JP2007213035A - Optical sheet, and backlight unit and display using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet capable of uniforming light rays from a light source without increasing a waste fraction of existing light rays and capable of exiting lightrays while controlling a diffusion range. <P>SOLUTION: The optical sheet (10) used to control an illumination light path of a backlight unit for a display comprises, from the entry side of the illumination light (L): at least a light scattering layer (13) for scattering the illumination light (L) to the exit surface (12) side; an adhesion layer or sticking layer (18); a light reflection layer (14) for reflecting the light scattered by the scattering layer (13) to the light scattering layer (13) side; and a lens sheet (17) fixed at its flat back side to the other surface of the light reflection layer (14) and having a plurality of unit lenses (16) arranged on its front side. The light reflection layer (14) has openings (15) having one-to-one correspondence with the unit lenses (16), and the adhesion layer or sticking layer (18) has a thickness less than that of the light reflection layer (14). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement of an optical sheet used for illumination light path control in a display backlight unit mainly using a liquid crystal display element, and further a backlight unit and a display equipped with the optical sheet. About.

  A display typified by a liquid crystal display device (LCD) is remarkably widespread in a type including a light source necessary for recognizing provided information. In a battery-powered device such as a laptop computer, the power consumed by the light source occupies a substantial portion of the power consumed by the entire battery-powered device.

  Thus, battery life is increased by reducing the total power required to provide a given brightness. This is particularly desirable for battery powered devices.

  A brightness enhancement film (BEF) which is a registered trademark of 3M Corporation of the United States is widely used as an optical sheet for solving this problem.

  BEF is a film in which unit prisms 72 having a triangular cross section are periodically arranged in one direction on a member 70 as shown in FIG.

  The unit prism 72 has a size (pitch) larger than the wavelength of light.

  BEF collects light from “off-axis” and redirects this light “on-axis” or “recycle” toward the viewer. To do.

  When using the display (when observing), BEF increases on-axis brightness by reducing off-axis brightness. Here, “on-axis” is a direction that coincides with the visual direction of the viewer, and is generally the normal direction (direction F shown in FIG. 1) side with respect to the display screen.

  If the repetitive array structure of the unit prisms 72 is arranged in only one direction, only the direction change or recycling in the parallel direction is possible. In order to control the luminance of the display light in the horizontal and vertical directions, Two sheets are stacked and combined so that the parallel directions are substantially orthogonal to each other.

  By adopting such BEF, a display designer can achieve a desired on-axis brightness while reducing power consumption.

For example, JP-B-1-37801 and JP-A-6-102506 disclose a technique in which a luminance control member having a repetitive array structure of unit prisms 72 represented by BEF is adopted for a display. Many are known as shown in Japanese Laid-Open Patent Publication No. 10-506500.
Japanese Patent Publication No. 1-378001 JP-A-6-102506 Japanese National Patent Publication No. 10-506500

  In the optical sheet using the BEF as a brightness control member as described above, the light L from the light source 20 is finally emitted at a controlled angle φ by the refraction action X as shown in FIG. Thus, it is possible to control to increase the intensity of light in the visual direction F of the viewer. However, at the same time, the light component due to the reflection / refraction action Y is unnecessarily emitted in the lateral direction without proceeding in the visual direction F of the viewer.

  Therefore, the light intensity distribution emitted from the optical sheet using the BEF as shown in FIG. 1 has a viewer's visual direction F, that is, an angle with respect to the visual direction F is 0 as shown in the light intensity distribution B of FIG. Although the light intensity at 0 ° can be maximized, there is a problem that the amount of light emitted from the horizontal direction is increased as indicated by a small light intensity peak around ± 90 ° shown on the horizontal axis in the figure.

  Further, when the member 70 is employed in a direct type backlight unit that does not employ a light guide plate constituting an edge light type surface light source, a light diffusion layer (light diffusion layer) is formed between the light source 20 and the member 70. In general, a configuration in which a single plate or a combination of a light diffusion film is interposed is provided. However, when the light diffusion layer is provided in this way, the flat member 70 and the light diffusion layer (not shown) are clear. When the flat surfaces having no level difference come into contact with each other, the boundary is not clear, and when both are materials having a close refractive index, the incident light does not enter the unit prism 72 at the intended angle, and the unit It becomes difficult to achieve optical characteristics as designed by the prism 72.

  In particular, when adopting a configuration in which the member 70 and the light diffusing layer are laminated and integrated via an adhesive layer or an adhesive layer, unexpected generation of incident light components (or deterioration of the function due to the light diffusing layer) is caused. It becomes easier to invite and it becomes more difficult to achieve optical characteristics as designed.

  The present invention has been made in view of such circumstances, and can uniformly emit light from a light source without increasing the amount of light emitted unnecessarily, and can emit light while controlling the diffusion range. An object is to provide an optical sheet.

  In the following description of the present application, “diffusion” and “scattering” of optical characteristics, “adhesive layer” and “adhesive layer”, and “optical sheet” and “optical film” according to the present application are synonymous. Will be used.

  In order to achieve the above object, the present invention takes the following measures.

  That is, the optical sheet according to the first aspect of the present invention is an optical sheet used for illumination optical path control in a display backlight unit, and the illumination light is directed to the non-incident surface side in order from the incident light incident side. A light scattering layer that scatters to the light exit surface side, an adhesive layer or an adhesive layer, and a surface that is adhered or adhered to the light scattering layer by the adhesive layer or the adhesive layer and faces the light exit surface side of the light scattering layer and has high light reflectivity A light reflecting layer that reflects light scattered by the light scattering layer to the light scattering layer side, and a flat back surface fixed to the other surface of the light reflecting layer, and a plurality of unit lenses on the surface And a lens sheet that is arranged. The light scattering layer may be, for example, a diffusion sheet using a base material represented by commonly used PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), PP (polypropylene), PE (polyethylene), or the like. , A diffusion plate using a substrate represented by PC, PMMA, acrylic, PS (polystyrene), or the like may be used. The light reflecting layer has an opening corresponding to 1: 1 for each unit lens, and the thickness of the adhesive layer or the adhesive layer is thinner than that of the light reflecting layer.

  Furthermore, this lens sheet is a lenticular sheet having a lens part in which semi-cylindrical convex cylindrical lenses are arranged in one direction as a unit lens, and when parallel rays are incident on the lenticular sheet from the lens part side. In addition, by providing a light-transmitting stripe-shaped opening as an opening so as to include a portion where incident parallel rays are collected by the condensing function of the lens part, the non-opening is reflected in a stripe-shaped light In addition to the layers, the parallel pitch of the semi-cylindrical convex cylindrical lenses is equal to the formation pitch of the striped openings. As the unit lens shape described as a semi-cylindrical convex cylindrical lens, various types such as a spherical lens and an aspherical lens may be used, and various designs are used for the uneven height of the lens portion.

  For example, the opening that contacts the back surface of the lens sheet is an air layer. Or it consists of material of a lower refractive index than a lens sheet. The adhesive layer or the pressure-sensitive adhesive layer is an ultraviolet curable resin layer, a pressure-sensitive pressure-sensitive adhesive layer, a heat-sensitive adhesive layer, or the like. Alternatively, the layer may contain light diffusing fine particles. The light reflection layer is a white ink, a metal foil, a metal vapor deposition layer, or the like.

  Such a lens sheet is, for example, a monolithic molded body by press molding or extrusion molding using a thermoplastic resin. Moreover, it is the laminated structure by which the unit lens which consists of a hardened | cured material of a radiation curable resin or a thermoplastic resin superposition | polymerization adheres to the base-material sheet | seat surface.

  On the other hand, the second aspect of the present invention is a display backlight unit configured by providing such an optical sheet together with a light source on the back surface of an image display element that defines a display image. Here, as the light source, for example, a direct light source, a surface light source including an edge light type light source and a light guide plate, or the like is used.

  Furthermore, a third aspect of the present invention provides such a display backlight unit comprising: an image display element comprising a liquid crystal display element that defines a display image in accordance with transmission / shielding in pixel units; It is a display constructed by combining with a light source by a tube or LED.

  According to the present invention, it is possible to realize an optical sheet that can make light emitted from a light source uniform and emit light while controlling the diffusion range without increasing the amount of light emitted unnecessarily.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 4 is a side view showing an example of the optical sheet according to the embodiment of the present invention.

  That is, the optical sheet 10 according to the embodiment includes the light diffusion layer 13 that guides the light L from the light source 20 from the incident surface 11 and scatters the light L toward the emission surface 12 side.

  As is well known in the technical field, the light diffusion layer 13 has a structure including resin beads or fine particles (fillers) having different refractive indexes in a translucent resin, or any one surface. The thing of the structure processed into the mat form is used.

  Further, the light reflecting layer 14 is fixed to the emission surface 12 of the light diffusing layer 13 by an adhesive layer 18. The light reflecting layer 14 is made of, for example, white ink, a metal foil, and a metal vapor-deposited layer. As shown in the plan view of FIG. 5, a plurality of openings 15 made of, for example, an air layer are regularly provided.

  Further, a lens sheet 17 having a plurality of unit lenses 16 disposed on the surface is fixed to the other surface of the light reflecting layer 14 (the upper surface of the light reflecting layer 14 shown in FIG. 4).

  For the adhesive layer 18, for example, an ultraviolet curable resin (hereinafter also referred to as “UV curable adhesive”) or other types of adhesive is used. In order to improve the diffusibility of the light diffusion layer 13, a diffusion material is used. Sometimes mixed. In consideration of the adhesiveness that remains after the optical sheet 10 is manufactured, it is preferable to use the polymerization adhesive strength of an ultraviolet curable resin because it is less likely to cause deterioration with time and optical characteristics. Further, when the adhesive layer 18 made of an ultraviolet curable resin is formed over the entire surface of the lens sheet 17, when the adhesive layer 18 is cured, a portion that does not contact the light reflecting layer 14 is prevented from entering the opening 15. It is easy to be done and is suitable.

  FIG. 6 is a side view showing a configuration example of the lens sheet 17.

  In the example shown in FIG. 6, the lens sheet 17 has a lens portion in which unit lenses 16 made of a semi-cylindrical convex cylindrical lens having a height TL are arranged on one side at a pitch P, and a light source 20 is provided on the other side. A light reflecting layer 14 having a high light reflecting property is provided. In the light reflecting layer 14, openings 15 made of, for example, an air layer having a width A corresponding 1: 1 with each of the unit lenses 16 of the lens sheet 17 are arranged in a stripe shape. Then, the space between the opening 15 and the semi-cylindrical convex cylindrical lens is the same as or close to the semi-cylindrical convex cylindrical lens so that the light incident on the opening 15 efficiently enters the semi-cylindrical convex cylindrical lens. It has a structure filled with a material having a refractive index n.

The lens sheet 17 having such a configuration has a distance TB from the valley of the unit lens 16 to the surface on the opposite side in order to efficiently enter light into the unit lens 16 formed of a semi-cylindrical convex cylindrical lens.
P ≦ A + 2 * TB * tanα
Satisfy the relationship. However, α is a critical angle at the interface with the lens sheet 17 at the opening 15, and is defined by α = sin ⁻¹ (n ₀ / n) using the refractive index n ₀ of the opening 15.

On the other hand, A / P corresponds to the aperture ratio. As shown in FIG. 7, the aperture ratio A / P has a general characteristic that the half-value angle of view improves as the aperture ratio A / P increases, but the luminance decreases. For this reason, the aperture ratio A / P needs to be set in consideration of the balance between the luminance and the half-value angle of view. Therefore, between the height TL, the distance TB, the width A of the opening, and the pitch P,
0.3 <TL / P <0.6, (1) Formula 0.3 <TB / P <1.0, (2) Formula 0.3 <A / P <0.6 (3) It is going to be established.

  In the formula (1), when TL / P is 0.3 or less, the light condensing property of the lens is insufficient, and when it exceeds 0.6, the directivity is too strong, which is not suitable for TV use and is molded. It becomes difficult.

  In Formula (2), if TB / P is out of the above range, light cannot be efficiently guided to the lens, resulting in an increase in light loss.

  In the formula (3), when A / P is 0.3 or less, the directivity is too strong, and the absorption in the white reflection layer appears remarkably, resulting in a large light loss. On the other hand, at 0.6 or more, the diffusibility is too strong (the light condensing property is weak), and it is difficult to improve the front luminance.

  Further, the range of the angle θ formed by the boundary (valley part) between the unit lenses 16 adjacent to each other is preferably 35 ° to 60 ° as will be described below.

  That is, if the angle θ formed by the boundary (valley part) between the unit lenses 16 adjacent to each other is less than 35 °, the mold releasability after molding deteriorates, or the mold tip is bent while the molding is repeated. Therefore, it is difficult to release the molded product, or the tip of the mold is damaged when handling the mold, and the mold life tends to be shortened. In order to widen the orientation characteristics of the unit lens 16, the radius of curvature of the semi-cylindrical convex cylindrical lens may be reduced, or the cross-sectional shape may be designed to be an aspherical (elliptical) shape. By making the angle θ formed by the 16 boundaries (valleys) to be 60 ° or less, good orientation characteristics can be realized.

  On the other hand, when the angle θ exceeds 60 °, the unit lens 16 has a gentle shape, so that the lens function is lowered and the orientation angle is narrowed, and the light intensity in the visual direction of the viewer is increased. This is an adverse effect in realizing the object of the present invention.

  The unit lens 16 is not limited to a semi-cylindrical convex cylindrical lens, and a lens sheet in which convex lenses are two-dimensionally arranged, and a semi-cylindrical convex cylindrical lens as the unit lens 16 is arranged in parallel in one direction. In the case of a lenticular sheet having a lens portion and other lens sheets, it does not depart from the gist of the present invention.

  Such a lens sheet 17 is made of, for example, a thermoplastic resin well known in the art using PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), COP (cycloolefin polymer), or the like. It is a monolithic molded product molded by press molding or extrusion molding using slag. Alternatively, by ultraviolet curing molding method in which an ultraviolet solidified resin is placed on a base material of PET (polyethylene terephthalate), PP (polypropylene), PC (polycarbonate), PMMA (polymethyl methacrylate), PE (polyethylene), etc. It may be formed.

  The opening 15 has a refractive index lower than that of the light diffusion layer 13 and the lens sheet 17 and is formed at a position corresponding to each of the plurality of unit lenses 16.

  As the locations where the openings 15 are formed, preferably, the apex of each unit lens 16 in the lens sheet 17 and the surface of the light reflecting layer 14 of each opening 15 corresponding to each unit lens 16 (shown in FIG. 4). When the cross section of the light reflection layer 14 is taken as a cross section, each line connecting the cross-sectional centers G is substantially orthogonal to the surface of the light reflection layer 14 (upper surface of the light reflection layer 14 shown in FIG. 4). I have to.

  In other words, the openings 15 are formed such that the cross-sectional center G of each opening 15 exists on the perpendicular drawn from the apex of each unit lens 16 along the thickness direction of the optical sheet 10.

  Alternatively, the light reflecting layer 14 may be provided in a region including the non-light-collecting surface of the unit lens 16, and the opening 15 may be provided in a region other than the light reflecting layer 14. Note that the opening 15 may have not only a flat surface but also a convex or concave portion formed on the surface. In the case of a convex shape, it is preferable in terms of manufacturing to make it lower than the convex portion corresponding to the stripe.

  As the width A of the opening 15 is increased, scattered light that has not been sufficiently narrowed is also incident on the unit lens 16, so that the light component that is not emitted in the visual direction F of the viewer as described above. Will increase.

  On the other hand, as the width A of the opening 15 is reduced, only the scattered light that is more uniformly focused enters the unit lens 16, and in some cases, the unevenness of the emitted light emitted from the unit lens 16 increases. End up.

  Therefore, the shape and width A of the opening 15 are design matters determined according to specifications required for the optical sheet 10.

  For example, when a lenticular sheet as described above is used as the lens sheet 17, when the parallel light beam is incident from the lens unit side, the lens unit 17 includes a portion where the incident parallel light beam is collected by the condensing function of the lens unit. As described above, for example, by providing a light-transmitting stripe-shaped opening 15 such as an air layer, the non-opening is formed of the stripe-shaped light reflecting layer 14 and the semi-cylindrical convex cylindrical lens is formed. The parallel pitch and the formation pitch of the striped openings 15 may be made equal.

  The light reflection layer 14 partially penetrated by the plurality of regularly arranged openings 15 uses a printing method, a transfer method, a photolithography method, or the like well known in the art. Form. Or it forms by application | coating formation of the ink layer formed by disperse-mixing a metal filler, transfer formation, or lamination formation of metal foil.

  Alternatively, a so-called “self-alignment method” that defines the position where the opening 15 is formed using the condensing characteristic of the lens itself is also employed as a method of photolithography.

  In defining the opening 15 by the self-alignment method, as shown in FIG. 4, the opening 15 corresponding to each unit lens 16 includes a perpendicular drawn from the top of the unit lens 16 to the back surface of the lens sheet 17. Therefore, the lens sheet 17 is required to irradiate the entire surface from the unit lens 16 side with parallel light.

  In addition, the photosensitive resin layer used in the self-alignment method may remain in the defined opening 15, but transparency is maintained in consideration of optical characteristics and resistance after the optical sheet 10 is manufactured. The type of the photosensitive resin is preferably employed, and the refractive index is more preferably lower than that of the lens sheet 17 (for example, close to air).

  Next, the operation of the optical sheet according to the embodiment configured as described above will be described with reference to FIG.

  That is, in the optical sheet 10 according to the embodiment, the light L from the light source 20 is incident from the incident surface 11 of the light diffusion layer 13. Here, the light L incident on the light diffusion layer 13 is randomly scattered. Of the scattered light, only the light γ that has passed through the opening 15 is guided to the lens sheet 17.

  Since each opening 15 is provided so as to face the apex of each unit lens 16 provided in the lens sheet 17, each unit lens 16 has only the light confined by each corresponding opening 15. Is guided.

  That is, since each opening 15 functions like a slit, only light γ with a narrowed scattering angle is incident on each unit lens 16, so that light incident on the unit lens 16 from an oblique direction is incident. Therefore, it is possible to eliminate the light that is emitted in the lateral direction without traveling in the visual direction F of the viewer. On the other hand, the light β that could not pass through the opening 15 is reflected by the light reflection layer 14 and returned to the light diffusion layer 13 side.

  Then, after being similarly scattered in the light diffusion layer 13, eventually becomes light γ with a narrowed scattering angle, then enters the unit lens 16 through the opening 15, and enters the predetermined angle φ by the unit lens 16. It is emitted after being diffused.

  As described above, the light L from the light source 20 is scattered, and only the light γ with a narrowed scattering angle can be incident on the unit lens 16, and the light that could not be incident on the unit lens 16 is wasted. Therefore, it is possible to emit light while controlling the diffusion range while improving the utilization efficiency of the light from the light source 20.

  Accordingly, as shown in FIG. 9, the light intensity distribution A emitted from the optical sheet 10 according to the embodiment is a light intensity distribution B emitted from the optical sheet using BEF. The distribution is such that a small light intensity peak around ± 90 ° on the axis disappears and the light intensity in the visual direction F of the viewer centered on 0 ° shown on the horizontal axis in the figure can be further increased.

  In addition, in order to further control the light emitted from the unit lens 16, a light scattering layer made of a sheet or film having a light scattering property on the light emitting surface side which is the upper side of the unit lens 16 in FIGS. 4 and 8, A reflective polarization separation film (both not shown) may be further provided.

  Hereinafter, various specific examples of the optical sheet according to the above embodiment will be described.

Example 1
A cylindrical lens group having a radius of curvature of unit lens 16 of 100 μm and an arrangement pitch of 200 μm is formed on one surface of a PET film (thickness: 75 μm) with a cured product of acrylic ultraviolet curable resin.

  As the light reflecting layer 14, a white ink layer (15 μm thick) is formed by a transfer method so that the ratio of the opening 15 to the light reflecting layer 14 is 1: 1.

At this time, P ≦ A + 2 * TA * tan α is satisfied,
TL / P = 0.31
TB / P = 0.38
A / P = 0.5
Thus, the optical sheet satisfies the conditions of the expressions (1) to (3).

(Example 2)
A cylindrical lens group having a radius of curvature of unit lens 16 of 100 μm and an arrangement pitch of 200 μm is formed on one surface of a PET film (thickness: 75 μm) with a cured product of acrylic ultraviolet curable resin.

  As the light reflecting layer 14, a white ink layer (15 μm thick) is formed by a transfer method so that the ratio of the opening 15 to the light reflecting layer 14 is 1: 1.

  Further, an acrylic pressure-sensitive adhesive material or heat-sensitive adhesive material (5 μm thickness) is formed as the adhesive layer 18, and is bonded to a PET film (75 μm thickness) to be the light diffusion layer 13 to create the optical sheet 10.

  Thus, the adhesive layer 18 is thinner than the white ink layer which is the light reflecting layer 14. Therefore, when the adhesive layer 18 is formed over the entire surface of the lens sheet 17, the portion that does not contact the light diffusion layer 13 enters the opening 15 and fills it, based on the difference in refractive index, Influencing the optical properties is avoided.

(Example 3)
A cylindrical lens group having a radius of curvature of unit lens 16 of 100 μm and an arrangement pitch of 200 μm is formed on one surface of a PET film (thickness: 75 μm) with a cured product of acrylic ultraviolet curable resin.

  As the light reflecting layer 14, a white ink layer (15 μm thick) is formed by a transfer method so that the ratio of the opening 15 to the light reflecting layer 14 is 1: 1.

  Further, as the adhesive layer 18, an acrylic pressure-sensitive adhesive material or heat-sensitive adhesive material (5 μm thickness) added with 10% by weight of a spherical acrylic resin filler (average particle size 5 μm) as a diffusing material is provided. A PET film (75 μm thick) and an optical sheet 10 to be bonded are prepared.

  Also in this case, the thickness of the adhesive layer 18 is smaller than that of the white ink layer that is the light reflecting layer 14 as in the second embodiment.

Example 4
A cylindrical lens group having a radius of curvature of unit lens 16 of 100 μm and an arrangement pitch of 200 μm is formed on one surface of a PET film (thickness: 75 μm) with a cured product of acrylic ultraviolet curable resin.

  As the light reflecting layer 14, a white ink layer (15 μm thick) is formed by a transfer method so that the ratio of the opening 15 to the light reflecting layer 14 is 1: 1.

  Further, a UV curable adhesive material (5 μm thickness) is provided as the adhesive layer 18, and a PET film (75 μm thickness) to be the light diffusion layer 13 is bonded to the optical sheet 10.

  Also in this case, the thickness of the adhesive layer 18 is smaller than that of the white ink layer that is the light reflecting layer 14 as in the second embodiment.

(Example 5)
A cylindrical lens group having a radius of curvature of unit lens 16 of 100 μm and an arrangement pitch of 200 μm is formed on one surface of a PET film (thickness: 75 μm) with a cured product of acrylic ultraviolet curable resin.

  As the light reflecting layer 14, a white ink layer (15 μm thick) is formed by a transfer method so that the ratio of the opening 15 to the light reflecting layer 14 is 1: 1.

  Further, as the adhesive layer 18, a UV curable adhesive material (5 μm thickness) added with 10% by weight of a spherical acrylic resin filler (average particle size 5 μm) as a diffusion material is provided, and a PET film (75 μm) that becomes the light diffusion layer 13. Thickness) and a bonded optical sheet 10 are created.

  Also in this case, the thickness of the adhesive layer 18 is smaller than that of the white ink layer that is the light reflecting layer 14 as in the second embodiment.

(Example 6)
A cylindrical lens group having a radius of curvature of unit lens 16 of 100 μm and an arrangement pitch of 200 μm is formed on one surface of a PET film (thickness: 75 μm) with a cured product of acrylic ultraviolet curable resin.

  As the light reflecting layer 14, a white ink layer (15 μm thick) is formed by a transfer method so that the ratio of the opening 15 to the light reflecting layer 14 is 1: 1.

  Further, an acrylic pressure-sensitive adhesive material or heat-sensitive adhesive material (5 μm thickness) is provided as the adhesive layer 18, and a diffusion film (100 μm thickness, haze 90, transmittance 90) to be the light diffusion layer 13 is bonded to the optical sheet 10. create.

  Also in this case, the thickness of the adhesive layer 18 is smaller than that of the white ink layer that is the light reflecting layer 14 as in the second embodiment.

(Example 7)
A cylindrical lens group having a radius of curvature of unit lens 16 of 100 μm and an arrangement pitch of 200 μm is formed on one surface of a PET film (thickness: 75 μm) with a cured product of acrylic ultraviolet curable resin.

  As the light reflecting layer 14, a white ink layer (15 μm thick) is formed by a transfer method so that the ratio of the opening 15 to the light reflecting layer 14 is 1: 1.

  Further, as the adhesive layer 18, an acrylic pressure-sensitive adhesive material or heat-sensitive adhesive material (5 μm thickness) to which 10% by weight of a spherical acrylic resin filler (average particle diameter 5 μm) is added as a diffusion material is provided. A diffusion film (100 μm thickness, haze 90%, transmittance 90%) and a laminated optical sheet 10 are prepared.

  Also in this case, the thickness of the adhesive layer 18 is smaller than that of the white ink layer that is the light reflecting layer 14 as in the second embodiment.

(Example 8)
A cylindrical lens group having a radius of curvature of unit lens 16 of 100 μm and an arrangement pitch of 200 μm is formed on one surface of a PET film (thickness: 75 μm) with a cured product of acrylic ultraviolet curable resin.

  As the light reflecting layer 14, a white ink layer (15 μm thick) is formed by a transfer method so that the ratio of the opening 15 to the light reflecting layer 14 is 1: 1.

  Further, a UV curable adhesive material (5 μm thickness) is provided as the adhesive layer 18, and a diffusion film (100 μm thickness, haze 90%, transmittance 90%) to be the light diffusion layer 13 is bonded to the optical sheet 10.

  Also in this case, the thickness of the adhesive layer 18 is smaller than that of the white ink layer that is the light reflecting layer 14 as in the second embodiment.

Example 9
A cylindrical lens group having a radius of curvature of unit lens 16 of 100 μm and an arrangement pitch of 200 μm is formed on one surface of a PET film (thickness: 75 μm) with a cured product of acrylic ultraviolet curable resin.

  As the light reflecting layer 14, a white ink layer (15 μm thick) is formed by a transfer method so that the ratio of the opening 15 to the light reflecting layer 14 is 1: 1.

  Further, as the adhesive layer 18, a UV curable adhesive material (5 μm thickness) to which 10% by weight of a spherical acrylic resin filler (average particle size 5 μm) is added as a diffusion material is provided, and a diffusion film (100 μm) that becomes the light diffusion layer 13. (Thickness, haze 90%, transmittance 90%) and a bonded optical sheet 10 are prepared.

  Also in this case, the thickness of the adhesive layer 18 is smaller than that of the white ink layer that is the light reflecting layer 14 as in the second embodiment.

  Next, the performance when the optical sheets 10 according to Examples 1 to 9 were applied to a backlight unit for display of a 26-inch liquid crystal television was evaluated. As an evaluation condition, a television configuration including a cold cathode tube, an optical sheet group, and a liquid crystal panel is used, and a luminance meter (EZlite manufactured by Eldim) is sequentially used for the following optical sheet group. This was done by evaluating the viewing angle distribution of display brightness.

  When using 3M BEF as the brightness enhancement film, it is generally used in a configuration as shown in FIG. As each role, the diffusing plate has an effect of shadowing the light source by diffusing the light source light, and also serves as a base for laminating various optical films. The lower diffusion film has a role of diffusion that is not sufficient only by diffusion of the diffusion plate, and the reflective polarization separation film is, for example, DBEF, which is generally a reflective polarizing film manufactured by 3M, and is attached to the liquid crystal panel. The purpose is to reflect and reuse the polarized light that is originally removed by the polarizing film. Further, the DBEF function reduces the useless emission in the horizontal direction of the BEF luminance viewing angle characteristics as shown in FIG.

  The luminance distribution diagram shown in FIG. 11 shows the luminance distribution of light of a specific polarization component. By adopting DBEF, the polarizing element below the liquid crystal layer among the amount of backlight incident on the liquid crystal display element is shown. It shows that the amount of light of the component of the polarization axis that passes through increases.

  In the specific comparative configuration and embodiment shown in FIGS. 10, 12A, and 12B, the “upper diffusion film” and the “lower diffusion film” have directivity in light scattering (diffusion), and incident light. Is the difference in the characteristics of whether there are many scattered emission components in the upper direction of the screen or more scattered emission components in the lower direction.

  Each specification is as follows.

  Lower diffusion film 1: film thickness 2 mm, haze 95%, transmittance 80%.

  Lower diffusion film 2: film thickness 100 μm, haze 90%, transmittance 90%.

  Upper diffusion film 3: film thickness 100 μm, haze 40%, transmittance 90%.

  The image evaluation of the display was performed in the above comparative configuration and implementation configuration.

  The diffusion plate has a function of diffusing light, like the diffusion film, but the diffusion film has a flexible structure on the thin film, whereas the diffusion plate is formed by extrusion molding. Thus, the thickness is greater than that of the diffusion film and the rigidity is high.

  As described above, in the general configuration, it is necessary to use a large number of optical films. However, in the optical sheet according to the first aspect of the present invention, there is no reflective polarization separation film as shown in FIG. However, even if the reflective polarization separation film is replaced with a normal diffusion film or removed, the optical characteristics are not impaired.

  Moreover, in the optical sheet of the second aspect of the present invention, even if the diffusion plate and the lower diffusion film are removed, the optical characteristics are not impaired.

  Therefore, the product of the present invention is highly effective not only in its optical characteristics but also in terms of reducing the number of parts.

  The optical sheet according to the embodiment of the present invention as described above is not limited to being applied to a relatively large screen liquid crystal television provided with a direct type light source, but is an edge light type light source, a cold cathode ray tube, or a light source using LEDs, The present invention is also effective when applied to a medium to small display having a backlight unit including a light guide plate.

FIG. 1 is a perspective view showing a configuration example of a BEF. FIG. 2 is a diagram for explaining the optical action of BEF. FIG. 3 is a diagram showing the light intensity distribution of the BEF with respect to the angle with respect to the visual direction. FIG. 4 is a side view showing an example of the optical sheet according to the embodiment of the present invention. FIG. 5 is a plan view showing a stripe arrangement example of the light reflecting layer and the opening. FIG. 6 is a partial side view showing a detailed configuration example of the optical sheet according to the embodiment. FIG. 7 is a diagram illustrating a general relationship between the aperture ratio, the luminance, and the half-value angle of view. FIG. 8 is a diagram illustrating the optical action of the optical sheet according to the embodiment. FIG. 9 is an explanatory diagram showing a light intensity distribution with respect to an angle with respect to the visual direction of the optical sheet according to the embodiment. FIG. 10 is a conceptual diagram showing a backlight configuration for performance evaluation when the optical sheet according to the embodiment is applied to a display backlight. FIG. 11 is a diagram illustrating a light intensity distribution in a backlight to which the optical sheet of Example 1 is applied. FIG. 12A is a diagram showing a list of specific configurations of each part in the backlight configuration for performance evaluation illustrated in FIG. FIG. 12B is a diagram showing a list of specific configurations of each part in the backlight configuration for performance evaluation illustrated in FIG. 10.

Explanation of symbols

  B: Light intensity distribution, F: Visual direction, G: Cross-sectional center, L, β, γ: Light, P: Pitch, TB: Distance, X, Y: Refractive action, n, n0: Refractive index, 1, 2 ... Lower diffusion film, 3 ... Upper diffusion film, 10 ... Optical sheet, 11 ... Incident surface, 12 ... Emission surface, 13 ... Light diffusion layer, 14 ... Light reflection layer, 15 ... Opening, 16 ... Unit lens, 17 ... Lens Sheet, 18 ... Adhesive layer, 20 ... Light source, 70 ... Member, 72 ... Unit prism

Claims (11)

In an optical sheet used for illumination light path control in a backlight unit for display,
In order from the incident light incident side, at least,
A light scattering layer that scatters the illumination light to the exit surface side that is the non-incident surface side;
An adhesive layer or an adhesive layer;
Light that is adhered or adhered to the light scattering layer by the adhesive or the pressure-sensitive adhesive, has a highly light-reflective surface facing the emission surface side of the light scattering layer, and is scattered by the light scattering layer A light reflecting layer that reflects the light scattering layer side,
A flat back surface is fixed to the other surface of the light reflection layer, and a lens sheet in which a plurality of unit lenses are arranged on the front surface, and
The optical sheet is characterized in that each of the unit lenses has an opening corresponding to 1: 1 in the light reflecting layer, and the thickness of the adhesive layer or the adhesive layer is thinner than that of the light reflecting layer. The lens sheet is a lenticular sheet having a lens portion in which semi-cylindrical convex cylindrical lenses are arranged in one direction as the unit lens,
When a parallel light beam is incident on the lenticular sheet from the lens unit side, a light-transmitting stripe shape is included so as to include a portion where the incident parallel light beam is collected by the condensing action of the lens unit. The stripe-shaped light reflecting layer having an opening is formed, and the parallel pitch of the semi-cylindrical convex cylindrical lens and the formation pitch of the stripe-shaped opening are formed to be equal to 1: 1. The optical sheet according to claim 1, wherein   The light reflecting portion is formed in a stripe shape so as to form a convex portion on a surface opposite to the lens portion and corresponding to each unit lens of the convex cylindrical lens. Item 3. The optical sheet according to Item 1 or 2.   The optical sheet according to claim 1, wherein the adhesive layer or the pressure-sensitive adhesive layer is any one of an ultraviolet curable resin layer, a pressure-sensitive pressure-sensitive adhesive layer, and a heat-sensitive adhesive layer.   The optical sheet according to claim 1, wherein the adhesive layer or the pressure-sensitive adhesive layer has a structure containing light diffusing fine particles in the layer.   3. The optical sheet according to claim 1, wherein the light reflection layer is formed of any one of a white ink, a metal foil, and a metal vapor deposition layer.   The optical sheet according to claim 1 or 2, wherein the lens sheet is a press-molded body using a thermoplastic resin or a monolithic molded body by extrusion molding.   The optical sheet according to claim 1, wherein the lens sheet has a laminated structure in which the unit lens made of a cured product of a radiation curable resin is polymerized and bonded to the surface of the base sheet.   A backlight unit for a display, comprising at least a direct light source and the optical sheet according to claim 1 on a back surface of an image display element that defines a display image.   A display backlight, comprising: a back surface of an image display element that defines a display image; and at least a surface light source including an edge light source and a light guide plate; and the optical sheet according to claim 1. unit. An image display element comprising a liquid crystal display element that defines a display image according to transmission / shading in pixel units;
A light source by a cold cathode ray tube or LED;
A display comprising the optical sheet according to claim 1.

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