JP4477712B2 - Optical sheet for backlight unit and backlight unit using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical sheet incorporated in a backlight unit of a liquid crystal display device and a backlight unit using the same.
[0002]
[Prior art]
In the liquid crystal display device, a backlight system in which a liquid crystal layer is illuminated from the back surface is widely used, and a backlight unit is provided on the lower surface side of the liquid crystal layer. As shown in FIG. 3, the backlight unit 20 generally includes a rod-shaped lamp 21 as a light source and a plurality of stacked optical sheets 22. Each of the optical sheets 22 has specific optical properties such as refraction and diffusion. Specifically, the optical sheet 22 has a rectangular plate-like light guide plate 23 and a light guide plate that are arranged so that the ends thereof are along the lamp 21. The light diffusion sheet 24 disposed on the front surface side of the light source 23, the prism sheet 25 disposed on the front surface side of the light diffusion sheet 24, and the like.
[0003]
The function of the backlight unit 20 will be described. First, a light beam incident on the light guide plate 23 from the lamp 21 is reflected by a reflection dot or a reflection sheet (not shown) on the back surface of the light guide plate 23 and each side surface. Emitted from the surface. The light beam emitted from the light guide plate 23 enters the light diffusion sheet 24, is diffused, and is emitted from the surface of the light diffusion sheet 24. Thereafter, the light beam emitted from the light diffusion sheet 24 is incident on the prism sheet 25 and is emitted as a distribution light beam having a peak in a substantially upward direction by the prism portion 25a formed on the surface of the prism sheet 25. As described above, the light emitted from the lamp 21 is diffused by the light diffusion sheet 24 and refracted by the prism sheet 25 so as to show a peak in a substantially directly upward direction. Illuminate.
[0004]
Although not shown, there is also a backlight unit in which a light diffusion sheet and a prism sheet are further provided as the optical sheet 22 in consideration of the light collecting characteristics of the prism sheet 24 and the like.
[0005]
[Problems to be solved by the invention]
In the backlight unit 20 using the above-described conventional optical sheet 22, no matter how the various optical properties of the light diffusion sheet 24 and the prism sheet 25 constituting the optical sheet 22 are improved, the backlight unit 20 emits light from the lamp 21. The visible light that is uniformly dispersed and emitted substantially vertically is limited, and the improvement of the luminance of the liquid crystal display device is limited by the amount of visible light emitted from the lamp 21.
[0006]
On the other hand, portable electronic devices such as notebook personal computers that use liquid crystal display devices have limited power consumption in order to enable long-term use, and the increase in the amount of light emitted from the lamp 21 is also limited based on the power consumption. There is.
[0007]
The present invention has been made in view of these disadvantages, and an optical sheet for a backlight unit capable of improving the luminance of a liquid crystal display device without increasing the power consumption of the backlight unit, and a backlight using the same. The purpose is to provide units.
[0008]
[Means for Solving the Problems]
The invention made to solve the above-mentioned problems is an optical sheet equipped in a backlight unit of a liquid crystal display device, and has a wavelength conversion function for converting light having a wavelength other than visible wavelengths into visible light, The expression of the wavelength conversion function is due to the dispersion of powdered optical glass containing the wavelength conversion substance, the optical sheet is a light diffusion sheet, the resin sheet is dispersed in the binder An optical sheet for a backlight unit comprising a sticking prevention layer on the back surface, wherein the optical glass is dispersed in the binder of the sticking prevention layer.
[0009]
This optical sheet for a backlight unit can convert a light ray other than a visible wavelength such as an ultraviolet ray into a visible light ray by a wavelength conversion function.
[0010]
Therefore, according to the backlight unit equipped with the optical sheet, light rays other than visible light rays emitted from the lamp can be converted into visible light rays by the optical sheet, and as a result, the light amount of the lamp is not increased. However, the brightness of the liquid crystal display device using the backlight unit can be improved by the amount of converted visible light. Therefore, it is not necessary to increase the power consumption for improving the brightness of the liquid crystal display device as in the case of the conventional backlight unit, and the portable electronic device such as a notebook personal computer or a mobile phone using the backlight unit is used for a long time. Is possible.
[0011]
In order to express the wavelength conversion function, powdery optical glass containing a wavelength conversion substance is dispersed. Here, the “wavelength converting substance” means a substance that converts light rays other than visible wavelengths into visible rays. Glass is preferable as a medium for stably dispersing various substances, and easily imparts optical properties such as refraction and diffusion. Therefore, optical glasses having various optical properties have been developed. The wavelength conversion function according to the present invention is also easily developed according to the optical glass, and can exhibit a high wavelength conversion function.
[0012]
In order to develop the wavelength conversion function, it is also possible to directly disperse the wavelength conversion substance in the resin constituting the optical sheet. By this means, as in the case of using the optical glass as described above, it is possible to convert rays other than visible wavelengths such as ultraviolet rays into visible rays, and the luminance of the liquid crystal display device using the backlight unit can be increased. Can be improved. Moreover, since the said optical glass etc. are not required, the simplification of the manufacturing process of the said optical sheet can be achieved.
[0013]
The optical sheet equipped with the wavelength conversion function is a light diffusion sheet, and optical glass is dispersed in a binder of an anti-sticking layer provided on the back surface of the light diffusion sheet. In the backlight unit, the light diffusion sheet is located in a lower layer. Therefore, according to this means, the light emitted from the lamp can be converted into visible light at an initial stage. Therefore, the optical functions of the optical sheet such as the light diffusion sheet and the lens sheet in the backlight unit can be effectively designed according to the visible light.
[0014]
It is preferable to use a wavelength conversion function that converts light other than the visible wavelength into ultraviolet light and converts the ultraviolet light into visible light. The conversion from ultraviolet light to visible light is a down conversion from short wavelength to long wavelength, and is a conversion in the direction of lowering photon energy. The improvement can be great.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. FIG. 1 is a schematic cross-sectional view showing an optical sheet for a backlight unit according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view showing an optical sheet according to a different form from the optical sheet of FIG.
[0016]
The optical sheet 1 in FIG. 1 is a so-called prism sheet, lens sheet, or the like, and has a specific structure including a sheet portion 2 and a plurality of prisms formed in parallel and adjacent to the surface of the sheet portion 2. Part 3. Due to the prism portion 3, the optical sheet 1 has an optical property of refracting the peak direction of the light beam emitted from the light guide plate from obliquely upward to substantially directly above.
[0017]
The optical sheet 1 contains powdered optical glass 5 dispersed in a base 4 formed from a synthetic resin. This optical glass 5 has a wavelength conversion function of converting light having a wavelength other than visible light to visible light by containing a wavelength converting substance that converts light having a wavelength other than visible wavelengths into visible light. is there. Examples of such wavelength converting substances include rare earth ions that become fluorescently active ions by receiving light having a wavelength other than the visible wavelength. In addition, as light rays having wavelengths other than the visible wavelength, ultraviolet rays, infrared rays, and the like are applicable, and it is preferable to convert ultraviolet rays into visible rays in consideration of photon energy loss.
[0018]
The synthetic resin forming the base 4 of the optical sheet 1 is transparent and preferably colorless and transparent because it is necessary to transmit light, and the material is not particularly limited. For example, polyethylene terephthalate, polyethylene Naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, weather resistant vinyl chloride and the like can be mentioned.
[0019]
A backlight unit in which a light guide plate 23, a light diffusion sheet 24, and a prism sheet 25 as shown in FIG. 3 are laminated, and the light emitted from the lamp 21 is uniformly diffused and sent to an upper deflection film (not shown) or the like. 20, when the optical sheet 1 is used as the prism sheet 25, it is possible to convert light having a wavelength other than the visible wavelength out of the light emitted from the lamp 21 by the optical sheet 1, and as a result, the backlight. The luminance of the liquid crystal display device including the unit 20 can be improved.
[0020]
The optical sheet 6 in FIG. 2 is a so-called light diffusion sheet, and has an optical property of uniformly dispersing transmitted light. Specifically, the optical sheet 6 includes a base material layer 7, a light diffusion layer 8 laminated on the front side of the base material layer 7, and a sticking prevention layer 9 laminated on the back surface of the base material layer 7. It is configured.
[0021]
Since the base material layer 7 needs to transmit light, it is made of a synthetic resin that is transparent, particularly colorless and transparent. The synthetic resin used for the base material layer 7 is not particularly limited, and examples thereof include polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, and weather resistant vinyl chloride. .
[0022]
The light diffusion layer 8 is composed of a binder 10 and resin beads 11 dispersed in the binder 10. By dispersing the resin beads 11 in this way, the light beam that passes through the light diffusion layer 8 can be uniformly diffused. Further, by providing a resin bead 11 whose upper end protrudes from the binder 10 or is embedded in the binder 10, the light beam can be diffused better.
[0023]
Examples of the polymer used for the binder 10 include acrylic resin, polyurethane, polyester, fluorine resin, silicone resin, polyamideimide, and epoxy resin. In addition to the above-mentioned polymer, the binder 10 may contain, for example, a plasticizer, a stabilizer, a deterioration inhibitor, a dispersant, and the like. Since the binder 10 needs to transmit light, it is transparent, and colorless and transparent is particularly preferable.
[0024]
The resin beads 11 are substantially spherical, and examples of the material thereof include acrylic resin, polyurethane, polyvinyl chloride, polystyrene, polyacrylonitrile, and polyamide. The resin beads 11 are preferably transparent in order to increase the amount of transmitted light, and particularly preferably colorless and transparent.
[0025]
The anti-sticking layer 9 is composed of a binder 12 and resin beads 13 dispersed in the binder 12. The materials of the binder 12 and the resin beads 13 are the same as those used for the light diffusion layer 8. Since the anti-sticking layer 9 is intended to prevent sticking with the light guide plate (see FIG. 2), the blending amount of the resin beads 13 is relatively small. Dispersed in.
[0026]
Like the optical sheet 1, a powdery optical glass 14 is dispersed inside the binder 12. With the anti-sticking layer 9 containing the optical glass 14 in a dispersed manner, the optical sheet 6 exhibits a wavelength conversion function for converting light having a wavelength other than visible light to visible light. Therefore, by using the optical sheet 6 as the light diffusion sheet of the backlight unit, the amount of visible light transmitted to the liquid crystal surface can be increased, and as a result, the brightness of the liquid crystal display device can be increased without increasing the power consumption. Can be improved.
[0027]
In addition, the optical sheet of this invention is not limited to the said embodiment, For example, it is also possible to provide a wavelength conversion function in a light-guide plate. In the optical sheet 6 as the light diffusion sheet, optical glass may be dispersed in the binder 10 or the base material layer 7 of the light diffusion layer 8.
[0028]
【The invention's effect】
As described above, according to the optical sheet for a backlight unit of the present invention and the backlight unit using the same, the light emitted from the lamp has a wavelength other than the visible wavelength such as ultraviolet rays and infrared rays not related to the luminance. Therefore, the luminance of the liquid crystal display device can be improved by the amount of the converted visible light.
[0029]
Further, since the luminance of the liquid crystal display device is improved, the power consumption of the liquid crystal display device is reduced, and a portable electronic device such as a notebook personal computer in which the liquid crystal display device is used can be used for a long time.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an optical sheet for a backlight unit according to an embodiment of the present invention.
2 is a schematic cross-sectional view showing an optical sheet for a backlight unit having a form different from that of the optical sheet in FIG.
FIG. 3 is a schematic perspective view showing a general backlight unit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Optical sheet 2 Sheet | seat part 3 Prism part 4 Base 5 Optical glass 6 Optical sheet 7 Base material layer 8 Light-diffusion layer 9 Sticking prevention layer 10 Binder 11 Resin bead 12 Binder 13 Resin bead 14 Optical glass

Claims (3)

It is an optical sheet equipped in a backlight unit of a liquid crystal display device, and has a wavelength conversion function for converting light having a wavelength other than visible wavelengths into visible light,
The expression of the wavelength conversion function is due to the dispersion of powdered optical glass containing a wavelength conversion substance ,
The optical sheet is a light diffusion sheet, this light diffusion sheet is provided with a sticking prevention layer in which resin beads are dispersed in a binder on the back surface,
An optical sheet for a backlight unit , wherein the optical glass is dispersed in the binder of the anti-sticking layer . The optical sheet for a backlight unit according to claim 1 , wherein the light rays other than the visible wavelength are ultraviolet rays. The backlight unit for liquid crystal display devices provided with the lamp | ramp and the optical sheet of Claim 1 or 2 which guide | induces uniformly the light ray emitted from this lamp | ramp to a front side direction.

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