JP2010044377A - Light beam deflection structure plate, surface light source device, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light beam deflecting structure plate capable of emitting uniform light with high luminance and without unevenness in luminance, not only in the center area but also in a corner area. <P>SOLUTION: The light beam deflecting structure plate 3 consists of a light-transmitting plate with a rectangular shape in a plan view which is provided, on one side thereof, with a concavoconvex pattern portion 4, formed by providing a plurality of quadrangular pyramid protrusions 6, and is characterized in that: bases 6d of adjoining quadrangular pyramid protrusions 6 are arranged, in such a form as the bases touch each other on the respective sides 6c thereof; the vertical angle θ of the quadrangular pyramid protrusion 6 is 45 to 150 degrees; and the angle (acute angle), formed by the base side 6c of the quadrangular pyramid protrusion 6 and the sides 41, 42 constituting the rectangular shape of the light-transmitting plate, is in a range of 40 to 50 degrees. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention can display a light deflection structure plate and a surface light source device capable of emitting uniform light with little brightness unevenness not only in a central area but also in a corner area, and a high brightness image with less brightness unevenness in all areas. The present invention relates to a liquid crystal display device.

  In this specification and claims, the term “vertical angle of the quadrangular pyramid convex portion” means a cut surface when the quadrangular pyramidal convex portion is cut by a plane passing through a pair of opposing hypotenuses among the four hypotenuses. Means the apex angle of the triangle.

  As a light source for a backlight of a liquid crystal television, it has been proposed to use an LED (light emitting diode) instead of a conventional cold cathode fluorescent tube (see Non-Patent Document 1). That is, it has been proposed to use a red LED, a green LED, and a blue LED as a backlight light source of a liquid crystal television. Such a liquid crystal display device using LEDs of three colors R (red), G (green), and B (blue) as a backlight light source can increase the color reproduction range and expand the color reproduction range. Because it has advantages such as being not used and being friendly to the global environment, having low power consumption, and having a long life, it has attracted a great deal of attention.

  By the way, in the direct type system used in the backlight of the liquid crystal television, the luminance directly above the light source is high, but the luminance gradually decreases from the position directly above to the intermediate position of the adjacent light sources. That is, there is a problem that luminance unevenness occurs.

  Therefore, when an LED or the like is used as the light source of the surface light source device, it has been proposed to provide a large number of quadrangular pyramid protrusions on the light exit surface of the light diffusion plate arranged on the front side of the light source (Patent Document 1). reference). By adopting such a configuration, light with less luminance unevenness can be emitted.

"Backlight technology for liquid crystal display-Liquid crystal lighting system and materials-", published by CMMC, August 31, 2006, p. 148-149

JP 2007-163810 A

  However, the conventional surface light source device has a problem that the four corner portions (four corner portions) of the rectangular light emission surface are clearly darker than other regions. That is, there is a problem that uniform light with little unevenness in luminance cannot be emitted in the entire region of the light emitting surface.

  The present invention has been made in view of such a technical background, and an optical deflection structure plate and a surface light source device capable of emitting uniform light with little luminance unevenness not only in the central region but also in the corner region with high luminance. The purpose is to provide.

  In order to achieve the above object, the present invention provides the following means.

[1] A light transmission plate having a rectangular shape in plan view in which a concavo-convex shape portion formed by projecting a plurality of quadrangular pyramid convex portions is provided on one side,
The bottom surfaces of the adjacent quadrangular pyramidal protrusions are arranged in a manner in which they touch each other at their respective bottom sides,
The apex angle of the quadrangular pyramidal protrusion is 45 to 150 degrees,
An angle (acute angle) formed by a base of the quadrangular pyramidal protrusion and a rectangular component side of the light transmission plate is in a range of 40 to 50 degrees.

  [2] The light deflection structure plate according to item 1 above, wherein the pitch interval between adjacent quadrangular pyramidal protrusions is 20 to 500 μm.

  [3] The light deflection structure plate according to item 1 or 2, wherein the total light transmittance is 70 to 95%.

  [4] The light deflecting structure plate according to any one of items 1 to 3, the plurality of point light sources disposed on the back side of the light deflecting structure plate, and disposed on the back side of the plurality of light sources. A surface light source device, comprising: a light reflection plate, wherein the light deflection structure plate is disposed such that a surface on which the uneven portion is formed is on a front surface side.

  [5] The light deflection structure plate according to any one of items 1 to 3, the plurality of point light sources arranged on the back side of the light deflection structure plate, and the back side of the plurality of light sources. A light reflection plate, and a light diffusion sheet disposed on the front side of the light deflection structure plate, wherein the surface of the light deflection structure plate on which the concavo-convex shape portion is formed is disposed on the front side. A surface light source device.

  [6] The light deflection structure plate according to any one of items 1 to 3, the plurality of point light sources arranged on the back side of the light deflection structure plate, and the back side of the plurality of light sources. A light reflection plate and a liquid crystal panel disposed on the front side of the light deflection structure plate, wherein the surface on which the concavo-convex shape portion is formed on the light deflection structure plate is disposed on the front side A liquid crystal display device.

  [7] The light deflection structure plate according to any one of items 1 to 3, the plurality of point light sources disposed on the back side of the light deflection structure plate, and the back surface side of the plurality of light sources. A light reflecting plate, a liquid crystal panel disposed on a front side of the light deflection structure plate, and a light diffusion sheet disposed between the liquid crystal panel and the light deflection structure plate, wherein the uneven shape in the light deflection structure plate A liquid crystal display device, wherein the surface on which the portion is formed is disposed on the front side.

  In the invention of [1], the concave-convex shape portion formed by projecting a plurality of quadrangular pyramid convex portions is composed of a light transmission plate having a rectangular shape in plan view provided on one side, and the bottom surfaces of adjacent quadrangular pyramidal convex portions are They are arranged in contact with each other at their respective bottom sides, the apex angle of the quadrangular pyramidal projections is 45 to 150 degrees, and the angle (acute angle) formed by the base of the quadrangular pyramid convex portions and the rectangular component side of the light transmission plate ) Is in the range of 40 to 50 degrees, it is possible to emit uniform light with little luminance unevenness with high luminance not only in the central region but also in the four corners (four corners).

  In the invention of [2], since the pitch interval between the adjacent quadrangular pyramidal projections is 20 to 500 μm, it is possible to sufficiently prevent the top of the quadrangular pyramidal projections from being visually observed, and to include the corner region. Thus, luminance unevenness can be further reduced in all regions.

  In the invention [3], since the total light transmittance is set to 70 to 95%, the luminance unevenness can be sufficiently reduced in the entire region including the corner region.

  In the invention of [4], the light deflection structure plate according to any one of [1] to [3], a plurality of point light sources arranged on the back side of the light deflection structure plate, and the back surfaces of the plurality of light sources A light reflecting plate disposed on the side, and the surface on which the concave and convex portions are formed on the light deflection structure plate is disposed on the front side, so that not only in the central region but also in the corner region Provided is a surface light source device capable of emitting uniform light with little luminance unevenness with high luminance.

  In the invention of [5], the light deflection structure plate according to any one of [1] to [3], a plurality of point light sources disposed on the back side of the light deflection structure plate, and the back surfaces of the plurality of light sources The light reflecting plate disposed on the side and the light diffusion sheet disposed on the front side of the light deflection structure plate are arranged so that the surface on which the concave and convex portions are formed on the light deflection structure plate is the front side. Therefore, there is provided a surface light source device capable of emitting uniform light with little luminance unevenness with high luminance not only in the central region but also in the corner region.

  In the invention of [6], the light deflection structure plate according to any one of [1] to [3], a plurality of point light sources disposed on the back side of the light deflection structure plate, and the back surfaces of the plurality of light sources And a liquid crystal panel disposed on the front side of the light deflection structure plate, and the surface on which the concave and convex portions are formed on the light deflection structure plate is disposed on the front side. Therefore, there is provided a liquid crystal display device capable of displaying a high quality image with little luminance unevenness with high luminance not only in the central region but also in the corner region.

  In the invention of [7], the light deflection structure plate according to any one of [1] to [3], a plurality of point light sources disposed on the back side of the light deflection structure plate, and the back surfaces of the plurality of light sources A light reflecting plate disposed on the front side, a liquid crystal panel disposed on the front side of the light deflecting structure plate, and a light diffusion sheet disposed between the liquid crystal panel and the light deflecting structure plate. Since the surface on which the shape part is formed is arranged on the front side, there is provided a liquid crystal display device capable of displaying a high-quality image with little luminance unevenness not only in the center area but also in the corner area with high brightness. Is done.

1 is a schematic view showing an embodiment of a liquid crystal display device according to the present invention. It is a top view which shows the arrangement | positioning aspect of the light source in the liquid crystal display device of FIG. It is a perspective view which shows one Embodiment of the optical deflection | deviation structure board based on this invention. It is a top view of the light deflection | deviation structure board of FIG. It is sectional drawing of the XX line in FIG. It is an expansion perspective view of the quadrangular pyramid convex part which comprises the uneven | corrugated shaped part of the light deflection | deviation structure board of FIG. It is a conceptual diagram which shows 4 division | segmentation of the light source image by the quadrangular pyramid convex part in the light deflection | deviation structure board of FIG. It is a schematic diagram which shows other embodiment of the liquid crystal display device based on this invention. It is explanatory drawing (sectional drawing) of a transfer rate. It is a conceptual diagram which shows four division of the light source image by the quadrangular pyramid convex part in the light deflection | deviation structure board of the comparative example 2. FIG. It is sectional drawing which shows the light deflection | deviation structure board of the comparative example 3. It is a luminance distribution graph for demonstrating the calculation method of luminance uniformity. It is a top view for demonstrating the corner | angular part (corner part) area | region of a light deflection | deviation structure board.

  An embodiment of a liquid crystal display device according to the present invention is shown in FIG. In FIG. 1, (30) is a liquid crystal display device, (11) is a liquid crystal cell, (12) and (13) are polarizing plates, and (1) is a surface light source device (backlight). Polarizing plates (12) and (13) are respectively arranged on the upper and lower sides of the liquid crystal cell (11), and a liquid crystal panel (20) as an image display unit is constituted by these constituent members (11), (12) and (13). Yes.

  The said surface light source device (1) is arrange | positioned at the lower surface side (back side) of the polarizing plate (13) below the said liquid crystal panel (20). The surface light source device (1) is a thin box-shaped lamp box (5) having a rectangular shape in plan view and having an open upper surface (front surface), and a lamp box (5) spaced apart from each other. A plurality of point light sources (2), a light deflection structure plate (3) disposed on the upper side (front side) of the plurality of point light sources (2), and a front side of the light deflection structure plate (3) And a light diffusing sheet (9) disposed on the surface. The light deflection structural plate (3) is placed and fixed to the lamp box (5) so as to close its open surface. The bottom wall (back wall) of the lamp box (5) is formed of a light reflecting plate (7), that is, the inner surface of the bottom wall of the lamp box (5) is a light reflecting surface.

  As shown in FIG. 2, the plurality of point light sources (2) of the surface light source device (1) are arranged on the constituent sides (vertical side 41, horizontal side 42) forming the rectangular shape of the light deflection structural plate (3). Along the vertical and horizontal directions. In the present embodiment, an LED (light emitting diode) is used as the point light source (2).

  As shown in FIG. 3, the light deflection structural plate (3) has one surface (light emitting surface) (3b) having a concavo-convex shape portion (4) formed by projecting a plurality of quadrangular pyramid convex portions (6). It is made of a light transmission plate having a rectangular shape in plan view. The other surface (light incident surface) (3a) of the light deflection structure plate (3) is formed as a flat surface. Although it does not specifically limit as said flat surface, For example, a smooth surface, a satin-like (mat-like) surface, etc. are employ | adopted. The light deflection structure plate (3) has a function of changing the direction of light incident on the light incident surface (3a) and emitting the light from the light emitting surface (3b).

  The light emitting structure plate (3) is arranged so that the light exit surface (3b) on which the concave and convex portion (4) is formed is located on the front side (so as to be on the liquid crystal panel side) (FIG. 1). reference). That is, the surface (light incident surface) (3a) in which the uneven portion (4) is not formed in the light deflection structure plate (3) is arranged on the back side (so as to be on the light source side). (See FIG. 1).

  In the light deflecting structure plate (3), the quadrangular pyramid convex portion (6) is formed so as to project in such a manner that its bottom surface (6d) is connected to a light transmitting plate (a flat surface of the surface) (FIG. 3, 5). That is, the quadrangular pyramid convex portion (6) is formed so as to protrude from the front surface of the light transmission plate in such a manner that the apex (6a) is disposed on the front surface side and the bottom surface (6d) is disposed on the back surface side. (See FIGS. 3 and 5).

  In addition, the bottom surfaces (6d) of the adjacent quadrangular pyramidal protrusions (6) are arranged so as to be in contact with each other at one base (6c) (see FIGS. 3 to 5). That is, the bottom surfaces (6d) of the adjacent quadrangular pyramidal protrusions (6) share one base (6c).

  In addition, the apex angle (θ) of the quadrangular pyramidal projection (6) is set in the range of 45 to 150 degrees (see FIGS. 3, 5 and 6). The term “vertex angle of the quadrangular pyramid convex part” cuts the quadrangular pyramidal convex part (6) by a plane passing through a pair of opposing hypotenuses (6b) among the four hypotenuses (6b) as shown in FIG. This means the apex angle of the triangle of the cut surface (6e) at the time.

  In addition, an angle (acute angle) (α) formed by the bottom side (6c) of the quadrangular pyramid convex portion (6) and the rectangular side edges (41) (42) of the light deflection structure plate (3) is 40 It is set in the range of ˜50 degrees (see FIG. 4).

  In the present embodiment, the quadrangular pyramidal protrusion (6) is protruded from the front surface of the light transmission plate in such a manner that its bottom surface (6d) is parallel to the light incident surface (3a) ( (See FIG. 5).

  Moreover, in this embodiment, the said quadrangular pyramid convex part (6) is protrudingly provided by the front surface of the light transmissive board in the aspect in which each bottom face (6d) mounts on the same plane (refer FIG. 3, 5).

  In the present embodiment, the lengths (E) of the bases (6c) of the plurality of quadrangular pyramidal protrusions (6) are set to be the same (see FIG. 4).

  Moreover, in this embodiment, the cut surface at the time of cut | disconnecting a quadrangular pyramid convex part (6) in the plane which passes along a pair of opposite hypotenuse (6b) among four oblique sides (6b) in the said quadrangular pyramid convex part (6). The triangle shape of (6e) is an isosceles triangle shape (including a regular triangle) (see FIG. 6).

  In the surface light source device (1) according to the above configuration, the light deflection structure plate (3) is a plan view in which a concave and convex portion (4) formed by projecting a plurality of quadrangular pyramid convex portions (6) is provided on one side. The bottom surfaces (6d) of the adjacent quadrangular pyramidal projections (6) are arranged in such a manner that they are in contact with each other at one base (6c), and the apex of the quadrangular pyramidal projections (6). The angle (θ) is 45 to 150 degrees, and the angle (acute angle) (α) formed by the base (6c) of the quadrangular pyramidal protrusion (6) and the sides (41) and (42) of the rectangular shape of the light transmission plate ) Is in the range of 40 to 50 degrees, so that uniform high luminance light with little luminance unevenness is emitted toward the liquid crystal panel (20) not only in the central region but also in the four corners (four corners). be able to.

  That is, since the convex part (6) of the concavo-convex shape part (4) is a quadrangular pyramid shape and the apex angle (θ) of the quadrangular pyramid convex part (6) is 45 to 150 degrees, the point light source (2 ) When the light emitted from the light incident surface (3a) enters the light incident surface (3a), passes through the light deflection structure plate (3), and exits from the light exit surface (3b). Since it divides | segments and radiate | emits (50) (refer FIG. 7), the uniform light by which the brightness nonuniformity was fully suppressed can be radiate | emitted. Further, since the light from the point light source (2) is divided into a plurality of lights (light source images) (50) and emitted, uniform high-luminance light is emitted even if the number of arranged point light sources (2) is reduced. It is possible.

  In addition, since the bottom surfaces (6d) of the adjacent quadrangular pyramidal projections (6) are arranged in contact with each other at their one base (6c), the light from the point light source (2) is divided. Without being lost in the substantially vertical direction (front direction) as it is, and uneven brightness can be sufficiently suppressed.

  Furthermore, the angle (acute angle) (α) formed by the bottom side (6c) of the quadrangular pyramid convex part (6) and the rectangular side edges (41) (42) of the light deflection structural plate (3) is 40 Since it is set in the range of ˜50 degrees, as shown in FIG. 7, the divided four light source images (50) are formed into the rectangular side edges (41) (41) of the light deflection structural plate (3). 42) are aligned in the vertical and horizontal directions, thereby emitting uniform high-luminance light with little luminance unevenness at the four corners (four corners) of the light deflection structural plate (3). Can do.

  Further, since the light diffusion sheet (9) is disposed on the front side of the light deflection structure plate (3), that is, between the light deflection structure plate (3) and the liquid crystal panel (20), 9) is arranged, it is possible to further improve the uniformity of luminance obtained by providing the light deflection structure plate (3) with the above-described configuration.

  For example, in the configuration in which the angle α is 0 degree, as shown in FIG. 10, the divided four light source images (150) are formed on the rectangular configuration side (vertical side / horizontal side) of the light deflection structure plate. Edge) is not aligned in the vertical and horizontal directions, but is aligned in the direction of 45 degrees diagonally, so that the brightness at the four corners (four corners) of the light deflection structure plate As a result, luminance unevenness occurs at the four corners. In FIG. 10, (106a) is the apex of the quadrangular pyramidal projection, (106b) is the hypotenuse, and (106c) is the base.

  In the present invention, the apex angle (θ) of the quadrangular pyramidal protrusion (6) needs to be set in the range of 45 to 150 degrees (see FIG. 6). When the apex angle (θ) is less than 45 degrees, there arises a problem that the light from the point light source (2) is not uniformly divided. On the other hand, when the apex angle (θ) exceeds 150 degrees, there arises a problem that light from the point light source (2) escapes in a substantially vertical direction (front direction) without being divided. Especially, it is preferable that the vertex angle ((theta)) of the said quadrangular pyramid convex part (6) is set to the range of 70-110 degree | times.

  The angle (acute angle) (α) formed by the base (6c) of the quadrangular pyramidal protrusion (6) and the constituent sides (41) (42) constituting the rectangular shape of the light deflection structural plate (3) is , Needs to be set in the range of 40 to 50 degrees (see FIG. 4). When the angle α is less than 40 degrees or more than 50 degrees, the luminance at the four corners (four corners) of the rectangular shape of the light deflection structure plate (3) is lowered from the surroundings, and the luminance unevenness at the four corners. Cannot be sufficiently suppressed. Among these, the angle α is preferably set in a range of 43 to 47 degrees, and a particularly preferable range is 44 to 46 degrees.

  The total light transmittance of the light deflection structural plate (3) is preferably set in the range of 70 to 95%. If the total light transmittance is less than 70%, the light from the point light source (2) is difficult to be divided, which is not preferable. Among them, it is particularly preferable that the total light transmittance of the light deflection structural plate (3) is set in a range of 80 to 90%.

  The pitch interval (P) between adjacent quadrangular pyramidal protrusions (6) is preferably set in the range of 20 to 500 μm (see FIG. 4). When it is 20 μm or more, the effect of preventing brightness unevenness can be sufficiently exhibited, and when it is 500 μm or less, the uneven shape of the uneven portion (4) is not visually observed. Especially, it is more preferable that the pitch interval (P) is set in a range of 30 to 300 μm.

  Moreover, it is preferable that the length (E) of the base (6c) of the quadrangular pyramidal protrusion (6) is set in a range of 20 to 500 μm (see FIGS. 4 and 6). When it is 20 μm or more, the effect of preventing brightness unevenness can be sufficiently exhibited, and when it is 500 μm or less, the uneven shape of the uneven portion (4) is not visually observed.

  Moreover, it is preferable that the height (H) of the said quadrangular pyramid convex part (6) is set to the range of 5-600 micrometers (refer FIG. 5). When it is 5 μm or more, luminance unevenness can be further reduced, and when it is 600 μm or less, the uneven shape of the uneven portion (4) is not visually observed.

  The shape of the bottom face (6d) of the quadrangular pyramidal protrusion (6) is not particularly limited as long as it is a quadrangular shape. For example, it is a square, a rectangle (not including a square), a rhombus, or a parallelogram (not including a rhombus). Etc. Among these, it is preferable that the shape of the bottom surface (6d) is a square. Thus, in the above embodiment, a square is adopted as the shape of the bottom surface (6d) of the quadrangular pyramid convex portion (6).

  In the present invention, the thickness (T) of the light deflection structural plate (3) is not particularly limited, but is preferably set in the range of 0.2 to 10 mm (see FIG. 5). By setting the thickness in such a range, it is possible to further reduce the thickness while sufficiently suppressing the luminance unevenness. Especially, it is more preferable that the thickness (T) of the light deflection structural plate (3) is set to 0.5 to 5.0 mm.

The method for producing the light deflection structural plate (3) is not particularly limited, but for example, an extrusion method, a press method, a cutting method, an injection molding method, a roll transfer molding method, an active energy curable resin composition, The method to use etc. are mentioned. In the case of manufacturing by the extrusion method or the press method, for example, as shown in FIG. 9, a transfer plate (60) engraved with a required square pyramid recess (61) pattern is used on the surface of the light deflection structure plate. The light deflection structural plate (3) can be manufactured by transferring the square pyramid convex portion (6) pattern as shown in FIGS. The transfer rate at that time is preferably 85% or more, and more preferably 90% or more. The transfer rate is a value calculated by the following calculation formula.
Transfer rate (%) = E ÷ F × 100
F: Length of the bottom side of the quadrangular pyramid recess (61) engraved on the plate E: Length of the bottom side (6c) of the quadrangular pyramid projection (6) of the obtained light deflection structure plate.

  In other words, in the light deflection structure plate (3) shown in FIG. 9, the structure in which E ÷ (E + S) × 100 is 85% or more is included in the scope of the claims of the present invention. That is, the phrase “the bottom surfaces of adjacent quadrangular pyramidal protrusions are arranged in contact with each other at their bottoms” is such that E ÷ (E + S) × 100 is 85% or more. Must be interpreted to include

  The light deflection structure plate (3) is not particularly limited as long as it is a plate made of a light-transmitting material, and any plate can be used. For example, a glass plate, an optical glass plate, a translucent resin plate, etc. are mentioned. Examples of the translucent resin plate include acrylic resin plates, polycarbonate plates, polystyrene plates, cyclic polyolefin plates, MS resin plates (methyl methacrylate-styrene copolymer resin plates), ABS resin plates, AS resin plates ( Acrylonitrile-styrene copolymer resin plate), polypropylene plate, styrene-methacrylic acid copolymer plate, styrene-maleic anhydride copolymer plate, and the like. Among them, a light transmission plate having a refractive index of 1.45 to 1.60 is preferably used.

  The light deflection structural plate (3) is provided with a deflection function for changing the direction of light by providing at least one surface with the concavo-convex shape portion (4) having the above characteristics. Light diffusibility may be imparted to the surface. That is, for example, light diffusing particles such as polystyrene particles, resin particles such as silicone particles, inorganic particles such as calcium carbonate particles, barium sulfate particles, titanium oxide particles, and alumina particles are added to translucent resins such as acrylic resins. An optical deflection structure plate formed by molding the contained composition may be used, or an optical deflection structure plate obtained by aligning and containing particles having refractive index anisotropy in an acrylic resin.

  The light diffusing particles (light diffusing agent) are incompatible with the transparent material such as the translucent resin, exhibit a refractive index different from that of the transparent material, and pass through the light deflection structural plate (3). The particles are not particularly limited as long as the particles have a function of diffusing light (including powder), and may be inorganic particles made of an inorganic material or organic particles made of an organic material, for example.

  The inorganic material constituting the inorganic particles is not particularly limited. For example, silica, calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, inorganic glass, mica, talc, white carbon, magnesium oxide, oxidized Zinc etc. are mentioned.

  The organic material constituting the organic particles is not particularly limited, and examples thereof include methacrylic crosslinked resins, methacrylic high molecular weight resins, styrene crosslinked resins, styrene high molecular weight resins, and siloxane polymers. It is done.

  The particle diameter of the inorganic particles and organic particles used as the light diffusion particles is usually 0.1 to 50 μm.

  The amount of the light diffusing particles to be used varies depending on the intended degree of diffusion of transmitted light, but is usually 0.01 to 20 parts by mass, preferably 0.05 to 10 parts per 100 parts by mass of the translucent resin. Parts by mass, more preferably 0.05 to 2 parts by mass, still more preferably 0.07 to 1 part by mass, and particularly preferably 0.1 to 0.5 parts by mass.

  In addition, in the surface light source device (1) of the said embodiment (FIG. 1), the structure provided with the light-diffusion sheet | seat (9) was employ | adopted, but the said light deflection | deviation structure board (3) contains light-diffusion particle | grains, for example. In the case where the light diffusing function is provided by, for example, a structure in which the light diffusing sheet (9) is not provided may be employed. That is, for example, a configuration as shown in FIG. 8 may be adopted.

  In the present invention, the light diffusion sheet (9) is not particularly limited, but for example, an external diffusion light diffusion sheet, an internal diffusion light diffusion sheet, or both external diffusion and internal diffusion And the like. Examples of the external diffusive light diffusing sheet include a light diffusing sheet provided with a light diffusing function by forming the sheet surface on a rough surface such as a mat surface. In this case, it is preferable to arrange the external diffusive light diffusion sheet so that the rough surface is located on the front side. Examples of the internal diffusive light diffusing sheet include a light diffusing sheet provided with a light diffusing function by dispersing and diffusing light diffusing particles (light diffusing agent) in the sheet.

  The number of light diffusion sheets (9) disposed on the front surface side of the light deflection structural plate (3) is not particularly limited, and may be one or may be two or more.

  The light diffusion sheet (9) may be disposed with a gap on the front side of the light deflection structural plate (3), or may be superimposed on the front side of the light deflection structural plate (3). It may be arranged. When two or more light diffusion sheets (9) are disposed, the adjacent light diffusion sheets (9) may be disposed with a gap therebetween or may be disposed in a superimposed manner.

  Although the thickness of the said light-diffusion sheet (9) is not specifically limited, Usually, it is the range of 0.05-5 mm.

  Although it does not specifically limit as said point light source (2), For example, LED (light emitting diode), an incandescent lamp, etc. are mentioned.

  In the above-described embodiment, a plurality of quadrangular pyramid convex portions (6) having the same shape and the same size having the above-described features are formed to project (see FIGS. 3 to 5). For example, if it is a quadrangular pyramid convex portion having the above characteristics (if it is a quadrangular pyramid convex portion satisfying the specific condition), a plurality of types of quadrangular pyramid convex portions having different shapes are projected. Alternatively, a plurality of square pyramid convex portions (6) having the same shape but different sizes (that is, similar shapes) may be provided.

  In this invention, it is preferable that the distance (L1, L2) between the centers of the adjacent point light sources (2) is set to 5 mm or more (see FIG. 2). The distance (d) between the light incident surface (3a) of the light deflection structure plate (3) and the light reflection plate (7) is preferably set to 50 mm or less from the viewpoint of thinning.

  The size (area) of the light deflection structural plate (3) is not particularly limited, and is appropriately set according to the size of the target surface light source device (1) and liquid crystal display device (30), for example. However, it is usually designed in a size of 20 cm × 30 cm to 150 cm × 200 cm.

  The light deflecting structure plate (3), the surface light source device (1), and the liquid crystal display device (30) according to the present invention are not particularly limited to those of the above-described embodiment. Any design changes are permitted as long as they do not depart from the spirit.

  Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples.

<Example 1>
When the surface light source device (1) shown in FIG. 1 is configured using the light deflection structure plate (3) having the structure shown in FIGS. 3 to 5, the average luminance and the luminance uniformity of the surface light source device are simulated by the Monte Carlo method. Calculated by

  As said light deflection | deviation structure board (3), 0.35 mass part of polymethyl methacrylate light-diffusion particle | grains (refractive index 1.49) with a volume average particle diameter of 2 micrometers in 100 mass parts of polystyrene resins (refractive index 1.59). Assuming a configuration composed of a resin composition dispersed and contained, the total light transmittance (Tt) is set to 85%, the apex angle (θ) of the quadrangular pyramid convex portion (6) is 90 degrees, and the quadrangular pyramid convex The length (E) of each base (6c) of the part (6) is set to 100 μm, the pitch interval (P) between the adjacent quadrangular pyramidal protrusions (6) is set to 100 μm, and the base of the quadrangular pyramid convex part (6) The angle (acute angle) (α) formed between (6c) and the rectangular-shaped constituent sides (41) (42) of the light deflection structural plate (3) is set to 45 degrees, and the thickness of the light deflection structural plate (3) is set. (T) is set to 2 mm, and the distance (L1) between the centers of adjacent LED point light sources (2) in the horizontal direction is set to 35. .2 mm, the center-to-center distance (L2) in the vertical direction is 35.2 mm, the distance (d) between the light incident surface (3a) of the light deflection structure plate and the light reflection plate (7) is 20 mm, and the surface light source device (1) The horizontal length (M) was set to 140.8 mm, and the vertical length (N) was set to 105.6 mm. The bottom surface (6d) of the quadrangular pyramid convex part (6) is a square (see FIG. 4), and the cut surface (6e) of the quadrangular pyramidal convex part (6) is isosceles with the same length of the hypotenuse (6b). The simulation was performed assuming that it was a triangle (see FIG. 6). In addition, a simulation was performed on the assumption that a diffusion film “BS912” manufactured by Eiwa Co., Ltd. was used as the light diffusion sheet (9).

  The Monte Carlo simulation is a simulation method for obtaining an approximate solution by performing a simulation using random numbers many times.

<Comparative Example 1>
The average luminance and luminance uniformity of the surface light source device are set to Monte Carlo in the same manner as in Example 1 except that the configuration in which the quadrangular pyramidal protrusions are not formed on the surface of the light deflection structure plate (the light emission surface is a smooth surface). Calculated by method simulation.

<Comparative example 2>
The surface light source device of the surface light source device was the same as in Example 1 except that the angle (α) formed by the bottom side of the quadrangular pyramid convex portion and the side constituting the rectangular shape of the light deflection structure plate was set to 0 degree or 90 degrees. Average brightness and brightness uniformity were calculated by Monte Carlo simulation.

<Comparative Example 3>
As shown in FIG. 11, the average luminance of the surface light source device was the same as in Example 1 except that the pitch interval (P) of the adjacent quadrangular pyramidal protrusions (106) in the light deflection structural plate (103) was set to 200 μm. And the brightness uniformity was calculated by Monte Carlo method simulation (the length E of the base of the quadrangular pyramidal projection was set to the same 100 μm as in Example 1). That is, the above-described design is E ÷ (E + S) × 100 = 50%.

<Comparative example 4>
The average luminance and luminance uniformity of the surface light source device are the same as in Example 1, except that the apex angle (θ) of the quadrangular pyramid protrusion is set to 40 degrees and the length (E) of each base is set to 100 μm. Was calculated by Monte Carlo simulation.

<Comparative Example 5>
The average luminance and the luminance uniformity of the surface light source device are the same as in Example 1 except that the apex angle (θ) of the quadrangular pyramid convex portion is set to 160 degrees and the length (E) of each base is set to 100 μm. Was calculated by Monte Carlo simulation.

  In addition, the evaluation method of the average brightness | luminance and brightness | luminance uniformity at the time of applying the said Monte Carlo method simulation is as follows.

<Average luminance measurement method and luminance uniformity evaluation method (evaluation on the entire light exit surface)>
The average value of the entire luminance of the front surface (light emitting surface) of the surface light source device is defined as average luminance (Nit), while the minimum luminance value in the entire front surface (light emitting surface) is defined as “b”. When the maximum luminance values on both sides of “a” and “c” are respectively (see FIG. 12),
Brightness uniformity (%) = b ÷ {(a + c) ÷ 2} × 100
The value obtained from the above formula was defined as the luminance uniformity.

<Evaluation method of brightness uniformity at four corners>
The average value of each brightness | luminance in four corner (corner part) area | regions (70) (refer FIG. 13) in the front surface (light-emitting surface) of a surface light source device is set to "Y", and the front surface (light-emitting surface) of a surface light source device ) When the average value of the overall brightness is "Z"
Brightness uniformity at the four corners (%) = Y ÷ Z × 100
The value obtained by the above calculation formula was defined as “luminance uniformity at the four corners”.

  As shown in FIG. 13, each corner region (70) is horizontally long when the horizontal length of the light exit surface of the light deflection structure plate (3) is “V” and the vertical length is “W”. The corner region has a size of 0.1 V and a vertical length of 0.1 W.

  As is apparent from Table 1, the surface light source device of Example 1 configured using the light deflection structural plate of the present invention has luminance uniformity with little luminance unevenness in the entire region including the corner region (four corners). It is possible to emit light with excellent brightness.

  On the other hand, in the surface light source devices of Comparative Examples 1, 3, and 5 configured using the light deflection structure plate that departs from the scope of the present invention, noticeable luminance unevenness is recognized in the central region, and the luminance is in the four corners. Unevenness occurs (the four corners are darker than other areas). Further, in the surface light source device of Comparative Example 2, although the luminance unevenness is relatively small in the central region, the luminance unevenness occurs in the four corners (the four corners are darker than the other regions). Further, although the surface light source device of Comparative Example 4 can emit uniform light with little unevenness in luminance, the overall average luminance is remarkably insufficient.

  The light deflecting structure plate of the present invention is suitably used as an optical member for a surface light source device (for example, a light deflecting structure plate, a light diffusing plate, etc.), but is not particularly limited to such use. The surface light source device of the present invention is preferably used as a backlight for a liquid crystal display device, but is not particularly limited to such applications.

DESCRIPTION OF SYMBOLS 1 ... Surface light source device 2 ... Point light source 3 ... Light deflection | deviation structure board 3a ... Back surface 3b ... Front surface (surface in which the uneven | corrugated shaped part was formed)
4 ... Uneven shape part 5 ... Lamp box 6 ... Quadrangular pyramid convex part 6c ... Base 7 ... Light reflector 9 ... Light diffusion sheet 20 ... Liquid crystal panel 30 ... Liquid crystal display device 41, 42 ... Rectangle configuration of light deflection structure plate Side θ: Vertex angle P of the quadrangular pyramidal protrusions P: Pitch interval α between adjacent quadrangular pyramidal protrusions: Angle formed by the base of the quadrangular pyramidal protrusions and the rectangular component side of the light deflection structural plate (acute angle)

Claims (7)

A concave-convex shape portion formed by projecting a plurality of quadrangular pyramid convex portions is a light transmission plate having a rectangular shape in plan view provided on one side,
The bottom surfaces of the adjacent quadrangular pyramidal protrusions are arranged in a manner in which they touch each other at their respective bottom sides,
The apex angle of the quadrangular pyramidal protrusion is 45 to 150 degrees,
An angle (acute angle) formed by a base of the quadrangular pyramidal protrusion and a rectangular component side of the light transmission plate is in a range of 40 to 50 degrees.   The light deflection structure plate according to claim 1, wherein a pitch interval between adjacent quadrangular pyramidal protrusions is 20 to 500 µm.   3. The light deflection structure plate according to claim 1, wherein the total light transmittance is 70 to 95%.   The light deflection | deviation structure board of any one of Claims 1-3, the some point light source arrange | positioned at the back side of this light deflection | deviation structure board, and the light reflection arrange | positioned at the back side of this some light source A surface light source device, wherein the surface on which the concave and convex portion is formed is disposed on the front side of the light deflection structure plate.   The light deflection | deviation structure board of any one of Claims 1-3, the some point light source arrange | positioned at the back side of this light deflection | deviation structure board, and the light reflection arrange | positioned at the back side of this some light source A light diffusion sheet disposed on the front surface side of the light deflection structure plate, and the light deflection structure plate is disposed such that the surface on which the uneven portion is formed is on the front surface side. A characteristic surface light source device.   The light deflection | deviation structure board of any one of Claims 1-3, the some point light source arrange | positioned at the back side of this light deflection | deviation structure board, and the light reflection arrange | positioned at the back side of this some light source And a liquid crystal panel disposed on the front surface side of the light deflection structure plate, wherein the surface on which the concavo-convex shape portion is formed on the light deflection structure plate is disposed on the front surface side. A liquid crystal display device.   The light deflection | deviation structure board of any one of Claims 1-3, the some point light source arrange | positioned at the back side of this light deflection | deviation structure board, and the light reflection arrange | positioned at the back side of this some light source A plate, a liquid crystal panel disposed on the front side of the light deflection structure plate, and a light diffusing sheet disposed between the liquid crystal panel and the light deflection structure plate, wherein the uneven shape portion is provided on the light deflection structure plate. A liquid crystal display device, wherein the formed surface is disposed on the front side.

Images