JP2012108498A - Light-diffusing plate and method for manufacturing light-diffusing plate - Google Patents

Abstract

A light diffusing plate, a method of manufacturing the light diffusing plate, a surface light source device including the light diffusing plate, and a liquid crystal display device including the light diffusing plate are provided.
A light diffusing plate is a light diffusing plate disposed on the back surface of a liquid crystal panel of a liquid crystal display device, and an optical element portion 53 extending in a plurality of first directions on a surface 50b on the liquid crystal panel side. There are arranged in parallel at a pitch P _l in a second direction perpendicular to the first direction, the pitch in the second direction of the pixel 11 of the liquid crystal panel and P _p, the second direction of the optical element portion and a pixel The pitch of the moire based on the periodic structure at Pm is P _m 1 and P _m 2, and P _m 1 and P _m 2 are P _m 1 = P _p · P _l / | P _p −P _l | and P _m 2 = 0. When expressed by 5P _p · P _l /|0.5 P _p −P _l |, P _l is a value in which both P _m 1 and P _m 2 satisfy less than 1500 μm.

Description

  The present invention relates to a light diffusing plate and a method for manufacturing the light diffusing plate.

  A backlight unit of a transmissive display (transmissive image display device) such as a liquid crystal display uses a linear light source such as a CCFL and a point light source such as an LED, and has a planar shape by diffusing light with a light diffusion plate. It has been converted to light. In the past, light diffusing plates using light scattering of diffusing agent particles have been used, but in recent years, in order to meet the demands for cost reduction, low power consumption and thinning by reducing the number of lamps, lenses, prisms, etc. A light diffusing plate having a surface shaped optical element portion has been used. Such a shaped diffusion plate has a periodic structure because a plurality of optical element portions are juxtaposed substantially parallel to each other. On the other hand, the liquid crystal panel also has a periodic structure because a plurality of pixels are arranged at regular intervals. When a shaped diffusion plate having a periodic structure is used in combination with a liquid crystal panel having a periodic structure, moire may occur due to the relationship between the widths (pitch) of the two. When moire with a period of several millimeters is generated, it is easily recognized by human eyes, and there is a problem that the display quality of the display is remarkably lowered.

  As a technique for preventing such moire, for example, a technique described in Patent Document 1 is known. In the technique described in Patent Document 1, a diffusion film is used in combination with a light diffusing plate, and the pitch of the optical element portion (convex portion) formed on the light diffusing plate is set to the pixel pitch, the haze of the diffusing film, and the total light transmission. By optimizing based on the rate, the occurrence of moire is suppressed.

JP 2007-11292 A

  However, for example, in the technique described in Patent Literature 1, moire may occur without following the formula formulated in Patent Literature 1.

  Accordingly, an object of the present invention is to provide a light diffusing plate, a method of manufacturing the light diffusing plate, a surface light source device including the light diffusing plate, and a liquid crystal display device including the light diffusing plate that can more reliably suppress moire. To do.

The light diffusion plate according to the present invention is a light diffusion plate provided on the incident surface side of the liquid crystal panel, and is formed on at least one of the first surface on the liquid crystal panel side and the second surface facing the first surface. A plurality of optical element portions. Each optical element portion extends in the first direction, and the plurality of optical element portions are arranged in parallel in a second direction substantially orthogonal to the first direction. The pitch of the plurality of optical element portions in the second direction is P _l [μm], and the pixel pitch of the plurality of pixels included in the liquid crystal panel is P _p [μm] (where P _p ≠ P _l and 0.5P _p ≠ P _l ), and the moire pitch of the moire based on the periodic structure in the second direction of the plurality of optical element portions and the plurality of pixels is P _m 1 [μm] and P _m 2 [μm]. , P _m 1 and P _m 2 are represented by formula (1) and formula (2), respectively, the above P _l is such that P _m 1 satisfies P _m 1 <1500 μm and P _m 2 is P _m 2. <Value satisfying 1500 μm.

When the light diffusing plate is used for a liquid crystal panel including pixels arranged with a pitch of P _p in the second direction, the P _m 1 is less than 1500 μm. For this reason, it is difficult to visually recognize moire generated by the periodic structure having the pitch P _{p and} the periodic structure having the pitch P _l . In addition to the moire caused by the periodic structure having the pitch P _p of the pixels of the liquid crystal panel as a period and the periodic structure having the pitch P _l of the optical element portion as a period, the present inventors have set ₁ of the pixel pitch P _p . It has been found that moire with a period of / 2 may occur. The pitch of the moire is expressed by equation (2). Then, in the light diffuser plate according to the present invention, _{P l} is, since _{P m} 2 is a value to be less than 1500 .mu.m, moire hardly visible to half the period of the pitch _{P p.} Therefore, the use of the light diffusing plate makes it more difficult to see moire more reliably.

The light diffuser plate according to the present invention, the _{P l} is, _{P m} 1 satisfies _{P m} 1 ≦ 1000 .mu.m, and can _{be P m} 2 is a value satisfying _{P m} 2 ≦ 1000 .mu.m, to. In this case, the moire becomes even less visible.

In the light diffusing plate according to the present invention, the P _p may be 440 μm or more and 535 μm or less, and the P ₁ may be 325 μm or more and 335 μm or less. In this case, when _{the P l} is a single light diffusion plate in which the optical element unit is formed by _{P l} of one of the following values 335μm above 325Myuemu, combined to the liquid crystal panel _{P p} is equal to or less than 535μm or 440 .mu.m, The combination with any liquid crystal panel can reduce the visibility of moire.

In the light diffusing plate according to the present invention, when the width of the liquid crystal panel in the second direction is L [μm] and the number of pixels in the second direction is N (N is an integer of 1 or more), P _p May be represented by L / N. An example of the optical element part in the light diffusion plate according to the present invention is a convex part.

  A surface light source device according to the present invention is a surface light source device that supplies light to a liquid crystal panel, and includes a light source unit that outputs illumination light to the liquid crystal panel, and the present invention provided between the light source unit and the liquid crystal panel. And a light diffusing plate.

  In this surface light source device, the light output from the light source unit passes through the light diffusion plate and is output to the liquid crystal panel side. Since a plurality of optical element portions are formed on the surface of the light diffusing plate on the liquid crystal panel side, the light diffusing plate is likely to be emitted in various directions when emitted from the light diffusing plate. Thereby, the light from the light source unit is irradiated onto the liquid crystal panel as planar light. Moreover, since the light diffusing plate which a surface light source device has is the light diffusing plate which concerns on this invention mentioned above, when it combines with the said liquid crystal panel, it becomes difficult to see a moire more reliably.

  The liquid crystal display device according to the present invention includes a liquid crystal panel, a light source unit that outputs illumination light to the liquid crystal panel, and a light diffusion plate according to the present invention provided between the light source unit and the liquid crystal panel.

  In this liquid crystal display device, the light output from the light source unit passes through the light diffusion plate and is output to the liquid crystal panel side. Since a plurality of optical element portions are formed on the surface of the light diffusing plate on the liquid crystal panel side, the light diffusing plate is likely to be emitted in various directions when emitted from the light diffusing plate. Thereby, the light from the light source unit is irradiated onto the liquid crystal panel as planar light. Moreover, since the light diffusing plate which a liquid crystal display device has is the light diffusing plate which concerns on this invention mentioned above, it becomes difficult to see a moire more reliably.

  The liquid crystal display device according to the present invention may further include an optical film portion including at least one optical film between the liquid crystal panel and the light diffusion plate. The haze value H (%) of the optical film portion satisfies 95 ≦ H ≦ 99.9.

  In this case, since the optical film whose haze value H satisfies the above conditions is provided between the liquid crystal panel and the light diffusing plate, the moire becomes even less visible.

The light diffusing plate manufacturing method according to the present invention is a light diffusing plate provided on the incident surface side of the liquid crystal panel, and a plurality of optical element portions extending in the first direction are perpendicular to the first direction. A method of manufacturing a light diffusing plate having surfaces arranged in parallel in a direction, a design process for designing a pitch P _l [μm] with respect to a second direction of a plurality of optical element portions, and a design based on the design process on the basis of the above P _l, and a manufacturing process a plurality of the optical element portion, which is formed on one surface of the light has a transparent diffuser plate and comprising a plate-like member to manufacture an optical diffusing plate. In the above design process, when the light diffusion plate is arranged with respect to the liquid crystal panel in the liquid crystal display device, the pixel pitch in the second direction of the plurality of pixels included in the liquid crystal panel is set to P _p [μm] (where P P _p ≠ P _l and 0.5P _p ≠ P _l ), and the moire pitch of the moire based on the periodic structure in the second direction of the plurality of optical element portions and the plurality of pixels is set to P _m 1 [μm] and P _m 2 [μm]. and then, when representing a _{P m} 1 and _{P m} 2, respectively formula (3) and (4), the _{P l, P m} 1 satisfies _P m 1 <1500 .mu.m, and, _{P m} 2 is _{P m} It is determined as a value satisfying 2 <1500 μm.

In the manufacturing method described above, the pitch P _l is designed using the equations (3) and (4) with respect to the pixel pitch P _p of the liquid crystal panel to be used. And a light diffusing plate is manufactured based on the design value. Therefore, when the manufactured light diffusing plate is used for a liquid crystal panel including pixels arranged with the pitch in the second direction being P _p , the P _m 1 is less than 1500 μm. Therefore, it is difficult to visually recognize the moire generated by the pitch P _p and the periodic structure of the pitch P _l . Moreover, in the light diffusing plate manufactured by the above-described manufacturing method, since P ₁ is a value in which P _m 2 is also less than 1500 μm, it is difficult to visually recognize moire having a period of 1/2 of the pitch P _p . Therefore, according to the above method, it is possible to manufacture a light diffusing plate that is more difficult to see moire even when combined with a liquid crystal panel.

In the manufacturing method of the light diffusion plate according to the present invention, in the design process, the _{P l,} satisfies the _{P m} 1 is _{P m} 1 ≦ 1000 .mu.m, and, _{P m} 2 is determined as a value satisfying _{P m} 2 ≦ _1000μm , And can be. In this case, when the manufactured light diffusing plate is combined with a liquid crystal panel, moire becomes even less visible.

In the method for manufacturing a light diffusing plate according to the present invention, the P _p is 440 μm or more and 535 μm or less, and the P ₁ is 325 μm or more and 335 μm or less. In this case, when _{the P l} is a single light diffusion plate in which the optical element unit is formed by _{P l} of one of the following values 335μm above 325Myuemu, combined to the liquid crystal panel _{P p} is equal to or less than 535μm or 440 .mu.m, The combination with any liquid crystal panel can reduce the visibility of moire. As a result, it is possible to reduce the production cost of, for example, a liquid crystal display device including the manufactured light diffusion plate.

In the light diffusing plate manufacturing method according to the present invention, when the width of the liquid crystal panel in the second direction is L [μm] and the number of pixels in the second direction is N (N is an integer of 1 or more). , P _p may be represented by L / N.

The manufacturing process of the light diffusion plate manufacturing method according to the present invention includes a sheet manufacturing process for manufacturing a resin sheet as the plate-like body by extrusion molding, and a pitch P designed in the design process on one surface of the resin sheet. a transfer step of transferring a transfer mold onto one surface by pressing a roll having a mold opposite to the plurality of optical element portions arranged at _l , and forming the plurality of optical element portions on one surface. A light diffusion forming step of cutting out a predetermined region of the resin sheet made into a light diffusion plate;
Can have.

  In this method, after forming the resin sheet, a roll having a transfer mold corresponding to the plurality of optical element portions arranged at the designed pitch P1 is pressed against one surface of the resin sheet, so that a plurality of Forming an optical element portion. And a light diffusing plate is obtained by cutting out the predetermined area | region of the resin sheet as a plate-shaped object in which the some optical element part was formed.

  According to the present invention, a light diffusing plate in which a plurality of optical elements extending in a predetermined direction are formed in parallel to each other and capable of more reliably suppressing moire, a method of manufacturing a light diffusing plate, light A surface light source device including a diffusion plate and a liquid crystal display device including a light diffusion plate can be provided.

1 is a perspective view schematically showing a configuration of an embodiment of a liquid crystal display device according to the present invention. It is a schematic diagram of the cross-sectional structure in the II-II line | wire of the liquid crystal display device shown in FIG. It is a perspective view which shows typically the structure of one Embodiment of the light diffusing plate which concerns on this invention. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. (A) is a schematic diagram of the liquid crystal display device shown in FIG. (B) is a schematic diagram of the periodic structure of the moire produced by the periodic structure of a light diffusing plate and a liquid crystal panel. (C) is a schematic diagram of the transmittance profile of the liquid crystal panel. (D) is a schematic diagram of the transmittance profile of the light diffusing plate. 4 is a diagram illustrating an example of a pixel image when a 32-inch FHD liquid crystal panel is driven in a VA mode. (A) is a diagram showing a periodic structure having a period of pitch P _l, moire occurring when a combination of a liquid crystal panel 32-inch FHD the relationship between the pitch and the pitch P _l. (B) is a diagram showing the relationship between the periodic structure having a period of pitch P _l, the pitch and the pitch P _l moire occurring when a combination of a liquid crystal panel 40-inch FHD. It is a schematic diagram of the cross-sectional structure of the liquid crystal display device in case an optical film part is included. It is a flowchart which shows one Embodiment of the manufacturing method of the light diffusing plate which concerns on this invention. (A) is a schematic diagram of an example of the manufacturing apparatus of a light diffusing plate. (B) is a partially enlarged view of region α in (a). It is a graph which shows the implementation conditions and evaluation result in Examples 1-14 and Comparative Examples 1-5. 10 is a chart showing implementation conditions and evaluation results in Examples 11, 13, 15, 16 and Comparative Examples 6 and 7.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same reference numerals are given to the same elements, and duplicate descriptions are omitted. Further, the dimensional ratios in the drawings do not necessarily match those described.

  FIG. 1 is a perspective view schematically showing a configuration of an embodiment of a liquid crystal display device according to the present invention. FIG. 2 is a schematic diagram of a cross-sectional configuration taken along line II-II of the liquid crystal display device shown in FIG.

  The liquid crystal display device 1 is a so-called direct liquid crystal display. The liquid crystal display device 1 includes a liquid crystal panel 10 and a backlight system (surface light source device) 20 that supplies illumination light to the liquid crystal panel 10. In the following description, in the liquid crystal display device 1, the liquid crystal panel 10 side is also referred to as a front side, and the backlight system 20 side is also referred to as a rear side or a back side. For convenience of explanation, the direction from the backlight system 20 toward the liquid crystal panel 10 (the thickness direction of the liquid crystal panel 10) is referred to as the z direction, and the direction orthogonal to the z direction is the x direction as shown in FIG. And the y direction.

  The liquid crystal panel 10 includes a liquid crystal cell 12 including a plurality of pixels 11 (see FIG. 2), and a pair of polarizing plates 13 and 14 that sandwich the liquid crystal cell 12 from both sides in the thickness direction of the liquid crystal cell 12. As the liquid crystal cell 12, for example, a known liquid crystal cell such as a TFT liquid crystal cell driven by active matrix driving can be used. As a driving method of the liquid crystal panel 10, a known method such as a VA method, an IPS method, and a TN method can be used. In the configuration shown in FIGS. 1 and 2, the polarizing plate 13 is located on the backlight system 20 side, and thus the surface 13 a of the polarizing plate 13 becomes an incident surface of illumination light to the liquid crystal panel 10.

  The backlight system 20 includes a resin-made lamp box 30 whose front side is open, a plurality of light sources 40 as light source units provided in the lamp box 30, and a lamp box 30 provided on the lamp box 30. And a light diffusing plate 50 that closes the opening. Here, the plurality of light sources 40 have been described as the light source unit, but the lamp box 30 may be a part of the light source unit.

  The lamp box 30 is configured such that a square frame-shaped side wall 32 is integrally provided on the peripheral edge of a plate-shaped bottom wall 31 and has a thin box shape. An example of the plurality of light sources 40 provided in the lamp box 30 is a linear light source as shown in FIG. In the present embodiment, the light source 40 will be described as a linear light source unless otherwise specified. An example of a linear light source used as the light source 40 is a cylindrical lamp such as a fluorescent tube (cold cathode tube), a halogen lamp, or a tungsten lamp. An example of the diameter of such a linear light source is about 2 mm to 4 mm. Here, the light source 40 is described as a linear light source, but the light source 40 is not limited to a linear light source, and may be a point light source. An example of a point light source is a light emitting diode (LED). Also in this case, it can be used as a direct type as shown in FIG.

  Next, the configuration of the light diffusion plate 50 included in the backlight system 20 will be described. FIG. 3 is a perspective view schematically showing a configuration of an embodiment of a light diffusing plate according to the present invention. FIG. 4 is a schematic diagram of a cross-sectional configuration along the line IV-IV in FIG. For convenience of explanation, the configuration of the light diffusing plate 50 will be described based on the state in which the light diffusing plate 50 is arranged as shown in FIG. 1, using the x direction, the y direction, and the z direction shown in FIG.

  The light diffusing plate 50 is a plate-like body having a light transmission property having a substantially square shape in plan view. As shown in FIGS. 3 and 4, the light diffusing plate 50 is a two-layer light in which a base layer 51 and a back layer 52 are laminated in the thickness direction in this order from the back side to the back layer 52 and the base layer 51. It is a diffusion plate.

  An example of the total thickness T of the light diffusion plate 50 obtained by adding the thickness t1 of the base material layer 51 and the thickness t2 of the back surface layer 52 is 0.1 mm to 10 mm. Moreover, the example of the thickness t1 of the base material layer 51 is 0.05 mm-9 mm, and the example of the thickness t2 of the back surface layer 52 is 0.03 mm-1 mm. The raw material for the light diffusion plate 50 is not particularly limited, and a known translucent resin can be used.

  Examples of the refractive index of the translucent resin are 1.46 to 1.62, and examples of the translucent resin are acrylic resin, styrene resin, polycarbonate, polyethylene, polypropylene, cyclic polyolefin, cyclic olefin copolymer. Polyethylene terephthalate, MS resin (methyl methacrylate-styrene copolymer resin), polystyrene resin, AS resin (acrylonitrile-styrene copolymer resin), and the like.

  The resin A as the raw material of the base material layer 51 and the resin B as the raw material of the back layer 52 may be the same or different. Further, each of the resin A and the resin B may be one using the above-described translucent resin alone, or may be a combination of two or more. As a combination of the resin A and the resin B, the same kind of translucent material is preferably used. Further, preferably, both of the resins A and B contain a styrene resin. Furthermore, it is preferable that both the resin A and the resin B are composed of only a styrene resin.

  The light diffusing plate 50 may contain a light diffusing agent such as light diffusing particles. The light diffusing agent is not particularly limited as long as it has a refractive index different from that of the translucent resin constituting the light diffusing plate 50 and can diffuse the light transmitted through the light diffusing plate 50. Examples of inorganic light diffusing agents are calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, silica, glass, talc, mica, white carbon, magnesium oxide, zinc oxide and the like. As the light diffusing agent, those obtained by subjecting the exemplified materials to surface treatment with a fatty acid or the like can also be used. Examples of the organic light diffusing agent include styrene polymer particles, acrylic polymer particles, and siloxane polymer particles. As the organic light diffusing agent, polymer polymer particles having a weight average molecular weight of 500,000 to 5,000,000, or crosslinked polymer particles having a gel fraction of 10% by mass or more when dissolved in acetone are more preferable. .

  When the light diffusing plate 50 contains a light diffusing agent, the mixing ratio of the light diffusing agent is 0.01 to 1 part by weight of the light diffusing agent with respect to 100 parts by weight of the translucent resin. More preferably, the amount is 0.001 to 0.01 parts by weight. The light diffusing agent can be used as a master batch in combination with a translucent resin that is a raw material mainly constituting the light diffusing plate 50. In addition, the absolute value of the difference between the refractive index of the light-transmitting resin as the main raw material of the light diffusing plate 50 and the refractive index of the light diffusing agent is 0.01 to 0.20 from the viewpoint of light diffusibility. 0.02-0.15 is more preferable.

  The light diffusing plate 50 may further contain additives such as an ultraviolet absorber, a heat stabilizer, an antioxidant, a weathering agent, a light stabilizer, a fluorescent brightening agent, and a processing stabilizer.

  Examples of ultraviolet absorbers are salicylic acid phenyl ester ultraviolet absorbers, benzophenone ultraviolet absorbers, triazine ultraviolet absorbers, and benzotriazole ultraviolet absorbers. The example of the addition amount of the ultraviolet absorber when adding the ultraviolet absorber is 0.1 to 3 parts by weight of the ultraviolet absorber with respect to 100 parts by weight of the translucent resin that is the main raw material of the light diffusion plate 50. is there. If it is this range, the bleeding to the surface of a ultraviolet absorber can be suppressed and the external appearance of the light-diffusion plate 50 can be maintained favorable.

  Examples of heat stabilizers are manganese compounds and copper compounds. The example of the addition method of a heat stabilizer is added with a ultraviolet absorber, and 2 weight part or less of a heat stabilizer with respect to 1 weight part of ultraviolet absorbers in translucent resin, More preferably, 0.01- It is to add at a ratio of 1 part by weight.

  Examples of the antioxidant are hindered phenol compounds and hindered amine compounds. An example of the addition amount of the antioxidant is 0.1 to 3 parts by weight of the antioxidant with respect to 100 parts by weight of the translucent resin.

  On the surface (second surface) 50a opposite to the base layer 51 of the back layer 52 of the light diffusion plate 50, fine concave portions or convex portions (hereinafter referred to as concave and convex portions) are distributed almost uniformly over the entire surface. The surface 50a is a so-called mat surface. The plurality of fine concavo-convex portions formed on the surface 50a can be formed by embossing, for example. The surface shape of the surface 50a can be represented by the surface roughness using the arithmetic average roughness Ra and the ten-point average roughness Rz of the surface 50a. An example of the arithmetic average roughness Ra of the surface 50a is a value measured in accordance with, for example, ISO-1997, and is 0.5 μm to 25 μm, preferably 1 μm to 20 μm. Moreover, the example of 10-point average roughness Rz of the surface 50a is 5 micrometers-110 micrometers by the value measured based on ISO-1997, for example, Preferably, they are 10 micrometers-100 micrometers. And the surface 50a can be made into the surface which satisfy | fills the said value illustrated as Ra and Rz simultaneously.

  A plurality of convex portions 53 are formed on the surface (first surface) 50 b opposite to the back surface layer 52 of the base material layer 51. Each convex portion 53 extends in the y direction (first direction), and the plurality of convex portions 53 are arranged in the x direction (direction orthogonal to the extending direction, second direction). In other words, a plurality of convex portions 53 are formed in a streak shape on the surface of the base material layer 51. An example of the cross-sectional shape orthogonal to the y direction (extending direction) of each convex portion 53 is a semicircular shape, and in this case, each convex portion 53 exhibits a cylindrical lens shape.

As shown in FIG. 4, the plurality of convex portions 53 can have a distance d [μm] between the adjacent convex portions 53. An example of a ratio (ha / P _l ) of the height ha [μm] of the convex portion 53 to the pitch P _{l when} the distance between the centers of the adjacent convex portions 53 (hereinafter referred to as a pitch) is P _l [μm]. Is 0.2 to 0.8. Here, it is assumed that there is a certain distance d between the adjacent convex portions 53, but d = 0 may also be used. In this case, P ₁ corresponds to the width of the convex portion 53.

Pitch P _l of the projections 53, when incorporating the light diffusion plate 50 to the liquid crystal display device 1 (see FIG. 1) is a value determined as moiré is not easily visible. Hereinafter, the conditions that the pitch _Pl satisfies will be described.

  First, the occurrence of moire will be described with reference to FIGS. 5A, 5B, 5C, and 5D. FIG. 5A is a schematic diagram of the liquid crystal display device 1 shown in FIG. In FIG. 5A, the surface 50a on the light source 40 side of the light diffusing plate 50 is schematically shown as a flat surface. FIG. 5B is a schematic diagram of a periodic structure of moire generated by the periodic structure of the light diffusion plate 50 and the liquid crystal panel 10. FIG. 5C is a schematic diagram of the transmittance profile of the liquid crystal panel 10. FIG. 5D is a schematic diagram of the transmittance profile of the light diffusing plate.

Since the plurality of convex portions 53 are arranged in parallel in the x direction at a pitch _Pl , the plurality of convex portions 53 have a periodic structure having a period _{Pl in} the x direction. The transmittance profile S1 based on this periodic structure is represented by S1 = E ₁ cos (2π (x / P _l )). “E ₁ ” in the equation indicates the amplitude of the transmittance profile S1.

The liquid crystal panel 10 includes a plurality of pixels 11, and the plurality of pixels 11 are regularly arranged in the x direction and the y direction. Accordingly, the liquid crystal panel 10 has a constant periodic structure in the x direction and the y direction. The pitch of the pixels 11 in the x direction of the liquid crystal panel 10 (the direction in which the plurality of protrusions 53 are arranged and the direction orthogonal to the extending direction of the protrusions 53) is P _p [μm] (where P _p ≠ P _l and 0. 5P _p ≠ P _l ), the transmittance profile S2 based on the periodic structure in the x direction in the liquid crystal panel 10 is represented by S2 = E ₂ cos (2π (x / P _p )). “E ₂ ” in the equation indicates the amplitude of the transmittance profile S2. The pitch P _p is expressed by P _p (μm) = L / N where the screen size in the x direction of the liquid crystal panel 10 is L (μm) and the number of pixels in the x direction is N (N is an integer of 1 or more). be able to.

In the liquid crystal display device 1, the periodic structure of the pitch P _l, and the periodic structure of the pitch P _p are stacked vertically. Therefore, the contrast S based on the periodic structure of the light obtained through the light diffusing plate 50 and the liquid crystal panel 10 is represented by S = S1 · S2. Here, S1 and S2 are as in Expression (5).

As shown in Expression (5) and FIG. 5B, the contrast S includes a high frequency component and a low frequency component. The high frequency component is not visually recognized because of its high frequency, and the low frequency component is visually recognized as so-called moire. Therefore, as shown in Expression (5), Moire pitch P _m 1 [μm] based on the periodic structure of pitch P _{p and} the periodic structure of pitch P _l is expressed by Expression (6).

The present inventors have made intensive studies, the liquid crystal panel 10, (1/2) pixel pitch, i.e., found that in some cases a change in transmittance 0.5P _p. Figure 6 shows an example of a case where transmittance 0.5P _p is changing. FIG. 6 shows a pixel image at a magnification of 200 times when the 32-inch FHD (Full High Definition) liquid crystal panel 10 is driven in the VA mode. The x direction and the y direction in FIG. 6 correspond to the x direction and the y direction in FIGS.

This period of 0.5P _p because of wide viewing angle, in one pixel 11 in the vicinity of the center of the x-direction is considered to be due to the alignment direction of liquid crystal molecules are different. FIG. 6 shows the case of the VA mode, but the same applies to the case of the IPS mode. In the case of the IPS mode, it is considered that the alignment direction of the liquid crystal molecules is different in the vicinity of the center in the x direction in one pixel 11 due to the comb electrode.

As described above, when the liquid crystal panel 10 further comprises a periodic structure of period 0.5P _p, the pitch P _{m 2} of moire caused by the periodic structure [[mu] m] is represented by the formula (7).

FIGS. 7 (a) and 7 (b), illustrates a transparent periodic structure having a period of pitch P _l, and the pitch of moire occurring when a combination of a liquid crystal panel, a relation between the pitch P ₁ It is. FIG. 7A and FIG. 7B show actual measurement values. Measurement values were obtained as follows. In a liquid crystal display device (liquid crystal television) having a 32-inch FHD and a 40-inch FHD liquid crystal panel, the above-mentioned periodic structure is arranged between the light source section and the liquid crystal panel, and moiré is observed in a dark room with white display. Then, the pitch of moire was measured. In the case of FIG. 7A, a 32-inch liquid crystal panel was used, and in the case of FIG. 7B, a 40-inch liquid crystal panel was used.

In FIG. 7A and FIG. 7B, “□” indicates a result when a light diffusing plate actually made of a translucent resin is used as the periodic structure. On the other hand, “◯” is the result when a light diffusion plate model (replica) made of silicon is used as the periodic structure. Although the raw material of the periodic structure is different as described above, the shape of the periodic structure is the same as that of the light diffusion plate shown in FIG. Further, in FIGS. 7A and 7B, the change of P _m 1 represented by the equation (6) with respect to P ₁ is shown by a solid line, and the P of P _m 2 represented by the equation (7) is shown in FIG. _The change with respect to _l is indicated by a broken line.

As shown in FIGS. 7A and 7B, the actual measurement values are mapped on the curves shown by the equations (6) and (7) regardless of the size of the liquid crystal panel 10. That is, it can be seen that a moire different from the moire based on the periodic structure of the pitch P _{p and} the periodic structure of the pitch _Pl of the liquid crystal panel 10 is generated. 7A and 7B, P _m 1 and P _m 2 calculated by the equations (6) and (7) represent the light diffusing plate 50 having a periodic structure with the pitch P _1. It can be seen that this corresponds to the pitch of moire generated when combined with the liquid crystal panel 10.

In the light diffusion plate 50, the pitch _Pl is
P _m 1 is
P _m 1 <1500 μm
And satisfy
P _m 2 is
P _m 2 <1500 μm
It is a value that satisfies.

P _m 1 and P _m 2 are moire pitches that may appear when the light diffusing plate 50 is mounted on the liquid crystal display device 1 as shown in FIG. In the light diffusion plate 50, _{P l} is set so that the pitch _{P m} 1 and the pitch _{P m} 2 is smaller than any 1500 .mu.m. Therefore, when the liquid crystal display device 1 is driven, moire is difficult to be visually recognized. Examples of such pitch _{P l} is 30μm or more 700μm or less. The pitch _{P l,} of the illustrated range, preferably 50μm or more 500μm or less, more preferably 150μm or more 400μm or less.

  From the viewpoint of further suppressing the moiré from being visually recognized, an optical film portion 60 may be provided between the light diffusion plate 50 and the liquid crystal panel 10 as shown in FIG. FIG. 8 is a schematic diagram of a cross-sectional configuration of the liquid crystal display device 1 when including an optical film portion. In FIG. 8, the case where the optical film part 60 has the three optical films 61 is illustrated. The kind and the number of optical films 61 constituting the optical film unit 60 may be selected so that the haze value H (%) of the optical film unit 60 satisfies 95 ≦ H ≦ 99.9. The haze value H is the total haze of all the optical films 61 constituting the optical film unit 60. The haze value H is a value measured according to JIS-K7136 (ISO 14782).

  Examples of the optical film 61 are a diffusion film, a prism film, a reflective polarization separation film, a retardation film, a polarizing film, and the like. The optical film unit 60 may be a stack of one or more of the same type of optical film, or may be a stack of one or more of a plurality of different types of optical films. Here, each film mentioned as an example of the optical film 61 will be described.

  A diffusion film is for diffusing and irradiating incident light. An example of the diffusion film is obtained by fixing beads on one surface of a transparent resin film with a binder. Specifically, “D121U series” manufactured by Tsujiden Co., Ltd., “Light Up TM” manufactured by Kimoto Co., Ltd., and the like.

  In the example of the prism film, a plurality of condensing lenses are formed on the surface disposed on the liquid crystal panel 10. Each condensing lens extends in one direction, and the plurality of condensing lenses are arranged in parallel in a direction orthogonal to the extending direction of the condensing lens. Examples of the fine condensing lens are a convex lens and a lenticular lens that are convex outward, and may be a prism lens having a triangular cross section.

  The reflective polarization separation film transmits predetermined polarized light and reflects polarized light having a property opposite to that of the predetermined polarized light. Examples of the reflective polarization separation film include a reflective linear polarization separation film that transmits linearly polarized light in a specific vibration direction and reflects linearly polarized light in a vibration direction orthogonal to the specific vibration direction, circularly polarized light in a predetermined rotation direction And a reflection type circularly polarized light separating film that reflects circularly polarized light that rotates in the direction opposite to the predetermined rotation direction. Examples of the reflective linearly polarized light separating film are “DBEF (Dual Brightness Enhancement Film)” manufactured by Sumitomo 3M Limited and “NIPOX” manufactured by Nitto Denko Corporation.

  The retardation film has a retardation (retardation) by stretching a resin film. Examples of the retardation film are a polycarbonate resin film, a polysulfone resin film, a polyether sulfone resin film, a polyarylate resin film, and a norbornene resin film. Specifically, “Elmec” manufactured by Kaneka Corporation and “Sumikalite” manufactured by Sumitomo Chemical Co., Ltd.

  The polarizing film is a film that transmits light that vibrates in a certain direction. Specific examples of the polarizing film are “NPF” manufactured by Nitto Denko Corporation and “Sumikaran” manufactured by Sumitomo Chemical Co., Ltd.

[Method of manufacturing light diffusion plate]
Next, an example of the manufacturing method of the light diffusing plate in this embodiment is demonstrated. The light diffusing plate 50 is manufactured by forming a plurality of convex portions 53 on one surface of a resin sheet and cutting out the resin sheet having the convex portions 53 into a predetermined size. As shown in FIG. 9, the manufacturing method of the light diffusing plate 50 includes a design step S10 for designing a plurality of convex portions 53 to be shaped, and a convex portion 53 designed on a resin sheet. And a manufacturing process S20. FIG. 9 is a flowchart showing a method for manufacturing a light diffusing plate. Hereinafter, each step will be described.

<Design process>
In the design step S <b> 10, the pitch P _l of the convex portion 53 is determined based on the pixel pitch P _p of the liquid crystal panel 10 combined with the light diffusing plate 50, and the equations (6) and (7). A concavo-convex pattern including a plurality of convex portions 53 to be shaped is determined. Here, it is assumed that the cross-sectional shape of each convex portion 53 has been designed (for example, semicircular), but the cross-sectional shape of the convex portion 53 may be designed in this design step S10.

<Manufacturing process>
In the manufacturing process S20, the resin sheet 70 is manufactured by using the light diffusion plate manufacturing apparatus 80 shown in FIG. 10A, and the designed convex portion 53 is formed on one surface 70a of the resin sheet 70. To do. The manufacturing apparatus 80 of the light diffusing plate 50 shown in FIG. 10 will be described.

  The manufacturing apparatus 80 takes out the resin sheet 70, a sheet molding machine 90 that extrudes the raw material resin into a sheet shape, a pair of pressing rolls 100 that further mold the extruded resin sheet 70 by pressing. And a take-up roll group 110.

  The sheet molding machine 90 includes a first extruder 91 for heating and melting the resin A that is the raw material of the base layer 51, and a second extruder 92 for heating and melting the resin B that is the raw material of the back layer 52, The feed block 93 to which the resin melted by the first extruder 91 and the second extruder 92 is supplied, and a die 94 for extruding the resin in the feed block 93 in a sheet state. The first and second extruders 91 and 92 are provided with hoppers 95 and 96 for introducing resin into the cylinders of the extruder.

  The pressing roll group 100 includes three pressing rolls 101, 102, and 103. Each of the three pressing rolls 101 to 103 is a cylindrical metal roll. The rotation axes of the pressing rolls 101 to 103 are parallel to each other. In the embodiment shown in FIG. 10A, the three pressing rolls 101 to 103 are continuously arranged in the vertical direction, and the rotation axis is horizontal. Here, although it demonstrates based on embodiment shown to Fig.10 (a), the arrangement | positioning relationship of the three press rolls 101-103 is not limited to the form shown to Fig.10 (a). For example, the pressing rolls 101 to 103 may be continuous in the horizontal direction. The rotation shafts of the three pressing rolls 101 to 103 are connected to driving means such as motors (not shown).

The peripheral surface 101a of the pressing roll 101 is a smooth surface. On the other hand, a mat transfer mold for forming the surface 50a including the fine irregularities shown in FIG. 3 on the peripheral surface 102a of the press roll 102 as an intermediate roll located between the press roll 101 and the press roll 103. 104 is provided. The surface of the mat transfer mold 104 is a mat surface on which an embossed shape composed of a concavo-convex pattern opposite to the concavo-convex pattern to be formed on the surface 50a is distributed almost uniformly. An example of the arithmetic average roughness Ra of the mat surface is a value measured according to ISO-1997, and is 6 μm to 30 μm. An example of the ten-point average roughness Rz is measured according to ISO-1997. The measured value is 45 μm to 150 μm. In FIG. 10A, an intaglio transfer mold 105 for forming the convex portion 53 is provided on the peripheral surface 103 a of the press roll 103 as a lower roll located on the lower side of the press roll 102. In the intaglio transfer mold 105, a plurality of concave grooves opposite to the convex portions 53 are formed in a streak shape along the circumferential direction of the pressing roll 103. That is, the groove has a substantially semicircular arc-shaped cut surface orthogonal to the longitudinal direction (circumferential direction), and the distance (pitch) between the centers of adjacent grooves is designed in the design step S10. Corresponds to the pitch _Pl .

  The mat transfer mold 104 may be provided on the pressing roll 103, and the intaglio transfer mold 105 may be provided on the intermediate pressing roll 102. Further, the peripheral surface 102a of the pressing roll 102 may be a smooth surface. In this case, the back surface 50a of the light diffusing plate 50 is a smooth surface.

  An organic material can be used as a raw material for the mat transfer mold 104 and the intaglio transfer mold 105. The organic material as the raw material of the mat transfer mold 104 and the intaglio transfer mold 105 has heat resistance that can maintain the shape of the transfer mold even when repeatedly pressed against the resin sheet 70 immediately after being extruded from the die 94 in a heated and melted state. What is necessary is just to have. Examples of the organic material include a thermosetting resin and a thermoplastic resin.

  The pressing roll group 100 rotates both the pressing roll 101 and the pressing roll 103 counterclockwise by the driving means, and rotates the pressing roll 102 clockwise so that both sides of the resin sheet 70 extruded from the sheet forming machine 90 are applied. The resin sheet 70 can be molded while being processed.

  The take-up roll group 110 has a pair of take-up rolls 111 and 112. The take-up rolls 111 and 112 sandwich the resin sheet 70 from both sides in the thickness direction of the resin sheet 70. Each of the take-up rolls 111 and 112 is a cylindrical metal roll. As shown in FIG. 10A, the pair of take-up rolls 111 and 112 are installed so that the resin sheet 70 can be horizontally conveyed while maintaining the height immediately after being sent from the pressing roll 103.

  Next, the manufacturing process S20 of the light diffusing plate 50 using the manufacturing apparatus 80 of the light diffusing plate 50 will be described with reference to FIGS. As shown in FIG. 9, the manufacturing process S20 includes a sheet manufacturing process S21, a transfer process S22, and a light diffusion plate forming process S23.

(1) Sheet manufacturing process S21
Resin A that is a raw material of the base material layer 51 is put into the hopper 95 of the first extruder 91. The first extruder 91 melts and kneads the resin A, and then supplies the melted and kneaded resin A to the feed block 93. Resin B as the raw material of the back layer 52 is put into the hopper 96 of the second extruder 92. The second extruder 92 melts and kneads the resin B, and then supplies the melted and kneaded resin B to the feed block 93. An example of the cylinder temperature of the first extruder 91 and the second extruder 92 is about 190 ° to 250 °. Next, the die 94 coextrudes the resin in the feed block 93. Thereby, as shown in FIG. 10B, the two-layer resin sheet 70 is extruded from the die 94. FIG. 10B is a partially enlarged view of the region α in FIG. In the embodiment shown in FIG. 10A, the lower layer 71 of the extruded resin sheet 70 is a layer to be the back layer 52, and the upper layer 72 is the layer to be the base material layer 51.

(2) Transfer process S22
The resin sheet 70 extruded from the die 94 is sandwiched and pressed between the pressing roll 101 and the pressing roll 102 and is conveyed according to the rotation of the pressing roll 102. At this time, the resin sheet 70 is cooled. Since the mat transfer mold 104 is provided on the pressing roll 102, when the pressing roll 101 and the pressing roll 102 press the resin sheet 70, the shape of the mat transfer mold 104 is transferred to the surface 70 b of the resin sheet 70. A large number of fine irregularities are formed. The surface temperatures of the pressure roll 101 and the pressure roll 102 are preferably lower than the extrusion temperature of the resin sheet 70, and examples of the surface temperature of the pressure roll 101 and the pressure roll 102 are about 50 ° C to 120 ° C.

  After being pressed and conveyed by the pressing roll 101 and the pressing roll 102, the resin sheet 70 is sandwiched and pressed between the pressing roll 102 and the pressing roll 103. As a result, the surface shape of the intaglio transfer mold 105 is transferred to the surface 70 a of the resin sheet 70. As a result, a large number of convex portions parallel to the flow direction (feeding direction) of the resin sheet 70 are formed on the surface 70a. An example of the surface temperature of the pressing roll 103 is about 50 ° C to 120 ° C.

  After the resin sheet 70 is sandwiched and pressed between the pressing roll 102 and the pressing roll 103 as described above, the resin sheet 70 is conveyed in close contact with the peripheral surface of the pressing roll 103, and is sent in the horizontal direction from the lower end of the pressing roll 103. The

(3) Light diffusing plate forming step S23
The resin sheet 70 is taken up by the pair of take-up rolls 111 and 112, and the resin sheet 70 having a predetermined shape on both upper and lower surfaces is manufactured. After further cooling the resin sheet 70, the light diffusing plate 50 is obtained by cutting out in a desired size (predetermined region). Usually, the cut-out size of the light diffusion plate 50 is slightly larger than the screen size of the liquid crystal display device 1 to be mounted because it is assembled by pressing four sides with a resin or metal frame when mounted.

The light diffusing plate 50 illustrated in FIGS. 3 and 4 can be manufactured by the above manufacturing method. When the light diffusing plate 50 manufactured in this way is mounted on the backlight system 20 and the liquid crystal display device 1, as shown in FIG. 1, it faces the bottom wall 31 of the lamp box 30 and opens the opening. A light diffusing plate 50 is provided on the lamp box 30 so as to close it. In this case, the light diffusion plate 50 and the liquid crystal panel 10, the design conditions employed in the design process S10, in particular, the arrangement direction of the convex portion 53 at a pitch P _l, the direction in which the pixel 11 at the pitch P _p are arrayed Arrange so that and match. Further, when the light source 40 is a linear light source, the extending direction of the light source (linear light source) 40 and the extending direction of the convex portion 53 substantially coincide (in FIG. 1, both are in the y direction). Arrange them so that.

  When the light source 40 of the backlight system 20 is turned on, the light output from the light source 40 is reflected directly or on the surface of the bottom wall portion 31 of the lamp box 30 and enters the light diffusion plate 50. Since the plurality of convex portions 53 are formed in a streak shape on the surface 50b of the light diffusing plate 50 on the liquid crystal panel 10 side, when light is emitted from the translucent light diffusing plate 50, the light is at the emission position. In response, the light is emitted in various directions. Thereby, the light from the light source 40 is diffused and emitted as planar light. Since the liquid crystal panel 10 is irradiated with this planar light, the liquid crystal panel 10 can be driven to display an image.

Pitch _{P l} of the convex portion 53 of the light diffusing plate 50, the pitch _{P m} 1 and _{P m} 2 of the formula (6) and (7), the _{P m 1,} satisfy the P m 1 <1500μm And P _m 2 is a value satisfying P _m 2 <1500 μm. Therefore, the moire pitch that may occur when the light diffusing plate 50 is mounted on the liquid crystal display device 1 is smaller than 1500 μm. As a result, it is difficult for the moire to be visually recognized, and the image quality of the display image by the liquid crystal panel 10 can be improved.

This will be described in more detail. In the present embodiment, the pitch P ₁ of the convex portion 53 is determined so that the moire pitches P _m 1 and P _m 2 represented by the equations (6) and (7) are less than 1500 μm. Therefore, not only the moire that can be generated by the periodic structure having the pitch P ₁ as the period and the periodic structure having the pitch P _p as the period, but also the 0.5P _p pitch ((1/2 pixel pitch) which the present inventors have paid attention to. The pitch P _l is determined so as to suppress the moiré associated with the periodic structure due to the liquid crystal panel 10), so that the light diffusion plate 50 is used for the liquid crystal panel 10 having the pixel pitch P _p , whereby the liquid crystal of the liquid crystal panel 10 is used. It is also possible to suppress the visibility of moire due to the 1/2 pixel pitch resulting from the change in transmittance due to the molecular orientation direction division.

Furthermore, as shown in FIGS. 7A and 7B, the equations (6) and (7) correspond to the pitch of the moiré that actually occurs. As a result, by determining P ₁ based on P _m 1 and P _m 2 defined by Expression (6) and Expression (7), it is difficult to more reliably recognize moire.

Further, as illustrated in FIG. 8, the haze value H (%) is between the light diffusion plate 50 and the liquid crystal panel 10.
95 ≦ H ≦ 99.9
When the optical film part 60 satisfying the above is provided, the moire can be further concealed. When the optical film unit 60 is provided in this manner, for example, moire is less likely to be visually recognized without depending on the distance between the liquid crystal panel 10 and the observation position (for example, even when approaching the liquid crystal panel 10).

In order to further visually by state hard moire, as _{P m} 1 and _{P m} 2 is 1000μm or less, it is preferable to design the _{P l.} In this case, even if the optical film portion 60 described above is not provided, or even if the haze value H (%) of the optical film portion 60 does not satisfy the above conditions, the generated moire pitch is 1000 μm or less. It becomes difficult to see.

For the liquid crystal panel 10 in which the pitch P _p of the pixels 11 in the arrangement direction of the protrusions 53 (x direction in FIG. 1) is in the range of 440 μm to 535 μm, the pitch P ₁ is in the range of 325 μm to 335 μm. Is preferably used. The one of the light diffusion plate 50 the convex portion 53 is formed in _{P l} of 335μm any of the following values or 325Myuemu, when combined in the liquid crystal panel 10 _{P p} is equal to or less than 535μm above 440 .mu.m, any of the liquid crystal panel This is because even when combined with 10, the visibility of moire can be reduced. In this case, in the manufacturing apparatus 80, the necessity of changing the pressing roll 103 on which the intaglio transfer mold is formed for each liquid crystal panel 10 having a different size is reduced, so that the production cost of the liquid crystal display device 1 can be reduced. Is possible.

  Next, based on an Example and a comparative example, the effect of a light diffusing plate is demonstrated. Below, for convenience of explanation, in Examples 1 to 16 as well as Comparative Examples 1 to 7, elements corresponding to those of the above embodiment are given the same reference numerals.

In Examples 1 to 16 and Comparative Examples 1 to 7, a liquid crystal display device 1 having a liquid crystal panel 10 of a predetermined size is prepared, and light diffusion plates 50 having different pitches _Pl are mounted on the liquid crystal display device 1. The presence or absence of moire in white display was visually evaluated in a dark room.

The pitches P _p of the liquid crystal panels 10 used in Examples 1 to 16 and Comparative Examples 1 to 7 and the pixels 11 of the respective liquid crystal panels 10 are as shown in FIGS. 11 and 12, respectively. FIG. 11 is a chart showing implementation conditions and evaluation results in Examples 1 to 14 and Comparative Examples 1 to 5. FIG. 12 is a chart showing implementation conditions and evaluation results in Examples 11, 13, 15, and 16 and Comparative Examples 6 and 7. As described above, FHD in FIGS. 11 and 12 is an abbreviation for Full High Definition. WXGA is an abbreviation for Wide eXtended Graphics Array. In the charts of FIGS. 11 and 12, “32 inches” and the like are abbreviated as “32”.

  The raw material of the light diffusing plate used in each of Examples 1 to 16 and Comparative Examples 1 to 7 and the manufacturing method of the light diffusing plate were the same. The raw material of the resin sheet used as Examples 1-16 and Comparative Examples 1-7 used as the light diffusing plate 50, the manufacturing apparatus of a light diffusing plate, and the optical film part used suitably are demonstrated.

<Raw material of resin sheet>
As raw materials for the resin sheet 70, the following raw materials (1) and (2) were prepared.
(1) Translucent resin A
Styrene resin (Toyo Styrene "HRM40" refractive index 1.59)
(2) Translucent resin B
Styrene resin (Toyo Styrene "HRM40" refractive index 1.59)
<Light diffusion plate manufacturing equipment>
The light diffusing plate 50 of Examples 1-16 and Comparative Examples 1-7 was manufactured using the manufacturing apparatus 80 shown to Fig.10 (a). The following were used for the press rolls 101-103 which comprise the press roll group 100 of the manufacturing apparatus 80. FIG.
-As the pressing roll 101, a metallic roll having a diameter of 450 mm with a mirror-finished peripheral surface 101a was used.
A metal roll having a diameter of 450 mm was used as the pressing roll 102. A mat transfer mold 104 is provided on the peripheral surface 102 a of the pressing roll 102.
A metal roll having a diameter of 450 mm was used as the pressing roll 103. An intaglio transfer mold 105 was provided on the peripheral surface 103 a of the pressing roll 103.
<Optical film part>
The optical film unit 60 is composed of three optical films 61. The optical films 61 used are all diffusion films. Specifically, D121UY / D121UY / D121UZ manufactured by Tsujiden Co., Ltd. was used in order from the optical film 61 on the light diffusion plate 50 side. The total haze of the three diffusion films, that is, the haze value H of the optical film portion 60 was 99.2%. In addition, the measurement of the haze value H was performed based on JIS-K7136 (ISO 14782) using HM-150 by Murakami Color Research Laboratory Co., Ltd.

  The light diffusing plate 50 was manufactured for Examples 1 to 16 and Comparative Examples 1 to 7 in the same manner as the manufacturing method described with reference to FIGS. 9 and 10A. That is, the resin A and the resin B were melt-kneaded by the first extruder 91 and the second extruder 92 whose temperatures in the cylinder were 190 ° C. to 250 ° C., respectively, and then supplied to the two-layer distribution type feed block 93. The amounts of translucent resin A and translucent resin B charged into the first extruder 91 and the second extruder 92, respectively, were 100 parts by weight.

  Next, the resin in the feed block 93 was co-extruded from the die 94 at an extrusion resin temperature of 250 ° C. to obtain a two-layer resin sheet 70. At this time, the resin supplied from the first extruder 91 to the feed block 93 was adjusted to be the base layer 51, and the resin supplied from the second extruder 92 to the feed block 93 was adjusted to be the back layer 52. Thereafter, the pressure roll group 100 was passed as described above. Accordingly, the width is 1300 mm, the total thickness T is 2.0 mm (the thickness t1 of the base layer 51 is 1.95 mm, and the thickness t2 of the back layer 52 is 0.05 mm), and the surface 70a has a plurality of protrusions. The resin sheet 70 in which the portion 53 was formed and the fine unevenness was formed on the surface 70b was produced. At this time, the surface temperature of the pressing roll 101 was 65 ° C., the surface temperature of the pressing roll 102 was 77 ° C., and the surface temperature of the pressing roll 103 was 98 ° C. The production speed of the resin sheet 70 was 4.7 m / min. The resin sheet 70 thus manufactured was cut into a predetermined size to obtain a light diffusing plate 50.

In the above manufacturing method, an intaglio transfer mold 105, in other words, appropriate use what the press rolls 103, corresponding to the pitch _{P l} of Examples 1 to 16 and Comparative Examples 1 to 7 shown in FIGS. 10 and 11 By doing, the light diffusing plate 50 with respect to each Examples 1-16 and Comparative Examples 1-7 was obtained. Moreover, the magnitude | size of the light diffusing plate 50 of each Examples 1-16 and Comparative Examples 1-7 is the magnitude | size of the liquid crystal panel 10 used for moire evaluation in each Examples 1-16 and Comparative Examples 1-7. It was in accordance. Accordingly, when the moire is evaluated using the liquid crystal panel 10 having the same size, the size of the light diffusion plate 50 is also the same.

<Moire evaluation method>
The light diffusing plate 50 prepared for each of Examples 1 to 16 and Comparative Examples 1 to 7 is combined with the liquid crystal panel 10 shown in FIGS. 11 and 12 to provide the liquid crystal display device 1 (see FIG. 2 or FIG. 8). Configured. The light source 40 in each liquid crystal display device 1 was a linear light source. Then, white display was performed, and the presence or absence of moire in a dark room was visually confirmed from the front and oblique directions. The driving method of the liquid crystal panel 10 is as shown in FIGS. The moiré was evaluated under the same conditions except that the light diffusion plate 50 was replaced for the liquid crystal panel 10 having the same size.

(Evaluation method of Examples 1-14 and Comparative Examples 1-5)
For Examples 1 to 14 and Comparative Examples 1 to 5, as the configuration of the liquid crystal display device 1 illustrated in FIG. 1, moire was confirmed in a state where the optical film unit 60 was not mounted. As a result, when even a part of the moire was visually recognized, the optical film unit 60 was mounted as shown in FIG.
(Evaluation methods of Examples 15 and 16 and Comparative Examples 6 and 7)
For Examples 15 and 16 and Comparative Examples 6 and 7, in order to evaluate the versatility of the light diffusing plate 50 as compared with Examples 11 and 13, the moire was mounted with the optical film portion 60 mounted from the beginning. The presence or absence was confirmed.

<Moire evaluation result>
The moire evaluation results will be described separately for the cases shown in FIGS. 11 and 12, P _m 1 and P _m 2 are obtained by substituting P _p and P _l of each of Examples 1 to 16 and Comparative Examples 1 to 7 into Equations (6) and (7). Calculated value. In FIGS. 11 and 12, _{P m} 1 and _{P m} 2 indicates the numerical values obtained by rounding off the last two digits. In the “moire evaluation” column, “X” is indicated when the moire can be visually recognized, and “◯” is indicated when the moire cannot be visually recognized.

(Moire evaluation results shown in FIG. 11)
In Examples 1 to 3, 5 to 7, 9, 10, and 14 in which P _l is designed so that P _m 1 and P _m 2 are 1000 μm or less, moire is generated even when the optical film portion 60 is not provided. It turns out that it is not visually recognized. Also, when also consider including when equipped with the optical film portion 60, when using a light diffusion plate 50 of Example 1 to 14, _{P m} 1 and _{P m} 2 derived from the pitch _{P l} and _{P p} is less than 1500μm It is. In other words, in the light diffusion plates 50 of Examples 1 to 14, the pitch _Pl is set so that P _m 1 and P _m 2 are less than 1500 μm. In this case, as shown in FIG. 11, it turns out that a moire is not visually recognized. As a result, it was confirmed that display performance with excellent uniformity was obtained.

On the other hand, in the light diffusing plates 50 of Comparative Examples 1 to 5, either P _m 1 or P _m 2 does not satisfy the condition of less than 1500 μm. In this case, as shown in FIG. 11, even if the optical film part 60 is included, it can be seen that moire is visible. Considering this point, in Examples 4, 8, and 11 to 13, it can be seen that the moire can be suppressed to the extent that the moire can be concealed by providing the optical film portion 60.

(Moire evaluation results shown in FIG. 12)
Also in Examples 15 and 16, P _m 1 and P _m 2 are less than 1500 μm. In other words, in the light diffusion plates 50 of Examples 15 and 16, the pitch _Pl is set so that P _m 1 and P _m 2 are less than 1500 μm. In this case, as shown in FIG. 12, moire is not visually recognized. As a result, it was confirmed that display performance with excellent uniformity was obtained. Also, as shown in FIG. 12, the pitch P _p of Examples 11, 13, 15, and 16 is in the range of 440 μm to 535 μm, and the pitch P _{l of} Examples 11, 13, 15, and 16 is 325 μm. It is 335 μm or less. In the case of satisfying such conditions Example 11,13,15,16, regardless of the difference of the pitch _{P p} of the pixel 11, a pitch _{P l} (Example 11,13,15,16 in _{P l} = 330 μm), it is possible to realize difficulty in visually recognizing moire. On the other hand, in Comparative Examples 6 and 7, P _p is 364 μm, which is out of the range of 440 μm to 535 μm. In this case, moire was visually recognized even when the pitch _Pl was the same as that of Example 11 or the like.

In FIG. 12, since the embodiments are classified according to the combination with the liquid crystal panel 10, the embodiments are separated from the embodiments 11, 13, 15, and 16. However, since the pitch _{P l} it is the same, the light diffusing plate 50 itself of the configuration is the same in Example 11,13,15,16. Therefore, it can be seen that the moire can be reduced with one light diffusion plate 50 regardless of the size of the liquid crystal panel 10.

  Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the spirit of the invention.

  Although the example of the optical element part which the light diffusing plate 50 has was demonstrated as the convex part 53, an optical element part can also be made into a recessed part. Furthermore, although the optical element portion such as the convex portion 53 is formed on the surface 50b on the liquid crystal panel 10 side, it may be formed on the surface 50a, or may be formed on either the surface 50a or the surface 50b. It may be. Further, although the light diffusing plate has been described as a light diffusing plate having a two-layer structure, the light diffusing plate may have a one-layer structure or may have a layer structure of three or more layers. Furthermore, although the cross-sectional shape of the convex part 53 illustrated the semicircle, the convex part 53 will not be specifically limited if it is a shape which produces the spreading | diffusion effect | action of the light diffusing plate 50. FIG.

  Moreover, although the light source 40 illustrated the linear light source, point light sources, such as a light emitting diode, can also be used. Moreover, when using the optical film part 60, haze value H of the optical film part 60 illustrated 95% or more and 99.9% or less. However, the haze value H of the optical film unit 60 may be 90% or more and 99.9% or less, and may be 80% or more and 99.9% or less. In addition, it is preferable from a viewpoint which suppresses visual recognition of a moire, so that a lower limit is high.

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device, 10 ... Liquid crystal panel, 11 ... Pixel, 13a ... Surface (incident surface of liquid crystal panel), 20 ... Backlight system (surface light source device), 30 ... Lamp box (light source part), 40 ... Light source ( Light source part), 50 ... Light diffusion plate, 50a ... Surface (second surface), 50b ... Surface (first surface), 53 ... Convex part (optical element part), 60 ... Optical film part, 61 ... Optical film , 70: Resin sheet (plate-like body), 70a: One surface of the resin sheet, 103: Pressing roll (roll).

Claims (13)

A light diffusing plate provided on the incident surface side of the liquid crystal panel,
A plurality of optical element portions formed on at least one of the first surface on the liquid crystal panel side and the second surface facing the first surface;
Each optical element portion extends in a first direction;
The plurality of optical element portions are arranged in parallel in a second direction substantially orthogonal to the first direction,
The pitch of the plurality of optical element portions in the second direction is P _l [μm], and the pixel pitch of the plurality of pixels included in the liquid crystal panel is P _p [μm] (where P _p ≠ P _l and 0.5P _p ≠ P _l ), and the moire pitch of the moire based on the periodic structure in the second direction of the plurality of optical element portions and the plurality of pixels is P _m 1 [μm] and P _m 2 [μm], and P _m 1 and P _m 2 are expressed by the formula (1) and the formula (2), respectively,
The _{P l,} the _{P m} 1 satisfies _P m 1 <1500 .mu.m, and the _{P m} 2 is a value satisfying _P m 2 <1500 .mu.m,
Light diffusion plate.

The _{P l,} the _{P m} 1 satisfies _{P m} 1 ≦ 1000 .mu.m, and the _{P m} 2 is a value satisfying _{P m} 2 ≦ 1000 .mu.m, the light diffusing plate of claim 1, wherein. The P _p is not less than 440 μm and not more than 535 μm,
Wherein _{P l} is equal to or less than 335μm or 325μm,
The light diffusing plate according to claim 1 or 2. When the width of the liquid crystal panel in the second direction is L [μm], and the number of the pixels in the second direction is N (N is an integer of 1 or more),
The P _p is represented by L / N.
The light diffusing plate as described in any one of Claims 1-3.   The light diffusing plate according to claim 1, wherein the optical element portion is a convex portion. A surface light source device for supplying light to a liquid crystal panel,
A light source unit that outputs illumination light to the liquid crystal panel;
The light diffusion plate according to any one of claims 1 to 5, provided between the light source unit and the liquid crystal panel,
A surface light source device comprising: LCD panel,
A light diffusing plate according to any one of claims 1 to 5, provided between a light source unit that outputs illumination light to the liquid crystal panel, and the light source unit and the liquid crystal panel.
A liquid crystal display device comprising: An optical film part including at least one optical film is further provided between the liquid crystal panel and the light diffusion plate,
The liquid crystal display device according to claim 7, wherein a haze value H (%) of the optical film portion satisfies 95 ≦ H ≦ 99.9. The light, which is a light diffusing plate provided on the incident surface side of the liquid crystal panel and has a surface in which a plurality of optical element portions extending in the first direction are arranged in parallel in a second direction orthogonal to the first direction A method of manufacturing a diffusion plate,
A design step of designing a pitch P ₁ [μm] with respect to the second direction of the plurality of optical element portions;
Based on the P _l that are designed based on the design process, a plurality of the optical element unit, the light diffusion plate is formed on one surface of said has a transparent light diffusing plate and comprising a plate-like body Manufacturing process for manufacturing,
With
In the design step, when the light diffusion plate is disposed with respect to the liquid crystal panel in the liquid crystal display device, the pixel pitch in the second direction of the plurality of pixels of the liquid crystal panel is set to P _p [μm] ( Here, P _p ≠ P _l and 0.5P _p ≠ P _l ), and the moire pitch of the moire based on the periodic structure in the second direction of the plurality of optical element portions and the plurality of pixels is set to P _m 1 [μm] and When P _m 2 [μm] and P _m 1 and P _m 2 are expressed by the formula (3) and the formula (4), respectively,
The _{P l,} wherein _{P m} 1 satisfies _P m 1 <1500 .mu.m, and the _{P m} 2 is determined as a value satisfying _P m 2 <1500 .mu.m,
Manufacturing method of light diffusing plate.

In the design process,
The _{P l,} wherein _{P m} 1 satisfies _{P m} 1 ≦ 1000 .mu.m, and the _{P m} 2 is determined as a value satisfying _{P m} 2 ≦ 1000 .mu.m,
The manufacturing method of the light diffusing plate of Claim 9. The P _p is not less than 440 μm and not more than 535 μm,
Wherein _{P l} is equal to or less than 335μm or 325μm,
The manufacturing method of the light diffusing plate of Claim 9 or 10. When the width of the liquid crystal panel in the second direction is L [μm], and the number of the pixels in the second direction is N (N is an integer of 1 or more),
The P _p is represented by L / N.
The manufacturing method of the light diffusing plate as described in any one of Claims 9-11. The manufacturing process includes
A sheet production step of producing a resin sheet as the plate-like body by extrusion;
The transfer mold is transferred onto the one surface by pressing a roll having, as a transfer mold, a mold opposite to the plurality of optical element portions arranged at the pitch _Pl designed in the design process on one surface of the resin sheet. A transfer process,
A light diffusing plate forming step of cutting out a predetermined region of the resin sheet in which the transfer mold is transferred and a plurality of the optical element portions are formed on the one surface;
Having
The manufacturing method of the light diffusing plate as described in any one of Claims 9-12.