JPH0795121B2 - Fresnel lens sheet manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a Fresnel lens sheet with high productivity.

(Prior Art) Conventionally, a Fresnel lens sheet has been manufactured by a molding method by heating and pressing a thermoplastic resin or the like using a mold, but in this method, after heating the thermoplastic resin and embossing it, However, since it needs to be cooled below the heat distortion temperature, there is a drawback that molding takes time.

Further, since the mold is also exposed to high temperature, the surface of the mold is oxidized and the prism shape of the Fresnel lens is changed, which causes a problem that the reproducibility of the Fresnel lens is deteriorated.

For this reason, in recent years, a method has been adopted in which a lens molding die that can be manufactured under relatively mild conditions is filled with a curable resin, and the resin is cured and shaped.

(Problems to be solved by the invention) However, this method requires laminating a transparent plastic film on one surface of the curable resin in order to increase the strength of the Fresnel lens sheet. Since the surface of the curable resin is coated with a transparent plastic film and then the resin is cured, the resulting Fresnel lens sheet is liable to curl due to polymerization shrinkage of the curable resin. However, there is a problem in that the yield is poor in terms of manufacturing and a post-process for curl correction is required.

(Means for Solving the Problems) The present inventors have found that even if a curable resin having substantially the same polymerization shrinkage ratio is provided on both surfaces of a transparent film and the resin is cured, the resin is cured to form a laminate. Paying attention to the fact that the body does not curl, in the production of Fresnel lenses, the other side of the transparent film coated on the surface of the curable resin to be shaped has substantially the same polymerization shrinkage ratio as the resin. The present invention has been completed by finding that the above problems can be solved by curling the resulting Fresnel lens if the curable resin is applied and then the resin is cured.

That is, according to the manufacturing method of the present invention, a molding die having a mold surface that is an inverse shape of the prism shape of the Fresnel lens is filled with the first curable resin liquid that is cured by ultraviolet rays or electron beams, and the filling is performed. A second curable resin liquid having the same or substantially the same polymerization shrinkage as the first curable resin, which is formed by coating a transparent film on the surface of the resin liquid resin and then curing the transparent film with ultraviolet rays or electron beams. And then irradiating with an ultraviolet ray or an electron beam.
And a second resin liquid are simultaneously cured, a prism shape of a Fresnel lens is imprinted on the first resin, and then the molding die is removed to produce a Fresnel lens sheet. To do.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a partial sectional view of a Fresnel lens sheet manufactured by the method of the present invention.

The Fresnel lens sheet 1 includes a resin layer 2 made of a first curable resin in which prism-shaped grooves of a Fresnel lens are engraved, a transparent film 3 as a support for supporting the Fresnel lens sheet, and a second curable resin. The second resin layer 4 made of is laminated in this order. Here, although not shown, an anchor layer for improving the adhesive strength between the transparent film 3 and the first resin layer 2 and the second resin layer 4 may be provided between the transparent film 3 and the first resin layer 2 and the second resin layer 4.

As the first curable resin, a thermosetting resin, an ultraviolet curable resin and an electron beam curable resin can be used, and specifically, a hydrocarbon resin, an acrylic resin (polyacrylic acid ester, Methacrylic acid ester, polyacrylonitrile, polyacrylic acid, polyacrylamide), vinyl acetate resin and its derivatives (polyvinyl acetate, polyvinyl alcohol, acetal resin) halogen-containing resin (polyvinyl chloride, polyvinyldene chloride, fluororesin), Vinyl polymerization resin (polyvinyl pyrrolidone, polyvinyl pyridine, polyvinyl carbazole) of nitrogen cyclic compound, polyether resin (polyethylene oxide,
Polyoxymethylene, potassium propylene oxide), polyalkyleneimine, lactam polymerization resin (polypyrrolidone, N-vinyllactam), fumaric acid or fumaric acid ester resin, aromatic vinyl resin and the like are used.

The transparent film 3 can be widely used as long as it is a transparent film having appropriate strength and capable of transmitting ultraviolet rays or electron beams to such an extent that the curable resin can be cured, and specifically, Films of polyvinyl chloride, ABS resin, polycarbonate, polyester, polystyrene, acryl, polyolefin, polyamide, etc. are used.

As the second curable resin, the first curable resin layer 2 is used.
The resin that forms the
The curling of the Fresnel lens sheet to be produced can be prevented by selecting and using the resin so as to have a polymerization shrinkage rate substantially the same as that of the curable resin. Specifically, the difference in the polymerization shrinkage between the first curable resin and the second curable resin varies depending on the thickness of the resin layer, the material and thickness of the transparent film, the intensity of irradiation rays, etc., but is 0.2%.
It is desirable that it is a degree.

In addition, in the present invention, a light diffusing agent may be added to the first curable resin to impart light diffusing property to the manufactured Fresnel lens sheet. As such a light diffusing agent, a substance having a property of scattering light can be used.
Fine particles of finely pulverized glass fiber, titanium oxide, calcium carbonate, silicon dioxide, aluminum oxide, various clays, silica, resin powder and the like are used, and these fine particles are added at a ratio of 1 to 10% by weight with respect to the resin.

In the Fresnel lens sheet manufactured by the above method, only the first resin layer 2 and the light diffusing layer serve as the light diffusing layer, and thus the light diffusing layer is thinned over the entire sheet manufactured by the conventional method. It can provide sharper image quality than the one with the agent.

FIG. 2 is a diagram schematically illustrating the manufacturing method of the present invention.

Reference numeral 5 in the figure denotes a Fresnel lens molding die, in which a shape opposite to the prism shape of the Fresnel lens is formed as irregularities on the die surface, and the material thereof is metal or resin having solvent resistance. When the molding die 5 made of resin is used, there is an advantage that ultraviolet rays or electron beams can be irradiated from the molding die 5 side as described later.

The first resin layer 2 is coated on the mold surface of the molding die 5 with a first resin which is cured by ultraviolet rays or electron beams, and a transparent film 3 is further coated on the first resin layer 2, and then the same as the resin. The second resin layer 4 is coated with a second resin having a polymerization shrinkage of 1 or 2 which is cured by an ultraviolet ray or an electron beam, and the second resin layer 4 is irradiated with an ultraviolet ray or an electron beam 6 to cure the first curable resin and the second curable resin. At the same time as the curable resin is cured, the prism shape of the Fresnel lens is imprinted on the first resin layer 2. As the coating method of the above resin liquid, known methods such as roll coating, knife coating, Miyabar coating, gravure coating, screen printing and pouring may be used, and the coating thickness is the strength and characteristics of the Fresnel lens sheet after curing. In consideration of the above, it is determined appropriately. Irradiation with ultraviolet rays or electron beams may be carried out directly on the resin-coated surface, but if the molding die 5 allows passage of ultraviolet rays or electron beams, irradiation with the molding die 5 is also possible. This has the advantage of increasing the degree of freedom in design.

After the first curable resin and the second curable resin are cured as described above, the molding die 5 can be peeled off to obtain the Fresnel lens sheet 1.

(Effect of the Invention) According to the production method of the present invention, since a resin having substantially the same polymerization shrinkage can be simultaneously cured on both sides of a transparent film as a support, a Fresnel lens with less curling and good lens characteristics can be obtained. A sheet can be efficiently manufactured without a decurling step. Further, when a light diffusing agent is added to the first resin layer, a Fresnel lens sheet having light diffusing property and capable of providing sharp image quality can be obtained. Obtainable.

(Example) Hereinafter, the present invention will be described in more detail based on specific examples.

Example 1 An epoxy acrylate-based UV curable resin (trade name, UV531A; made by Morohoshi Ink Co., Ltd.) was used as a first curable resin in a molding die in which the reverse shape of the Fresnel lens prism shape was provided on the mold surface. It was filled to a thickness of 300 μ, and the surface was smoothed by squeezing to form a first resin layer.

Next, the surface of the resin was coated with a polyester film having a thickness of 100 μ and having primer layers provided on both surfaces in advance.

Next, the same resin as the first curable resin was applied on the above-mentioned film by a mier bar coating to a thickness of 300 μm to form a second resin layer.

Next, from the second resin layer side, ultraviolet rays are radiated for 60 seconds by two ultraviolet lamps having an output of 4 KW to completely cure the above two resin layers, and then the mold is removed to remove a Fresnel having a thickness of 700 μm. I got a lens sheet.

The Fresnel lens sheet obtained had good physical properties without curling.

Example 2 An epoxy acrylate UV curable resin (trade name, UV531A; made by Moroboshi Ink Co., Ltd.) was used as the first curable resin in a molding die in which the reverse shape of the Fresnel lens prism shape was provided on the mold surface. It was filled to a thickness of 300 μ, and the surface was smoothed by squeezing to form a first resin layer.

Next, the surface of the resin was coated with a polyester film having a thickness of 100 μ and having primer layers provided on both surfaces in advance.

Next, 0.2% more than the first curable resin on the above film.
Then, a polyester acrylate-based UV curable resin having a different polymerization shrinkage was applied to the second resin layer by a bar coating to a thickness of 300 μm.

Next, from the second resin layer side, ultraviolet rays are radiated for 60 seconds by two ultraviolet lamps with an output of 4 KW to completely cure the above two resins, and then the mold is removed to release a Fresnel lens with a thickness of 700 μm. Got the sheet.

The Fresnel lens sheet obtained had good physical properties without being carted.

Example 3 An epoxy containing 5% of silica powder (trade name, Hugh Rex Y-20) as a first curable resin in a molding die in which the reverse shape of the prism shape of a Fresnel lens is provided on the mold surface. Acrylate UV curable resin (trade name, U
V531A (made by Morohoshi Ink Co., Ltd.) was filled to a thickness of 300 μm, and the surface was smoothed by squeezing to form a first resin layer.

Next, the surface of the resin was coated with a polyester film having a thickness of 100 μ and having primer layers provided on both surfaces in advance.

Next, the same resin as the first curable resin was applied on the above-mentioned film by a mier bar coating to a thickness of 300 μm to form a second resin layer.

Next, from the second resin layer side, ultraviolet rays are radiated for 60 seconds by two ultraviolet lamps having an output of 4 KW to completely cure the above two resin layers, and then the mold is removed to remove a Fresnel having a thickness of 700 μm. I got a lens sheet.

The Fresnel lens sheet thus obtained had good physical properties without curling, and gave sharp image quality as compared with the Fresnel lens sheet containing a light diffusing agent produced by a pressing method.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a Fresnel lens sheet manufactured by the present invention, and FIG. 2 is an explanatory view schematically showing the manufacturing method of the present invention. 1 ... Fresnel lens sheet 2 ... first resin layer 3 ... transparent film 4 ... second resin layer 5 ... molding die

Claims (2)

[Claims] 1. A molding die having a mold surface which is an inverse shape of a prism shape of a Fresnel lens is filled with a first curable resin liquid which is cured by ultraviolet rays or electron beams, and the filled resin resin liquid After coating a transparent film on the surface, a second curable resin liquid having the same or substantially the same polymerization shrinkage as the first curable resin that is cured by ultraviolet rays or electron beams is applied onto the transparent film, Then, the first and second resin liquids are simultaneously cured by irradiating with ultraviolet rays or electron beams, and at the same time, the prism shape of the Fresnel lens is imprinted on the first resin, and then the molding die is removed. A method of manufacturing a Fresnel lens sheet, which comprises manufacturing a Fresnel lens sheet. 2. The method for producing a Fresnel lens sheet according to claim 1, wherein the first curable resin and the second curable resin contain a light diffusing agent.