JP2001315148A - Molding die for light diffusion sheet and producing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide both a producing method for a light diffusion sheet, in which multiscattering can be prevented and diffusing power of the same degree as the light diffusion sheet using a bead can be exerted, and a molding die for the light diffusion sheet used for such the producing method as this. SOLUTION: The producing method for the light diffusion sheet is equipped with (a) a die forming process, in which a light diffusion sheet model 1 having the same shape as the light diffusion sheet is used and a metal is electrodeposited on the surface of the light diffusion sheet model 1 by an electrocasting method and the molding die 2 for the light diffusion sheet is obtained by releasing the light diffusion sheet model 1 from a formed metallic layer, (b) a laminating process for laminating a transparent synthetic resin 7 of an uncured stage on the molding die 2 for the light diffusion sheet, (c) a curing process for curing the synthetic resin 7 and (d) a mold release process for releasing the molding die 2 for the light diffusion sheet from the synthetic resin 7.

Description

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 diffusion sheet used for a backlight unit of a liquid crystal display device and a mold for a light diffusion sheet used for the method for manufacturing the light diffusion sheet.

[0002]

2. Description of the Related Art In a liquid crystal display device, a backlight system in which a liquid crystal layer is illuminated from the back surface to emit light has become widespread, and a backlight unit is provided on a lower surface side of the liquid crystal layer. Generally, as shown in FIG. 2A, the backlight unit 50 includes a rod-shaped lamp 51 as a light source, and a rectangular plate-shaped light guide plate 52 arranged such that an end thereof is along the lamp 51. And a plurality of optical sheets 53 laminated on the front side of the light guide plate 52. This optical sheet 5
Reference numerals 3 denote specific optical properties such as refraction and diffusion, and more specifically, a light diffusion sheet 54 disposed on the surface side of the light guide plate 52 and a light diffusion sheet 54 disposed on the surface side of the light diffusion sheet 54. The prism sheet 55 to be provided corresponds to this.

The function of the backlight unit 50 will be described. First, a light beam incident on the light guide plate 52 from the lamp 51 is reflected by a reflection dot or a reflection sheet (not shown) on the back surface of the light guide plate 52 and each side surface. The light is emitted from the surface of the light guide plate 52. Light emitted from the light guide plate 52 enters the light diffusion sheet 54, is diffused, and is emitted from the surface of the light diffusion sheet 54. Thereafter, the light beam emitted from the light diffusion sheet 54 enters the prism sheet 55, and is emitted by the prism portion 55a formed on the surface of the prism sheet 55 as a light beam having a distribution showing a peak almost directly above. Thus, the light beam emitted from the lamp 51 is
The light is diffused by the light diffusion sheet 54, is refracted by the prism sheet 55 so as to show a peak almost directly above, and illuminates the entire liquid crystal layer (not shown) further above.

[0004] Although not shown, there is also a backlight unit in which a light diffusion sheet or a prism sheet is further disposed on the surface side of the prism sheet 55 in consideration of the light-collecting characteristics of the prism sheet 55 described above.

[0005] As the light diffusion sheet 54 of the backlight unit 50 having the above-described structure, a laminate of a base layer 56 and a light diffusion layer 57 as shown in FIG. 2B is generally used. The light diffusion layer 57 is made of a synthetic resin in a binder 58 made of a synthetic resin such as an acrylic resin.
It has a structure in which beads 59 made of glass or the like are dispersed.

[0006]

According to the above-mentioned conventional light diffusion sheet 54, since the refraction and reflection by the beads 59 in the binder 58 are used for expressing the diffusion ability, a multiple scattering phenomenon occurs, Inevitably, a loss of light output is inevitable.

The present invention has been made in view of these inconveniences, and a method of manufacturing a light diffusion sheet which can prevent multiple scattering and can exhibit the same level of diffusing ability as a light diffusion sheet using beads. An object of the present invention is to provide a mold for a light diffusion sheet used in a manufacturing method.

[0008]

The invention made to solve the above-mentioned problem uses a light diffusion sheet model having the same shape as the light diffusion sheet, and a metal is electroformed on the surface of the light diffusion sheet model by an electroforming method. A light diffusion sheet forming die formed by attaching and peeling the light diffusion sheet model from the electrodeposited metal layer. Here, “electroforming” means a method of applying a principle of electroplating to electrodeposit a metal on the surface of a model.

The light diffusion sheet mold uses an electroforming method for its production, so that the complicated surface shape of the light diffusion sheet model is accurately transferred and duplicated.
Therefore, by using the light diffusion sheet molding die, a light diffusion sheet having the same surface shape as the light diffusion sheet model can be easily mass-produced.

The light diffusion sheet model includes a base material layer on the back side and a light diffusion layer on the front side in which beads are dispersed in a binder, that is, a bead coating type using beads as a conventional diffusing agent. It is preferable to use the same one as the light diffusion sheet.

According to the molding die for a light diffusion sheet using the light diffusion sheet of the bead coating type as a light diffusion sheet model, the unevenness of the surface is the same as that of the light diffusion sheet of the bead coating type. In addition, it becomes possible to manufacture a light diffusion sheet having no beads inside. Therefore, the light diffusion sheet manufactured by the light diffusion sheet forming die prevents multiple scattering and reduces the loss of the output light amount while maintaining the same level of diffusion ability as the light diffusion sheet of the bead coating type. be able to.

Further, the invention relating to a method for manufacturing a light diffusion sheet comprises: (a) using a light diffusion sheet model having the same shape as the light diffusion sheet, and forming a metal on the surface of the light diffusion sheet model by electroforming. Forming a light diffusion sheet mold by peeling the light diffusion sheet model from the applied metal layer; and (b) laminating an uncured transparent synthetic resin on the light diffusion sheet mold. And (c) a curing step of curing the synthetic resin, and (d) a mold release step of peeling off the light diffusion sheet forming die from the synthetic resin. And a light diffusion layer on the surface side in which beads are dispersed in a binder. According to the method for manufacturing the light diffusion sheet, a mold similar to the mold for the light diffusion sheet is manufactured, and by a relatively simple method and a small number of steps, while maintaining the above-described high diffusivity, multiple scattering is prevented. Light diffusion sheets that can be prevented can be mass-produced.

It is preferable to use an ultraviolet curing resin as the synthetic resin, and to use ultraviolet irradiation in the curing step. According to this means, the surface shape of the light diffusion sheet can be formed by a simple and reliable method of curing the ultraviolet curable resin by irradiation of ultraviolet rays.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings as appropriate. 1A to 1C are schematic sectional views illustrating a method for manufacturing a light diffusion sheet according to one embodiment of the present invention.

The method for manufacturing the light diffusion sheet shown in FIG. 1 includes a mold forming step, a laminating step, a curing step, and a releasing step.

In the mold forming step, as shown in FIG.
In this step, a metal is electrodeposited on the surface of the light diffusion sheet model 1 by an electroforming method, and the light diffusion sheet model 1 is separated from the formed metal layer to obtain the light diffusion sheet molding die 2.

The light diffusion sheet model 1 is the same as the conventional light diffusion sheet of the bead coating type. Specifically, the light diffusion sheet model 1 is formed by laminating a base layer 3 and a surface of the base layer 3. And the light diffusion layer 4 formed.

The base layer 3 is made of a synthetic resin such as polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, and weather resistant vinyl chloride. Further, the thickness of the base material layer 3 is not particularly limited.
0 micrometer or less. If the thickness of the base material layer 3 is less than the above range, curling may easily occur when the resin composition for forming the light diffusion layer 4 is applied, and conversely, If the thickness of the layer 3 exceeds the above range, the brightness of the liquid crystal display device is reduced, and the thickness of the backlight unit is increased, which is against the demand for thinning the liquid crystal display device.

The light diffusion layer 4 comprises a binder 5 and beads 6 dispersed in the binder 5. The beads 6 are provided with ones whose upper ends protrude from the binder 5 or are buried in the binder 5 in order to diffuse the light rays better. The thickness of the light diffusion layer 4 (meaning the thickness of the binder 5 excluding the beads 6) is not particularly limited.
It is about μm or less.

Examples of the polymer used for the binder 5 include acrylic resins, polyurethanes, polyesters, fluorine resins, silicone resins, polyamide imides, epoxy resins and the like. Further, in addition to the above-mentioned polymer, for example, a plasticizer, a stabilizer, a deterioration inhibitor, a dispersant, and the like may be blended in the binder 5.

The beads 6 are substantially spherical, and examples of the material include acrylic resin, polyurethane, polyvinyl chloride, polystyrene, polyacrylonitrile, polyamide and the like.

The particle size of the beads 6 is 0.1 μm or more and 100
μm or less, preferably 1 μm or more and 50 μm or less. If the particle size of the beads 6 is less than the above range, the light diffusion effect becomes insufficient. Conversely, if the particle size exceeds the above range, the coating of the resin composition forming the light diffusion layer 4 is not performed. This is because the work becomes difficult.

The amount of the beads 6 in the light diffusion layer 4 is 0.1 part or more to 100 parts of the polymer in the binder 5.
It is preferably at most 00 parts, particularly preferably at least 5 parts and at most 300 parts. This means that if the amount is less than the above range,
The above-mentioned effect of improving the total light transmittance becomes insufficient,
On the other hand, even if the compounding amount exceeds the above range, the total light transmittance decreases.

As described above, the light diffusion sheet model 1 serving as a duplication source is made of a synthetic resin. However, since the electroforming method can be molded at room temperature in principle, the light diffusion sheet model 1 is formed during the mold forming process. It is possible to manufacture the light diffusion sheet molding die 2 in which the irregularities on the surface are transferred as they are without deformation of the mold 1.

The metal to be electrodeposited on the light diffusion sheet model 1 in the mold forming step is not particularly limited, and examples thereof include silver, gold, copper, iron, nickel, lead, platinum, tin, and zinc. It can be used. Above all, in consideration of the electrodeposition property for the light diffusion sheet model 1 having a predetermined shape and the releasability from the light diffusion sheet model 1 after electrodeposition,
Copper and nickel are preferred.

In the laminating step, as shown in FIG. 1 (b), an uncured transparent synthetic resin 7 is laminated on the mold surface of the light diffusion sheet molding die 2 formed in the mold forming step. This is a step of molding the synthetic resin 7 into a sheet. As the synthetic resin 7, an ultraviolet curable resin or a thermosetting resin can be used, and since it is necessary to transmit light, it is preferably transparent, particularly preferably colorless and transparent. Examples of the ultraviolet curable resin used for the synthetic resin 7 include: a) a radical polymerizable resin such as epoxy acrylate, urethane acrylate, and melamine acrylate; b) a photoaddition polymerizable polythiol / polyene resin; and c) a photocationic polymerizable resin. And the like. Examples of the thermosetting resin include a urea resin, a melamine resin, a phenol resin, an epoxy resin, an unsaturated polyester resin, an alkyd resin, and a urethane resin.

The curing step is a step of curing the synthetic resin 7 laminated on the light diffusion sheet molding die 2 in the above-mentioned laminating step. The specific curing means differs depending on the type of the synthetic resin 7. For example, when an ultraviolet curable resin is used as the synthetic resin 7, the synthetic resin 7 is irradiated with ultraviolet rays.

The last release step is a step of peeling off the light diffusion sheet molding die 2 from the synthetic resin 7 cured by the above-mentioned curing step. By going through the above manufacturing steps, FIG.
The manufacture of the light diffusion sheet 8 shown in (c) is completed.

The light diffusing sheet 8 produced by the method for producing a light diffusing sheet of the present invention has the irregularities on the surface of the light diffusing sheet model 1 which is a light diffusing sheet of the bead coating type transferred as it is, and And no beads. Therefore, the same diffusing ability as that of the conventional bead-coated light diffusion sheet can be exerted by the same surface irregularities as the light diffusion sheet model 1, and the loss of light rays due to multiple scattering due to the use of beads can be reduced. Can be.

[0030]

As described above, according to the light diffusion sheet forming die and the method for manufacturing the light diffusion sheet using the same according to the present invention, light loss due to multiple scattering is eliminated, and luminance is improved. It becomes possible to manufacture a light diffusion sheet having small performance variations.

[Brief description of the drawings]

FIGS. 1A to 1C show a method for manufacturing a light diffusion sheet according to an embodiment of the present invention.

FIG. 2A is a schematic perspective view showing a general backlight unit, and FIG. 2B is a schematic cross-sectional view showing a conventional general light diffusion sheet.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light diffusion sheet model 2 mold for light diffusion sheet 3 base material layer 4 light diffusion layer 5 binder 6 beads 7 synthetic resin 8 light diffusion sheet

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29L 7:00 B29L 7:00 F term (Reference) 2H042 BA04 BA15 BA20 2H091 FA21Z FA32Z FA41Z FC06 FD06 LA18 4F202 AA44 AE10 AF01 AG01 AG05 AJ02 CA09 CB01 CD02 CD12 4F205 AA44 AE10 AF01 AG01 AG05 AJ02 GA15 GB01 GN29 GN30

Claims (5)

[Claims] 1. A light diffusion sheet model having the same shape as the light diffusion sheet, a metal is electrodeposited on the surface of the light diffusion sheet model by an electroforming method, and the light diffusion sheet model is peeled off from the electrodeposited metal layer. Forming mold for light diffusion sheet. 2. The light diffusion sheet molding according to claim 1, wherein the light diffusion sheet model includes a base layer on the back side and a light diffusion layer on the front side in which beads are dispersed in a binder. Type. 3. A light diffusion sheet model having the same shape as the light diffusion sheet, a metal is electrodeposited on the surface of the light diffusion sheet model by an electroforming method, and the light diffusion sheet model is separated from the formed metal layer. A mold forming step of obtaining a light diffusion sheet molding die, a lamination step of laminating an uncured stage of a transparent synthetic resin on the light diffusion sheet molding die, a curing step of curing the synthetic resin, and the synthetic resin A mold releasing step of peeling off a light-diffusing sheet forming mold from a light-diffusing sheet. 4. The production of the light diffusion sheet according to claim 3, wherein the light diffusion sheet model has a base material layer on the back side and a light diffusion layer on the front side in which beads are dispersed in a binder. Method. 5. The method for producing a light diffusion sheet according to claim 3, wherein an ultraviolet curing resin is used as the synthetic resin, and irradiation of ultraviolet light is used in the curing step.