A liquid crystal display apparatus is provided in which occurrence of a moiré pattern can be prevented without largely reducing front luminance. A liquid crystal display apparatus 1 includes a surface light source 4, a liquid crystal display panel 2, and first and second prism sheets 5 and 6 for condensing light emitted from the surface light source 4 and guiding the light toward the liquid crystal display panel. The first and second prism sheets 5 and 6 are disposed such that prism array directions thereof are orthogonal to each other. When a pixel pitch of the liquid crystal display panel 2 is defined as pp [μm]; a prism array pitch of the first prism sheet 5 is defined as Px [μm]; and a prism array pitch of the second prism sheet 6 is defined as Py [μm], relationships of Px≤Pp/(14−0.045 pp) and Py≤Pp/(11.5−0.032 pp) are satisfied.
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0. 16. A condenser sheet for condensing light emitted from a light source and guiding a light toward a liquid crystal display panel having a pitch defined as pp in micrometers comprising ridges of a first corrugated structure having a first light-condensing characteristic that are periodically arranged on a first surface of the condenser sheet in a first direction of the liquid crystal display panel, wherein the first corrugated structure has an array pitch in micrometers defined as Px such that Px has a value greater than or equal to 10 microns and less than or equal to pp/(14−0.045Pp).
0. 21. A condenser sheet for condensing light emitted from a light source and guiding a light toward a liquid crystal display panel having a pitch defined as pp in micrometers comprising ridges of a second corrugated structure having a second light-condensing characteristic that are periodically arranged on a first surface of the condenser sheet in a second direction of the liquid crystal display panel, wherein the second corrugated structure has an array pitch in micrometers defined as Py such that Py has a value greater than or equal to 10 microns and less than or equal to pp/(11.5−0.032Pp).
0. 1. A liquid crystal display apparatus comprising:
a light source;
a liquid crystal display panel;
and condenser sheets for condensing light emitted from the light source and guiding the light toward the liquid crystal display panel,
the condenser sheets including:
a first condenser sheet in which ridges of a first corrugated structure having a first light-condensing characteristic are periodically arranged on one surface of the first condenser sheet in a longitudinal direction of the liquid crystal display panel; and
a second condenser sheet in which ridges of a second corrugated structure having a second light-condensing characteristic are periodically arranged on one surface of the second condenser sheet in a lateral direction of the liquid crystal display panel,
wherein, when a longitudinal, lateral, or sub-pixel pitch of the liquid crystal display panel is defined as pp, an array pitch of the first corrugated structure is defined as Px, and an array pitch of the second corrugated structure is defined as Py, the following relationships are satisfied: Px is approximately equal to pp/(14−0.045Pp) and Py is approximately equal to pp/(11.5−0.032Pp) such that moiré patterns are not produced by the condenser sheets and the liquid crystal display panel, and the condenser sheets do not significantly reduce the luminance from the liquid crystal display.
0. 2. The liquid crystal display apparatus according to
0. 3. The liquid crystal display apparatus according to
0. 4. The liquid crystal display apparatus according to
0. 5. The liquid crystal display apparatus according to
0. 6. The liquid crystal display apparatus according to
0. 7. The liquid crystal display apparatus according to
0. 8. A liquid crystal display apparatus comprising:
a liquid crystal display panel; and
condenser sheets for condensing light emitted from a light source and guiding the light toward the liquid crystal display panel,
the condenser sheets including:
a first condenser sheet in which ridges of a first corrugated structure having a first light-condensing characteristic are periodically arranged on one surface of the first condenser sheet in a longitudinal direction of the liquid crystal display panel; and
a second condenser sheet in which ridges of a second corrugated structure having a second light-condensing characteristic are periodically arranged on one surface of the second condenser sheet in a lateral direction of the liquid crystal display panel,
wherein, when a longitudinal, lateral, or sub-pixel pitch of the liquid crystal display panel is defined as pp, an array pitch of the first corrugated structure is defined as Px, and an array pitch of the second corrugated structure is defined as Py, the following relationships are satisfied: Px is approximately equal to pp/(14−0.045Pp) and Py is approximately equal to pp/(11.5−0.032Pp) such that moiré patterns are not produced by the condenser sheets and the liquid crystal display panel, and the condenser sheets do not significantly reduce the luminance from the liquid crystal display.
0. 9. The liquid crystal display apparatus according to
0. 10. The liquid crystal display apparatus according to
0. 11. The liquid crystal display apparatus according to
0. 12. The liquid crystal display apparatus according to
0. 13. The liquid crystal display apparatus according to
0. 14. The liquid crystal display apparatus according to
0. 15. The liquid crystal display apparatus according to
0. 17. The condenser sheet of claim 16, wherein the first corrugated structure is a prism structure having ridges of a triangular shape in cross section.
0. 18. The condenser sheet of claim 16, wherein the first corrugated structure includes aspheric lens structures.
0. 19. The condenser sheet of claim 16, wherein 10 microns≤Px≤50 microns and Pp≥222 microns.
0. 20. The condenser sheet of claim 16, wherein 10 microns≤Px≤20 microns and Pp≥144 microns.
0. 22. The condenser sheet of claim 21, wherein the second corrugated structure is a prism structure having ridges of a triangular shape in cross section.
0. 23. The condenser sheet of claim 21, wherein the second corrugated structure includes aspheric lens structures.
0. 24. The condenser sheet of claim 21, wherein 10 microns≤Py≤50 microns and Pp≥222 microns.
0. 25. The condenser sheet of claim 21, wherein 10 microns≤Py≤20 microns and Pp≥144 microns.
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As described above, by determining the array pitches of the respective corrugated structures of the first and second condenser sheets in accordance with the pixel pitch of the liquid crystal display panel, occurrence of a moiré pattern can be prevented without largely reducing front luminance of the liquid crystal display panel.
Preferably, Px≤50, Py≤50, and |Px−Py|<50 are satisfied when Pp≥222; Px≤20, Py≤20, and |Px−Py|<20 are satisfied when 222>Pp≥144; and Px≤15, Py≤20, and −20<Px−Py<15 are satisfied when 114>Pp≥136.5.
The first and second corrugated structures correspond to prism structures having ridges of a triangular shape in cross section if the condenser sheets are prism sheets. If the condenser sheets are lens sheets, the first and second corrugated structures have ridges of a lens shape, such as an aspheric lens, with a curved cross section.
As described above, according to the liquid crystal display apparatus of the present invention, occurrence of a moiré pattern can be prevented without largely reducing front luminance.
An embodiment of the present invention will now be described with reference to the drawings. The invention is not limited to the following embodiment, and various modifications can be made within the scope of the invention.
The liquid crystal display panel 2 includes pixels arranged in the longitudinal direction (X-direction in
The surface light source 4 is either a direct-lighting type in which a plurality of light sources are disposed on a surface or an edge-lighting type in which a light-guiding plate is used. The surface light source 4 irradiates the entire back surface of the liquid crystal display panel 2 with backlight. As the light sources, linear light sources such as fluorescent tubes or point light sources such as light-emitting diodes are used.
The first and second prism sheets 5 and 6 serve as “condenser sheets” of the invention for condensing light emitted from the surface light source 4 toward the front (in the Z-direction) so as to improve front luminance. The diffusion plate 7 is an optically functional element for diffusing and delivering the backlight so as to produce uniform luminance. The diffusion plate 7 may be provided between the first prism sheet 5 and the surface light source 4. Optically functional elements other than the first and second prism sheets 5, 6, and the diffusion plate 7 may also be provided, such as a polarization separation element that transmits one polarized component and reflects another polarized component, for example.
Each of the first and second prism sheets 5 and 6 is provided with a prism structure having ridges of a triangular shape in cross section on a light-output surface thereof. The prism structure correspond to a “corrugated structure” of the present invention.
On the first prism sheet 5, prisms 5P are arranged successively at a predetermined pitch in the longitudinal direction of the liquid crystal display panel 2 (the X-direction in
The first prism sheet 5 condenses light spreading in the X-direction, among the backlight emitted from the surface light source 4, toward the Z-direction. The second prism sheet 6 condenses light spreading in the Y-direction toward the Z-direction. Since the light spreading in the X- and Y-directions are condensed toward the front (in the Z-direction) by the first and second prism sheets 5 and 6, front luminance of the liquid crystal display apparatus 1 is more improved than in the case where only one prism sheet is provided.
The prism array pitch of the first prism sheet 5 and the prism array pitch of the second prism sheet 6 may be either the same or different. In general, the smaller the prism array pitch is, the lower the resultant front luminance becomes. Moreover, a moiré pattern of interference fringes may occur due to the periodic structures provided on the first and second prism sheets 5 and 6 and the display pixels provided on the liquid crystal display panel 2. The occurrence of such a moiré pattern can be prevented by reducing the prism array pitches of the first and second prism sheets 5 and 6. However, if the prism array pitches are excessively reduced, front luminance will be reduced considerably.
Hence, the liquid crystal display apparatus 1 of this embodiment is configured so that, when the pixel pitch of the liquid crystal display panel 2 is defined as Pp [μm], the prism array pitch of the first prism sheet 5 is defined as Px [μm], and the prism array pitch of the second prism sheet 6 is defined as Py [μm], the following relationships are satisfied:
Px≤Pp/(14−0.045Pp), and
Py≤Pp/(11.5−0.032Pp) (1)
By setting the first prism array pitch Px and the second prism array pitch Py in accordance with the pixel pitch Pp of the liquid crystal display panel 2 so as to satisfy the above expression (1), a liquid crystal display apparatus in which occurrence of a moiré pattern can be prevented without largely reducing front luminance can be obtained.
For example, when the pixel pitch Pp is 222 μm, the upper limits of Px and Py are about 55 μm and 56 μm, respectively; when the pixel pitch is 144 μm, the upper limits of Px and Py are about 19 μm and about 20 μm, respectively; and when the pixel pitch is 136.5 μm, the upper limits of Px and Py are about 17 μm and 19 μm, respectively.
Preferably, in the case of Pp≥222, Px≤50, Py≤50, and |Px−Py|<50 are satisfied; in the case of 222>Pp≥144, Px≤20, Py≤20, and |Px−Py|<20 are satisfied; and in the case of 144>Pp≥136.5, Px≤15, Py≤20, and −20<Px−Py<15 are satisfied.
Referring to
As described above, by setting the pixel pitch Pp of the liquid crystal display panel 2 and the prism array pitches Px and Py of the first and second prism sheets 5 and 6 so as to satisfy the relationships of the expression (1), the liquid crystal display apparatus 1 causing no moiré pattern can be obtained.
As shown in
Thus, according to this embodiment, the array pitches of the respective prisms 5P and 6P on the first and second prism sheets 5 and 6 are determined in accordance with the pixel pitch of the liquid crystal display panel 2 as shown in the expression (1). Accordingly, occurrence of a moiré pattern can be prevented, without largely reducing front luminance of the liquid crystal display panel.
Furthermore, since the upper limits of the prism array pitches Px and Py producing a high front luminance without causing a moiré pattern can be obtained easily according to the expression (1), the combination of the prism sheets 5 and 6 can be optimized and the degree of design flexibility can also be improved.
Next, detailed configurations of the first and second prism sheets 5 and 6 and modifications thereof will be described below.
Each of the first and second prism sheets 5 and 6 is configured to have a prism structure on one surface of a base film made of light-transmissive resin such as polyethylene terephthalate (PET) or polycarbonate (PC). The prism structure may be directly formed on the base film by a method such as casting or melt extrusion. Alternatively, a surface having the shape of the prism structure may be formed using an ultraviolet-curable resin material and then be transferred onto the surface of the base film.
In an exemplary configuration in which the prism structure is transferred onto the base film, the prism sheet can be made thinner by configuring the prism structure to be later separable from the base film. Specifically, the thickness of the prism sheet can be made thinner in the following manner, for example: the thickness of a 50-μm-pitch prism sheet becomes 50 μm, the thickness of a 19-μm-pitch prism sheet becomes 35 μm, the thickness of a 14-μm-pitch prism sheet becomes 32 μm, and the thickness of a 10-μm-pitch prism sheet becomes 30 μm.
If usability of the first and second prism sheets is expected to be degraded because of such thinning, the first and second prism sheets 5 and 6 may be bonded together with an adhesive layer 8 therebetween, as shown in
The liquid crystal display apparatus 1 having an improved front luminance can be obtained by employing two prism sheets including the first and second prism sheets 5 and 6 as shown in
In the case where a single pixel includes sub-pixels having colors of R, G, and B as in the case of a color liquid crystal display panel, the prism array pitch Px of the first prism sheet 5 having the prisms 5P arranged in the longitudinal direction (X-direction) of the screen may be set to one-third of the prism array pitch Py of the second prism sheet 6 having the prisms 6P arranged in the lateral direction (Y-direction) of the screen.
The condenser sheets according to the present invention are not limited to the above-described prism sheets 5 and 6.
Also in this example, by setting the pixel pitch Pp of the liquid crystal display panel, the prism array pitch Px of the prism sheet 5, and a lens array pitch Py of the lens sheet 9 so as to satisfy the relationships of the expression (1), the advantages of the invention can be obtained. Further, by placing the lens sheet 9 on the upper position, a liquid crystal display apparatus having a wider viewing angle can be produced. Also when the first and second condenser sheets are both lens sheets, the same advantages as those described above can be obtained.
Aoki, Makoto, Sasaki, Jun, Abiko, Toru, Kimura, Kiyohiro
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