JP2008066287A - Backlight device, display device, and optical member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight device having high front face luminance and a luminance angle distribution in the two-axis direction spreading to some extent. <P>SOLUTION: The backlight device has a plane light source, a microlens array sheet 51, and a lenticular lens sheet 52. The microlens array sheet 51 has a flat surface facing the plane light source and a microlens surface located on the opposite side of the flat surface and on which a plurality of microlenses are formed. The lenticular lens sheet 52 has a flat surface facing the microlens surface and a cylindrical lens surface located on the opposite side of the flat surface and on which a plurality of cylindrical lenses are formed side by side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a backlight device, a display device, and an optical member, and more specifically, a backlight device used in a display device represented by a liquid crystal display, a display device including the backlight device, and an optical device used in the backlight device. It relates to members.

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

  In recent years, further improvements in front luminance have been demanded, and backlight devices having various optical members have been presented. Japanese Patent Application Laid-Open Publication No. 2004-311263 (Patent Document 2) discloses an optical member for a backlight device including a microlens array sheet 100 and a prism sheet 200 as shown in FIG. Hereinafter, this optical member is referred to as a preceding optical member 300. In Patent Document 2, a higher light collection effect is obtained by superimposing the prism sheet 200 on the microlens array sheet 100. As a result, the front luminance can be significantly improved.

  However, as a result of the investigation by the inventors of the present application, it has been found that the preceding optical member 300 has the following three problems.

  First, in the preceding optical member 300, a narrow luminance angle distribution is generated. When the preceding optical member 300 is laid such that the parallel arrangement direction of the plurality of prisms 201 on the prism sheet is the vertical direction of the display screen of the display device, the width of the luminance angle distribution in the vertical direction becomes very narrow. That is, the viewing angle in the vertical direction (hereinafter referred to as the vertical viewing angle) is narrowed. FIG. 15 is a luminance angle distribution in the vertical direction and the horizontal direction of the preceding optical member 300 obtained by the inventors of the present application. The horizontal axis in the figure indicates the viewing angle. As for the viewing angle, the normal direction of the optical member (that is, the front) is 0 deg. For the vertical direction, the tilt angle from 0 deg to the upward direction is plus (+), and the tilt angle to the downward direction is minus (−). It was. Similarly, in the left-right direction, the inclination angle from 0 deg to the right direction is plus (+), and the inclination angle to the left direction is (-). The vertical axis in the figure indicates the luminance. The luminance here refers to relative luminance (unit: a) based on the front luminance (luminance at a viewing angle of 0 deg) of the backlight device in which only the diffusion plate is laid in the opening without laying the optical member. .U.).

  Referring to FIG. 15, the front luminance of the display screen, that is, the luminance at a viewing angle of 0 deg is about 2.3 a. u. It is higher than the front luminance (1.55 a.u.) of one prism sheet. However, the width of the luminance angle distribution in the vertical direction (solid line in the figure) becomes narrow. Specifically, a viewing angle range in which the luminance is 1/2 or more of the front luminance (hereinafter referred to as a 1/2 viewing angle range) is narrower than a range of ± 35 deg and is in a range of −30 to +30 deg. It is preferable that the luminance angle distribution in the vertical direction and the horizontal direction have a certain width. This is because the user of the display device may view the display screen from the top-bottom diagonal direction or the left-right diagonal direction. Therefore, it is preferable that the luminance angle distribution in any of the biaxial directions (vertical direction and horizontal direction) has a certain extent. Specifically, in the luminance angle distribution in the biaxial direction, it is preferable that the ½ viewing angle range is larger than the range of ± 35 deg.

  Second, the horizontal luminance angle distribution (dotted line in the figure) obtained by the preceding optical member 300 is not a natural distribution in which the luminance gradually decreases with the spread of the viewing angle with the front luminance as a peak. When the angle is larger than P1 (about −50 deg) and P2 (about +50 deg), the luminance is extremely lowered. Such an extreme change in the inclination of the luminance angle distribution gives the user viewing the display screen a feeling of strangeness.

Third, the vertical luminance obtained with the preceding optical member 300 gradually decreases as the viewing angle increases, but increases again when it exceeds ± 50 deg. That is, the luminance angle distribution in the vertical direction has side lobes S1 and S2. Such side lobes S1 and S2 also give an uncomfortable feeling to the user viewing the display screen.
Japanese Patent No. 3262230 JP 2004-312663 A

  An object of the present invention is to provide a backlight device having high front luminance and having a certain extent of luminance angle distribution in the biaxial direction. More specifically, the front luminance is higher than the front luminance of the backlight device with one prism sheet, and in each of the luminance angle distributions in the biaxial direction, the ½ viewing angle range is more than ± 35 deg. Is to provide a large backlight device.

  Another object of the present invention is to provide a backlight device in which the luminance angle distribution is a natural orientation distribution. More specifically, an object of the present invention is to provide a backlight device that can suppress an extreme change in the slope of a luminance angle distribution curve and can suppress the occurrence of side lobes.

Means for Solving the Problems and Effects of the Invention

  The backlight device according to the present invention includes a surface light source, a microlens array sheet, and a lenticular lens sheet. The microlens array sheet has a flat surface facing the surface light source, and a microlens surface opposite to the flat surface on which a plurality of microlenses are formed. The lenticular lens sheet has a flat surface facing the micro lens surface, and a cylindrical lens surface on which a plurality of cylindrical lenses are arranged in parallel to each other on the opposite side of the flat surface.

  In the backlight device according to the present invention, a lenticular lens sheet is laid on a microlens array sheet. Since the light condensed by the micro lens array is further condensed by the lenticular lens sheet, the front luminance is higher than the front luminance of the backlight device with one prism sheet. Furthermore, when a lenticular lens sheet is laid on the microlens array sheet, it is possible to suppress an extremely narrow luminance angle distribution in the direction in which the cylindrical lenses are arranged side by side. Therefore, the luminance angle distribution in the biaxial direction (longitudinal direction and parallel direction of the cylindrical lenses) has a 1/2 viewing angle range larger than the range of ± 35 deg. Preferably, one of the biaxial directions has a 1/2 viewing angle range larger than a range of ± 50 deg. Furthermore, side lobes can be reduced and extreme changes in the slope of the luminance angle distribution can be suppressed.

  Preferably, the microlens array sheet and the lenticular lens sheet are rectangular, and the plurality of cylindrical lenses are arranged in parallel in the short side direction of the lenticular lens sheet.

  In this case, the condensing effect in the direction in which the cylindrical lenses are arranged side by side is larger than the condensing effect in the longitudinal direction. Therefore, the luminance angle distribution in the long side direction is wider than the luminance angle distribution in the short side direction.

  Usually, the display screen of a display device is a rectangle long in the horizontal direction (left-right direction). Therefore, when the backlight according to the present invention is applied to such a display device, the luminance angle distribution in the left-right direction can be made wider than the luminance angle distribution in the vertical direction.

  A display device according to the present invention includes a surface light source, a microlens array sheet, a lenticular lens sheet, and a display panel. The display panel is laid on the cylindrical lens surface of the lenticular lens sheet and has a plurality of pixels arranged in a matrix.

Preferably, the arrangement pitch Pc of the plurality of cylindrical lenses and the arrangement pitch Pp of the pixels arranged in the same direction as the parallel arrangement direction of the cylindrical lenses among the plurality of pixels satisfy Expression (1).
Pc ≦ Pp / 5 (1)

  In this case, it is possible to suppress the occurrence of moire fringes between the pixels of the display panel and the backlight device.

  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. In the luminance angle distribution diagram, the solid curve indicates the luminance angle distribution in the vertical direction, and the dotted curve indicates the luminance angle distribution in the horizontal direction.

[Display device]
Referring to FIGS. 1 and 2, the 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 of the display device 1 has a rectangular shape having long sides in the left-right direction (x direction in the drawing) and short sides in the up-down direction (y direction in the drawing).

[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 cold cathode tubes 13, and a light diffusion plate 14. The housing 12 is a housing having an opening 120 on the front, and houses the cold cathode tube 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 cold cathode 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 cold cathode 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 cold cathode tube 13 is a linear light source extending in the left-right direction (the x direction in FIG. 1), for example, a fluorescent tube. Instead of the cold cathode tube 13, a plurality of point light sources such as LEDs (Light Emitting Device) may be housed in the housing 12. Moreover, a line light source and a point light source may be accommodated.

  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, it is possible to prevent light emitted from the cold cathode tube 13 from leaking outside the light diffusion plate 14 to the outside of the housing 12 and to improve light utilization efficiency.

  The light diffusing plate 14 diffuses the light from the cold cathode tube 13 and the light reflected by the reflection film 121 substantially 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 diffusion 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]
3 to 5, the optical member 15 includes a microlens array sheet 51 and a lenticular lens sheet 52 laid on the microlens array sheet 51.

  The microlens array sheet 51 is in the form of a sheet or film and has two surfaces (a flat surface 511 and a microlens surface 512). The plane 511 faces the surface light source 11. A plurality of microlenses 513 arranged in a two-dimensional manner are formed on the microlens surface 512 opposite to the plane 511. Each microlens 513 is a so-called plano-convex lens.

  The microlens array sheet 51 includes a base material unit 500 and a lens unit 501 that is formed on the base material unit 500 and includes a plurality of microlenses 513. The sheet-like base material portion 500 is transparent to visible light, and includes, for example, glass, polyester resin, polycarbonate resin, polyacrylate resin, alicyclic polyolefin resin, polystyrene resin, polychlorinated resin. It consists of resin such as vinyl resin, polyvinyl acetate resin, polyether sulfonic acid resin, and triacetyl cellulose resin. The lens unit 501 is also transparent to visible light and is made of an ultraviolet curable resin that is cured by ultraviolet rays. You may use resin hardened | cured by ionizing radiation other than an ultraviolet-ray.

  The lenticular lens sheet 52 has a sheet shape or a film shape and has two surfaces (a flat surface 521 and a cylindrical lens surface 522). The plane 521 is opposed to the microlens surface 512. A plurality of cylindrical lenses 523 arranged in parallel to each other are formed on the cylindrical lens surface 522 opposite to the plane 521.

  The lenticular lens sheet 52 includes a base material portion 503 and a lens portion 504 that is formed on the base material 503 and includes a plurality of cylindrical lenses. The base material portion 503 is made of the same resin as the base material portion 500, and the lens portion 504 is made of an ultraviolet curable resin or a resin that is cured by ionizing radiation other than ultraviolet light.

[Production method]
The microlens array sheet 51 and the lenticular lens sheet 52 can be manufactured by a normal manufacturing method. An example of a process for manufacturing the microlens array sheet 51 is as follows. A roll plate having a plurality of concave portions corresponding to the microlens 513 on the surface is prepared. An ultraviolet curable resin is applied onto the roll plate by a die coater. After application, the lens unit 501 is transferred to the substrate unit 500 by irradiating with ultraviolet rays while pressing the sheet-like substrate unit 500 against the roll plate. The microlens array sheet 51 can be manufactured through the above steps. The lenticular lens sheet 52 can also be manufactured by the same manufacturing method as the microlens array sheet 51. At this time, a roll plate having a plurality of grooves on the surface having the same transverse shape as the cylindrical lens 523 is used.
In the above-described manufacturing method, the ultraviolet curable resin is applied on the roll plate, but the ultraviolet curable resin may be applied on the base material portion 500. In this case, the microlens array sheet 51 and the lenticular lens sheet 52 can be manufactured by irradiating ultraviolet rays while pressing the roll plate against the ultraviolet curable resin applied on the base material portion 500. Moreover, you may apply | coat an ultraviolet curable resin on the roll plate and the base-material part 500. FIG.

[Action]
The backlight device 10 including the optical member 15 condenses the diffused light emitted from the surface light source 11 and improves the front luminance. The backlight device 10 further maintains a wide width of the luminance angle distribution. The backlight device 10 further suppresses an extreme change in inclination in the luminance angle distribution and suppresses the occurrence of side lobes. Hereinafter, these features will be described.

  In general, the width of the luminance angle distribution obtained by stacking two lens sheets having a condensing function is narrower than the width of the luminance angle distribution obtained by one lens sheet having a condensing function. For example, the luminance angle distribution of a single prism sheet having prism lenses arranged in parallel in the vertical direction is as shown in FIG. On the other hand, the luminance angle distribution of the preceding optical member 300 having prism lenses arranged side by side in the vertical direction is as shown in FIG. Comparing both, it can be seen that the width of the luminance angle distribution in the vertical direction of the preceding optical member 300 is narrower than the width of the luminance angle distribution in the vertical direction of the prism sheet alone.

  On the other hand, although the optical member 15 provided in the backlight device 10 has a lenticular lens sheet 52 laid on the microlens array sheet 51 to increase the front luminance, the luminance angle distribution in the vertical direction. Reduction in width can be suppressed. Hereinafter, this point will be described.

  FIG. 7 is a luminance angle distribution of a single lenticular lens sheet 52 having a plurality of cylindrical lenses 523 arranged in the vertical direction (y direction in FIG. 1). FIG. 8 shows a luminance angle distribution of the optical member 15 having a plurality of cylindrical lenses 523 arranged in parallel in the vertical direction.

  Referring to FIG. 7, the width of the luminance angle distribution in the vertical direction (y direction) of the single lenticular lens sheet 52 is wide. Specifically, the 1/2 viewing angle range is a range of ± 41 deg, which is larger than the range of ± 35 deg. Here, the 1/2 viewing angle range is obtained by the following method. The average of the luminance at the viewing angle 0 deg in the luminance angle distribution in the vertical direction and the luminance at the viewing angle 0 deg in the luminance angle distribution in the horizontal direction is defined as the front luminance (au) of the optical member. In FIG. 7, the front luminance is 1.54a. u. It is. A viewing angle range indicating a luminance of 1/2 or more of the obtained front luminance is defined as a 1/2 viewing angle range. In FIG. 7, the luminance is 0.77a. u. The above viewing angle range becomes the 1/2 viewing angle range.

On the other hand, the width of the vertical luminance angle distribution of the optical member 15 shown in FIG. 8 is not significantly narrower than the vertical luminance angle distribution width of the single lenticular lens sheet 52 of FIG. That is, when the lenticular lens sheet 52 is laid on the microlens array sheet 51, a reduction in the width of the luminance angle distribution in the vertical direction is greatly suppressed. Therefore, the optical member 15 has high front luminance and can maintain a wide luminance angle distribution in the vertical direction. Specifically, the ½ viewing angle range can be made larger than the range of ± 35 deg. In FIG. 8, the vertical viewing angle range is ± 37 deg. In FIG. 8, the front luminance is 1.9 a. u. Therefore, 0.95a. u. The viewing angle range showing the above luminance is defined as a 1/2 viewing angle range.
Note that the luminance angle distribution in the left-right direction of the optical member 15 is narrower than the luminance angle distribution in the left-right direction of the lenticular lens sheet 52 alone. Therefore, in the optical member 15, it is considered that the decrease in the luminance angle distribution width in the left-right direction contributes to the improvement of the front luminance. Although the luminance angle distribution in the left-right direction of the optical member 15 is narrower than the luminance angle distribution of the lenticular lens sheet 52 alone, the ½ viewing angle range is larger than ± 50 deg. In FIG. 8, the viewing angle distribution in the left-right direction is ± 51 deg. Therefore, the optical member 15 can maintain a wide width of the luminance angle distribution in the biaxial direction (vertical direction and horizontal direction).

  In the luminance angle distribution in the left-right direction shown in FIG. 8, the luminance smoothly decreases as the viewing angle increases. Like the luminance angle distribution in the left-right direction of the preceding optical member 300 shown in FIG. The points P1 and P2 at which the slope of the angle changes extremely are not generated. Therefore, it is possible to prevent the user who views the screen from the left and right directions from feeling uncomfortable.

  Further, in the vertical luminance angle distribution shown in FIG. 8, the occurrence of side lobes is suppressed. That is, the optical member 15 can suppress the occurrence of side lobes.

  Further, as shown in FIG. 8, the optical member 15 has a wider luminance angle distribution in the left-right direction than a luminance angle distribution in the vertical direction. In a liquid crystal display, it is preferable that the luminance angle distribution in the horizontal direction is wider than the luminance angle distribution in the vertical direction. This is because the user of the display device has more opportunities to view with a larger viewing angle in the left-right direction than in the up-down direction. The optical member 15 has a lenticular lens sheet 52 laid on a microlens array sheet 51 and a cylindrical lens 523 arranged in parallel in the vertical direction (y direction in FIG. 1). Therefore, the luminance angle distribution in the horizontal direction can be made wider than the luminance angle distribution in the vertical direction. When the microlens array sheet 51 is laid on the lenticular lens sheet 52 instead of laying the lenticular lens sheet 52 on the microlens array sheet 51, the front luminance is improved, but the luminance angles in the vertical and horizontal directions are improved. The widths of the distributions are both narrowed and the same width.

  Since the display screen of the display device 1 is long in the horizontal direction, the optical member 15 has a rectangular shape. That is, the microlens array sheet 51 and the lenticular lens sheet 52 are rectangles having the same size as each other, and the cylindrical lenses 523 are arranged in parallel in the short side direction. As a result, the luminance angle distribution in the long side direction (left-right direction) becomes wider than the luminance angle distribution in the short side direction (vertical direction). 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. Further, when the display screen is not rectangular, the microlens array sheet 51 and the lenticular lens sheet 52 do not have to be rectangular, and may have any shape corresponding to the display screen.

The convex surface of the microlens 513 is preferably a spherical surface. This is because if the convex surface is spherical, the diffused light from the surface light source 11 can be condensed isotropically. More preferably, the curvature radius R ₅₁₃ of the convex surface of the microlens ₅₁₃ is 10 to 50 μm, and the height H ₅₁₃ of the microlens from the apex of the convex surface to the lens plane (surface including the edge of the convex lens) 514 is 5 to 50 μm. . Preferably, the ratio (hereinafter referred to as the flat portion ratio) of the region where the microlens 513 is not formed on the microlens surface 512 (hereinafter referred to as the flat portion) to the entire microlens surface 512 (hereinafter referred to as the flat portion ratio) is 10 to 60%. A height H ₅₁ of ₅₁ is 100 to 300 μm. The flat portion ratio is a value (%) obtained by dividing the total area of the flat portion by the area of the microlens surface 512 when the microlens surface 512 is viewed from directly above (that is, the same area as the plane 511). The microlens array sheet 51 preferably has a smaller flat portion ratio. This is because the flat portion does not contribute to light collection. If the microlenses are arranged in a hexagonal close-packed arrangement, the flat portion ratio can be reduced.

  The cross-sectional shape of the cylindrical lens 523 is preferably an arc or an elliptical arc. Also, adjacent cylindrical lenses 523 are preferably in contact with each other. That is, it is preferable that there is no gap between the adjacent cylindrical lenses 523. This is because the gap does not contribute to light collection. When the surface light source 11 is composed of a plurality of line light sources (cold cathode tubes 13) arranged in parallel in the vertical direction as in the present embodiment, uneven brightness in the vertical direction occurs in the front luminance of the surface light source 11 itself. Prone to occur. Cylindrical lenses arranged side by side in the vertical direction have high light collecting properties in the vertical direction. Therefore, if the parallel direction of the cylindrical lenses is the same as the parallel direction of the plurality of line light sources constituting the surface light source, and the adjacent cylindrical lenses are in contact with each other, the luminance that can be generated in the parallel direction of the line light sources Unevenness can be eliminated.

  In order to bring adjacent cylindrical lenses into contact with each other without a gap, an angle (hereinafter referred to as a contact angle) θc formed by a surface (lens plane) including an edge of the cylindrical lens 523 and a convex surface is preferably an acute angle. When θc is set to an acute angle, a cylindrical lens having an elliptical arc whose transverse shape is the end point of the major axis of the lens has a higher light condensing effect than a circular cylindrical lens. Therefore, more preferably, the cross-sectional shape of the cylindrical lens 523 is an elliptical arc whose long-axis end point is the lens apex.

The elliptical arc preferably has a minor axis diameter of 10 to 130 μm, a major axis diameter of 20 to 400 μm, and a height H ₅₂₃ from the lens apex to the lens plane of 4 to 80 μm. The distance between apexes (hereinafter referred to as arrangement pitch) Pc of adjacent cylindrical lenses is preferably 10 to 100 μm, and the height H ₅₂ of the lenticular lens sheet is preferably 100 to 350 μm.

  As described above, the liquid crystal panel 20 has a plurality of pixels arranged in a matrix. Of the pixels arranged in the vertical direction (y direction), when the distance between the center of a certain pixel and the center of the other adjacent pixel is the pixel arrangement pitch Pp (μm), the pixel arrangement pitch Pp and the cylindrical If the lens arrangement pitch Pc satisfies the equation (1), the occurrence of moire fringes can be suppressed.

  Pc ≦ Pp / 5 (1)

[Example 1]
The optical member according to the present embodiment having the shape shown in FIGS. 3 to 5 and the preceding optical member having the shape shown in FIG. 14 were manufactured, and the respective luminance angle distributions were investigated.

  A microlens array sheet constituting the optical member according to this example was manufactured by the following method. A roll plate having a surface in which a plurality of concave portions corresponding to the microlenses were arranged in a hexagonal close-packed shape was prepared. Further, a polyethylene terephthalate (PET) film having a thickness of 188 μm was prepared as a base material. An ultraviolet curable resin was applied onto the roll plate using a die coater. Subsequently, the roll plate was pressed while conveying the PET film in the longitudinal direction, and the ultraviolet curable resin was cured by irradiating with ultraviolet rays to obtain a microlens array sheet.

  Moreover, the lenticular lens sheet which comprises the optical member by a present Example was manufactured by the method similar to a micro lens array sheet. Specifically, roll plates each having an elliptical arc shape and each having a plurality of grooves extending in the circumferential direction and arranged in parallel in the axial direction are prepared, and ultraviolet rays are prepared on the prepared roll plates. A cured resin was applied. Subsequently, the roll plate was pressed against a 188 μm-thick PET film, and the ultraviolet curable resin was cured by irradiating the ultraviolet curable resin to obtain a lenticular lens sheet.

  The shape dimensions of the manufactured microlens array sheet were as follows. The radius of the lens plane of each microlens was 15 μm and the height was 15 μm. The curvature radius of the convex surface was 15 μm. The shortest distance from the edge of the microlens to the edge of the other adjacent microlens (hereinafter referred to as the flat part shortest distance) was 7.8 μm, and the flat part ratio was 43%. The height of the microlens array sheet was 210 μm. Moreover, the shape dimension of the manufactured lenticular lens was as follows. The cross-sectional shape of each cylindrical lens was an elliptical arc having the major axis end point as the lens apex, the major axis diameter being 100 μm, the minor axis diameter being 58.8 μm, and the height being 23.7 μm. The contact angle θc was 70 deg and the arrangement pitch Pc was 50 μm. The height of the lenticular lens sheet was 220 μm.

  The preceding optical member was manufactured by the same method as the optical member of the above-described embodiment. The size and shape of the microlens array sheet was the same as the microlens array sheet constituting the optical member of this example. Moreover, the shape dimensions of the prism sheet were as follows. The apex angle of each prism was 90 deg and the height was 25 μm. Neighboring prisms were in contact with each other. The height of the prism sheet was 220 μm.

  The luminance angle distribution was investigated using the produced optical member of this example. The cold cathode tube was accommodated, an optical member was laid in a housing in which a reflective film was laid on the inner surface and a light diffusion plate was fitted in the opening. At this time, the parallel arrangement direction of the cylindrical lenses was the vertical direction.

  After laying the optical member of this example on the housing, the luminance angle distribution was examined. The viewing angle is defined by taking the normal direction (front) of the optical member 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-right viewing angle. . The luminance at each vertical viewing angle and left and right viewing angle was measured with a luminance meter.

  Similarly, the brightness angle distribution was investigated by laying a preceding optical member as a comparative example on the housing. At this time, the parallel arrangement direction of the prism lenses was the vertical direction.

The luminance angle distribution of the optical member of this example is as shown in FIG. 8, and the luminance angle distribution of the preceding optical member as a comparative example is as shown in FIG. The front luminance of the optical member of this example was 1.9 (au), which was higher than the front luminance (= 1.55) of the prism sheet alone. Moreover, the brightness angle distribution in the vertical direction and the horizontal direction of the optical member of the present example maintained a certain extent. Specifically, the 1/2 viewing angle range in the vertical direction (viewing angle range in which the luminance is 0.95 a.u. or more) is a range of ± 37 deg, which is larger than the range of ± 35 deg. The ½ viewing angle range in the left-right direction is a range of ± 51 deg, which is larger than the range of ± 50 deg. On the other hand, in the preceding optical member, the 1/2 viewing angle range of the luminance angle distribution in the vertical direction was ± 30 deg.
In addition, the luminance angle distribution of the optical member of the present embodiment is a smooth and natural orientation distribution in both the vertical direction and the horizontal direction, and an extreme change in the inclination of the luminance angle distribution (points P1 and P2) as in the preceding optical member. )There was no. Moreover, in the luminance angle distribution in the vertical direction of the optical member of this example, generation of side lobes was suppressed.

Further, using the optical member of the present example, the investigation of luminance unevenness and moire fringes was performed by the following method. First, a housing for observing luminance unevenness and moire fringes was prepared. Sixteen cold-cathode tubes were arranged in parallel in the prepared housing. The distance between adjacent cold cathode axes was 20 to 26.5 mm. A diffuser plate having a total light transmittance of 65% was fitted in the front of the housing. The size of the diffuser was 32 inches. The optical member of this example was laid on the front of the prepared housing. At this time, the parallel arrangement direction of the cylindrical lenses was the vertical direction. Then, a liquid crystal panel including a plurality of pixels arranged in a matrix was laid on the optical member to produce a liquid crystal display device. Among the plurality of pixels, the arrangement pitch Pp of the pixels arranged in the vertical direction was 500 μm. Therefore, Pc (= 50 μm) of the optical member of the present example is Pp / 5 (= 100 μm) or less, which satisfies Expression (1).
The luminance unevenness was visually observed for all viewing angles of the manufactured liquid crystal display. As a result, no luminance unevenness was found. Furthermore, moiré fringes were visually observed for all viewing angles. As a result, no moire fringes were found.

[Example 2]
An optical member provided with a lenticular lens sheet having a shape different from that of Example 1 was manufactured, and the luminance angle distribution was investigated. Specifically, a microlens array sheet and a lenticular lens sheet were manufactured in the same manner as in Example 1. The shape dimensions of the manufactured lenticular lens sheet were as follows. The cross-sectional shape of each cylindrical lens was an elliptical arc whose major axis end point was the lens apex, the major axis diameter was 100 μm, the minor axis diameter was 58.8 μm, and the height was 22.0 μm. The contact angle θc was 67.4 deg and the arrangement pitch Pc was 48 μm. The height of the lenticular lens sheet was 215 μm. The other shape dimensions of the lenticular lens sheet and the shape dimensions of the microlens array were the same as those of the optical member of Example 1. The manufactured optical member was laid on the housing in the same manner as in Example 1, and the luminance angle distribution was examined. The side-by-side direction of the cylindrical lenses was the vertical direction.

  FIG. 9 shows the luminance angle distribution of the optical member of this example. Referring to FIG. 9, the front luminance of the optical member of the present example was 1.9 (au). Further, in the luminance angle distribution of the optical member of this example, the vertical viewing angle range (viewing angle range in which the luminance is 0.95 a.u. or more) is a range of ± 36 deg. It was bigger than the range. The ½ viewing angle range in the left-right direction was a range of ± 50.5 deg, which was larger than the range of ± 50 deg. Further, the luminance angle distribution in the vertical direction and the horizontal direction of the optical member of this example was a smooth and natural orientation distribution, and the occurrence of side lobes was suppressed in the luminance angle distribution in the vertical direction.

Furthermore, a liquid crystal display device was manufactured using the same luminance unevenness and moire fringe observation housing as in Example 1, the optical member of this example, and the same liquid crystal panel as in Example 1. At this time, Pc (= 48 μm) was less than Pp / 5 (= 100 μm), which satisfied Expression (1).
The luminance unevenness was visually observed for all viewing angles of the manufactured liquid crystal display. As a result, no luminance unevenness was found. Furthermore, moiré fringes were visually observed for all viewing angles. As a result, no moire fringes were found.

[Example 3]
An optical member provided with a microlens array sheet having a shape different from those in Examples 1 and 2 was manufactured, and the luminance angle distribution was investigated. Specifically, a microlens array sheet and a lenticular lens sheet were manufactured in the same manner as in Example 1. The shape dimensions of the manufactured microlens array sheet were as follows. The lens plane radius of each microlens was 15 μm, the height was 15 μm, and the curvature radius of the convex surface was 15 μm. The shortest flat portion distance was 5.2 μm, and the flat portion ratio was 34%. The other shape dimensions of the microlens array sheet and the shape dimensions of the lenticular lens sheet were the same as those in Example 1. The manufactured optical member was laid on the housing in the same manner as in Example 1, and the luminance angle distribution was examined. The side-by-side direction of the cylindrical lenses was the vertical direction.

  FIG. 10 shows the luminance angle distribution of the optical member of this example. The front luminance of the optical member of this example was 1.95 (au). The vertical viewing angle range (viewing angle range in which the luminance is 0.975 au or higher) was ± 36 deg. The ½ viewing angle range in the left-right direction was ± 50.5 deg. Other optical characteristics were the same as those of the optical member of Example 1.

[Example 4]
An optical member provided with a microlens array sheet having a shape different from those of Examples 1 to 3 was manufactured, and the luminance angle distribution was investigated. Specifically, a microlens array sheet and a lenticular lens sheet were manufactured in the same manner as in Example 1. The shape dimensions of the manufactured microlens array sheet were as follows. The lens plane radius of each microlens was 15 μm, the height was 15 μm, and the curvature radius of the convex surface was 15 μm. The shortest flat portion distance was 11.2 μm, and the flat portion ratio was 52%. The other shape dimensions of the microlens array sheet and the shape dimensions of the lenticular lens sheet were the same as those in Example 1. The manufactured optical member was laid on the housing in the same manner as in Example 1, and the luminance angle distribution was examined. The side-by-side direction of the cylindrical lenses was the vertical direction.

  FIG. 11 shows the luminance angle distribution of the optical member of this example. The front luminance of the optical member of this example was 1.85 (au). The vertical viewing angle (viewing angle range in which the luminance is 0.925 a.u. or higher) was ± 36 deg. The ½ viewing angle range in the left-right direction was ± 51 deg. Other optical characteristics were the same as those of the optical member of Example 1.

[Comparative Example 1]
A prism sheet having a cross-sectional shape shown in FIG. 12 was produced in the same manner as in Example 1. The geometry of the prism sheet was as follows. The apex angle of each prism was 90 deg and the height was 25 μm. Neighboring prisms were in contact with each other. The height of the prism lens sheet (height from the apex of the prism to the bottom surface of the prism lens sheet) was 220 μm.

  The manufactured prism sheet was laid on the above-described housing, and the luminance angle distribution was investigated. At this time, the parallel arrangement direction of the prisms was the vertical direction. The obtained luminance angle distribution was as shown in FIG. The front luminance was 1.55 (au).

[Comparative Example 2]
The luminance angle distribution of the single microlens array sheet manufactured in Example 1 was investigated by the same method as in Example 1. FIG. 13 shows the luminance angle distribution of the microlens array sheet of this comparative example. The front luminance of this comparative example is 1.53a. u. It was slightly lower than the front luminance of the prism sheet of Comparative Example 1. The ½ viewing angle range was ± 50 deg in both the vertical direction and the horizontal direction.

[Comparative Example 3]
The luminance angle distribution of the single lenticular lens sheet manufactured in Example 1 was investigated by the same method as in Example 1. The luminance angle distribution of the lenticular lens sheet of this comparative example is shown in FIG. The front luminance of this comparative example is 1.54 a. u. It was slightly lower than the front luminance of the prism sheet of Comparative Example 1. The vertical viewing angle range was ± 41 deg, and the horizontal viewing angle range was ± 59 deg.

  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 display device including a backlight device according to an embodiment of the present invention. It is sectional drawing in line segment II-II in FIG. It is a perspective view of the optical member shown in FIG. It is sectional drawing of the micro lens array sheet which comprises the optical member shown in FIG. It is sectional drawing of the lenticular lens sheet which comprises the optical member shown in FIG. It is a luminance angle distribution map of a prism sheet alone. It is a luminance angle distribution diagram of a lenticular lens sheet alone. FIG. 3 is a luminance angle distribution diagram of the optical member of Example 1. 6 is a luminance angle distribution diagram of the optical member of Example 2. FIG. FIG. 10 is a luminance angle distribution diagram of the optical member of Example 3. FIG. 10 is a luminance angle distribution diagram of the optical member according to Example 4. It is sectional drawing of a prism sheet. It is a luminance angle distribution figure of the micro lens array sheet simple substance which is a comparative example. It is a perspective view of the optical member indicated by prior art literature. It is a luminance angle distribution map of the optical member shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Display apparatus 10 Backlight apparatus 11 Surface light source 20 Liquid crystal panel 51 Micro lens array sheet 52 Lenticular lens sheet 511,521 Plane 512 Micro lens surface 513 Micro lens 522 Cylindrical lens surface 523 Cylindrical lens

Claims (7)

A surface light source;
A microlens array sheet having a flat surface facing the surface light source, and a microlens surface opposite to the flat surface and having a plurality of microlenses formed thereon,
A backlight comprising: a lenticular lens sheet having a plane facing the microlens surface; and a cylindrical lens surface on which a plurality of cylindrical lenses arranged in parallel to each other on the opposite side of the plane are formed. apparatus. The backlight device according to claim 1,
The microlens array sheet and the lenticular lens sheet are rectangular,
The backlight device, wherein the plurality of cylindrical lenses are arranged in parallel in a short side direction of the lenticular lens sheet. The backlight device according to claim 1,
A backlight device, wherein the convex surface of the microlens is a spherical surface. The backlight device according to claim 1,
The backlight device, wherein the cylindrical lens is in contact with the other adjacent cylindrical lens. A surface light source;
A microlens array sheet having a flat surface facing the surface light source, and a microlens surface opposite to the flat surface and having a plurality of microlenses formed thereon,
A lenticular lens sheet having a plane opposed to the microlens surface, and a cylindrical lens surface formed with a plurality of cylindrical lenses opposite to the plane and arranged in parallel with each other;
And a display panel including a plurality of pixels laid on the cylindrical lens surface and arranged in a matrix. The display device according to claim 5,
The display device characterized in that an arrangement pitch Pc of the plurality of cylindrical lenses and an arrangement pitch Pp of pixels arranged in the same direction as the arrangement direction of the cylindrical lenses among the plurality of pixels satisfy Expression (1). .
Pc ≦ Pp / 5 (1) An optical member used in a backlight device,
A microlens array sheet having a microlens surface on which a plurality of microlenses are formed;
An optical member comprising: a plane facing the microlens surface; and a lenticular lens sheet having a cylindrical lens surface formed with a plurality of cylindrical lenses arranged in parallel to each other on the opposite side of the plane. .

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