JP4730339B2 - Surface light source device, transmissive display device - Google Patents

Description

  The present invention relates to a direct-type surface light source device and a transmissive display device including the same.

Various surface light source devices have been proposed and put to practical use as surface light sources (backlights) for illuminating a transmissive liquid crystal display or the like from the back. Surface light source devices include an edge light type and a direct type, mainly by converting a light source that is not a surface light source into a surface light source.
For example, the direct type uses a combination of a plurality of diffuser plates and optical sheets having a function of converging light between the light source unit made up of a plurality of arranged light emitters and a liquid crystal panel, etc. It was.

Conventionally, in such a surface light source device, a viewing angle is controlled and luminance unevenness is reduced by combining a light control sheet that can mainly control a light emission angle in one direction and a diffusion sheet having a light diffusing action. (See Patent Document 1). However, due to the diffusing action of the diffusion sheet, the luminance in the front direction is lowered, and a sufficient luminance improvement cannot be obtained.
JP 2004-6256 A

  An object of the present invention is to provide a surface light source device that can efficiently reduce luminance unevenness, has uniform brightness, and has high front luminance, and a transmissive display device including the same.

The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to the Example of this invention is attached | subjected and demonstrated, it is not limited to this.
The invention of claim 1 is a direct-type surface light source device that illuminates the transmissive display unit from the back side, the light source unit (13) that emits illumination light, the light source unit disposed on the output side, and the output side A first light control sheet (14) in which a plurality of first unit lenses (141) formed so as to be convex are arranged in a vertical direction in the usage state of the surface light source device, and the first light A second unit lens (151, 251) arranged on the exit side from the control sheet and formed to be convex on the exit side is arranged in a plurality in the horizontal direction in the usage state of the surface light source device. Light control sheet (15, 25), and the first light control sheet is formed along the convex surface of the first unit lens and scatters light. The first unit lens of the first light control sheet The scattering characteristic due to the scattering component other than the shape of the second light is greater than the scattering characteristic due to the scattering component other than the lens shape of the second unit lens of the second light control sheet, and the thickness (W1) of the first light control sheet. ) Is a surface light source device (12, 13, 14, 15, 25, 16) characterized by being thicker than the thickness (W2) of the second light control sheet.
According to a second aspect of the present invention, in the surface light source device according to the first aspect, the major axis of the first unit lens (141) and the second unit lens (151, 251) is orthogonal to the sheet surface. A surface light source device (12, 13, 14, 15, 25, characterized by being a part of a continuous elliptic cylinder or a part of a spheroid whose major axis is orthogonal to the sheet surface. 16).
According to a third aspect of the present invention, in the surface light source device according to the first or second aspect, the second light control sheet (15) is along a convex surface of the second unit lens (151). A surface that is formed and has a second scattering layer (152) that scatters light, and the first scattering layer (142) has a scattering property larger than that of the second scattering layer. It is a light source device (12, 13, 14, 15, 16).
According to a fourth aspect of the present invention, in the surface light source device according to the third aspect, the first scattering layer (142) and the second scattering layer (152) each contain a diffusing material, The refractive index difference (Δn1) between the diffusing material contained in one scattering layer and the resin serving as the base of the first scattering layer is the difference between the diffusing material contained in the second scattering layer and the second scattering layer. A surface light source device characterized by being larger than a refractive index difference (Δn2) with a base resin. (12, 13, 14, 15, 16).
According to a fifth aspect of the present invention, in the surface light source device according to any one of the first to fourth aspects, the first scattering layer (142) contains a diffusing material, In the surface light source device (12, 13, 14, 15, 25, 16), at least a part of the diffusing material contained in the scattering layer is a particle containing a plurality of fine bubbles therein.
According to a sixth aspect of the present invention, in the surface light source device according to the fifth aspect, the particles are formed using an organic compound (12, 13, 14, 15, 25). 16).
A seventh aspect of the present invention is the surface light source device according to any one of the first to sixth aspects, wherein a pitch at which the first unit lenses (141) are arranged is P1, and the second light source device is the second light source device. The surface light source device (12, 13, 14, 15, 25, 16) is characterized by satisfying a relationship of P2 ≦ P1, where P2 is a pitch at which the unit lenses (151, 251) are arranged.
According to an eighth aspect of the present invention, in the surface light source device according to any one of the first to seventh aspects, the light source section includes a plurality of light emitters (13) arranged adjacent to each other, and the light emitters adjacent to each other. And the distance between the light emitter and at least one of the first light control sheet (14) and the second light control sheet (15, 25) is d, A minimum value of an angle formed by a contact surface (T) with respect to a lens surface at a valley portion between adjacent unit lenses (141) of any one of the sheets and a normal line (H) direction of the sheet surface of any of the sheets. θ, satisfying the relationship of arccos (n × cos (φ + θ)) ≦ θ, φ = arcsin (sin (arctan (L / (2d))) / n) where n is the refractive index of the unit lens. Surface light source device (12,1) , It is a 14,15,25,16).
The invention of claim 9 is illuminated from the back by the surface light source device (12, 13, 14, 15, 25, 16) according to any one of claims 1 to 8 and the surface light source device. A transmissive display device (10, 20).
According to a tenth aspect of the present invention, in the transmissive display device according to the ninth aspect, the pixel pitch of the transmissive display section (11) is P0, the pitch at which the first unit lenses (141) are arranged is P1, The transmission type display device (10, 20) is characterized by satisfying a relationship of P2 ≦ P1 <P0, where P2 is a pitch at which the second unit lenses (151, 251) are arranged.

According to the present invention, the following effects can be obtained.
(1) In the surface light source device according to the present invention, a plurality of first unit lenses that are arranged on the emission side from the light source unit and are convex on the emission side are arranged in the vertical direction in the usage state of the surface light source device. The first light control sheet and the second unit lens that is arranged on the emission side from the first light control sheet and is convex on the emission side are in the horizontal direction when the surface light source device is used. And a plurality of second light control sheets arranged in the light source, the light can be controlled independently in both the vertical direction and the horizontal direction in the usage state of the surface light source device, and the viewing angle can be freely set. be able to.
The first light control sheet is formed along the convex surface of the first unit lens, has a first scattering layer that scatters light, and the lens of the first unit lens of the first light control sheet Since the scattering characteristic due to the scattering component other than the shape is larger than the scattering characteristic due to the scattering component other than the lens shape of the second unit lens of the second light control sheet, in addition to the light convergence effect by the first unit lens, A light diffusing action can be imparted, and the effect of reducing luminance unevenness and improving front luminance can be enhanced. In addition, when the first scattering layer is not present, light emitted from the first light control sheet with a large emission angle outside the desired viewing angle is scattered by the first scattering layer and returned to the light source side. By being reused, it is possible to increase the proportion of light emitted into a desired viewing angle. Therefore, the effect of reducing luminance unevenness and improving front luminance can be increased more efficiently. Furthermore, by using the first light control sheet having a large scattering characteristic due to a scattering component other than the lens shape of the unit lens and the second light control sheet having a small scattering characteristic, the effect of reducing luminance unevenness is increased while being excessively increased. It is possible to suppress a decrease in front luminance due to light scattering.
Since the first light control sheet is thicker than the second light control sheet, the first light control sheet is more rigid than the second light control sheet, and other optical sheets such as the second light control sheet are used. Has the function of holding. In addition, when the first light control sheet is formed of a material having no hygroscopicity, it is difficult to cause a warp that protrudes toward the emission side due to heat from the light source unit, etc., so that it is possible to prevent uneven brightness due to the warp. I can expect. Further, since the second light control sheet is thinner than the first light control sheet, the second light control sheet can be easily formed when the second light control sheet is produced by, for example, extrusion molding.

(2) The first unit lens and the second unit lens may be a part of an elliptic cylinder whose major axis is continuous perpendicular to the sheet surface, or a spheroid whose major axis is orthogonal to the sheet surface. Therefore, the light convergence effect can be enhanced. Further, the design can be easily performed according to the desired convergence effect.

(3) The second light control sheet is formed along the convex shape of the surface of the second unit lens and has the second scattering layer that scatters light. Light emitted outside the angular range can be scattered by the first scattering layer and the second scattering layer, and can be emitted after being corrected to an emission angle within the viewing angle range. Also, by scattering such light and returning it to the light source side for reuse, luminance unevenness can be reduced, or the proportion of light emitted into the desired viewing angle range can be increased to increase the front luminance. Can do.
Since the first scattering layer has a larger scattering characteristic than the second scattering layer, the first scattering layer is diffused by the first scattering layer, and the light emitted from the first scattering layer is returned to the light source unit within the viewing angle range and reused. The ratio is increased and the reused light is incident on a position away from the position where the light is first incident on the first light control sheet. It is done. In addition, when the first scattering layer is not provided, light emitted at a large emission angle can be emitted at an emission angle within the viewing angle range by being scattered by the first scattering layer, thereby improving the front luminance. In addition, unnecessary luminance peaks that occur outside the viewing angle range can be reduced. Further, since the first scattering layer having a large scattering characteristic is formed on the first light control sheet disposed on the light source side, most of the light scattered by the diffusing material is returned to the light source side to thereby return the surface light source device. By reflecting with a reflecting plate or the like, it is possible to more reliably scatter, and to increase the luminance unevenness reduction effect.

(4) The first scattering layer and the second scattering layer each contain a diffusing material, and the refractive index of the diffusing material contained in the first scattering layer and the resin serving as the base of the first scattering layer. Since the difference is larger than the refractive index difference between the diffusing material contained in the second scattering layer and the resin serving as the base of the second scattering layer, the scattering action by the first scattering layer is the second scattering layer. It is larger than the scattering effect by. Therefore, when the first scattering layer does not exist, the light emitted at a large emission angle outside the desired viewing angle by entering the first light control sheet at a large angle or the like is reflected on the first scattering layer. It is greatly scattered by the diffusing material and returned to the light source side, and the rate of reuse is increased. Further, the reused light is incident on the first light control sheet at a position away from the position where the light is first incident, and the ratio of the light that is emitted within a desired viewing angle range is increased. Further, since the first scattering layer having a large scattering characteristic is formed on the first light control sheet disposed on the light source side, most of the light scattered by the diffusing material is returned to the light source side to thereby return the surface light source device. It is possible to scatter more reliably by reflecting the light with a reflector or the like. Thereby, luminance unevenness can be reduced efficiently and luminance within a desired viewing angle range can be improved.
In addition, when the first scattering layer is not provided, light emitted at a large emission angle can be emitted at an emission angle within the viewing angle range by being scattered by the first scattering layer. It is possible to improve and reduce unnecessary luminance peaks that occur outside the viewing angle range.

(5) Since at least a part of the diffusing material contained in the first scattering layer is a particle containing a plurality of fine bubbles inside, the scattering effect by the diffusing material can be increased, and luminance unevenness can be reduced. The effect of improving the front luminance can be enhanced.

(6) Since the particles are formed using an organic compound, fine bubbles can be easily formed.

(7) When the pitch at which the first unit lenses are arranged is P1, and the pitch at which the second unit lenses are arranged is P2, the relationship P2 ≦ P1 is satisfied, so that it is compared with the second light control sheet. Even the first light control sheet having a large thickness can be easily formed while maintaining the convergence effect due to the lens shape of the first unit lens.

(8) At least one of the first light control sheet and the second light control sheet is arccos (n × cos (φ + θ)) ≦ θ, φ = arcsin (sin (arctan (L / (2d) )) / N), the light having a large incident angle to the light control sheet, such as the light emitted from the trough between the unit lenses at a position corresponding to the approximate center between the adjacent light emitters. However, the light is emitted in a direction substantially normal to the sheet surface. Accordingly, it is possible to reduce unevenness in brightness due to the positions of the light emitters such that the positions corresponding to the light emitters are bright and the spaces between the light emitters are dark, and the front luminance can be improved.

(9) Since the transmissive display device includes the surface light source device according to the present invention and a transmissive display unit that is illuminated from the back by the surface light source device, the transmissive display device has little luminance unevenness, is uniformly bright, and has high front luminance. It can be set as a display device, and a good image can be displayed.

(10) When the pixel pitch of the transmissive display unit is P0, the pitch at which the first unit lenses are arranged is P1, and the pitch at which the second unit lenses are arranged is P2, the relationship of P2 ≦ P1 <P0 is established. Since it satisfies, generation | occurrence | production of moire can be reduced and a favorable image | video can be displayed.

  The present invention aims to provide a surface light source device that can efficiently reduce luminance unevenness, has uniform brightness, and has high front luminance, and a transmissive display device including the surface light source device. A plurality of first light control sheets arranged in the vertical direction in the use state of the device, and a plurality of second unit lenses arranged in the horizontal direction in the use state of the surface light source device are arranged on the emission side from the first light control sheet. A second light control sheet arranged, and the first light control sheet has a first scattering layer formed along the surface convex shape of the first unit lens, and scatters light. The scattering characteristic due to the scattering component other than the lens shape of the first unit lens of the first light control sheet is larger than the scattering characteristic due to the scattering component other than the lens shape of the second unit lens of the second light control sheet. The thickness of the light control sheet is the second The formed surface light source device thicker than the thickness of the light control sheet, and was achieved by a transmission type display device including the same.

(First embodiment)
FIG. 1 is a diagram showing a transmissive display device according to a first embodiment of the present invention.
In addition, each figure shown below including FIG. 1 is the figure shown typically, and the magnitude | size, the number, shape, etc. of each part are exaggerated suitably for easy understanding.
In addition, the terms “plate”, “sheet”, “film” and the like are used, but these are generally used in the order of thickness, “plate”, “sheet”, “film”. I am using it. However, since there is no technical meaning in such proper use, the description in the claims is used in the unified description of the sheet. Accordingly, the terms “sheet”, “plate”, and “film” can be appropriately replaced. For example, the light control sheet may be a light control film or a light control plate.
Furthermore, numerical values such as dimensions and material names of each member described in the present specification are examples of the embodiment, and the present invention is not limited thereto, and may be appropriately selected and used.

The transmissive display device 10 of the present embodiment includes an LCD (Liquid Crystal Display) panel 11, a reflector 12, a light emitting tube 13, a first light control sheet 14, a second light control sheet 15, a polarization reflection sheet 16, and the like. And a transmissive liquid crystal display device that illuminates and displays video information formed on the LCD panel 11 from the back side. In addition, as a surface light source device (backlight device) for illuminating the LCD panel 11 from the back, a reflector 12, an arc tube 13, a first light control sheet 14, a second light control sheet 15, and a polarization reflection sheet 16 are provided. Applicable.
The first light control sheet 14, the second light control sheet 15, and the polarization reflection sheet 16 are arranged so that their sheet surfaces are substantially parallel to each other.
In addition, the sheet surface indicates a surface which is a planar direction of the sheet when viewed as the whole sheet in each sheet, and is defined as the same in the following description and in the claims. Used. For example, in the first light control sheet 14, the sheet surface is a surface in the planar direction of the first light control sheet 14 when viewed as the entire first light control sheet 14, and the first light control sheet 14 It is a surface parallel to the incident surface of the sheet 14 (surface on the arc tube 13 side).
In order to facilitate understanding, in the following specification, the vertical direction and the horizontal direction are the vertical direction and the horizontal direction in the usage state of the surface light source device or the transmissive display device, unless otherwise specified. Suppose that

The LCD panel 11 is a transmissive display unit formed by a transmissive liquid crystal display element. In the present embodiment, a diagonal 32 inch size (740 mm × 420 mm) and 1280 × 768 dots can be displayed. In the LCD panel 11, the direction along the longitudinal direction of the arc tube 13 is used as a horizontal direction, and the direction in which the arc tubes 13 are arranged is used as a vertical direction.
The arc tube 13 is a light emitter that forms the light source part of the surface light source device. In the present embodiment, the arc tube 13 is a cold cathode tube of a line light source, and only six are shown in FIG. 1, but in reality, 18 are arranged in parallel at regular intervals of approximately 20 mm. . A reflection plate 12 is provided on the back surface of the arc tube 13.
The reflection plate 12 is provided over the entire surface of the arc tube 13 on the opposite side (back side) from the first light control sheet 14, and diffuses and reflects the illumination light traveling toward the back side, so that the first light control sheet 14. It has a function of making the incident light illuminance uniform evenly in the direction (outgoing direction).

The first light control sheet 14 is arranged on the emission side (LCD panel 11 side) from the arc tube 13, and a plurality of first unit lenses 141 that are convex on the emission side are arranged in the vertical direction. The first light control sheet 14 mainly has a light control function in the vertical direction.
The second light control sheet 15 is arranged on the emission side (LCD panel 11 side) from the first light control sheet 14, and a plurality of second unit lenses 151 that are convex on the emission side are arranged in the horizontal direction. ing. The second light control sheet 15 mainly has a light control function in the horizontal direction.
When viewed from the normal direction of the sheet surface, the first light control sheet 14 and the second light control sheet 15 have the unit lens arrangement directions orthogonal to each other, and the light control directions are the same. Since they are orthogonal to each other, it is possible to independently control light in the two directions of the vertical direction and the horizontal direction in the usage state of the surface light source device, and the viewing angle can be set freely.

A spacer (not shown) is provided between the arc tube 13 and the first light control sheet 14 so that a predetermined interval is provided.
The polarization reflection sheet 16 is a polarization separation sheet that is disposed between the second light control sheet 15 and the LCD panel 11 and has an effect of increasing luminance without narrowing the viewing angle. In this embodiment, it is DBEF (made by Sumitomo 3M Co., Ltd.), and its thickness is 0.4 mm.

Details of the shapes and the like of the first light control sheet 14 and the second light control sheet 15 will be described.
FIG. 2 is an enlarged view of a cross section of the first light control sheet 14 taken along S1-S2 indicated by arrows in FIG.
In the first light control sheet 14, a plurality of first unit lenses 141 formed so as to be convex on the emission side are arranged in the vertical direction.
In the cross section shown in FIG. 2, the first unit lens 141 is a part of an elliptical shape having a major radius a1 = 0.25 mm (250 μm) and a minor radius b1 = 0.12 mm (120 μm). Therefore, the first unit lens 141 is a part of an elliptic cylinder whose major axis is continuous perpendicular to the sheet surface of the first light control sheet 14. The first unit lens 141 has a lens height (a distance from the top to the valley of the first unit lens 141 in the thickness direction) h1 = 0.102 mm (102 μm), and an array pitch P1 = 0. It is formed to be 204 mm (204 μm).
Further, the thickness W1 of the first light control sheet 14 is 1.5 mm, which is larger than the thickness W2 of the second light control sheet 15 described later. In addition, as thickness of the 1st light control sheet | seat 14, it is preferable that it exists in the range of 1.0-2.0 mm from a viewpoint of a moldability or environmental resistance.

The ratio of the major radius a1 to the minor radius b1 of the first unit lens 141 is in the range of a1: b1 = 1.5: 1-3: 1. From the viewpoint of improving the ratio. In the present embodiment, a1: b1 = 2: 1.
Further, the first unit lens 141 has a ratio between the lens height h1 and the pitch P1 of the first unit lens 141 within a range of P1: h1 = 1.8: 1 to 2.2: 1. It is preferable from the viewpoint of achieving both the light condensing effect by the lens shape and the improvement of moldability and environmental resistance. In the present embodiment, P1: h1 = 2: 1.
In the present embodiment, the first unit lens 141 is formed using a PC (polycarbonate) resin having a refractive index of 1.59. As the resin for forming the first unit lens 141, in addition to the PC resin, AS (acrylonitrile-styrene) resin, MS (methacrylate-styrene) resin, PMMA (methyl methacrylate) resin, PET (polyethylene terephthalate). ) Resin, cycloolefin resin, etc. can be used.
Note that the first light control sheet 14 is formed using a material having low hygroscopicity (such as amorphous PET resin), so that a difference in moisture absorption occurs between the front and back of the sheet due to heat from the arc tube 13. This is preferable from the viewpoint of preventing sheet warpage caused by the above.

A first scattering layer 142 containing a diffusing material is formed along the convex shape of the first unit lens 141 on the surface layer inner portion of the first unit lens 141 on the observation surface side (LCD panel 11 side). Yes. The film thickness t1 of the first scattering layer 142 is about 25 μm at a position corresponding to the top of the first unit lens 141.
In FIG. 2, the first scattering layer 142 is shown as being thick near the top of the first unit lens 141 and thin near the valley between the first unit lenses 141. For example, the first unit lens 141 may be formed so that the vicinity of the top is thin and the vicinity of the valley is thick, or the first unit lens 141 is formed with a substantially uniform thickness along the shape of the first unit lens 141. It is good also as a form.
The first scattering layer 142 contains a diffusing material, but the base resin is formed of the same resin as the first unit lens 141 (PC resin in this embodiment).
In the present embodiment, the first light control sheet 14 is formed by extruding two layers of a PC resin layer containing a diffusing material and a PC resin layer not containing a diffusing material, and the PC resin layer side containing the diffusing material during molding. The first unit lens 141 is formed, and the first scattering layer 142 and the portion other than the first scattering layer 142 of the first unit lens 141 can be discriminated by the presence or absence of the diffusing material. ing.

In the present embodiment, multi-bubble beads having a particle diameter r1 = 5 μm formed of an acrylic resin are used as the diffusion material used for the first scattering layer 142. This multi-foam bead is a microbead containing many fine bubbles, and its average refractive index is about 1.27. The diffusing material used for the first scattering layer 142 has a refractive index difference Δn1 of 0.15 or more with the resin that forms the base of the first scattering layer 142, that is, the resin that forms the first unit lens 141. Some are preferable from the viewpoint of obtaining large scattering characteristics. In the present embodiment, Δn1 = 0.32, which is 0.15 or more.
Here, since the multi-bubble beads contain a large number of fine bubbles, the average refractive index was used as the refractive index. This average refractive index is the diameter of the bubbles contained in the multi-bubble beads. When it is sufficiently small with respect to the wavelength, it is an average refractive index when viewed as the whole foamed beads. In this embodiment, since the diameter of the bubbles contained in the multi-bubble beads is sufficiently small with respect to the wavelength of light, the average refractive index is used as the refractive index. When the diameter of the bubbles contained in the multi-bubble beads has a certain size with respect to the wavelength of light, the refractive index of the multi-bubble beads is substantially equal to the refractive index of the bubbles (eg, air) contained therein. , About 1.0.

  The scattering characteristic indicates the degree to which light is scattered by the scattering component, and is used as the same definition in the following description and in the claims. The scattering component is a component that acts to scatter light emitted from an optical sheet or the like, and in the present embodiment, the first light control sheet 14 and the second light control sheet 15 are used as scattering components. Each has a lens shape of the first unit lens 141 and the second unit lens 151, a first scattering layer 142, and a second scattering layer 152 to be described later.

FIG. 3 is an enlarged view of a cross section of the second light control sheet 15 cut along S3-S4 indicated by arrows in FIG.
In the second light control sheet 15, a plurality of second unit lenses 151 formed so as to be convex on the emission side are arranged in the horizontal direction.
In the cross section shown in FIG. 3, the second unit lens 151 is a part of an elliptical shape having a major radius a2 = 0.12 mm (120 μm) and a minor radius b2 = 0.60 mm (60 μm). Therefore, the second unit lens 151 is a part of an elliptic cylinder whose major axis is continuous perpendicular to the sheet surface of the second light control sheet 15. The lens height of the second unit lens 151 is h2 = 0.05 mm (50 μm), and the pitch P2 = 0.10 mm (100 μm) at which the second unit lenses 151 are arranged is formed. Further, the thickness W2 of the second light control sheet 15 is 0.60 mm, which is thinner than the thickness W1 of the first light control sheet 14. The thickness of the second light control sheet 15 is preferably in the range of 0.3 to 1.0 mm from the viewpoint of moldability and environmental resistance.

The ratio of the long radius a2 and the short radius b2 of the second unit lens 151 is in the range of a2: b2 = 1.5: 1 to 3: 1, as in the first unit lens 141. This is preferable from the viewpoint of improving the light collecting property of the second unit lens 151. In the present embodiment, a2: b2 = 2: 1.
The ratio between the lens height h2 of the second unit lens 151 and the pitch P2 is P2: h2 =
It is preferable that it is in the range of 1.8: 1 to 2.2: 1 from the viewpoint of improving moldability and environmental resistance while maintaining the light collecting action by the lens shape of the second unit lens 151. . In the present embodiment, P2: h2 = 2: 1.
In the present embodiment, the second unit lens 151 is formed using AS resin having a refractive index of 1.57. As the resin for forming the second unit lens 151, PC resin, MS resin, PMMA resin, PET resin, cycloolefin resin, or the like can also be used.

A second scattering layer 152 containing a diffusing material is formed along the convex shape of the second unit lens 151 on the surface layer inner portion of the second unit lens 151 on the observation surface side (LCD panel 11 side). Yes. The film thickness t <b> 2 of the second scattering layer 152 is about 25 μm at a position corresponding to the top of the second unit lens 151.
In FIG. 3, the second scattering layer 152 is shown as being thick near the top of the second unit lens 151 and thin near the valley between the second unit lenses 151. For example, the second unit lens 151 may be formed so that the vicinity of the top of the second unit lens 151 is thin and the vicinity of the valley is thick, or the second unit lens 151 is formed with a substantially uniform thickness along the shape of the second unit lens 151. It is good also as a form.
In the present embodiment, the second light control sheet 15 is formed by two-layer extrusion forming, like the first light control sheet 14, and the second scattering layer 152 contains a diffusing material. However, since the base resin is formed of the same resin (AS resin) as that of the second unit lens 151, the second scattering layer 152 and the second unit lens 151 can be formed with or without a diffusing material. It has a form in which a portion other than the second scattering layer 152 can be distinguished.

In the present embodiment, resin beads having a particle diameter r2 = 5 μm formed of acrylic resin are used as the diffusion material used for the second scattering layer 152. The refractive index of this resin bead is 1.49. As in the present embodiment, the diffusing material used for the second scattering layer 152 is a fine bead made of resin or the like, and the resin serving as the base of the second scattering layer 152, that is, the second unit lens 151. Those having a refractive index difference Δn2 with respect to the resin forming 0.01 are preferably 0.01 or more and 0.12 or less from the viewpoint of scattering characteristics and the like.
As the diffusing material, a light scattering action cannot be obtained unless a difference in refractive index with the base resin containing the diffusing material is 0.01 or more. In addition, the second scattering layer 152 preferably has a smaller scattering characteristic than the first scattering layer 142 described above, from the viewpoint of improving the front luminance and controlling the viewing angle. Therefore, the refractive index difference Δn2 between the diffusing material used for the second scattering layer 152 and the resin serving as the base of the second scattering layer 152 is preferably within the above range. In the present embodiment, Δn2 = 0.08, which satisfies this range.

Table 1 summarizes the shapes and the like of the first light control sheet 14 and the second light control sheet 15.
In the present embodiment, of the first light control sheet 14 and the second light control sheet 15, the thickness W1 of the first light control sheet 14 disposed on the arc tube 13 side is disposed on the LCD panel 11 side. The thickness of the second light control sheet 15 is made thicker than W2. Thereby, the 1st light control sheet 14 can hold | maintain the various optical sheets arrange | positioned at the LCD panel 11 side from the 1st light control sheet 14, such as the 2nd light control sheet 15. FIG.

Next, the pitch P1 at which the first unit lenses 141 of the first light control sheet 14 are arranged and the pitch P2 at which the second unit lenses 151 of the second light control sheet 15 are arranged are as follows. For pixel pitch P0,
P2 ≦ P1 <P0 (Formula 1)
Satisfying this relationship is preferable from the viewpoints of moire reduction, unit lens convergence, ease of moldability, and the like.
For example, when P1 ≧ P0, moire tends to occur. Therefore, it is preferable that P1 <P0.

Usually, in a display device or the like, the viewing angle in the vertical direction is regarded as important, and the light condensing action in the vertical direction is regarded as important. Therefore, the first unit lens 141 having the light controlling function in the vertical direction is used. The shape is desired to have a small ratio of the arrangement pitch to the lens height h1 and high accuracy.
In general, when a light control sheet with a plurality of unit lenses arranged is manufactured by extrusion molding, if the thickness is increased, it is difficult to manufacture both the lens shape and the pitch with high accuracy from the viewpoint of moldability. is there. In other words, it is necessary to select either the lens shape accuracy to increase the pitch, or the pitch accuracy to be increased to make the lens shape a gentle lens shape with a low lens height. .
Therefore, in the present embodiment, the first light control sheet 14 is thicker than the second light control sheet 15 and has a light control function in the vertical direction. In order to achieve both optical properties, it is preferable to increase the accuracy of the lens shape of the first unit lens 141 and to set P2 ≦ P1 with respect to the arrangement pitch.
On the other hand, in the second light control sheet 15 arranged on the LCD panel 11 side, the arrangement pitch P2 of the second unit lenses 151 is desired to be fine and highly accurate from the viewpoint of preventing moire.

From this point of view, it is desirable that the pitches P1, P2, and P0 satisfy (Equation 1). In this embodiment, P1 = 204 μm, P2 = 100 μm, and P0 = 510 μm, which satisfies (Equation 1).
In addition, as for the 2nd light control sheet | seat 15, it is more preferable that the pitch P2 is 1/5 or less of the pixel pitch P0 from a viewpoint of improving the effect of moire prevention. In this embodiment, the pitch P2 is smaller than 102 μm, which is 1/5 of the pixel pitch P0, and a high moire prevention effect can be expected. In addition, since moire can be reduced by this, it is not necessary to provide an optical sheet or the like having a light diffusing action on the LCD panel side from the second light control sheet 15, and it is possible to prevent a decrease in luminance and reduce production costs. it can.

The effects obtained by providing the first scattering layer 142 and the second scattering layer 152 on the first light control sheet 14 and the second light control sheet 15, respectively, are as follows.
In the case where the light control sheet is not provided with a scattering layer, light incident on the light control sheet at a large incident angle, such as light incident on a unit lens formed at a position substantially corresponding to the center between the arc tubes 13, is light control sheet. Tends to be emitted at a large emission angle. Even when the incident angle is small, the light traveling along the surface shape of the unit lens by being totally reflected at the unit lens interface or the like tends to be emitted from the light control sheet at a large emission angle.
Therefore, the first scattering layer 142 and the second unit lens 151 formed on the first light control sheet 14 and the second light control sheet 15 along the surface shape of the first unit lens 141, respectively. By forming the second scattering layer 152 formed along the surface shape, the light that is emitted at a large emission angle has a longer distance through each scattering layer and is scattered a lot. Accordingly, when each scattering layer is not provided, a part of the light emitted at a large emission angle is corrected to a small emission angle and emitted from each light control sheet, and another part of the light is emitted from the arc tube The light that is returned to the side 13 and reused and emitted at a large emission angle can be negligible. Accordingly, it is possible to reduce luminance unevenness, improve front luminance, and reduce unnecessary luminance peaks that occur outside the viewing angle range.

Further, the first light control sheet 14 uses multifoam beads as a diffusing material used for the first scattering layer 142, and the refractive index difference Δn1 between the polyfoam beads and the resin forming the first unit lens 141. = 0.32. On the other hand, the second light control sheet 15 uses resin beads as a diffusion material used for the second scattering layer 152, and the difference in refractive index between the resin beads and the resin forming the second unit lens 151. Δn2 = 0.08.
Therefore, Δn2 <Δn1, and the light scattering characteristics of the diffusing material are greater in the first scattering layer 142.

Further, the scattering characteristics when viewed as the entire scattering layer containing the diffusing material, i.e., regarding the size of the scattering characteristics due to the scattering components other than the lens shape of each unit lens in each light control sheet, When the refractive index difference between the diffusing material contained and the resin serving as the base of the scattering layer is Δn and the particle size of the diffusing material is r, the value of Δn / r can be used to compare the size of the scattering characteristics. it can.
In each scattering layer, the larger the particle size r of the diffusing material, the smaller the ratio of light hitting the diffusing material, the smaller the ratio of scattered light when viewed as the entire scattering layer, and the lower the scattering characteristics. Conversely, the smaller the particle size of the diffusing material, the greater the proportion of light that strikes the diffusing material, and the greater the scattering characteristics when viewed as the entire scattering layer. Therefore, it can be said that the magnitude of the scattering characteristics when viewed as the entire scattering layer is proportional to the refractive index difference Δn and inversely proportional to the particle size r of the diffusing material.

Therefore, the larger the value of Δn / r, the larger the scattering characteristics. By comparing the values of Δn / r of the scattering layers, the scattering characteristics of the scattering layers can be compared.
In this embodiment, the refractive index differences Δn1 = 0.32 and Δn2 = 0.08 of each scattering layer, and the particle diameters r1 = 5 μm and r2 = 5 μm of each diffusing material, Δn1 / r1 = 0.32 / 5 = 0.064 and Δn2 / r2 = 0.08 / 5 = 0.016. Therefore, Δn1 / r1> Δn2 / r2, and the scattering characteristics of the entire first scattering layer 142 (scattering characteristics due to scattering components other than the lens shape of the first unit lens 141 of the first light control sheet 14) are: It is larger than the scattering characteristics of the entire second scattering layer 152 (scattering characteristics due to scattering components other than the lens shape of the second unit lens 151 of the second light control sheet 15). In the present embodiment, since the particle diameters of the diffusing materials are equal (r1 = 5 μm, r2 = 5 μm), the scattering characteristics of the entire scattering layer can be compared depending on the difference in refractive index Δn1 and Δn2.
By disposing the first scattering layer 142 having such a large scattering characteristic on the first light control sheet 14 on the arc tube 13 side, the ratio of light scattered and reused by the first scattering layer 142 is increased. Therefore, luminance unevenness can be reduced and front luminance can be improved. Furthermore, since the thing with a low scattering characteristic (in this embodiment, resin bead) can be used as a diffuser of the 2nd light control sheet 15 by the side of the LCD panel 11, the fall of a brightness | luminance can be prevented.
Further, by using a combination of the first light control sheet 14 having a large scattering characteristic due to a scattering component other than the lens shape of the unit lens and the small second light control sheet 15, the front luminance is reduced due to excessive scattering. It is possible to increase the effect of reducing luminance unevenness while suppressing front luminance.

It should be noted that most of the light incident on each light control sheet from a direction substantially normal to the sheet surface or incident at a small incident angle is incident on each scattering layer substantially perpendicularly or at a small incident angle, and from each unit lens. The light exits in a direction substantially normal to the sheet surface or exits within the viewing angle range. Therefore, such light has a short distance to pass through each scattering layer and is less affected by the scattering layer.
However, most of the light that is desired to be scattered by each scattering layer, that is, light that is emitted at a large emission angle, travels near the surface layer of the unit lens by being totally reflected at the interface of each unit lens. Regardless of the film thickness, the distance through each scattering layer is long, and the influence of the scattering layer is large.
Therefore, in this embodiment, the size of the scattering characteristic is defined by the refractive index difference Δn between the diffusing material of each scattering layer and the base resin, or the ratio Δn / r between the refractive index difference and the particle size of the diffusing material. is doing.

FIG. 4 is a diagram illustrating the relationship between the first light control sheet 14 and the arc tube 13. Note that the first scattering layer 142 is omitted for easy understanding.
From the viewpoint of preventing luminance unevenness according to the position of the arc tube 13, the first light control sheet 14 sets the distance between adjacent arc tubes 13, that is, the pitch at which the arc tubes 13 are arranged to L, and the arc tube 13. The distance between the first light control sheet 14 and the first light control sheet 14 is d, and the contact surface T with the lens surface of the first unit lens 141 in the valley between the adjacent first unit lenses 141 of the first light control sheet 14 and the first light control sheet 14 When the minimum value of the angle formed by the normal H direction of the sheet surface of one light control sheet 14 is θ and the refractive index of the first unit lens 141 is n, it is desirable to satisfy the following two expressions.
arccos (n × cos (φ + θ)) ≦ θ (Formula 2)
φ = arcsin (sin (arctan (L / (2d))) / n) (Formula 3)

In the present embodiment, as shown in FIG. 1, arc tubes 13 that are line light sources as light emitters are arranged in the light source unit at predetermined intervals in the vertical direction. In general, in a surface light source device or the like using such a light source unit, linear luminance unevenness corresponding to the position of the light emitter is likely to occur.
The second light control sheet 15 mainly has a light control function in the horizontal direction by the second unit lenses 151 arranged in the horizontal direction, and can be said to have the second scattering layer 152. However, the control action in the vertical direction is weak.
On the other hand, since the first light control sheet 14 has a control action in the vertical direction that is the arrangement direction of the arc tubes 13, the arc tube 13 diffuses and converges the light from the arc tubes 13 in the vertical direction. The effect of reducing the luminance unevenness corresponding to the position 13 can be obtained.

According to (Expression 3), the angle φ indicates that the light L1 emitted from the most valley portion between the adjacent first unit lenses 141 formed at a position corresponding to the approximate center between the arc tubes 13 is the first light control. This is the angle formed with the normal H direction of the sheet surface within the sheet 14 (see FIG. 4).
Further, (Equation 2) is obtained when the light emitted from the arc tube 13 is emitted from a valley between adjacent first unit lenses 141 formed at a position corresponding to the approximate center between the arc tubes 13. Refracted by the lens shape of the first unit lens 141 and emitted in the normal H direction of the sheet surface (light L1), or in the normal H direction of the sheet surface as light L3 indicated by a broken line in FIG. This means that the light is emitted in a direction that makes a slight angle with respect to the direction (hereinafter, these directions are referred to as substantially normal directions).

The minimum value θ of the angle between the light emitted from the most valley portion between the adjacent first unit lenses 141 formed at a position corresponding to the approximate center between the arc tubes 13 and the contact surface T with the lens surface is expressed by When 2) is not satisfied, the light emitted from the most valley portion between the first unit lenses 141 is emitted from the first light control sheet 14 at a large emission angle (light L2). As a result, the gap between the arc tubes 13 becomes dark, and brightness unevenness occurs in which the position corresponding to the arc tube 13 becomes bright.
However, when the minimum value θ satisfies (Equation 2), the light most emitted from the trough is emitted in the substantially normal direction of the first light control sheet 14 (light L1 and light L3).
Therefore, in the first light control sheet 14, when the above (Expression 2) and (Expression 3) are satisfied, light is not emitted at a large emission angle between the arc tubes 13. The light can be emitted in the line direction. Therefore, luminance unevenness corresponding to the position of the arc tube 13 can be reduced.
When the first light control sheet 14 satisfies (Expression 2) and (Expression 3), the light L1 shown in FIG. 4 is incident substantially perpendicular to the first scattering layer 142 or at a small incident angle. The incident distance through the first scattering layer 142 is short, and the influence of the first scattering layer 142 is small.

According to the present embodiment, the following effects can be achieved.
(1) Since the luminance uniformity can be efficiently reduced and the luminance unevenness can be improved and the front luminance can be improved, there is little luminance irregularity, the brightness is uniform, and the surface light source device having a high front luminance, a transmission type It can be a display device.
(2) When the first light control sheet 14 and the second light control sheet 15 are viewed from the normal direction of the sheet surface, the arrangement directions of the unit lenses are orthogonal, and the light control direction is Since they are arranged so as to be orthogonal to each other, light can be easily controlled in two directions, ie, a vertical direction and a horizontal direction, and an optimum viewing angle can be obtained.
(3) Since the first scattering layer 142 and the second scattering layer 152 are provided, the light emitted from each light control sheet at a large emission angle is scattered and returned to the light source side for reuse, or the viewing angle. The emission angle can be corrected to an emission angle within the range. Accordingly, luminance unevenness can be reduced and front luminance can be improved.

(4) Since the first scattering layer 142 contains, as a diffusing material, beads having a large refractive index difference Δn1 with the resin forming the first unit lens 141, the first scattering layer 142 is compared with the second scattering layer 152. Thus, the first scattering layer 142 having a large scattering characteristic is provided on the first light control sheet 14 on the arc tube 13 side. Accordingly, if the first scattering layer 142 is not provided, the light emitted from the first unit lens 141 in a direction greatly deviating with respect to the normal direction of the sheet surface is caused by the first scattering layer 142. It is possible to increase the proportion of light to be reused by scattering and returning to the arc tube 13 side. Therefore, it is possible to obtain a bright surface light source device and a transmissive display device that have a more uniform brightness and no luminance unevenness. Further, since light emitted from the first unit lens 141 in a direction greatly deviating from the normal direction of the sheet surface is scattered, an unnecessary luminance peak generated outside the viewing angle range can be reduced.

(5) Since the first light control sheet 14 is thicker than the second light control sheet 15, other optical sheets such as the second light control sheet 15 can be held.
(6) Since the first light control sheet 14 and the second light control sheet 15 satisfy (Equation 1), moire or the like does not occur and can be easily manufactured.
(7) Since the first light control sheet 14 satisfies (Expression 2) and (Expression 3), from the valley between the adjacent first unit lenses 141 at a position corresponding to the approximate center between the arc tubes 13. The light emitted in the substantially normal direction of the sheet surface can be increased, the luminance in the front direction can be improved, and the luminance unevenness corresponding to the position of the arc tube 13 can be reduced.

(Second Embodiment)
FIG. 5 is a diagram showing a transmissive display device according to a second embodiment of the present invention.
The transmissive display device 20 of the second embodiment has substantially the same form as the transmissive display device 10 of the first embodiment, except that the form of the second light control sheet 25 is different. Therefore, the same reference numerals are given to the portions that perform the same functions as those in the first embodiment described above, and repeated descriptions are omitted as appropriate.
The transmissive display device 20 of the second embodiment includes an LCD panel 11, a reflecting plate 12, an arc tube 13, a first light control sheet 14, a second light control sheet 25, and a polarization reflecting sheet 16.
The 2nd light control sheet 25 is a form substantially the same as the 2nd light control sheet 15 shown in 1st Embodiment except the point which is not provided with the 2nd scattering layer containing a diffuser. In the second light control sheet 25 of the present embodiment, a plurality of second unit lenses 251 formed so as to be convex on the emission side are arranged in the horizontal direction. The second unit lens 251 has substantially the same shape as the second unit lens 151 shown in the first embodiment, but does not include the second scattering layer.
According to this embodiment, since the 2nd light control sheet 25 is not provided with the 2nd scattering layer, manufacture is easy and production cost can be held down.

(Deformation)
Without being limited to the embodiments described above, various modifications and changes are possible, and these are also within the scope of the present invention.
(1) In each embodiment, an example in which the arc tube 13 that is a line light source is arranged in a one-dimensional direction as a light emitter has been shown. A light emitter such as an LED (Light Emitting Diode) may be used. In this case, in addition to the first light control sheet 14, it is preferable that the second light control sheets 15 and 25 also satisfy (Expression 2) and (Expression 3) from the viewpoint of preventing luminance unevenness.

(2) In each embodiment, the first unit lens 141 has an example in which the ratio between the arrangement pitch P1 and the lens height h1 is P1: h1 = 2: 1. The lens may have a gentle lens shape in which the ratio of the lens height h1 to the arrangement pitch P1 is small in accordance with a desired light condensing property in the vertical direction. By setting it as such a form, a moldability can be improved.

(3) In each embodiment, although the 1st scattering layer 142 showed the example containing a polyfoam bead, it is not restricted to this, Resin used as a base, ie, resin which forms the 1st unit lens 141, The refractive index difference Δn1 may be a diffusing material with a large refractive index difference of 0.15 or more. For example, glass beads containing bubbles, inorganic fine particles such as titanium oxide and barium oxide, titanium oxide, etc. You may use the bead containing etc.

(4) In each embodiment, the first unit lens 141 and the second unit lenses 151 and 251 are examples of a part of an elliptic cylinder whose major axis is continuous perpendicular to the sheet surface. For example, the long axis may be a part of a spheroid whose axis is perpendicular to the sheet surface.

(5) In each embodiment, the example in which the polarization reflection sheet 16 is provided between the second light control sheets 15 and 25 and the LCD panel 11 has been described. However, the present invention is not limited to this. In addition, a fine uneven shape (matte shape), a diffusion sheet coated with a diffusion material, or the like may be arranged on the surface on the emission side to further enhance the luminance unevenness prevention effect. Further, no optical sheet is provided between the second light control sheet 15 and the LCD panel 11, and the reflector 12, the arc tube 13, the first light control sheet 14, the second light control sheet 15 or the second light control sheet 15. The surface light source device may be configured by the light control sheet 25.

(6) In each embodiment, although the 1st unit lens 141 and the 2nd unit lens 151,251 showed the example which consists of one type of lens shape, it is not restricted to this, For example, from multiple types of lens It is good also as a unit lens.

1 is a diagram showing a first embodiment of a transmissive display device according to the present invention. It is the enlarged view of the cross section which cut | disconnected the 1st light control sheet | seat 14 by S1-S2 shown by the arrow in FIG. It is the enlarged view of the cross section which cut | disconnected the 2nd light control sheet | seat 15 by the S3-S4 cross section shown by the arrow in FIG. FIG. 3 is a diagram showing a relationship between a first light control sheet 14 and an arc tube 13. It is a figure which shows 2nd Embodiment of the transmissive display apparatus by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,20 Transmission type display apparatus 11 LCD panel 12 Reflector 13 Light emission tube 14 1st light control sheet 141 1st unit lens 142 1st scattering layer 15,25 2nd light control sheet 151,251 2nd Unit lens 151 Second scattering layer 16 Polarized reflection sheet

Claims (10)

A direct-type surface light source device that illuminates a transmissive display unit from the back,
A light source that emits illumination light;
A first light control sheet in which a plurality of first unit lenses arranged on the emission side from the light source unit and formed to be convex on the emission side are arranged in a vertical direction in the usage state of the surface light source device; ,
A second unit lens that is arranged on the emission side from the first light control sheet and is formed to be convex on the emission side is arranged in a plurality in the horizontal direction in the usage state of the surface light source device. A light control sheet;
With
The first light control sheet has a first scattering layer that is formed along the convex surface shape of the first unit lens and scatters light.
The scattering characteristic due to the scattering component other than the lens shape of the first unit lens of the first light control sheet is the scattering characteristic due to the scattering component other than the lens shape of the second unit lens of the second light control sheet. Bigger,
The thickness of the first light control sheet is thicker than the thickness of the second light control sheet;
A surface light source device. The surface light source device according to claim 1,
The first unit lens and the second unit lens may be a part of an elliptic cylinder whose major axis continues perpendicular to the sheet surface, or a spheroid whose major axis is perpendicular to the sheet surface. Being part of,
A surface light source device. In the surface light source device according to claim 1 or 2,
The second light control sheet has a second scattering layer that is formed along the surface convex shape of the second unit lens and scatters light.
The first scattering layer has greater scattering characteristics than the second scattering layer;
A surface light source device. The surface light source device according to claim 3,
The first scattering layer and the second scattering layer each contain a diffusing material,
The difference in refractive index between the diffusion material contained in the first scattering layer and the resin serving as the base of the first scattering layer is the base of the diffusion material contained in the second scattering layer and the second scattering layer. Is larger than the refractive index difference with the resin
A surface light source device. In the surface light source device according to any one of claims 1 to 4,
The first scattering layer contains a diffusing material;
At least a part of the diffusing material contained in the first scattering layer is a particle containing a plurality of fine bubbles therein;
A surface light source device. The surface light source device according to claim 5,
The particles are formed using an organic compound;
A surface light source device. The surface light source device according to any one of claims 1 to 6,
When the pitch at which the first unit lenses are arranged is P1, and the pitch at which the second unit lenses are arranged is P2,
P2 ≦ P1
Satisfying the relationship
A surface light source device. In the surface light source device according to any one of claims 1 to 7,
The light source unit has a plurality of light emitters arranged, and a distance between adjacent light emitters is L,
The distance from the light emitter to at least one of the first light control sheet and the second light control sheet is d, and the lens surface in the valley between adjacent unit lenses of any of the sheets When the minimum value of the angle formed by the contact surface and the normal direction of the sheet surface of any one of the sheets is θ, and the refractive index of the unit lens is n,
arccos (n × cos (φ + θ)) ≦ θ
φ = arcsin (sin (arctan (L / (2d))) / n)
Satisfying the relationship
A surface light source device. A surface light source device according to any one of claims 1 to 8,
A transmissive display unit illuminated from the back by the surface light source device;
A transmissive display device. The transmissive display device according to claim 9,
When the pixel pitch of the transmissive display unit is P0, the pitch at which the first unit lenses are arranged is P1, and the pitch at which the second unit lenses are arranged is P2.
P2 ≦ P1 <P0
Satisfying the relationship
A transmissive display device characterized by the above.

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