JP2005043516A - Optical sheet, surface light source device, and transmission-type display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet for performing uniform illumination over the whole screen, even when light is introduced by using a parallel set cathode-ray tubes from the rear face, and to provide a surface light source device and a transmission-type display device. <P>SOLUTION: The optical sheet 12 is arranged between an LCD panel 11 and a light source part arranging a plurality of the cathode-ray tubes 13 in parallel. The optical sheet 12 is a both-sided lenticular lens sheet, provided with an incident-side lenticular lens part 12b provided on a side opposite to the light source part and an emission side lenticular lens part 12c provided on a side opposite to the transmission-type display part. The ridge direction of the incident-side lenticular lens part 12b and the ridge direction of the emission side lenticular lens part 12c substantially coincide, furthermore, these ridge directions also coincide with the longitudinal direction of the cathode-ray tube 13. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical sheet used for a backlight such as a liquid crystal display, a surface light source device used as a backlight, and a transmissive display device using them.
[0002]
[Prior art]
In a backlight used for a liquid crystal display or the like, light is introduced from the side by using a cathode ray tube or a cathode ray tube is arranged in parallel on the back side.
However, when light is introduced from the side, there is a problem that the intensity of light cannot be increased more than a certain degree because the number of usable cathode ray tubes is limited.
[0003]
Conventionally, when light is introduced using a parallel cathode ray tube from the back side, the distance between the cathode ray tube and the LCD panel (transmission type display unit) is increased, and a diffusion plate is used between them. Illumination light emitted from the LCD panel can uniformly illuminate the LCD panel.
However, when light is introduced from the back side, in order to suppress unevenness of the light intensity between the gap portion of the cathode ray tube and immediately below, or in order to suppress this, the interval between the cathode ray tube and the LCD panel is largely separated. However, there has been a problem that the amount of light used can be reduced by increasing the thickness of the display, increasing diffusion to suppress unevenness, or limiting the amount of transmission.
[0004]
For these problems, for example, various methods for maintaining uniformity by providing a light-shielding portion as in Patent Document 1 and Patent Document 2 have been proposed.
Further, for example, Patent Document 3 proposes a method using a sheet provided with lenticular lenses on both sides.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 05-119703 [Patent Document 2]
Japanese Patent Laid-Open No. 11-242219 [Patent Document 3]
Japanese Patent Laid-Open No. 06-347613
[Problems to be solved by the invention]
However, the methods described in Patent Documents 1 and 2 have a problem in that the light utilization rate decreases because the light shielding portion is provided.
The method described in Patent Document 3 is a configuration for performing diffusion control in two directions, and has no function of correcting the optical axis. Therefore, if the optical axis varies depending on the position of the LCD due to the positional relationship with the cathode ray tube, there is a problem that brightness spots occur at each position of the screen depending on the position where the screen is observed.
[0007]
An object of the present invention is to provide an optical sheet, a surface light source device, and a transmissive display device that can perform uniform illumination over the entire screen even when light is introduced from the back using a parallel cathode ray tube. It is to be.
[0008]
[Means for Solving the Problems]
The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this. In other words, the invention of claim 1 is an optical sheet (12) provided between a transmissive display unit (11) and a light source unit in which a plurality of line light sources (13) are arranged in parallel. An incident-side lenticular lens portion (12b) provided on the opposite side, and an emission-side lenticular lens portion (12c) provided on the side facing the transmissive display portion. The optical sheet is characterized in that a ridge line direction and a ridge line direction of the emission side lenticular lens portion substantially coincide with each other.
[0009]
According to a second aspect of the invention, in the optical sheet of the first aspect, when combined with the light source unit, the ridge line directions of the incident side lenticular lens unit (12b) and the emission side lenticular lens unit (12c) are The optical sheet (12) is characterized in that it substantially coincides with the longitudinal direction of the plurality of line light sources (13).
[0010]
According to a third aspect of the present invention, in the optical sheet according to the first or second aspect, the shape of the incident side lenticular lens portion (12b) and / or the emission side lenticular lens portion (12c) is the same as that of the light source portion. The optical sheet (12) is characterized by being different depending on the distance to the line light source (13) when combined.
[0011]
According to a fourth aspect of the present invention, there is provided the optical sheet according to any one of the first to third aspects, wherein the incident side lenticular lens portion (12b) and the emission side lenticular lens portion (12c) are provided. Is an optical sheet (12) characterized in that a base material layer (12a) is provided.
[0012]
The invention of claim 5 is a surface light source device for projecting illumination light from the back side of the transmissive display unit (11), wherein a plurality of linear light sources (13) are arranged in parallel, and the light source unit An optical sheet (12) provided on the exit side of the light source, and the optical sheet is disposed on the exit side of the light source unit and on the side facing the light source unit (incident side lenticular lens unit ( 12b) and an exit-side lenticular lens portion (12c) provided on the side facing the transmissive display portion, and a ridgeline direction of the entrance-side lenticular lens portion and a ridgeline direction of the exit-side lenticular lens portion Are surface light source devices (12, 13) characterized by substantially matching.
[0013]
The invention of claim 6 is the surface light source device according to claim 5, wherein the ridge line direction of the incident side lenticular lens portion (12 b) and the emission side lenticular lens portion (12 c) is the plurality of line light sources (13). The surface light source device (12, 13) is characterized in that it substantially coincides with the longitudinal direction.
[0014]
A seventh aspect of the present invention is the surface light source device according to the fifth or sixth aspect, wherein the shape of the incident side lenticular lens portion (12b) and / or the emission side lenticular lens portion (12c) is the linear light source. The surface light source device (12, 13) is characterized by being different depending on the distance to (13).
[0015]
The surface light source device according to claim 8 is the surface light source device according to any one of claims 5 to 7, wherein the line light source (13) is a cathode ray tube. 12, 13).
[0016]
A ninth aspect of the present invention is the surface light source device according to any one of the fifth to eighth aspects, wherein the incident side lenticular lens portion (12b) and the emission side lenticular lens portion (12c) are arranged. Is a surface light source device (12, 13) characterized in that a base material layer (12a) is provided.
[0017]
The invention of claim 10 includes a transmissive display section (11), a light source section in which a plurality of line light sources (13) are arranged in parallel, and an optical sheet (between the transmissive display section and the light source section). 12), wherein the optical sheet is provided on the exit side of the light source unit and on the side facing the light source unit, and an incident side lenticular lens unit (12b). And an exit side lenticular lens portion (12c) provided on the side facing the transmission type display portion, and the ridge line direction of the entrance side lenticular lens portion and the ridge line direction of the exit side lenticular lens portion are approximately The transmission type display device (10) is characterized by being coincident.
[0018]
According to an eleventh aspect of the present invention, in the transmissive display device according to the tenth aspect, the ridge line direction of the incident side lenticular lens portion (12b) and the emission side lenticular lens portion (12c) is a longitudinal direction of the plurality of line light sources. A transmissive display device (10) characterized in that it substantially coincides with the direction.
[0019]
According to a twelfth aspect of the present invention, in the transmissive display device according to the tenth or eleventh aspect, the shape of the incident side lenticular lens portion (12b) and / or the emission side lenticular lens portion (12c) is the line. The transmissive display device (10) is characterized by being different depending on the distance to the light source (13).
[0020]
The invention of claim 13 is the transmission type display device according to any one of claims 10 to 12, wherein the line light source (13) is a cathode ray tube. Device (10).
[0021]
The invention of claim 14 is the transmissive display device according to any one of claims 10 to 13, wherein the incident side lenticular lens portion (12b) and the emission side lenticular lens portion (12c) are provided. A transmissive display device (10) is characterized in that a base material layer (12a) is provided therebetween.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.
FIG. 1 is a diagram showing an embodiment of a transmissive display device according to the present invention. In addition, each figure shown below including FIG. 1 is the figure shown typically, and the magnitude | size and shape of each part are exaggerated suitably for easy understanding.
The transmissive display device 10 according to the present embodiment includes an LCD panel 11, an optical sheet 12, a cathode ray tube 13, and the like. An image formed on the LCD panel 11 is displayed from the back by a surface light source device including the optical sheet 12 and the cathode ray tube 13. A transmissive liquid crystal display device for illumination.
The LCD panel 11 is a so-called transmissive liquid crystal display element, which is 30 inches in size and has a resolution of SVGA.
The cathode ray tube 13 is a line light source that forms a light source unit of a backlight. In this embodiment, six cathode ray tubes 13 are arranged in parallel at regular intervals of about 75 mm.
The distance between the cathode ray tube 13 and the optical sheet 12 is 50 mm.
[0023]
The optical sheet 12 is provided between the cathode ray tube 13 and the LCD panel 11, corrects the optical axis so that illumination light emitted from the cathode ray tube 13 is emitted substantially perpendicularly to the LCD panel 11, and It is a sheet provided so as to have a uniform illuminance distribution regardless of the position.
The transmissive display device according to this embodiment has the above-described configuration and a thickness of 100 mm.
[0024]
FIG. 2 is a diagram showing the optical sheet 12. FIG. 2A shows the entire optical sheet 12, and FIG. 2B is a cross-sectional view taken along the line AA 'shown in FIG. The optical sheet 12 in the present embodiment includes a base sheet 12a, an incident side lenticular lens portion 12b, and an emission side lenticular lens portion 12c.
The base material sheet 12a is a transparent base material formed in a sheet shape having a thickness of about 1 to 3 mm. The base sheet 12a is formed of, for example, an acrylic resin, polystyrene, polycarbonate, epoxy resin, or the like.
[0025]
The incident side lenticular lens portion 12b and the emission side lenticular lens portion 12c have a unit lens whose cross section is a part of an ellipse, and is formed of, for example, acrylic resin, polystyrene, polycarbonate, epoxy resin, or the like.
In the present embodiment, the entrance side lenticular lens portion 12b and the exit side lenticular lens portion 12c are arranged such that unit lenses are arranged substantially in parallel at a pitch P = 0.3 mm.
[0026]
Here, the lens pitch P of the incident-side lenticular lens portion 12b and the emission-side lenticular lens portion 12c is either of the following in relation to the matrix image video pitch D in order to prevent moire from the matrix image of the LCD panel 11 or the like. It is advisable to determine that these conditions are met. That is, condition 1: (D / P) = 2 / (2n + 1) or (D / P) = (2n + 1) / 2 (where n is a non-negative integer). Condition 2: (D / P)> 3.5 or (P / D)> 3.5, more preferably (D / P)> 4.5 or (P / D)> 4.5 The lens pitch P may be determined so as to satisfy any of the following.
[0027]
In addition, the exit side lenticular lens portion 12c in the present embodiment is provided in the vicinity of the focal position of the entrance side lenticular lens portion 12b (see FIG. 5).
Furthermore, in the present embodiment, the direction of the ridge line substantially coincides.
Further, these ridge line directions substantially coincide with the longitudinal direction of the cathode ray tube 13.
[0028]
(Manufacturing method of the optical sheet 12)
Here, the manufacturing method of the optical sheet 12 in this embodiment is demonstrated.
In this embodiment, the optical sheet 12 is manufactured by a so-called 2P method using an ultraviolet curable resin for forming the incident side lenticular lens portion 12b and the emission side lenticular lens portion 12c.
First, an ultraviolet curable resin is filled by a roll coating method, a gravure method, a dispenser method, a die coating method, or the like into a mold corresponding to the shape of the incident side lenticular lens portion 12b and the emission side lenticular lens portion 12c. After the mold is filled with the ultraviolet curable resin, a base sheet is laminated on the ultraviolet curable resin filled in the mold and is pressed by a pressure roller so that the ultraviolet curable resin and the base sheet are brought into close contact with each other. When the ultraviolet curable resin and the base sheet are brought into close contact with each other, the ultraviolet curable resin is irradiated with ultraviolet rays from the base sheet to cure the ultraviolet curable resin. Finally, the cured ultraviolet curable resin is released from the mold. The optical sheet 12 is completed by performing this operation on both sides.
The optical sheet 12 manufactured in this way is cut into a predetermined size as necessary and used as an optical sheet 12 for a backlight.
[0029]
The production of the optical sheet 12 is not limited to the 2P method using the ultraviolet curable resin described above, and corresponds to the optical sheet 12 using a resin material such as acrylic resin, polystyrene, polycarbonate, epoxy resin, or the like. A method of filling a mold with a resin material in a monomer state, polymerizing and curing, and then releasing the mold (casting method), or a method of releasing a mold after filling a similar resin mold with a heated resin material and pressurizing ( It can be manufactured by a hot press method).
[0030]
FIG. 3 is a diagram for explaining how the optical sheet 12 works in the transmissive display device of the present embodiment. FIG. 3 shows a cross section similar to that of FIG.
In the cross section shown in FIG. 3, the illumination light emitted from the cathode ray tube 13 spreads in all directions around the cathode ray tube 13 and enters the optical sheet 12 at various angles. Illumination light that is incident on the optical sheet 12 at a relatively small incident angle is refracted by the incident-side lenticular lens unit 12b and the emission-side lenticular lens unit 12c, and enters the LCD panel 11 substantially perpendicularly. The light is emitted from the optical sheet 12.
[0031]
Illumination light incident on the optical sheet 12 at a relatively large incident angle is refracted when it enters the incident-side lenticular lens unit 12b and exceeds the critical angle when it reaches the output-side lenticular lens unit 12c. Because it is totally reflected. This total reflection is repeated several times in the optical sheet 12, and light is emitted from the optical sheet 12 when the critical angle is not exceeded. Therefore, even if the illumination light is incident on the optical sheet 12 from the cathode ray tube 13 at a relatively large incident angle, the incident light is incident on the LCD panel 11 with a small incident angle (nearly perpendicular). Become.
As described above, since the optical axis of the illumination light is corrected by the optical sheet 12, in the transmission type display device according to this embodiment, the luminance difference of the display image depending on the location is within 10%, and the luminance unevenness can be confirmed practically. The brightness is uniform.
[0032]
(Comparative example)
In order to confirm the effect of the optical sheet 12 in the present embodiment, the following transmissive display device was created.
FIG. 4 is a diagram showing a transmissive display device created as a comparative example. FIG. 4 shows the same as FIG.
In the comparative example shown in FIG. 4, the LCD panel 11 having the same 30-inch size and SVGA resolution as the above-described embodiment is used. Further, the cathode ray tube 13 is the same as that in the above-described embodiment, and six cathode ray tubes 13 are arranged on the back surface of the LCD at approximately 75 mm intervals and substantially in parallel with each other. In the comparative example shown in FIG. 4, a diffusion plate 14 is arranged between the LCD panel 11 and the cathode ray tube 13. The distance between the diffusion plate 14 and the cathode ray tube 13 is 70 mm. This interval is such that the difference in luminance of the illumination light is minimized depending on the position on the LCD panel 11.
The transmission type display device in this comparative example has the above-described configuration, and its thickness is 120 mm.
[0033]
When the transmissive display device of the completed comparative example was operated and observed, the luminance difference of the display image depending on the location was 50% at maximum in this comparative example.
Further, in this comparative example, the luminance unevenness when observed from the front can be corrected, but when the viewpoint is moved, the luminance unevenness corresponding to the position of the cathode ray tube has been confirmed.
Further, the transmittance decrease due to the diffusion plate 14 is approximately 20%, and further the transmittance decrease due to the diffusion of the incident light to the LCD panel 11 occurs 30% compared to the above-described embodiment.
[0034]
As described above, in the transmissive display device of the comparative example, although the thickness of the device is increased, the brightness difference of the display image is large, uneven, and the transmittance is low, so that the brightness is low. Compared with the transmissive display device of the embodiment of the present invention, it was clearly inferior in all aspects.
[0035]
According to this embodiment, since the optical sheet 12 that is a double-sided lenticular lens is inserted into the gap between the cathode ray tube 13 and the LCD panel 11, the light incident direction from the cathode ray tube 13 to the LCD panel 11 with the cathode ray tube 13 is reduced. It is possible to correct the variation due to the positional relationship and to enter the LCD panel 11 substantially perpendicularly. Therefore, it is possible to ensure a uniform direction and intensity of incident light at any position on the LCD panel 11, suppress unevenness in the intensity of the image, and suppress a loss of light amount by obtaining an appropriate diffusion characteristic. The transmittance in the panel 11 can also be increased.
[0036]
As described above, the transmissive display device configured as described above causes the illumination light from the cathode ray tube 13 to be emitted so that the incident angle to the LCD panel 11 is substantially vertical by the action of the optical sheet 12, so that the observation is performed. A person can observe the image on the LCD panel 11 with high brightness and without unevenness.
[0037]
In the present embodiment, since the optical sheet 12 is formed with the incident side lenticular lens portion 12b and the emission side lenticular lens portion 12c on both surfaces of the base sheet 12a with an ultraviolet curable resin, the optical sheet 12 can be easily manufactured. can do.
[0038]
(Deformation)
The present invention is not limited to the embodiment described above, and various modifications and changes are possible, and these are also within the equivalent scope of the present invention.
For example, in the present embodiment, the incident side lenticular lens portion 12b and the emission side lenticular lens portion 12c have the same shape, and the unit lens has the same shape at all positions. For example, the shape of the unit lens may be changed between the incident side lenticular lens portion 12b and the emission side lenticular lens portion 12c, or depending on the positional relationship with the cathode ray tube 13 (depending on the distance to the cathode ray tube 13). In response to this, the unevenness of the illuminance may be adjusted by changing the shape of the unit lens.
[0039]
【The invention's effect】
As described above in detail, according to the present invention, the following effects can be obtained.
(1) An optical sheet provided between a transmissive display unit and a light source unit in which a plurality of line light sources are arranged in parallel, an incident side lenticular lens unit provided on the side facing the light source unit, and a transmissive type An exit-side lenticular lens unit provided on the side facing the display unit, and the ridgeline direction of the entrance-side lenticular lens unit and the ridgeline direction of the exit-side lenticular lens unit are substantially coincident with each other, so that transmission from the cathode-ray tube The incident angle of illumination light to the mold display unit can be corrected substantially vertically, suppressing unevenness in the intensity of the image, suppressing the loss of light quantity by obtaining an appropriate diffusion characteristic, and also the transmittance in the transmissive display unit Can be high.
[0040]
(2) Since the ridge line directions of the incident side lenticular lens unit and the emission side lenticular lens unit substantially coincide with the longitudinal directions of the plurality of line light sources, the optical axis of the illumination light can be corrected more accurately.
[0041]
(3) Since the shape of the entrance-side lenticular lens part and / or the exit-side lenticular lens part varies depending on the distance to the line light source when combined with the light source part, even if the number of line light sources is small The optical axis of the illumination light can be corrected with high accuracy, and uniform illumination light can be obtained.
[0042]
(4) Since the base material layer is provided between the incident side lenticular lens portion and the emission side lenticular lens portion, the optical sheet can be easily manufactured.
[0043]
(5) Since the line light source is a cathode ray tube, the surface light source device and the transmissive display device can be manufactured at low cost.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a transmissive display device according to the present invention.
FIG. 2 is a view showing an optical sheet 12;
FIG. 3 is a diagram for explaining how the optical sheet 12 works in the transmissive display device of the present embodiment.
FIG. 4 is a diagram showing a transmissive display device created as a comparative example.
FIG. 5 is a diagram illustrating a positional relationship between an incident side lenticular lens unit and an output side lenticular lens unit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Transmission type display apparatus 11 LCD panel 12 Optical sheet 12a Base material sheet 12b Incident side lenticular lens part 12c Outgoing side lenticular lens part 13 Cathode ray tube 14 Diffusion plate

Claims (14)

An optical sheet provided between a transmissive display unit and a light source unit in which a plurality of line light sources are arranged in parallel,
An incident side lenticular lens provided on the side facing the light source;
An emission side lenticular lens portion provided on the side facing the transmissive display portion,
The ridge line direction of the said incident side lenticular lens part and the ridge line direction of the said output side lenticular lens part substantially correspond, The optical sheet characterized by the above-mentioned. The optical sheet according to claim 1,
When combined with the light source unit, the ridge line direction of the incident side lenticular lens unit and the emission side lenticular lens unit substantially coincides with the longitudinal direction of the plurality of line light sources. . In the optical sheet according to claim 1 or 2,
The optical sheet, wherein the shape of the incident side lenticular lens part and / or the emission side lenticular lens part varies depending on the distance to the line light source when combined with the light source part. In the optical sheet according to any one of claims 1 to 3,
An optical sheet, wherein a base material layer is provided between the incident side lenticular lens portion and the emission side lenticular lens portion. A surface light source device that projects illumination light from the back side of a transmissive display unit,
A light source unit in which a plurality of line light sources are arranged in parallel;
An optical sheet provided on the emission side from the light source unit, and
The optical sheet is an incident side lenticular lens portion provided on a side opposite to the light source portion on the emission side from the light source portion, and
An emission side lenticular lens part provided on the side facing the transmission type display part,
A surface light source device, wherein a ridgeline direction of the incident-side lenticular lens portion and a ridgeline direction of the emission-side lenticular lens portion substantially coincide with each other. The surface light source device according to claim 5,
2. A surface light source device according to claim 1, wherein a ridge line direction of the incident side lenticular lens portion and the emission side lenticular lens portion substantially coincides with a longitudinal direction of the plurality of line light sources. In the surface light source device according to claim 5 or 6,
2. The surface light source device according to claim 1, wherein the shape of the incident side lenticular lens portion and / or the emission side lenticular lens portion varies depending on a distance to the line light source. In the surface light source device according to any one of claims 5 to 7,
A surface light source device, wherein the line light source is a cathode ray tube. In the surface light source device according to any one of claims 5 to 8,
A surface light source device, wherein a base material layer is provided between the incident side lenticular lens portion and the emission side lenticular lens portion. A transmissive display;
A light source unit in which a plurality of line light sources are arranged in parallel;
An optical sheet provided between the transmissive display unit and the light source unit;
A transmissive display device comprising:
The optical sheet is an incident side lenticular lens portion provided on a side opposite to the light source portion on the emission side from the light source portion, and
An emission side lenticular lens part provided on the side facing the transmission type display part,
A transmissive display device, wherein a ridge line direction of the incident-side lenticular lens part and a ridge line direction of the emission-side lenticular lens part substantially coincide with each other. The transmissive display device according to claim 10,
A transmissive display device, wherein ridge line directions of the incident side lenticular lens part and the emission side lenticular lens part substantially coincide with longitudinal directions of the plurality of line light sources. The transmissive display device according to claim 10 or 11,
The transmission type display device, wherein the shape of the incident side lenticular lens portion and / or the emission side lenticular lens portion varies depending on the distance to the line light source. The transmissive display device according to any one of claims 10 to 12,
The transmission type display device, wherein the line light source is a cathode ray tube. The transmissive display device according to any one of claims 10 to 13,
A transmissive display device, wherein a base material layer is provided between the incident side lenticular lens portion and the emission side lenticular lens portion.

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