JP4321946B2 - Mold for light diffusion sheet and method for manufacturing light diffusion sheet - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a light diffusing sheet used in a backlight unit of a liquid crystal display device and a mold for a light diffusing sheet used in the method for producing the light diffusing sheet.
[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. 2A, the backlight unit 50 generally includes a rod-shaped lamp 51 serving as a light source, and a rectangular plate-shaped light guide plate 52 that is disposed so that an end thereof is along the lamp 51. And a plurality of optical sheets 53 stacked on the surface side of the light guide plate 52. Each of the optical sheets 53 has specific optical properties such as refraction and diffusion. Specifically, the light diffusion sheet 54 disposed on the surface side of the light guide plate 52 and the surface of the light diffusion sheet 54 For example, the prism sheet 55 disposed on the side corresponds to this.
[0003]
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. Emitted from the surface. Light rays emitted from the light guide plate 52 enter the light diffusion sheet 54, are diffused, and are 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 as a light beam having a distribution having a peak in a substantially upward direction by the prism portion 55 a formed on the surface of the prism sheet 55. In this way, the light beam emitted from the lamp 51 is diffused by the light diffusion sheet 54 and refracted by the prism sheet 55 so as to show a peak in a substantially upward direction, and further the entire liquid crystal layer not shown above is Illuminate.
[0004]
Although not shown, there is also a backlight unit in which a light diffusion sheet and a prism sheet are further arranged on the surface side of the prism sheet 55 in consideration of the light condensing characteristics of the prism sheet 55 described above.
[0005]
As the light diffusion sheet 54 of the backlight unit 50 having the above structure, a laminate of a base material layer 56 and a light diffusion layer 57 as shown in FIG. 2B is generally used. The light diffusion layer 57 has a structure in which beads 59 made of synthetic resin, glass or the like are dispersed in a binder 58 made of synthetic resin such as acrylic resin.
[0006]
[Problems to be solved by the invention]
According to the conventional light diffusing sheet 54, since the refraction and reflection by the beads 59 in the binder 58 are utilized for the expression of the diffusing ability, the multiple scattering phenomenon occurs and the loss of the emitted light quantity is inevitable.
[0007]
The present invention has been made in view of these disadvantages, and relates to a method for manufacturing a light diffusing sheet that can prevent multiple scattering and that can exhibit the same diffusivity as a light diffusing sheet using beads, and such a manufacturing method. The object is to provide a mold for a light diffusion sheet to be used.
[0008]
[Means for Solving the Problems]
The invention made in order to solve the above problems uses a light diffusion sheet model having the same shape as the light diffusion sheet, and electrodeposits metal onto the surface of the light diffusion sheet model by electroforming, and from the electrodeposited metal layer It is the light-diffusion-sheet shaping | molding die formed by peeling the said light-diffusion sheet model. Here, the “electroforming method” means a method of applying metal to the surface of a model by applying the principle of electroplating.
[0009]
Since the light diffusing sheet forming die uses an electroforming method for its production, the complicated surface shape of the light diffusing sheet model is accurately transferred and duplicated. Therefore, when the light diffusion sheet molding die is used, a light diffusion sheet having the same surface shape as that of the light diffusion sheet model can be easily mass-produced.
[0010]
As a model of the above-mentioned light diffusion sheet, a material having a base 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 light diffusion using beads as a conventional diffusing agent. A sheet similar to the sheet may be used.
[0011]
In this way, according to the light diffusion sheet forming mold using the bead coating type light diffusion sheet as a light diffusion sheet model, the uneven shape of the surface is the same as that of the bead coating type light diffusion sheet, and It is possible to manufacture a light diffusion sheet in which no beads exist. Therefore, the light diffusing sheet manufactured by the light diffusing sheet molding die maintains the same diffusing ability as the bead coating type light diffusing sheet, prevents multiple scattering, and reduces the loss of light output. be able to.
[0012]
The invention relating to the method for producing a light diffusing sheet includes (a) a light diffusing sheet model having the same shape as the light diffusing sheet, and a metal formed by electrodepositing metal on the surface of the light diffusing sheet model by electroforming. A mold forming step of obtaining a light diffusing sheet mold by peeling the light diffusing sheet model from the layer; and (b) a laminating step of laminating an uncured transparent synthetic resin on the light diffusing sheet mold, (C) a curing step of curing the synthetic resin, and (d) a release step of peeling the light diffusion sheet mold from the synthetic resin, and the back side substrate as the light diffusion sheet model A layer and a light diffusion layer on the surface side where beads are dispersed in a binder may be used. According to the light diffusing sheet manufacturing method, a mold similar to the above light diffusing sheet mold is manufactured, and multiple scattering can be performed while maintaining the above high diffusivity by a relatively simple method and few steps. The light diffusion sheet that can be prevented can be mass-produced.
[0013]
An ultraviolet curable resin may be used as the synthetic resin, and ultraviolet irradiation may be used for 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 with ultraviolet rays.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. 1A to 1C are schematic cross-sectional views illustrating a method for manufacturing a light diffusion sheet according to an embodiment of the present invention.
[0015]
The manufacturing method of the light diffusion sheet in FIG. 1 includes a mold forming process, a laminating process, a curing process, and a mold releasing process.
[0016]
In the mold forming process, as shown in FIG. 1A, a metal is electrodeposited on the surface of the light diffusion sheet model 1 by electroforming, and the light diffusion sheet model 1 is peeled off from the formed metal layer. This is a step of obtaining the diffusion sheet mold 2.
[0017]
The light diffusing sheet model 1 is the same as a conventional bead coating type light diffusing sheet. Specifically, the base material layer 3 and light laminated on the surface of the base material layer 3 are used. And a diffusion layer 4.
[0018]
The base material layer 3 is formed of a synthetic resin such as polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, and weather resistant vinyl chloride. Moreover, the thickness of the base material layer 3 is not particularly limited, but is, for example, 50 micrometers or more and 250 micrometers 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 forming the light diffusion layer 4 is applied. This is because if the thickness of the layer 3 exceeds the above range, the luminance of the liquid crystal display device is lowered, and the thickness of the backlight unit is increased, which is against the demand for thinning of the liquid crystal display device.
[0019]
The light diffusion layer 4 includes a binder 5 and beads 6 dispersed in the binder 5. Further, the beads 6 are provided with the upper ends protruding from the binder 5 or embedded in the binder 5 in order to better diffuse the light beam. The thickness of the light diffusion layer 4 (meaning the thickness of the binder 5 portion excluding the beads 6) is not particularly limited, but is, for example, about 1 μm or more and 30 μm or less.
[0020]
Examples of the polymer used for the binder 5 include acrylic resin, polyurethane, polyester, fluorine resin, silicone resin, polyamideimide, and epoxy resin. In addition to the above-mentioned polymer, the binder 5 may contain, for example, a plasticizer, a stabilizer, a deterioration inhibitor, a dispersant, and the like.
[0021]
The beads 6 are substantially spherical, and examples of the material thereof include acrylic resin, polyurethane, polyvinyl chloride, polystyrene, polyacrylonitrile, and polyamide.
[0022]
The particle size of the beads 6 is preferably 0.1 μm or more and 100 μm or less, and particularly 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 diffusing effect becomes insufficient. Conversely, if the particle size exceeds the above range, the resin composition for forming the light diffusing layer 4 is applied. This is because the work becomes difficult.
[0023]
The amount of the beads 6 in the light diffusion layer 4 is preferably 0.1 part or more and 500 parts or less, particularly preferably 5 parts or more and 300 parts or less, with respect to 100 parts of the polymer in the binder 5. If the blending amount is less than the above range, the above-mentioned total light transmittance improving effect becomes insufficient. On the other hand, even if the blending amount exceeds the above range, the total light transmittance is decreased. Because to do.
[0024]
As described above, the light diffusing sheet model 1 as a replication source is made of a synthetic resin. However, since the electroforming method can be molded at room temperature in principle, the light diffusing sheet model 1 is deformed during the mold forming process. Therefore, it is possible to manufacture the light diffusion sheet forming die 2 in which the uneven shape of the surface is transferred as it is.
[0025]
The metal electrodeposited on the light diffusion sheet model 1 in the mold forming process is not particularly limited, and for example, silver, gold, copper, iron, nickel, lead, platinum, tin, zinc, or the like is used. Among these, copper and nickel are preferable in consideration of electrodeposition on the light diffusion sheet model 1 having a predetermined shape and releasability from the light diffusion sheet model 1 after electrodeposition.
[0026]
In the laminating step, as shown in FIG. 1B, an uncured transparent synthetic resin 7 is laminated on the mold surface of the light diffusing sheet mold 2 formed in the mold forming step, and the synthetic resin 7 Is a step of forming a sheet 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 colorless and transparent. Examples of the ultraviolet curable resin used for the synthetic resin 7 include: a) radical polymerization resins such as epoxy acrylate, urethane acrylate, and melamine acrylate; b) photoaddition polymerization type polythiol / polyene resin; c) photocationic polymerization type resin. Etc. Examples of the thermosetting resin include urea resin, melamine resin, phenol resin, epoxy resin, unsaturated polyester resin, alkyd resin, and urethane resin.
[0027]
The curing step is a step of curing the synthetic resin 7 laminated on the light diffusion sheet molding die 2 in the above-described lamination step, and the specific curing means varies depending on the type of the synthetic resin 7. For example, when an ultraviolet curable resin is used for the synthetic resin 7, the synthetic resin 7 is irradiated with ultraviolet rays.
[0028]
The final mold releasing step is a step of peeling the light diffusion sheet forming die 2 from the synthetic resin 7 after being cured by the curing step. Through the above manufacturing process, the manufacture of the light diffusion sheet 8 shown in FIG. 1C is completed.
[0029]
The light diffusing sheet 8 manufactured by the method for manufacturing a light diffusing sheet of the present invention has the uneven shape on the surface of the light diffusing sheet model 1 which is a bead coating type light diffusing sheet transferred as it is, and the beads are placed inside. It will not have. Therefore, the same surface irregularities as the light diffusion sheet model 1 can exhibit the same diffusivity as a conventional bead coating type light diffusion sheet, and further reduce the light loss due to multiple scattering caused by the use of beads. Can do.
[0030]
【The invention's effect】
As described above, according to the mold for light diffusing sheet of the present invention and the method for manufacturing a light diffusing sheet using the same, there is no loss of light due to multiple scattering, the luminance is improved, and the variation in performance is small. A light diffusion sheet can be manufactured.
[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]
DESCRIPTION OF SYMBOLS 1 Light diffusion sheet model 2 Mold for light diffusion sheet 3 Base material layer 4 Light diffusion layer 5 Binder 6 Bead 7 Synthetic resin 8 Light diffusion sheet

Claims (5)

A light diffusion sheet model having the same shape as the light diffusion sheet was used, and a metal was electrodeposited on the surface of the light diffusion sheet model by electroforming, and the light diffusion sheet model was peeled off from the electrodeposited metal layer. Mold for light diffusion sheet. The mold for a light diffusing sheet according to claim 1, wherein the light diffusing sheet model is provided with a base layer on the back side and a light diffusing layer on the front side in which beads are dispersed in a binder. Using a light diffusion sheet model that is the same shape as the light diffusion sheet, electrodepositing metal onto the surface of the light diffusion sheet model by electroforming, and peeling the light diffusion sheet model from the formed metal layer A mold forming step for obtaining a mold;
A laminating step of laminating an uncured transparent synthetic resin on the mold for light diffusion sheet;
A curing step for curing the synthetic resin;
A method for producing a light diffusing sheet, comprising: a mold releasing step of peeling the mold for light diffusing sheet from the synthetic resin. 4. The method for producing a light diffusing sheet according to claim 3, wherein the light diffusing sheet model includes a back side base layer and a front side light diffusing layer in which beads are dispersed in a binder. Using an ultraviolet curable resin as the synthetic resin,
The manufacturing method of the light-diffusion sheet of Claim 3 or Claim 4 which uses irradiation of an ultraviolet-ray for the said hardening process.

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