JPH01285332A - Preparation of lens sheet - Google Patents

Abstract

PURPOSE:To prepare a lens sheet containing no air bubbles, by increasing the coating amount of the first ionizing radiation curable resin of the part forming the resin sump. of a second ionizing radiation curable resin. CONSTITUTION:In the coating amount of a first ionizing radiation curable resin 1 of the part where a second ionizing radiation curable resin 2 is dripped is set so as to become equal to or higher than each of the lens pattern-shaped ridge parts of a mold, a gaseous phase becomes absent between the first and second ionizing radiation curable resins 1, 2 when the second ionizing radiation curable resin 2 is dripped by a dispenser 6 and air bubbles are prevented from remaining in the lens part after coating. When the max. value of the height of each ridge part of the mold is about 150mum, the part where the first ionizing radiation curable resin is thickly applied is further made thick by 30-70mum from the ridge part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is a method of hardening the lens portion of a lens sheet such as a Fresnel lens sheet, a prism lens sheet, a lenticular lens sheet, etc. used in a transmission type screen by ionizing radiation. The present invention relates to a method of manufacturing a lens sheet molded with resin, and particularly to a method of manufacturing a lens sheet that includes an improved resin coating step that prevents air bubbles from being mixed into the lens portion.

[Conventional technology]

Conventionally, this type of lens sheet has been molded by a pressing method, a casting method, or the like. The former press method has poor productivity because it involves a heating, pressurizing, and cooling cycle. In addition, the latter casting method involves pouring monomer into a mold and polymerizing it, which is time-consuming.
Since a large number of molds are required, there is a problem in that the manufacturing cost increases.

In order to solve this problem, an ionizing radiation curing resin such as an ultraviolet ray curing resin or an electron beam curing resin is poured between the mold and the base member, and ionizing radiation such as ultraviolet rays or an electron beam is irradiated. Various ionizing radiation curing resin methods (photopolymer methods) have been proposed in which the resin is cured and polymerized.

For example, in JP-A No. 62-33613 ``Method for manufacturing a screen for a video projector'', ``An ultraviolet curable resin is injected into a lens mold under normal pressure to
The ultraviolet curable resin filled between the ultraviolet curable plate and the mold is cured by passing through the ultraviolet rays transparent plate, and the cured ultraviolet curable resin is released. A proposal has been made with the gist of "forming".

[Problems to be Solved by the Invention] The proposed method has the following problems to be solved.

First, as a means of laminating a UV-transparent substrate on the UV-curable resin injected into the mold, we used vacuum tweezers to stack the UV-transparent substrate on one side of the mold in which the UV-curable resin was injected. It is proposed that the other side be covered with ultraviolet curable resin so as not to trap air bubbles. In order to do so, the control device and drive device become complicated, leading to an increase in cost, and it is impossible to completely cover the air bubbles so as not to contain air bubbles.

Second, when bubbles are mixed into the resin during injection, it is proposed to ``remove them using a pipette, etc.'' However, detecting the presence of bubbles and removing them manually is not productive. Bad and uncertain.

Thirdly, the resin must be defoamed before injection, which requires equipment and time, leading to poor productivity and increased costs.

If such bubbles remain in the lens part, partial defects will occur.
Lens quality will deteriorate.

An object of the present invention is to solve the above-mentioned problems and provide a method for manufacturing a lens sheet that does not contain air bubbles in the lens portion.

[Means to solve the problem]

As a result of various studies, the inventor of the present invention has discovered that the above object can be achieved by improving the coating method of the ionizing radiation-cured resin, and has come up with the present invention.

FIG. 1 is a diagram for explaining the gist of the method for manufacturing a lens sheet according to the present invention.

The manufacturing method of this lens sheet includes a first resin coating step 1.
01, second resin coating step 102, leveling and laminating step 1
03, a resin curing step 104, and a mold release step 105.

The first resin coating step 101 is a step of coating the entire surface of the mold in which the lens pattern mold is formed with a first ionizing radiation-curable resin. This step is a step for uniformizing the wettability of the mold, stabilizing the amount of coating, and promoting defoaming in the next step. Specifically, the roll coating method.

Silk screen method, curtain method, gravure method.

The second resin coating step 102 can be carried out by a squeezing method or the like.
This is a step of forming a resin pool of ionizing radiation-cured resin. The second ionizing radiation-curable resin in this step functions to push out air bubbles that enter between the base member to be laminated and the mold, and to provide adhesiveness to the base member. As a method for forming the resin pool of the second ionizing radiation-cured resin, methods such as a squeezing method, a flow coating method, a roll coating method, and a quantitative separation method can be used.

In the leveling and laminating step 103, an ionizing radiation-transparent base member is placed on the resin pool of the second ionizing radiation-curable resin, and the second ionizing radiation-curable resin is applied to the mold using a pressure roll through the base member. The base member is leveled over the first ionizing radiation-cured resin coated on the second ionizing radiation-cured resin.
This is the step of laminating the t# radiation-cured resin. This process works to push out air bubbles that may have entered between the mold and the base member, and to make the thickness of the molded product uniform.

The resin curing step 104 is a step of curing each of the ionizing radiation-cured resins by irradiating them with ionizing radiation. In this step, both resins are cured by irradiating them with ionizing radiation such as ultraviolet rays or electron beams. At this time, it is preferable to bring the light source as close as possible to the roll pressurizing part.
This is to prevent floating between the mold and the base member and to prevent air bubbles from being reintroduced between them.

The mold release step 105 is a step of releasing each of the ionizing radiation-cured resins from the mold.

Each of the ionizing radiation-curable resin layers can be made of an ultraviolet curable resin, an electron beam-curable resin, or the like. , acrylic acid, acrylamide, acrylonitrile.

A polymerizable oligomer or monomer having a polymerizable vinyl group such as styrene may be used alone or in combination, with additives such as a sensitizer added if necessary.

For such ionizing radiation-curable resins, it is better to use monomers or prepolymers with multifunctional groups in order to improve general mechanical properties such as surface strength and hardness; Preferably used.

Further, this ionizing radiation-cured resin can contain a diffusing agent. Diffusing agents can improve coating suitability and prevent polymerization shrinkage, and
Diffusibility can be imparted. As the diffusing agent, glass, silica, alumina, insoluble plastic, talc, etc. can be used.

As for the ionizing radiation curable resin, the physical properties of the first ionizing radiation curable resin are mold transferability, defoaming property, wettability to the mold, and surface hardening properties, and the physical properties of the second ionizing radiation curable resin are , adhesiveness with the base member, fluidity, mechanical strength, transparency, etc. are important.

In addition, the viscosity of the first ionizing radiation-cured resin is 2
A low viscosity adjusted to 00 centipoise or less is preferable, and the second ionizing radiation curing resin has a viscosity of 500 to 5000 centipoise.
A relatively high viscosity adjusted to centipoise is used. The reason for this is that the first ionizing radiation-curable resin must have a low viscosity because it is applied over the entire surface so as not to contain air bubbles between it and the fine lens pattern mold of the mold.
This is because the second ionizing radiation-curable resin must have a certain degree of viscosity because it is applied while leveling to drive out air bubbles within the resin. By forming the first ionizing radiation-cured resin layer in this way, the defoaming property at the mold interface is further improved.

In this way, by using two layers of resin, each part of the mold, the base member, or the molded lens sheet itself can more effectively fulfill its respective functions, and these functions can be divided into two layers. This allows for a wider range of resin selection.

The selection conditions for each ionizing radiation curable resin will be further explained below. In the case of a lens sheet, it is required that the refractive indexes of both sheets are at least approximately equal. This is because the interface where the first 148 radiation-cured resin and the second ionizing radiation-cured resin are laminated is not necessarily flat.
This is because if the refractive indexes of the two resins are significantly different, uniform light cannot be obtained.

If this relationship is satisfied, the first ionizing radiation curing resin and the second
The ionizing radiation-cured resins may be made of the same material or different materials, and in the case of different resins, combinations with approximately the same refractive index are used, taking into account physical properties. For example, a urethane acrylate resin with good mold reproducibility may be used as the first ionizing radiation curing resin, and an epoxy acrylate resin with good adhesion to the base member may be used as the second ionizing radiation curing resin. . In addition, the resin temperature in the processing steps of the first ionizing radiation-cured resin and the second ionizing radiation-curable resin may be changed, or additives (antifoaming agents) may be added.

leveling agents, etc.), solvents, etc., or
First! The wettability to the mold, fluidity, viscosity, etc. may be suitably adjusted by changing the blending ratio of monomers, oligomers, etc. of the radiation-curing resin and the second 1-layer M radiation-curing resin. When adjusting using a solvent, it is desirable to volatilize the solvent after coating in order to prevent resin shrinkage, solvent deterioration, etc.

Furthermore, a diffusing agent can be included in both or one of the first ionizing radiation-curable resin and the second ionizing radiation-curable resin.

The base member is a sheet or film that is solvent resistant and transparent to ionizing radiation, and is made of i! Those with a high i-pass rate are preferably used. In addition, this base member preferably has adhesive properties to ionizing radiation-cured resins and has high mechanical strength.
A primer layer of urethane or the like that improves adhesiveness can be provided.

Next, the method for manufacturing a lens sheet according to the present invention will be explained in more detail, focusing on the resin coating process.

FIGS. 2 and 3 are diagrams for explaining the resin coating step of the method for manufacturing a lens sheet according to the present invention.

In the present invention, the amount of the first ionizing radiation curable resin applied to the portion where the resin pool of the second ionizing radiation curable resin is formed is increased, specifically, the amount of the first ionizing radiation curable resin is applied higher than the groove depth of the mold. be.

The reason for this is that if the applied amount of the first ionizing radiation curing resin 1 is small and is below the height of the peak of the lens pattern mold of the mold 4 (Fig. 2 (a)), the second When the ionizing radiation curing resin 2 of
ionizing radiation curing resin 1 and second ionizing radiation curing resin 2
Since a gas phase 7 exists between the two (Fig. 2, et al.)), even if pressure is applied to remove the bubbles in the second resin coating step 102 described above, the gas phase 7 cannot be pushed out, and small bubbles 7a remain on the lens portion even after coating. There was a high possibility that this would occur (Figure 2 (C)).

As in the present invention, the amount of the first 1ft #radiation curable resin 1 on the part where the second ionizing radiation curable resin 2 is dropped is set to be equal to or higher than the height of the peak of the lens pattern mold of the mold 4. For example (FIG. 3(a)), when the second ionizing radiation curing resin 2 is dropped by the dispenser 6, a gas phase is created between the first ionizing radiation curing resin 1 and the second ionizing radiation curing resin 2. No longer existed (Figure 3 (C)), and no air bubbles remained on the lens portion after coating (Figure 3 (C)).

When the maximum height of the peak of the mold is about 150 μm, the first ionizing radiation-curable resin can be applied thickly to the area where it is further thickened by 30 to 70 μm from the peak of the mold.

In addition, in the first resin coating step 101, when applying the first ionizing radiation curing resin 1 to the entire surface of the mold 4, if the coating thickness is made thicker than the depth of the mold over the entire surface, especially When the viscosity of the first ionizing radiation-curable resin l is high, the wettability between the mold 4 and the first ionizing radiation-curable resin l becomes poor, and since the resin 1 has a high viscosity, it is thick enough to prevent air bubbles from being mixed in. Difficult to apply.

In addition, in an attempt to increase the wettability of the mold 4 and the ionizing radiation-cured resin l, and to achieve a thick coating without the inclusion of air bubbles, the first
A solvent was added to radiation curing resin 1 to reduce the viscosity to 50.
If it is dropped below centiboise, the added solvent may have an adverse effect on the physical properties if it remains after molding, so it is necessary to volatilize the solvent. For this reason, the process for removing the solvent takes a long time, resulting in poor productivity.

Furthermore, if the first ionizing radiation curing resin is applied thickly to the entire surface, the amount of application will increase and the amount of resin used will increase.In addition, the overflowing excess resin must be post-processed, which increases manufacturing costs. Connect.

The method for manufacturing a lens sheet according to the present invention can be applied to Fresnel lens sheets, prism lens sheets, Lentsch error lens sheets, etc., and can also be applied to optical cards, optical disks, holograms, etc. that have fine patterns on their surfaces. The same can be applied to

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

FIGS. 4 to 8 are diagrams showing an embodiment of the method for manufacturing a lens sheet according to the present invention.

In each figure, l is the first UV curing resin 52 and the second U
3 is a base member, 4 is a mold, 5 is a pressure roll, and 6 is a UV light source.

First, as shown in Fig. 4, the height and width are 1 m, and the pinch is 0.
The first UV curing resin 1 of the mold 4 having a 1 mm Fresnel lens-shaped lens pattern has a refractive index of 1.
49. A urethane acrylate resin with a viscosity of 100 centivoise was applied to a thickness of approximately 50 μm from the bottom of the mold (the fourth
In Figure (a) t+), coat the entire surface and apply only the part IA surrounded by the two-dot chain line about 50 μm further from the peak of the mold.
(Figure 4(a) L8) The thickness was increased.

To apply in this way, as shown in Figure 5(a),
After uniformly coating the entire surface of the mold 4 using a roll coater 8 so that the thickness is 50 μm from the crest of the mold, a squeegee 9 is used to coat the entire surface, as shown in FIG. 5(b) (C). The thickness was scraped off except for the portion IA surrounded by the dotted chain line. Note that the upper and lower sides of the squeegee 9 are set 5 to 10 times higher than the head of the mold 4 using a timing sensor or the like.
Do this when it is lowered by cm.

Next, as shown in FIG. 6, the second UV curing resin 2 is
In the part IA of the first UV curing resin 1 surrounded by the two-dot chain line,
A resin reservoir of 0.5 g/C- was formed by the flow coating method. This second UV curing resin 2 has a refractive index of 1
．． 49. An epoxy acrylate resin whose viscosity was adjusted to 1500 centivoise was used.

After forming the resin reservoir in this way, as shown in FIG. 7, a 3.0 mm thick transparent acrylic plate coated with a vinyl chloride/vinyl acetate copolymer primer was laminated as the base member 3. Pressure rolls 5, 5 at a speed of 50c
Pressure was applied by transferring at m/min. At this time, air bubbles that enter between the mold 4 and the base member 3 are pushed out at a portion indicated by A in the figure. At this time, ultraviolet light (UV) of 160 W/cm was irradiated from the base member 3 side using the UV light source 6 to cure the second UV curable resin 2 of the first UV curable resin color.

Finally, as shown in FIG. 8, the mold 4 was depressurized and released to obtain a Fresnel lens sheet. This Fresnel lens sheet is composed of a first U-cured resin 1 on the tip side of the lens portion and a second UV-cured resin 2 on the base side, and further includes:
The base members 3 were laminated. In this Fresnel lens sheet, no air bubbles were mixed in the part where the second UV curing resin 2 was dropped.

FIG. 9 and FIG. 1O are diagrams showing other embodiments of the method for manufacturing a lens sheet according to the present invention.

This example shows an example in which the second UV curing resin 2 is applied in a U-shape in order to eliminate molding defects around the lens sheet.

In this case as well, after applying the first U-cured resin l uniformly in advance with a roll coater, use a narrow squeegee 9 to scrape off the resin l, as shown in FIG. By leaving a portion, only the portion 1B of the first UV curing resin 1 surrounded by the two-dot chain line was made thicker.

Further, the second UV curing resin 2 was applied thereon in a U-shape. Second UV curing tree 11! li2 to the left end 70
It was manufactured in the same manner as in the example shown in FIG. 1, except that resin reservoirs of 20 g each were formed at both the upper and lower ends.

Similarly to the above, no air bubbles were found in the part where the second UV curable resin 2 was dropped.

〔Effect of the invention〕

As explained in detail above, according to the present invention, since the amount of the first ionizing radiation-curable resin applied to the portion forming the resin pool of the second ionizing radiation-curable resin is increased, the second ionizing radiation-curable resin
A large amount of air bubbles are no longer mixed in when dropping the ionizing radiation-cured resin, making it possible to manufacture a lens sheet that does not contain air bubbles.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the gist of the method for manufacturing a lens sheet according to the present invention. FIGS. 2 and 3 are diagrams for explaining the resin coating step of the method for manufacturing a lens sheet according to the present invention. 4 to 8 are diagrams showing an embodiment of the method for manufacturing a lens sheet according to the present invention. FIGS. 9 and 10 are diagrams showing other embodiments of the method for manufacturing a lens sheet according to the present invention. FIG. 1... First UV curing resin 2... Second UV curing resin 3... Base plate member 4... Molding mold 5...
Roll 6...UV light source patent applicant Dai Nippon Printing Co., Ltd. Agent Patent attorney Sickle 1) Second son Figure 1

Claims (1)

[Claims] A first ionizing radiation curable resin is applied to the entire surface of the mold in which the lens pattern mold is formed, and a second ionizing radiation curable resin is applied onto the first ionizing radiation curable resin coated on the mold. forming a puddle, stacking the base member on the resin puddle of the second ionizing radiation-cured resin, and layering it on the first ionizing radiation-curable resin while leveling the second ionizing radiation-cured resin with a pressure roll; , a method for manufacturing a lens sheet comprising irradiating each of the ionizing radiation-curable resins with ionizing radiation to cure them, and releasing each of the ionizing radiation-curable resins from the mold, the resin of the second ionizing radiation-curable resin; A method for manufacturing a lens sheet, characterized in that the amount of the first ionizing radiation-curable resin applied is increased in a portion where a pool is formed.