JP2009109829A - Optical sheet, backlight unit, and display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet capable of attaining high brightness, high display quality, and saved electric consumption, and capable of obtaining a clear display image. <P>SOLUTION: The high brightness, the high display quality and the saved electric consumption are attained since an excellent light convergence-diffusion function is obtained by layering a plurality of optical element layers. In addition, an optical element is prevented from getting defective, by specifying a curvature radius of a top part in a cross-sectional shape of each optical element layer, as to all the optical element layers excepting the optical element layer provided in the position most distant from a light source, out of the layered optical element layers, and a shape of each optical element layer is prevented from collapsing, by specifying a Young's modulus of the optical element layer. The high brightness, the high display quality and the saved electric consumption are attained by this manner, and the clear display image is also obtained thereby. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical sheet used for illumination light path control, for example, a backlight unit using the optical sheet, and a display device.

  Some display devices typified by a liquid crystal display device (LCD) have a built-in light source (backlight) for displaying image information such as still images and moving images. There are roughly two types of backlights: a light guide plate light guide method (edge light method) and a direct type. The edge light system is a system in which light from a light source lamp is reflected multiple times within a light guide plate and emitted to the outside. The direct type is a method in which light from a light source lamp is directly emitted without using such a light guide plate.

  For example, a configuration shown in FIG. 19 is known as a liquid crystal display device equipped with an edge light type backlight unit. As shown in the figure, a light guide plate 79 having a substantially rectangular plate shape in a plan view is disposed on the lower surface side of the liquid crystal panel 72 sandwiched between the polarizing plates 71 and 73 in the figure. A diffusion film 78 is provided on the upper surface. A reflection film 77 is provided on the lower surface of the light guide plate 79 in the drawing. A light source lamp 76 is attached to a side end portion of the light guide plate 79, and a lamp reflector 81 for efficiently allowing light from the light source lamp 76 to enter the light guide plate 79 is provided so as to cover the back side of the light source lamp 76. It has been. In addition, prism films 74 and 75 having a light condensing function are provided between the diffusion film 78 and the liquid crystal panel 72 as shown in FIG. Arranged configurations are also known.

  A configuration shown in FIG. 21 is known as a liquid crystal display device on which a direct type backlight unit is mounted. As shown in the figure, a light source 51 made of a fluorescent tube or the like is provided on the lower surface side of the liquid crystal panel 72, and the light emitted from the light source 51 and diffused by the diffusion film 82 is efficiently used in the liquid crystal panel 72. The light is condensed on the display area. A reflector 52 is disposed on the back surface of the light source 51.

  In these liquid crystal display devices, the control of the viewing angle is left only to the diffusibility of the diffusion film, and the characteristic that the central portion in the front direction of the display becomes brighter and becomes darker toward the peripheral portion is unavoidable. As a solution to this, as shown in FIG. 23, a brightness enhancement film (Brightness Enhancement Film BEF: US 3M registered trademark, shown in FIG. 22) is conventionally disposed on the diffusion film 70, and the light diffusion film is disposed thereon. A method of arranging 70 is employed. The adoption of BEF allows display designers to achieve the desired on-axis brightness while reducing power consumption. As a patent document disclosing that a brightness control member having a repetitive array structure of prisms represented by BEF is adopted for a display, there are many known as exemplified in Patent Documents 1 to 3. Yes.

  On the other hand, an optical sheet using BEF as a luminance control member has problems such as unnecessarily emitting light in the lateral direction without simultaneously proceeding in the visual direction of the viewer, and unexpected light rays. For this reason, as shown in FIG. 24, the light intensity distribution emitted from the optical sheet using BEF has the light intensity when the viewer's visual direction, that is, the angle with respect to the visual direction F is 0 ° (corresponding to the axial direction). Although most enhanced, there is a problem that a small light intensity peak occurs in the vicinity of ± 90 ° from the front, that is, light (side lobes) emitted from the lateral direction is increased. A luminance distribution having such a light intensity peak is not desirable, and a smooth luminance distribution having no light intensity peak around ± 90 ° is more desirable. In addition, in recent years, development of a backlight unit and a display device that can realize a liquid crystal display device with low cost, high luminance, high display quality, and low power consumption is awaited. In response to this request, the present applicant has proposed a lens sheet exemplified in Patent Document 4 as an alternative product of a prism sheet represented by BEF.

  The lens sheet according to the above publication is illuminated in a display backlight unit having a lens portion formed of a unit lens group that is substantially flat on an incident surface side of light from an illumination light source and formed on an exit surface side that is a non-incident surface side. In the lens sheet for optical path control, the lens sheet is configured to include a light reflecting layer having an opening corresponding to the lens part on the exit surface side (see FIG. 25). As shown in FIG. 25, in the backlight unit using the lens sheet 83, the use efficiency of light is improved by adjusting the size and position of the opening of the light reflecting layer provided on the back surface, and the lens sheet 83 As a result, it is possible to increase the proportion of light emitted in the front direction S from the front and to suppress side lobes.

The above-mentioned BEF is generally used by laminating two sheets 94 so that the parallel directions of the prism groups 92 are substantially orthogonal to each other, and being incorporated in a display device together with the light diffusion plate 95 and the light diffusion sheet 91 ( (See FIG. 26). Even in a lens sheet having a light reflecting layer on the back surface described in Patent Document 4 or a lens sheet without a light reflecting layer, two or more sheets 94 are laminated so that the parallel direction of the lens array is substantially orthogonal to each other, The light diffusing plate 95 and the light diffusing sheet 91 may be used by being incorporated in a display device (see FIG. 27). 26, FIG. 27 and the subsequent drawings, in order to make the shape of the optical element easy to understand, the side view of the shape in which the longitudinal directions of the optical element arrays of the optical element sheets that are all stacked are parallel to each other. As shown in FIG. 28, the optical element arrays are actually stacked so as to be substantially orthogonal to each other.
Japanese Patent Publication No. 1-378001 JP-A-6-102506 Japanese National Patent Publication No. 10-506500 JP 2000-284268 A

  In the case of using the BEF, in the above-described backlight unit and display device, the casing is shaken by the transportation and packing in the state where the two BEF sheets 94 are laminated, and the BEF sheets move to each other. As shown in FIG. There is a problem in that the top of the prism 92 of the BEF sheet 94 located on the side is scraped to cause a defect, resulting in unevenness that can be visually recognized on the display screen.

  When the lens sheet of Patent Document 4 is used, in the same backlight unit and display device, the diffusion plate 95 set in the device together with the lens sheet 94 as shown in FIG. However, it may cause thermal deformation due to heat during use, and may be greatly convex or concave in the direction of the liquid crystal panel. At this time, pressure is applied to the surface of the lens 92 of the lens sheet 94 located on the backlight side. There is a problem that the collapse of the shape occurs and the display image is abnormal as described above.

  The present invention has been devised in view of the above circumstances, an optical sheet capable of realizing high brightness, high display quality, and power saving and capable of obtaining a clear display image, and a back It is to provide a light unit and a display device.

  In order to achieve the above object, an optical sheet according to the present invention is an optical sheet that converges or equalizes light from a light source, and a light incident surface on which light from the light source is incident and the light incident surface are A plurality of light emitting surfaces provided on the opposite surface for emitting light from the light incident surface, and a plurality of layers between the light incident surface and the light emitting surface, and the light emitted from the light emitting surface. An optical element layer having a convex optical element that controls at least one of a traveling direction, an emission range, a wavelength component, and a luminance distribution, and is provided at a position farthest from the light source among the plurality of optical element layers. For all of the optical element layers except the optical element layer formed, the top portion of the optical element layer is fitted in a range in which the formation pitch width is P and the width is 0.1 P in the vicinity of the top portion in the cross-sectional view of the optical element layer. Let Rt be the radius of curvature of The fitting radius of curvature Rt of the top satisfies Rt ≧ 0.1P, and the Young's modulus E ′ of the optical element layer at room temperature satisfies 200 ≦ E ′ ≦ 3000. To do.

  According to the present invention, it is possible to obtain an excellent light collecting and diffusing function by laminating a plurality of optical element layers, so that high luminance, high display quality, and power saving can be realized. In addition, for all the optical element layers except the optical element layer provided at the position farthest from the light source among the laminated optical element layers, the optical radius is determined by defining the curvature radius of the top of the cross-sectional shape of the optical element layer. The loss of the element can be prevented, and the deformation of the optical element layer can be prevented by defining the Young's modulus of the optical element layer. As a result, high brightness, high display quality, and power saving can be realized, and a clear display image can be obtained.

In the optical sheet, the plurality of optical element layers are each provided in a rectangular shape in plan view, and are disposed at positions where they overlap each other in plan view, and at least one set of two opposing sides of the optical element layer. It further comprises a support member for supporting the sides of the.
According to the present invention, since at least one set of the two opposing sides of the optical element layer is supported by the support member, it is possible to prevent the optical element layer from being displaced.

The optical sheet is characterized in that the support member supports all two opposing sides of the optical element layer.
According to the present invention, since the supporting member supports all the two sets of opposing sides of the optical element layer, it is possible to more reliably prevent the optical element layer from being displaced.

The optical sheet is characterized in that the support member is made of metal.
According to the present invention, since the support member is made of metal, it is resistant to thermal deformation, and the displacement between the optical element layers can be reliably prevented.

The optical sheet is characterized in that the support member is made of a resin.
According to the present invention, since the support member is made of resin, the processing of the support member is easy and the range of material selection is widened.

The optical sheet is characterized in that the optical element layer is made of a thermosetting resin, a thermoplastic resin, or a radiation curable resin, and the optical element layer is polymerized and bonded to the support member.
According to the present invention, the optical element layer is made of a thermosetting resin, a thermoplastic resin, or a radiation curable resin, and the optical element layer is polymerized and bonded to the support member. Can be reliably prevented.

In the optical sheet, the optical element layer is made of a thermosetting resin, a thermoplastic resin, or a radiation curable resin, and the optical element layer is the same member as the support member.
According to the present invention, the optical element layer is made of a thermosetting resin, a thermoplastic resin, or a radiation curable resin, and the optical element layer is the same member as the support member. Misalignment can be avoided.

The optical sheet is characterized in that the optical element includes at least one of a prism and a lens.
In the present invention, the configuration of the optical element differs depending on which of the light traveling direction, the emission range, the wavelength component, and the luminance distribution is controlled with priority. Therefore, in the present invention, since the optical element includes at least one of a prism and a lens, the design range of the optical element is widened, and efficient light control can be performed according to the application. An optical element layer can be obtained.

The optical sheet is characterized in that a light reflecting layer is provided on the optical element layer.
According to the present invention, since the light reflection layer is provided in the optical element layer, the light that is scattered by the optical element layer or reflected by the light exit surface and returned to the light source side is reused. Can do. Thereby, the utilization efficiency of light can be improved.

The optical sheet is characterized in that the light reflecting layer is provided on the light incident surface side of the optical element layer.
According to the present invention, since the light reflecting layer is provided on the light incident surface side of the optical element layer, more light in the optical element layer can be reused.

The optical sheet is characterized in that the light reflecting layer is provided on the light emitting surface side of the optical element layer.
According to the present invention, since the light reflecting layer is provided on the light emitting surface side of the optical element layer, the light reflected by the light emitting surface can be reliably reused.

The optical sheet is characterized in that the light reflecting layer is provided between the plurality of optical element layers.
According to the present invention, since the light reflecting layer is provided between the plurality of optical element layers, the light can be reused for each optical element layer.

In the optical sheet, the optical element layer includes a plurality of the optical elements, and the light reflection layer is provided between the plurality of optical elements in a plan view.
According to the present invention, since the optical element layer has a plurality of optical elements, and the light reflection layer is provided between the plurality of optical elements in a plan view, light leaks between the optical elements. Can be prevented and the light can be used. Thereby, the utilization efficiency of light can be further improved.

The optical sheet is characterized in that a light diffusing portion is provided inside the optical element.
According to the present invention, since the light diffusion portion is provided inside the optical element, it is possible to diffuse light in the optical element and make the light intensity distribution uniform.

A backlight unit according to the present invention includes the optical sheet described above and a light source that irradiates light to the light incident surface of the optical sheet.
According to the present invention, since the optical sheet capable of realizing high brightness, high display quality, and power saving and capable of obtaining a clear display image is provided, a high quality backlight unit is provided. Obtainable.

A display device according to the present invention includes the backlight unit described above, and a display that is provided on the light emission surface side of the optical sheet in the backlight unit and that performs display using light emitted from the light emission surface. And a panel.
According to the present invention, since a high-quality backlight unit is provided, a display device with high display characteristics can be obtained.

In the display device, the light source includes at least one of a cold cathode fluorescent lamp, an LED, an EL, and a semiconductor laser.
According to the present invention, since the light source includes at least one of a cold cathode fluorescent lamp, an LED, an EL, and a semiconductor laser, light corresponding to the light characteristics required by the display panel is supplied. Can do.

  According to the present invention, it is possible to provide an optical sheet, a backlight unit, and a display device that can realize high brightness, high display quality, and power saving and can obtain a clear display image. .

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a side view showing a display device including an optical sheet according to an embodiment of the present invention.
As shown in the figure, the display device 1 includes a display panel 2 and a backlight unit 3 so that images such as still images and moving images are displayed on the display panel 2 by light from the backlight unit 3. It has become.

  As the display panel 2, a liquid crystal panel is used in this embodiment. In addition to the liquid crystal panel, other types of devices such as a projection screen device, a plasma display, and an EL display may be used as long as they display images using the light of the backlight unit 3.

  The backlight unit 3 includes a light source unit 11 and an optical sheet 12, and light from the light source unit 11 is applied to the display panel 2 through the optical sheet 12.

  The light source unit 11 includes a plurality of light sources 13 and a light reflection plate 14 disposed on the opposite side of the display panel 2 with respect to the light sources 13. As the light source 13, for example, a light-emitting element such as a cold cathode fluorescent lamp, LED, EL, or semiconductor laser can be used. The light reflection plate 14 is an optical member that reflects light from the light source 13 toward the display panel 2 side.

  The optical sheet 12 includes a light diffusing plate 15, an optical element sheet (optical element layer) 16, a light diffusing sheet 17, and a support member 18, and is disposed between the light source unit 11 and the display panel 2. The optical sheet 12 has a configuration in which a light diffusing plate 15, an optical element sheet 16, and a light diffusing sheet 17 are sequentially laminated from the light source unit 11 side toward the display panel 2 side. Of the optical sheet 12, the light source 11 side is the light incident side, the display panel 2 side is the light emission side, the lower surface 15a of the light diffusion plate 15 is the light incident surface, and the upper surface 17a of the light diffusion sheet 17 is the light emission surface. It has become.

  The light diffusing plate 15 and the light diffusing sheet 17 are optical members that adjust the illuminance distribution of the light by diffusing the light from the light source unit 11, and are provided in a rectangular shape in plan view. The light diffusing plate 15 and the light diffusing sheet 17 are configured to have a transparent resin and transparent particles dispersed in the transparent resin, and the refractive index of these transparent resins is different from the refractive index of the transparent particles. There must be. The difference between the refractive index of the transparent resin and the refractive index of the transparent particles is preferably 0.02 or more. This is because if the difference in refractive index is smaller than this, sufficient light scattering performance cannot be obtained. The difference in refractive index is preferably 0.5 or less. Since the light diffusing plate 15 and the light diffusing sheet 17 need to transmit the light incident on the light diffusing plate while being scattered, the average particle diameter of the transparent particles contained in the light diffusing plate 15 and the light diffusing sheet 17 is The average particle size is desirably 0.5 to 10.0 μm, and more preferably 1.0 to 5.0 μm. The transparent particles may have a structure having fine cavities containing air in the transparent resin, that is, a structure in which diffusion performance is obtained by a difference in refractive index between the transparent resin and air. Examples of the transparent resin include polycarbonate resin, acrylic resin, fluorine acrylic resin, silicone acrylic resin, epoxy acrylate resin, polystyrene resin, cycloolefin polymer, methylstyrene resin, fluorene resin, PET, polypropylene, and acrylonitrile styrene. A polymer etc. can be used.

  The optical element sheet 16 has a configuration in which a plurality of optical elements 16b are arranged on a base sheet 16a provided in a rectangular shape in plan view, and a plurality of optical element sheets 16 are provided between the light incident surface 15a and the light emitting surface 17a. It has been. In FIG. 1, two optical element sheets 16 are stacked. However, for example, a configuration in which three or more optical element sheets 16 are stacked may be used.

  As the base sheet 16a, plastic sheets such as polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polymethyl methacrylate (PMMA), polyethylene (PE) and the like well known in the art can be used. Used. The refractive index of these sheets is in the range of 1.50 ± 0.5, for example.

  As the optical element 16b, as shown in FIG. 17, a lens having a radius of curvature Rt of the apex that is fitted within a range of 10% of the pitch width P in a cross-sectional view has a value of 10% or more of the pitch width P. In this embodiment, a lens-shaped optical element is used. The specific shape may be a pattern in which lenses are arranged in an array in one direction or a dot pattern such as a microlens. FIG. 1 shows a pattern in which lenses are arranged in an array. In the drawing, for convenience, the optical element sheets 16 are shown to be laminated so that the extending direction of the lens pattern is the same. However, when a pattern that is actually arranged in an array is used, The optical element sheets 16 are laminated so that the extending directions intersect (or orthogonal).

  In all the optical element sheets 16 except the optical element sheet 16 arranged at the position farthest from the light source unit 11, the material of the optical element 16b is a resin whose cured material has a Young's modulus E ′ of 200 MPa to 3000 MPa. Is used. Examples of such resins include 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. Radiation curable resin, or thermosetting resin such as acrylonitrile styrene copolymer resin, phenol resin, melamine resin, urea resin, alkyd resin, or thermoplastic resin such as propylene resin, polyethylene terephthalate resin, polyacetal resin Etc.

  However, the Young's modulus of the cured product of these resins can also vary depending on the conditions for curing the resin. For example, in the case of a UV curable resin, if the UV irradiation amount during curing is small, the Young's modulus decreases due to insufficient curing of the resin, and conversely, if it is large, the Young's modulus tends to increase. Therefore, it is necessary to find the optimum curing conditions and cure the resin so that the Young's modulus of the cured resin is applicable to the above-described conditions. The refractive index of the cured product of these resins is 1.50 ± 0.5 regardless of the curing conditions.

  As a pattern forming method for the optical element 16b, a roll-shaped mold 43 having a concavo-convex inverted mold formed on the surface of a base sheet 16a coated with a thermosetting, thermoplastic or radiation curable resin 41 is used. The resin 41 coated on the surface of the base material sheet 16a is cured by cooling, heating, or radiation irradiation 42 through the base material sheet 16a while pressing the resin application side to the optical material having the desired uneven shape. The method of forming the pattern of the element 16b on the surface of the base material sheet 16a is mentioned (refer FIG. 18).

  When the pattern of the optical element 16b is molded, the pattern of the optical element 16b and the base sheet 16a may be formed at once by an extrusion molding method, an injection molding method, or the like. The conditions such as the Young's modulus and the curvature radius of the top described above correspond to all the optical element sheets except the optical element sheet provided at the position farthest from the backlight, and the optical element sheet located on the outermost side. There is no need to define the Young's modulus of the optical element and the curvature radius of the apex.

  The light diffusing plate 15, the optical element sheet 16, and the light diffusing sheet 17 have substantially the same dimensions in plan view, and are arranged so that the positions in plan view overlap. The support member 18 supports one set (for example, the side located in the left-right direction in the drawing) of the two opposing sides of the light diffusion plate 15, the optical element sheet 16, and the light diffusion sheet 17.

  Examples of the material constituting the support member 18 include metals and resins. A material that is not deformed by light from the light source unit 11 and heat generated by the light source unit 11 or the display panel 2 is preferable. When the optical element sheet 16 is made of a thermosetting resin, a thermoplastic resin, or a radiation curable resin, the optical element sheet 16 may be polymerized and bonded to the support member 18, or the support member 18 may be attached to the optical element sheet 16. The structure integrally molded as the same member which consists of the same material may be sufficient. In addition, examples of the support member 18 include a pressure-sensitive adhesive, an adhesive, a welding method, a method using a fixing tool, and a method for performing room temperature bonding by irradiating an excimer.

  Examples of the pressure-sensitive adhesive and adhesive include acrylic-based, urethane-based, rubber-based, and silicone-based pressure-sensitive adhesives and adhesives. In any case, since it is used in a high-temperature backlight, it is desirable that the storage elastic modulus G ′ is 10 MPa or more at 100 ° C. If the value is lower than this, the support member 18 may be peeled off during use. The pressure-sensitive adhesive or adhesive may be a double-sided tape or a single layer. As a method of applying an adhesive or an adhesive, various coating apparatuses such as a comma coater, a printing method, a method using a dispenser or a spray, or manual coating using a brush or the like may be used.

  When using the technique of welding, the method of using a heat | fever, an ultrasonic wave, or a laser is mentioned, for example. These methods are easy to process and are suitable for joining outside the display area. In the case where welding is performed by laser irradiation, for example, a method in which a portion outside the display area near the four corners of the optical sheet 12, a side surface of the optical sheet 12, or the like is melted and welded by, for example, a carbon dioxide laser.

  In the case of using a fixing tool, examples of the fixing tool include resin and metal molded into the shape of the support member 18, a metal stopper, a stapler, a tape, rubber, a clip, and the like. Environmentally friendly materials such as biodegradable plastics and materials containing cellulose such as paper and wood may be used.

  The resin or metal stopper molded as the support member 18 may be integrated with the backlight casing. These methods are easier to process than welding, and are suitable for joining outside the display area. When the optical sheet 12 is fixed using the support member 18, a positioning opening is provided in advance in the light diffusion sheet 17, the optical element sheet 16, and the light diffusion plate 15, and a pin that penetrates the support member 18 through the opening. By providing the optical sheet 12, the optical sheet 12 can be easily assembled. If there are a plurality of pins on the support member 18, the positional accuracy is further improved.

  In the case of using a method in which the excimer is bonded at room temperature by irradiation as the support member 18, after irradiating one or both of the two materials to be bonded with the 178 nm excimer UV, the two materials are laminated. Heat may be applied during lamination, or heat may be applied after lamination.

  As described above, according to the present embodiment, an excellent light collecting and diffusing function can be obtained by laminating a plurality of optical element sheets 16, so that high brightness, high display quality, and power saving can be realized. It becomes possible. In addition, the curvature radius of the top of the cross-sectional shape of the optical element sheet 16 for all the optical element sheets 16 except the optical element sheet 16 provided at the position farthest from the light source unit 11 among the laminated optical element sheets 16. It is possible to prevent the optical element 16b from being lost and to regulate the Young's modulus of the optical element sheet 16 to prevent the optical element sheet 16 from being crushed. As a result, high brightness, high display quality, and power saving can be realized, and a clear display image can be obtained.

The technical scope of the present invention is not limited to the above-described embodiment, and appropriate modifications can be made without departing from the spirit of the present invention.
For example, as shown in FIG. 2, the configuration of the optical sheet 12 is such that the light diffusing plate 15, two optical element sheets 16, and the light diffusing sheet 17 are stacked in order from the backlight unit 3 side and fixed by the support member 18. The optical element sheet 16 may be configured to use a prism as the optical element 16b of the optical element sheet 16 (hereinafter, such an optical element sheet is referred to as “prism sheet 16”). In this configuration, the prism sheets 16P are laminated so that the prism patterns are orthogonal.

  Further, as shown in FIG. 3, in order from the backlight unit 3 side, an optical element sheet using lenses as the light diffusion plate 15 and the optical element 16b (hereinafter, such an optical element sheet is referred to as “lens sheet 16”). The optical sheet 12 may be assembled by laminating 16L, the prism sheet 16P, and the light diffusion sheet 17 one by one and fixing them with the support member 18. The lens sheet 16L and the prism sheet 16P are laminated so that the extending directions of the patterns are orthogonal to each other. The lens sheet 16L and the prism sheet 16P may be stacked in the reverse order.

  In addition, as shown in FIG. 4, in the order from the backlight unit 3 side, two optical diffusion plates 15, two prism sheets 16 </ b> P, and a light diffusion sheet 17 are stacked and fixed by a support member 18, and assembled. It does not matter. Here, the prism sheets 16P on the backlight unit 3 side are reversed in direction and are laminated so that the extending directions of the patterns of the optical elements 16b are orthogonal to each other in the form of contacting the respective base material sheets. As shown in FIG. 5, a lens sheet 16L may be used instead of the prism sheet 16P.

  Further, as shown in FIG. 6, the light diffusion plate 15, the optical element sheet 16 </ b> L, the prism sheet 16 </ b> P, and the light diffusion sheet 17 are stacked one by one in order from the backlight unit 3 side, and fixed and assembled by the support member 18. The optical sheet 12 may be used. In the configuration shown in the figure, the configuration of the optical element 16b used in the optical element sheet 16L is a shape that is asymmetric in the cross section when viewed in the direction in which the array extends, and the direction in which each optical element 16b extends. Are stacked so as to be orthogonal to each other. In this configuration, a lens sheet 16L may be used instead of the prism sheet 16P.

  7, in order from the backlight unit 3 side, the light diffusion plate 15, the lens sheet 16L provided with the light reflection layer 19, the lens sheet 16L provided with no light reflection layer 19, and the light diffusion sheet. Alternatively, the optical sheet 12 may be assembled by stacking 17 pieces one by one and fixing them with the support member 18. The lens sheet 16L provided with the light reflecting layer 19 and the lens sheet 16L are laminated so that the extending directions of the optical elements (lenses) are orthogonal to each other. A prism sheet 16P may be used instead of the lens sheet 16L.

  In this case, it is preferable to provide the light reflection layer 19 on the incident surface side of the optical element sheets 16L and 16P. When the light reflecting layer 19 is provided, it is preferable to use a white pigment and a metal vapor deposition layer and to select a material having high reflectance and low light absorption. For example, a transparent resin such as acrylic resin in which white fine particles such as titanium dioxide, alumina, calcium carbonate, zinc white, lead white, and lithopone are dispersed and solidified, or white ink may be employed. . The reflectance of the light reflecting layer 19 is preferably a high reflectance of 83% or more, more preferably 90% or more so that the light can be reflected on the back side and reused as illumination light. preferable.

  The light reflecting layer 19 can also be formed by a transfer method using a UV curable adhesive material. A UV curable adhesive material is bonded in advance to the surface opposite to the optical element 16b, and UV light is irradiated from the optical element 16b side to cure the condensing portion of the optical element 16b of the adhesive material. And a pattern in which uncured portions are alternately arranged. Thereafter, the light reflecting layer is bonded to the surface of the adhesive material and peeled off, so that the light reflecting layer can be left only in the uncured portion of the adhesive material, and a light reflecting layer pattern synchronized with the pattern of the optical element 16b is completed. . With this method, the optical element 16b and the light reflecting layer can be easily arranged in a 1: 1 correspondence.

    The light reflecting layer 19 is formed by integrating and molding the optical element 16b, the base sheet 16a on the exit surface side, and a lens sheet having irregularities on the other surface by extrusion or injection molding. It can also be made by a method of applying an ink showing light reflectivity in a pattern.

  Further, as shown in FIG. 8, the light diffusion plate 15, the lens sheet 16 </ b> L with the light reflection layer 19, the prism sheet 16 </ b> P, and the light diffusion sheet 17 are laminated one by one in order from the backlight unit 3 side. The optical sheet 12 may be fixed and assembled by the above. The lens sheet 16L with the light reflection layer 19 has a concave portion on the light incident surface side in a lens shape, and is laminated so that the extending directions of the optical elements are orthogonal to each other. A lens sheet 16L may be used instead of the prism sheet 16P.

  Further, as shown in FIG. 9, the light diffusion plate 15, the lens sheet 16 </ b> L, the prism sheet 16 </ b> P, and the light diffusion sheet 17 are stacked one by one in order from the backlight unit 3 side, and fixed and assembled by the support member 18. The optical sheet 12 may be used. The lens sheet 16L is provided with a lens array on the light incident surface side, and is laminated so that the extending directions of the optical elements are orthogonal to each other. A lens sheet may be used instead of the prism sheet 16P.

  Further, as shown in FIG. 10, the light diffusion plate 15, the lens sheet 16 </ b> L, the lens sheet 16 </ b> L with the light reflection layer 19, and the light diffusion sheet 17 are laminated one by one in order from the backlight unit 3 side. The optical sheet 12 may be fixed and assembled by the above. The lens sheet 16L with the light reflecting layer 19 is provided with the light reflecting layer 19 on the top of the lens, and is laminated so that the extending direction of each optical element is orthogonal to the lens sheet 16L on the light source side. ing. A prism sheet may be used instead of the lens sheet 16L on the light source side.

  Further, as shown in FIGS. 11, 12, and 13, the light diffusion plate 15, the lens sheet 16 </ b> L, the lens sheet 16 </ b> L provided with the light diffusion particles 20, and the light diffusion sheet 17 are sequentially provided from the backlight unit 3 side. The optical sheets 12 may be laminated one by one and fixed and assembled by the support member 18. The lens sheet 16L with the light diffusing particles 20 is obtained by providing fine particles of transparent resin as the light diffusing particles 20 inside the lens sheet, and the extending direction of each optical element is orthogonal to the lens sheet 16L on the light source side. Are stacked. 11 is a diagram using a sheet in which the light diffusing particles 20 are provided only inside the lens 16b, and FIG. 12 is a diagram using a sheet in which the light diffusing particles 20 are provided only inside the base material sheet 16a. These are figures using the sheet | seat which provided the light-diffusion particle | grains 20 in the inside of both the lens 16b and the base material sheet | seat 16a. A prism sheet may be used instead of the lens sheet 16L on the light source side. Examples of transparent resins include polycarbonate resin, acrylic resin, fluorine-based acrylic resin, silicone-based acrylic resin, epoxy acrylate resin, polystyrene resin, cycloolefin polymer, methylstyrene resin, fluorene resin, PET, polypropylene, etc. If the refractive index of the lens 92 is M and the refractive index of the light diffusing particle 20 is N, it is desirable that the refractive index difference between the two satisfies the relationship of | M−N | ≧ 0.01. This is because if the difference in refractive index between the two is less than 0.01, sufficient light diffusibility cannot be obtained.

  Further, as shown in FIG. 14, the light diffusion plate 15, the lens sheet 16 </ b> L with the light reflection layer 19, the lens sheet 16 </ b> L, and the light diffusion sheet 17 are stacked one by one in order from the backlight unit 3 side. The optical sheet 12 may be fixed and assembled by the above. The lens sheet 16L with the light reflecting layer 19 is provided with the light reflecting layer 19 in the gap of the lens array so that the extending direction of each optical element is orthogonal to the lens sheet 16L on the display panel 2 side. Are stacked. A prism sheet may be used instead of the lens sheet 16L on the liquid crystal panel 90 side.

  Further, as shown in FIG. 15, the optical sheet 12 is assembled by laminating two light diffusion plates 15, a lens sheet 16 </ b> L, and a light diffusion sheet 17 in order from the backlight unit 3 side, and fixing with a support member 18. It does not matter. The lens sheet 16L on the display panel 2 side is a sheet when the lens height differs depending on the array, and the extending direction of each optical element is orthogonal to the lens sheet 16L on the light source unit 11 side. Are stacked. A prism sheet may be used instead of the lens sheet 16L on the light source unit 11 side.

  Further, as shown in FIG. 16, the light diffusion plate 15, the lens sheet 16 </ b> L, the lens sheet 16 </ b> L with the light reflection layer 19, and the light diffusion sheet 17 are stacked one by one in order from the backlight unit 3 side, and the support member 18. The optical sheet 12 may be fixed and assembled by the above. The lens sheet 16L with the light reflection layer 19 is a sheet when the light incident surface is uneven and the light reflection layer 19 is provided in the recess, and each lens sheet 16L is provided between the lens sheet 16L on the light source unit 11 side. The optical elements are stacked so that the extending directions thereof are orthogonal to each other. A prism sheet may be used instead of the lens sheet 16L on the light source unit 11 side.

  1 to 16, in the optical element sheet 16 on the light source unit 11 side among the optical element sheets 16 laminated in plural, the Young's modulus E ′ of the optical element 16 b and the curvature radius Rt of the top part are set. It is defined as described in the above embodiment.

  In this example, an optical sheet having the configuration shown in FIG. 1 was prepared. First, a UV curable acrylic resin for forming an optical element pattern is applied on the surface of a PET sheet of a 75 μm-thick base sheet, and the resin is applied to a roll-shaped mold having an uneven shape on the surface. While the application side was pressed, UV irradiation was performed through the substrate sheet, the resin applied on the surface of the PET sheet was cured, and an optical element having the desired uneven shape was formed on the sheet surface.

  The optical elements 16b in the present example are all lenticular lens arrays in which the pitch width P is 140 μm, the height is 76 μm, and semi-cylindrical cylindrical lens groups are arranged in parallel in one direction. In addition, a lens sheet 16L having a shape in which the curvature radius Rt of the top portion fitted within the range of 10% of the lens pitch width P in the lens cross section, that is, 14 μm, was varied from 0 μm to 50 μm was prepared. The lens has a prism shape when the curvature radius Rt is 0 to 10 μm, and a lens shape when the curvature radius Rt is 11 to 50 μm. Note that Rt of 0 μm means a prism shape with a completely sharp apex.

  Further, the lens sheet 16L having various Young's moduli was prepared by changing the curing conditions greatly to change the degree of curing of the resin variously. The Young's modulus E 'was measured using a micro hardness meter (Nano Indenter) after making a cross section perpendicular to the direction in which the lens extends with a microtome. The indentation depth was 500 nm, and the Young's modulus was calculated from the unloading curve at this time. The measurement was performed 6 times for each sample, and an average value was taken.

  The light diffusion plate 15 and the two lens sheets 16L prepared in this example were laminated in this order from the backlight 97 side, and the light diffusion sheet 17 was laminated in that order, and incorporated in a display device, and a vibration test was performed. The test method is that a display device incorporating the optical sheet 98 is placed on a test machine, the conditions are a frequency of 5 to 50 Hz, an acceleration of 1.0 G, and 20 minutes in the x direction (direction parallel to the short side of the lens sheet), the y direction. After testing for 20 minutes (in the direction parallel to the long side of the lens sheet) and 70 minutes in the z direction (thickness direction of the lens sheet), the presence or absence of unevenness in the displayed image was visually observed.

  Two light diffusion plates 15 and two lens sheets 16L prepared in this embodiment were laminated in this order from the backlight 97 side, and the light diffusion sheet 17 was laminated in that order, and incorporated in a display device, and a lighting test was performed. In the test method, after the backlight of the display device incorporating the optical sheet 98 was turned on for 200 hours, the presence or absence of unevenness in the displayed image was visually observed.

  From the results shown in Table 1, when the radius of curvature Rt at the top of the lens 92 is 14 μm or more and the Young's modulus E ′ is 200 MPa or more and 3000 MPa or less, the lens surface is not crushed and no defect occurs, and the lens is clear. It is possible to provide an optical sheet, a backlight unit, and a display device that are advantageous in obtaining a stable display image. In this embodiment, the curvature radius Rt at the top of the lens was increased to a maximum of 50 μm, and verification was performed. In the present invention, the radius of curvature Rt is set to 14 μm or more, that is, Rt ≧ 0.1P (10% of the lens pitch width P = 14 μm).

  Next, the light diffusion plate from the backlight side, the two lens sheets 16L created in this example, and the light diffusion sheet 17 are laminated in this order, incorporated into the display device, using a luminance measuring machine, And the half-value angle in the horizontal direction was measured. Regarding the front luminance, the luminance of BEFIII of 3M company was measured as a reference, and expressed as a ratio when the value was 1. In addition, measurement was performed when only one lens sheet 16L was incorporated, and the improvement in optical characteristics was also confirmed when two or more lens sheets 16 were incorporated.

  From the results shown below, it was confirmed that the front brightness and the viewing angle were greatly improved by laminating two or more lens sheets 16L. For the luminance measurement, a lens sheet 16L having a radius of curvature of 0.7 mm and a Young's modulus of 2000 MPa was used. This time, we measured the brightness in the case of only one sheet and two patterns when two sheets were stacked, but we hope to further improve the optical characteristics by stacking three or more lens sheets as necessary. You can also.

  In addition, this time, verification was performed only for lenses having a pitch width of 140 μm and a height of 76 μm, but the same tendency was observed for lenses having other pitch widths and heights, prisms, and microlenses. Can be expected.

Moreover, the optical sheet and display device used this time are examples, and are not limited to the configuration according to the present invention.
As described above, according to the present invention, by providing a configuration in which at least two optical element sheets for improving luminance are laminated in part, it has an excellent light collecting and diffusing function, and has high luminance and high luminance. Provide optical sheets with display quality and low power consumption. Of the optical element sheets laminated two or more, the surface of all optical element sheets except the optical element sheet provided at the position farthest from the backlight. It is possible to provide an optical sheet, a backlight unit for display, and a display device that are advantageous in preventing defects and shape collapse and obtaining a clear display image.

Explanatory drawing which shows an example of the optical sheet and liquid crystal display device which concern on this invention. Explanatory drawing which shows an example of the optical sheet and liquid crystal display device which concern on this invention. Explanatory drawing which shows an example of the optical sheet and liquid crystal display device which concern on this invention. Explanatory drawing which shows an example of the optical sheet and liquid crystal display device which concern on this invention. Explanatory drawing which shows an example of the optical sheet and liquid crystal display device which concern on this invention. Explanatory drawing which shows an example of the optical sheet and liquid crystal display device which concern on this invention. Explanatory drawing which shows an example of the optical sheet and liquid crystal display device which concern on this invention. The side view which shows the manufacturing process of an optical element sheet | seat. Explanatory drawing which shows an example of the optical sheet and liquid crystal display device which concern on this invention. Explanatory drawing which shows an example of the optical sheet and liquid crystal display device which concern on this invention. Explanatory drawing which shows an example of the optical sheet and liquid crystal display device which concern on this invention. Explanatory drawing which shows an example of the optical sheet and liquid crystal display device which concern on this invention. Explanatory drawing which shows an example of the optical sheet and liquid crystal display device which concern on this invention. Explanatory drawing which shows an example of the optical sheet and liquid crystal display device which concern on this invention. Explanatory drawing which shows an example of the optical sheet and liquid crystal display device which concern on this invention. Explanatory drawing which shows an example of the optical sheet and liquid crystal display device which concern on this invention. Explanatory drawing which shows the fitting curvature radius Rt of the top part of an optical element. The side view which shows the manufacturing process of an optical element sheet | seat. Explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. Explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. Explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. Explanatory drawing which shows the perspective view of BEF by a prior art. Explanatory drawing which shows the structural example of the optical sheet for liquid crystal displays by a prior art. Explanatory drawing which shows light intensity distribution radiate | emitted from the optical sheet using BEF. Explanatory drawing which shows the optical sheet which concerns on another type of prior art from BEF. Explanatory drawing which shows the optical sheet and liquid crystal display device which laminated | stacked and comprised BEF. Explanatory drawing which shows the optical sheet and liquid crystal display device which laminated | stacked and comprised the lens sheet of a different type from BEF. The solid explanatory drawing which shows a mode that the optical element sheet | seat was made to go straight and was laminated | stacked. The figure which shows a mode that a defect | deletion arises on the surface of BEF. The figure which shows a mode that a crushing arises on the lens surface of a lens sheet.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Display apparatus 2 ... Display panel 3 ... Backlight unit 11 ... Light source part 12 ... Optical sheet 13 ... Light source 14 ... Light reflecting plate 15 ... Light diffusing plate 15a ... Light incident surface 16 ... Optical element sheet 16a ... Base material sheet 16b Optical element 16P Prism sheet 16L Lens sheet 17 Light diffusing sheet 17a Light exit surface 18 Support member 19 Light reflecting layer 20 Light diffusing particles

Claims (17)

An optical sheet that converges or equalizes light from a light source,
A light incident surface on which light from the light source is incident;
A light exit surface that is provided on a surface opposite to the light incident surface and emits light from the light incident surface;
A plurality of laminated layers between the light incident surface and the light exit surface, and a convex shape that controls at least one of a traveling direction, an exit range, a wavelength component, and a luminance distribution of the light emitted from the light exit surface. An optical element layer having an optical element,
For all the optical element layers except the optical element layer provided at the position farthest from the light source among the plurality of optical element layers,
When the formation pitch width of the optical element layer is P, and the curvature radius of the top part fitted in the range where the width is 0.1 P in the cross-sectional view of the optical element layer is Rt, the fitting curvature of the top part is Rt. Radius Rt is
Rt ≧ 0.1P
Satisfied, and
The Young's modulus E ′ of the optical element layer at room temperature is
200 ≦ E ′ ≦ 3000
An optical sheet characterized by satisfying The plurality of optical element layers are each provided in a rectangular shape in plan view, and are arranged at positions where each overlaps in plan view,
The optical sheet according to claim 1, further comprising a support member that supports at least one set of two sets of opposing sides of the optical element layer. The optical sheet according to claim 2, wherein the support member supports all of two opposing sides of the optical element layer. The optical sheet according to claim 2, wherein the support member is made of metal. The optical sheet according to claim 2, wherein the support member is made of a resin. The optical element layer is made of a thermosetting resin, a thermoplastic resin or a radiation curable resin,
The optical sheet according to any one of claims 2 to 5, wherein the optical element layer is polymerized and bonded to the support member. The optical element layer is made of a thermosetting resin, a thermoplastic resin or a radiation curable resin,
The optical sheet according to any one of claims 2 to 5, wherein the optical element layer is the same member as the support member. The optical sheet according to any one of claims 1 to 7, wherein the optical element includes at least one of a prism and a lens. The optical sheet according to any one of claims 1 to 8, wherein a light reflection layer is provided on the optical element layer. The optical sheet according to claim 9, wherein the light reflecting layer is provided on the light incident surface side of the optical element layer. The optical sheet according to claim 9, wherein the light reflecting layer is provided on the light emitting surface side of the optical element layer. The optical sheet according to any one of claims 9 to 11, wherein the light reflection layer is provided between the plurality of optical element layers. The optical element layer has a plurality of the optical elements,
The optical sheet according to claim 9 or 10, wherein the light reflection layer is provided between the plurality of optical elements in a plan view. The optical sheet according to any one of claims 1 to 13, wherein a light diffusion portion is provided inside the optical element. The optical sheet according to any one of claims 1 to 14,
A backlight unit comprising: a light source that irradiates light to the light incident surface of the optical sheet. The backlight unit according to claim 15;
A display device, comprising: a display panel that is provided on the light exit surface side of the optical sheet in the backlight unit and performs display using light emitted from the light exit surface. The display device according to claim 16, wherein the light source includes at least one of a cold cathode fluorescent lamp, an LED, an EL, and a semiconductor laser.

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