JP2007256575A - Lens array sheet, optical sheet, and back light - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens sheet which is excellent in the control of the diffusion angle of existing light rays from a light source and is superior in the availability of the existing light rays in order to obtain high luminance, an optimum viewing angle, a high contrast or the like, and to provide an optical sheet and a back light with the optical sheet. <P>SOLUTION: In the lens array sheet, which has a lens surface where a plurality of convex unit lenses are arrayed in two dimensions at a predetermined pitch and a flat surface on the opposite side from the lens surface, a light reflective layer reflecting a light beam to a light non-convergence surface region of the lens is formed on the flat surface. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a lens array sheet, an optical sheet, and a back provided with the optical sheet, which can optimize the viewing angle according to the liquid crystal display device and improve the luminance of efficiently emitting backlight light to the liquid crystal panel side. Regarding light.

  In recent years, liquid crystal display devices using liquid crystal panels have been used as image display means for notebook personal computers in the OA field, displays for personal computers, information terminal devices, etc., information display equipment for information appliances such as large-screen TVs, and mobile phones. In addition, it has been used in various fields as an image display means for personal digital assistance (PDA). Such a liquid crystal display device is a transmissive type, and a light source is provided on the back side of the liquid crystal panel, and a surface light source device that irradiates the liquid crystal panel by converting light from the light source into surface light emission, a so-called backlight is provided. It has been adopted. Such a backlight method is roughly divided into a light source such as a cold cathode fluorescent tube (CCFT) along a side end portion of a flat light guide plate made of acrylic resin having excellent light transmittance. There are a light guide plate light guide method (edge light method) in which light from the light source is multiply reflected within the light guide plate, and a direct type method in which a light source is arranged on the back of a liquid crystal panel that does not use the light guide plate.

  Recently, for a small-sized liquid crystal display device of 20 inches or less used for a notebook personal computer or a portable information terminal, a light guide light guide system which can achieve low power consumption and can be easily thinned has become mainstream. The direct type is used.

  A liquid crystal display device equipped with a general light guide plate light guide type backlight has, for example, a color filter sandwiched between a transparent substrate and a polarizing plate at the top, a liquid crystal panel composed of a liquid crystal layer, and a backlight on the lower surface side. Is provided.

  The backlight has a light guide plate made of transparent PMMA (polymethyl methacrylate) or the like having a substantially rectangular plate shape, a diffusion film (diffusion layer) on the light emission surface on the upper surface side of the light guide plate, and the lower surface side of the light guide plate, A scattering reflection pattern part (printing pattern, groove, dot, etc.) that scatters and reflects the light introduced into the light guide plate efficiently and uniformly in the direction of the liquid crystal panel is formed, and a reflective film (reflection) is formed below the scattering reflection pattern part Layer). A light source is attached to the light guide plate along the side edge, and a high-reflectance lamp reflector is provided so as to cover the back side of the light source that allows light from the light source to enter the light guide plate efficiently.

The scattering reflection pattern part is formed by printing a mixture of white titanium dioxide (TiO ₂ ) powder in a transparent resin or the like in the form of dots, for example, conical, convex lens, Mt. Fuji dots, or V-shaped grooves. It can be formed by injection molding or hot pressing together with the molding of the light guide plate. This scattering reflection pattern portion imparts directivity to the light incident on the light guide plate and guides the light toward the light exit surface, and is one means for increasing the brightness.

Furthermore, it has been proposed to provide a prism film (prism layer) having a light condensing function between the diffusion film and the liquid crystal panel in order to improve the light utilization efficiency and increase the luminance. This prism film collects the light emitted from the light exit surface of the light guide plate and diffused by the diffusion film with high efficiency on the effective display area of the liquid crystal panel.
A liquid crystal display device equipped with a general direct type backlight has, for example, a color filter sandwiched between a transparent substrate and a polarizing plate at the top, a liquid crystal panel composed of a liquid crystal layer, and a backlight on the lower surface side. It has been.

  The backlight is composed of a plurality of light sources extending in a columnar shape in a housing having an opening on the front surface, a highly reflective reflective layer disposed inside the housing, and a diffusion plate that diffuses emitted light. Yes.

  The direct type method consumes more power by using multiple light sources than the light guide plate light guide method, but the light guide is unnecessary and the surface brightness can be kept high even if the screen is enlarged. Therefore, a direct type is often used as a backlight of a large liquid crystal display device.

  However, in the direct type, light directed directly from the light source to the viewer side (liquid crystal panel side) is emitted as diffused light, so that it is recognized that the directivity of light from the light source is reduced, and the viewing angle dependency is reduced. There is a problem that it does not lead to improvement. The viewing angle dependency is, for example, what is supposed to be displayed in black when the liquid crystal display device is observed from a direction of a certain angle or more, or a decrease in contrast due to gradation inversion, contrast inversion, etc. , It means that there is a state where the observer cannot see the image accurately. The reason why this viewing angle dependency occurs is mainly due to the twist of the liquid crystal molecules, the refractive index anisotropy of the liquid crystal molecules, the polarization characteristics of the polarizing plate, and the surface light source.

Furthermore, as a light source, a cold cathode tube (CCFT) or LED (Light Emitting)
In the case of Diode), since the shape of the light source that emits light can be directly visually recognized through the diffusion plate that diffuses the emitted light, a resin plate having a very strong light scattering property is used as the diffusion plate. This diffuser plate usually needs a thickness of about 1 mm to 3 mm in order to give strong diffusibility, and because of the thickness, there is not a little light absorption, the light quantity from the light source is reduced, and the liquid crystal display is displayed. There is a problem of darkening.

  If the above diffusion sheet alone is not sufficient, when one or two prism sheets are used orthogonally, the direct-type backlight has the highest intensity light emitted vertically from the light source directly on the prism surface. Although the light reflected and reflected by the reflective layer on the lower surface of the light source can be reused, since the reflectance of the reflective layer on the lower surface of the light source is not 100%, the reusable amount of light is reflected between the reflective layer and the diffuser. Since the total light quantity from the light source does not reach the liquid crystal panel, the liquid crystal display screen becomes dark due to the decrease in the light quantity.

  In addition, when a prism sheet is used, there is a drawback that about 10% of emitted light is emitted at a deep angle that cannot be used for displaying a liquid crystal image.

  By the way, a large-sized liquid crystal display device of 20 inches or more is required to have low viewing angle dependency, high luminance, and high contrast, and a backlight mounted on the liquid crystal display device is also a liquid crystal display device. Accordingly, it is necessary to cope with optimization of viewing angle and improvement of luminance and contrast for efficiently emitting backlight light to the liquid crystal panel side.

  In particular, as described above, the conventional direct type backlight has a problem that the amount of transmitted light is reduced due to absorption and reflection of outgoing light by the diffusion plate, and further, there is a problem of direct image generation of the light source through the backlight. Since the emitted light is diffused in a direction that is not used for the display of the liquid crystal display device, there are problems such as a problem that the light use efficiency is low and the contrast is lowered.

The present invention has been made in view of the above-described problems. In order to achieve high brightness, optimum viewing angle, high contrast, and the like, the lens has excellent control of the diffusion angle of light emitted from a light source and efficiency of use of the emitted light. An object is to provide a sheet, an optical sheet, and a backlight including the optical sheet.

To achieve the above objectives, ie
The invention according to claim 1
A lens array sheet in which a plurality of unit lenses formed in a convex shape at a predetermined pitch are two-dimensionally arranged, and a lens array sheet having a flat surface opposite to the lens surface,
The lens array sheet is characterized in that a light reflecting layer that reflects light rays is formed on the non-light-condensing surface area of the lens on the flat surface.

The invention according to claim 2
2. The lens array sheet according to claim 1, wherein the lens array sheet is a lenticular lens sheet in which a plurality of convex cylindrical lenses formed at a predetermined pitch are arranged in parallel.

The invention according to claim 3
3. The lens array sheet according to claim 1, wherein the light reflecting layer is transferred from a transfer sheet having the light reflecting layer.

The invention according to claim 4
The lens array sheet according to any one of claims 1 to 3, wherein the light reflecting layer is a silver reflecting layer formed by a metal vapor deposition method or a metal ink printing method.

The invention according to claim 5
5. The lens array sheet according to claim 1, further comprising: a polarization separation film on a lens surface side; and a light diffusion plate on a light reflection layer side opposite to the lens surface; and the polarization separation film. And / or the lens array sheet and / or between the lens array sheet and the light diffusing plate.

The invention according to claim 6
A backlight of a liquid crystal display device comprising the optical sheet according to claim 5 and a light source,
The backlight is characterized in that the light diffusing plate side of the optical sheet is arranged on the light source side to be integrated.

  According to the present invention, the flat surface of the polarization separation film used for the optical sheet constituting the backlight of the liquid crystal display device and the lens array sheet is provided with the light reflecting layer that reflects the light beam to the non-light-condensing surface area of the lens. As a result, the use efficiency of light in the optical sheet and the reflectance of light in the region other than the light transmission opening (condensing surface) are increased, so that it is possible to suppress the loss of light quantity, and thereby the backlight using the optical sheet The display image is bright (high brightness), the lens shape, the lens pitch, the refractive index of the resin constituting the substrate sheet, etc., and the light transmission aperture (collection) are matched to the liquid crystal display device. By controlling the size of the light surface), it is possible to optimize the viewing angle and to obtain the optimum viewing angle (low viewing angle dependency) with the same brightness. It is possible to provide the door and the backlight having the optical sheet.

Further, according to the present invention, the direction of the lens of the lenticular lens array sheet constituting the optical sheet is arranged substantially parallel to the direction of the linear light source or at a predetermined angle, so that the light emitted from the light source is transmitted to each lens. As a result of reduced image formation, as many thin light source images as the number of lenses are arranged on the optical sheet, a direct image of the light source cannot be seen from the observer side, and a planar light source, that is, a surface light source It can be. Accordingly, it is not necessary to use a thick diffuser plate having a strong diffusivity as in the prior art, and light loss can be suppressed.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic perspective view showing an example of a lens array sheet of the present invention. FIG. 2 is a schematic longitudinal sectional view of the lens array sheet of the present invention shown in FIG. 1 in the horizontal direction. FIG. 3 is a schematic perspective view showing another example of the lens array sheet of the present invention. FIG. 4 is a schematic plan view of the lens array sheet of the present invention shown in FIG. 3 viewed from the lens side. FIG. 5 is a schematic plan view of the lens array sheet of the present invention shown in FIG. 3 as viewed from the opposite surface on the lens side. FIG. 6 is an explanatory view illustrating an example of a method for producing a lenticular lens array sheet as the lens array sheet of the present invention. 7-9 is a schematic sectional drawing which shows one Example of a structure of the optical sheet of this invention. FIG. 10 is a schematic cross-sectional view showing an example of the configuration of the backlight of the present invention. FIG. 11 is a schematic cross-sectional view showing an example of a liquid crystal display device provided with the backlight of the present invention.

  The lens array sheet of the present invention is a lens array sheet in which a plurality of unit lenses formed in a convex shape at a predetermined pitch are two-dimensionally arranged, and the lens surface opposite to the lens surface is a flat surface, The lens array sheet is characterized in that a light reflecting layer that reflects light rays is formed on the non-light-condensing surface area of the lens on the flat surface. Also, a lens array sheet in which a plurality of convex cylindrical lenses formed at a predetermined pitch are arranged in parallel and a lens array sheet having a flat surface opposite to the lens surface, the flat surface includes: The lens array sheet is characterized in that a light reflecting layer for reflecting a striped light beam in a longitudinal direction is formed on a non-light-condensing surface region of the convex cylindrical lens. It is a lens array sheet.

  As the lens array sheet in the present invention, for example, a lenticular lens array sheet in which unit lenses composed of cylindrical curved surfaces are arranged in one plane in a plane, or a dome having a bottom shape such as a circle, a rectangle, a hexagon, etc. For example, a lens array sheet in which unit lenses composed of a curved surface are two-dimensionally arranged in a plane can be used.

  Specifically, for example, as shown in FIG. 1, a lenticular lens array sheet in which unit lenses composed of cylindrical curved surfaces are arranged in one direction in a plane, and one side of a flat transparent substrate (1) And a non-condensing surface area of a lenticular lens array (2) formed by arranging unit lenses (2a) in one direction in a plane and a flat lens opposite to the lens surface of the transparent substrate (1). A lens array sheet (A) comprising a light reflecting layer (4) formed in (3) and an opening (5) at a position corresponding to the top of the cylindrical convex portion of the lenticular lens array (2) ). At this time, in order to collect incident light incident on the unit lens (2a), the opening (4) on the opposite surface on the unit lens (2a) side is formed in a shape having a focal point in or near the flat surface. is necessary. In addition, the longitudinal cross-sectional schematic in the horizontal direction of the lenticular lens array sheet | seat shown in FIG. 1 is shown in FIG.

The transparent substrate (2) is not particularly limited as long as it is a material that transmits at least visible light, and a plastic material is preferable in terms of mechanical strength, thinness, light weight, workability, and the like. As the plastic material, for example, an acrylic acid ester such as polymethyl methacrylate, polymethyl acrylate or the like having a refractive index of about 1.4 to 1.7 or a methacrylic acid ester homopolymer or polyethylene, polyethylene Examples thereof include resin materials such as polyester such as terephthalate and polybutylene terephthalate, polycarbonate and polystyrene.
The thickness of the transparent substrate is about 75 to 125 μm. Further, the surface of the transparent substrate may be subjected to corona discharge treatment, plasma discharge treatment or the like.

  A known method can be used as a method of forming the lenticular lens. For example, a mold having an uneven surface corresponding to the shape of the unit lens to be arranged, a method of transferring a shape such as a nickel (Ni) stamper by a hot press, an ultraviolet curable resin or an electron beam curable resin is used as a transparent base. After embossing with a roll embossing plate that is applied to the material and forming a lens-shaped mold, the lens is formed by irradiating ultraviolet rays or electron beams to cure the resin, and a resist material is formed by a photolithography method. There is a method in which a pattern is formed at a pitch and this is heated and melted to form a lens. The height of the lens is about 5 to 200 μm, and the pitch of the lens is appropriately selected according to the application, but is about 20 to 1000 μm.

  From the viewpoint of productivity, an ultraviolet curable resin or an electron beam curable resin is applied to a transparent substrate, embossed by a roll embossing plate in which a lens-shaped mold is formed, and then irradiated with ultraviolet rays or an electron beam. A method in which the lens and the transparent substrate are integrally formed by a method in which the lens is cured to form a lens is desirable.

  Examples of the ultraviolet curable resin or electron beam curable resin used in the present invention include, for example, a known ultraviolet curable resin or electron beam curable resin, typically a (meth) acryloyl group [(meth) in the molecule. An acryloyl group means an acryloyl group or a methacryloyl group. ], A composition comprising a prepolymer and / or a monomer having a polymerizable functional group such as a (meth) acryloyloxy group, an epoxy group or a mercapto group. For example, prepolymers such as urethane (meth) acrylate, epoxy (meth) acrylate, and silicone (meth) acrylate, and polyfunctional monomers such as trimethylolpropane tri (meth) acrylate and dipentaerythritol hexa (meth) acrylate are mainly used. It is a composition as a component. In order to make the prism layer and the lens layer have a high refractive index, it is preferable to use the above-mentioned polyfunctional monomer as a main component and a highly crosslinked type. The ionizing radiation curable resin is basically a solventless one, but a solvent diluted one may be used if necessary.

  When the ionizing radiation curable resin is cured with ultraviolet rays, a photopolymerization initiator such as acetophenones and benzophenones, and a photosensitizer such as n-butylamine, triethylamine, and tri-n-butylphosphine are contained in the resin. Add as appropriate. The ionizing radiation curable resin is usually cured by irradiation with an electron beam or an ultraviolet ray. In the case of electron beam curing, a cockcroft Walton type, a bandegraph type, a resonant transformation type, an insulated core transformer type, a linear type, An electron beam having an energy of 50 to 1000 keV, preferably 100 to 300 keV emitted from various electron beam accelerators such as a dynamitron type and a high frequency type is used. In the case of ultraviolet curing, an ultrahigh pressure mercury lamp, a high pressure mercury lamp, UV light from a light source such as a low-pressure mercury lamp, carbon arc, xenon arc, or metal halide lamp is used.

  Moreover, as a lens array sheet in the present invention, as shown in FIG. 3 (a part of the lens array sheet is shown), for example, a circular bottom shape formed on one side of a flat transparent substrate (10) A lens array (11) in which unit lenses (11a) each having a dome-shaped curved surface are two-dimensionally arranged in a plane, and a flat lens opposite to the lens surface of the transparent substrate (10) A lens array composed of a light reflecting layer (12) formed in the non-light-condensing surface area and an opening (13) through which light passes at a position corresponding to the top of the convex portion of the lens array (11) It may be a sheet (B). 3 is a plan view of a part of the lens array sheet shown in FIG. 3 viewed from the lens side, and FIG. 5 is a plan view of the lens array sheet viewed from the opposite side of the lens side.

The lens array (11) is formed by periodically arranging minute convex portions (unit lenses (11a) having a lens function on a transparent substrate (10). The unit lens (11a) has a circular bottom surface. In addition to having a shape, a two-dimensional array lens array in which unit lenses having a bottom surface shape such as a rectangle or a hexagon and having a dome-like curved surface are arranged in the plane is used. It is necessary to form a focal point in the flat surface of the opening (13) on the opposite surface on the unit lens (11a) side or in the vicinity thereof so that the incident light for the lens (11a) is condensed.

  As the transparent substrate (10) of the lens array sheet (B), the same substrate as the lenticular lens array sheet (A) can be used. The lens array can be formed using the same molding method as that for the lenticular lens array sheet (A).

  Hereinafter, a lenticular lens array sheet (A) will be exemplified as a lens array sheet of the present invention, and a manufacturing method thereof will be described with reference to FIG.

  In the method for producing a lenticular lens array sheet (A) as a lens array sheet of the present invention, first, an ultraviolet curable resin composition is applied to a molding surface of an embossing roll mold having a shape capable of giving a lens array shape. At the same time, the transparent substrate (1) such as a polyethylene terephthalate (PET) film is supplied to an embossing roll mold and irradiated with ultraviolet rays through the transparent substrate (1) to cure the ultraviolet curable resin. A convex cylindrical lens array (2) formed by arranging unit lenses (2a) which are resin moldings in one plane in a plane is polymerized and bonded to a transparent substrate (1), or a transparent substrate (1 ) Is coated with an ultraviolet curable resin composition, supplied to the above embossing roll mold, and irradiated with active energy rays through the transparent substrate (1) to cure the resin. At the same time, a convex cylindrical lens array (2) formed by arranging unit lenses (2a) made of a cured resin in one plane in a plane is polymerized and bonded to the transparent substrate (1) [( see a)].

  An ultraviolet curable resin that has adhesiveness on the flat surface of the transparent substrate (1) opposite to the convex cylindrical lens array (2) and has the property that the adhesiveness disappears when irradiated with ultraviolet rays. An adhesive UV-curable resin layer (20) is formed by applying a layer or laminating an adhesive, for example, a film-like UV-curable resin [see (b)].

  Next, ultraviolet rays (30) are irradiated through the convex cylindrical lens array (2), and a region corresponding to the opening is formed by the lens action (condensing) to form a hardened portion (21) [see (c)]. .

  Thereafter, the transfer sheet (40) on which the light reflecting layer (42) is formed on the base material (41) is superposed on the light reflecting layer (42) side and pressed, and an ultraviolet curable resin layer other than the cured portion (21). The light reflecting layer (42) is attached only to the uncured portion (22) by utilizing the adhesiveness of the resin to the uncured portion (22) [see (d)].

  Subsequently, the transfer sheet (40) is peeled off [see (e)], whereby a striped light reflecting layer (42) on the uncured portion (22) [corresponding to the light reflecting layer (4) in FIG. 1]. [See (f)].

Finally, from the light reflecting layer (42) side, the entire surface is irradiated with ultraviolet rays (30) to cure the uncured portion (22) [see (f)], and as the lens array sheet of the present invention shown in FIG. A lenticular lens array (2) formed by arranging unit lenses (2a) in one direction in a plane on one side of a flat transparent substrate (1), and the opposite side of the lens surface of the transparent substrate (1) The light reflecting layer (4) formed in the non-light-condensing surface region (3) of the flat lens and the opening (5) at a position corresponding to the top of the cylindrical convex portion of the lenticular lens array (2). And a lenticular lens array sheet (A).

  The transfer sheet having a light reflecting layer composed of a silver reflective layer by a metal vapor deposition method or a metal ink printing method used in the present invention has a silver color by a metal vapor deposition method or a metal ink printing method which is configured to be peelable on a substrate. Obtained by forming a reflective layer. Examples of the metal include aluminum (Al), silver (Ag), tin (Sn), and the like. Examples of methods for forming a silver reflective layer by metal vapor deposition include conventional metal thin films such as vacuum vapor deposition, sputtering, ion plating, reactive vacuum vapor deposition, reactive sputtering, and reactive ion plating. It is formed by the forming method. The thickness of the metal reflective layer is not particularly limited, but is usually appropriately selected from the range of about 5 nm to 200 nm. If the thickness is less than 5 nm, the intrinsic action of the metal deposition layer, that is, the light selective reflectivity is not exhibited, which is not preferable. When aiming at the reflectivity of a metal vapor deposition layer, it is usually preferable to be about 30 nm or more. On the other hand, even if it exceeds 200 nm, the reflectance is not further improved, which is not preferable. Moreover, as a method of forming a silver reflective layer by a metal ink printing method, for example, a metal ink in which a metal powder is dispersed in a resin binder dissolved by adding an organic solvent can also be formed by a gravure printing method or the like. When adjusting the metal ink, the particle size of the metal powder is desirably in the range of 1 to 100 μm, and as the binder resin, acrylic resin, polyester resin, polyurethane resin, wax, or the like is used. The organic solvent is not particularly limited as long as it can dissolve the above resin.

  A protective layer can be provided on a flat surface including the light reflecting layer. The protective layer should be light transmissive and have excellent physical properties such as abrasion resistance, solvent resistance, and heat resistance, improve the abrasion resistance of the lens array sheet, and damage the surface in the backlight manufacturing process. The occurrence of defects can be reduced, the yield can be increased, and the cost can be reduced. In addition, by providing this protective layer with an ultraviolet ray absorbing action, when used in a backlight, the ultraviolet ray from the light source is absorbed by the protective layer, thereby reducing the transmitted ultraviolet ray, improving the light resistance, and the liquid crystal display. The product life of the device can be extended. Furthermore, it is possible to convert ultraviolet light contained in light emitted from a cold cathode tube, which is one of the light sources, into visible light by providing the protective layer with an ultraviolet absorbing action containing a fluorescent substance. The amount of light can be used effectively.

  Next, the optical sheet of the present invention using the lens array sheet such as the lenticular lens array sheet (A) obtained above will be described.

  7 to 9 show an embodiment of the optical sheet of the present invention. The optical sheet of the present invention includes a polarization separating film (50) on the lens (2) side of the lens array sheet (A) and a light diffusion plate (70) on the light reflecting layer (4) side opposite to the lens (2) side. And a light diffusion sheet (60) is disposed between the polarization separation film and the lens array sheet (A) and / or between the lens array sheet (A) and the light diffusion plate (50). This is an optical sheet characterized by being integrally formed.

  The optical sheet (C) of the present invention shown in FIG. 7 has a configuration in which a light diffusion sheet (60) is disposed between the polarization separation film (50) and the lens (2) side of the lens array sheet (A).

  The optical sheet (D) of the present invention shown in FIG. 8 has a configuration in which a light diffusion sheet (60) is disposed between the light reflection layer (4) side of the lens array sheet (A) and the light diffusion plate (70). is there.

  Further, the optical sheet (E) of the present invention shown in FIG. 9 is provided between the polarization separation film (50) and the lens (2) side of the lens array sheet (A), and the light reflecting layer of the lens array sheet (A). (4) The light diffusing sheet (50) is disposed between the side and the light diffusing plate (60).

  In the above-described optical sheet, it is preferable that the members are integrally formed. This is because the apparatus can be made compact, the number of parts can be reduced, the manufacturing can be simplified, and the strength obtained can be improved. Each member can be joined using an adhesive, a pressure-sensitive adhesive, a double-sided tape, or the like if the member itself does not have a predetermined level of shape maintenance ability. It can be carried out by applying or applying an adhesive, a pressure-sensitive adhesive or a double-sided tape that is optically transparent to a part or all of the joint surface of the member, that is, has a high light transmittance. More preferably, bonding can be performed using an adhesive or the like having a refractive index close to the refractive index of each member.

  As the polarization separation film used in the present invention, a film having reflective polarization can be used. The reflective polarizing film is usually a polarizing film that transmits only light in a vibration direction parallel to one in-plane axis (transmission axis) and reflects other light. In other words, only the light component in the vibration direction parallel to the transmission axis is transmitted among the light incident on the polarizing film to exert the polarizing action, but unlike the conventional light absorption polarizing plate, it does not transmit the polarizing film. The light is not substantially absorbed by the polarizing film. Therefore, the light once reflected on the polarizing film can be returned to the light source side, and returned again to the reflective polarizing film by a reflecting element such as a light diffusion film installed on the light source side. Of the returned light, only the light component in the vibration direction parallel to the transmission axis is transmitted, and the rest is reflected again. That is, the intensity of the transmitted polarized light can be increased by repeating such transmission-reflection action. Specific examples of such a reflective polarizing film include brightness enhancement films manufactured by 3M Corporation: “DBEF (trade name) series” and “DRPF-H (trade name) series”. Alternatively, a circular polarizer may be used instead of such a linear polarizer. An example of a circular polarizer is a cholesteric type circular polarizer available as “Nipocs” (trade name) from Nitto Denko Corporation.

  More specifically, the polarizing film transmits P-polarized light and reflects S-polarized light. The reflected S-polarized light is transmitted between the light guide plate of the lighting unit and the light reflecting element disposed adjacent thereto. While repeating multiple reflections, the light is depolarized every time it passes through the diffuser, so that a part of it is converted to P-polarized light and reused efficiently, and transmitted from the polarizing film. Further, in this multiple reflection, the use of a multilayer reflection film as a light reflection element attached to the light guide plate can minimize the attenuation of light due to reflection, so that the polarizing film can work effectively.

  The light diffusing sheet used in the present invention, the light diffusing plate, a layer using a light scattering effect due to a difference in refractive index between the diffusing agent and the light transmissive resin by dispersing the diffusing agent in the light transmissive resin, A layer having an uneven surface on the surface of the light transmissive resin can be used. As the diffusing agent, for example, beads or fillers mainly composed of acrylic resin, polystyrene, polyethylene, urea resin, urethane resin, organic silicone resin, calcium carbonate, titanium oxide, silica, etc., or hollow beads are used. The average particle size of the diffusing agent used is preferably 1 to 50 μm from the viewpoint of handling, and two or more types having different types and particle sizes may be combined. Examples of the light transmissive resin include polyester resins, acrylic resins, polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, polyethylene resins, polypropylene resins, polyurethane resins, polyamide resins, and polyacetic acids. Vinyl resin, polyvinyl alcohol resin, epoxy resin, cellulose resin, silicone resin, polyimide resin, polysulfone resin, polyarylate resin and the like are used.

Furthermore, the light diffusing film can be used in any thickness depending on the purpose of use, but in general, it should be selected for the purpose of reducing the thickness and weight of the liquid crystal display device. The thickness of the film is usually in the range of about 5 to 1000 μm, preferably in the range of about 5 to 500 μm, and more preferably in the range of about 5 to 200 μm. The thickness of the light diffusing film is most preferably in the range of about 5 to 150 μm.

  As schematically shown in FIG. 10, the backlight (F) of the present invention includes a plurality of cold-cathode tubes (80) as a backlight illumination unit, which is a kind of fluorescent tube of a direct type backlight illumination unit. As an example of the optical sheet of the present invention, a light diffusing sheet (60) is disposed between the polarization separation film (50) and the lens (2) side of the lens array sheet (A) on the light source side. This is a backlight in which the light diffusing plate (70) side of the sheet (C) is disposed. The inner surface of the casing (90) is formed of an insulating material having light reflectivity, and may be formed of an aluminum die-cast casing, other metal materials, resin materials, or the like because of its strength and formability. Also, the shape can be arbitrarily changed in consideration of the improvement in strength. For example, ribs can be attached to the wall.

  The optical sheet (C) is securely fixed by attaching film fixtures (not shown) only at the four corners of the optical sheet while suppressing distortion of the optical sheet. The fixture is not particularly limited, and can be formed in any shape from a resin material or a metal material such as aluminum.

  Next, an example of a liquid crystal display device including the backlight of the present invention will be briefly described with reference to FIG. A segment side transparent electrode layer (102) is formed on the surface of the glass plate (101a) on the opposing surface of the glass plates (101a, 101b) facing each other. On the other hand, on the surface of the glass plate (101b). A color filter layer (103) is formed, and a common-side transparent electrode layer (105) is formed so as to overlap therewith. The distance between the opposing surfaces of the glass plate (101a) is held by the spacers (106a, 106b), and the liquid crystal for display (107) is interposed in the gap formed thereby. Further, polarizing plates (108a, 108b) are attached to the outer surfaces of the glass plates (101a, 101b). The liquid crystal display panel (G) is configured as described above, and further, on the back side, for example, a light source composed of a plurality of cold cathode tubes (70), which is a kind of fluorescent tube, and a lens of the lens array sheet (A) (2) The polarizing separation film (50) on the side and the light diffusing plate (70) on the light reflection layer (4) side opposite to the lens (2) side are provided, and further, the polarizing separation film (50) and the above A direct type backlight provided with the optical sheet of the present invention, which is configured integrally with a light diffusion sheet (60) disposed between the lens array sheets (A), is disposed.

  According to the present invention, the polarizing separation film used for the optical sheet constituting the backlight of the liquid crystal display device and the flat surface of the lens array sheet are provided with the metal reflection layer that reflects the light beam to the non-light-condensing surface area of the lens. As a result, the use efficiency of light in the optical sheet and the reflectance of light in the region other than the light transmission opening (condensing surface) are increased, so that it is possible to suppress the loss of light quantity, and thereby the backlight using the optical sheet In a liquid crystal display device, the display image is bright (high brightness), and the lens shape, lens pitch, refractive index of the resin constituting the base sheet, etc., light transmission aperture (condensing surface) are matched to the liquid crystal display device ) Can be designed to optimize the viewing angle, and the optimum viewing angle (low viewing angle dependency) can be obtained with the same brightness.

  Further, according to the present invention, the direction of the lens of the lens array sheet constituting the optical sheet is arranged substantially parallel to the direction of the linear light source or at a predetermined angle, so that the light emitted from the light source is reduced by each lens. Since an image is formed, and the same number of thin light source images as the number of lenses are arranged on the optical sheet, a direct image of the light source cannot be seen from the observer side, and a planar light source, that is, a surface light source and can do. Accordingly, it is not necessary to use a thick diffuser plate having a strong diffusivity as in the prior art, and light loss can be suppressed.

It is a schematic perspective view which shows an example of the lens array sheet of this invention. It is a schematic longitudinal cross-sectional view of the lens array sheet of this invention shown in FIG. 1 in the horizontal direction. It is a schematic perspective view which shows the other example of the lens array sheet of this invention. It is the schematic plan view seen from the lens side of the lens array sheet of this invention shown in FIG. It is the schematic plan view seen from the surface opposite to the lens side of the lens array sheet of this invention shown in FIG. It is explanatory drawing explaining an example of the manufacturing method of the lenticular lens array sheet as a lens array sheet of this invention. It is a schematic sectional drawing which shows one Example of a structure of the optical sheet of this invention. It is a schematic sectional drawing which shows one Example of a structure of the optical sheet of this invention. It is a schematic sectional drawing which shows one Example of a structure of the optical sheet of this invention. It is a schematic sectional drawing which shows an example of a structure of the backlight of this invention. It is a schematic sectional drawing which shows an example in the liquid crystal display device provided with the backlight of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,10 ... Transparent base material 2 ... Lenticular lens array 2a, 11a ... Unit lens 3 ... Non-light-collecting surface area 4, 12, 42 ... Light reflection layer 5, 13 ... Opening 11 ... 2D array lens array 20 ... Adhesive UV curable layer 21 ... Curing part (exposure part)
22 ... Non-cured part (non-exposed part)
DESCRIPTION OF SYMBOLS 30 ... Ultraviolet ray 40 ... Transfer sheet 41 ... Base material 50 ... Polarization separation film 60 ... Light diffusion sheet 70 ... Light diffusion plate 80 ... Cold cathode tube 90 ... Casing DESCRIPTION OF SYMBOLS 100 ... Liquid crystal display panel 101a, 101b ... Glass plate 102 ... Segment side transparent electrode layer 103 ... Color filter layer 105 ... Common side transparent electrode 106a, 106b ... Spacer 107 ... Display liquid crystal 108a, 108b ... Polarizing plate A ... Lenticular lens array sheet B ... Two-dimensional array lens array sheet C, D, E ... Optical sheet F ... Backlight G ... Liquid crystal Display board p ・ ・ ・ Lens pitch

Claims (6)

A lens array sheet in which a plurality of unit lenses formed in a convex shape at a predetermined pitch are two-dimensionally arranged, and a lens array sheet having a flat surface opposite to the lens surface,
The lens array sheet according to claim 1, wherein a light reflecting layer that reflects light rays is formed on the non-light-condensing surface area of the lens on the flat surface.   2. The lens array sheet according to claim 1, wherein the lens array sheet is a lenticular lens sheet in which a plurality of convex cylindrical lenses formed at a predetermined pitch are arranged in parallel.   The lens array sheet according to claim 1, wherein the light reflection layer is transferred from a transfer sheet having the light reflection layer.   The lens array sheet according to any one of claims 1 to 3, wherein the light reflecting layer is a silver reflecting layer formed by a metal vapor deposition method or a metal ink printing method.   5. The lens array sheet according to claim 1, further comprising: a polarization separation film on a lens surface side; and a light diffusion plate on a light reflection layer side opposite to the lens surface; and the polarization separation film. An optical sheet comprising a light diffusion sheet disposed between the lens array sheet and / or the lens array sheet and the light diffusion plate. A backlight of a liquid crystal display device comprising the optical sheet according to claim 5 and a light source,
A backlight comprising the optical sheet and a light diffusing plate side disposed on the light source side to be integrated.