JP2010044378A - Light beam deflecting 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 a 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 recesses 6 and is such that bases 6d of adjoining quadrangular pyramid recesses 6 are arranged, in such a form as the bases touch each other on the respective base sides 6c; the vertical angle θ of the quadrangular pyramid recess 6 is 45 to 150 degrees; and an angle (acute angle), formed by the base side 6c of the quadrangular pyramid recess 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 recess” means the virtual cut surface when the quadrangular pyramid recess is cut by a plane passing through a pair of opposing hypotenuses among the four hypotenuses. It means the apex angle of a 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, in the case where 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 recesses on the light exit surface of the light diffusion plate disposed on the front side of the light source (see Patent Document 1). ). 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 concave and convex portion formed by a plurality of quadrangular pyramid recesses is provided on one side,
The bottom surfaces of the adjacent quadrangular pyramid recesses are arranged in such a manner that they touch each other on the one bottom side,
The apex angle of the quadrangular pyramid recess is 45 to 150 degrees,
An optical deflection structure plate, wherein an angle (acute angle) formed by a bottom side of the quadrangular pyramid recess and a rectangular component side of the light transmission plate is in a range of 40 to 50 degrees.

  [2] The optical deflection structure plate according to item 1 above, wherein the pitch interval between adjacent quadrangular pyramid recesses 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 including a plurality of quadrangular pyramid recesses is formed of a light transmission plate having a rectangular shape in plan view provided on one side, and the bottom surfaces of the adjacent quadrangular pyramid recesses are mutually connected. It arrange | positions in the aspect contact | connected in one base, the apex angle of a quadrangular pyramid recessed part is 45-150 degree | times, and the angle (acute angle) which the bottom side of a quadrangular pyramid recessed part and the rectangular-shaped component side of a light-transmitting plate make is 40- Since it is in the range of 50 degrees, uniform light with little luminance unevenness can be emitted 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 pyramid recesses is 20 to 500 μm, the uneven shape of the uneven portion can be sufficiently prevented from being visually observed, and the corner portion region is also included. Luminance unevenness can be further reduced in the entire region.

  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 recessed 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 of the light source image by the quadrangular pyramid recessed 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 recessed 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 structure plate (3) has a concave-convex shape portion (4) in which a plurality of quadrangular pyramid recesses (6) are provided on one surface (light emitting surface) (3b). It consists 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 deflection structural plate (3), the quadrangular pyramid recess (6) has an apex (6a) disposed on the back side and a bottom surface (virtual bottom surface) (6d) disposed on the front side. It is formed on the front side of the light transmission plate (see FIGS. 3 and 5).

  Moreover, the bottom surfaces (6d) of the adjacent quadrangular pyramid recesses (6) are arranged in such a manner that they contact each other at one bottom side (6c) (see FIGS. 3 to 5). That is, the bottom surfaces (6d) of the adjacent quadrangular pyramid recesses (6) share one base (6c).

  Moreover, the apex angle ((theta)) of the said quadrangular pyramid recessed part (6) is set to the range of 45-150 degree | times (refer FIG.3,5,6). The term “vertical angle of the quadrangular pyramid recess” means that when the quadrangular pyramid recess (6) is cut by a plane passing through a pair of opposing hypotenuses (6b) among the four hypotenuses (6b) as shown in FIG. Means the apex angle of the triangle of the virtual cutting plane (6e).

  The angle (acute angle) (α) formed by the bottom side (6c) of the quadrangular pyramid recess (6) and the rectangular component sides (41) (42) of the light deflection structural plate (3) is 40 to 40. The range is set to 50 degrees (see FIG. 4).

  In the present embodiment, the quadrangular pyramid recess (6) is formed on the front side 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 recessed part (6) is formed in the front surface of a 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 length (E) of the base (6c) of the plurality of quadrangular pyramid recesses (6) is set to be the same (see FIG. 4).

  Moreover, in this embodiment, the virtual cut surface (when a quadrangular pyramid recessed part (6) is cut | disconnected by the plane which passes along a pair of hypotenuse (6b) which opposes among the four oblique sides (6b) in the said quadrangular pyramid recessed part (6) ( The triangle shape of 6e) is an isosceles triangle shape (including an equilateral triangle) (see FIG. 6).

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

  That is, since the concave portion (6) of the concave-convex shape portion (4) has a quadrangular pyramid shape and the apex angle (θ) of the quadrangular pyramid concave portion (6) is 45 to 150 degrees, the point light source (2) When the emitted light is incident on the light incident surface (3a), passes through the light deflecting structure plate (3) and is emitted from the light emitting surface (3b), a plurality of light (light source images) (50 of the same intensity) (50 ) (See FIG. 7), it is possible to emit uniform light in which luminance unevenness is sufficiently suppressed. 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.

  Further, since the bottom surfaces (6d) of the adjacent quadrangular pyramid recesses (6) are arranged in contact with each other at one base (6c), the light from the point light source (2) is not divided. It is possible to prevent the lens from slipping out in the substantially vertical direction (front surface direction) as it is, and thereby it is possible to sufficiently suppress luminance unevenness.

  Furthermore, the angle (acute angle) (α) formed by the bottom side (6c) of the quadrangular pyramid recess (6) and the rectangular-shaped constituent sides (41) (42) of the light deflection structure 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 the rectangular side edges (41) (42) of the light deflection structural plate (3). ) Along the vertical and horizontal directions so that uniform high-luminance light with little luminance unevenness can be emitted even at the four corners (four corners) of the light deflection structural plate (3). it can.

  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 pyramid recess, (106b) is the hypotenuse, and (106c) is the base.

  In the present invention, the apex angle (θ) of the quadrangular pyramid recess (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 recessed 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 pyramid recess (6) and the constituent sides (41) (42) constituting the rectangular shape of the light deflection structural plate (3) is: It 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 pyramid recesses (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.

  The length (E) of the base (6c) of the quadrangular pyramid recess (6) is preferably set in the 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.

  The depth (H) of the quadrangular pyramid recess (6) is preferably set in the range of 5 to 600 μm (see 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 surface (virtual bottom surface) (6d) of the quadrangular pyramid recess (6) is not particularly limited as long as it is a square shape. For example, a square, a rectangle (not including a square), a rhombus, a parallelogram (a rhombus) Not included). Among these, the shape of the bottom surface (virtual bottom surface) (6d) is preferably square. Thus, in the above embodiment, a square is employed as the shape of the bottom surface (6d) of the quadrangular pyramid recess (6) (see FIGS. 3 and 4).

  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, the surface of the light deflection structure plate is formed using a transfer plate (60) engraved with a required square pyramidal convex portion (61) pattern. A light deflecting structural plate (3) can be manufactured by transferring a quadrangular pyramid recess (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 pyramidal protrusion (61) engraved on the plate E: Length of the bottom side (6c) of the quadrangular pyramid concave portion (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. In other words, the phrase “the bottom surfaces of the adjacent quadrangular pyramid recesses are arranged in such a manner that they are in contact with each other at their respective bottoms” is such that E ÷ (E + S) × 100 is 85% or more. It must be interpreted in the meaning of inclusion.

  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 embodiment, a plurality of quadrangular pyramid recesses (6) having the same shape and the same size as described above are formed (see FIGS. 3 to 5). However, the present invention is particularly limited to such a configuration. For example, as long as it is a quadrangular pyramid recess having the above characteristics (if it is a quadrangular pyramid recess satisfying the specific condition), a configuration in which a plurality of types of quadrangular pyramid recesses having different shapes may be provided. Alternatively, a configuration may be employed in which a plurality of quadrangular pyramid recesses (6) having the same shape and different sizes (that is, similar shapes) are 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 comprising a resin composition dispersed and contained, the total light transmittance (Tt) is set to 85%, the apex angle (θ) of the quadrangular pyramid recess (6) is 90 degrees, and the quadrangular pyramid recess ( 6) The length (E) of each base (6c) is set to 100 μm, the pitch interval (P) between adjacent quadrangular pyramid recesses (6) is set to 100 μm, and the base (6c) of the quadrangular pyramid recess (6) is set to The angle (acute angle) (α) formed by the rectangular component sides (41) (42) of the light deflection structural plate (3) is set to 45 degrees, and the thickness (T) of the light deflection structural plate (3) is set. 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 recess (6) is a square (see FIG. 4), and the virtual cut surface (6e) of the quadrangular pyramid recess (6) is an isosceles triangle having the same length of the hypotenuse (6b). (See FIG. 6), a simulation was performed. 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 the luminance uniformity of the surface light source device are determined by the Monte Carlo method in the same manner as in Example 1 except that the surface of the light deflection structural plate is not formed with a quadrangular pyramid recess (the light emission surface is a smooth surface). Calculated by simulation.

<Comparative example 2>
The average of the surface light source device is the same as that of Example 1, except that the angle (α) formed by the bottom side of the quadrangular pyramid recess and the side constituting the rectangular shape of the light deflection structural plate is set to 0 degree or 90 degrees. Luminance and luminance uniformity were calculated by Monte Carlo simulation.

<Comparative Example 3>
As shown in FIG. 11, the average luminance of the surface light source device and the average luminance of the surface light source device are the same as in Example 1 except that the pitch interval (P) between the adjacent quadrangular pyramid recesses (106) in the light deflection structural plate (103) is set to 200 μm. The luminance uniformity was calculated by Monte Carlo simulation (calculated by setting the length E of the bottom side of the quadrangular pyramid recess 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 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 recess is set to 40 degrees and the length (E) of each base is set to 100 μm. It was calculated by Monte Carlo simulation.

<Comparative Example 5>
The average luminance and luminance uniformity of the surface light source device were set in the same manner as in Example 1 except that the apex angle (θ) of the quadrangular pyramid recess was set to 160 degrees and the length (E) of each base was set to 100 μm. It 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, in the surface light source device of Comparative Example 4, the overall average luminance is remarkably insufficient, and luminance unevenness occurs at the four corners (the four corners are darker than other regions).

  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 portion 5 ... Lamp box 6 ... Quadrangular pyramid recess 6c ... Base 7 ... Light reflecting plate 9 ... Light diffusion sheet 20 ... Liquid crystal panel 30 ... Liquid crystal display device 41, 42 ... Rectangle-shaped side of the light deflection structure plate θ: apex angle of quadrangular pyramid recess P: pitch interval between adjacent quadrangular pyramid recesses α: angle formed by the base of the quadrangular pyramid recess and the rectangular component side of the light deflection structural plate (acute angle)

Claims (7)

The concave-convex shape portion formed by providing a plurality of quadrangular pyramid recesses is a light transmission plate having a rectangular shape in plan view provided on one side,
The bottom surfaces of the adjacent quadrangular pyramid recesses are arranged in such a manner that they touch each other on the one bottom side,
The apex angle of the quadrangular pyramid recess is 45 to 150 degrees,
An optical deflection structure plate, wherein an angle (acute angle) formed by a bottom side of the quadrangular pyramid recess 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 pyramid recesses 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.

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