JP2010107934A - Optical sheet for dimming back light, back light unit and display incorporating the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a back light dimming optical sheet, a back light unit, and a display incorporating it, that can reduce uneven brightness between light sources still more in a back light dimming optical sheet incorporating a brightness control member and a reflective layer using a method of integrating the brightness control member of a repetitive array structure and a diffusion layer without changing the shape (volume) of the air layer between them. <P>SOLUTION: The back light dimming optical sheet has a diffusion layer to diffuse the light from the light source, a brightness control member having the repetitive array structure of the lenses arranged on this diffusion layer at its diffused light outputting side, and a reflector having an aperture regulating the range of the light incident angles to each lens of the brightness control member formed between the diffusion layer and the brightness control member. Further, it has a micro-lens array formed on the diffusion layer at its side facing the light source. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

    The present invention relates to an optical sheet for backlight dimming having a diffusion layer for diffusing light from a light source and a luminance control member, a backlight unit including the same, and a display device.

  A display device that is not a self-luminous type typified by a liquid crystal display device (LCD) incorporates a light source (backlight) in order to display information such as an image. The power consumed by this light source occupies a considerable portion of the power consumed by the entire display device, and in recent years when there is a strong demand for reducing the total power, it is first required to improve the light source utilization efficiency. ing.

  In addition, because the number of light sources is reduced to reduce power consumption and cost, the distance between the light sources becomes longer, and the thickness of the apparatus is further reduced, so that the light source and the optical sheet for backlight dimming can be reduced. Since the distance is very close, there is a second problem in that uneven brightness of the screen is perceived by the viewer.

  As means for improving the utilization efficiency of the light source, displays using a brightness enhancement film (BEF; Brightness Enhancement Film: a registered trademark of 3M Corporation in the United States) are increasing.

  BEF is a film in which unit prisms having a triangular cross section are periodically arranged in one direction on a transparent substrate. This prism is formed in a size (pitch) larger than the wavelength of light. BEF collects light from “off-axis” and redirects this light “on-axis” to the viewer, or “recycle”. " Therefore, when using the display (when observing), off-axis rays from the light source can be condensed by the BEF and redirected to increase the on-axis luminance.

  Note that “on the axis” is a direction that coincides with the visual direction of the user, and is generally a normal direction to the display screen.

  In BEF, when a repetitive array structure of prisms is arranged in only one direction, it is only possible to redirect or recycle light in that arrangement direction. Therefore, in order to control the luminance of the display light in the horizontal direction on the horizontal plane and in the vertical direction perpendicular thereto, the two BEFs may be used in combination so that the arrangement directions of the prism groups are substantially orthogonal to each other. . Thus, by adopting BEF, a desired on-axis brightness can be achieved while reducing power consumption.

  The use of a luminance control member having a repetitive array structure of prisms typified by BEF as an optical sheet for backlight dimming for a display device or the like is disclosed in many patent documents (for example, Patent Documents 1 to 1). 3).

  For example, in an edge light type display device that uses BEF as a brightness control member for an optical sheet for backlight dimming, light from the light source is emitted from the inclined surface of the prism. The light is emitted in a certain angle range controlled as the center of the light. Since the emitted light is controlled in this way, the intensity of light in the visual direction of the user is increased.

  However, at the same time, there is a light component that is reflected at one inclined surface of the prism and refracted at the other inclined surface, and is emitted wastefully in the lateral direction without proceeding to the visual direction of the user. there were.

  FIG. 3 is a diagram showing a luminance distribution with respect to a viewing angle in the display device. The vertical axis represents the light intensity, and the horizontal axis represents the viewing angle of the user centered on the on-axis.

  A broken line B in FIG. 3 is a light intensity distribution for a display device including only the above-described BEF (prism sheet) as an optical sheet for backlight dimming. As indicated by a broken line B, in the BEF, the light intensity at the angle 0 ° in the user's visual direction F (on-axis direction) is the highest, and the light emission angle from the screen with respect to the visual direction F is horizontal. The light intensity gradually decreases symmetrically in both directions (−90 °, + 90 °). At an emission angle near ± 90 ° that coincides with the horizontal axis, sidelobe light deviating from the viewing direction is shown as a small light intensity peak. Since the sidelobe light deviates from the observer's field of view, it is unnecessarily emitted from the lateral direction of the prism. That is, BEF has a problem that there is this useless light. If possible, a smooth luminance distribution shown as a substantially normal distribution curve with a solid line A in FIG. 3 having no light intensity peak due to sidelobe light around ± 90 ° is preferable.

  In general, a configuration is widely used in which two prism sheets are used in such a manner that one prism row and the other prism row are substantially orthogonal to each other. In this way, it is possible to collect light in the direction of angle 0 ° of the user's viewing angle direction F with respect to light incident in parallel to one prism row, and it is possible to improve the light utilization efficiency. become.

  On the other hand, when only the on-axis luminance increases excessively, the peak width of the curve in FIG. 3 becomes extremely narrow, and the viewing area is extremely limited. In order to appropriately widen the peak width, it is conceivable to additionally provide a light diffusion member (diffusion layer) to the optical sheet for backlight light control. However, the effect of reducing the sidelobe light cannot be obtained, and it cannot be said that the light use efficiency is high.

  In order to overcome such drawbacks, an air layer formed at the interface between a brightness control member such as BEF and a diffusion layer is known. By utilizing interfacial refraction in the air layer, light that has once diffused in the diffusion layer is collected again at the center with a large incident angle on the lens, which can improve the central luminance. it can. However, when integrating the brightness control member and the diffusion layer, it is difficult to hold the shape (volume) of the air layer without deformation.

  In order to solve this problem, a configuration is disclosed in which a light reflection layer having an opening is used as a spacer between the luminance control member and the diffusion layer, and the opening between the reflection layers is formed as an air layer. In this configuration, the shape of the air layer can be kept constant by bonding the diffusion layer and the luminance control member through a bonding material such as an adhesive or an adhesive. (See Patent Document 4).

  The above-mentioned method can considerably improve the utilization efficiency of the light source, and has recently been adopted in many liquid crystal displays and the like as a solution to the first problem. However, the above method solves another problem, that is, the unevenness of light and darkness between light sources that appears on the screen to the extent that the user perceives it, even though a diffusion layer is provided. Is difficult.

Japanese Patent Publication No. 1-378001 JP-A-6-102506 Japanese National Patent Publication No. 10-506500 JP 2007-057871 A

  An object of the present invention is to integrate the brightness control member having a repetitive array structure and the diffusion layer without changing the shape (volume) of the air layer at the interface between them. In the backlight light control optical sheet having the brightness control member and the reflective layer, the backlight light control optical sheet capable of reducing uneven brightness between the light sources and the backlight unit including the same It is to provide a display device.

  In order to solve the above problems, the invention according to claim 1 of the present invention comprises a diffusion layer for diffusing light from a light source, and a repetitive array structure of lenses arranged on the diffusion light emission side of the diffusion layer. A brightness control member having a reflection portion having an opening that restricts an incident angle range of light with respect to each lens of the brightness control member formed between the diffusion layer and the brightness control member. An optical sheet for light dimming, wherein a microlens array is formed on a light source side surface of the diffusion layer.

  The invention according to claim 2 of the present invention includes a diffusion layer for diffusing light from a light source, a luminance control member having a repetitive array structure of lenses arranged on the diffusion light emission side of the diffusion layer, and the diffusion layer. A backlight dimming optical sheet having a reflection part having an opening that regulates an incident angle range of light with respect to each lens of the brightness control member formed between the brightness control members, An optical sheet for backlight dimming, wherein a microlens array sheet in which a microlens array is formed is integrated on the light source side surface of the diffusion layer via an adhesive layer.

  The invention according to claim 3 of the present invention is characterized in that the microlens array sheet is composed of a transparent base film and a microlens array formed thereon. It is a sheet.

  According to a fourth aspect of the present invention, the microlens array sheet comprises a transparent base film and a microlens array formed thereon, and the transparent base film and the microlens array are made of the same material. The backlight light-modulating optical sheet according to claim 2, wherein the optical sheet is formed simultaneously.

  According to a fifth aspect of the present invention, in the microlens array, microlenses made of a cured product of an ionizing radiation curable resin composition are densely arranged, and the shape of each microlens is a part of a spherical surface. The diameter L of the bottom is 40 μm to 50 μm, the height is 10 μm to 200 μm, and the ratio of the curvature radius r of the spherical surface of the top to the diameter L of the bottom (r / L) is 0.05 to It is 0.4, It is an optical sheet for backlight light control of any one of Claims 1-4 characterized by the above-mentioned.

The invention according to claim 6 of the present invention is characterized in that light diffusing fine particles having a particle diameter of 10 μm or less are added to the microlens array at a ratio of 10 wt% to 30 wt%. The optical sheet for backlight light control described in 1.

  The invention relating to claim 7 of the present invention is the optical sheet for backlight dimming according to claim 1, characterized in that the base material on the light incident side and the exit side are equal.

  The invention according to claim 8 of the present invention is a backlight unit comprising the optical sheet for backlight dimming according to any one of claims 1 to 7.

  The invention according to claim 9 of the present invention is a display device comprising the backlight unit according to claim 7.

  According to the configuration of the first or second aspect, the brightness control member and the diffusion layer are integrated, and the light from the light source is scattered by the microlens array unit, and further scattered by the diffusion layer, thereby causing uneven brightness of the light source (brightness) Unevenness can be reduced.

  Further, since there is an air layer between the brightness control member and the diffusion layer for the light diffused by the diffusion layer, a desired refractive effect can be obtained. That is, when the light diffused in the diffusion layer passes through the air layer and enters the lens unit, the emission angle is controlled to ± 40 ° due to the difference in refractive index, and then the light is condensed by passing through the lens unit. . Therefore, an optical sheet for backlight dimming excellent in light utilization efficiency can be obtained.

  The effect of claim 5 is that the microlens array has a structure in which microlenses made of a cured product of an ionizing radiation curable resin composition are closely arranged, and the shape of each microlens has a top part of a spherical surface. None, the bottom diameter L is 40 μm to 50 μm, the height is 10 μm to 200 μm, and the ratio of the radius of curvature r of the top spherical surface to the bottom diameter L (r / L) is 0.05 to 0. .4. With this shape, the desired shape can be obtained, and the reproducibility of the shape of the mold is good, and the disadvantage that the tip of the protrusion is easily applied to the microlens having the normal shape can be solved.

The effect of claim 6 is that the light-diffusing fine particles are added to the microlens array, so that the brightness of the light source can be made more effective and uniform. When the particle size of the light diffusing fine particles is 10 μm or less, the luminance unevenness can be made extremely uniform.
Moreover, when it is less than 10 wt%, the effect is low, and when it is 10 wt% or more, it is effective. When it is 30 wt% or more, the front luminance is remarkably lowered and it is necessary to be less than 30 wt%.

  The effect of Claim 7 can reduce the curvature of the optical sheet for backlight dimming by the heat from the light source because the base material on the entrance side and the exit side are equal.

It is typical sectional drawing which shows schematic structure of the display apparatus in one Embodiment of this invention, and a backlight unit. It is typical sectional drawing which shows schematic structure of the display apparatus in one Embodiment of this invention, and a backlight unit. It is a graph which shows the light intensity distribution of the transmitted light of the conventional optical sheet for backlight light control, and an ideal intensity distribution. It is a perspective view which shows the detail of the shape of a micro lens sheet and a micro lens.

  Next, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a display device according to an embodiment of the present invention. In FIG. 1, the scale of each layer or each member is appropriately changed so that each layer or each member has a size that can be recognized on the drawing.

  In FIG. 1, a display device 100 according to the present embodiment is an example of the display device according to the present invention, and includes a backlight unit 20, a backlight dimming optical sheet 21 for adjusting backlight light, and a liquid crystal display unit 22. Are stacked in this order. The backlight passes through the backlight dimming optical sheet 21, and the brightness unevenness is reduced and the light use efficiency is improved. The light enters the liquid crystal display unit 22 and is controlled by the image signal. The light is emitted from the liquid crystal display unit 22 upward in the figure. Hereinafter, based on such an arrangement, the upper direction in FIG. 1 may be simply referred to as a display screen side (ejection side), and the lower direction may be simply referred to as a back side.

  The backlight unit 20 and the backlight dimming optical sheet 21 constitute a backlight unit 23 and are an example of the backlight unit of the present invention.

  The backlight unit 20 includes a plurality of light sources 20a in which line-shaped light emitting units extending in the left-right direction on the paper surface are arranged at equal intervals along the depth direction of the paper surface, the light sources 20a are covered from the back side, and the display screen side is opened. A direct-type configuration composed of the reflector 20b is employed.

  However, the backlight unit 20 is not limited to such a configuration as long as white light can be emitted to the back side of the optical sheet 21 for backlight dimming, and a backlight unit having any known configuration may be employed. For example, an edge light type surface light source in which a line light source is arranged on the side surface of the light guide plate may be employed.

  For example, a cold cathode tube or the like can be used as the light source 20a, but an LED light source in which a plurality of LED elements are arranged on a line along the depth direction of the paper surface may be employed.

  The backlight dimming optical sheet 21 condenses part of the light emitted from the backlight unit 20 to the display screen side, transmits the light to the display screen side, and reflects the other light to the backlight unit 20 side. In this case, the microlens array 30, the diffusion layer 7, the bonding layer 6, the reflection unit 5, and the lens unit (optical element unit) 1 are incident on the backlight unit 20 from the back side toward the display screen side. Are stacked in this order. As will be described later, the bonding layer 6 and the lens unit 1 are laminated in this order in the air layer 5a portion formed in the reflection unit 5.

  The diffusion layer 7 is a plate-like member provided at a position that covers the display screen side of the backlight unit 20. The diffusion layer 7 includes a transparent resin and transparent particles dispersed in the transparent resin, and the refractive index of the transparent resin is different from that of the transparent particles. The diffusion layer 7 diffuses the light P emitted from the backlight unit 20 to the display screen side, suppresses uneven brightness in the horizontal direction in the figure due to the plurality of light sources 20a, and appropriately displays the display light with an appropriate viewing angle. Can be granted. As the transparent resin of the diffusion layer 7, for example, PC (polycarbonate) resin, acrylic resin, fluorine acrylic resin, silicone acrylic resin, epoxy acrylate resin, methylstyrene resin, fluorene resin, and the like can be used. .

  In addition, as a method of forming the microlens array 30 on the back surface (light source side) of the diffusion layer 7, there is a method of bonding the microlens array sheet 31 on which the microlens array is formed using an adhesive or an adhesive. Specifically, a method of applying an adhesive or a pressure-sensitive adhesive to the diffusion layer and bonding the microlens array sheet with a laminator can be mentioned. Moreover, after processing an adhesive agent or an adhesive into a dry film form, the method of laminating with a laminator is mentioned.

  Moreover, when it bonds together with an adhesive and an adhesive agent, it is desirable that the adhesive force is 1 kg / inch or more.

  As shown in the perspective view of FIG. 3 (X), the microlens array sheet 31 is formed by arranging a large number of microlenses on the upper surface (= light source side) of the transparent base film 32 as a microlens array 30. It has the convex part 33 made.

  Each microlens has a substantially conical shape, and most of the lower side of the convex portion 33 is formed of a part of a conical shape, but the top portion 34 is rounded, specifically, a spherical shape. Part of it. As illustrated in the perspective view of FIG. 3 (X), the convex portion 33 may be provided on a lattice point of a rectangular lattice, or may be provided on a lattice point of a rhombus lattice. Or as long as it arranges densely, the arrangement which is not regular may be sufficient.

  In the case shown in FIG. 3 (X), the protrusions 33 are formed with a slight gap between them. However, if the gaps are too long, a portion through which light from the light source can pass is formed. It is preferable to narrow. Furthermore, the interval may be narrowed to the extent that there is no planar transparent substrate portion between the convex portions 33.

  FIG. 3Y is a cross-sectional view showing a state in which the convex portion 33 of the microlens is cut along a plane perpendicular to the transparent base film 32 including the top portion thereof. The diameter L of the bottom surface of the convex portion 33 is preferably 40 μm to 50 μm, and this numerical range is comparable to or smaller than the pitch of the electrode matrix of the liquid crystal display element.

  The radius r of the sphere forming the top 34 is preferably determined such that the ratio r / L to the bottom surface diameter L is 0.05 to 0.4. Here, it is not preferable that the ratio r / L is less than 0.05 (when L is 20 μm, 0.05 corresponds to 1 μm), which is difficult in terms of manufacturing accuracy. On the other hand, when the ratio r / L exceeds 0.4, the ratio of the conical slope portion is relatively reduced, which makes it difficult to diffuse incident light in an oblique direction from the light source. Further, it is preferable that the height h of the convex portion 33 is not so high or low as compared with the diameter L of the bottom surface, and the height h is preferably 10 μm to 200 μm.

  In addition, the sphere here refers to a true sphere, a slightly flat shape in which the true sphere is crushed in the vertical direction, and a rugby ball in which the true sphere is extended in the vertical direction. Including. In addition, the boundary between the lowermost part of the slope of the convex portion 33 and the upper surface of the transparent base film 32 of the optical sheet for backlight dimming according to the present invention is drawn linearly in FIG. That is, the vicinity of the boundary is not smoothly continuous, but the boundary vicinity may be a continuous curved surface.

  The convex portions 33 as described above are densely arranged in a large number as described above. If the spacing is too large, the ratio of the flat and non-light diffusing performance will increase, and the light diffusing performance of the entire sheet will decrease, so the gaps between the protrusions 33 will be adjacent to each other, both of the bottom surface It is preferable that the two convex portions 33 having a diameter L are measured between the respective end portions and are about L / 7 or less.

  The number of microlenses is, for example, 47852 / cm2 when the distance between the end portions at the time of arrangement is L / 7, for example, when the bottom diameter is 40 μm, and 30625 / cm2 when the bottom diameter is 50 μm. It becomes.

  In addition, in the case where the gap is formed so that the flat portion of the transparent base material is not exposed between the convex portions 3, as shown in FIG. 3 (Z), as an example, a conical shape of one convex portion. It is preferable that the skirt portion has a shape parallel to a plane passing through the center of the top and bottom of the cone and cut and removed so that the bottom surface becomes a square. At this time, the conical slope portion is reduced and the proportion of the portion of the top spherical surface is relatively large. Therefore, in order to eliminate this point, the maximum value of r / L is set to 0.3. It is preferable to set the degree.

  By intentionally making the tip of the conical protrusion not a pointed shape but a part of the spherical surface, the tip of the protrusion becomes difficult to chip, and the reproducibility of the shape of the protrusion according to the mold is improved. .

  Hereinafter, a method of forming the microlens array sheet 31 on the transparent base film to form the microlens array sheet 31 will be described.

  As a raw material of the transparent base film 32, a material having transparency and smoothness and having no foreign matter mixed therein is preferable, and a material having mechanical strength for processing and product use is preferable.

  Generally preferred as the transparent substrate film 32 are cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, polyester, polyamide, polyimide, polyether sulfone, polysulfone, polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal. , A film of a thermoplastic resin such as polyether ketone, polymethyl methacrylate, polycarbonate, or polyurethane.

  Although these thermoplastic resin films are flexible and easy to use, there is no need to bend them during handling, and when a hard one is desired, plate-like ones such as the above-mentioned resin plates and glass plates can also be used. Can be used. As thickness, about 8-1000 micrometers is preferable and 50-200 micrometers is more preferable. In addition, when it is plate shape, you may exceed this range.

  The transparent substrate film 32 is usually subjected to various treatments that can be performed to improve adhesion to the layer formed on either the upper surface or the lower surface, or both, that is, corona discharge treatment. In addition to physical treatment such as oxidation treatment, a primer layer (not shown) may be formed by previously applying a coating called an anchor agent or primer.

  The microlens array 30 of the present invention basically has a concave portion corresponding to the shape of the protrusion, and preferably a concave portion of a roll-shaped mold filled with an ionizing radiation curable resin composition by ionizing radiation. It is obtained by curing and molding. Although it can be configured by using a thermosetting resin composition, it takes time to cure the thermosetting resin composition on the mold, so the ionizing radiation curable resin can be cured instantaneously. It is preferable to use a composition.

  The ionizing radiation curable resin composition has a high scratch resistance after curing so that the curing speed when forming the convex portion 33 by a casting method using a mold is high and the surface is not damaged during use. What has is preferable. Further, as the ionizing radiation curable resin composition, those having a hardness after curing of “H” or higher in the pencil hardness test shown in JIS K5400 are more preferable.

As an ionizing radiation curable resin composition, a prepolymer, an oligomer, and / or a monomer having a polymerizable unsaturated bond or an epoxy group in a molecule are appropriately mixed.
The ionizing radiation refers to an electromagnetic wave or a charged particle beam having an energy quantum capable of polymerizing or cross-linking molecules, and usually an ultraviolet ray or an electron beam is used.

  Examples of prepolymers and oligomers in the ionizing radiation curable resin composition include unsaturated polyesters such as unsaturated dicarboxylic acid and polyhydric alcohol condensates, polyester methacrylate, polyether methacrylate, polyol methacrylate, melamine methacrylate, etc. Examples include methacrylates, polyester acrylates, epoxy acrylates, urethane acrylates, polyether acrylates, polyol acrylates, acrylates such as melamine acrylate, and cationic polymerization type epoxy compounds.

  Examples of the monomer in the ionizing radiation curable resin composition include styrene monomers such as styrene and α-methylstyrene, methyl acrylate, 2-ethylhexyl acrylate, methoxyethyl acrylate, butoxyethyl acrylate, acrylic acid Acrylic esters such as butyl, methoxybutyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, methoxyethyl methacrylate, ethoxymethyl methacrylate, phenyl methacrylate, lauryl methacrylate, etc. Esters, 2- (N, N-diethylamino) ethyl acrylate, 2- (N, N-dimethylamino) ethyl acrylate, 2- (N, N-dibenzylamino) methyl acrylate, acrylic acid -2- (N, N-diechi Unsaturated substituted amino alcohol esters such as amino) propyl, unsaturated carboxylic acid amides such as acrylamide and methacrylamide, ethylene glycol diacrylate, propylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol di Compounds such as acrylate, triethylene glycol diacrylate, polyfunctional compounds such as dipropylene glycol diacrylate, ethylene glycol diacrylate, propylene glycol dimethacrylate, diethylene glycol dimethacrylate, and / or two or more thiol groups in the molecule Polythiol compounds having, for example, trimethylolpropane trithioglycolate, trimethylolpropane trithiopropylate, pentaerythritol Examples include tetrathioglycolate.

  Usually, as a monomer in an ionizing radiation curable resin composition, the above compounds are used alone or in combination of two or more as necessary, but the ionizing radiation curable composition is given a normal coating suitability. Therefore, the prepolymer or oligomer is preferably 5% by weight or more, and the monomer and / or polythiol compound is preferably 95% by weight or less.

  When flexibility is required when the ionizing radiation curable resin composition is cured, it is preferable to reduce the amount of monomer or use an acrylate monomer having 1 or 2 functional groups. When wear resistance, heat resistance, and solvent resistance are required when the ionizing radiation curable resin composition is cured, an ionizing radiation curable resin is used such as using an acrylate monomer having three or more functional groups. A composition design is possible.

  Further, as shown by 31b in FIG. 2, luminance unevenness can be more effectively reduced by mixing light diffusing fine particles into the lens portion. At this time, when the ionizing radiation curable resin is used for the lens portion, the refractive index difference between the ionizing radiation curable resin and the light diffusing fine particles is preferably 0.07 to 0.09. The addition ratio of the light diffusing fine particles is preferably the light diffusing fine particles 30 with respect to the ionizing radiation curable resin 90 and the light diffusing fine particles 30 with respect to the ionizing radiation curable resin 70. Further, two or more kinds of light diffusing fine particles having the same refractive index and different particle diameters may be mixed.

  The shape of the diffusing fine particles can be applied without particular limitation, such as a spherical shape, an amorphous shape, a rugby ball type, and a hollow type, but a spherical shape is preferable.

  Basically, the microlens array is provided with a recess corresponding to the shape of the projection of the microlens array on the mold forming surface of the mold substrate material. It is obtained by filling the composition, curing it with ionizing radiation, and molding it.

  First, a concave portion corresponding to the shape of a special protrusion of the optical sheet for backlight dimming of the present invention is formed on the mold forming surface of the mold substrate material. As a mold substrate material, a substrate coated with ceramics or the like is prepared. Considering the strength at the time of handling, the mold substrate is preferably a metal plate made of a metal such as iron or a metal roll.

  A recess forming layer is formed on the surface of the mold substrate. As the recess forming layer, a layer of ceramics such as chromium oxide, alumina or zirconia, copper, aluminum or the like is preferable. Among these, the ceramic layer can be formed on the substrate as a recess forming layer by plasma spraying or low temperature plasma spraying, and the copper, aluminum, or the like layer can be formed on the substrate by plating or the like.

  For the recess forming layer, a laser is used to form a recessed mold by forming an inverted cone in the irradiated portion and forming a plurality of recesses in which the deepest portion forms part of the inner surface of the sphere. . The laser light source is selected from a high-power laser such as a carbon dioxide laser, a YAG laser, or a ruby laser, and is irradiated while relatively moving the laser beam and the mold substrate using a lens. The control of the deepest spherical shape is performed by adjusting the laser output and focal length.

  Next, the ionizing radiation curable composition is applied onto the obtained concave mold surface, and at least the concaves are filled with the ionizing radiation curable composition. Except for the recess, the ionizing radiation curable composition may or may not be applied. If necessary, apply doctoring. Laminate a transparent substrate film through which ionizing radiation can be transmitted from above the coated film, taking care not to contain air bubbles, and laminate a concave mold, ionizing radiation curable resin composition, and a transparent substrate film. Let it be the body.

  By irradiating ionizing radiation from the outside of the transparent substrate film 32 of the laminate, the ionizing radiation curable resin composition in the laminate is cured and the ionizing radiation curable resin composition is adhered to the transparent substrate film. Thereafter, the transparent substrate film is peeled off from the concave mold together with the cured product to obtain the microlens array sheet of the present invention. As the ionizing radiation used for irradiation, either electron beam or ultraviolet rays can be used, but it is more preferable to use ultraviolet rays which are compact and easy to handle.

  In addition, in the above-mentioned process, in short, it is only necessary to laminate the concave mold, the ionizing radiation curable resin composition, and the transparent substrate film, so that the ionizing radiation curing is performed on the transparent substrate film as described above. After applying the functional resin composition, it may be superimposed on the concave mold, or may be superimposed after the application is performed on both the concave mold and the transparent substrate film. In short, the side having the concave concave section and The ionizing radiation curable resin composition is filled while the transparent substrate films are stacked, and the concave mold, the ionizing radiation curable resin composition, and the transparent substrate film are laminated.

  In the above description, the microlens array sheet 31 has been described as having the microlens array 30 laminated on the transparent base film 32. However, a transparent substrate film 32 is not used by using a flat type instead of the transparent base film, and by making the concave type and the opposite type opposite to each other when forming the microlens array 30, and adjusting the gap. Can be formed of the same material at the same time. However, the planar type transmits ionizing radiation such as ultraviolet rays, and further needs to have releasability with respect to the cured microlens array material.

  The reflection unit 5 includes an air layer 5a and a reflection layer 5b. When the thickness (height) of the reflecting portion is about 12 ± 2 μm and the width is 100, the width of the reflecting layer is 55 to 70 and the width of the air layer is 30 to 45.

  The reflective layer 5b has a rectangular cross-sectional shape extending in the depth direction on the paper surface on the back surface side of the lens unit 1, and a plurality of the reflective layers 5b are arranged at regular intervals along the left-right direction on the paper surface, and are formed in stripes. The reflective layer 5b reflects light incident on the reflective layer 5b out of the light P emitted from the backlight unit 20 to the back side, and re-reflects the reflected light on the reflective plate 20b. And the light utilization efficiency can be improved by injecting the light re-reflected by the reflecting plate 20b to the display screen side again.

  The material of the reflective layer 5b is, for example, an ink formed by dispersing or mixing metal particles such as titanium dioxide, barium sulfate, magnesium oxide, or the like, a laminate formed of a metal foil, or a metal material such as silver. The thing etc. which vapor-deposited etc. are employable. The cross-sectional shape of the reflective layer is not limited to a rectangular cross section. For example, a trapezoidal cross section, a rectangular cross section, or a cross-sectional shape with rounded corners on the back side of the trapezoidal cross section can be adopted.

  An opening is formed between the reflective layers 5b, and this opening is configured as an air layer 5a. The air layer 5a regulates the incident range of light on each of a plurality of lenses (to be described later) in the lens unit 1 between the surface on the display screen side of the bonding layer 6 and the interface on the back side of the lens unit 1. is there. The air layer 5a has a lower refractive index than the bonding layer 6 described later, and light once diffused in the diffusion layer 7 is refracted at the interface between the bonding layer 6 and the air layer 5a, thereby passing through the air layer 5a. Light incident on the lens unit 1 at a large incident angle can be collected again in the center.

  The lens unit 1 collects diffused light transmitted through the air layer 5a to the display screen side, so that a plurality of optical elements, for example, lenses are arranged in an array at equal intervals so as to face different air layers 5a. It is a thing. The lens unit 1 is made of, for example, a PET resin, a PC resin, PMMA (polymethyl methacrylate), COP (cycloolefin polymer), or the like, which is well known in the technical field, such as an extrusion molding method, an injection molding method, or a hot press. It can be formed by a molding method. Alternatively, it can be molded using an ultraviolet (UV) curable resin.

  The lens unit 1 is preferably made of the same material as the lens unit 31. Due to the heat from the light source, the backlight light control optical sheet tends to be convex toward the light source side, and the warpage can be reduced by making the lens portions 1 and 31 the same material.

  The lens unit 1 is composed of a convex cylindrical lens array in which a convex cylindrical lens whose lens surface 1a formed convex on the display screen side is extended in the depth direction in the drawing is a unit lens. That is, it is configured as a lenticular lens. The convex cylindrical lens array preferably has a height of 50 to 60 μm and a pitch of 130 to 140 μm.

  As the shape of the lens surface, a well-known appropriate lens surface shape such as a spherical surface or an elliptical surface may be adopted depending on the required light collecting performance. Further, in order to improve the light collection efficiency, an aspherical shape in which an ellipsoidal surface is used as a reference surface and correction is performed by a high-order term may be used.

Here, the bonding layer 6 is for stacking and integrating the diffusion layer 7 with the lens unit 1 provided with the reflection unit 5, and the diffusion layer 7 and the reflection unit 5 are interposed via the bonding layer 6. It is pasted.
The thickness of the bonding layer 6 is preferably 20 μm or more. When it is thinner than 20 μm, peeling occurs at a high temperature of 80 ° C. or higher. The upper limit of the thickness of the bonding layer is not theoretically, but is preferably up to about 40 μm in terms of cost.

  Examples of the constituent material of the bonding layer 6 include a light-transmitting pressure-sensitive adhesive. The main raw material of the pressure-sensitive adhesive of the present embodiment is composed of at least one of polymer materials such as acrylic, rubber-based, silicone-based, and vinyl-based materials. In these polymer materials, a tackifier, a tackifier, and the like are used. Those containing additives are preferred.

  Further, the above-mentioned pressure-sensitive adhesive contains fine particles made of organic or inorganic fine particles having a spherical or amorphous shape. By including the fine particles, the elastic modulus of the pressure-sensitive adhesive becomes appropriate, the flowability of the pressure-sensitive adhesive is reduced, and the air layer is held during bonding. When fine particles are not included, the pressure-sensitive adhesive flows at a high temperature of 80 ° C. or higher, and the air layer is crushed.

  As a specific method for producing the pressure-sensitive adhesive used for the bonding layer 6, first, a light-diffusing fine particle is prepared by mixing and stirring a main polymer material and various additives in an organic solvent in which the light-diffusing fine particles are dispersed. Is dispersed in an adhesive to produce a dispersion. Furthermore, a pressure-sensitive adhesive can be obtained by mixing a crosslinking agent with this dispersion, and applying and drying the substrate. The base material used at this time may be a film obtained by subjecting an inexpensive base material such as PET to a release treatment. Moreover, there is no restriction | limiting in particular as the application method to a base material, and a drying system.

  Below, it demonstrates based on an Example. We compared the light source's ability to cancel the light and dark unevenness when the shape of the microlens was changed. Using CCFL as the light source, visually compare the degree of unevenness of the light source over the backlight dimming optical sheet under the conditions of a distance of 39 mm from the CCFL to the backlight dimming optical sheet and a distance of 18 mm between the CCFLs did.

  As an optical sheet for backlight dimming, a sample sheet having the 21 configuration shown in FIG. 1 was prepared and used.

  <Evaluation> Evaluation was performed with “x” indicating that the light and dark unevenness could be visually detected and “◯” indicating that it was not detectable. (H: height of the microlens, L: length of a piece of the bottom of the microlens, r: radius of the sphere at the top of the microlens).

<Example 1>
The brightness was fixed when h = 70 μm and r / L = 0.1, and the uneven brightness was evaluated when L was changed. The results are shown in Table 1, and it was a good result that the length (L) of the bottom piece of the microlens was not perceptible with the naked eye (visually) in the range of 40 to 50 μm.

<Example 2>
Fixing was performed with L = 45 μm and r / L = 0.1, and the brightness unevenness when h was changed was evaluated.
The results are shown in Table 2. As the microlens height (h) was in the range of 10 to 200 μm, light / dark unevenness could not be detected visually.

<Example 3>
L = 45 μm and h = 70 μm were fixed, and the uneven brightness was evaluated when r / L was changed.
The results are shown in Table 3. Light / dark unevenness is detected visually when the radius of the sphere at the top of the microlens (r) / the length of the bottom piece of the microlens (L) is 0.05 to 0.4. could not.

  As described above, in the backlight light control optical sheet in which the brightness control member and the diffusion layer are integrated, the light source side diffusion plate surface has a conical shape having a bottom diameter L of 40 μm to 50 μm and a height of 10 μm to 200 μm. When the microlens array is closely arranged and the ratio r / L of the curvature radius r of the spherical surface at the top of each microlens to the L is 0.05 to 0.4, the unevenness of the light and darkness of the light source is visually observed. As a result, it was possible to reduce to a level where it could not be detected.

  It should be noted that the technical scope of the present invention is not limited to the above-described embodiments, and includes those in which various modifications are made to the above-described embodiments without departing from the spirit of the present invention.

  For example, in the above-described embodiment, the configuration of the color display is not particularly described as the display device. However, if a known configuration such as providing a color filter on the viewing side of the liquid crystal display unit is added, a display that performs color display. Needless to say, it can also be applied to devices.

  In addition, the optical sheet for backlight dimming according to the present invention is not limited to the lens surface on the user side being a lenticular lens sheet, and a sheet in which prism sheets and other unit lenses are arranged in an array is used. be able to.

DESCRIPTION OF SYMBOLS 1 ... Lens part 1a ... Lens surface 5 ... Reflection part 5a ... Air layer (opening part)
5b ··· reflective layer 6 · · · bonding layer 7 · · · diffusion layer 8 · · · adhesive layer 20 · · backlight portion 20a · light source 20b · reflector 21 · · optical sheet 22 for backlight dimming Liquid crystal display 23.. Backlight unit 30. Microlens array 31. Microlens array sheet 32. Transparent substrate film 33. Conical convex part 34 of microlens. Top 100 of microlens apparatus

Claims (9)

  A diffusion layer for diffusing light from the light source; a luminance control member having a repetitive array structure of lenses disposed on the diffusion light emission side of the diffusion layer; and formed between the diffusion layer and the luminance control member. And a light control optical sheet for backlight dimming having a reflection part provided with an opening for restricting an incident angle range of light with respect to each lens of the brightness control member, and a microlens on a light source side surface of the diffusion layer An optical sheet for backlight dimming, wherein an array is formed.   A diffusion layer for diffusing light from the light source; a luminance control member having a repetitive array structure of lenses disposed on the diffusion light emission side of the diffusion layer; and formed between the diffusion layer and the luminance control member. And a light-regulating optical sheet having an opening that regulates an incident angle range of light with respect to each lens of the brightness control member, the adhesive on the light source side surface of the diffusion layer An optical sheet for backlight dimming, wherein a microlens array sheet on which a microlens array is formed is integrated through a layer.   The optical sheet for backlight dimming according to claim 2, wherein the microlens array sheet comprises a transparent base film and a microlens array formed thereon.   The microlens array sheet includes a transparent base film and a microlens array formed thereon, and the transparent base film and the microlens array are simultaneously formed using the same material. The optical sheet for backlight dimming according to claim 2,   In the microlens array, microlenses made of a cured product of an ionizing radiation curable resin composition are densely arranged, and the shape of each microlens is a part of a spherical surface at the top, and the diameter L at the bottom is 40 μm. It has a conical shape with a height of 50 μm and a height of 10 μm to 200 μm, and the ratio (r / L) of the radius of curvature r of the top spherical surface to the diameter L of the bottom is 0.05 to 0.4. The optical sheet for backlight light control according to any one of claims 1 to 4.   6. The optical sheet for backlight dimming according to claim 1, wherein light diffusing fine particles having a particle diameter of 10 μm or less are added to the microlens array at a ratio of 10 wt% to 30 wt%. .   The optical sheet for backlight dimming according to claim 1, wherein the base material on the light incident side is the same as that on the light emitting side.   A backlight unit comprising the optical sheet for backlight dimming according to claim 1.   A display device comprising the backlight unit according to claim 8.

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