JPH06118207A - Lens sheet - Google Patents

Abstract

(57) [Summary] [Object] To obtain an excellent lens sheet that can sufficiently exhibit the original optical characteristics of the lens pattern formed on the lens sheet, and is free from bubbles and uneven thickness. [Structure] A transparent base material 1 and a lens portion 2 formed on the transparent base material 1 and made of an active energy ray curable resin. The lens portion 2 is made of a first active energy ray curable resin. The tip layer 3 and the lens base layer 4 formed of the second active energy ray-curable resin, and the interface 5 between the lens tip layer 3 and the lens base layer 4 has a relatively smooth surface. Lens sheet characterized by.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens sheet such as a Fresnel lens or a lenticular lens used for a projection screen used as a screen of a projection television or a microfilm reader.

[0002]

2. Description of the Related Art As a method for manufacturing a lens sheet such as a Fresnel lens or a lenticular lens, a transparent resin material such as an acrylic resin, a polycarbonate resin, a vinyl chloride resin or a styrene resin is used, and these resins are injection molded. There are known a press molding method in which a resin plate and a lens mold are brought into contact with each other and the lens pattern of the lens mold is transferred by heating and pressing the resin plate, and a direct cutting method in which the resin plate is directly cut. Recently, a method of injecting an active energy ray-curable resin into a lens mold and then irradiating the resin with an active energy ray to cure the resin has been proposed.

However, in the injection molding method, it is difficult to mold a large-sized molded product, and it can be used only for molding a relatively small-sized molded product. Further, in the press molding method, since the heating and cooling cycle of the resin plate and the molding die takes a long time, a large number of molding dies are required for mass production of the resin molded product, and in order to manufacture a large resin molded product. Costs a huge amount of production equipment.

On the other hand, the method using the active energy ray-curable resin composition can shorten the molding time and improve the productivity, but has a problem such as entrainment of bubbles or the like when the resin composition is injected into the lens mold. In order to solve this, it is necessary to separately perform a defoaming treatment or to slowly inject, which is not sufficient for mass production. In particular, when manufacturing a Fresnel lens having a concentric lens pattern, bubbles are likely to be generated because bubbles are trapped in the groove due to the concentric lens-shaped pattern shape, and bubbles once generated can be easily removed. However, there is a problem in that it is not possible to cause lens defects due to air bubbles. As a method for preventing the generation of such bubbles, as described in Japanese Patent Application Laid-Open No. 1-192529, a low viscosity UV-curable resin (first resin) is applied to a lens mold, and then a relatively high A method has been proposed in which a UV curable resin (second resin) having a viscosity is injected, and transparent substrates are superposed and irradiated with UV rays to be cured and then demolded.

[0005]

However, the lens sheet manufactured by such a method has a second resin layer in the convex portion of the lens due to shrinkage during polymerization as shown in the partial sectional view of FIG. 28 is the first resin layer 27
As a result, the interface 29 becomes arcuate. Thus, the first resin layer 28 and the second resin layer 2
When the interface 29 with 7 is formed in an arc shape, the interface 29 acts as a lens and the original optical characteristics of the lens sheet are impaired.

If the first resin applied to the lens mold has a raised portion in the manufacturing process, it remains as uneven thickness of the lens sheet even after the second resin is injected and cured. There is also a problem that it causes deterioration of lens quality such as image distortion. Therefore, an object of the present invention is to provide a high-quality lens sheet having excellent optical characteristics and free from lens defects and thickness unevenness due to bubbles and the like.

[0007]

Means for Solving the Problems In view of the above problems of the prior art, the inventors of the present invention have earnestly studied a lens sheet using an active energy ray-curable resin, and as a result,
The present invention has been reached. That is, the lens sheet of the present invention comprises a transparent base material and a lens portion formed on the transparent base material and made of an active energy ray curable resin, and the lens portion is made of a first active energy ray curable resin. And a lens base layer formed of a second active energy ray curable resin, wherein the interface between the lens tip layer and the lens base layer is a relatively smooth surface. To do.

FIG. 1 shows a partial sectional view of the lens sheet of the present invention. In the figure, 1 is a transparent base material, and a lens portion 2 made of active energy rays is formed on the transparent base material 1.
The lens portion 2 is made of a first active energy ray-curable resin and forms a lens tip layer 3 that forms a lens tip portion, and a lens base layer 4 that is made of a second active energy ray-curable resin and forms a lens base portion. It has a two-layer structure, and the interface 5 between the lens tip layer 3 and the lens base layer 4 is formed as a relatively smooth surface.

The transparent base material 1 constituting the lens sheet of the present invention is not particularly limited in thickness and material, but it is not preferable that the light transmittance is remarkably lowered due to coloring or turbidity. Examples of materials that can be used include plastics and glass, and specifically include acrylic resins, polycarbonate resins, polyester resins, polystyrene resins, fluororesins, polyimide resins, copolymers or polymer alloys of these resins, and the like. The thickness of the transparent substrate 2 is preferably 3 mm or less from the viewpoint of the permeability of active energy rays and the handling property. In particular, when it is used as a lens for a projection screen such as a Fresnel lens or a lenticular lens, it is 1 m in view of optical characteristics such as multiple images and rainbow color spots.
It is preferably m or less.

The first active energy ray curable resin forming the lens tip layer 3 and the second active energy ray curable resin forming the lens base layer 4 of the present invention may have the same composition or different compositions. It may be. Even if they have the same composition, it is possible to use those having different physical properties such as viscosity. For example, a resin having good reproducibility of a lens type lens pattern can be used as the first resin, and a resin having good adhesion to a transparent substrate can be used as the second resin. In particular, the first resin has a viscosity of 10 when injected.
It is preferably as low as 0 cps or less and has high transparency after curing. This is because if the viscosity at the time of injection exceeds 100 cps, bubbles are more likely to be generated due to factors such as capitation when passing through the injection nozzle. Moreover, since the curability in the presence of air is inferior and the adhesiveness with the second resin composition can be improved, those containing a methacrylate component as a main component are preferable.

As the first and second active energy ray curable resins, polyvalent acrylates and / or polyvalent methacrylates (hereinafter, referred to as polyvalent (meth) acrylates), monos are used in view of handling property and curability. Those containing acrylate and / or monomethacrylate (hereinafter referred to as mono (meth) acrylate) and a photopolymerization initiator by an active energy ray as a main component are preferable. Typical polyvalent (meth) acrylates include polyol poly (meth) acrylate, polyester poly (meth) acrylate, epoxy poly (meth) acrylate, urethane poly (meth) acrylate, and the like. These are used alone or as a mixture of two or more kinds. Also,
Examples of mono (meth) acrylates include monoalcohol mono (meth) acrylic acid esters and polyol mono (meth) acrylic acid esters. In the latter case, it is considered to be the influence of free hydroxyl groups. However, since the releasability from the metal mold is deteriorated, it is better not to use a large amount when using the metal mold. Also, since (meth) acrylic acid and its metal salt have high polarity, it is better not to use a large amount when using a metal mold.

In the present invention, the active energy ray-curable resin does not interfere with the curing of additives such as antioxidants, ultraviolet absorbers, anti-yellowing agents, bluing agents, pigments and diffusing agents, if necessary. You may mix | blend in the range. In the lens sheet of the present invention, it is important that the interface 5 between the lens front end layer 3 and the lens base layer 4 is formed with a relatively smooth surface, which allows the original pattern obtained by the lens pattern of the lens sheet to be obtained. The optical characteristics can be sufficiently exhibited. Since such an interface 5 forms an uneven fine lens pattern on the lens sheet itself, some unevenness formed by contraction during polymerization of the active energy ray-curable resin cannot be avoided, but In the invention, slight unevenness at the interface is not a problem as long as it does not significantly impair the optical characteristics of the lens sheet. That is, the relatively smooth surface in the present invention means the extent to which the original optical characteristics of the lens sheet are not significantly impaired. More specifically, the variation width of the unevenness of the interface 5 is 20
The range may be 0 μm or less, preferably 100 μm or less.

As described above, the lens sheet in which the interface 5 between the lens front end layer 3 and the lens base layer 3 is formed from a relatively smooth surface, for example, is smoothed after the first resin is injected into the lens mold. Or by irradiating with active energy rays to subsequently cure or semi-cure the first resin. Hereinafter, the method for producing the lens sheet of the present invention using the smoothing treatment and irradiation of the first resin with active energy rays will be described in detail with reference to the drawings.

FIG. 2 is a schematic view showing another method for injecting the first active energy ray-curable resin of the present invention, in which the lens mold 6 having a lens pattern is installed at an inclination and the upstream end thereof. The active energy ray curable resin liquid 8 is injected from the above using the injection nozzle 7. The resin liquid 8 is supplied to the injection nozzle 6 from the resin liquid tank through the metering pump 9.
When injecting the resin liquid 8, care should be taken not to make the flow rate of the resin liquid 8 extremely fast, and an excessive amount of resin liquid of 10 Amm ³ or more may be flowed down when the area of the lens mold 6 is Amm ^2. desirable. By allowing the excess resin liquid 8 to flow down in this way, the bubbles generated at the initial stage of injection can be washed away, and the bubbles can be prevented from remaining in the lens mold 6. The surplus resin liquid 8 can be returned to the resin liquid tank and used again for injection after being subjected to treatments such as defoaming and filtration. The inclination angle 10 of the lens mold 6 is preferably 15 degrees or less in consideration of the viscosity of the resin liquid, the flow rate, and the like.

The first active energy ray-curable resin can be injected by using an injection nozzle such as a multi-hole nozzle or a slit nozzle while moving the injection nozzle according to the shape of the lens mold. In this case, the viscosity of the resin liquid to be used and the L / D of the nozzle hole portion (L is the nozzle) so that the Reynolds number calculated from the flow velocity at the nozzle hole portion of the injection nozzle is not extremely separated from the laminar flow region. Hole length,
D represents the diameter. ) Or slit width needs to be determined.

As the lens mold 6 used in the present invention,
An appropriate lens pattern is formed on the inner surface, made of glass, metal such as aluminum, brass, steel, etc., synthetic resin such as silicon resin, urethane resin, epoxy resin, ABS resin, fluorine resin, polymethylpentene resin, etc. The thing etc. can be used. Further, such a material may be mixed with various metal powders or may be plated.

Lens mold 6 which has undergone the first resin injection step
Performs the smoothing process outlined in FIG. The lens mold 6 in which the first resin 8 was poured so as to rise from the lens pattern portion was used as a resin liquid 8 by a smoothing device provided with a blowing nozzle 12 that blows out a gas by a carrying device 11.
Is only smoothed so that only the lens pattern concave portion 14 of the lens mold 6 remains and the liquid surface of the resin liquid 8 becomes smooth. In the smoothing device, the blow-out nozzle 12 having a blow-out port in which the blown-out gas spreads little and has no unevenness is a blow-out fan 16
Is installed and connected to the outlet nozzle 12
The excess resin liquid 15 is removed by the air blown out from the surface to smooth the resin. The surplus resin 15 may be overflowed from the peripheral portion of the lens mold 6, recovered from the resin liquid receiver installed around the lens mold 6, and subjected to treatments such as defoaming and filtering, and then used for injection again. it can.

Further, in the smoothing device of the present invention, as shown in FIG. 4, a suction nozzle 13 having a slit having a width of about 5 mm at a position facing the blowout nozzle 12 is connected to a suction fan 17 and installed. However, the air and the resin liquid 15 blown out from the blowout nozzle 12 can be sucked. By installing such a suction nozzle 13, the excess resin liquid 15 scattered by the air blown from the blow nozzle 12 is sucked from the suction nozzle 13, and the excess resin liquid 15 in the form of fine particles is scattered. It is possible to prevent the resin liquid that has been smoothed by the above method from adhering to the surface. Excessive dispersion of the resin liquid 15 causes unevenness in the thickness of the lens sheet, so it is preferable to install the suction nozzle 13 side by side, but it is also possible to prevent it by controlling the moving speed of the blowing nozzle 12 and the blowing amount of air. it can.

After the smoothing step, the first hardening step is performed. Lens mold 6 obtained by smoothing the injected first resin liquid 8
Is irradiated with active energy rays by the active energy ray irradiation device, and the injected first resin liquid 8 is cured or semi-cured. Examples of the active energy rays include particle rays such as electron rays and ion rays, electromagnetic waves such as γ rays, ultraviolet rays, visible rays and infrared rays, and ultraviolet rays are preferable from the viewpoint of curing speed and production equipment. As the active energy ray irradiating device, when irradiating ultraviolet rays, an ultraviolet lamp such as a high pressure mercury lamp, a chemical lamp, or a germicidal lamp can be used.

The active energy ray irradiated in the first curing step has a cumulative dose of 320 to 390 nm of 1
It is preferably 0 to 1000 mJ / cm ² . This is because when the irradiation dose is less than 10 mJ / cm ² , the curing reaction of the resin does not proceed, which causes thickness unevenness and bubble generation due to the injection of the second resin. On the contrary, the irradiation dose is 1000m
This is because if it exceeds J / cm ² , the adhesiveness to the second resin may be deteriorated, or coloring may occur due to irradiation with active energy rays after the injection of the second resin. By irradiating the active energy ray with the irradiation amount in this range, only the inner surface of the first resin can be cured or semi-cured, so that the adhesiveness with the second resin is excellent and its interface is also optical. Can be made uniform.

The first curing step as described above may be carried out if necessary, and after the smoothing step, the second resin injection step may be directly carried out without the curing step. However, when injecting the second resin without curing or semi-curing the first resin, the first resin moves while being pressed by the second resin, and the first resin and the second resin are moved. There is a possibility that bubbles may be generated due to the lens-shaped shape with the resin, or that the interface between the first resin layer and the second resin layer cannot form a relatively smooth surface. It is preferable to inject the second resin after performing the steps.

A second resin injection step is performed on the lens mold 6 after the smoothing step or the first curing step. In Figure 5,
The schematic of the 2nd resin injection process was shown. The roll coater 1 is used to inject the second active energy ray-curable resin liquid 18.
It is injected with a constant thickness on the first resin layer 8 using a constant thickness coating device such as 9. Note that, instead of the roll coater 19, another constant thickness coating device such as a silk screen printing machine may be used, or a porous nozzle or a slit nozzle may be used as in the case of the first resin liquid injection. Good. When the second resin liquid 18 having a relatively high viscosity is used, a resin pool of the second resin liquid 18 is formed on the first resin layer 8 at the end of the lens mold 6, It is also possible to apply it while spreading it with a pressure roll through the transparent substrate 2. Furthermore, it is also possible to prepare the transparent base material 2 to which the second resin has been applied in advance and to superpose it on the first resin layer 8. Moreover, when injecting a relatively low viscosity liquid as the second resin liquid, a smoothing step may be performed as in the case of performing after the first resin injection.

The transparent base material 2 is superposed on the lens mold 6 in which the second resin has been injected, as schematically shown in FIG. The end 21 of the transparent substrate 2 is aligned with the end 20 of the lens mold 6, and the rolls 22 are used to overlap each other. in this case,
The excess resin liquid overflows from the direction of movement of the roll or the peripheral portion, is collected from the excess resin liquid receiver 23 installed below the lens mold 6, and is used for re-injection after being subjected to treatments such as defoaming and filtering. can do. Transparent substrate 2
Are preferably arranged along the roll 22 and overlapped. The roll 22 used has a diameter of 2
A size of about 50 mm or less is preferable. When the transparent substrate 2 is arranged away from the roll 22 or when the roll 22 having a diameter of more than 250 mm is used,
The convex portion formed on the surface of the second resin liquid 18 and the transparent substrate 2 are
There is a possibility that bubbles may be generated between the transparent base material 2 and the resin liquid 18 by contacting and overlapping the transparent base material 2 and the second resin liquid 18 by the roll 22 at a position deviating from the original overlapping position. Because there is.

After the transparent substrates 2 are overlaid, the transparent substrate 2
The resin liquid is cured by irradiating an active energy ray from above. In this curing step, the dose of active energy rays is sufficient to completely cure the resin liquid, and is appropriately determined depending on the type of active energy ray-curable resin used. After the resin is hardened, the end of the transparent substrate 2 is held and released from the lens mold 6 to obtain a lens sheet.

[0025]

EXAMPLES Examples of the present invention will be specifically described below with reference to FIGS. As shown in FIG. 7, the thickness is 3 m
A lens mold 6 having a Fresnel lens pattern formed on a brass plate having a size of 1200 mm × 800 mm and having a size of m was prepared. When the lens mold 6 is placed on the frame 24,
The leg 25 was erected so that it had a degree of inclination. Further, the frame 24 having one open side and the resin liquid receiver 23 were installed around the lens mold 6 such that the open side of the frame 24 was located on the lower side and the lower end of the frame 24 was in contact with the resin liquid receiver 23.

The injection nozzle 7 has a length of 1300 mm.
SUS304TP15A stainless steel tube with a diameter of 1m
m nozzle holes provided at intervals of 10 mm were used, and a gear pump 9 for supplying the first ultraviolet curable resin liquid was connected to the line filter 26. Lens type 6
The first resin liquid 8 was injected into the lens mold 6 at an injection speed of 20 liters / minute while moving the injection nozzle 7 from the upstream side to the downstream side of the lens mold 6 at an interval of 3 mm.

The composition of the first ultraviolet curable resin was as follows, and the viscosity at room temperature was 40 cps. <Resin composition> Funkryl FA-321M 50% by weight (Hitachi Chemical Co., Ltd., ethylene oxide modified bisphenol A dimethacrylate) Diabeam 4117 10% by weight (Mitsubishi Rayon Co., bisphenol A-based acrylate) Diabeam 2106 40% by weight (Mitsubishi Rayon Co., Tetrahydrofurfuryl acrylate) Darocur 5117 1.5% by weight (Merck Japan Co., 2-hydroxy (relative to the sum of the above resins) -2-methyl-1-phenylpropan-1-one) Then, As shown in FIG. 8, a blowing nozzle 12 that blows air in a slit shape having a length substantially equal to the width of the lens mold 6.
A smoothing device having the suction nozzle 13 and the suction nozzle 13 was prepared.
As the blow-out nozzle 12, an air nozzle (manufactured by Kikuchi, DN
Four (-300 type Daico air nozzles) were installed, and the suction nozzle 7 was installed at a position facing this.

At a position 5 mm away from the tip of these nozzles, the lens mold 6 is moved at a speed of 2 m / min by the conveying device 11, and the first resin liquid 8 is injected only into the lens pattern concave portion 14 of the lens mold 6. It was smoothed as follows. A ring blower 16 is connected to the blow-out nozzle 12, air is sent at 1200 mmAq, and a vacuum cleaner 17 is connected to the suction nozzle 13 to remove the excess resin liquid 1.
5 was aspirated.

After smoothing, in the first ultraviolet irradiation device in which eight chemical lamps are arranged in parallel, the distance between the chemical lamp and the lens mold 6 is 100 mm, and the lens mold is at a conveying speed of 3 m / min. 6 was passed through and the first resin liquid was cured so as to be in a semi-cured state. At this time, 320-
The cumulative UV irradiation dose of 390 nm is 150 mJ / cm ^2.
Met. On the semi-cured first resin layer, a second resin liquid, which is the same as the first resin liquid, is applied to a substantially uniform thickness by using a Van Koran Squeegee CB-60-A (mesh industry Co., Ltd. quantitative coating device). It was spread so that it would be. Then, as shown in FIG. 9, as the transparent substrate 2, an acrylic resin sheet (Acrylite # 000 manufactured by Mitsubishi Rayon Co., Ltd.) having substantially the same size as the lens mold 6 and a thickness of 1 mm was used. Was placed in contact with the end of the lens mold 6, and the roll 22 was lowered while being held so as to be arranged along the roll 22. The roll 22 is moved from one end to the other end of the lens mold 6 at a speed of 1 m / min to move the transparent substrate 2 to the second position.
Was superposed on the resin liquid of. The excess resin liquid that overflowed was collected in the resin liquid receiver 23 installed below the lens mold 6. Then, when the roll 22 moves to the other end of the lens mold 6, the roll 22 is lifted and the superposition is completed. As the roll 22, a metal roll having a diameter of 160 mm and an NBR sheet having a JIS rubber hardness of 40 degrees was wound.

The lens mold 6 in which the transparent base materials 2 are superposed is
The resin solution was completely cured by irradiating it with ultraviolet rays using an ultraviolet ray irradiating device in which three ultraviolet ray lamps each having an irradiation intensity of 6.4 kW and an irradiation intensity of 80 W / cm were arranged. After the curing was completed, the lens 6 was released from the mold to obtain a Fresnel lens sheet. The obtained Fresnel lens sheet has a transparent base material 1 as shown in FIG.
A lens part 2 having a two-layer structure, which is composed of a lens tip layer 3 made of a first ultraviolet curable resin and a lens base layer 4 made of a second ultraviolet curable resin, is formed on the upper portion of the lens tip layer 3 and the lens base layer 4. The interface 5 with and is formed from a relatively smooth surface with unevenness of 55 μm or less, no bubbles remain in the lens, and uniform high quality without thickness unevenness.
Its optical characteristics were also excellent.

[0031]

Since the lens sheet of the present invention is constituted as described above in detail, the original optical characteristics of the lens pattern formed on the lens sheet can be sufficiently exhibited, and It is excellent in that it does not generate air bubbles or has uneven thickness, and is particularly suitable for a Fresnel lens or a lenticular lens used in a projection screen or the like.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a lens sheet of the present invention.

FIG. 2 is a schematic view showing a manufacturing process of the lens sheet of the present invention.

FIG. 3 is a schematic view showing a manufacturing process of the lens sheet of the present invention.

FIG. 4 is a schematic view showing a manufacturing process of the lens sheet of the present invention.

FIG. 5 is a schematic view showing a manufacturing process of the lens sheet of the present invention.

FIG. 6 is a schematic view showing a manufacturing process of the lens sheet of the present invention.

FIG. 7 is a schematic view showing a manufacturing process of an example of the present invention.

FIG. 8 is a schematic view showing a manufacturing process of an example of the present invention.

FIG. 9 is a schematic view showing a manufacturing process of an example of the present invention.

FIG. 10 is a partial cross-sectional view of a conventional lens sheet.

[Explanation of symbols]

 1 ... Transparent base material 2 ... Lens part 3 ... Lens tip layer 4 ... Lens base layer 5 ... Interface 6 ... Lens type 7 ... Injection nozzle 8 ... 1st Active energy ray curable resin 9 ... Metering pump (gear pump) 10 ... Lens type inclination angle 11 ... Conveying device 12 ... Blow-out nozzle 13 ... Suction nozzle 14 ... Lens pattern concave portion 15.・ ・ Excess resin 16 ・ ・ ・ Blow-out fan (ring blower) 17 ・ ・ ・ Suction fan (vacuum cleaner) 18 ・ ・ ・ Second active energy ray curable resin 19 ・ ・ ・ Roll coater 20 ・ ・ ・Lens mold end 21 ... Transparent base material end 22 ... Roll 23 ... Resin liquid receiver 24 ... Frame 25 ... Leg 26 ... Line filter 27 ... First resin layer 28 ... Second Resin layer 29 ... Interface

Claims (1)

[Claims] 1. A transparent substrate, and a lens portion formed on the transparent substrate and made of an active energy ray-curable resin,
The lens portion includes a lens tip layer formed of a first active energy ray curable resin and a lens base layer formed of a second active energy ray curable resin, and the lens tip layer and the lens base layer. A lens sheet having an interface with a relatively smooth surface.