JP2009043506A - Backlight device, liquid crystal display device, optical member, and lenticular lens sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight device capable of suppressing luminance irregularity, and of keeping a large width of viewing angle dependency of luminance in a predetermined axis direction large. <P>SOLUTION: This backlight device is provided with a surface light source, a lenticular lens sheet 31, and a diffusion sheet 32. The surface light source includes a plurality of linear light sources arranged in parallel to one another. The lenticular lens sheet 31 is installed over the surface light source. The lenticular lens sheet 31 has a plurality of cylindrical lenses arranged in parallel to one another in the direction in which the linear light sources are arranged in parallel to one another, and also has a plurality of flat sections each formed between adjacent cylindrical lenses. The pitch Pc of the plurality of cylindrical lenses, the width Wf of the flat section, and the height Hc of the cylindrical lens satisfy expression (1) and expression (2). The diffusion sheet 32 is installed over the cylindrical lenses and has a haze of 70-80%. Expression (1): 1/16≤Wf/Pc <1/6, and Expression (2): 5/16≤Hc/Pc≤1/2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a backlight device, a liquid crystal display device, an optical member, and a lenticular lens sheet, and more particularly, a direct backlight device, a liquid crystal display device using the backlight device, an optical member used in the backlight device, and The present invention relates to a lenticular lens sheet used for an optical member.

  A liquid crystal display device is required to have high front luminance. Therefore, the backlight device used for the liquid crystal display device includes an optical member that improves the front luminance. As disclosed in Japanese Patent No. 3262230 (Patent Document 1), a prism sheet is generally used as an optical member.

  When a prism sheet is used, moire fringes are likely to occur because the prism lens interferes with the pixels of the liquid crystal panel. Japanese Patent Laying-Open No. 2006-235014 (Patent Document 2) discloses a technique for preventing such moire fringes. Specifically, a diffusion sheet is laid between the prism sheet and the liquid crystal panel. As a result, the occurrence of moire fringes is suppressed.

  Certainly, if a diffusion sheet is laid between the prism sheet and the liquid crystal panel, the prism sheet does not interfere with the liquid crystal panel, and moire fringes are eliminated. However, if a diffusion sheet is laid on the prism sheet, there arises a problem that the viewing angle on the display screen of the liquid crystal display device becomes narrow.

  In particular, in the case of a liquid crystal display device, it is preferable that the viewing angle in the left-right direction (that is, horizontal direction) of the display screen is wide. This is because the user of the liquid crystal display device has more opportunities to view the display screen from the left and right oblique directions than the opportunity to view the display screen from the oblique direction. Therefore, it is preferable that the viewing angle in at least the left-right direction is wide on the display screen of the liquid crystal display device. Specifically, in the viewing angle dependency of the luminance in the left-right direction of a liquid crystal display device including an IPS liquid crystal panel, a viewing angle range having a luminance of 1/3 or more of the front luminance (hereinafter referred to as 1/3 viewing angle). ) Is preferably 120 deg or more.

Furthermore, when the backlight device includes a plurality of line light sources arranged in parallel to each other, luminance unevenness may occur. Specifically, in the display screen, the luminance of the portion corresponding to the position where the line light source is disposed is high, and the luminance of the other portions is low. Such luminance unevenness gives the user viewing the display screen a sense of discomfort. Therefore, it is preferable to suppress luminance unevenness.
Japanese Patent No. 3262230 JP 2006-235014 A

  An object of the present invention is to provide a backlight device that can suppress luminance unevenness and can maintain a wide range of viewing angle dependence of luminance in a predetermined axis direction. Specifically, a backlight device that can suppress luminance unevenness and has a viewing angle dependency of luminance in a predetermined axis direction obtained by laying an IPS liquid crystal panel has a 1/3 viewing angle of 120 degrees or more. Is to provide.

Means for Solving the Problems and Effects of the Invention

  The backlight device according to the present invention includes a surface light source, a lenticular lens sheet, and an optical sheet. The surface light source includes a plurality of line light sources arranged in parallel with each other. The lenticular lens sheet is laid on a surface light source. The lenticular lens sheet includes a plurality of cylindrical lenses and a plurality of flat portions. The plurality of cylindrical lenses are juxtaposed in the direction in which the line light sources are juxtaposed. The flat portion is provided between adjacent cylindrical lenses. The pitch Pc of the plurality of cylindrical lenses, the width Wf of the flat portion, and the height Hc of the cylindrical lens satisfy Expressions (1) and (2).

1/16 ≦ Wf / Pc <1/6 (1)
5/16 ≦ Hc / Pc ≦ 1/2 (2)
The optical sheet is laid on the lenticular lens sheet. The optical sheet improves the luminance uniformity. The optical sheet is, for example, a diffusion sheet or a reflective polarizer.
In the backlight device according to the present invention, the lenticular lens sheet satisfies the expressions (1) and (2), and an optical sheet that improves the luminance uniformity is laid on the lenticular lens sheet. Therefore, it is possible to maintain a wide viewing angle in a predetermined axial direction, specifically, the longitudinal direction of the line light source, and to suppress luminance unevenness.

Preferably, the optical sheet is a diffusion sheet having a haze of 70 to 80%.
In this case, in the viewing angle dependency of the luminance in the longitudinal direction of the line light source, a viewing angle range (1/3 viewing angle) having a luminance of 1/3 or more of the front luminance is 120 degrees or more. Furthermore, the occurrence of uneven brightness can be suppressed.

  Preferably, the transverse shape of the cylindrical lens includes a lens apex and two lens edges. The transverse shape of the cylindrical lens is an elliptic arc in which the end point of the long axis corresponds to the top of the lens. Alternatively, it has an arcuate shape composed of an arc including the top of the lens and two straight lines connecting the end point of the arc and the lens edge.

  If the transverse shape of the cylindrical lens is such a shape, the proportion of the flat portion can be further suppressed while maintaining the viewing angle. Therefore, the occurrence of uneven brightness is further suppressed.

  A liquid crystal display device according to the present invention includes the above-described backlight device and a liquid crystal panel laid on the backlight device. An optical member according to the present invention includes the above-described lenticular lens sheet and the above-described diffusion sheet laid on the lenticular lens sheet.

  The backlight device according to the present invention includes a surface light source, a lenticular lens sheet, and an optical sheet. The surface light source includes a plurality of line light sources arranged in parallel with each other. The lenticular lens sheet is laid on a surface light source. The lenticular lens sheet includes a plurality of cylindrical lenses and a plurality of flat portions. The plurality of cylindrical lenses are juxtaposed in the direction in which the line light sources are juxtaposed. The plurality of flat portions are provided between the adjacent cylindrical lenses. The optical sheet is laid on the lenticular lens sheet to improve the luminance uniformity. In the backlight device according to the present invention, when a liquid crystal panel is laid on the diffusion sheet, the viewing angle range in which the viewing angle range in which the brightness of the front light is 1/3 or more is 120 degrees or more in the longitudinal direction of the line light source is 120 degrees or more. Has dependency.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Display device]
1 and 2, the liquid crystal display device 1 includes a backlight device 10 and a liquid crystal panel 20 laid on the front surface of the backlight device 10. The liquid crystal panel 20 includes a plurality of pixels arranged in a matrix. The display screen 21 of the liquid crystal display device 1 has a rectangular shape having long sides in the left-right direction (x direction in the figure) and short sides in the up-down direction (y direction in the figure).

[Backlight device]
The backlight device 10 is a so-called direct type, and includes a surface light source 11 that emits diffused light and a sheet-like optical member 15 that is laid on the surface light source 11.

  The surface light source 11 includes a housing 12, a plurality of fluorescent tubes 13 that are line light sources, and a light diffusion plate 14. The housing 12 is a housing having an opening 120 on the front surface, and houses a plurality of fluorescent tubes 13 therein. The inner surface of the housing 12 is covered with a reflective film 121. The reflection film 121 irregularly reflects the light emitted from the fluorescent tube 13 and guides the irregularly reflected light to the opening 120. The reflective film 121 is, for example, Toray Lumirror (registered trademark) E60L or E60V, and preferably has a diffuse reflectance of 95% or more.

  The plurality of fluorescent tubes 13 are arranged in parallel in the vertical direction (y direction in FIG. 1) in front of the rear surface of the housing 12. The fluorescent tube 13 is a linear light source extending in the left-right direction (x direction in FIG. 1), and is, for example, a cold cathode tube or an EEFL (External Electrode Fluorescent Lamp: external electrode fluorescent tube). A plurality of point light sources such as LEDs (Light Emitting Device) may be housed in the housing 12 together with the fluorescent tube 13. Moreover, a pseudo line light source may be formed by arranging a plurality of housed LEDs in a line.

  The light diffusing plate 14 is fitted into the opening 120 and is disposed in parallel with the back surface of the housing 12. When the light diffusing plate 14 is fitted into the opening 120, the inside of the housing 12 is sealed. Therefore, the light emitted from the fluorescent tube 13 can be prevented from leaking out of the housing 12 from a place other than the light diffusion plate 14, and the light utilization efficiency is improved.

  The light diffusing plate 14 diffuses the light from the fluorescent tube 13 and the light reflected by the reflection film 121 almost uniformly and emits the light to the front. The light diffusing plate 14 includes a transparent base material and a plurality of particles dispersed in the base material. The particles dispersed in the substrate have a refractive index different from that of the substrate with respect to light having a wavelength in the visible light region. Therefore, the light diffusion plate 14 diffuses the incident light, and the diffused light is transmitted through the light diffusion plate 14. The base material of the light diffusing plate 14 is, for example, glass, polyester resin, polycarbonate resin, polyacrylate resin, alicyclic polyolefin resin, polystyrene resin, polyvinyl chloride resin, polyvinyl acetate resin. It consists of resin such as resin, polyether sulfonic acid resin, triacetyl cellulose resin. The light diffusing plate 14 also supports the optical member 15.

[Optical member]
With reference to FIGS. 3 to 5, the optical member 15 includes a lenticular lens sheet 31 and a diffusion sheet 32.

  The lenticular lens sheet 31 has a sheet shape or a film shape, and is laid on the light diffusion plate 14. At this time, the flat surface 314 of the lenticular lens sheet 31 faces the light diffusion plate 14.

  The lenticular lens sheet 31 includes a base part 310 and a cylindrical lens part 311. The base material part 310 is transparent to visible light. The base material portion 310 is made of, for example, a resin such as glass, a polyester resin, a polycarbonate resin, a polyacrylate resin, an alicyclic polyolefin resin, a polystyrene resin, or a triacetyl cellulose resin.

  The cylindrical lens portion 311 is formed on the base material portion 310. The cylindrical lens portion 311 is transparent to visible light. The cylindrical lens part 311 includes a plurality of cylindrical lenses 312 and a flat part 313. The plurality of cylindrical lenses 312 are juxtaposed in the same direction as the juxtaposition direction of the plurality of fluorescent tubes 13 that are line light sources. That is, the plurality of cylindrical lenses 312 are juxtaposed in the vertical direction (y direction in FIG. 1). The transverse shape of the surface (lens surface) 315 of the cylindrical lens 312 is an arc, an elliptical arc, or an arcuate shape. The flat portion 313 is formed between adjacent cylindrical lenses 312.

  The cylindrical lens portion 311 is made of an ionizing radiation curable resin. The ionizing radiation curable resin is cured by ionizing radiation such as ultraviolet rays and electron beams. Examples of ionizing radiation curable resins include polyester acrylate resins, urethane acrylate resins, polyether acrylate resins, epoxy acrylate resins, polyester methacrylate resins, urethane methacrylate resins, polyether methacrylate resins, and epoxy methacrylate resins. is there.

  The diffusion sheet 32 is an optical sheet that improves the luminance uniformity. The diffusion sheet 32 is laid on the lenticular lens sheet 31. The diffusion sheet 32 includes a base part 320 and a lens part 321. The base material part 320 is made of the same material as the base material part 310 of the lenticular lens sheet 31.

  The lens part 321 has a plurality of convex parts 323. The lens unit 321 includes spherical particles and a binder. The spherical particles are made of glass, resin or the like and are randomly dispersed in the binder. Part of the spherical particles in the binder is exposed from the binder surface, and a plurality of convex portions 323 are formed on the surface of the lens portion 321. The plurality of convex portions 323 collect the light incident from the lower surface 322 in the front (normal direction of the lower surface 322). The binder is made of an ionizing radiation curable resin that is cured by ionizing radiation. The liquid crystal panel 20 is laid on the diffusion sheet 32.

In the optical member 15, the pitch Pc (μm) between the adjacent cylindrical lenses 312, the width Wf (μm) of the flat portion 313, and the height Hc of the cylindrical lens 312 are expressed by Equations (1) and (2). Satisfied.
1/16 ≦ Wf / Pc <1/6 (1)
5/16 ≦ Hc / Pc ≦ 1/2 (2)
Here, the pitch Pc is the distance between the tops Tc of the adjacent cylindrical lenses 312 as shown in FIG.

Furthermore, the haze (%) of the diffusion sheet 32 satisfies the formula (3).
70 ≦ haze ≦ 80 (3)
The optical member 15 can maintain a wide viewing angle in the left-right direction (hereinafter referred to as a left-right viewing angle) by satisfying the expressions (1) to (3). Specifically, when an IPS-type liquid crystal panel is laid, the viewing angle (hereinafter referred to as the following) is a luminance of 1/3 or more of the front luminance in the viewing angle dependency of the luminance in the left-right direction (x direction in FIG. 1). 1/3 left-right viewing angle) is 120 deg or more. More specifically, the 1/3 viewing angle in the viewing angle dependency of the luminance in the right direction from the front normal (viewing angle 0 deg) is 60 deg or more, and the viewing angle dependency in the luminance in the left direction from the normal is The 1/3 viewing angle is 60 degrees or more.
Furthermore, the occurrence of luminance unevenness is suppressed by satisfying the expressions (1) to (3). Details of the formulas (1) to (3) will be described below.

[Regarding Formula (1)]
If Wf / Pc is too small, the 1/3 left-right viewing angle is less than 120 deg. If Wf / Pc is too small, the ratio of the flat portion 313 in the lenticular lens sheet 31 will be too small. Therefore, in the optical member 15, it is estimated that the light collecting function in the left-right direction becomes excessively high, and as a result, the left-right viewing angle is narrowed. If Wf / Pc is 1/16 or more, the 1/3 left-right viewing angle is 120 deg or more.

  On the other hand, if Wf / Pc is too large, luminance unevenness occurs. If Wf / Pc is too large, the ratio of the flat portion 313 in the lenticular lens sheet 31 becomes too large. The flat part 313 does not contribute to light collection. Therefore, when a light beam emitted from the line light source in the front direction of the liquid crystal panel enters the flat portion 313, the light is emitted as it is without being deflected. Therefore, on the display screen of the liquid crystal panel, the luminance corresponding to the line light source is increased, and the luminance of other portions is decreased. For the above reason, it is estimated that luminance unevenness occurs. If Wf / Pc is less than 1/6, since the ratio of the flat portion 313 in the lenticular lens sheet 31 is small, the occurrence of uneven brightness can be suppressed. Preferably, 1/16 ≦ Wf / Pc ≦ 1/8.

[Regarding Formula (2)]
Hc / Pc also affects the left / right viewing angle and luminance unevenness. When Expression (2) is satisfied, the occurrence of luminance unevenness can be suppressed, and the 1/3 left-right viewing angle is 120 degrees or more. The reason for this is not clear, but the following reason is presumed.

  If Hc / Pc is small, the height Hc of the cylindrical lens 312 is small with respect to the pitch Pc. Therefore, the curvature of the surface 315 of the cylindrical lens 312 becomes small. If the curvature of the surface 315 is small, the light incident from the line light source 13 is difficult to be deflected. Therefore, it is estimated that luminance unevenness is likely to occur.

  On the other hand, if Hc / Pc is large, the curvature of the surface 315 of the cylindrical lens 312 becomes large. Therefore, the light incident from the line light source 13 is largely deflected. As a result, the width of the viewing angle dependency of luminance is narrowed, and it is estimated that the 1/3 left-right viewing angle is less than 120 deg.

[Regarding Formula (3)]
Haze is also called haze and indicates the degree to which incident light diffuses. The haze is measured by a haze measuring method based on JIS K7136. If the expressions (1) and (2) are satisfied and the haze of the diffusion sheet 32 satisfies the expression (3), the occurrence of luminance unevenness can be suppressed, and the 1/3 left-right viewing angle becomes 120 degrees or more. The reason is estimated as follows. If the haze is too small, the degree of light diffusion is small and the transparency is high. Therefore, it is estimated that luminance unevenness is likely to occur. On the other hand, if the haze is too large, the degree of light diffusion is large. For this reason, it is presumed that the width of the viewing angle dependency of luminance becomes narrow.

For the above reasons, if the expressions (1) to (3) are satisfied, the 1/3 left-right viewing angle becomes 120 degrees or more, and the occurrence of luminance unevenness is suppressed.
In addition, it can replace with the diffusion sheet 32 which satisfy | fills Formula (3), and can also obtain the effect similar to the above-mentioned even if it uses a reflective polarizer. The reflective polarizer improves the luminance uniformity like the diffusion sheet. The reflective polarizer is, for example, DBEF (Dual Brightness Enhancement Film) manufactured by Sumitomo 3M.

  In general, the display screen 21 of the liquid crystal display device 1 has a rectangular shape that is long in the left-right direction. The fluorescent tubes 13 are arranged in the short side direction of the display screen 21. In this case, the optical member 15 has the same rectangular shape as the display screen 21. In other words, the lenticular lens sheet 31 and the diffusion sheet 32 have a rectangular shape with the same size as each other, and the cylindrical lens 312 is arranged in parallel in the short side direction. Thereby, the viewing angle in the long side direction (left-right direction) becomes wide, and by satisfying the expressions (1) to (3), the 1/3 left-right viewing angle becomes 120 degrees or more.

  Note that the rectangular shape here does not have to be a strict rectangle, but may be a rectangular shape having a long side and a short side. When the display screen is not rectangular, the lenticular lens sheet 31 and the diffusion sheet 32 do not have to be rectangular, and may have any shape corresponding to the display screen.

  The transverse shape of the surface 315 of the cylindrical lens 312 is an arc or an elliptical arc shown. The transverse shape may be an arcuate shape.

  Preferably, the transverse shape of the surface 315 of the cylindrical lens 312 is an elliptical arc whose end point of the major axis LA is the apex Tc, as shown in FIG. Or, preferably, the transverse shape of the cylindrical lens 312 is configured by an arc 316 including the top Tc and a line segment 317 connecting the end point CP of the arc and the edge EL of the cylindrical lens 312 as shown in FIG. An arcuate shape is preferred. The arc 316 may be a circular arc or an elliptical arc. Further, the line segment 317 may be a tangent line at the end point CP.

  If the cross-sectional shape of the surface 315 of the cylindrical lens 312 is the shape shown in FIG. 6 or FIG. 7, the ratio of the flat portion can be suppressed, and the width of the luminance angle characteristic in the left-right direction becomes excessively narrow. Can be prevented. Even in the case of these shapes, the expressions (1) to (3) need to be satisfied.

  Furthermore, an angle θc (hereinafter referred to as a contact angle) θc formed by a surface (lens plane) ES including the lens edge EL of the cylindrical lens 312 and the surface 315 is preferably 60 degrees or more and less than 90 degrees. If Expression (2) is satisfied, θc is often not less than 60 degrees and less than 90 degrees. When the contact angle θc is less than 60 deg, the light condensing function is low, so that uneven brightness tends to occur. Further, when the contact angle θc is 90 degrees or more, the portion near the lens edge of the surface 315 does not contribute to the light collection. Furthermore, it becomes difficult to manufacture a lenticular lens sheet by the roll plate. A more preferable contact angle θc is not less than 60 deg and not more than 75 deg.

  The transmittance of the light diffusing plate 14 is preferably 50 to 70%, and more preferably 60 to 70%. More preferably, it is 60 to 65%.

[Production method]
The lenticular lens sheet 31 is manufactured by a known manufacturing method. An example of a process for manufacturing the lenticular lens sheet 31 is as follows. A roll plate having an outer peripheral surface in which a plurality of grooves corresponding to the plurality of cylindrical lenses 312 are arranged in the axial direction is prepared. An ionizing radiation curable resin is applied onto the roll plate by a die coater. After the application, the cylindrical lens portion 311 is transferred onto the substrate portion 310 by irradiating ionizing radiation while pressing the substrate sheet to be the substrate portion 310 against the roll plate. The lenticular lens sheet 31 can be manufactured through the above steps.

  In the above-described manufacturing method, the ionizing radiation curable resin is applied on the roll plate. However, the ionizing radiation curable resin layer may be formed by applying the ionizing radiation curable resin on the base member 310. In this case, the ionizing radiation curable resin layer is pressed against the roll plate. Moreover, you may apply | coat ionizing radiation hardening resin to the surface of a roll plate, and the surface of the base-material part 310, respectively. Moreover, in the above-described manufacturing method, a roll plate is used, but a plate-like lithographic plate may be used.

  The diffusion sheet 32 can also be manufactured by a known manufacturing method. An example of a process for manufacturing the diffusion sheet 32 is as follows. First, a plurality of types of spherical particles having different particle diameters are uniformly dispersed in an ionizing radiation curable resin as a binder. Subsequently, the ionizing radiation curable resin in which the spherical particles are dispersed is applied onto the base material sheet to be the base material portion 320 using a gravure coater. At this time, the particle concentration and the coating thickness are adjusted so that a part of the plurality of spherical particles is exposed from the coating film of the ionizing radiation curable resin. After the application, ionizing radiation is irradiated to cure the ionizing radiation curable resin to obtain a diffusion sheet 32.

The diffusion sheet 32 can be manufactured by a method different from the above method. For example, a paint in which an organic solvent-soluble resin is dissolved in an organic solvent is prepared. Disperse the glass particles in the prepared paint. A paint in which glass particles are dispersed is applied on a base sheet. After application, the organic solvent is dried to form a diffusion sheet 32.
A reflective polarizer is also manufactured by a known manufacturing method.

  Optical members having various shapes and haze and light diffusing plates having various transmittances were prepared. Backlight devices with test numbers 1 to 10 were manufactured using the prepared optical member and light diffusion plate. The viewing angle dependence and luminance unevenness of each manufactured backlight device were investigated.

表１中の「レンズ横断形状」は、各試験番号のレンチキュラレンズシートを構成するシリンドリカルレンズの表面の横断形状を示す。表中の「楕円」は、シリンドリカルレンズ表面の横断形状が、長軸の端点をレンズ頂上とする楕円弧であることを示す。また、表中の「弓状」は、シリンドリカルレンズ表面の横断形状が、頂上を含む円弧と、円弧の端点とシリンドリカルレンズのエッジとを結ぶ接線とで構成された弓状であることを示す。より具体的には、各試験番号のシリンドリカルレンズ形状は以下のとおりであった。試験番号１、３、４、６及び７のシリンドリカルレンズ表面の横断形状は、長径が１００μｍ、短径が５８．８μｍの楕円弧であった。試験番号２のシリンドリカルレンズ表面の横断形状のうち、頂上を含む円弧の半径（以下、弓状円弧半径という）は、１９．２μｍであった。試験番号５の弓状円弧半径は２１．１μｍであった。試験番号８の弓状円弧半径は２５μｍであった。試験番号９の弓状円弧半径は１７．３μｍであった。 The backlight devices of test numbers 1 to 9 were manufactured by the following methods, respectively.
First, the lenticular lens sheet which comprises an optical member was manufactured with the following method. A roll plate having a plurality of grooves corresponding to the shape of the cylindrical lens was prepared, and an ultraviolet curable resin was applied on the prepared roll plate. Subsequently, the roll plate was pressed against a polyethylene terephthalate (PET) film serving as a base material portion. At this time, the ultraviolet curable resin was cured by irradiating ultraviolet rays to obtain a lenticular lens sheet. The cross-sectional shape of the cylindrical lens surface of the manufactured lenticular lens sheet, the contact angle θc (deg), the pitch Pc (μm), the flat portion width Wf (μm), and the cylindrical lens height Hc (μm) are shown. It is shown in 1.

The “lens transverse shape” in Table 1 represents the transverse shape of the surface of the cylindrical lens constituting the lenticular lens sheet of each test number. “Ellipse” in the table indicates that the transverse shape of the surface of the cylindrical lens is an elliptical arc with the end point of the long axis at the top of the lens. In addition, “bow shape” in the table indicates that the transverse shape of the surface of the cylindrical lens is an arc shape formed by an arc including the apex and a tangent line connecting the end point of the arc and the edge of the cylindrical lens. More specifically, the cylindrical lens shape of each test number was as follows. The transverse shape of the cylindrical lens surfaces of Test Nos. 1, 3, 4, 6 and 7 was an elliptical arc having a major axis of 100 μm and a minor axis of 58.8 μm. Of the transverse shape of the cylindrical lens surface of Test No. 2, the radius of the arc including the top (hereinafter referred to as the arcuate arc radius) was 19.2 μm. The arcuate arc radius of Test No. 5 was 21.1 μm. The arcuate arc radius of Test No. 8 was 25 μm. The arcuate arc radius of Test No. 9 was 17.3 μm.

  Next, the diffusion sheet which comprises an optical member was manufactured with the following method. A paint was prepared in which a plurality of types of acrylic particles having different particle sizes were dispersed in an ultraviolet curable resin. Moreover, the PET film used as a base material part was prepared. The coating material was apply | coated on PET film using the gravure coater. The coating material applied by irradiating ultraviolet rays was cured to produce a diffusion sheet. In the manufactured diffusion sheet, some of the plurality of acrylic particles were exposed from the surface, and irregularities were formed on the surface. Table 1 shows the haze (%) of the produced diffusion sheet. In addition, haze was measured by the haze measuring method based on JISK7136.

The surface light source was manufactured as follows. A housing containing 16 EEFLs was prepared. The EEFLs were arranged in the vertical direction (y direction in FIG. 1). A light diffusing plate having transmittance was fitted into the opening of the housing. Table 1 shows the transmittance (%) of the light diffusion plate. The transmittance was measured with a spectrophotometer.
The manufactured lenticular lens sheet was laid on the surface light source, and the manufactured diffusion sheet was further laid on the lenticular lens sheet to manufacture backlight devices with test numbers 1 to 9. At this time, the parallel direction of the cylindrical lenses was set to the same vertical direction as the parallel direction of the EEFL.

  Further, a backlight device of test number 10 was manufactured. The backlight device of test number 10 used a prism sheet instead of the lenticular lens sheet used in the backlights of test numbers 1-9.

The transverse shape of each prism of the prism sheet was an isosceles triangle having an apex angle of 90 deg, and the distance between apexes (that is, the pitch) of adjacent prisms was 50 μm. The prism sheet was manufactured using a roll plate in the same manner as in test numbers 1 to 9.
Moreover, the diffusion sheet was manufactured by the method similar to the test numbers 1-9. The haze of the produced diffusion sheet was 65.0% as shown in Table 1.
As the surface light source, a light diffusing plate having a transmittance of 65% was used. The configuration of the other surface light sources was the same as the surface light sources of Test Nos. 1-9.

  A prism sheet was laid on the surface light source. At this time, the prism sheet was laid so that the flat surface opposite to the surface on which the plurality of prisms were formed (hereinafter referred to as the prism surface) of the surface of the prism sheet was opposed to the front surface of the surface light source. In addition, the parallel direction of the prisms was the same as the parallel direction of the EEFL. Further, a diffusion sheet was laid on the prism surface of the prism sheet to manufacture a backlight device.

[Investigation method]
About the manufactured backlight apparatus of the test numbers 1-10, front brightness ratio, 1/3 right-and-left viewing angle, and brightness nonuniformity were investigated by the method shown next.

[Front luminance ratio, 1/3 left / right viewing angle]
An IPS liquid crystal panel having a 32-inch display screen was laid on each backlight device to obtain a liquid crystal display device.

  The viewing angle dependence of the luminance in the vertical and horizontal directions of each liquid crystal display device was measured. The viewing angle is defined by taking the normal direction (front) of the display screen as the 0 degree axis, the tilt angle from the 0 degree axis in the vertical direction as the vertical viewing angle, and the tilt angle from the 0 degree axis in the horizontal direction as the left and right viewing angle. . Of the left and right viewing angles, the inclination angle (viewing angle) from the normal to the right is indicated by plus (+), and the inclination angle (viewing angle) from the normal to the left is indicated by minus (−). Similarly, of the vertical viewing angles, the inclination angle (viewing angle) upward from the normal line is indicated by plus (+), and the inclination angle (viewing angle) downward from the normal line is indicated by minus (−). It was. The luminance at each vertical viewing angle and left and right viewing angle was measured with a luminance meter. The luminance measurement point was the center of the display screen.

  After measuring the viewing angle dependence of the luminance in the vertical direction and the horizontal direction, the front luminance ratio was determined by the following method. First, for each test number, a liquid crystal display device composed of a surface light source and an IPS liquid crystal panel was produced. That is, a liquid crystal display device from which the optical member was removed was produced. Hereinafter, this liquid crystal display device is referred to as a reference liquid crystal display device. Subsequently, the front luminance of the reference liquid crystal display device (hereinafter referred to as reference front luminance) was obtained. At this time, the average of the luminance at the viewing angle 0 deg in the horizontal viewing angle dependency and the luminance at the viewing angle 0 deg in the vertical viewing angle dependency was defined as the reference front luminance.

  The ratio of the front luminance of each liquid crystal display device (liquid crystal display device including an optical member) to the determined reference front luminance was defined as the front luminance ratio. Here, the front luminance of each liquid crystal display device was the average of the luminance of the viewing angle 0 deg in the vertical viewing angle dependency and the luminance of the viewing angle 0 deg in the horizontal viewing angle dependency.

  Further, the 1/3 left-right viewing angle was obtained by the following method. First, as shown in FIGS. 8 to 17, graphs of viewing angle dependency of luminance of each test number were prepared. FIG. 8 shows the viewing angle dependence of the luminance of test number 1. Similarly, FIGS. 9 to 17 show the viewing angle dependence of the luminance of Test No. 2 to Test No. 10, respectively. The horizontal axis of each figure is the viewing angle. The vertical axis represents the luminance ratio (relative luminance) at each viewing angle. The luminance ratio at each viewing angle is the ratio of the luminance at each viewing angle to the reference frontal luminance described above. In the figure, the solid line is a curve of the viewing angle dependency of the luminance in the left-right direction, and the broken line is a curve of the viewing angle dependency of the luminance in the vertical direction.

  Of the viewing angle dependence of the luminance in the left and right directions shown in FIGS. The viewing angle was used. Similarly, the viewing angle range having a luminance ratio of 1/3 of the front luminance ratio among the viewing angle dependence of the luminance in the vertical direction is defined as 1/3 vertical viewing angle.

[Brightness unevenness]
The luminance unevenness was evaluated by the following method. Using the liquid crystal display devices of test numbers 1 to 10 described above, it was visually determined whether or not luminance unevenness occurred on the display screen.

[Investigation result]
The survey results are shown in Table 1. “◯” in “Luminance unevenness” in Table 1 indicates that no luminance unevenness occurred. “X” indicates that luminance unevenness occurred. Further, “± 62.2” in the 1/3 left-right viewing angle in Table 1 is the range where the 1/3 left-right viewing angle is −62.2 deg to +62.2 deg. The viewing angle is 124.4 deg. The same applies to the numerical value of the 1/3 vertical viewing angle.

  Referring to Table 1, the front luminance ratios of Test No. 1 to Test No. 10 were all greater than 1. That is, the front luminance was improved by using the optical member.

  The backlight devices with test numbers 1 to 3 satisfied all of the expressions (1) to (3). Therefore, the 1/3 left-right viewing angle was 120 degrees or more. Further, luminance unevenness did not occur.

  On the other hand, in the backlight device of test number 4, Wf / Pc did not satisfy Formula (1) and was less than the lower limit value. Therefore, the 1/3 left-right viewing angle was less than 120 deg. In the backlight device of test number 5, Wf / Pc did not satisfy the formula (1) and exceeded the upper limit value. As a result, luminance unevenness occurred.

  In the backlight device of test number 6, the haze of the diffusion sheet did not satisfy the formula (3) and exceeded 80%. Therefore, the 1/3 left-right viewing angle was less than 120 deg. In the backlight device of test number 7, the haze of the diffusion sheet did not satisfy the formula (3) and was less than 70%. As a result, luminance unevenness occurred.

In the backlight device of test number 8, Hc / Pc did not satisfy the formula (2) and was less than the lower limit. As a result, luminance unevenness occurred. In the backlight device of test number 9, Hc / Pc did not satisfy the formula (2) and exceeded the upper limit value. Therefore, the 1/3 left-right viewing angle was less than 120 deg. In the backlight device of Test No. 10, since a prism sheet was laid instead of the lenticular lens sheet, the 1/3 left-right viewing angle was less than 120 deg.
The 1/3 vertical viewing angle was 80 deg (−40 deg to +40 deg) or more for all test numbers.

  While the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately modifying the above-described embodiment without departing from the spirit thereof.

1 is a perspective view of a liquid crystal display device according to an embodiment of the present invention. It is sectional drawing in line segment II-II of the backlight apparatus in FIG. It is a perspective view of the optical member in FIG. It is sectional drawing in line segment IV-IV in FIG. FIG. 5 is a cross-sectional view taken along line VV in FIG. 3. It is a cross-sectional view of another lenticular lens sheet different from the shape shown in FIG. FIG. 7 is a cross-sectional view of another lenticular lens sheet different from the shape shown in FIGS. 4 and 6. It is a figure which shows the luminance angle characteristic of the backlight apparatus of the test number 1 in an Example. It is a figure which shows the luminance angle characteristic of the backlight apparatus of the test number 2 in an Example. It is a figure which shows the luminance angle characteristic of the backlight apparatus of the test number 3 in an Example. It is a figure which shows the luminance angle characteristic of the backlight apparatus of the test number 4 in an Example. It is a figure which shows the luminance angle characteristic of the backlight apparatus of the test number 5 in an Example. It is a figure which shows the luminance angle characteristic of the backlight apparatus of the test number 6 in an Example. It is a figure which shows the luminance angle characteristic of the backlight apparatus of the test number 7 in an Example. It is a figure which shows the luminance angle characteristic of the backlight apparatus of the test number 8 in an Example. It is a figure which shows the luminance angle characteristic of the backlight apparatus of the test number 9 in an Example. It is a figure which shows the luminance angle characteristic of the backlight apparatus of the test number 10 in an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 10 Backlight apparatus 11 Surface light source 14 Light diffusing plate 15 Optical member 20 Liquid crystal panel 21 Display screen 31 Lenticular lens sheet 32 Diffusion sheet 312 Cylindrical lens 313 Flat part

Claims (10)

A surface light source including a plurality of line light sources arranged in parallel with each other;
A plurality of cylindrical lenses laid on the surface light source and arranged in parallel with the line light source; and a plurality of flat portions provided between adjacent cylindrical lenses, the plurality of cylindrical lenses A lenticular lens sheet in which the pitch Pc, the width Wf of the flat portion, and the height Hc of the cylindrical lens satisfy the expressions (1) and (2),
A backlight device comprising: an optical sheet that is laid on the lenticular lens sheet to improve luminance uniformity.
1/16 ≦ Wf / Pc <1/6 (1)
5/16 ≦ Hc / Pc ≦ 1/2 (2) The backlight device according to claim 1,
The backlight device, wherein the optical sheet is a diffusion sheet having a haze of 70 to 80%. The backlight device according to claim 1 or 2,
The cylindrical lens transverse shape includes a lens top and two lens edges,
The cylindrical lens has a transverse shape with an elliptical arc whose long axis end point corresponds to the top of the lens, or an arc having an arc including the top of the lens and two straight lines connecting the end point of the arc and the lens edge. There is a backlight device. A surface light source including a plurality of line light sources arranged in parallel with each other;
A lenticular lens sheet comprising a plurality of cylindrical lenses laid on the surface light source and arranged in parallel in the line light source, and a plurality of flat portions each provided between adjacent cylindrical lenses;
An optical sheet laid on the lenticular lens sheet to improve the brightness uniformity;
When the liquid crystal panel is laid on the optical sheet, the viewing angle dependence of the luminance is such that the viewing angle range in which the luminance of the front light source is 1/3 or more is 120 degrees or more in the longitudinal direction of the line light source. Backlight device characterized. The backlight device according to any one of claims 1 to 4,
A liquid crystal display device comprising: a liquid crystal panel laid on the backlight device. An optical member laid on a surface light source including a plurality of line light sources arranged side by side,
The plurality of cylindrical lenses including a plurality of cylindrical lenses laid on the surface light source and arranged in parallel with the line light source, and a plurality of flat portions each provided between adjacent cylindrical lenses. A lenticular lens sheet in which the pitch Pc, the width Wf of the flat portion, and the height Hc of the cylindrical lens satisfy the expressions (1) and (2),
An optical member, comprising: an optical sheet that is laid on the lenticular lens sheet and improves brightness uniformity.
1/16 ≦ Wf / Pc <1/6 (1)
5/16 ≦ Hc / Pc ≦ 1/2 (2) The optical member according to claim 6,
The optical member is a diffusion sheet having a haze of 70 to 80%. The optical member according to claim 6 or 7,
The cylindrical lens transverse shape includes a lens top and two lens edges,
The cylindrical lens has a transverse shape with an elliptical arc whose long axis end point corresponds to the top of the lens, or an arc having an arc including the top of the lens and two straight lines connecting the end point of the arc and the lens edge. There is an optical member. A back provided with a surface light source including a plurality of line light sources arranged in parallel to each other, a lenticular lens sheet laid on the surface light source, and an optical sheet laid on the lenticular lens sheet and improving luminance uniformity The lenticular lens sheet used in a light device,
A plurality of cylindrical lenses arranged in parallel in the direction in which the linear light sources are arranged;
Each including a plurality of flat portions provided between adjacent cylindrical lenses;
The lenticular lens sheet, wherein the pitch Pc of the plurality of cylindrical lenses, the width Wf of the flat portion, and the height Hc of the cylindrical lens satisfy the expressions (1) and (2).
1/16 ≦ Wf / Pc <1/6 (1)
5/16 ≦ Hc / Pc ≦ 1/2 (2) The lenticular lens sheet according to claim 9, wherein
The cylindrical lens transverse shape includes a lens top and two lens edges,
The cylindrical lens has a transverse shape having an arcuate arc whose long axis end point corresponds to the top of the lens or an arc including the top of the lens and two straight lines connecting the end point of the arc and the lens edge. A lenticular lens sheet characterized by

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