JP3585509B2 - Transmissive liquid crystal display - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a transmission type liquid crystal display device using a surface light source device as a backlight.
[0002]
[Prior art]
As shown in FIG. 5, a conventional surface light source device includes a transparent light guide plate 1 made of an acrylic resin or the like, and a translucent diffusion sheet 2 having a high transmittance is provided on one surface of the transparent light guide plate 1. A prism lens sheet 3 in which lenses are arranged is provided thereon, and a light diffusion reflection sheet 5 for diffusing and reflecting light is provided on the other surface of the transparent light guide plate 1. Light from a light source 6 is incident from the side end surface of the transparent light guide plate 1, and the light is diffusely reflected by the specular reflection layer 7 and the light diffusion pattern 8 of the light diffusion reflection sheet 5 to emit light on the light emission surface 9 side. A surface light source device having such a configuration is known (actually disclosed in Japanese Utility Model Application Laid-Open No. 4-107201, Example 1). In the present invention, the prism lens sheet 3 has a function of directing the light emitted from the light emitting surface 9 in a certain direction, and the brightness in that direction increases.
[0003]
Further, as another conventional surface light source device, as shown in FIG. 6, a transparent light guide plate 1 made of acrylic resin or the like is provided, and one surface of the transparent light guide plate 1 is a light emitting surface 9, and this transparent light guide plate 1 A light diffusing / reflecting sheet 5 for diffusing and reflecting light is provided on the other surface of the light guide plate 1. Light from a light source 6 is incident from a side end surface of the transparent light guide plate 1, and the light is transmitted to the light diffusing / reflecting sheet 5. There is known a surface light source device configured to emit light on the light emitting surface 9 side by diffusing and reflecting the light from the specular reflection layer 7 and the light diffusion pattern 8 (JP-A-1-245220, Example 2). In the present invention, the light diffusion pattern of the light diffusion reflection sheet 5 is formed by applying the light scattering substance 10, and the light diffusion substance 10 becomes denser as the distance from the light incident portion of the light source 6 increases. This makes the luminance distribution of the surface light source device uniform.
[0004]
However, in the prior art described above, in Example 1, if the light diffusion pattern 8 of the light diffusion reflection sheet 5 is made fine in order to make the luminance distribution uniform, an optical moire phenomenon occurs with the prism lens sheet 3 and the nonuniformity due to the moire pattern occurs. When the light diffusion pattern was large, the light diffusion pattern 8 appeared in the luminance distribution, and sufficient uniformity could not be obtained. Therefore, it is necessary to provide the translucent diffusion sheet 2 having a large diffusion effect, and the translucent diffusion sheet 2 alleviates the light diffusion pattern 8 from appearing in the luminance distribution. Increasing the diffusion effect increases the amount of light absorption, and also reduces the effect of increasing the luminance near the normal direction of the light emitting surface by the prism lens sheet 3 because the light is also diffused near the tangential direction of the light emitting surface unnecessary for display. There was a problem that was.
Therefore, in order to increase the brightness of the surface light source device, the brightness of the light source 6 must be increased, which causes a problem that the life of the light source is shortened and power consumption is increased.
Further, in Example 2, although the effect of uniformizing the luminance distribution is achieved to some extent, there is a limit because the translucent diffusion sheet is not used, and the luminance near the normal direction is low because the prism lens sheet 3 cannot be used. Was inferior.
[0005]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a high light emission luminance in the normal direction near the light emitting surface, it is to provide a transmission type liquid crystal display device using the backlight luminance distribution uniform surface light source device .
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present inventor has conducted various studies, and as a result, a light guide plate, a prism lens sheet provided with lenses arranged on the light emitting surface side of the light guide plate, and provided on the back side of the light guide plate. In the surface light source device having the light diffusion reflection means in which the light diffusion patterns are arranged, the prism lens sheet and the prism lens sheet are arranged such that the arrangement axis of the light diffusion pattern forms a predetermined angle with respect to the arrangement axis of the lenses of the prism lens sheet. after having earned a light diffuse reflection means, the arrangement axis of the array axis and a prism lens sheet lenses of the pixel of the liquid crystal display device by the to Turkey at a predetermined angle, high emission luminance in the normal direction near The present invention has been found to achieve a transmission-type liquid crystal display device having a uniform luminance distribution and not causing moiré between the liquid crystal display device and the prism lens sheet, and achieving the above object. It was led to the completion.
[0007]
[Action]
Provided on the light-emitting surface side of the surface light source device, the brightness near the normal direction of the light-emitting surface is enhanced by the refraction and condensing action of the prism lens sheet on which the lenses are arranged, and the uniformity of the brightness is obtained by the light-diffuse reflection means with the arranged light-diffusion patterns At this time, the prism lens sheet and the light diffusion reflection sheet are arranged such that the arrangement axis of the printing dots (light diffusion pattern) forms an angle with respect to the arrangement axis of the lenses of the prism lens sheet. Accordingly, optical moiré (between the prism lens sheet and the light diffusion pattern) does not occur, and the light diffusion pattern of the light diffusion / reflection means can be made invisible, so that both high luminance and uniform luminance can be achieved.
Also, if a translucent diffusion sheet is not required at all, or if used, the diffusion effect is small and the amount of light absorbed is small, so that the luminance is uniform and the high luminance by the prism lens sheet is extremely effective. .
Furthermore, the alignment axis of the alignment axis and the prism lens sheet lenses of the pixel of the liquid crystal display device by the to Turkey at a predetermined angle, does not occur even moire between the liquid crystal display device and a prism lens sheet.
[0008]
【Example】
The present invention will be described below with reference to preferred embodiments.
FIG. 1 is a diagram schematically showing a cross section of the surface light source device of the present invention. Particularly, a case of an edge light type (also called a side light type) is illustrated. In FIG. 1, reference numeral 1 denotes a transparent light guide plate made of acrylic resin, glass, or the like. A translucent diffusion sheet 2 having a high transmittance is provided on one surface of the transparent light guide plate 1, and a prism on which a lens is further arranged is provided. A lens sheet 3 is provided. Further, light diffusing / reflecting means 5 for diffusing and reflecting light is provided on the other surface of the transparent light guide plate 1. Light from a light source 6 is incident from a side end surface of the transparent light guide plate 1, and the light is reflected by the light. The light is diffused and reflected by the specular reflection layer 7 and the light diffusion pattern 8 of the diffuse reflection means 5 to emit light on the light emitting surface 9 side. In the present invention, the prism lens sheet 3 has a function of directing the light emitted from the light emitting surface 9 in a certain direction, and the brightness in that direction increases. The maximum direction of the luminance is usually the normal direction of the light emitting surface 9. The light diffusion pattern of the light diffusion / reflection means 5 is obtained by applying the light scattering substance 10 in, for example, a dot shape by printing or the like, so that the area of the light scattering substance 10 increases as the distance from the light incident portion of the light source 6 increases. It is configured to make the luminance distribution of the surface light source device uniform.
Here, the light guide plate may be hollow as disclosed in JP-A-63-318003 (US Pat. No. 7,491,540) and JP-A-63-181201.
[0009]
Figure 2 is a diagram schematically showing a plane of Sekiru surface light source device of the present invention. In FIG. 2, reference numeral 11 denotes an arrangement axis of (the lens of) the prism lens sheet 3, and reference numeral 12 denotes an arrangement axis of the light diffusion pattern 8. The array axis 11 and the array axis 12 form an angle θ. In the present invention, this angle is in the range of 15 to 75 degrees, and has a function of making the light diffusion pattern of the light diffusion reflection sheet invisible without causing moire.
[0010]
The prism lens sheet 3 that can be used in the present invention may be of any type. For example, as shown in FIG. 3, a triangular prism type lenticular lens 13, a circular or elliptic cylindrical convex lenticular lens 14, a circular or elliptical cylindrical concave lenticular lens 15, a pyramid lens 16, a fly-eye lens 17, and the like can be used. . As shown at 18 in FIG. 3, one prism lens sheet 3 can be used as a single layer, but it can be used as two layers by stacking two sheets in parallel or at right angles. It is also possible to use three or more layers. Furthermore, not only the same kind of prism lens sheets can be combined, but also different kinds of prism lens sheets can be used in combination.
The material of the prism lens sheet is not particularly limited, and may be any material as long as it is optically transparent. Thermoplastic resins, or heat, ultraviolet rays, may be any of curable resins that are cross-linked by an electron beam, for example, acrylic resin, vinyl chloride resin, polycarbonate resin, polyethylene resin, polyester resin, polypropylene resin, polyamide resin, etc. Can be used. Materials such as glass and quartz can also be used.
It is also possible to use a single material, but as shown in FIG. 8, a structure in which a prism lens formed of a transparent material is laminated on a transparent sheet-like (or plate-like) base material is used. You can also.
[0011]
The light diffusion / reflection means 5 that can be used in the present invention may be a light diffusion / reflection sheet 5. The light diffusion reflection sheet 5 has, for example, a dot-shaped light diffusion pattern 8 formed by printing or the like. The light diffusion pattern 8 is a light scattering substance 10 and is usually made of a high-whiteness ink or paint pigment. For example, titanium white, zinc oxide, calcium oxide, barium oxide, barium sulfate and the like can be used.
These pigments are dispersed in a spreading agent containing a binder, a solvent, and the like, and printed on the light diffusion reflection sheet 5 as printing ink, or applied to the light diffusion reflection sheet 5 as a paint. Alternatively, a method in which a tape-shaped member is attached to the light diffusion reflection sheet 5 may be used. The concentration of the light scattering material 10 is gradually increased as the distance from the light source side end of the transparent light guide plate 1 is increased, or the area of the light diffusion pattern 8 is increased. Thereby, the distribution of luminance in the surface light source device can be made uniform.
[0012]
On the other hand, the mirror reflection layer 7 of the light diffusion reflection sheet 5 has a mirror surface on which aluminum vapor deposition or the like is performed, and reflects light.
As described above, the specular reflection layer 7 and the light diffusion pattern 8 are provided on the light diffusion / reflection sheet 5, but they may be provided directly on the transparent light guide plate 1. In that case, the mirror reflection layer 7 is formed on the surface opposite to the light emitting surface 9, but the light diffusion pattern 8 may be provided on any surface of the transparent light guide plate 1, or may be provided on both surfaces.
[0013]
As shown in FIG. 4, the light diffusion pattern 8 includes dots arranged at regular intervals, a dot pattern 19 in which the dot diameter increases as the distance from the light source increases, and a random arrangement of dots. As the distance from the light source increases, the number of dots per unit area increases. A random pattern 20 for increasing the number, a wedge pattern 21 in which a plurality of wedge-shaped patterns are arranged in parallel so that the tips of the wedges face the light source, and lines are drawn at regular intervals, and the number of lines drawn increases as the distance from the light source increases Any pattern may be used as long as the pattern area increases as the distance from the light source increases, such as a line pattern 22 to be formed.
[0014]
In the prism lens sheet 3 and the light diffusion pattern 8 as described above, the angle θ between the arrangement axis 11 of the prism lens sheet 3 and the arrangement axis 12 of the diffusion pattern 7 is determined as follows.
The array axis 11 is the Y axis when the direction of the circle or elliptic cylinder of the circular or elliptic cylindrical convex lenticular lens is the Y axis direction, and the direction in which a plurality of circles or elliptic cylinders are arrayed is the X axis direction. The arrangement axis 12 is defined as the y-axis direction in which the direction of the dots of the light diffusion pattern 8 away from the light source 6 is the y-axis direction and the direction parallel to the light source 6 is the y-axis direction. It is assumed that the origins of both coordinate systems are O and o, and the origin O and the origin o coincide with each other in the coordinate system OXY and the coordinate system oxy.
At this time, in order to prevent moiré fringes, the angle between the Y axis and the y axis, that is, the angle θ between the array axis 11 and the array axis 12 is preferably set to 15 degrees or more and 75 degrees or less. Moiré fringes occur at 15 degrees or less and at 75 degrees or more.
[0015]
Further, when the angle θ is changed, the shadow of the dot which is the light diffusion pattern 8 changes, and when θ is θ = sin ⁻¹ (2/5 ⁻² ) = 63.5 degrees, the shadow of the dot is most visible. This makes it possible to realize the invisibleness of the dots that are the diffusion pattern 7. θ = 63.5 degrees is an angle at which the shadow of the dot is minimized, and particularly when θ is in the range of approximately 57 to 70 degrees, it is the optimum range in which the shadow of the dot is not visible.
Since θ is symmetric whether measured from the X axis (x axis) or from the Y axis (y axis), θ and 90−θ give the same result, and θ = 90−63.5 = 26 In the case of 0.5 degrees, the same result as when θ = 63.5 degrees is obtained.
[0016]
Whereas the arrangement axis of the conventional prism lens sheet and the arrangement axis of the diffusion pattern are perpendicular or parallel, in the present invention, since these axes form an angle, shadows of the diffusion pattern are difficult to see and moire fringes also occur. Therefore, in the translucent diffusion sheet 2 of the present invention, both the haze (haze value) and the amount of absorbed light can be reduced to 以下 or less.
Further, it can be omitted altogether depending on the invisibility of the diffusion pattern, the half angle of light diffusion of the surface light source, and the luminance.
[0017]
When the surface light source device of the present invention is used as a backlight of a transmissive LCD display device (liquid crystal display device), in the prism lens sheet 3, the lens arrangement cycle is such that moire does not occur with the pixels of the LCD display. (1) "The pixel arrangement axis and the arrangement axis of the prism lens sheet 3 also form an angle of 15 to 75 degrees." Or (2) "One third or less of the pixel arrangement cycle or 3 More than twice. " When the lens is larger, that is, three times or more, the cycle of the lens becomes noticeable. However, when the arrangement period of the lenses is about 1 μm or less, a light diffraction phenomenon occurs. Therefore, the arrangement period of the lenses is 1 μm or more. Assuming that the arrangement period of the pixels of the LCD display is 300 μm, the arrangement period of the lens is preferably 10 to 100 μm.
Further, the arrangement period of the dots as the diffusion pattern 7 is preferably 100 μm to 5000 μm from the viewpoint of inconspicuousness of dots, luminance, and uniformity in the plane.
As the light source 6, a linear light source such as a fluorescent lamp or a point light source such as an incandescent lamp is used.
Further, as shown in FIG. 7, the light source device of the present invention may be configured in a direct type (commonly known).
[0018]
【The invention's effect】
The effect in the surface light source device portion is that the prism lens sheet and the light diffuse reflection are arranged such that the light diffusion dot arrangement axis of the light diffusion reflection sheet forms a predetermined angle with respect to the lens arrangement axis of the prism lens sheet. By arranging the sheets, optical moiré due to both sheets does not occur, and the light diffusion pattern of the light diffusion reflection sheet can be made invisible, so that both high luminance and uniform luminance can be achieved. Also, if a translucent diffusion sheet is not required at all, or even if it is used, the diffusion effect is small and the amount of light absorbed is small, so that the luminance is uniform and the high luminance by the prism lens sheet is extremely effective. .
And further as the effect of the entire liquid crystal display device, the alignment axis of the alignment axis and the prism lens sheet lenses of the pixel of the liquid crystal display device of that between to Turkey as to form a predetermined angle, the surface light source device Moire caused by the prism lens sheet and the pixels of the liquid crystal display device does not occur.
[0019]
[Brief description of the drawings]
FIG. 1 is a schematic view of a cross section of a surface light source device of the present invention.
FIG. 2 is a schematic plan view of the surface light source device of the present invention.
FIG. 3 is a diagram of a prism lens sheet that can be used in the present invention.
FIG. 4 is a diagram of a light diffusion pattern of a light diffusion reflection sheet that can be used in the present invention.
FIG. 5 is a schematic view of a cross section of a conventional surface light source device.
FIG. 6 is a schematic diagram of a cross section of a conventional surface light source device.
FIG. 7 is a schematic cross-sectional view of the surface light source device of the present invention.
FIG. 8 is a diagram of a prism lens sheet that can be used in the present invention.
[Explanation of symbols]
1 Transparent light guide plate 2 Translucent diffusion sheet 3 Prism lens sheet 4 Light diffusion reflection means 5 Light diffusion reflection sheet 6 Light source 7 Specular reflection layer 8 Light diffusion pattern 9 Light emitting surface 10 Light scattering material 11 Arrangement axis of prism lens sheet 12 Light diffusion Pattern arrangement axis 13 Triangular prism type lenticular lens 14 yen or elliptic cylindrical convex lenticular lens 15 yen or elliptic cylindrical concave lenticular lens 16 Pyramidal lens 17 Fly eye lens 18 yen or two elliptical cylindrical convex lenticular lenses Overlaid lens 19 dot pattern 20 random dot pattern 21 wedge pattern 22 line pattern 23 transmissive liquid crystal display element 24 base sheet or substrate

Claims (2)

A surface light source device having at least a light guide plate, a prism lens sheet provided on a light emitting surface side of the light guide plate and arranged with lenses, and a light diffusion reflection unit provided behind the light guide plate and arranged with a light diffusion pattern. A transmissive liquid crystal display device used as a backlight of a liquid crystal display device,
The angle formed by the arrangement axis of the lens of the prism lens sheet and the arrangement axis of the light diffusion pattern is not less than 15 degrees and not more than 75 degrees, and the arrangement axis of the pixels of the liquid crystal display device and the lens of the prism lens sheet. Wherein the angle formed by the array axes is 15 degrees or more and 75 degrees or less. 2. The transmission type liquid crystal display device according to claim 1, wherein the surface light source device has a translucent diffusion sheet between the light guide plate and the prism lens sheet.

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