when the display is used (observation). Note that “on the axis” is a direction that coincides with the viewing direction F ′ of the viewer, and generally indicates a normal direction to the display screen.

However, when such a BEF 185 is used, a phenomenon occurs in which the light component due to the reflection / refractive action is unnecessarily emitted in the lateral direction without proceeding to the visual direction F ′ of the viewer.
That is, the light intensity distribution on the BEF 185 has the highest light intensity at an angle of 0 ° (corresponding to the axial direction) with respect to the visual field direction F ′ as shown by the broken line B in FIG. Near the angle ± 90 °, a small light intensity peak (side lobe) is generated, and the amount of light emitted from the lateral direction is increased.

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 lens sheet 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.
According to this optical film, as shown by a solid line A in FIG. 16, no side lobe appears in the light intensity distribution, and the light intensity in the viewing direction F ′ can be improved as compared with the broken line B.
JP 2007-103321 A JP 2007-12517 A JP 2006-195276 A JP 2007-213035 A

  However, even with a backlight using the optical film described in Patent Document 4 above, the lamp image cannot be completely erased, and light and dark appear in the image display. It was difficult.

  The present invention has been made in view of such problems, and an optical device capable of further reducing the lamp image and further improving the display quality of image display, and light using the same. An object is to provide a diffusion device, an optical sheet, a backlight unit, and a display device.

In order to solve the above problems, the present invention proposes the following means.
That is, an optical device according to the present invention is an optical device that controls an optical path of light emitted from a light source and emits it to an observer side, the light propagation layer disposed on the observer side, and the light propagation layer A plurality of light deflection lenses arranged at a constant pitch on the light source side surface, and the light deflection lens diffuses light incident substantially parallel to the normal direction of the surface of the light propagation layer. The oblique incident light incident at an incident angle φ of 20 ° or more with respect to the normal direction is deflected toward the normal direction, and the light intensity peak due to the oblique incident light is ±± It is characterized by being within a range of 10 °.

According to the optical device having such a feature, light incident on the light deflection lens substantially parallel to the normal direction of the surface of the light propagation layer, that is, light incident at an incident angle of 0 ° is transmitted by the light deflection lens. Since the light is diffused within a certain range, it is possible to prevent only the portion directly above the light source from becoming excessively bright.
Further, the oblique incident light incident at an incident angle φ of 20 ° or more with respect to the normal direction is raised toward the normal direction by the light deflection lens, so that the light intensity peak due to the oblique incident light has a normal line. Within ± 10 ° with respect to the direction. Therefore, it is possible to improve the front luminance at the portion where the light from the light source is incident obliquely, thereby preventing the portion from becoming dark.
Therefore, it is possible to prevent the portion directly above the light source from becoming excessively bright, and to prevent the portion where light is incident obliquely other than the portion directly above the light source from being darkened, so that the entire light passing through the optical device can be prevented. As a result, it is possible to remove the lamp image with certainty.

Further, in the optical device according to the present invention, a plurality of the light sources are arranged at a distance d in the normal direction to the light deflection lens and at an interval L along the arrangement direction of the light deflection lenses. The incident angle φ of the oblique incident light satisfies the following formula (1).

  According to the optical device having such a feature, the light intensity at the intermediate point between the adjacent light sources can be improved, so that the intermediate point is prevented from being darkened, and the entire light passing through the optical device is reduced. Brightness unevenness can be made uniform.

Further, in the optical device according to the present invention, a plurality of the light sources are arranged at a distance d in the normal direction to the light deflection lens and at an interval L along the arrangement direction of the light deflection lenses. In this case, the incident angle φ of the oblique incident light may satisfy the following formula (2).

  According to the optical device having such a feature, the light intensity at the dividing point when the distance between adjacent light sources is divided into three can be improved. It is possible to make the luminance unevenness of the entire light passing through the light more uniform.

Furthermore, in the optical device according to the present invention, the shape of the light deflection lens includes a lens top portion having an arcuate surface or a ridge line, and a lens inclined surface extending from the lens top portion to the light propagation layer, and faces each other. The distance between the lens inclined surfaces is formed so as to gradually decrease toward the top of the lens, the refractive index of the light propagation layer is n, the pitch of the light deflection lens is P, and the lens inclined surface The thickness T of the light propagation layer is defined as follows, where θ is the angle formed by the tangent line from the junction point where the lens is bonded to the substrate to the inclined surface of the lens and the surface opposite to the viewer of the substrate. It is preferable to satisfy Formula (3).

  By defining the thickness T of the light diffusing and transmitting layer based on this equation, the focal point of the light deflection lens can be surely positioned on the light propagation layer. Therefore, the light that has passed through the light deflection lens is once condensed inside the light propagation layer, and then diffused to the range where the diffused light from the adjacent light deflection lens is overlapped and emitted. Thus, the lamp image can be reduced more reliably.

  In the optical device, the lens inclined surface has a curved shape, and an angle formed between a tangent in the curved shape and a light source side surface of the light propagation layer continuously changes from 20 ° to 90 °. It is preferable.

A light diffusing device according to the present invention is a light diffusing device for controlling an illumination optical path, and includes any one of the above-described optical devices and a light diffusing substrate laminated on a viewer-side surface of the optical device. It is characterized by becoming.
According to such a light diffusing device, light that has passed through the optical device and has a uniform light intensity distribution is further diffused in the light diffusing substrate, so that the lamp image can be reduced more reliably. Is possible.

  Moreover, in the light diffusing device according to the present invention, the light diffusing substrate is formed by dispersing light diffusing particles in a transparent resin, and has a total light transmittance of 30 to 80% and a haze value of 95% or more. In addition, the light propagation layer preferably has a total light transmittance of 80% or more and a haze value of 95% or less.

  The optical sheet according to the present invention is an optical sheet for controlling an illumination optical path of a display, and the optical sheet is formed by overlapping an optical film on a surface on the observer side of any one of the light diffusion devices, The optical film is composed of a light-transmitting substrate and a condensing lens, and a plurality of condensing lenses are arranged at a constant pitch on the surface of the light-transmitting substrate on the observer side, and the shape of the condensing lens Is a convex curved surface shape.

In the optical sheet according to the present invention, a plurality of light masks and a light transmission opening for separating the light masks are provided between the optical film and the light diffusing device, and the light It is preferable that the transmission openings are respectively arranged at positions corresponding to the tops of the condenser lenses. That is, when the optical sheet is viewed from the observer side, the respective positions of the light transmission opening and the top of the condenser lens coincide.
Thereby, since most of the light to be transmitted can be emitted in the direction of the top of the condenser lens, the luminance in the front direction can be improved.

  Furthermore, in the optical sheet according to the present invention, the optical film and the light diffusing device may be integrally laminated via the light mask.

  Furthermore, in the optical sheet according to the present invention, dot-like or linear ribs are arranged between the optical film and the light diffusing device, and the optical film and the light diffusing device are interposed via the rib. It may be integrally laminated.

  A backlight unit according to the present invention includes any one of the optical devices described above, a light source, and an optical member that collects light from the light source that has passed through the optical device.

  The backlight unit according to the present invention may include any one of the light diffusing devices described above and a light source.

  Furthermore, the backlight unit according to the present invention may include any one of the above optical sheets and a light source.

  In any one of the backlight units described above, the light source is a linear light source and the shape of the light deflection lens is a lenticular lens, and when viewed in plan, the major axis direction of the lenticular lens and the The angle formed by the major axis direction of the linear light source may be 20 degrees or less.

  A display device according to the present invention includes an image display element that displays an image by transmitting or blocking light in pixel units, and any one of the backlight units described above.

  According to the optical device of the present invention, and the light diffusing device, optical sheet, backlight unit, and display device using the same, the portion directly above the light source is prevented from becoming excessively bright, and other than the portion directly above the light source. It is possible to prevent the portion where the light is incident from becoming dark. Therefore, it is possible to make the luminance unevenness of the entire light passing through the optical device uniform and to erase the lamp image reliably, and to improve the display quality of the image display.

Hereinafter, embodiments of an optical device, a light diffusion device, a backlight unit, and a display device of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an example of a display apparatus employing the optical device and the light diffusing device of this embodiment.
The display device 70 according to the embodiment of the present invention includes an image display element 35 and a backlight unit 55.
Further, in the backlight unit 55 according to the embodiment of the present invention, a plurality of light sources 41 are arranged in a lamp house (reflecting plate) 43, and the light diffusion device 25 and the optical member 2 are disposed thereon (observer side direction F). Are arranged in a single or a plurality. Note that the optical member 2 is not necessarily provided, and may be omitted. The light diffusion device 25 is configured by laminating a diffusion base material 26 on the optical device 24.
Under such a configuration, the light H emitted from the light source 41 is diffused by the light diffusing device 25, and is diffused, reflected, condensed, and color-shifted by the optical member 2 disposed thereon. Then, the light K emitted from the backlight unit 55 enters the image display element 35 and is emitted to the observer side F.

  The light source 41 supplies light to the image display element 35 via the light diffusion device 25 and the optical member 2. As the light source 41, a plurality of linear light sources are used, and examples thereof include a fluorescent lamp, a cold cathode fluorescent lamp (CCFL), an EEFL, or a linearly arranged LED.

  The reflection plate 43 is disposed on the opposite side of the plurality of light sources 41 from the observer side F, and observes light emitted in the direction opposite to the observer side F among light emitted from the light source 41 in all directions. Reflect toward the person side F. Thereby, the utilization efficiency of the light radiate | emitted from the light source 41 can be improved. The reflection plate 43 may be any member that reflects light with high efficiency. For example, a general reflection film or a reflection plate is used.

  The light diffusing device 25 is configured by laminating a diffusing base material 26 on the optical device 24, and the surface 26 a of the diffusing base material 26 opposite to the observer side F is formed on the propagation layer 23 of the optical device 24. The surface 23b on the observer side F is formed to overlap.

The optical device 24 includes a light deflection lens 28 and a light propagation layer 23, and the light deflection lens 28 is disposed toward the light source 41 side.
The optical device 24 deflects the light H incident from the incident surface of the light deflecting lens 28, then emits the light H to the light propagation layer 23, and emits diffused light from the light emission surface of the light propagation layer 23.

The light deflection lens 28 in the optical device 24 can be formed on the surface 23a opposite to the observer side F of the light propagation layer 23 using an electron beam curable resin such as a UV curable resin.
In addition to the above UV molding, the light deflection lens 28 is made of PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), COP (cycloolefin polymer), acrylonitrile styrene copolymer, acrylonitrile polystyrene copolymer. You may form by the injection molding method or the hot press molding method using coalescence etc. Further, the light deflection lens 28 may be formed using a radiation curable resin.

The light propagation layer 23 in the optical device 24 and the light diffusing device 25 is preferably made of a transparent resin made of a thermoplastic resin. For example, a polycarbonate resin, an acrylic resin, a fluorine acrylic resin, a silicone acrylic Examples thereof include resins, epoxy acrylate resins, polystyrene resins, cycloolefin polymers, methyl styrene resins, fluorene resins, PET, polypropylene, acrylonitrile styrene copolymers, acrylonitrile polystyrene copolymers, and the like. The light propagation layer 23 may be extended in at least a uniaxial direction.
In order to effectively spread and propagate the light deflected by the light deflection lens 28, it is more desirable that the light propagation layer 23 does not include a light diffusing element.

  Further, in this light propagation layer 23, the total light transmittance is preferably 80% or more. When the total light transmittance is less than 80%, the luminance of the light emitted to the observer side F is lowered, which is not preferable. In this respect, if the total light transmittance is 80% or more, the luminance of the light emitted to the observer side F is not lowered. The total light transmittance is a measured value based on JIS K7361-1.

  Here, the light propagation layer 23 has a function of effectively spreading and propagating the incident light deflected by the light deflection lens 28 and causing the incident light to enter the diffusion base material 26. Therefore, in order to obtain a sufficient light diffusion effect, the haze value of the light propagation layer 23 is preferably 95% or less. The haze value is a measured value based on JIS K7136.

  And the light diffusing device is comprised by laminating | stacking the diffusion base material 26 on the surface 23b of the observer side F of the light propagation layer 23 in such an optical device 23. FIG.

The diffusion base material 26 is formed by dispersing a light diffusion region in a transparent resin.
As the transparent resin, 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 resin, a polystyrene resin, a cycloolefin polymer Methyl styrene resin, fluorene resin, polyethylene terephthalate (PET), polypropylene, acrylonitrile styrene copolymer, acrylonitrile polystyrene copolymer, and the like can be used.

  When a thermoplastic resin is used, for example, polyethylene terephthalate (PET), polyethylene-2, 6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, cyclohexanedimethanol copolymer polyester resin, isophthalic acid copolymer polyester resin, sporoglycol copolymer Polyester resins such as polyester resins and 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, poly Ethers, polyester amides, polyether esters, polyvinyl chloride, cycloolefin polymers, and copolymers comprising these components, And it will be employed as mixtures of these resins.

The light diffusion region dispersed in such a transparent resin is preferably made of light diffusion particles. This is because suitable diffusion performance can be easily obtained.
Further, 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. The size and shape of the transparent particles are not particularly limited.

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, the film thickness of the diffusion base material 26 can be made thinner.
Examples of such a diffusion base material 26 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.

  When light diffusion particles are used as the light diffusion region, the thickness of the diffusion base material 26 is preferably 0.1 to 5 mm in order to obtain optimum diffusion performance and brightness. This is because when the thickness is less than 0.1 mm, the diffusion performance is insufficient, and when it exceeds 5 mm, the amount of resin is large and the luminance decreases due to absorption.

  The diffusion base material 26 made of a thermoplastic resin may be stretched at least in the uniaxial direction. This is because bubbles can be generated around the filler by stretching in at least one axial direction.

When bubbles are used as the light diffusion region, the thickness of the diffusion base material 26 is preferably 25 to 500 μm.
When the thickness of the diffusion base material 26 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. Further, when the thickness of the diffusing substrate 26 exceeds 500 μm, there is no particular problem with respect to optical performance. However, since the rigidity is increased, it is difficult to process into a roll shape, and a slit cannot be easily formed. Since the advantage of the thinness obtained by comparison becomes small, it is not preferable.

The diffusion base material 26 preferably has a total light transmittance of 30% to 80%. If the total light transmittance is less than 30%, the brightness of the emitted light to the observer side F is lowered, which is not preferable. Conversely, if the total light transmittance exceeds 80%, the diffusion performance is low. This is not preferable because it becomes insufficient and the uniformity of in-plane luminance deteriorates.
Further, the diffusion base material 26 preferably has a haze value of 95% or more. When the haze value is less than 95%, the diffusion performance becomes insufficient and the uniformity of in-plane luminance is deteriorated, which is not preferable.

In such a light diffusing device 25, it is desirable that the light propagation layer 23, the diffusion base material 26, and the light deflection lens 28 are integrally formed by an extrusion method, a multilayer injection molding method, or the like. After the material 26 is integrally formed as a plate-like member by an extrusion method or the like, the light deflection lens 28 is subjected to UV molding or the like on the surface 23a opposite to the observer side F of the light propagation layer 23 as described above. It may be formed.
In the light diffusing device, before the light propagation layer 23 and the diffusion base material 26 are integrally formed, the light deflection lens 28 is UV-molded on the surface 23a opposite to the observer side F of the light propagation layer 23. May be.

  In this light diffusing device 25, the diffusion base material 26 and the light propagation layer 23 are separately formed by an extrusion method, injection molding, or the like, and then integrally formed by an adhesive or an adhesive material. The lens 28 may be formed by UV molding or the like. For example, as the adhesive material or the adhesive material, the diffusion base material 26 and the light propagation layer 23 can be bonded using a generally used laminate or the like.

  The optical device 24 and the light diffusing device 25 having such a configuration are not limited to liquid crystal devices, but may be any devices that perform optical path control, such as rear projection screens, solar cells, organic or inorganic EL, and lighting devices. Can also be used.

  The optical member 2 diffuses, reflects, condenses, and shifts the light from the light source 41 that has passed through the light diffusing device 25 and transmits it to the image display element 35. What is the light source 41 side of the light diffusing device 25? It is disposed along the opposite surface, that is, the surface 26 b on the viewer side F of the diffusion base material 26.

  The backlight unit 55 is configured by stacking the reflection plate 43, the light source 41, the light diffusion device 25 including the optical device 24 and the diffusion base material 26, and the optical member 2 in this order.

And the display apparatus 70 is comprised by laminating | stacking the image display element 35 on the observer side F of such a backlight unit 5. FIG.
The image display element 35 includes two polarizing plates (polarizing films) 31 and 33 and a liquid crystal panel 32 sandwiched therebetween. The liquid crystal panel 32 is configured, for example, by filling a liquid crystal layer between two glass substrates. The light K emitted from the backlight unit 50 is incident on the liquid crystal unit 32 via the polarizing filter 33 and is emitted to the observer side F via the polarizing filter 31.

Such an image display element 35 is preferably an element that displays an image by transmitting / blocking light in pixel units in order to display an image with high image quality.
The image display element 35 is preferably a liquid crystal display element. A liquid crystal display element is a typical element that transmits / shields light in pixel units and displays an image, and can improve image quality and reduce manufacturing cost compared to other display elements. Can do.
In addition, you may arrange | position a diffusion film, a prism sheet, a polarization separation reflection sheet, etc. to the display apparatus 70. FIG. By doing so, the image quality can be further improved.

  The schematic configuration of the display device 70 according to the embodiment has been described above. Hereinafter, the functions of the optical device 24 and the light diffusing device 25 will be described with reference to more detailed configurations.

FIG. 2A is a diagram for explaining an optical path of light incident on the light deflection lens 28 of the optical device 24 at an incident angle of 0 ° (that is, substantially parallel to the normal direction of the surface of the light propagation layer 23). It is.
In FIG. 2A, the light sources 41 are arranged at a constant pitch in the Ve direction, which is the arrangement direction of the light deflection lenses 28, in the reflection plate 43 (not shown in FIG. 2A), as in FIG. Has been.

  As shown in FIG. 2A, the light H emitted from the light source 41 is incident from the surface opposite to the observer side F of the optical device 24, that is, the light deflection lens 28. At this time, the light H is deflected by the light deflection lens 28 and diffused with a certain spread angle.

Here, in the optical device 24, the tangent m of the lens inclined surface at the junction 30 between the lens inclined surface 28 b of the light deflection lens 28 and the light propagation layer 23, and the side opposite to the observer side F of the light propagation layer 23. When the angle formed by the surface 23a is θ, the pitch of the light deflection lens 28 is P, and the refractive index of the light propagation layer 23 is n, the thickness T of the light propagation layer 23 satisfies the following expression (3): It is preferable.

  When the relationship of the above expression (3) is satisfied, the light H from the light source deflected by the light deflection lens 28 is condensed inside the light propagation layer 27 as shown in FIG. After focusing, the light deflected by the adjacent light deflection lens 28 is diffused to the overlapping range and emitted. Therefore, it becomes possible to improve the diffusibility of the light incident perpendicularly to the light deflection lens 28 of the optical device 24, and the lamp image can be further reduced.

  Note that the pitch P of the light deflection lens 28 is defined as a distance between two points joined to the light propagation layer 23 when the light deflection lens 28 is viewed in cross section, and in particular, the pitch P is 10 μm or more and 600 μm or less. Is desirable. When the pitch P of the light deflection lens 28 is smaller than 10 μm, the structure period approaches the wavelength, and thus the influence of diffraction cannot be ignored. When the pitch P of the light deflection lens 28 exceeds 600 μm, the diffusion performance is high. Although there is no problem, the thickness T of the light propagation layer 23 becomes very thick, which is an obstacle to thinning. In this case, it is desirable to set the thickness of the light propagation layer 23 to be 2 mm or less.

Furthermore, it is more preferable that not only the diffused light from the adjacent light deflection lenses 28 overlap but also the light deflected by the two adjacent light deflection lenses 28 is mixed in the light propagation layer 23. Thereby, it is possible to further improve the diffusion performance. In this case, it is necessary that the thickness T of the light propagation layer 23 satisfies the following expression (4).

  The light deflected by the two light deflection lenses 28 is mixed in the light propagation layer 23 to further improve the diffusion performance. Therefore, even in the state where the distance from the light source 41 is close to 10 mm or less, the lamp It becomes possible to reduce / disappear the image.

FIG. 2B is a diagram for explaining the optical path of light (obliquely incident light) incident on the light deflection lens 28 of the optical device 24 with a constant incident angle.
In the optical device 24 of the present embodiment, the oblique incident light H incident at an incident angle φ (20 ° or more in the present embodiment) from the normal direction N of the surface of the optical device 24 is transmitted by the light deflection lens 28. It is deflected so as to rise in the normal direction N. Thereby, the light intensity peak due to the deflected light of the oblique incident light H falls within a range of ± 10 ° with respect to the normal direction N as shown in FIG.

More specifically, the light deflection lens 28 in the present embodiment deflects the oblique incident light H incident at an incident angle φ defined by the following equation (1), so that the deflected light of the oblique incident light H is changed. The light intensity peak to be produced is emitted so as to be within a range of ± 10 ° with respect to the normal direction N.

Details of the equation (1) will be described with reference to FIG.
In the above equation (1), L indicates the distance between the adjacent light sources 41, and d indicates the distance between the light source 41 and the light deflection lens 28. According to this, the obliquely incident light emitted from the light source 41 with an incident angle φ and incident on the light deflection lens 28 is an intermediate point (L / 2) between the adjacent light sources 41 as shown in FIG. ), Or a portion facing an intermediate point (3L / 2) between the adjacent light source 41 and the two adjacent light sources 41 with the light source 41 interposed therebetween.

  Then, the oblique incident light incident on the position facing the intermediate point (L / 2, 3L / 2) is deflected so as to rise in the normal direction N by the light deflection lens 28, so that the oblique light at the intermediate point is inclined. The light intensity peak produced by the deflected light of the incident light is within a range of ± 10 ° with respect to the normal direction N. As a result, the light intensity at the intermediate position is improved, and a pseudo light source can be created at an intermediate point between adjacent light sources 41 that should be dark.

On the other hand, separately from the above, the light deflection lens 28 in the present embodiment deflects the oblique incident light H incident at an incident angle φ defined by the following equation (2), thereby deflecting the oblique incident light H. May be emitted so that the light intensity peak produced by the laser beam is within a range of ± 10 ° with respect to the normal direction N.

Details of the above equation (2) will be described with reference to FIG.
In the above formula (1), L represents the distance between the adjacent light sources 41, and d represents the distance between the light sources and the light deflection lens 28. According to this, the oblique incident light emitted from the light source 41 with the incident angle φ and incident on the light deflection lens 28 is 1 when the adjacent light sources 41 are divided into three as shown in FIG. The incident light is incident on a total of two locations opposite to the / 3 division point (L / 3) and the 2/3 division point (2L / 3).

  Then, the oblique incident light incident on the portions facing these division points (L / 2, 3L / 2) is deflected so as to rise in the normal direction N by the light deflection lens 28, so that The light intensity peak produced by the deflected light of the oblique incident light is within a range of ± 10 ° with respect to the normal direction N. As a result, the light intensity at the dividing point can be improved, and a pseudo light source can be created at the dividing points of 1/3 and 2/3 of the adjacent light sources 41 that should originally be dark.

As described above, in the optical device 24, the light incident on the light deflection lens 28 substantially parallel to the normal direction N of the surface of the light propagation layer 23, that is, the light incident on the light deflection lens 28 at an incident angle of 0 °. The light is deflected and diffused by the light deflection lens 28. Therefore, it is possible to prevent only the portion directly above the light source 41 from becoming excessively bright.
Further, the oblique incident light incident at an incident angle φ of 20 ° or more with respect to the normal direction N is deflected by the light deflection lens 28 so as to rise in the normal direction, and the oblique incident light The light intensity peak due to the deflected light is within a range of ± 10 ° with respect to the normal direction. Thereby, the front brightness | luminance in the part into which the light from the light source 41 inclines diagonally, for example, the above intermediate points and division points, can be improved.
Accordingly, the portion directly above the light source 41 is prevented from becoming excessively bright, and the portion where the light is incident obliquely other than the portion directly above the light source 41 (for example, the intermediate point (L / 2) as described above, the dividing point (L / 3, 2L / 3)), it is possible to prevent darkening by forming a pseudo light source, so that the luminance unevenness of the entire light passing through the optical device 24 is made uniform and the lamp image is surely obtained. It can be erased.

  Furthermore, according to the light diffusion device 25 formed by adding the diffusion base material 26 to the optical device 24 as described above, since the light uniformized as described above is diffused by the diffusion base material 26, the light source 41 The emitted light can be more effectively uniformized. Therefore, it is possible to more reliably reduce the lamp image.

  Here, the light deflection lens 28 may have any lens shape, but it is desirable to have a triangular prism shape as shown in FIG. This is because the lens can be easily molded, and the incident light H from the front can be largely deflected, and the obliquely incident light H can be deflected in the normal direction N.

  Moreover, the curved prism shape as shown in FIG. Since the tangent line at each point of the inclined lens surface 28b continuously changes, the incident light H from the front can be deflected to various angles and the oblique incident light H can be deflected in the normal direction N. This is because it can be done.

Furthermore, the lens shape of the light deflection lens 28 may be an aspherical shape as shown in FIG. 6, particularly an aspherical shape having a reduced radius of curvature at the tip, such as a parabola or a hyperbola. It is desirable that the shape is defined by the formula.

  Here, z is a position function in the height direction of the unit lens, r is a position variable in the width direction of the unit lens, and when the pitch of the unit lens is normalized to 1, each coefficient k, ( 1 / (2R) + A), B, C are within the range of −1 ≧ k, −5 <(1 / (2R) + A) <5, −10 <B <10, −30 <C <30. It is desirable to be. In the parabolic or hyperbolic lens designed by the above formula, the radius of curvature of the lens apex portion 28a is small, and the light H incident from the front on the lens apex portion 28a having a small radius of curvature is largely deflected and is incident obliquely. This is because H can be deflected in the normal direction N.

  The light deflection lens 28 may be configured by combining a plurality of the above lens shapes. For example, a triangular prism may be combined on a convex curved lens, or two curved triangular prisms may be shifted in the Ve direction and overlapped. This is because the diffusion performance is further increased by the diffusion effect of two or more lens shapes.

  The light diffusing device 25 may be formed by integrally forming a diffusion base material 26, a light propagation layer 23, and a light deflection lens 28 by a multilayer extrusion method as shown in FIG. 7A. At this time, the light diffusing device 25 may be extended in at least one axial direction. By using the multilayer extrusion method in this way, the manufacturing process can be simplified and made more efficient, and the manufacturing cost can be reduced.

Further, as shown in FIG. 7B, the light diffusing device 25 is formed into a sheet shape, and is then applied to the surface 23a opposite to the observer side F of the light propagation layer 23 by a fixing layer 20 by lamination or the like. It can also be pasted. In this case, it is preferable to include an ultraviolet absorber in the light deflection lens 28 formed into a sheet shape. By including an ultraviolet absorber in the light deflection lens 28 formed into a sheet shape, it is possible to prevent peeling of the fixed layer 20 due to ultraviolet degradation.
Here, the fixing layer 20 can be formed using a pressure-sensitive adhesive or an adhesive, and as the pressure-sensitive adhesive and the adhesive, urethane-based, acrylic-based, rubber-based, silicone-based, vinyl-based resins, or the like are used. . In addition, as the pressure-sensitive adhesive and the adhesive, those which are pressed and adhered in a one-pack type, those which are cured by heat or light can be used, and those which are cured by mixing two liquids or a plurality of liquids are used. be able to.
Further, a filler may be dispersed in the fixed layer 20. Thereby, the elastic modulus of the bonding layer can be increased.
Moreover, as a formation method of the fixed layer 20, various methods, such as a method of directly applying to the bonding surface and a method of pasting together those prepared as a dry film, can be employed. . It is preferable to prepare the fixed layer 20 as a dry film because it can be easily handled in the manufacturing process.

Moreover, it is desirable that the fixed layer 20 has an effect of preventing warpage. In this respect, warping of the light diffusing device 25 itself can be prevented by adjusting the thermal linear expansion coefficient of the fixed layer 20 to be substantially the same as the thermal linear expansion coefficient of the diffusion base material 26.
Furthermore, it is possible to prevent warping of the light diffusion device 25 itself by matching the thermal linear expansion coefficient of the light deflection lens 28 formed into a sheet shape so as to be substantially the same as the thermal linear expansion coefficient of the diffusion base material 26. It becomes.
The thickness of the light deflection lens 28 formed into a sheet is preferably 10 μm to 1 mm. Furthermore, it is desirable that it is 25 micrometers-500 micrometers. This is because if the thickness of the light deflection lens 28 formed into a sheet shape is too thin, wrinkles or the like are generated, and if it is too thick, bonding to the light propagation layer 23 is not easy.
Here, the base material region of the light deflection lens 28 formed into a sheet shape can be regarded as the light propagation layer 23. Therefore, by forming the light deflection lens 28 into a thick sheet, the thickness of the light propagation layer 23 can be reduced. Further, it can be directly bonded to the diffusion base material 26.

The surface of the light deflection lens 28 may have fine irregularities. Thereby, the deflection effect by the light deflection lens 28 can be further enhanced. At this time, the surface roughness Ra is desirably in the range of 0.1 μm to 10 μm. This is because it is difficult to obtain a deflection effect with a concavo-convex structure of less than 0.1 μm, and a concavo-convex structure of more than 10 μm is substantially meaningless because it itself becomes the optical deflection lens 28.
As a method for forming fine irregularities formed on the surface of the light deflection lens 28, for example, a method of imparting roughness to the surface of the light deflection lens 28 itself or a molding die by etching or sandblasting, or the light deflection lens. For example, 28 fine molds may be cut into finer irregularities.

  Further, the light deflection lens 28 may not have the lens shape as described above as long as it deflects the incident light H. For example, the light deflection lens 28 may be a diffusion layer made of a resin filler or bubbles. This is because the incident light H is deflected by the light deflection lens 28, the light deflected by the light propagation layer 23 is expanded, and further diffused by the diffusion base material 26, thereby improving the diffusion performance.

Further, in the light diffusion device 25, the light propagation layer 23 may have a multilayer structure of at least two layers as shown in FIG. At this time, when the refractive index of the layer 23A on the light deflection lens 28 side is n1, the refractive index of the layer 23B on the diffusion base material 26 side is n2, and the refractive index of the light deflection lens 28 is n0, the following equation (6) is obtained. It is desirable to satisfy.

The above equation (6) will be described with reference to FIG.
In FIG. 8A, when light H enters the light deflection lens 28, the light H is deflected by the refractive index of air and the refractive index n0 of the light deflection lens 28. At this time, since the refraction angle increases as the refractive index n0 of the light deflection lens 28 increases, it is preferable that the refractive index n0 of the light deflection lens 28 be larger.

In FIG. 8, light is emitted from the light source 41 at the interfaces of the light deflection lens 28, the layer 23A of the light propagation layer 23 on the light deflection lens 28 side, and the layer 23B of the light propagation layer 23 on the diffusion base material 26 side. When moving from the side to the observer side F, the case where the refractive index at the interface increases is indicated by a two-dot chain line, the case where the refractive index does not change is indicated by a dotted line, and the case where the refractive index decreases by a solid line.
For example, when the light deflected by the light deflection lens 28 enters the light propagation layer 23, when n0> n1, that is, when the refractive index is low, the light is deflected in the direction shown by the solid line. Since the angle formed between the deflected light and the surface 23a opposite to the observer side F of the light propagation layer 23 is reduced, the diffusion performance is improved.

On the other hand, when n0 <n1, that is, when the refractive index increases, the light is deflected in the direction shown by the two-dot chain line. Since the angle formed between the deflected light and the surface 23a opposite to the observer side F of the light propagation layer 23 is increased, the diffusion performance is deteriorated.
Similarly, at the interface between the layer 23A on the light deflection lens 28 side of the light propagation layer 23 and the layer 23B on the diffusion base material 26 side of the light propagation layer 23, when n1> n2, that is, the refractive index is lowered. In this case, the diffusion performance is improved.

  Therefore, the refractive index n0 of the light deflection lens 28 and the refractive index n1 of the layer 23A on the light deflection lens 28 side of the light propagation layer 23 are the same or the refractive index n0 of the light deflection lens 28 is larger. desirable. Also. The refractive index n1 of the layer 23A on the light deflection lens 28 side of the light propagation layer 23 is equal to the refractive index n2 of the layer 23B on the diffusion base material 26 side of the light propagation layer 23, or the light deflection lens 28 of the light propagation layer 23. It is desirable that the refractive index n1 of the side layer 23A is larger.

In the light propagation layer 23 having such a two-layer structure, the thickness of the layer 23B on the diffusion base material 26 side of the light propagation layer 23 is thicker than the thickness of the layer 23A on the light deflection lens 28 side. More desirable. This is because the light can be greatly expanded in the layer 23B of the light propagation layer 23 on the diffusion base material 26 side.
Further, as shown in FIG. 8B, the point where the light incident on both ends of the unit lens of the light deflection lens 28 is deflected and intersects is located in the layer 23A of the light propagation layer 23 on the light deflection lens 28 side. It is desirable to do.
Further, when the light propagation layer 23 has a multilayer structure of at least two layers, the farthest intersection point of the light deflection lens 28 is opposite to the light exit surface of the light deflection lens 28 (that is, the observer side F of the light propagation layer 23). It may be contained in a layer in contact with the side surface 23a). As a result, since the farthest intersection point is at a point close to the light deflection lens 28 in the light propagation layer 23, light can be diffused greatly.

  The light propagation layer 23 having such a multilayer structure can be formed by a plurality of layers having different refractive indexes by a multilayer extrusion method or the like. Further, the light deflection lens 28 is formed into a sheet shape using a material having a refractive index higher than that of the light propagation layer 23 on the light propagation layer 23 formed by an extrusion method or an injection molding method, and is bonded by a laminating method or the like. Can also be realized.

  Furthermore, by using the light propagation layer 23 having a multilayer structure, it is possible to prevent the optical device 24 and the light diffusion device 25 from warping. In this case, warpage of the optical device 24 and the light diffusing device 25 is prevented by matching the thermal linear expansion coefficient of the layer farthest from the viewer side with the thermal linear expansion coefficient of the diffusion base material 26 to approximately the same level. Can do. Further, the warp of the optical device 24 and the light diffusion device 25 can also be prevented by adjusting the thickness of the light propagation layer 23.

  In addition, in the light diffusing device 25, as shown to Fig.9 (a), the surface 26b of the observer side F of the diffusion base material 26 may be provided with uneven | corrugated shape. Thereby, compared with the case where the surface 26b on the observer side F of the diffusing substrate 26 is substantially flat (see FIG. 9B), the emission surface with various angles is formed, so that the light is emitted to a wider range. , The diffusion performance is improved and the lamp image is reduced / disappeared. An example of the uneven shape imparted to the observer side is a light diffusion lens 21 that diffuses light more.

The light diffusing lens 21 preferably has a triangular prism shape as shown in FIG. This is because lens molding is easy and the direction of the emitted light can be easily controlled.
Further, it may have a convex curved lens shape as shown in FIG. This is because the emission performance can be improved because the exit surface can be set at various angles.
Furthermore, an aspherical shape as shown in FIG. This is because the radius of curvature at the top can be reduced, and the diffusion performance is increased.
Furthermore, it is desirable that the light diffusing lens 21 is a curved triangular prism as shown in FIG. This is because there is no surface parallel to the viewer-side surface 26b of the diffusion base material 26, and the exit surface can be set at various angles, so that the diffusion performance is improved.
Further, the light diffusing lens 21 can combine a plurality of the above lens shapes. For example, as shown in FIG. 10E, it may be a shape in which a triangular prism is combined on a convex curved lens. This is because the diffusion performance is further increased by the diffusion effect of two or more lens shapes. In addition, the above-described lens shape can be adopted as the light deflection lens 28.

The light diffusing lens 21 may be arranged by appropriately combining a plurality of the above-described lenses. For example, a diffusion lens 21 having a high diffusion performance may be disposed in a region directly above the light source 41, and a diffusion lens 21 having a low diffusion performance may be disposed between the light source 41 and the light source 41.
On the other hand, when a diffusing lens 21 is disposed on the surface of the diffusing substrate 26, for example, when a lens sheet is disposed as the optical member 2, moire interference fringes may occur between the diffusing lens 21 and the lens sheet. Therefore, a method of matching the periodic structure of the diffusing lens 21 and the periodic structure of the lens sheet 2 with a pitch at which moire interference fringes do not occur, or forming an angle with each other, or placing a diffusing film as the optical member 2 or the like. It is necessary to apply.

  Next, an embodiment of an optical sheet according to the present invention, a backlight unit using the same, and a display device will be described. FIG. 11 is a schematic cross-sectional view illustrating an example of a display device using the optical sheet of the embodiment.

As shown in FIG. 11, the display device 70 includes an image display element 35 and a backlight unit 55. The backlight unit 55 includes a reflector 43, a light source 41, and an optical sheet 52 stacked in this order. It is constituted by.
The optical sheet 52 is configured by laminating the optical film 1 with the fixed layer 20 on the light diffusion device 25 described above.

The optical film 1 includes a light-transmitting substrate 17 and a condensing lens 16 having a convex curved surface. A plurality of condensing lenses 16 are arranged at a constant pitch on a surface 17b of the light-transmitting substrate 17 on the observer side. Is formed.
In this way, by arranging the condensing lens 16 on the surface 17b on the observer side of the light transmissive substrate 17, the light passing through the light diffusion device 25 is condensed on the observer side F, and the observer side It is possible to improve the brightness of F.

Examples of the shape of the condenser lens 16 include a triangular prism shape. Since the triangular prism has a high light condensing property in the front direction, an optical sheet 52 with high brightness can be obtained. The shape of the condenser lens 16 may be a convex curved surface. Since light is emitted not only in the front direction but also in various directions, the optical sheet 52 having a wide visual field range can be obtained.
Furthermore, the shape of the condensing lens 16 is not limited to the shape described above, and can be appropriately selected depending on the light distribution characteristics required for the display to be used. Specifically, in addition to the above, a microlens shape, a polygonal pyramid shape including a triangular pyramid and a quadrangular pyramid may be employed.

In this optical sheet 52, the surface 17a opposite to the observer side F of the light transmissive substrate 17 is a substantially flat surface, and a plurality of light masks 22 are formed on the surface 17a. The light diffusing device 25 is joined through the gap.
As a material of the light transmissive substrate 17, a thermoplastic resin, a thermosetting resin, or the like can be used, and the material used for the light diffusion device 25 described above may be used. Thereby, it is possible to suppress the warp generated in the optical sheet 52.

In general, when lenses are formed on one surface and the other surface of one member, moire interference fringes may occur. However, in the optical sheet 52, the condensing lens 16 and the light deflection lens 28 Since the diffusion base material 26 is inserted between them, the generation of the moire interference fringes as described above can be prevented.
Further, it is not necessary to form a diffusing element between the condensing lens 16 and the diffusing substrate 26, and the optical film 1 is bonded to the surface 26b on the observer side F of the diffusing substrate 26 without unevenness. Furthermore, it is desirable that the viewer-side surface 26b of the diffusion base material 26 is substantially flat.

As shown in FIG. 11, a plurality of light masks 22 and light transmission openings (air layers) 100 that separate the light masks 22 are provided between the optical film 1 and the light diffusion device 25. ing. The pitch of the optical mask 22 and the air layer 15 is substantially the same as the pitch of the condenser lens 16.
The position of the optical mask 22 is formed at a location corresponding to the position of the valley portion 13 of the condenser lens 16. Therefore, the position of the air layer 100 is provided at a position corresponding to the top portion 16 a of the condenser lens 16.

  Such an optical mask 22 is made of a highly light-shielding material, and is formed at a location corresponding to the position of the valley portion 13 of the condenser lens 16 formed on the surface 17b on the viewer side F. Therefore, most of the light incident on the optical film 1 passes through the air layer 100 formed between the optical masks 22 and enters the condenser lens 16. Therefore, the light that has passed through the light diffusing device 25 can be efficiently emitted in the front direction (observer side) F.

  Moreover, the optical mask 22 can be comprised from light-reflective members, such as a metal material and a white reflective material, for example. In this case, the light reflected by the light mask 22 is returned into the diffusion base material 26 that constitutes the light diffusion device 25, and after being diffused again by the diffusion base material 26, a part of the light again enters the optical film 1. Incident light is emitted from the light diffusion device 25 to the light source side. Then, after being reflected by the reflection plate 43, it is incident again on the light diffusion device 25 and diffused, and is incident again on the optical film 1. By repeating such steps, most of the light from the light source 41 can be efficiently emitted to the observer side F.

  When the optical mask 22 is composed of a light reflective member, the reflectance is preferably 80% or more. Thereby, since most of the light incident on the optical film 1 can be incident from the air layer 100 to the condenser lens 16, the luminance on the observer side F can be improved. On the other hand, when the reflectance is less than 80%, the amount of light transmitted through the light mask 22 increases, and the amount of inefficient light incident on the condenser lens 16 increases. It will cause.

  As a method for producing such an optical film 1, for example, a method by self-alignment can be mentioned. The condensing lens 16 is formed on the observer-side surface 17b of the light-transmitting substrate 17, and a photosensitive adhesive resin is bonded to the surface 17a opposite to the observer-side F of the light-transmitting substrate 17. By irradiating UV light from the condenser lens 16 side, the photosensitive adhesive resin at a position corresponding to the top of the condenser lens 16 is exposed to cure and lose adhesiveness. Thereafter, by transferring the optical mask 22, the optical mask 22 can be formed at a position corresponding to the valley portion 13 of the condenser lens 16.

The optical sheet 52 is manufactured by laminating the optical film 1 manufactured as described above to the light diffusion device 25 by the fixing layer 20 by lamination or the like. At this time, it is necessary to select the material of the fixed layer 20 so that the air layer 100 is maintained.
As the material of the fixing layer 20, for example, a pressure-sensitive adhesive or an adhesive can be used. Specifically, urethane-based, acrylic-based, rubber-based, silicone-based, vinyl-based resins, or the like can be used. In addition, as the pressure-sensitive adhesive and the adhesive, those which are pressed and adhered in a one-pack type, those which are cured by heat or light can be used, and those which are cured by mixing two liquids or a plurality of liquids are used. It is also possible.

  Further, a filler may be dispersed in the fixed layer 20. Thereby, the elastic modulus of the fixed layer 20 can be increased, and the fixed layer 20 can be prevented from entering the region of the air layer 100 when the optical film 1 and the light diffusion device 25 are integrated. Therefore, it becomes easy to hold the air layer 100.

  Moreover, as a formation method of the fixed layer 20, there are various methods such as a method of directly applying to the bonding surface and a method of pasting together those prepared in advance as a dry film. In particular, when the fixed layer 20 is prepared as a dry film, it is more preferable because it can be handled easily in the manufacturing process.

Here, when a stretched film typified by PET is used as the light-transmitting substrate 17 constituting the optical film 1, the optical sheet 52 is warped in a convex shape toward the light source 41 due to heat generated from the light source 41. The problem arises.
In this regard, it is possible to eliminate the warp problem by using a material of the layer 23A on the light deflection lens 28 side of the light propagation layer 23 having a multilayer structure of two or more layers as a warp prevention layer. That is, the layer 23A on the light deflection lens 28 side of the light propagation layer 23 generates a moment that warps the optical sheet 52 into a concave shape on the light source 41 side by heat, thereby canceling each moment, and as a result Warpage can be prevented. Specifically, the light deflection lens 28 is formed on the same material as the light transmissive substrate 17, and is bonded to the surface 23a opposite to the observer side F of the light propagation layer 23 by the fixed layer 20. Warpage can be prevented.

  The optical sheet 52 produced as described above is an optical film including the light diffusion device 25 that uniformly diffuses the light H from the light source 41, the air layer that efficiently enters the condensing lens 16, and the light mask 22. 1, it is possible to satisfy the diffusion / condensing function with one optical sheet 52, and to display a high-luminance image while completely erasing the lamp image. it can.

  As shown in FIG. 12, a plurality of ribs 29 are provided between the optical film 1 and the light diffusion device 25. The ribs 29 are arranged in a dot shape or a line shape and have a role of securing a sufficient air layer between the optical film 1 and the light diffusion device 25. At the time of the arrangement, the valley portion 13 of the condenser lens 16 and the linear rib 29 are arranged so as to coincide with each other, thereby suppressing a decrease in luminance, and moire interference between the rib 29 and the condenser lens 16. It is possible to prevent the stripes from occurring.

  As shown in FIG. 12A, the rib 29 may be formed on the surface 17a opposite to the viewer side of the light transmitting substrate 17 of the optical film 1, as shown in FIG. ), The light diffusion device 25 may be formed on the viewer-side surface 26b of the diffusion base material 26.

  Also in the display device 70 using such an optical sheet 52, the portion directly above the light source 41 is prevented from becoming excessively bright, and a pseudo light source is used for a portion where light is incident obliquely other than the portion directly above the light source 41. Since it can be prevented from becoming dark by forming, it is possible to make the luminance unevenness of the entire light passing through the optical device 24 uniform and to erase the lamp image with certainty.

The embodiment of the present invention has been described above, but the present invention is not limited to this, and can be appropriately changed without departing from the technical idea of the present invention.
For example, in the present embodiment, as shown in FIG. 13, the angle θ ₄₁ formed by the axial direction j of the light deflection lens 28 and the axial direction k of the light source 41 may be appropriately changed within a range of 20 degrees or less. In this case, the light source 41 is a linear light source, and the light deflection lens 28 is formed of a lenticular lens.
When the angle θ ₄₁ is 20 degrees or less, the lamp image of the light source 41 can be eliminated. On the contrary, when the angle θ ₄₁ exceeds 20 degrees, the effect of reducing the lamp image of the light source 41 becomes insufficient, and the lamp image of the light source 41 may be seen on the liquid crystal display screen. When the angle θ ₄₁ is 0 degrees, the effect of the light deflection lens 28 is the greatest, and therefore the angle θ ₄₁ is preferably 0 degrees.

  For the display device 70 using the light diffusion device 25 and the optical sheet 52 of the present invention, a test for examining the presence of luminance and luminance unevenness was performed.

First, a convex lenticular lens was used as the light deflection lens 28. In the convex lenticular lens, the pitch P is 150 μm, the angle θ formed by the tangent m at the junction 30 between the light propagation layer 23 and the convex lenticular lens, and the surface 23a opposite to the observer side of the light propagation layer 23 is 65. The top of the convex lenticular lens (approximately 20% range with respect to the pitch P) has a parabolic shape with a radius of curvature of about 25 μm and a height of 80 μm.
As a result, an optical deflection lens that strongly deflects in the normal direction N at an angle φ = 65 degrees of oblique incident light was obtained.
The materials of the light deflection lens 28, the light propagation layer 23, and the diffusion base material 26 were all made of polycarbonate (refractive index = 1.59).
The diffusion base material 26 contained an appropriate amount of a resin filler, whereby the total light transmittance was 55%, the haze value was 99%, and the thickness was 1.5 mm.
The light propagation layer 23 was made of a transparent material without containing a resin filler, and the total light transmittance was 87%. In the following examples, samples in which the thickness of the light propagation layer 23 was changed were produced.

(Comparative Example 1)
In the light diffusion device 25 set as described above, the thickness of the light propagation layer 23 was set to 150 μm, and the light diffusion device 25 was produced by a multilayer extrusion method.
Example 1
In the light diffusion device 25 set as described above, the thickness of the light propagation layer 23 was set to 600 μm, and the light diffusion device 25 was produced by a multilayer extrusion method.

The optical sheet 52 is formed by stacking the diffusion film, the 90-degree triangular prism sheet, and the diffusion film in this order on the surface on the viewer side F of the light diffusion device 25 of Example 1 and Comparative Example 1 manufactured as described above. Was made.
These are arranged in the backlight 56 having a CCFL interval of 16 mm, and the distance between the CCFL and the light diffusion device 25 is 5 mm, and the liquid crystal panel 35 is arranged on the observer side F of the backlight 56, whereby the display device 70 is arranged. Obtained.

Second, a convex lenticular lens sheet was used as the light deflection lens 28. In the convex lenticular lens, the pitch P is 150 μm, the angle θ formed by the tangent m at the junction 30 between the light propagation layer 23 and the convex lenticular lens, and the surface 23a opposite to the observer side of the light propagation layer 23 is 70. A parabolic shape having a curvature radius of about 25 μm and a height of 100 μm at the top of the convex lenticular lens (approximately 20% range with respect to the pitch P) was UV molded on a 75 μm PET substrate.
As a result, an optical deflection lens that strongly deflected in the normal direction N at an angle φ = 55 degrees of oblique incident light was obtained.
Further, the light propagation layer 23 and the diffusion base material 26 were polycarbonate (refractive index = 1.59).
The diffusion base material 26 contained an appropriate amount of a resin filler, whereby the total light transmittance was 55%, the haze value was 99%, and the thickness was 1.5 mm.
The light propagation layer 23 was made of a transparent material without containing a resin filler, had a thickness of 600 μm, and a total light transmittance of 87%.

(Example 2)
The condensing lenses 16 are arranged at a 150 μm pitch on a 75 μm PET substrate on the surface of the observer side F of the produced light diffusing device 25 so that the area of the light mask 22 is 50% of the pitch of the condensing lenses 16. Example 2 was obtained by integrally laminating the formed optical film 1 with an adhesive material to produce an optical sheet 52.
(Example 3)
Example 3 was obtained by arranging the diffusion film, the 90-degree triangular prism sheet, and the diffusion film in this order on the surface of the observer side F of the light diffusion device 25 produced as described above to form the optical sheet 52. .
Example 4
An optical film 1 in which a 90-degree triangular prism is molded on a 75-μm PET base material and dot-shaped ribs 29 having a size of 50 μm × 50 μm are formed on the surface facing the 90-degree triangular prism was produced using an adhesive. An optical sheet 52 that was integrally laminated on the surface of the light diffusing device 25 on the viewer side F was designated as Example 4.

  The samples of Examples 2 to 4 produced as described above were placed in the backlight 56 with a CCFL interval of 50 mm and the distance between the CCFL and the light diffusion device 25 being 18 mm, and a liquid crystal panel was placed on the observer side F of the backlight 56. By arranging 35, display devices 70 of Examples 2 to 4 were manufactured.

(Comparative Example 2)
Third, a convex lenticular lens was used as the light deflection lens 28. The angle P formed by the pitch P of the convex lenticular lens is 150 μm, the tangent m at the junction 30 between the light propagation layer 23 and the convex lenticular lens, and the surface 23a opposite to the observer side of the light propagation layer 23 is 70 degrees, The convex lenticular lens has an aspherical shape with a radius of curvature of about 60 μm and a height of 60 μm at the top (approximately 20% range with respect to the pitch P).
As a result, when the angle φ of obliquely incident light exceeds 10 °, an optical deflection lens that hardly deflects in the normal direction N ± 10 ° range is obtained.
The materials of the light deflection lens 28, the light propagation layer 23, and the diffusion base material 26 are all polycarbonate (refractive index = 1.59).
The diffusion base material 26 contained an appropriate amount of a resin filler, whereby the total light transmittance was 55%, the haze value was 99%, and the thickness was 1.5 mm.
The light propagation layer 23 was made of a transparent material without containing a resin filler, and a light diffusion device 25 having a thickness of 600 μm and a total light transmittance of 87% was obtained. On the surface of the light diffusion device 25 thus obtained on the viewer side F, the condensing lenses 16 are arranged on a 75 μm PET substrate at a pitch of 150 μm, and the area of the optical mask 22 is 50 of the pitch of the condensing lenses 16. An optical sheet 52 was obtained by integrally laminating the optical film 1 formed to be% with an adhesive.

  The sample of Comparative Example 2 produced as described above is placed in the backlight 56 having a CCFL interval of 50 mm and the distance between the CCFL and the light diffusion device 25 being 18 mm, and the liquid crystal panel 35 is placed on the observer side F of the backlight 56. The display device 70 of Comparative Example 2 was produced.

(Optical evaluation)
The display devices of this example and comparative example were evaluated by the following measuring methods.
(Front brightness evaluation)
The display device 70 was set to all white display, and the center of the screen was measured with a spectral radiance meter (SR-3A: manufactured by Topcon Technohouse).
(Luminance unevenness evaluation)
The display device 70 was set to display all white, and the entire screen was measured with a luminance unevenness measuring device (ProMetric 1200: manufactured by Radiant Imaging), and analysis was performed using luminance distribution data in a vertical direction of a plurality of cold cathode tubes.
Since the luminance distribution can be obtained as a wave distribution corresponding to the cold cathode fluorescent lamps, the luminance data corresponding to the five cold cathode fluorescent lamps at the center is extracted to calculate the average luminance, and then the luminance change with respect to the average luminance is calculated. (%) Was calculated. When the standard deviation σ of the luminance change was within 1%, it was determined that the diffusibility of the optical sheet was good.
Table 1 shows the measurement results of this example and the comparative example.

In Comparative Example 1, the light incident on the position of 2L / 3 with respect to the light source interval L was strongly deflected in the normal direction N, so that although two pseudo light sources were generated between the light sources, the light propagation layer Was too thin, the diffusion performance was insufficient, that is, NG.
In Example 1, the light source image disappeared and sufficient luminance was obtained. (OK determination).
In the second embodiment, the light incident on the position L / 2 with respect to the light source interval L is strongly deflected in the normal direction N, so that one pseudo light source is generated between the light sources and the light source image disappears. High luminance was obtained (OK determination).
In Example 3, the light source image disappeared and sufficient luminance was obtained (OK determination).
In Example 4, the light source image disappeared, and although the luminance was slightly lower than in Examples 2 and 3, it was at a level with no problem. (OK determination).
Since the comparative example 2 was a light deflecting lens that hardly deflected light having an incident angle exceeding 10 degrees in the normal direction N, the light source image was NG without disappearing.

It is a cross-sectional schematic diagram which shows an example of the display apparatus which employ | adopted the optical device and light-diffusion device of this embodiment. (A) is a figure explaining the optical path of the light which injects into the optical deflection lens of an optical device with the incident angle of 0 degree (namely, substantially parallel with respect to the normal line direction of the surface of a light propagation layer), (b). It is a figure explaining the optical path of the light (oblique incident light) which injects into the optical deflection lens 28 of the optical device 24 with a fixed incident angle. It is a figure which shows distribution of the light intensity peak by the deflection light of obliquely incident light. (A) is a figure explaining the detail of (1) Formula, (b) is a figure explaining the detail of (2) Formula. It is a figure which shows an example of the lens shape of a light deflection lens. It is a figure which shows an example of the lens shape of a light deflection lens. (A) is a figure which shows the form at the time of integrally molding a light-diffusion device, (b) is a figure which shows the form at the time of shape | molding a light deflection lens in a sheet form. (A) is a figure explaining the light rays in case a light propagation layer is a multilayer structure, (b) is a figure explaining the light rays in case a light propagation layer is a multilayer structure. (A) is a figure explaining the effect by which the unevenness | corrugation was added to the emission surface of the light-diffusion device, (b) is a figure explaining the case where the emission surface of a light-diffusion device is flat. It is a figure which shows an example of the lens shape of a light-diffusion lens. It is a cross-sectional schematic diagram of the display apparatus provided with the optical sheet. (A) is a cross-sectional schematic diagram of the display apparatus provided with the optical sheet, (b) is a schematic cross-sectional view of the display apparatus provided with the optical sheet. It is a figure which shows the case where the angle | corner with the axial direction of a light deflection lens and the axial direction of a light source is changed suitably in the range of 20 degrees or less. It is a cross-sectional schematic diagram which shows an example of arrangement | positioning of BEF. It is a perspective view of BEF. It is a graph which shows the relationship between light intensity and the angle with respect to a visual field direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical film 2 Optical member 16 Condensing lens 20 Fixed layer 21 Light diffusion lens
22 Optical mask 23 Light propagation layer 24 Optical device 25 Light diffusing device 26 Diffusion substrate 35 Image display element 41 Light source 43 Reflector plate 52 Optical sheet 55 Backlight unit 56 Backlight unit 70 Display device 72 Display device

Claims (16)

An optical device that controls an optical path of light emitted from a light source and emits the light toward an observer,
A light propagation layer disposed on the observer side, and a plurality of light deflection lenses arranged at a constant pitch on the light source side surface of the light propagation layer,
The light deflection lens diffuses light incident substantially parallel to the normal direction of the surface of the light propagation layer, and oblique incident light incident at an incident angle φ of 20 ° or more with respect to the normal direction. Is deflected toward the normal direction, and the light intensity peak due to the deflected light of the oblique incident light is set within a range of ± 10 ° with respect to the normal direction. When a plurality of the light sources are arranged at a distance d in the normal direction from the light deflection lens and at an interval L along the arrangement direction of the light deflection lenses,
The optical device according to claim 1, wherein an incident angle φ of the oblique incident light satisfies the following formula (1).

When a plurality of the light sources are arranged at a distance d in the normal direction from the light deflection lens and at an interval L along the arrangement direction of the light deflection lenses,
The optical device according to claim 1, wherein an incident angle φ of the oblique incident light satisfies the following formula (2).

The shape of the light deflection lens includes a lens top portion having an arcuate surface or a ridge line, and a lens inclined surface extending from the lens top portion to the light propagation layer, and a distance between the facing lens inclined surfaces is the lens. It is formed so as to gradually decrease toward the top,
The refractive index of the light propagation layer is n, the pitch of the light deflection lens is P, and the tangent line from the junction where the lens inclined surface is bonded to the substrate to the lens inclined surface is the observer of the substrate. When the angle between the opposite surface and θ is θ,
The optical device according to claim 2, wherein a thickness T of the light propagation layer satisfies the following formula (3).

  The lens inclined surface has a curved shape, and an angle formed between a tangent line in the curved shape and a light source side surface of the light propagation layer continuously changes from 20 ° to 90 °. The optical device according to claim 4. A light diffusing device for controlling an illumination optical path,
An optical device according to any one of claims 1 to 5,
A light diffusing device comprising: a light diffusing substrate laminated on a surface on the viewer side of the optical device. The light diffusing substrate has light diffusing particles dispersed in a transparent resin, has a total light transmittance of 30% or more and 80% or less, and a haze value of 95% or more,
The light diffusing device according to claim 6, wherein the light propagation layer has a total light transmittance of 80% or more and a haze value of 95% or less. An optical sheet for controlling an illumination light path of a display,
The optical sheet is formed by overlapping an optical film on the surface of the observer side of the light diffusing device according to claim 6 or 7,
The optical film is composed of a light-transmitting substrate and a condensing lens, and a plurality of condensing lenses are arranged at a constant pitch on the surface of the light-transmitting substrate on the observer side, and the shape of the condensing lens Is a convex curved surface. Between the optical film and the light diffusing device, there are provided a plurality of light masks and a light transmission opening for separating the light masks,
The optical sheet according to claim 8, wherein the light transmission openings are respectively arranged at positions corresponding to the tops of the condenser lenses.   The optical sheet according to claim 9, wherein the optical film and the light diffusing device are integrally laminated through the optical mask.   A dot-like or linear rib is arranged between the optical film and the light diffusing device, and the optical film and the light diffusing device are integrally laminated through the rib. Item 9. The optical sheet according to Item 8.   A backlight unit comprising the optical device according to claim 1, a light source, and an optical member that collects light that has passed through the optical device.   A backlight unit comprising the light diffusing device according to claim 6 and a light source.   A backlight unit comprising the optical sheet according to any one of claims 8 to 10 and a light source. The light source is a linear light source and the shape of the light deflection lens is a lenticular lens,
The angle formed by the major axis direction of the lenticular lens and the major axis direction of the linear light source when viewed in plan is 20 degrees or less. Backlight unit.   A display device comprising: an image display element that displays an image by transmitting or blocking light in pixel units; and the backlight unit according to claim 12.

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