JP2000193805A - Manufacture of light diffusive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light diffusive sheet and a manufacturing method for the sheet having reduced processes and obtain a uniform light diffusion without using spherical beads, and a back light unit using the sheet. SOLUTION: A light diffusive sheet is integrally provided with a plurality of lens parts whose surfaces are curved like a lens (spherically recessed parts 4). A method for producing a light diffusive sheet comprises a laminating process for laminating a transparent resin (an ultraviolet-curing resin) prior to curing on a surface of a transparent substrate sheet 2 using a sheet form light diffusive sheet mold 9 having a surface with a plurality of parts curved like a lens as well as operated a mold releasing treatment, a transcribing process for pressing the resin on the surface of the light diffusive sheet mold 9, a curing process for curing the resin (by ultraviolet-light irradiation) and a mold releasing process for peeling the light diffusive sheet mold 9 from the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light diffusion sheet used for a backlight unit of a liquid crystal display device, a method for manufacturing the light diffusion sheet, and a backlight unit using the light diffusion sheet.

[0002]

2. Description of the Related Art Conventionally, as a backlight unit incorporated in a liquid crystal display device, a lamp as a light source, a light guide plate disposed beside the lamp to guide light emitted from the lamp to the front side, and A light guide plate having a light diffusion sheet laminated on the front side of the light guide plate is used.

[0003] As a method of manufacturing this light diffusion sheet,
(A) There has been proposed a method of applying a binder in which beads are dispersed on the surface of a base material sheet (for example, Japanese Utility Model Application Laid-Open No. HEI-5-95).
-73602 and the like). According to this manufacturing method,
A light diffusion sheet including a light diffusion layer in which beads are dispersed in a binder and a base sheet laminated on the back surface is manufactured. As the material of the base sheet, for example, a synthetic resin such as polyethylene terephthalate, polyester, or polycarbonate is used.As the material of the beads, a resin such as acryl or glass is used. As the material of the binder, a synthetic resin such as acryl or urethane is used. A composition is used.

(B) As another manufacturing method, embossing is performed at the time of molding a synthetic resin sheet.
There is a method of forming irregularities on the surface.

[0005]

The above-mentioned conventional light diffusing sheet, the method for producing the same, and the backlight unit using the same have the following disadvantages. That is, (1) The manufacturing method by embossing of (b) requires molding with a mold or a roll, and the equipment becomes large-scale.

(2) In the manufacturing method by embossing of (b), it is difficult to form spherical irregularities on the surface exhibiting a light diffusing action, so that the light diffusion tends to be biased. Further, according to the embossing, there is a possibility that the light transmittance of the synthetic resin material to be processed is deteriorated.

(3) The production method of (a) requires many steps such as a step of dispersing beads in a binder, a step of applying a binder, and a step of drying, which requires labor and time.

The present invention has been made in view of these inconveniences, has a small number of manufacturing steps, and enables uniform diffusion of light without using spherical beads. The purpose is to provide the backlight unit used.

[0009]

According to an aspect of the present invention, there is provided a light diffusing sheet having a plurality of lens portions whose surfaces are curved like lenses. According to this means, the transmitted light can be uniformly dispersed throughout the light diffusion sheet by the plurality of lens portions formed on the surface. In addition, since a lens unit for dispersing light is integrally provided and beads are not used unlike a conventional light diffusion sheet, the number of parts can be reduced, and as a result, manufacturing efficiency can be improved. Further, since the lens portion is integrally formed, the improvement of the strength of the light diffusion sheet itself can be promoted, and the product life can be improved. When the lens portion is formed into a spherical concave portion (claim 2), the uniformity of light diffusion can be further improved.

The invention relating to a method for manufacturing a light diffusing sheet comprises: a) a laminating step of laminating an uncured transparent resin on the surface of a transparent substrate sheet; and b) curving a plurality of portions of the surface into a lens. And using a sheet-shaped light diffusion sheet mold having a surface subjected to release treatment, and pressing a resin laminated on the surface of the light diffusion sheet mold, and c) a curing step of curing the resin. And d) a releasing step of peeling the light diffusion sheet mold from the resin (claim 3). According to this means, a light diffusion sheet having a plurality of lens portions integrally formed on the above-described surface can be manufactured by a relatively simple method and a small number of steps. In other words, the method does not require a mold or a roll as in the conventional manufacturing method by embossing (b) and does not use resin beads or glass beads as in the manufacturing method in (a). Light diffusion property can be obtained.

As the light diffusion sheet type, it is preferable to use a light diffusion sheet type having a sheet-shaped base material, spherical beads dispersed on the surface of the base material, and a binder for connecting the base material and the beads ( Claim 4). According to this means, the light diffusion sheet manufactured by the conventional manufacturing method of the above (a), that is, the conventional light diffusion sheet comprising a light diffusion layer in which beads are dispersed in a binder and a base sheet laminated on the back surface thereof The same thing as a light-diffusion sheet can be used for the shaping | molding die of a light-diffusion sheet. Further, by adjusting the average particle diameter of the beads, light diffusivity can be dramatically improved.

Further, an ultraviolet curing resin can be used as the resin, and ultraviolet irradiation can be used as the curing step. According to this means, the lens portion can be formed on the surface of the light diffusion sheet by a simple and reliable method of curing the ultraviolet curable resin by irradiation of ultraviolet light.

A lamp, and a light guide plate disposed on a side of the lamp to guide light rays emitted from the lamp toward a front side;
In the backlight unit for a liquid crystal display device having the light diffusion sheet disposed on the front side of the light guide plate, the use of the light diffusion sheet of the above means (claim 6) suppresses uneven brightness of the liquid crystal display device. be able to.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings as appropriate. FIG. 1A is a partial sectional view showing a light diffusion sheet according to one embodiment of the present invention.
2B is a partial cross-sectional view illustrating a method for manufacturing the light diffusion sheet in FIG. 2A, and FIG. 2 is a schematic cross-sectional view illustrating the configuration of a backlight unit using the light diffusion sheet in FIG. is there. In FIG. 1, since the light diffusing sheet 1 is turned upside down, the front surface of the light diffusing sheet 1 indicates the lower surface of the light diffusing sheet in FIG. 1, and conversely, the rear surface indicates the upper surface.

The light diffusion sheet 1 shown in FIG.
And a light diffusion layer 3 laminated on the surface of the base sheet 2. The base sheet 2 is made of, for example, a synthetic resin such as polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, and weather-resistant vinyl chloride. The base sheet 2 is transparent because it is necessary to transmit light, and is preferably colorless and transparent. Further, the thickness of the base sheet 2 is not particularly limited.
0 micrometer or less. If the thickness of the base sheet 2 is less than the above range, curling may easily occur when the resin composition for forming the light diffusion layer 3 is applied, and conversely, If the thickness of the sheet 2 exceeds the above range, the brightness of the liquid crystal display device is reduced, and the thickness of the backlight unit 5 is increased, which is against the demand for thinning the liquid crystal display device.

The light diffusion layer 3 is made of an ultraviolet curable resin, and has a large number of spherical concave portions 4 formed on the surface. The concave portion 4 on the surface of the light diffusion layer 3 exerts the same function as the concave lens, so that the light transmitted through the light diffusion layer 3 from the back side to the front side can be uniformly diffused to the front surface of the light diffusion sheet 1. The average thickness of the light diffusion layer 3 is not particularly limited, but is, for example, about 10 μm or more and 30 μm or less. Further, the ultraviolet curable resin used for the light diffusion layer 3 is not particularly limited,
For example, a) radical polymerizable resins such as epoxy acrylate, urethane acrylate, and melamine acrylate;
b) photoaddition polymerization type polythiol / polyene resin;
c) Photocationically polymerizable resins and the like. The light diffusion layer 3 is also transparent because it is necessary to transmit light, and is preferably colorless and transparent.

In the light diffusion sheet 1, the back surface of the base sheet 2 is smooth, but the back surface may be subjected to, for example, embossing to improve the light diffusion performance and the anti-sticking performance.

As shown in FIG. 2, a backlight unit 5 incorporating the light diffusing sheet 1 shown in FIG. 1A has a lamp 6 as a light source, and a lamp disposed beside the lamp 6. The light guide plate 7 is provided with a light guide plate 7 for guiding light rays emitted from the light guide plate 6 toward the front side, and the light diffusion sheet 1 laminated on the front side of the light guide plate 7. In FIG. 2, the light guide plate 7 and the light diffusion sheet 1 are illustrated as being separated for convenience of explanation, but the front side surface of the light guide plate 7 and the back side surface of the light diffusion sheet 1 are actually in contact.

The locus of the light beam 8 in the backlight unit 5 will be described. First, the light beam 8 is emitted from the lamp 6 and guided into the light guide plate 7. Next, the light beam 8 in the light guide plate 7 is reflected by a reflection dot or a reflection sheet (not shown) on the back side of the light guide plate 7 and emitted to the light diffusion sheet 1 above. The light beam 8 emitted upward passes through the concave portion 4 formed on the surface of the light diffusion sheet 1, and at this time, the concave portion 4 acts like a lens and is refracted in various directions at each incident point. Therefore, the light rays 8 are uniformly diffused throughout the light diffusion sheet 1. Therefore, in the backlight unit 5, the light uniformly diffused throughout the light diffusion sheet 1 is sent to a further upper deflecting film (not shown) or the like at an equal density, thereby suppressing luminance unevenness on the screen of the liquid crystal display device. be able to.

Next, a method of manufacturing the light diffusion sheet 1 shown in FIG. 1A will be described. The manufacturing method includes a lamination step, a transfer step, a curing step, and a release step in this order. This laminating step is a step of laminating an uncured stage ultraviolet curable resin on the surface of the base sheet 2 to form the resin layer 3. In the transfer step, as shown in FIG. 1B, the resin layer 3 on the surface of the base sheet 2 obtained in the laminating step is pressed against the surface of the light diffusion sheet mold 9 to change the surface shape of the light diffusion sheet mold 9 to resin. This is a step of transferring to the layer 3. The curing step is a step of irradiating ultraviolet rays while the resin layer 3 is pressed against the light diffusion sheet mold 9 in the transfer step, to cure the resin layer 3. The last release step is a step of peeling the light diffusion sheet mold 9 from the cured resin layer 3. The light diffusion sheet 1 described above can be manufactured through the above manufacturing steps.

Light diffusion sheet mold 9 used in the above manufacturing method
Is composed of a sheet-shaped base material 10, spherical beads 11 dispersed on the surface of the base material 10, and a binder 12 for connecting the beads 11 on the base material 10. For this reason, the light diffusion sheet mold 9 is spherically curved at a plurality of positions on the surface by the beads 11. The spherical protrusions are transferred, and a plurality of spherical concave portions 4 are formed on the surface of the resin layer 3 as described above. The light diffusion sheet mold 9 is subjected to a release treatment on the surface thereof, thereby facilitating the work of peeling the resin layer 3 in the release step.

The light diffusion sheet mold 9 can be manufactured by the same method as the above-described conventional method (a) for manufacturing a light diffusion sheet. That is, it can be manufactured by a method of applying a binder 12 in which beads 11 are dispersed on the surface of the base material 10. As a material of the base material 10, a synthetic resin such as polyethylene terephthalate, polyester, or polycarbonate is used as in the case of the base material sheet 1.
As a material of the beads 11, a resin such as acryl or glass is used similarly to the beads used in the conventional light diffusion sheet. As the binder 12, acryl, urethane, or the like is used in the same manner as the binder used for the conventional light diffusion sheet.

The present invention is not limited to the above embodiment. For example, the material of the resin layer 3 may be a photo-setting resin other than an ultraviolet-setting resin such as a visible-light setting resin, a thermoplastic resin, or the like. However, the curing means in the curing step differs depending on the type of these resins. Also, the light diffusion sheet type may have a plurality of irregularities curved like a lens on the surface. For example, if the light diffusion sheet 1 of the present embodiment is used for the light diffusion sheet type, the light diffusion sheet having a spherical convex portion may be used. Sheets can be manufactured.

[0024]

As described above, according to the method for manufacturing a light diffusing sheet of the present invention, (1) since a mold and a roll are not required unlike the conventional manufacturing method by embossing, the manufacturing efficiency is improved. Can be improved. Further, a light diffusion sheet having high light diffusivity can be manufactured without using resin beads, glass beads, or the like as in the conventional manufacturing method using beads.

(2) By using a photocurable resin and transferring the surface shape of one light diffusion sheet using conventional beads, light having the same level of light diffusion as the conventional light diffusion sheet is obtained. Many diffusion sheets can be manufactured.

(3) By changing the refractive index of the ultraviolet-curable resin used or arbitrarily adjusting the surface shape of the light-diffusing sheet to be transferred, a light-diffusing sheet with unprecedented optical performance can be manufactured.

Therefore, when a backlight unit is manufactured using such a light diffusion sheet having an excellent light diffusion property, it is possible to obtain a backlight unit with reduced luminance unevenness on the screen of a liquid crystal display device.

[Brief description of the drawings]

1A is a partial cross-sectional view illustrating a light diffusion sheet according to an embodiment of the present invention, and FIG. 1B is a partial cross-sectional view illustrating a method for manufacturing the light diffusion sheet of FIG.

FIG. 2 is a schematic cross-sectional view illustrating a configuration of a backlight unit using the light diffusion sheet of FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light diffusion sheet 2 substrate sheet 3 light diffusion layer 4 concave portion 5 backlight unit 6 lamp 7 light guide plate 8 light beam 9 light diffusion sheet type 10 base material 11 beads 12 binder

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[Procedure amendment]

[Submission Date] March 14, 2000 (200.3.1)
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

Patent application title: Method for manufacturing light diffusion sheet

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a light diffusing sheet used for a backlight unit of a liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, as a backlight unit incorporated in a liquid crystal display device, a lamp as a light source, a light guide plate disposed beside this lamp to guide light emitted from the lamp to the front side, and A light guide plate having a light diffusion sheet laminated on the front side of the light guide plate is used.

[0003] As a method of manufacturing this light diffusion sheet,
(A) There has been proposed a method of applying a binder in which beads are dispersed on the surface of a base material sheet (for example, Japanese Utility Model Application Laid-Open No. HEI-5-95).
-73602 and the like). According to this manufacturing method,
A light diffusion sheet including a light diffusion layer in which beads are dispersed in a binder and a base sheet laminated on the back surface is manufactured. As the material of the base sheet, for example, a synthetic resin such as polyethylene terephthalate, polyester, or polycarbonate is used.As the material of the beads, a resin such as acryl or glass is used. As the material of the binder, a synthetic resin such as acryl or urethane is used. A composition is used.

(B) As another manufacturing method, embossing is performed at the time of molding a synthetic resin sheet.
There is a method of forming irregularities on the surface.

[0005]

The above-mentioned conventional method for manufacturing a light diffusion sheet has the following disadvantages. That is, (1) The manufacturing method by embossing of (b) requires molding with a mold or a roll, and the equipment becomes large-scale.

(2) In the manufacturing method by embossing of (b), it is difficult to form spherical irregularities on the surface exhibiting a light diffusing action, so that the light diffusion tends to be biased. Further, according to the embossing, there is a possibility that the light transmittance of the synthetic resin material to be processed is deteriorated.

(3) The production method of (a) requires many steps such as a step of dispersing beads in a binder, a step of applying a binder, and a step of drying, which requires labor and time.

The present invention has been made in view of these inconveniences, has a small number of manufacturing steps, and is capable of producing a light diffusing sheet capable of uniformly diffusing light without using spherical beads. An object of the present invention is to provide a method for manufacturing a sheet.

[0009]

Means for Solving the Problems The invention relating to a method for manufacturing a light diffusing sheet made to solve the above-mentioned problems is as follows: a) lamination of laminating an uncured transparent resin on the surface of a transparent base sheet. And b) using a sheet-shaped light diffusion sheet mold in which a plurality of portions of the surface are curved into a lens shape and the surface of which is subjected to a release treatment, and pressing the resin laminated on the surface of the light diffusion sheet mold. A transfer step; c) a curing step of curing the resin; and d) a release step of peeling the light diffusion sheet mold from the resin.

According to this means, a light diffusion sheet having a plurality of lens portions integrally formed on the above-described surface can be manufactured by a relatively simple method and a small number of steps. That is, it does not require a mold or a roll as in the conventional embossing method (b), and
Similar light diffusivity can be obtained without using resin beads or glass beads as in the production method (a).

As the light diffusion sheet type, it is preferable to use one having a sheet-like base material, spherical beads dispersed on the surface of the base material, and a binder for connecting the base material and the beads. According to this means, the light diffusion sheet manufactured by the conventional manufacturing method of the above (a), that is, the conventional light diffusion sheet comprising a light diffusion layer in which beads are dispersed in a binder and a base sheet laminated on the back surface thereof The same thing as a light-diffusion sheet can be used for the shaping | molding die of a light-diffusion sheet. Further, by adjusting the average particle diameter of the beads, light diffusivity can be dramatically improved.

An ultraviolet curing resin may be used as the resin, and ultraviolet irradiation may be used as the curing step. According to this means, the lens portion can be formed on the surface of the light diffusion sheet by a simple and reliable method of curing the ultraviolet curable resin by irradiation of ultraviolet light.

According to the method for manufacturing a light diffusion sheet of the present invention, a light diffusion sheet having a plurality of lens portions whose surfaces are curved like lenses can be manufactured. According to such a light diffusion sheet, the transmitted light can be uniformly dispersed throughout the light diffusion sheet by the plurality of lens portions formed on the surface. In addition, since a lens unit for dispersing light is integrally provided and beads are not used unlike a conventional light diffusion sheet, the number of parts can be reduced, and as a result, manufacturing efficiency can be improved. Furthermore, since the lens portion is integrally formed, the improvement of the strength of the light diffusion sheet itself can be promoted,
Product life can be improved. When such a lens portion is formed as a spherical concave portion, the uniformity of light diffusion can be further improved.

Therefore, a liquid crystal display device comprising a lamp, a light guide plate disposed on the side of the lamp and guiding light emitted from the lamp toward the front side, and a light diffusing sheet disposed on the front side of the light guide plate. When a light diffusion sheet manufactured by the manufacturing method of the present invention is used in a backlight unit for use in a display device, uneven brightness of a liquid crystal display device can be suppressed.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings as appropriate. FIG. 1B is a partial cross-sectional view illustrating a method for manufacturing a light diffusion sheet according to an embodiment of the present invention, and FIG. 1A is a partial cross-sectional view illustrating a light diffusion sheet manufactured by the manufacturing method. FIG. 2 is a schematic cross-sectional view illustrating the configuration of a backlight unit using the light diffusion sheet of FIG. In FIG. 1, since the light diffusing sheet 1 is turned upside down, the front surface of the light diffusing sheet 1 indicates the lower surface of the light diffusing sheet in FIG. 1, and conversely, the rear surface indicates the upper surface.

The light diffusion sheet 1 shown in FIG. 1A comprises a base sheet 2 and a light diffusion layer 3 laminated on the surface of the base sheet 2. The base sheet 2 is made of, for example, polyethylene terephthalate, polyethylene naphthalate,
It is formed from a synthetic resin such as an acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, and weather-resistant vinyl chloride. The base sheet 2 is transparent because it is necessary to transmit light, and is preferably colorless and transparent. Further, the thickness of the base sheet 2 is not particularly limited, but is, for example, not less than 50 micrometers and not more than 250 micrometers. If the thickness of the base sheet 2 is less than the above range, curling may easily occur when the resin composition for forming the light diffusion layer 3 is applied, and conversely, If the thickness of the sheet 2 exceeds the above range, the brightness of the liquid crystal display device is reduced, and the thickness of the backlight unit 5 is increased, which is against the demand for thinning the liquid crystal display device.

The light diffusion layer 3 is made of an ultraviolet curable resin, and has a large number of spherical concave portions 4 formed on the surface. The concave portion 4 on the surface of the light diffusion layer 3 exerts the same function as the concave lens, so that the light transmitted through the light diffusion layer 3 from the back side to the front side can be uniformly diffused to the front surface of the light diffusion sheet 1. The average thickness of the light diffusion layer 3 is not particularly limited, but is, for example, about 10 μm or more and 30 μm or less. Further, the ultraviolet curable resin used for the light diffusion layer 3 is not particularly limited,
For example, a) radical polymerizable resins such as epoxy acrylate, urethane acrylate, and melamine acrylate;
b) photoaddition polymerization type polythiol / polyene resin;
c) Photocationic polymerization type resin and the like. The light diffusion layer 3 is also transparent because it is necessary to transmit light, and is preferably colorless and transparent.

In the light diffusion sheet 1, the back surface of the base sheet 2 is smooth, but the back surface may be subjected to, for example, embossing to improve the light diffusion performance and the sticking prevention performance.

As shown in FIG. 2, a backlight unit 5 incorporating the light diffusing sheet 1 shown in FIG. 1A has a lamp 6 as a light source, and a lamp 6 disposed beside the lamp 6. The light guide plate 7 is provided with a light guide plate 7 for guiding light rays emitted from the light guide plate 6 toward the front side, and the light diffusion sheet 1 laminated on the front side of the light guide plate 7. In FIG. 2, the light guide plate 7 and the light diffusion sheet 1 are illustrated as being separated for convenience of explanation, but the front side surface of the light guide plate 7 and the back side surface of the light diffusion sheet 1 are actually in contact.

The locus of the light beam 8 in the backlight unit 5 will be described. First, the light beam 8 is emitted from the lamp 6 and guided into the light guide plate 7. Next, the light beam 8 in the light guide plate 7 is reflected by a reflection dot or a reflection sheet (not shown) on the back side of the light guide plate 7 and emitted to the light diffusion sheet 1 above. The light beam 8 emitted upward passes through the concave portion 4 formed on the surface of the light diffusion sheet 1, and at this time, the concave portion 4 acts like a lens and is refracted in various directions at each incident point. Therefore, the light rays 8 are uniformly diffused throughout the light diffusion sheet 1. Therefore, in the backlight unit 5, the light uniformly diffused throughout the light diffusion sheet 1 is sent to a further upper deflecting film (not shown) or the like at an equal density, thereby suppressing luminance unevenness on the screen of the liquid crystal display device. be able to.

Next, a method of manufacturing the light diffusion sheet 1 shown in FIG. 1A will be described. The manufacturing method includes a lamination step, a transfer step, a curing step, and a release step in this order. This laminating step is a step of laminating an uncured stage ultraviolet curable resin on the surface of the base sheet 2 to form the resin layer 3. In the transfer step, as shown in FIG. 1B, the resin layer 3 on the surface of the base sheet 2 obtained in the laminating step is pressed against the surface of the light diffusion sheet mold 9 to change the surface shape of the light diffusion sheet mold 9 to resin. This is a step of transferring to the layer 3. The curing step is a step of irradiating ultraviolet rays while the resin layer 3 is pressed against the light diffusion sheet mold 9 in the transfer step, to cure the resin layer 3. The last release step is a step of peeling the light diffusion sheet mold 9 from the cured resin layer 3. The light diffusion sheet 1 described above can be manufactured through the above manufacturing steps.

Light diffusion sheet mold 9 used in the above manufacturing method
Is composed of a sheet-shaped base material 10, spherical beads 11 dispersed on the surface of the base material 10, and a binder 12 for connecting the beads 11 on the base material 10. For this reason, the light diffusion sheet mold 9 is spherically curved at a plurality of positions on the surface by the beads 11. The spherical protrusions are transferred, and a plurality of spherical concave portions 4 are formed on the surface of the resin layer 3 as described above. The light diffusion sheet mold 9 is subjected to a release treatment on the surface thereof, thereby facilitating the work of peeling the resin layer 3 in the release step.

The light diffusion sheet mold 9 can be manufactured by the same method as the above-described conventional method (a) for manufacturing a light diffusion sheet. That is, it can be manufactured by a method of applying a binder 12 in which beads 11 are dispersed on the surface of the base material 10. As a material of the base material 10, a synthetic resin such as polyethylene terephthalate, polyester, or polycarbonate is used as in the case of the base material sheet 1.
As a material of the beads 11, a resin such as acryl or glass is used similarly to the beads used in the conventional light diffusion sheet. As the binder 12, acryl, urethane, or the like is used in the same manner as the binder used for the conventional light diffusion sheet.

The present invention is not limited to the above embodiment. For example, the material of the resin layer 3 may be a photo-setting resin other than an ultraviolet-setting resin such as a visible-light setting resin or a thermoplastic resin. However, the curing means in the curing step differs depending on the type of these resins. Also, the light diffusion sheet type may have a plurality of irregularities curved like a lens on the surface. For example, if the light diffusion sheet 1 of the present embodiment is used for the light diffusion sheet type, the light diffusion sheet having a spherical convex portion may be used. Sheets can be manufactured.

[0025]

As described above, according to the method for manufacturing a light diffusing sheet of the present invention, (1) since a mold and a roll are not required unlike the conventional manufacturing method by embossing, the manufacturing efficiency is improved. Can be improved. Further, a light diffusion sheet having high light diffusivity can be manufactured without using resin beads, glass beads, or the like as in the conventional manufacturing method using beads.

(2) By using a photocurable resin and transferring the surface shape of one light diffusion sheet using conventional beads, light having the same degree of light diffusion as the conventional light diffusion sheet is obtained. Many diffusion sheets can be manufactured.

(3) By changing the refractive index of the UV-curable resin used or arbitrarily adjusting the surface shape of the light-diffusing sheet to be transferred, a light-diffusing sheet with unprecedented optical performance can be manufactured.

Therefore, when a backlight unit is manufactured using such a light diffusion sheet having excellent light diffusion properties, a backlight unit with reduced luminance unevenness on the screen of a liquid crystal display device can be obtained.

[Brief description of the drawings]

1A and 1B are partial cross-sectional views illustrating a method for manufacturing a light diffusion sheet according to an embodiment of the present invention, and FIG.
It is a fragmentary sectional view showing the light diffusion sheet manufactured by the manufacturing method of the light diffusion sheet of the above.

FIG. 2 is a schematic cross-sectional view illustrating a configuration of a backlight unit using the light diffusion sheet of FIG.

DESCRIPTION OF SYMBOLS 1 light diffusion sheet 2 base sheet 3 light diffusion layer 4 concave portion 5 backlight unit 6 lamp 7 light guide plate 8 light beam 9 light diffusion sheet type 10 base material 11 beads 12 binder

Claims (6)

[Claims] 1. A light diffusion sheet integrally having a plurality of lens portions whose surfaces are curved like lenses. 2. The light diffusion sheet according to claim 1, wherein the lens portion is a spherical concave portion. 3. A laminating step of laminating a transparent resin in an uncured stage on the surface of a transparent base sheet, a sheet-like surface having a plurality of curved surfaces in a lens shape and a release treatment applied to the surface. A light diffusion sheet including a transfer step of pressing a resin laminated on the surface of the light diffusion sheet mold, a curing step of curing the resin, and a release step of peeling the light diffusion sheet mold from the resin. Manufacturing method. 4. The light diffusion sheet type includes a sheet-like base material, spherical beads dispersed on the surface of the base material, and a binder for connecting the base material and the beads. Item 4. The method for producing a light diffusion sheet according to Item 3. 5. The method for producing a light diffusion sheet according to claim 3, wherein an ultraviolet curing resin is used as the resin, and ultraviolet irradiation is used as the curing step. 6. The lamp according to claim 1, wherein the lamp is arranged on a side of the lamp, the light guide plate guides light emitted from the lamp in a front side direction, and the light guide plate is arranged on a front side of the light guide plate. A backlight unit for a liquid crystal display device comprising a light diffusion sheet.