JP2009163123A - Diffusion member, optical sheet, back light unit and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diffusion member which has no need of performing alignment in accordance with the position of a light source, improves the luminance in the front direction, reduces the dependency of light intensity on a viewing angle, and reduces a lamp image, and to provide an optical sheet, a back light unit and a display device. <P>SOLUTION: The diffusion member 25 for controlling the lighting optical path of a display comprises: a diffusion base material 26; and a light diffusion transmission layer 27. The diffusion base material 26 is composed in such a manner that a light diffusion region is dispersed into a transparent resin, and has a total luminous transmittance of 40 to 80% and a Haze value of ≥98%. The light diffusion transmission layer 27 comprises a base material 23 and unit lenses 28 for the light diffusion transmission layer, and in which the unit lenses 28 for the light diffusion transmission layer are arranged at the face 23a on the side opposite to an observer in the base material 23 at a fixed pitch. The base material 23 has a total luminous transmittance of ≥80% and a Haze value of ≤95%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

In recent large-sized liquid crystal televisions, direct type backlights in which a plurality of cold cathode tubes and LEDs (Light Emitting Diodes) are arranged are employed.
A resin plate (diffusion plate) having a strong light scattering property is used 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.
The diffusing plate diffuses light in all directions by the light diffusing effect, and thus darkens the liquid crystal display screen. Moreover, since the thickness of the diffusion plate usually requires a thickness of about 1 to 5 mm in order to enhance the light scattering property, the diffusion plate absorbs light not a little, and the liquid crystal display screen becomes dark.

  Further, since the liquid crystal television tends to be thinner year by year, the diffusion plate also tends to be thinner, and further improvement of the diffusion performance is demanded.

  Conventionally, a diffusion plate used in a direct type backlight is intended to diffuse light emitted from a cold cathode tube, which is a light source, and reduce luminance unevenness (lamp image). However, it is difficult to completely erase the lamp image.

If the number of diffusing particles is forcibly increased in order to completely eliminate the lamp image, the total light transmittance is lowered too much, causing a decrease in luminance.
Further, if the diffusion particles of the diffusion plate are reduced so as not to reduce the total light transmittance, the diffusion effect is also lowered.

Patent Documents 1 to 3 disclose examples in which a lens shape is formed on the exit surface of a diffusion plate as means for improving diffusion performance. For example, a lens sheet having a convex curved surface is disposed on the diffusion plate.
In such a diffusion plate, it is necessary to design the shape of the lens in accordance with the arrangement of the light sources and determine the alignment of the lens, and the manufacturing process may be complicated. Further, by shaping the lens shape on the exit surface of the diffuser plate, the total light transmittance of the diffuser plate may be lowered, and the liquid crystal display screen may be darkened. Furthermore, moire interference fringes may be generated from the lens sheet and the liquid crystal pixels arranged on the diffusion plate.

As a means for improving the brightness of the liquid crystal display screen, a brightness enhancement film (BEF), which is a registered trademark of 3M USA, is widely used as a lens sheet.
FIG. 7 is a schematic cross-sectional view showing an example of the arrangement of BEF, and FIG. 8 is a perspective view of the BEF. As shown in FIGS. 7 and 8, 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. The unit prism 187 has a size (pitch) larger than the wavelength of light.

  The BEF 185 collects light from “off-axis” and redirects this light “on-axis” or “recycle” toward the viewer. can do. That is, the BEF 185 can increase the on-axis luminance by reducing the off-axis luminance when the display is used (observation). Here, “on-axis” is a direction that coincides with the viewing direction F ′ of the viewer, and is generally the normal direction to the display screen (the viewing direction F ′ shown in FIG. 6).

However, when the BEF 185 is used, the light component due to the reflection / refraction action may be unnecessarily emitted in the lateral direction without proceeding to the viewer's visual field direction F ′.
FIG. 9 is a graph showing the relationship between the light intensity and the angle with respect to the viewing direction F ′. Line A is an ideal system light intensity curve, and line B is emitted from the optical sheet using BEF185. This is a light intensity curve of light.
As shown by the line B in FIG. 9, in the optical sheet using the BEF185, the light intensity is maximized when the viewer's viewing direction F ′, that is, the angle with respect to the viewing direction F ′ is 0 ° (corresponding to the axial direction). However, a small light intensity peak (side lobe) occurs in the vicinity of ± 90 ° with respect to the viewing direction F ′, and the amount of light emitted from the lateral direction is increased.
On the other hand, the line A in FIG. 9 does not show side lobes, and the light intensity in the viewing direction F ′ is also improved over the line B.

  When a lens sheet represented by BEF185 is used, a diffusion filler is applied on a transparent substrate, and a diffusion film having a function of both diffusion and condensing (hereinafter referred to as a lower diffusion film) is formed between the diffusion plate and the lens sheet. By disposing in between, the diffused light emitted from the diffuser plate can be collected efficiently, and the visibility of the light source that cannot be erased by the diffuser plate alone can be suppressed.

Furthermore, when a light diffusing film is disposed between the lens sheet and the liquid crystal panel, side lobes can be reduced and moire interference fringes generated between the regularly arranged lenses and the liquid crystal pixels. Can be prevented.
However, the method using the lower diffusing film and the light diffusing film increases the number of members, which complicates the work for assembling the display, and causes problems such as contamination between optical sheets.

  In Patent Document 4, as a means for solving such a problem, an optical film composed only of the unit prism is not used, but an array structure in which unit lenses are arranged at a constant pitch in a two-dimensional direction. A backlight unit using an optical film is disclosed.

However, in the backlight unit using such an optical film, it is necessary to align the position of the light source and the position of the lens, which causes a problem that the manufacturing process becomes complicated. Furthermore, since it is necessary to flatten the exit surface of the diffuser plate in order to laminate the optical film integrally, it becomes impossible to shape the lens on the exit surface of the diffuser plate to increase the light collecting property, and the viewing direction F ′ It is no longer possible to take measures to improve the image visibility by improving the brightness of the image.
JP 2007-103321 A JP 2007-12517 A JP 2006-195276 A JP 2007-213035 A

  In view of the above problems, the present invention eliminates the need for alignment according to the position of the light source, improves the diffusion / condensability, and improves the luminance in the front direction (observer side). An object of the present invention is to provide a diffusion member, an optical sheet, a backlight unit, and a display device that reduce the dependency of the intensity on the viewing angle and reduce the lamp image.

In order to achieve the above object, the present invention employs the following configuration. That is,
The diffusing member of the present invention is a diffusing member for controlling an illumination optical path of a display, and the diffusing member includes a diffusing base material and a light diffusing and transmitting layer, and is disposed on a surface opposite to the observer of the diffusing base material. The light diffusion / transmission layer is formed by superimposing the observer side surface, and the diffusion base material has a light diffusion region dispersed in a transparent resin, and has a total light transmittance of 40% to 80%, haze. The value is 98% or more, and the light diffusing and transmitting layer is composed of a base material and a unit lens for the light diffusing and transmitting layer, and a plurality of units for the light diffusing and transmitting layer are provided on a surface opposite to the observer of the base material. The lenses are arranged at a constant pitch, and the substrate has a total light transmittance of 80% or more and a haze value of 95% or less.

  In the diffusing member of the present invention, the light diffusing / transmitting layer unit lens has a convex curved surface shape or a triangular prism shape, a first apex portion having an arcuate surface or a ridgeline, and a first apex portion extending from the first apex portion to the base material. And a distance between the first inclined surfaces facing each other gradually decreases toward the first top.

  In the diffusing member of the present invention, the refractive index of the light diffusing / transmitting layer is n, the pitch of the unit lens for the light diffusing / transmitting layer is P, and the first inclined surface is bonded to the substrate when viewed in cross section. When the angle between the tangent line from the joining point to the first inclined surface and the surface of the substrate opposite to the viewer is θ, the thickness T of the substrate satisfies the following formula (1) It is characterized by that.

  The diffusion member of the present invention is characterized in that the light diffusion region is a light diffusion particle, and the thickness of the diffusion base is 0.1 to 5 mm.

  The diffusion member of the present invention is characterized in that the transparent resin is a thermoplastic resin, the light diffusion region includes bubbles, and the thickness of the diffusion base material is 25 to 500 μm.

  The diffusion member of the present invention is characterized in that the diffusion base material is stretched in at least one axial direction.

  The diffusing member of the present invention is characterized in that the light diffusing and transmitting layer does not contain light diffusing particles.

  In the diffusing member of the present invention, the light diffusing and transmitting layer is made of a thermoplastic resin.

  The diffusing member of the present invention is characterized in that the base material of the light diffusing and transmitting layer is stretched in at least one axial direction.

  The diffusion member of the present invention is characterized in that the diffusion base material and the light diffusion / transmission layer are integrally formed by a multilayer extrusion method.

  The diffusion member of the present invention is characterized in that the diffusion base material and the light diffusion / transmission layer base material are integrally formed by a multilayer extrusion method.

  The diffusion member of the present invention is characterized by being stretched in at least one axial direction.

  The diffusing member of the present invention is characterized in that the diffusing base material and the light diffusing and transmitting layer are laminated with an adhesive or an adhesive.

  The diffusing member of the present invention is characterized in that the diffusing base material and the base material of the light diffusing and transmitting layer are laminated with an adhesive or an adhesive.

  The optical sheet of the present invention is an optical sheet for controlling an illumination optical path of a display, and the optical sheet is composed of the diffusion member and the optical film described above, and the optical member is formed on the observer side surface of the diffusion member. The surface opposite to the viewer of the film is formed by being overlapped, and the optical film is composed of a light-transmitting substrate and a unit lens for the light-transmitting substrate, and the surface of the light-transmitting substrate on the viewer side A plurality of unit lenses for the light-transmitting substrate are arranged at a constant pitch, the shape of the unit lenses for the light-transmitting substrate is a convex curved surface, the second top portion having an arcuate surface, and the second A second inclined surface that extends from the top to the light-transmitting substrate, and is formed such that the distance between the opposing second inclined surfaces gradually decreases as the second top is reached. It is characterized by.

  In the optical sheet of the present invention, a plurality of light masks and a light transmission opening for separating the light mask are provided between the optical film and the diffusion member, and the light transmission opening is It is provided corresponding to the second apex portion of the unit lens for a light transmissive substrate.

  In the optical sheet of the present invention, dot-shaped or linear ribs are arranged between the optical film and the diffusing member, and the optical film and the diffusing member are integrally laminated via the rib. Features.

  The optical sheet of the present invention is characterized in that the viewer-side surface of the diffusion substrate is a substantially flat surface.

  The optical sheet of the present invention is characterized in that a plurality of unit lenses for a diffusion base material are arranged at a constant pitch on the surface of the diffusion base material on the viewer side.

  The backlight unit of the present invention includes the optical sheet described above and a light source.

  In the backlight unit of the present invention, the light source is a linear light source, and the shape of the light diffusion / transmission layer unit lens is a lenticular type, and when viewed in plan, the major axis direction of the lenticular lens and the line The angle formed by the major axis direction of the light source is 20 degrees or less.

  A display device according to the present invention includes an image display element that transmits and blocks light in pixel units and displays an image, and the backlight unit described above.

  The display device of the present invention is characterized in that the image display element is a liquid crystal display element.

  According to the above configuration, it is not necessary to perform alignment according to the position of the light source, it is possible to improve the diffusion / condensability, improve the brightness in the front direction (observer side), and the viewing angle of the light intensity It is possible to provide a diffusion member, an optical sheet, a backlight unit, and a display device that reduce the dependency and reduce the lamp image.

Hereinafter, modes for carrying out the present invention will be described.
(Embodiment 1)
FIG. 1 is a schematic cross-sectional view illustrating an example of an optical sheet, a backlight unit, and a display device according to an embodiment of the present invention.
The display device 70 according to the embodiment of the present invention is generally configured by an image display element 35 and a backlight unit 55. Further, the backlight unit 55 according to the embodiment of the present invention includes an optical sheet 52 and a backlight unit 45. Furthermore, the optical sheet 52 according to the embodiment of the present invention is schematically configured from the optical film 1 and the diffusion member 25.

  The optical sheet 52 is formed by superimposing a surface 17 a opposite to the observer of the optical film 1 on the observer-side surface 26 b of the diffusing member 25 via the optical mask 22. The optical sheet 52 is an optical sheet for controlling the illumination optical path of the display, and controls the optical path of light from the backlight for use as illumination light of the display device.

(Diffusion member)
The diffusing member 25 according to the embodiment of the present invention includes a diffusing base material 26 and a light diffusing / transmitting layer 27, and the surface 26 a opposite to the observer of the diffusing base material 26 on the viewer side of the light diffusing / transmitting layer 27. The surface 23b is formed to overlap.

(Light diffusion transmission layer)
The light diffusion / transmission layer 27 includes a base material 23 and a light diffusion / transmission layer unit lens 28, and a plurality of light diffusion / transmission layer unit lenses 28 have a constant pitch on a surface 23 a opposite to the observer of the base material 23. Are arranged in
A surface 23 b on the viewer side of the base material 23 is joined to a surface 26 a on the opposite side of the viewer of the diffusion base material 26.

  The base material 23 preferably has a total light transmittance of 80% or more. If the total light transmittance is 80% or more, the luminance of light emitted in the front direction (observer side) F is not lowered. On the contrary, when the total light transmittance is less than 80%, the luminance of the light emitted in the front direction (observer side) F is lowered, which is not preferable. The total light transmittance is a measured value based on JIS K7361-1.

  The base material 23 preferably has a haze value of 95% or less. When the haze value exceeds 95%, it is preferable because a sufficient light diffusion effect cannot be obtained even if the light diffusion / transmission layer unit lens 28 is formed on the surface 23a opposite to the observer of the substrate 23. Absent. The haze value is a measured value based on JIS K7136.

  The material used for the light diffusing and transmitting layer 27 is preferably a transparent resin made of a thermoplastic resin. For example, polycarbonate resin, acrylic resin, fluorine acrylic resin, silicone acrylic resin, epoxy acrylate resin, polystyrene resin, cycloolefin polymer , Methylstyrene resin, fluorene resin, PET, polypropylene and the like. The light diffusing and transmitting layer 27 may be extended in at least one axial direction.

  More preferably, the light diffusing and transmitting layer 27 does not contain light diffusing particles. This is because when the light diffusion / transmission layer 27 contains light diffusion particles, the light diffusion effect by the light diffusion / transmission layer unit lens 28 is weakened.

(Diffusion base material)
An observer-side surface 26b of the diffusion base material 26 is a substantially flat surface. Therefore, the optical film 1 can be laminated and integrated. Even if the surface 26b on the viewer side is provided with irregularities, the effect cannot be obtained if the layers are integrated.

  The diffusion base material 26 preferably has a total light transmittance of 40% to 80%. If the total light transmittance is less than 40%, it is not preferable because the luminance of the emitted light in the front direction (observer side) F is lowered. Conversely, if the total light transmittance exceeds 80%, This is not preferable because the diffusion performance becomes insufficient and the uniformity of in-plane luminance deteriorates.

  The diffusion base material 26 preferably has a haze value of 98% or more. When the haze value is less than 98%, the diffusion performance becomes insufficient and the uniformity of in-plane luminance is deteriorated, which is not preferable.

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 , Methylstyrene resin, fluorene resin, polyethylene terephthalate (PET), polypropylene, 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 (tetra Fluoropolymer particles such as fluoroethylene-hexafluoropropylene copolymer), PVDF (polyfluorovinylidene), and ETFE (ethylene-tetrafluoroethylene copolymer); silicone resin particles can be used.
Moreover, you may use combining 2 or more types of transparent particles from the transparent particle described previously. Furthermore, the size and shape of the transparent particles are not particularly defined.

When the light diffusion particle is used as the light diffusion region, the thickness of the diffusion base material 26 is preferably 0.1 to 5 mm.
When the thickness of the diffusion substrate 26 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, 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 a resin incompatible with PET, fillers such as titanium oxide (TiO ₂ ), and barium sulfate (BaSO ₄ ) in PET, and then stretching the PET by a biaxial stretching method. And forming bubbles around the filler.

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

  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, and spiroglycol 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 Or the like can be used a mixture of these resins are not particularly limited.

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. In addition, when the thickness of the diffusion base material 26 exceeds 500 μm, there is no particular problem in optical performance, but the rigidity is increased, so that it is difficult to process into a roll shape, and slits cannot be easily formed. This is not preferable because the merit of thinness obtained is reduced.

The diffusing member 25 is preferably formed by integrally forming the diffusing base material 26 and the light diffusing and transmitting layer 27 by a multilayer extrusion method. At this time, the light diffusion / transmission layer 27 is formed by extruding the light diffusion / transmission layer unit lens 28 together, whereby the manufacturing process can be further simplified. Moreover, the diffusing member 25 may be extended in at least one axial direction.
By using the multilayer extrusion method, the manufacturing process can be simplified and made more efficient, and the manufacturing cost can be reduced.

The diffusion member 25 may be formed by integrating the diffusion base material 26 and the light diffusion / transmission layer 27 separately by an extrusion method, injection molding, or the like, and then integrating them with an adhesive or an adhesive material.
For example, as the adhesive or adhesive material, the diffusion base material 26 and the light diffusion / transmission layer 27 can be bonded using a generally used laminate or the like.

The unit lens 28 for the light diffusing and transmitting layer can be formed on the surface 23a of the base 23 opposite to the observer using a radiation curable resin such as a UV curable resin. After forming the material 23 as a plate-like member, the light diffusion / transmission layer unit lens 28 can be formed by UV molding on the surface 23a of the base 23 opposite to the observer. Alternatively, after the base material 23 is formed as a plate-like member by an extrusion method and integrated with the diffusion base material 26, the light diffusion / transmission layer unit lens 28 is formed on the surface 23 a opposite to the observer of the base material 23. Can be UV molded.
Light diffusion by injection molding or hot press molding using PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), COP (cycloolefin polymer), acrylonitrile styrene copolymer, etc. The transmission layer unit lens 28 can also be formed.

FIG. 2 is a schematic cross-sectional view illustrating a light path in the diffusing member 25.
The diffusion member 25 is formed by overlapping a diffusion base material 26 and a light diffusion / transmission layer 27. The light diffusion / transmission layer 27 includes a base material 23 and light diffusion / transmission layer unit lenses 28 arranged on the surface 23a of the base material 23 opposite to the observer at a constant pitch. Further, a surface 26 a opposite to the observer of the diffusion base material 26 is joined to the surface 23 b of the base material 23 on the viewer side.

A backlight (light source) 41 (not shown) is provided on the surface 23 a side opposite to the observer of the base material 23, and light H from the backlight (light source) 41 (not shown) enters the diffusion member 25. It is supposed to be configured.
Therefore, the surface 23a opposite to the observer of the base material 23 and the surface 26a opposite to the observer of the diffusion base material 26 are incident surfaces of the respective members, and the surface 23b of the base material 23 on the observer side is diffused. The surface 26b on the observer side of the base material 26 is an emission surface of each member.

  The shape of the light diffusion / transmission layer unit lens 28 is preferably a convex curved surface shape or a triangular prism shape. With this shape, the light diffusibility can be improved and the lamp image can be reduced. For example, a lens array formed in a one-dimensional or two-dimensional arrangement can be used, and examples thereof include a prism lens array, a microlens array, a cylindrical lens array, or a lens array formed by combining these.

The light diffusion / transmission layer unit lens 28 is formed in a convex curved shape when viewed in cross-section, and has a first apex portion 28a having an arcuate surface and a first inclined surface 28b extending from the first apex portion 28a to the base material 23. And a substantially flat surface 28c. The light diffusing / transmitting layer unit lens 28 is formed so that the distance between the first inclined surfaces 28b facing each other gradually decreases toward the first apex portion 28a.
The first inclined surface 28 b is bonded to the base material 23 at the bonding point 30. The light diffusion / transmission layer unit lenses 28 are arranged at a pitch P, and are joined to the adjacent light diffusion / transmission layer unit lenses 28 at junction points 30 respectively.
When the angle (hereinafter referred to as the contact angle) formed by the tangent line 1 from the junction point 30 to the surface of the unit lens 28 for the light diffusing / transmitting layer and the one surface 23a of the substrate 23 is θ, the thickness T of the substrate 23 is as follows. It is preferable to satisfy the formula (2).

When the relationship of the above formula (2) is satisfied, as shown in FIG. 2, the light from the light source is incident on the light diffusion / transmission layer unit lens 28 as indicated by an arrow H, and the convex curved surface has an arrow. After being refracted like L and condensed once inside the light diffusing / transmitting layer 27, the diffused light by the adjacent unit lens 28 for the light diffusing / transmitting layer is diffused to the overlapping range, and the observer of the base material 23 The light is emitted to the side surface 23b. Thereafter, the light is incident on the inside of the diffusion base material 26 from the surface (incident surface) 26a opposite to the observer of the diffusion base material 26 and further diffused inside the diffusion base material 26, and then the viewer of the diffusion base material 26 is observed. The light is emitted in the front direction (observer side) F from the side surface (outgoing surface) 26b.
By diffusing such light, the lamp image can be reduced, and outgoing light with reduced viewing angle dependency of light intensity can be obtained. Note that the reduction of the lamp image is to scatter the light from the linear light source 41 to eliminate unevenness in brightness and to prevent the light source 41 from being seen through.
Furthermore, since the total light transmittance of the entire diffusing member 25 is reduced only on the order of several percent, the surface (exiting surface) 26b on the observer side of the diffusing base material 26 is directed in the front direction (observer side) F. The brightness of the emitted light is hardly reduced.
In addition, it is not necessary to align the position of the backlight (light source) 41 and the position of the diffusing member 25, so that the manufacturing efficiency can be improved and the manufacturing cost can be reduced.

  On the other hand, when the relationship of the above formula (2) is not satisfied, the surface on the viewer side of the base material 23 is condensed once within the light diffusing / transmitting layer 27 and diffused in an optimum range. 23b is not preferable because the effect of reducing the lamp image becomes insufficient and luminance unevenness due to the lamp image of the backlight (light source) 41 may be visually recognized. Furthermore, the case where the viewing angle dependency of the light intensity cannot be sufficiently reduced occurs, which is not preferable.

The length of the pitch P of the unit lenses 28 for the light diffusing and transmitting layer is not particularly limited and can be designed freely.
However, when the pitch P of the light diffusion / transmission layer unit lenses 28 is too large, the thickness T of the base material 23 must be increased in order to satisfy the relationship of the above formula (2). In consideration of production efficiency, production cost, etc., it is not preferable that the thickness T of the base material 23 is thick. In practice, the pitch P is preferably 0.5 mm or less, more preferably 0.2 mm or less. preferable.

It should be noted that another layer may be laminated on the viewer-side surface 26 b of the diffusion base material 26 that constitutes the diffusion member 25.
FIG. 3 is a cross-sectional view showing an example of a diffusing member in which other layers are laminated. FIG. 3A is a diagram in the case where a protective film 37 is laminated, and FIG. FIG. 3C is a diagram in the case where the protective unit lens 19 and the diffusion base unit lens 19 are laminated.
By disposing the unit lens 19 for the diffusing substrate, the total light transmittance is lowered, but the diffusibility can be improved, and the amount of light diffusing particles added to the diffusing substrate 26 can be reduced. Furthermore, the high condensing effect by the lens array shape to form can be acquired.
Examples of the diffusion base unit lens 19 include a prism lens array, a microlens array, a cylindrical lens array, or a lens array formed by combining these.
Further, the same diffusion effect can be obtained by arranging the protective film 37. The protective film 37 may be formed by applying a thermoplastic resin to the produced diffusion member 25, or may be integrally formed when the diffusion member 25 is produced by extrusion or stretching.
Further, the diffusion base unit lens 19 may be disposed on the protective film 37. Further diffusion performance can be obtained.

(Optical sheet)
As shown in FIG. 1, the optical sheet 52 is formed by overlapping the optical film 1 and the diffusion member 25.
(Optical film)
The optical film is composed of a light-transmitting substrate 17 and a light-transmitting substrate unit lens 16, and a plurality of light-transmitting substrate unit lenses 16 are fixed on the surface 17b of the light-transmitting substrate 17 on the observer side. Arranged at pitch.

  By forming the light transmission substrate unit lens 16 on the surface 17b of the light transmission substrate 17 on the observer side, the light passing through the diffusion member 25 is condensed in the front direction (observer side) F. The brightness in the front direction (observer side) F can be improved.

The surface 17a opposite to the observer of the light transmissive substrate 17 is a substantially flat surface, a plurality of light masks 22 are formed, and a diffusion member 25 is further bonded.
As the 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 diffusion member 25 may be used. Generation | occurrence | production of curvature can be suppressed by joining the material used for the diffusion member 25. FIG.

  In addition, when unit lenses are formed on one surface and the other surface of one member, moire interference fringes may occur, and the optical sheet 52 is a surface (outgoing surface) on the observer side of the light transmitting substrate 17. The light transmission base unit lens 16 is formed on 17b, and the light diffusion / transmission layer unit lens 28 is formed on the surface (incident surface) 23a opposite to the observer of the base film 23. Since the diffusion base material 26 is inserted between the base film 23 and the base film 23, moire interference fringes caused by the factors described above can be prevented.

  The shape of the light transmitting base unit lens 16 is a convex curved surface, and has a second apex portion 16a having an arcuate surface and a second inclined surface 16b extending from the second apex portion 16a to the light transmitting base material. Moreover, the unit lens 16 for light transmissive base materials is formed so that the distance between the opposing second inclined surfaces 16b gradually decreases toward the second top portion 16a. Furthermore, the light transmission base unit lenses 16 are spaced apart by the valleys 13 and formed at a constant pitch.

Between the optical film 1 and the diffusing member 25, a plurality of light masks 22 and light transmission openings 15 that separate the light masks 22 are provided. The pitch of the light mask 22 and the light transmission openings 15 is substantially the same as the pitch of the light transmission base unit lenses 16.
The position of the optical mask 22 is formed at a position corresponding to the position of the valley portion 13. Therefore, the position of the light transmission opening 15 is provided at a position corresponding to the second apex portion 16 a of the light transmission substrate unit lens 16.

  The optical mask 22 is made of a material that does not transmit light, and is formed at a position corresponding to the position of the valley portion 13 that separates the light transmitting base unit lens 16 formed on the surface 17b on the viewer side. Therefore, the light incident on the optical film 1 passes through the light transmitting opening 15 formed away from the optical mask 22 and enters the light transmitting base unit lens 16, and thus passes through the diffusion member 25. The emitted light is efficiently emitted in the front direction (observer side) F.

  Furthermore, 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 to the diffusing substrate 26 constituting the diffusing member 25, is again diffused by the diffusing substrate 26, and then is emitted in the front direction (observer side) F. Is done. By repeating this process, almost all the light from the backlight (light source) 41 can be emitted in the front direction (observer side) F.

  The optical sheet 52 can be formed by bonding the diffusing member 25 to the four sides of the surface 17a opposite to the observer of the optical film 1 on which the optical mask 22 is formed as described above, with a double-sided tape. For example, the thickness of the diffusion member 25 is 2 mm, and the width of the double-sided tape is 5 mm.

  The diffusion member 25 according to the embodiment of the present invention has a total light transmittance of 40% to 80%, a diffusion base material 26 having a haze value of 98% or more, a total light transmittance of 80% or more, and a haze value of 95%. Since it is composed of the light diffusion / transmission layer 27 described below, it is possible to improve the light collection / diffusion characteristics and reduce the lamp image.

  The diffusing member 25 according to the embodiment of the present invention has a light diffusing / transmitting layer 27 including a base material 23 in which a plurality of unit lenses 28 for light diffusing / transmitting layers are arranged at a constant pitch. The characteristics can be improved and the lamp image can be reduced.

  In the diffusing member 25 according to the embodiment of the present invention, the pitch of the light diffusion / transmission layer unit lenses 28 is P, the refractive index of the light diffusion / transmission layer 27 is n, and the first inclined surface 28b is formed on the base material 23. When the angle (tangential angle) formed by the tangent line 1 from the junction point 30 to be joined to the surface 28a of the light diffusion / transmission layer unit lens 28 is θ, the thickness T of the base material 23 satisfies the above formula (2). With this configuration, it is possible to improve the light collection and diffusion characteristics and reduce the lamp image.

  In the diffusing member 25 according to the embodiment of the present invention, the shape of the unit lens 28 for the light diffusing / transmitting layer is a convex curved surface, and the first apex portion 28a having an arcuate surface and One inclined surface 28b, and the distance between the opposed first inclined surfaces 28b gradually decreases toward the first top 28a. The light incident from the convex curved surface can be diffused to the range where the diffused light by the light diffusion / transmission layer unit lens 28 adjacent to the surface 23b on the viewer side of the substrate 23 overlaps and emitted. As a result, the light collection / diffusion characteristics can be improved and the lamp image can be reduced.

  In the diffusing member 25 according to the embodiment of the present invention, a light diffusing and transmitting layer 27 is bonded to a surface 26a opposite to the observer of the diffusion base material 26, and the surface 26b on the observer side is used as an emitting surface. Can be integrated with the optical film 1.

  Since the diffusing member 25 according to the embodiment of the present invention has a configuration in which the diffusing substrate 26 is formed by dispersing light diffusing particles in a transparent resin, desired diffusing performance can be easily obtained.

  The diffusion member 25 according to the embodiment of the present invention has a configuration in which the diffusion base material 26 is formed by dispersing bubbles in a thermoplastic resin. Therefore, the internal surface of the bubbles formed inside the thermoplastic resin causes irregular reflection of light. It is possible to develop a light diffusing function equivalent to or higher than that when the light diffusing particles are dispersed. Therefore, the film thickness of the diffusion base material 26 can be made thinner.

In the diffusion member 25 according to the embodiment of the present invention, a resin that is not compatible with the thermoplastic resin, a filler such as titanium oxide (TiO ₂ ), or barium sulfate (BaSO ₄ ) is dispersed in the thermoplastic resin. After that, since the structure has the diffusion base material 26 that is stretched in at least one axial direction, it can be formed by generating bubbles around the filler. Therefore, 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 the light diffusing particles are dispersed can be exhibited.

  The diffusion member 25 according to the embodiment of the present invention has a configuration in which the diffusion base material 26 and the light diffusion / transmission layer 27 are integrally formed by a multilayer extrusion method. Therefore, the diffusion member 25 can be easily manufactured, and the manufacturing process is simplified. The manufacturing cost can be reduced.

  The diffusing member 25 according to the embodiment of the present invention has a configuration in which the diffusing base material 26 and the light diffusing and transmitting layer 27 are laminated by an adhesive or an adhesive material. Therefore, the diffusing member 25 can be easily manufactured and simplifies the manufacturing process. At the same time, the manufacturing cost can be reduced.

  In the diffusing member 25 according to the embodiment of the present invention, since the light diffusing and transmitting layer 27 does not include diffusing particles, the diffusion effect of the light diffusing and transmitting layer unit lens 28 is not reduced.

  The optical sheet 52 according to the embodiment of the present invention has a plurality of optical masks 22 and light transmission openings 15 that separate the optical masks 22 between the optical film 1 and the diffusing member 25. The light mask 22 is formed so as to correspond to the second top portions 16a of the plurality of light transmission substrate unit lenses 16 arranged on the observer-side surface 17b of the light transmission substrate 17 constituting the The light to be transmitted can be almost only the light emitted in the direction of the second apex portion 16a of the unit lens 16 for the light transmitting base material, and the luminance in the front direction (observer side) F can be improved.

  Since the optical sheet 52 according to the embodiment of the present invention uses a light reflective member as the light mask 22, the light that is not transmitted by the light mask 22 is returned to the diffusion base material 26 and is diffused again by the diffusion base material 26. After that, the step of emitting light in the front direction (observer side) F can be repeated, and almost all light from the backlight (light source) 41 can be emitted in the front direction (observer side) F.

(Backlight unit)
As shown in FIG. 1, a backlight unit 55 according to an embodiment of the present invention is a direct type backlight unit, and is schematically composed of an optical sheet 52 and a backlight unit 45. The backlight unit 45 includes a plurality of backlights (light sources) 41 and a reflecting plate 43.

As the backlight (light source) 41, for example, a plurality of cylindrical light sources can be used. As the plurality of cylindrical light sources, for example, a plurality of linear fluorescent lamps, cold cathode fluorescent lamps (CCFLs), LEDs, or the like can be used.
The reflection plate 43 is disposed on the opposite side of the front direction (observer side) F of the plurality of backlights (light sources) 41, and the front direction (observation) of the light emitted from the backlights (light sources) 41 in all directions. The light emitted in the direction opposite to the viewer side F can be reflected and emitted in the front direction (observer side) F. As a result, the light H emitted in the front direction (observer side) F becomes light emitted in almost all directions from the backlight (light source) 41. By using the reflection plate 43 in this way, the light utilization efficiency can be increased. The reflection plate 43 may be any member that reflects light with high efficiency. For example, a general reflection film, a reflection plate, or the like can be used.

  By arranging the optical sheet 52 in the front direction (observer side) F of the plurality of backlights (light sources) 41, the light H from the backlights (light sources) 41 can be almost taken in. The light H is incident on the optical sheet 52 and is set as outgoing light K. The emitted light K is eliminated from the lamp image of the backlight (light source) 41 due to the diffusion effect of the optical sheet 52, the viewing angle dependency of the light intensity is reduced, and further, due to the light collection effect of the optical sheet 52, The brightness in the front direction (observer side) F is improved and emitted.

  4 is a schematic plan view when the backlight (light source) 41 and the light diffusion / transmission layer unit lens 28 are viewed, as indicated by an arrow X in FIG. The backlight (light source) 41 is a linear light source, and the light diffusion / transmission layer unit lens 28 is formed of a lenticular lens. Further, the axial direction m of the light diffusion / transmission layer unit lens 28 is arranged slightly inclined with respect to the axial direction n of the backlight (light source) 41.

The angle θ ₄₁ formed by the axial direction m of the light diffusion / transmission layer unit lens 28 and the axial direction n of the backlight (light source) 41 is preferably 20 degrees or less.
When the angle θ ₄₁ is 20 degrees or less, the lamp image of the backlight (light source) 41 can be eliminated. Conversely, when the angle θ ₄₁ exceeds 20 degrees, the effect of reducing the lamp image of the backlight (light source) 41 becomes insufficient, and the lamp image of the backlight (light source) 41 can be seen on the liquid crystal display screen. A case occurs.

  Since the backlight unit 55 according to the embodiment of the present invention includes the optical sheet 52 described above, the light K from the light source 41 is incident on the optical sheet 52, and the light K is condensed and diffused. It is possible to improve the brightness in the front direction (observer side) F, smooth the visual direction distribution of the light intensity, and reduce the lamp image.

  The backlight unit 55 according to the embodiment of the present invention is a plan view when the light source 41 is a linear light source and the shape of the 28 unit lens for the light diffusion / transmission layer of the light diffusion / transmission layer 27 is a lenticular type. In addition, since the angle formed by the axial direction m of the lenticular lens and the axial direction n of the linear light source 41 is 20 degrees or less, the lamp image can be reduced.

(Display device)
As shown in FIG. 1, a display device 70 according to an embodiment of the present invention includes an image display element 35 and a backlight unit 50.
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 through the polarizing filter 33 and is emitted in the front direction (observer side) F through the polarizing filter 31.

The image display element 35 is preferably an element that displays an image by transmitting / blocking light in pixel units. If the image is displayed by transmitting / blocking light in pixel units, the optical sheet 52 improves the brightness in the front direction (observer side) F, and the viewing angle dependency of the light intensity is reduced. Furthermore, it is possible to display an image with high image quality by effectively using light with a reduced lamp image.
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 which is embodiment of this invention. By doing so, the image quality can be further improved.

  Since the display device 70 according to the embodiment of the present invention is configured to use the light K whose light collection / diffusion characteristics are improved by the optical sheet 52 described above, the luminance in the front direction (observer side) F is improved. It is possible to display on the image display element 35 an image in which the distribution of the light intensity in the visual direction is smoothed and the lamp image is reduced.

  A display device 70 according to an embodiment of the present invention is an image display element 35 that defines a display image according to transmission / light-shielding in pixel units, and improves the light collection and diffusion characteristics by the backlight unit 55 described above. Therefore, the luminance in the front direction (observer side) F can be improved, the visual direction distribution of the light intensity can be smoothed, and an image with a reduced lamp image can be obtained.

  In the display device 70 according to the embodiment of the present invention, the image display element 35 is a liquid crystal display element and uses the light K whose light collection / diffusion characteristics are improved by the backlight unit 55 described above. The luminance of the direction (observer side) F can be improved, the visual direction distribution of light intensity can be smoothed, and an image with a reduced lamp image can be obtained.

(Embodiment 2)
FIG. 5 is a schematic cross-sectional view illustrating another example of the optical sheet, the backlight unit, and the display device according to the embodiment of the present invention. The same members as those in the first embodiment are denoted by the same reference numerals.

The configuration different from the first embodiment is that the V-shaped groove 4 is first formed in the second apex portion 18a of the light transmitting base unit lens 18. Next, the optical film 11 and the diffusing member 25 are joined via the rib 29, and the gap portion 14 is provided between the optical film 11 and the diffusing member 25. Furthermore, the diffusion base unit lens 19 is formed on the viewer-side surface 26 b of the diffusion base 26 exposed inside the gap portion 14.
Except for the above three points, the display device 72 according to the embodiment of the present invention is formed with substantially the same configuration as that of the first embodiment. That is, the display device 72 includes the image display element 35 and the backlight unit 56. Further, the backlight unit 56 according to the embodiment of the present invention includes an optical sheet 53 and a backlight unit 45. The backlight unit 45 includes a backlight (light source) 41 and a reflection plate 43. The optical sheet 53 according to the embodiment of the present invention includes the optical film 11 and the diffusing member 25.

  The light H incident on the optical sheet 53 from the backlight (light source) 41 is diffused and condensed inside the optical sheet 53, and is directed from the light transmitting base unit unit lens 18 of the optical film 11 in the front direction (observer side). F is emitted to F as outgoing light K.

<Unit lens 18 for light transmissive substrate>
FIG. 6 is a perspective view of the optical film 11. As shown in FIG. 6, the plurality of unit lenses 18 for a light transmissive substrate are formed on an observer-side surface (light exit surface) 17 b of the light transmissive substrate 17, extend in the X direction, and extend in the Y direction. Are arranged at regular intervals (pitch).
The shape of the unit lens 18 for the light transmissive substrate is a convex curved surface shape, a flat surface 18c facing the observer side surface (emission surface) 17b of the light transmissive substrate 17, and a second apex portion 18a having an arcuate surface. And the second inclined surface 18b from the second top portion 18a to the light transmitting base material 17, and the distance between the opposed second inclined surfaces 18b gradually decreases as going to the second top portion 18a. Is formed. Further, a V-shaped groove 4 extending in the X direction is formed on the top portion 18a of the unit lens 18 for a light transmitting base material.

As described above, when the V-shaped groove 4 is provided in the second apex portion 18a of the light transmitting base unit lens 18, light is recycled by total reflection of light generated at the side surface of the V-shaped groove 4 and the air layer interface. As a result, it is possible to obtain a higher brightness increasing effect than the conventional lens sheet.
Further, when a general prism sheet is used as the brightness enhancement film, there is a possibility that side lobes may be generated in the light intensity spectrum. However, the V-shaped groove 4 is formed on the second apex portion 18a of the unit lens 18 for a light transmitting substrate. Is provided on both sides of the V-shaped groove 4 are the second inclined surfaces 18b, the side lobes of the light intensity spectrum can be suppressed to a minimum, and the brightness is rapidly reduced with respect to the field of view ( (Cut-off) can be reduced.
In addition, it is not limited to the said shape of the unit lens 18 for light transmissive base materials, For example, a convex lenticular shape, a micro lens shape, a prism shape etc. are mentioned.

<Unit lens 19 for diffusion base>
By forming the unit lens 19 for the diffusing substrate, the diffusibility of the light emitted from the diffusing member 25 can be further improved and incident on the optical film 11.

  By using the optical sheet 53 with improved diffusion characteristics as described above, the light K emitted from the optical sheet 56 can be converted to light having an optical gain of 1 or more. Here, the optical gain is one of indexes indicating the diffusibility of the optical diffusing member, and is expressed as a ratio to the luminance of the light, assuming that the luminance of the diffuser that completely diffuses is 1. When the diffusivity of the diffusing member to be measured is biased depending on the direction, the diffusion characteristic of the diffusing member can be shown by obtaining the optical gain for each direction. Also, complete diffusion refers to an ideal diffuser that has zero absorption and a constant intensity in any direction. That is, an optical gain of 1 or more indicates that there is an effect of collecting light in the measurement direction, and that the larger the value, the stronger the light collection effect.

<Fixing element (rib) 29>
As shown in FIG. 5, fixing elements (ribs) 29 are arranged around the observer-side surface 25b of the diffusing member 25 on which the diffusing substrate unit lens 19 is formed as described above, and the diffusing member 25 is attached. Are combined. In this way, the optical sheet 53 can be formed.
Further, by joining the optical film 11 and the diffusing member 25 via a fixing element (rib) 29, the gap portion 14 can be secured between the optical film 11 and the diffusing member 25, and the inside of the gap portion 14. The diffusion base unit lenses 19 arranged at a constant pitch can be held on the viewer-side surface 26b of the diffusion base 26 exposed in step S2. The shape of the fixing element (rib) 29 may be a dot shape or a linear shape.
Furthermore, the brightness increasing effect can be enhanced by aligning the valleys of the light transmission substrate unit lens 18 with the fixing element (rib) 29.

  The optical sheet 53 according to the embodiment of the present invention includes a plurality of diffusion base unit lenses 19 arranged at a constant pitch on the viewer-side surface 26b of the diffusion base 26 exposed inside the gap portion 14. With this configuration, light can be efficiently emitted from the surface 26b on the observer side, diffusion characteristics can be improved, and a lamp image can be reduced.

  Since the optical sheet 53 according to the embodiment of the present invention is configured to dispose the dot-like or linear rib 29 between the optical film 11 and the diffusing member 25, the optical sheet 53 can be easily manufactured. While simplifying a manufacturing process, manufacturing cost can be reduced.

  Since the backlight unit 56 according to the embodiment of the present invention includes the optical sheet 53 described above, it improves the light collection / diffusion characteristics, improves the luminance in the front direction (observer side) F, and increases the light intensity. The distribution in the visual direction is smoothed to minimize the side lobe of the light intensity spectrum, the sudden brightness drop (cutoff) with respect to the visual field can be reduced, and the lamp image can be reduced.

Since the display device 72 according to the embodiment of the present invention includes the optical sheet 53 described above, the light collection / diffusion characteristics are improved, the luminance in the front direction (observer side) F is improved, and the light intensity is increased. While smoothing the distribution in the visual direction to minimize the side lobes of the light intensity spectrum, it is possible to mitigate the sudden decrease in brightness (cutoff) with respect to the visual field, and using light with a reduced lamp image, Since the image is displayed, the brightness in the front direction (observer side) F can be improved, the viewing angle dependency of the light intensity can be reduced, and an image with high image quality can be displayed.
Hereinafter, the present invention will be specifically described based on examples. However, the present invention is not limited only to these examples.

First, as a diffusion base material, a transparent resin in which light diffusion particles are dispersed was examined.
Example 1
A diffusion base material and a light diffusion transmission layer were molded by a multi-layer extrusion method based on MS (methyl methacrylate / styrene). At that time, a unit lens for a light diffusing and transmitting layer having a lens pitch of 100 μm and a contact angle of 50 degrees was formed on the light diffusing and transmitting layer side. A diffusion member having a thickness of 2 mm (a diffusion member of Example 1) was prepared by setting the thickness of the diffusion base material to 1.5 mm and the thickness of the light diffusion / transmission layer to 0.5 mm.

  Next, an optical film having a light-transmitting substrate unit lens on one surface and a reflective layer formed on the other surface corresponding to the position of the light-transmitting substrate unit lens was prepared. Thereafter, the surface of the diffusing member of Example 1 on which the unit lens for the light diffusing / transmitting layer is not shaped and the surface on which the reflective layer of the optical film is provided are joined with an adhesive, and the surface of Example 1 is joined. An optical sheet was produced.

  The optical sheet of Example 1 was set so that the distance from the cold cathode tube was 3 mm, and a direct type backlight unit was produced. This was installed on the back side of the liquid crystal display device, and it was confirmed whether the lamp image could be seen from the front side. When the optical sheet of Example 1 was used, the lamp image was not visible.

(Comparative Example 1)
A diffusion base material and a light diffusion transmission layer were molded by a multi-layer extrusion method based on MS (methyl methacrylate / styrene). At that time, a light diffusion / transmission layer unit lens having a lens pitch of 100 μm and a contact angle of 40 degrees was formed on the light diffusion transmission layer side. A diffusion member having a thickness of 2 mm (a diffusion member of Comparative Example 1) was prepared by setting the thickness of the diffusion base material to 1.8 mm and the thickness of the light diffusion / transmission layer to 0.2 mm.
Next, an optical sheet of Comparative Example 1 was produced in the same manner as Example 1 except that the diffusion member of Comparative Example 1 was used. Further, the lamp image was evaluated in the same manner as in Example 1. When the optical sheet of Comparative Example 1 was used, a lamp image was seen and the level was NG.

(Comparative Example 2)
First, a commercially available MS (methyl methacrylate / styrene) -based diffusion member having a thickness of 2 mm (a diffusion member of Comparative Example 2) was prepared.
Next, an optical sheet of Comparative Example 2 was produced in the same manner as in Example 1 except that the diffusion member of Comparative Example 2 was used. Further, the lamp image was evaluated in the same manner as in Example 1. When the optical sheet of Comparative Example 2 was used, a lamp image was seen and the level was NG.

Next, the thing using the thermoplastic resin as a diffusion base material was examined.
(Create diffusion member)
First, a polyethylene terephthalate (PET) chip, a poly-4-methylpentene-1 chip incompatible with PET as a thermoplastic resin, and a polyethylene glycol having a molecular weight of 4000 as a dispersant were mixed. This was vacuum dried at 180 ° C. for 3 hours, then supplied to an extruder, melted at 285 ° C. by a conventional method, and introduced into a T-die composite die to obtain a melt sheet.
The obtained melt sheet was cooled and solidified while closely contacting on a cooling drum maintained at a surface temperature of 25 ° C. to obtain an unstretched film.
Subsequently, the unstretched film was stretched in the longitudinal direction using a roll group heated to 98 degrees, and then cooled in a roll group at 25 ° C. to obtain a uniaxially stretched film.
Next, the uniaxially stretched film is guided to a tenter while being held by a clip, stretched in a direction perpendicular to the longitudinal direction in a heated atmosphere at 105 ° C., and further heat-treated at 220 ° C. in the tenter while relaxing in the width direction. And uniformly cooled. Finally, this was wound up to obtain a diffusion base material sample of Test Example 1 made of a thermoplastic resin.

  Except that the amount of poly-4-methylpentene-1 added and the draw ratio were changed, diffusion base samples of Test Examples 2 to 23 made of a thermoplastic resin were obtained in the same manner as Test Example 1.

Table 1 shows the measurement results of the total light transmittance (JIS K7361-1) and haze value (JIS K7136) of the diffusion base material samples of Test Examples 1 to 23 obtained. The total light transmittance and the haze value could be changed by changing the addition amount of poly-4-methylpentene-1 and the stretching ratio.
The total light transmittance of the light diffusing and transmitting layer and the protective layer used in this test example was 99% or more, and the haze value was less than 1%.

  Next, the light diffusing / transmitting layer, the unit lens for the light diffusing / transmitting layer, the protective layer, the unit lens for the diffusing substrate, and the like are joined to the diffusion substrate samples of Test Examples 1 to 23, and the diffusing member of Test Examples 1 to 23 A sample was created. In addition, PET was used as the light diffusion / transmission layer and the protective layer. The refractive indexes of the unit lens for the light diffusing and transmitting layer and the exit surface lens array (unit lens for the diffusing substrate) were both 1.5.

  About the diffusion base material samples of Test Examples 1-4, 6-9, 11-14, 19-21, and 23, specifically, they were integrally formed with the light diffusion / transmission layer by the laminated integral extrusion method, and Test Example 1 -4, 6-9, 11-14, 19-21, 23 diffusion base material / light diffusion transmission layer samples. The surface of the sample on the light diffusing and transmitting layer side was subjected to easy adhesion treatment. A photo-curing acrylic resin was applied to the surface subjected to the easy adhesion treatment, and then a die cut in advance into a hemispherical cylindrical mold was pressed. In this state, the diffusion base material / light diffusion / transmission layer samples of Test Examples 1 to 4, 6 to 9, 11 to 14, 19 to 21 and 23 are irradiated with UV light to form unit lenses for the light diffusion / transmission layer. The diffusion member samples of Test Examples 1 to 4, 6 to 9, 11 to 14, 19 to 21, and 23 were obtained.

  In addition, for the diffusion base material samples of Test Examples 5 and 10, first, easy adhesion treatment was performed on one surface thereof. Thereafter, a photocurable acrylic resin was applied to the surface subjected to the easy adhesion treatment, and a die cut in advance into a hemispherical cylindrical mold was pressed. In that state, the diffusion base material samples of Test Examples 5 and 10 were irradiated with UV light to form a light diffusion / transmission layer unit lens, and the diffusion member samples of Test Examples 5 and 10 were obtained.

  In addition, the diffusion base material sample of Test Example 15 was joined to the light diffusion / transmission layer by the laminated integral extrusion method to obtain a diffusion base material / light diffusion transmission layer sample of Test Example 15. Next, an easy adhesion treatment was performed on the surface of the sample on the light diffusing and transmitting layer side. An acrylic resin dissolved in a solvent was applied to the surface subjected to the easy adhesion treatment, and the cut mold was pressed against a heated hemispherical microlens mold. Then, it removed from the metal mold | die and the diffusion member sample of Test Example 15 was obtained.

  For the diffusion base material sample of Test Example 16, the protective layer made of PET having a layer thickness of 5 μm was integrally formed with the light diffusion / transmission layer by the laminated integrated extrusion method in a state where the protective layer was laminated on the diffusion base material side. Sixteen samples of protective layer / diffusion substrate / light diffusion transmission layer were used. The surface of the protective layer / diffusion substrate / light diffusion / transmission layer sample of Test Example 16 on the light diffusion / transmission layer side was subjected to an easy adhesion treatment. A photo-curing acrylic resin was applied to the surface subjected to the easy adhesion treatment, and a die cut in advance into a hemispherical cylindrical mold was pressed. In that state, the protective layer / diffusion substrate / light diffusion / transmission layer sample of Test Example 16 was irradiated with UV light to form a light diffusion / transmission layer unit lens, and a diffusion member sample of Test Example 16 was obtained.

  In addition, the diffusion base material sample of Test Example 17 was integrally formed with the light diffusion / transmission layer by the laminated integral extrusion method to obtain the diffusion base material / light diffusion transmission layer sample of Test Example 17. The surface of the sample on the light diffusing and transmitting layer side was subjected to easy adhesion treatment. A photo-curing acrylic resin was applied to the surface subjected to the easy adhesion treatment, and then a die cut in advance into a hemispherical cylindrical mold was pressed. In this state, the light diffusing and transmitting layer unit lens was formed by irradiating the diffusion member sample of Test Example 17 with UV light. Thereafter, an exit surface lens array (a unit lens for a diffusion base material) was formed using a photocurable acrylic resin by the same method, and a diffusion member sample of Test Example 17 was obtained.

  For the diffusion base material sample of Test Example 18, the protective layer made of PET having a layer thickness of 5 μm was integrally formed with the light diffusion / transmission layer by the laminated integral extrusion method in a state where the protective layer was laminated on the diffusion base material side. Eighteen protective layers / diffusion base materials / light diffusion transmission layer samples were prepared. The surface of the protective layer / diffusion substrate / light diffusion / transmission layer sample of Test Example 18 on the light diffusion / transmission layer side was subjected to an easy adhesion treatment. A photo-curing acrylic resin was applied to the surface subjected to the easy adhesion treatment, and a die cut in advance into a hemispherical cylindrical mold was pressed. In this state, the protective layer / diffusion substrate / light diffusion / transmission layer sample of Test Example 18 was irradiated with UV light to form a light diffusion / transmission layer unit lens. Then, the exit surface lens array (unit lens for diffusion base material) was formed using a photocurable acrylic resin by the same method, and the diffusion member sample of Test Example 18 was obtained.

Moreover, about the diffusion base material sample of Test Example 22, after forming a light diffusion / transmission layer unit lens on a separately prepared light diffusion transmission layer using a photocurable acrylic resin, the diffusion base material is formed using an adhesive material. (Diffusion method) to obtain a diffusion member sample of Test Example 22.
The preparation conditions for the diffusion member samples of Test Examples 1 to 23 are summarized in Table 1.

(Creation of optical sheet, backlight unit, liquid crystal display)
The diffusion member samples of Test Examples 1 to 23 were cut into a 37-inch size, and four sides were bonded to a transparent lens sheet having a thickness of 2 mm with a double-sided tape, thereby producing optical sheets of Test Examples 1 to 23. The width of the double-sided tape was 5 mm so that the double-sided tape did not enter the image display area.
The optical sheets of Test Examples 1 to 23 were arranged with respect to the backlight so that the unit lenses for the light diffusing and transmitting layer were opposed to the cold cathode tubes, and the backlight units of Test Examples 1 to 23 were created. In addition, it was possible to prevent the diffusing member from sagging on the light source side of the backlight by bonding to a transparent lens sheet having a thickness of 2 mm.
For the diffusion member samples of Test Examples 1 to 14 and 16 to 23 other than the diffusion member sample of the hemispherical microlens type test example 15, the major axis direction of the hemispherical cylindrical type light diffusion / transmission layer unit lens is The backlight is arranged so as to be parallel to the long axis direction of the linear light source.
Furthermore, the backlight units of Test Examples 1 to 23 were arranged on the side opposite to the front direction (observer direction) F with respect to the liquid crystal display panel, thereby producing liquid crystal display devices of Test Examples 1 to 23.

(Diffusion evaluation of optical sheet)
The evaluation of the diffusivity is a luminance distribution obtained by displaying a solid white image on the liquid crystal display panels of the liquid crystal display devices of Test Examples 1 to 23 and measuring the luminance in the vertical direction of the cold cathode tube at different positions. Performed by data.
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.

As a result, the optical sheets of Test Examples 1, 3, 4, 8, 9, and 14 to 23 had a standard deviation σ of luminance change within 1%, and the optical sheet was determined to have good diffusibility. However, in the optical sheets of Test Examples 2, 5 to 7, and 10 to 13, the standard deviation σ of the luminance change was more than 1%, and it was determined that the optical sheet had poor diffusibility. The optical sheets of Test Examples 2, 5-7, and 10-13 were considered to be outside the scope of the present invention.
In addition, although the diffusing member sample of Test Example 1 had good diffusibility, the total light transmittance was low, and the displayed image was extremely dark.

It is a cross-sectional schematic diagram of the display apparatus which is embodiment of this invention. It is a plane schematic diagram which shows the positional relationship of the light source of the backlight unit which is embodiment of this invention, and the unit lens for light diffusion transmissive layers. It is the cross-sectional schematic diagram which joined the protective film or / and the unit lens for diffusion base materials to the diffusion member which is embodiment of this invention. It is a cross-sectional schematic diagram explaining the path | route of the light in the diffusion member which is embodiment of this invention. It is a cross-sectional schematic diagram of the display apparatus which is embodiment of this invention. It is a perspective view of an optical film. 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

H, K ... light, P, Q ... pitch, l ... tangent, T ... substrate thickness of the film, one surface and the tangent line l is the angle of theta ... base film, axial n of theta _{41 ...} lenticular lens Angle formed with the axial direction m of the linear light source, 1, 11 ... optical film, 4 ... V-groove, 13 ... valley, 14 ... gap, 15 ... light transmission opening, 16, 18 ... light transmission substrate Unit lens, 16a ... first apex, 16b ... first inclined surface, 17 ... light transmitting substrate, 17a ... surface opposite to the observer, 17b ... observer side (flat surface), 18a ... second Top part, 18b ... Second inclined surface, 18c ... Flat surface, 19 ... Unit lens for diffusion base material, 22 ... Optical mask, 23 ... Base material, 23a ... Surface opposite to the observer, 23b ... Surface on the observer side 25 ... diffusion member, 26 ... diffusion substrate, 26a ... surface opposite to the observer, 26b ... surface on the observer side, 27 ... light diffusion Overlayer, 28 ... Unit lens for light diffusing and transmitting layer, 29 ... Fixing element (rib), 30 ... Junction point, 31, 33 ... Polarizing plate, 32 ... Liquid crystal panel, 35 ... Image display element, 37 ... Protective film, 41 ... light source, 43 ... reflecting plate (reflective film), 45 ... backlight part, 52, 53 ... optical sheet, 55,56 ... backlight unit, 70,72 ... display device, 182 ... diffusing film, 184 ... light diffusing film 185 ... BEF, 186 ... transparent member, 187 ... unit prism.

Claims (23)

A diffusing member for controlling an illumination optical path of a display,
The diffusion member is composed of a diffusion base material and a light diffusion / transmission layer, and is formed by superimposing an observer side surface of the light diffusion transmission layer on a surface opposite to the observer of the diffusion base material,
The diffusion base material has a light diffusion region dispersed in a transparent resin, has a total light transmittance of 40% to 80%, and a haze value of 98% or more,
The light diffusing and transmitting layer is composed of a base material and a unit lens for the light diffusing and transmitting layer, and the plurality of unit lenses for the light diffusing and transmitting layer are arranged at a constant pitch on a surface opposite to the observer of the base material. And
The diffusion member according to claim 1, wherein the base material has a total light transmittance of 80% or more and a haze value of 95% or less. The shape of the unit lens for the light diffusing and transmitting layer is a convex curved surface shape or a triangular prism shape, and has a first apex portion having an arcuate surface or a ridgeline, and a first inclined surface extending from the first apex portion to the base material. And
The diffusing member according to claim 1, wherein a distance between the first inclined surfaces facing each other gradually decreases as going to the first top. The refractive index of the light diffusion / transmission layer is n, the pitch of the unit lenses for the light diffusion / transmission layer is P, and when viewed in cross section, the first inclined surface is bonded to the base material from the junction point. When the angle between the tangent to the inclined surface and the surface opposite to the viewer of the substrate is θ,
The diffusion member according to claim 2, wherein a thickness T of the base material satisfies the following formula (1).

  The said light-diffusion area | region is a light-diffusion particle, The thickness of the said diffusion base material is 0.1-5 mm, The diffusion member of any one of Claims 1-3 characterized by the above-mentioned.   The said transparent resin is a thermoplastic resin, the said light-diffusion area | region contains a bubble, The thickness of the said diffusion base material is 25-500 micrometers, The any one of Claims 1-3 characterized by the above-mentioned. The diffusing member described.   The diffusion member according to claim 5, wherein the diffusion base material is stretched in at least one axial direction.   The diffusion member according to claim 1, wherein the light diffusion / transmission layer does not include light diffusion particles.   The diffusion member according to claim 1, wherein the light diffusion / transmission layer is made of a thermoplastic resin.   The diffusing member according to claim 8, wherein the base material of the light diffusing and transmitting layer is stretched in at least one axial direction.   The diffusion member according to any one of claims 1 to 9, wherein the diffusion base material and the light diffusion / transmission layer are integrally formed by a multilayer extrusion method.   The diffusion member according to claim 1, wherein the diffusion base material and the base material of the light diffusion / transmission layer are integrally formed by a multilayer extrusion method.   The diffusing member according to claim 10, wherein the diffusing member is stretched in at least one axial direction.   The diffusion member according to claim 1, wherein the diffusion base material and the light diffusion / transmission layer are laminated with an adhesive or an adhesive.   The diffusion member according to any one of claims 1 to 9, wherein the diffusion base material and the base material of the light diffusion / transmission layer are laminated with an adhesive or an adhesive.   An optical sheet for controlling an illumination optical path of a display, wherein the optical sheet includes the diffusing member according to any one of claims 1 to 14 and an optical film, and the surface of the diffusing member on a viewer side. A surface opposite to the observer of the optical film is formed by being overlapped, and the optical film is composed of a light-transmitting substrate and a unit lens for the light-transmitting substrate, and the observer side of the light-transmitting substrate. A plurality of light transmission substrate unit lenses are arranged at a constant pitch on the surface, the shape of the light transmission substrate unit lenses is a convex curved surface, the second apex having an arcuate surface, A second inclined surface extending from the second top to the light-transmitting substrate, and formed so that the distance between the opposing second inclined surfaces gradually decreases as going to the second top. An optical sheet characterized by comprising: Between the optical film and the diffusing member, a plurality of light masks and an opening for light transmission separating the light masks are provided,
The optical sheet according to claim 15, wherein the light transmission opening is provided corresponding to the second top of the unit lens for light transmission substrate.   The dot-shaped or linear rib is arranged between the optical film and the diffusing member, and the optical film and the diffusing member are integrally laminated via the rib. The optical sheet according to claim 16.   The optical sheet according to any one of claims 15 to 17, wherein the viewer-side surface of the diffusing substrate is a substantially flat surface.   The optical sheet according to any one of claims 15 to 18, wherein a plurality of unit lenses for the diffusion base are arranged at a constant pitch on a surface of the diffusion base on the viewer side.   A backlight unit comprising the optical sheet according to claim 15 and a light source.   The light source is a linear light source, and the shape of the light diffusion / transmission layer unit lens is a lenticular type, and when viewed in plan, the major axis direction of the lenticular lens and the major axis direction of the linear light source The backlight unit according to claim 20, wherein an angle formed is 20 degrees or less.   A display apparatus comprising: an image display element that transmits and blocks light in pixel units to display an image; and the backlight unit according to any one of claims 20 and 21.   The display device according to claim 22, wherein the image display element is a liquid crystal display element.

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