JP2678713B2 - Fresnel lens and manufacturing method thereof - Google Patents

Description

BACKGROUND OF THE INVENTION [0001] Field of the Invention The present invention, projection television and microfilm projection screen to be used as screen readers, etc., such as a shutter lens or perspective variable lens <br/>'s The present invention relates to a method for manufacturing a Fresnel lens used in the optical field. Fresnel lenses are not used in various optical fields because they do not have a large thickness or weight as compared with general convex lenses and concave lenses and can exhibit lens hardening over a wide area. There is. Recently, it has been attempted to provide such a Fresnel lens with a transparent electrode function and to develop it into, for example, a shutter lens enclosing a liquid crystal or a perspective variable lens. By the way, as a method of manufacturing such a Fresnel lens, glass has been used for the cutting process in the old days, but since the productivity cannot be improved, recently, a synthetic resin material is injection-molded, compression-molded or pressed. It has come to be manufactured by molding or the like. [0005] The present invention is, however, the case of producing a Fresnel lens I by the above molding method, adjustment of the fine molding conditions in order to reproduce the fine lens surfaces provided on the mold need However, it is often difficult to obtain a lens having no optical distortion. In view of such a situation, the present invention uses a transparent base material as a base material of a Fresnel lens as a kind of mold, and molds only the lens portion with a compatible material to form a lens surface. Excellent reproducibility and no optical distortion
It is intended to provide a method of manufacturing a Fresnel lens . [0007] That is, the frame of the present invention
The manufacturing method of the flannel lens is to form the Fresnel lens.
Active energy ray hardening type resin in the mold with fine grooves for
Inject the oily liquid, and then let the resin liquid shake in the fine grooves of the mold.
Apply pressure to the sheet-shaped transparent base material
While overlapping, gradually overlap from one end of the mold to the other
Then, the resin liquid is cured by irradiating with active energy rays.
The cured product and the transparent substrate are integrated and then removed.
It is characterized by shaping . Base material for Fresnel lens used in the present invention
As the sheet-shaped transparent substrate to be used, any kind of material having high transparency can be used, and examples thereof include glass, acrylic resin, polycarbonate resin, styrene resin, polysulfone resin, polyether sulfone resin or vinyl chloride. Resin etc. can be mentioned. Above all, glass, acrylic resin or polycarbonate resin having a small optical distortion is preferable. The thickness of the sheet-shaped transparent substrate is 2 mm.
It is preferably as thin as the following . This is because when used as a Fresnel lens for a projection screen, the thickness of the transparent substrate is 2 mm or less.
Prevents multiple images, etc., caused by interfacial reflection on the front and back surfaces of the transparent substrate by making it thinner
Can provide excellent image characteristics
That's because. [0012] The present invention is characterized by the use to function the transparent substrate as one of the mold, as the original mold for forming a Fresnel lens, deflection to the inner surface
Has fine grooves for forming the lens part of the flannel lens
If it is a mold (hereinafter referred to as a lens mold), it is made of glass or metal.
Those made of resin or resin can be used. The fine grooves of the Fresnel lens in this case
The shape can be a circular Fresnel lens or a linear Fresnel lens. The cell used in the manufacturing method of the present invention is
It is composed of a transparent base material and a lens mold, and has a peripheral edge
Is usually unnecessary, but it is necessary
Depending on the situation, it may be sealed with a gasket or the like. In the manufacturing method of the present invention,
Active energy for injection and curing to form the lens part
The rugged ray curable resin liquid (hereinafter referred to as a resin liquid) can be cured by active energy rays such as ultraviolet rays and electron beams, and the ultraviolet curable resin liquid is preferable from the viewpoint of handling and manufacturing equipment. As such a resin liquid, an acrylic resin, especially methyl methacrylate as a main component, diols such as ethylene glycol and 1,3-propanediol, triols such as trimethylolpropane, and other polyols are used. Those obtained by copolymerizing a polyfunctional (meth) acrylic acid ester obtained by copolymerizing an ester or the like with acrylic acid and / or methacrylic acid are preferable. Further, as the photopolymerization initiator, for example, benzoyl peroxide, benzoin, benzoin ether or the like is mixed in the resin liquid. A feature of the present invention is that it forms a Fresnel lens.
Inject the resin liquid into the mold that has fine grooves for
So that the resin liquid is completely spread over the fine grooves of the mold.
, While pressing the sheet-shaped transparent substrate on it,
For gradually stacking from one end of the mold to the other
You. Thus, on the resin liquid injected into the mold,
From one end of the lens mold while applying pressure using a transparent substrate
To gradually superimpose the resin solution on the other end,
Completely fit into the fine groove for forming the lens surface of the lens type.
It is possible to disperse the air inside the cell
Prevents the occurrence of lens defects and ensures the lens type
It is possible to accurately transfer the lens pattern of
Things. As a pressurizing method at this time, specifically,
Inject resin liquid into part or all of the lens mold and
Do not pressurize using a roller etc. from the part where the oil is poured.
A method of gradually superimposing transparent substrates is preferable. A lens in which a transparent base material is filled with a resin liquid
It is necessary to adjust the viscosity of the resin liquid in order to suppress the entrainment of air as much as possible when superposed on the mold , which is related to the wetting speed of the transparent substrate and the lens mold ,
It is preferable to set the viscosity of the resin liquid to about 100 to 1000 cps. Furthermore, considering the entrainment of air and the uniformity of thickness, it is necessary to use a resin liquid with a lower viscosity, first fill the resin liquid only in the fine groove portions of the lens mold , and then to form the Fresnel lens. Only fill the resin liquid and press the transparent substrate from one end of the lens mold to the other end.
A method of gradually superposing them is preferable. EXAMPLES The present invention will be described in detail below with reference to examples. Example 1 A glass plate having a total light transmittance of 89% and a thickness of 2 mm was immersed in a silane coupling agent (KBE1003, manufactured by Shin-Etsu Chemical Co., Ltd.) diluted to 1% by weight with methanol at 40 ° C. for 10 minutes. After that, it was dried at 110 ° C. for 5 minutes. Next, a resin solution having the following composition was applied to the glass plate and spread. <Resin composition> Methyl methacrylate 80 parts by weight 1,6-hexanediol diacrylate 18 parts by weight benzoin butyl ether 2 parts by weight And, on this spread resin solution, concave circular Fresnel with a pitch of 10 pieces / mm on the inner surface. A mold having fine grooves that can be formed by a lens was placed, and a force was further applied to the mold to press it, and a high pressure mercury lamp (1000 W) was irradiated for 3 minutes to cure from a position 15 cm away from the glass plate, and the mold was released. . The Fresnel lens obtained was excellent in the formation of the lens surface and the optical characteristics. Example 2 Convex circular Fresnellen with a pitch of 5 lines / mm on the inner surface
The resin with the following composition is placed in a mold with fine grooves that can be formed
After filling with oil, thickness of total light transmittance of 83% on it
While applying pressure to a 2 mm polycarbonate resin substrate
From one end of the mold to the other end gradually,
Was spread over the fine grooves of the mold. [0028] and <Resin Composition> methyl methacrylate 51 parts by weight of dipentaerythritol hexaacrylate 17 parts by weight, mixture α- hydroxy dipentaerythritol pentaacrylate over preparative - isobutyl phenone 3 parts by weight 1,6-hexanediol di 29 parts by weight of acrylate and 15 cm from the polycarbonate resin substrate side
After the resin solution was cured by irradiating a high-pressure mercury lamp (1000W) 2 minutes from a distance, and demolded. The Fresnel lens obtained was excellent in the formation of the lens surface and the optical characteristics. Since the present invention has the constitution as described in detail above, a sheet-like transparent substrate and a Fresnel lens are provided.
The Fresnel lens surface can be accurately formed by using the mold having the fine grooves for forming, and an excellent Fresnel lens without optical distortion can be obtained.

   ────────────────────────────────────────────────── ─── Continuation of front page        Panel     Referee Takehiko Katayose     Judge Yoshiyuki Kawakami     Judge Ichiro Kotani                (56) References JP-A-63-82401 (JP, A)                 JP-A-61-177215 (JP, A)

Claims (1)

(57) [Claims] Has fine grooves to form Fresnel lens
Inject the active energy ray curable resin liquid into the mold, then
So that the resin liquid spreads over the fine grooves of the mold.
While pressing the sheet-shaped transparent substrate on top of the
After gradually overlapping from end to end, the active energy
The resin solution is hardened by irradiating the
It is characterized in that the transparent base material is integrated and then released from the mold.
Fresnel lens manufacturing method.