JP4305090B2 - Lens sheet and manufacturing method thereof - Google Patents

Description

  The present invention relates to a lens sheet represented by a screen for projection TV, a Fresnel lens for overhead projector, and the like, and more particularly to a method for producing a lens sheet formed by curing a photosensitive resin on a substrate. is there.

  Examples of a method for producing a lens sheet having a lens shape on the surface, represented by a Fresnel lens or a lenticular lens, include a pressing method and a casting method.

  However, these production methods have a problem that a molding cycle takes a long time, productivity is low, and manufacturing costs are expensive.

  As a method for solving such a problem, a photopolymer process method (hereinafter referred to as 2P method) is proposed.

The 2P method is a method of molding a resin molded product by injecting an ultraviolet curable resin composition into a mold and then irradiating with ultraviolet rays to cure the resin composition. (See Patent Document 1)
In the 2P method, since the temperature range from the melting temperature of the resin molded at the time of molding to the normal temperature is narrow, the thermal shrinkage is small and the reproducibility of the molding dimensions is good. Therefore, the 2P method is suitable for manufacturing a lens sheet that requires a high-definition lens portion as compared with a pressing method or a casting method.

  The 2P method is typically formed using ultraviolet rays (UV) and ultraviolet curable resins, but can also be formed using an electron beam. Hereinafter, in this specification, an example using an ultraviolet curable resin will be described.

Here, when productivity improvement is considered in the 2P method, it is important to prevent air bubbles from being mixed when injected into the mold.
Japanese Patent Application Laid-Open No. 11-084536.

  The present invention seeks to solve the problems that occur when using the 2P method.

That is, (1) prevention of bubbles from being mixed into the optical ultraviolet curable resin,
(2) Preventing bubbles from being mixed into the lens sheet, which adversely affects the target or appearance.

  The above point is a problem to be solved, and by providing a manufacturing method that eliminates the above point, a lens sheet having optical elements such as a fine Fresnel lens, a micro lens, and a lenticular lens shape can be improved in quality. The purpose is to provide it at low cost.

The method for producing a lens sheet according to the invention of claim 1 comprises:
A lens sheet including a step of transferring and forming fine irregularities on the surface of an ultraviolet curable resin layer formed on a light-transmitting substrate using a mold having a shape obtained by inverting the fine irregularities constituting the lens portion. This manufacturing method is characterized by having the following steps.
(1) A step of smoothing with a roll and flattening after applying an ultraviolet curable resin to a mold.
(2) A step of laminating a translucent substrate on the resin planarized on a mold.
(3) A step of squeezing the laminated body of the translucent base material and the mold from the translucent base material side with a pressure roll so that the resin and the base material are in close contact with each other.
(4) A step of curing the resin on which the fine concavo-convex shape of the molding die is transferred and formed by polymerizing and bonding the cured product of the resin and the substrate by irradiating ultraviolet rays from the translucent substrate side. .
(5) A step of peeling the cured product of the resin and the base material from the mold by polymerization.

  In the step (1), the roll to be used is preferably a roll having a maximum diameter at the center, a minimum diameter at both ends, and a gentle curve from the center to both ends.

  Examples of the lens sheet include a Fresnel lens, a micro lens, and a lenticular lens.

  In the step (1), the bubbles present in the applied resin can be taken out of the effective area of the mold. Moreover, after planarizing the resin in the step (1), by performing the step (2), the bubbles that could not be removed in the step (1) can be pushed out of the effective area of the mold. It becomes easy.

  In the invention of claim 2, by using a roll having a maximum diameter at the center, a minimum diameter at both ends, and a gentle curve from the center to both ends, the bubbles in the resin are molded. It becomes easy to extrude from the effective area to the periphery.

  The ultraviolet curable resin used in the present invention is desirably defoamed in advance under a reduced pressure of 300 Pa or less.

  In the present invention, as the translucent substrate, at least one kind is selected from a translucent glass plate, a translucent resin sheet or film, a translucent and flexible resin sheet or film, and the like. Selected.

  Alternatively, a lens sheet in which at least one shape selected from a lenticular lens, a prism lens array, a Fresnel lens, and the like is formed on at least one surface can be used as the translucent substrate.

  In the present invention, the fine concavo-convex shape constituting the optical article can be selected from a Fresnel lens, a linear Fresnel lens, a lenticular lens, and the like.

  By performing the defoaming step according to the present invention, it is possible to provide a high-quality lens sheet in terms of both appearance and optical performance with minimal bubble mixing.

  Hereinafter, embodiments of the invention will be described. The material used in the present invention is, for example, an acrylic resin, an MS resin, a polycarbonate resin, a polyester resin, a polystyrene resin, a polyolefin resin, a vinyl chloride resin, a polyimide resin, or a sheet made of a mixture of the above resins. It can be appropriately selected from a film, a glass plate and the like.

  Here, considering releasability from the mold, acrylic resin, MS resin, polycarbonate resin and the like having high flexibility are desirable.

  Examples of the ultraviolet curable resin liquid include compositions containing urethane (meth) acrylate and / or epoxy (meth) acrylate oligomer, reaction diluent, photopolymerization initiator, and photosensitizer.

  Hereinafter, the manufacturing method of the present invention will be described with reference to the drawings.

  FIG. 1 is a flowchart showing a lens sheet manufacturing method according to the present invention.

  In the embodiment shown in FIG. 1, an ultraviolet curable resin is optionally applied onto a mold provided with a shape that is a reversal of the fine irregularities constituting the lens sheet, and applied onto the mold. Smoothing and defoaming the cured UV curable resin with a roll, laminating a translucent base material on a coated mold, and using a pressure roll from the translucent base side Polymerization for integrating the step (c) for bringing the material and the resin into close contact, the step (d) for irradiating and curing the ultraviolet ray from the translucent substrate side, and the cured ultraviolet curable resin and the translucent substrate It is a manufacturing method including an adhesion step (e) and a step (f) of releasing the cured ultraviolet curable resin from the mold.

  In the smoothing and defoaming step (b) by the roll, as shown in FIG. 2, the resin is planarized by smoothing the ultraviolet curable resin 2 arbitrarily applied on the mold 1 using the roll 3. This is a step of defoaming by further extruding bubbles existing in the ultraviolet curable resin to the outside of an effective area as a lens sheet.

  As shown in FIG. 3, the roll 3 to be used is a roll having a maximum diameter R at the center, a minimum diameter r at both ends, and a gentle curve from the center to both ends. It is effective on the defoaming mechanism.

  In addition, even if it cannot be completely degassed by using the roll, by slightly flattening the resin, even slightly remaining bubbles can be almost degassed in the step (c) of FIG.

  As shown in FIG. 4, the contact step (c) between the substrate and the resin by the pressure roll is performed by placing the translucent substrate 5 on the ultraviolet curable resin 2 that has been thinly planarized through the step (b). After lamination, the translucent substrate 5 and the ultraviolet curable resin 2 can be brought into close contact with each other by squeezing with the pressure roll 6 from the translucent substrate 5 side.

  Furthermore, it is possible to defoam bubbles remaining in the step (b). At this time, the thickness of the resin layer can be adjusted by appropriately changing the moving speed and pressing force of the pressure roll.

  In the resin liquid curing step (d) and the polymerization adhesion step (e) by ultraviolet rays, as shown in FIG. 5, the ultraviolet curable resin 5 is reacted and cured by irradiating ultraviolet rays from the translucent substrate 4 side. The cured ultraviolet curable resin 2 and the translucent substrate 4 are polymerized and adhered.

  Finally, as shown in FIG. 6, as a base material peeling step from the mold 1, the cured product of the ultraviolet curable resin 5 polymerized and adhered to the translucent base material 4 is peeled off from the mold. An optical article is obtained in which fine irregularities are transferred onto an optical substrate.

The flowchart which shows an example of the manufacturing process of this invention. Explanatory drawing which shows an example of the smoothing by a roll, and a defoaming process (b). Explanatory drawing which shows an example of the roll used for a process (b). Explanatory drawing which shows the contact | adherence process (c) of a base material and resin by a pressure roll. Explanatory drawing which shows the resin hardening process (d) and superposition | polymerization adhesion process (e) by ultraviolet irradiation. Explanatory drawing which shows the base material mold release process (f) from a shaping | molding die.

Claims (2)

A lens sheet including a step of transferring and forming fine irregularities on the surface of an ultraviolet curable resin layer formed on a light-transmitting substrate using a mold having a shape obtained by inverting the fine irregularities constituting the lens portion. The method for producing a lens sheet, comprising the following steps.
(1) A process of smoothing with a roll having a maximum diameter at the center, a minimum diameter at both ends, and a gentle curve from the center to both ends after applying an ultraviolet curable resin to the mold.
(2) A step of laminating a translucent substrate on the resin planarized on a mold.
(3) A step of squeezing the laminated body of the translucent base material and the mold from the translucent base material side with a pressure roll so that the resin and the base material are in close contact with each other.
(4) A step of curing the resin on which the fine concavo-convex shape of the molding die is transferred and formed by polymerizing and bonding the cured product of the resin and the substrate by irradiating ultraviolet rays from the translucent substrate side. .
(5) A step of peeling the cured product of the resin and the base material from the mold by polymerization. The method for manufacturing a lens sheet according to claim 1, wherein the lens sheet is any one of a Fresnel lens, a micro lens, and a lenticular lens.