JP2000071257A - Manufacturing method of molded products - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin molding die having high dimensional accuracy using a general-purpose thermoplastic resin, and to provide a method for manufacturing a molded article such as a lens sheet in a simple process using the same. thing. SOLUTION: A resin mold 3 is produced by hot-pressing a mold 2 having an uneven pattern on one surface of a thermoplastic resin sheet 1 and transferring the uneven pattern of the mold 2 to the thermoplastic resin sheet 1, Using the resin mold 3, a concave / convex pattern is transferred to the photocurable resin 6, and the photocurable resin 6 is cured to produce a molded product. In particular, a material having a wetting index of 40 or less forms a thermoplastic resin sheet surface to which a mold uneven pattern is transferred, and furthermore, a material that forms a thermoplastic resin sheet surface to which the mold uneven pattern is transferred. The difference between the wetting index and the wetting index of the cured photocurable resin is preferably 4 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a molded article having a fine uneven surface such as a lens sheet.

[0002]

2. Description of the Related Art As a method of manufacturing a lens sheet which is required to mold fine irregularities with high precision, such as a Fresnel lens sheet, a lenticular lens sheet, a prism lens sheet, etc., there are a hot press molding method and a casting method. And an injection molding method. recently,
Because of its features such as low manufacturing cost and suitability for manufacturing large lens sheets, lens sheets are also manufactured by a photopolymer method (2P method) using an ultraviolet curable resin.

[0003] A method of manufacturing a lens sheet by the 2P method will be described with reference to an example of a method of manufacturing a Fresnel lens sheet for a rear projection screen. An NC lathe is used to cut a V-shaped groove opposite to the Fresnel lens shape into a metal plate. Then, a mold is manufactured, and the shape is accurately transferred to an ultraviolet curable resin to form a Fresnel lens sheet. In the Fresnel lens sheet for rear projection screen, the pitch of the lens pattern is 100 μm
It has a depth of up to 150 μm, and there are also problems such as cutting accuracy and bite wear. One large mold such as a 50-inch Fresnel lens sheet is required. The time required for cutting with an NC lathe is long. In order to increase the productivity per hour of the production line of the Fresnel lens sheet by the 2P method, it is necessary to prepare a plurality of dies, and the yield at the time of cutting the dies is not necessarily high.
The cost of the mold in the manufacturing cost of the Fresnel lens sheet is large. For this reason, it is desired to reduce the mold cost for molding one Fresnel lens sheet.

[0004] In order to reduce the cost of the mold, there is a technique for producing a second molding resin mold having the same dimensions as the mold from the mold via the first resin intermediate mold (Japanese Patent Laid-Open No. 1-174418). Gazette). According to this technique, since a large number of molding resin dies can be obtained from a single mold, the cost of the mold per molded product can be reduced.

[0005]

SUMMARY OF THE INVENTION However, Japanese Patent Laid-Open Publication No. 1-1
In the method described in Japanese Patent No. 74418, the dimensional accuracy may be reduced due to passing through a number of molding steps of a mold, a resin intermediate mold, and a resin mold for molding. There is a problem that the selection range of the thermosetting resin is narrow and the material cost is high. Furthermore, there remains a problem that the yield is poor due to the complicated process and it is difficult to reduce the cost.

[0006] In order to reduce the cost of the mold required to mold one molded product, it is important to consider the life of the molding resin mold. That is, when a lens sheet or the like is molded using a resin mold, it becomes difficult to release the molded product from the molded product as the number of molded products increases, and finally the mold cannot be released and cannot be used. It is important to extend the number of molded articles (resin mold life). If the number of molds per resin mold is small, the mold cost increases. In order to replace the resin mold that has reached the end of its life, the production line must be temporarily stopped, resulting in a decrease in the line operation rate. The life of a resin mold for molding by the method described in JP-A-1-174418 is about 100 to 250 per sheet, and the ratio of the resin mold to the production cost of molded articles is not necessarily low. Further, in this method, a large amount of used intermediate resin molds and molding resin molds are generated, and when these are discarded, a problem of industrial waste occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a resin molding die having high dimensional accuracy is obtained by using a general-purpose thermoplastic resin, and a lens is formed by a simple process using the same. An object of the present invention is to provide a method for manufacturing a molded article such as a sheet.

[0008]

According to the present invention, there is provided a method for manufacturing a molded article, which comprises the steps of: pressing a mold having an uneven pattern on one surface of a thermoplastic resin sheet; Producing a resin mold by transferring to a thermoplastic resin sheet, transferring a concave / convex pattern to a photocurable resin using the resin mold, and manufacturing a molded article by curing the photocurable resin. It is characterized by. The method for producing a molded article according to the present invention is to obtain a resin mold for molding by directly hot-press transfer from a mold to a thermoplastic resin sheet, and the process is simplified since it does not pass through an intermediate resin mold. It is excellent in mass productivity and a molded product with high accuracy can be obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to FIG. 1 by taking as an example a manufacturing process of a Fresnel lens sheet. FIG.
As shown in (a), in the present invention, a thermoplastic resin sheet 1 and a mold 2 in which a concave / convex pattern of a Fresnel lens sheet as a product is reversely engraved are used. First, both or one of the thermoplastic resin sheet 1 and the mold 2 is heated and pressed (FIG. 1B). The thermoplastic resin sheet 1 is released from the mold 2 and a press resin mold (resin mold) 3
(FIG. 1 (c)). The resin molding die 3 may be used as it is for molding a Fresnel lens sheet. However, when it is necessary to provide the thickness and rigidity required for the molding die, the resin molding die 3 has a rigidity as shown in FIG. The thermoplastic resin sheet 1 may be bonded to a certain reinforcing sheet (support) 4. The resin mold 3 is used to mold a Fresnel lens. A space between the resin mold 3 and the transparent substrate 5 is filled with a photocurable resin such as an ultraviolet curable resin 6, and the transparent substrate 5 is irradiated with ultraviolet light to cure the ultraviolet curable resin 6 (FIG. 1).
(E)). Next, the Fresnel lens sheet 7 is obtained by releasing the mold at the boundary between the resin mold 3 and the ultraviolet curing resin 6 as shown in FIG.

As the thermoplastic resin sheet 1 serving as a resin mold, a sheet having a multilayer structure composed of two layers, three layers, or the like can be used as described later. As shown in FIG. 2 (a-1), if a thermoplastic resin sheet having a two-layer structure using a material having a high mold release property is used for the lens molding surface, FIG.
A resin mold having a two-layer structure shown in (d-1) is obtained. When an intermediate adhesive layer is required, a three-layer thermoplastic resin sheet as shown in FIG.
A resin mold shown in (d-2) can also be obtained.

According to the present invention, the thermoplastic resin sheet to which the asperities of the mold are transferred by the hot pressing method is extruded,
Those formed by a method such as cast molding or press molding are used, and the thickness thereof is preferably in the range of 0.2 to 20 mm, more preferably in the range of 0.5 to 5 mm. The above-mentioned thermoplastic resin may be either a crystalline resin or a non-crystalline resin. General-purpose materials as shown in Table 1 below can be used.

If it is necessary to perform hot pressing to transfer the irregularities of the mold to the thermoplastic resin sheet, a predetermined pressure may be applied in a vacuum state. The temperature at the time of hot pressing is too low for molding, or too high for viscosity to drop and the flow starts, especially at the outer periphery of the mold where the resin flows out of the mold and has a uniform thickness Things are no longer available,
It is necessary to make settings so that the pressing force is insufficient to cause insufficient shaping. The temperature suitable for hot pressing varies depending on the type of resin. However, if the material is a crystalline material, the temperature around the melting point is appropriate, and if it is an amorphous material, the glass transition temperature Tg
The high temperature side is suitable. When manufacturing a large-sized resin molding die, it is preferable to select a material having a wide moldable temperature range from the problem of temperature unevenness in the mold, the thermoplastic resin sheet, and the inside of the molding device. In general, a crystalline material is hard at a temperature below the melting point, and softens rapidly when slightly exceeding the melting point, and becomes fluidized. On the other hand, the amorphous material is hard at a temperature lower than Tg, but has a region that gradually softens even when the temperature exceeds Tg, and fluidizes at a temperature considerably higher than Tg. Therefore, it is effective in the present invention to use an amorphous thermoplastic resin having a wide temperature range suitable for molding.

In the present invention, it is preferable that the wetting index of the thermoplastic resin sheet surface of the resin mold to which the concave / convex pattern of the mold is transferred is 40 or less. Here, the wetting index is a value determined by a method specified in JIS K6768 in a flat state. The material forming the thermoplastic resin sheet surface to which the mold concave / convex pattern is transferred has a wetting index of 4
If it is 0 or less, the solubility parameter (SP value) is small, the polarity is low, and the mold releasability from the mold is excellent. If the wetting index exceeds 40, it becomes difficult to release the mold from the mold, and an optical defect called a release mark occurs at the time of release after transfer by hot press. May be impossible. In Table 1 below, measured values of the wetting index of each thermoplastic resin are shown.

In order to suitably use a resin mold obtained from a thermoplastic resin sheet in a 2P molding method using a photocurable resin (for example, an ultraviolet curable resin), the properties desired for the material of the resin mold are: That is, even if the mold is used repeatedly, the shape of the mold is not mechanically deformed. Even if the mold is repeatedly irradiated with ultraviolet rays or the like, there is no deterioration or deformation. A more desirable property of the resin-type material than these properties is that it is easy to release the resin mold from the photocurable resin after the uneven shape is transferred and cured. If a large force is required to release the molded product, the molded product may break at the time of release, or the molded product may be released at a constant speed from one or the outer periphery of the resin molding die. Cannot be peeled off, and a pattern called a release mark appears. In addition, generally, the operations of applying a photocurable resin to a resin mold, curing the photocurable resin by irradiation with ultraviolet light, and releasing the molded article made of the photocurable resin from the resin mold are performed. The force required for mold release increases by repeating, but it is desirable that the number of reusable times (mold life) is long.

As described above, in the present invention, it is preferable that the material forming the thermoplastic resin sheet surface of the resin mold to which the concave and convex pattern of the mold is transferred has a wetting index of 40 or less. 2P using photocurable resin
In order to preferably use the molding method, the difference between the wetting index of the material forming the thermoplastic resin sheet surface to which the concave and convex pattern of the mold is transferred and the wetting index of the cured photocurable resin is 4 or more. Preferably, there is. Table 1 below summarizes the difference in the wetting index between a general ultraviolet curable resin and each thermoplastic resin and the number of moldings (mold life) until the force required for mold release is expected to reach 10 kg. Indicated. Table 1 also shows an example of the wetting index and the limit number of molded articles of the epoxy resin used for the resin mold for molding by the method described in JP-A-1-174418. When a resin mold using a resin having a small difference in the wetting index from an ultraviolet curable resin such as an epoxy resin is used, the number of moldable times is small.

[0016]

[Table 1]

Using a thermoplastic resin or the like shown in Table 1, 300 mm in accordance with the method of the embodiment of the present invention described later.
FIG. 3 shows the result of measuring the relationship between the number of times the Fresnel lens sheet having the square size was molded and the force required when releasing the molded product (Fresnel lens sheet) from the resin mold. The release force was measured using a spring scale. Release force is 1
When the weight exceeds 0 kg, defects such as a release mark begin to occur in a large molded product, and when the molding is repeated, the molded product is not separated from the resin mold at all.

In the present invention, it is not necessary that the thermoplastic resin sheet of the resin molding die to which the concave and convex pattern of the die is transferred is a single-layer sheet made of one material. Considering that the two properties of excellent moldability during hot pressing and excellent mold releasability to the photocurable resin film are compatible, the thermoplastic resin sheet is made of two or more thermoplastic resins. It may be preferable to have a multilayer structure of two or more layers. The thermoplastic resin sheet may have a three-layer structure with an adhesive layer interposed therebetween. Such a thermoplastic resin sheet is formed by laminating a film made of a thermoplastic resin different from the thermoplastic resin on the thermoplastic resin sheet material, or by a multilayer extrusion method using two or more kinds of thermoplastic resins. It can be obtained by molding.

In the case where an expensive thermoplastic resin sheet is used, or when the thickness of the sheet is reduced to shorten the heating-cooling cycle during hot pressing, for example, the thickness of the thermoplastic resin sheet is reduced. With a thickness of about 0.2 to 3 mm, a support made of a rigid sheet material having a thickness of about 10 mm can be bonded to the support to form a resin mold. here,
The rigid support may be formed into a cylindrical roll.

In the production of a lens sheet according to the present invention, the photocurable resin constituting the molded product is usually applied on a sheet-like substrate made of a transparent resin. For example, an acrylic resin, a polystyrene resin, a polycarbonate resin, a polyethylene terephthalate resin, or the like is suitably used. This is because the difference between the wetting index of these resins and the wetting index of the photocurable resin is small, and these resins have high adhesion to the photocurable resin. If the wetting index of the ultraviolet curable resin is about 36 to 40, the above-mentioned general-purpose transparent material having a wetting index of 35 to 40 may be used as the base material.

The present invention is suitable for use in the production of lens sheets such as Fresnel lens sheets, but the molded article produced by the present invention is not limited to lens sheets.

[0022]

The present invention will be described below in more detail with reference to examples. In the following examples, a case where a Fresnel lens sheet is manufactured according to the present invention will be described.

Example 1 Dicyclopentadiene-based amorphous thermoplastic resin (ZEONEX480 manufactured by Zeon Corporation)
A single-layer thermoplastic resin sheet having a thickness of 3 mm was formed by extrusion molding using R). The mold provided with the concave and convex shape of the reverse type of the Fresnel lens is hot-pressed under the condition that the molding temperature is 180 ° C., and the concave and convex shape of the Fresnel lens is transferred to this thermoplastic resin sheet, so that the 50-inch size Fresnel lens A resin mold for molding was obtained. An ultraviolet curable resin is applied onto the resin mold, and a transparent MS substrate having a thickness of 2 mm (methyl methacrylate (MMA) and styrene is applied so that the weight ratio is 6: 4) on the applied surface. (Polymerized resin) was placed, and ultraviolet rays were irradiated from the MS substrate side to cure the ultraviolet curable resin. The wetting index of the ultraviolet curable resin used here after curing is 39, and the wetting index of the dicyclopentadiene-based amorphous thermoplastic resin used as the resin mold is 33 (the difference between the wetting indices is 6). Is.). When the MS substrate is peeled from the resin mold, it is easily released, and the thickness of the MS substrate is 1
A Fresnel lens sheet having a Fresnel lens layer made of a 00 μm ultraviolet curable resin adhered thereto was obtained. The dimensional error between the Fresnel lens sheet and the mold was less than 1%, and the uneven shape was transferred with high accuracy. When Fresnel lens sheets were repeatedly manufactured by this method, molding was possible 390 times or more.

An acrylic plate having a thickness of 7 mm and a slightly larger size than the sheet is adhered to the back surface of the thermoplastic resin sheet using a double-sided adhesive, and a Fresnel lens sheet is formed in the same manner as described above. Was done. By backing the acrylic plate, the rigidity of the resin mold was increased, and not only the workability at the time of production was enhanced, but also the mold release of the molded product was easy.

(Example 2) Polyvinylidene fluoride resin having a wetting index of 34 (KF2300 manufactured by Kureha Chemical Co., Ltd.)
A thermoplastic resin sheet having a multilayer structure in which the surface layer of the polyvinylidene fluoride resin had a thickness of 300 μm and the overall thickness was 3 mm was formed by extruding a multilayer using acrylic resin and acrylic resin. By pressing the mold provided with the reverse concave and convex shape of the Fresnel lens at a molding temperature of 160 ° C., the concave and convex shape of the Fresnel lens is transferred to the polyvinylidene fluoride layer of the thermoplastic resin sheet. An inch-size resin mold for Fresnel lens molding was obtained. The same UV-curable resin (wetting index: 39) as used in Example 1 was applied onto the resin mold, a 2 mm-thick transparent MS substrate was placed on the applied surface, and ultraviolet light was applied from the MS substrate side. Irradiation cured the ultraviolet curable resin. The difference in the wetting index between polyvinylidene fluoride and the ultraviolet curable resin is 5. When the MS substrate is peeled from the resin mold, it is easily released, and the thickness of the MS substrate is 100
A Fresnel lens sheet having a Fresnel lens layer made of a UV-curable resin having a thickness of μm in close contact was obtained. The dimensional error between the Fresnel lens sheet and the mold was less than 1%, and the uneven shape was transferred with high accuracy. When a Fresnel lens sheet was repeatedly manufactured by this method, 33
Molding was possible 0 or more times.

Example 3 A polypropylene resin having a wetting index of 26 was used for the surface layer (thickness: 300 μm), and maleic anhydride-modified polypropylene (trade name: ADMER, manufactured by Mitsui Chemicals, Inc.) was used as an adhesive layer for the intermediate layer. A 3-mm-thick thermoplastic resin sheet having a three-layer structure using an acrylic resin as a main layer was prepared by a multi-layer extrusion method. By pressing the mold provided with the concave-convex shape of the reverse type of the Fresnel lens at a molding temperature of 170 ° C., the concave-convex shape of the Fresnel lens is transferred to the polypropylene layer of the thermoplastic resin sheet, and the 50-inch size is obtained. A resin molding die for molding a Fresnel lens was obtained. On this resin mold, the same ultraviolet curable resin as used in Example 1 (wetting index 3
9) is applied, and a transparent 2 mm thick M
The S substrate was placed, and ultraviolet rays were irradiated from the MS substrate side to cure the ultraviolet curable resin. The difference in the wetting index between the polypropylene and the ultraviolet curable resin is 13. When the MS substrate was peeled off from the resin mold, it was easily released, and a Fresnel lens sheet in which a Fresnel lens layer made of an ultraviolet curable resin having a thickness of 100 μm was adhered to the MS substrate was obtained. The dimensional error between the Fresnel lens sheet and the mold was less than 1%, and the uneven shape was transferred with high accuracy. When Fresnel lens sheets were repeatedly manufactured by this method, molding was possible 500 times or more.

Example 4 At the same time as the extrusion molding of an acrylic resin sheet, a polyvinylidene fluoride film having a wetting index of 36 (DX film, manufactured by Denki Kagaku Kogyo Co., Ltd., thickness 50 μm) was thermally fused (laminated). Thus, a thermoplastic resin sheet having a thickness of 3 mm was prepared. Molding temperature is 16
By hot pressing a mold provided with the reverse concave and convex shape of the Fresnel lens at 5 ° C., the concave and convex shape of the Fresnel lens is transferred to the polyvinylidene fluoride layer of the thermoplastic resin sheet, and the 50-inch size is formed. A resin mold for Fresnel lens molding was obtained. On this resin mold, the same ultraviolet curable resin as used in Example 1 (wetting index: 39)
Was applied, a transparent MS substrate having a thickness of 2 mm was placed on the applied surface, and ultraviolet rays were irradiated from the MS substrate side to cure the ultraviolet curable resin. The difference in the wetting index between polyvinylidene fluoride and the ultraviolet curable resin is 3. When the MS substrate was peeled off from the resin mold, it was easily released, and a Fresnel lens sheet in which a Fresnel lens layer made of an ultraviolet curable resin having a thickness of 100 μm was adhered to the MS substrate was obtained. The dimensional error between the Fresnel lens sheet and the mold was less than 1%, and the uneven shape was transferred with high accuracy. When Fresnel lens sheets were repeatedly manufactured by this method, molding was possible 210 times or more.

[0028]

According to the method of manufacturing a molded article of the present invention, a molded article including a lens sheet such as a Fresnel lens sheet can be manufactured with high dimensional accuracy by a simplified process. In particular, a material having a wetting index of 40 or less forms a thermoplastic resin sheet surface to which a mold uneven pattern is transferred, and furthermore, a material that forms a thermoplastic resin sheet surface to which the mold uneven pattern is transferred. If the difference between the wetting index and the wetting index of the cured photocurable resin is 4 or more,
It is excellent in mold release properties of a molded product, and for example, in the production of a lens sheet, it is possible to respond to a demand for high optical performance.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a process of the present invention.

FIG. 2 is a view showing another example of a thermoplastic resin sheet used in the present invention.

FIG. 3 is a diagram showing a result of measuring a relationship between the number of times of molding a Fresnel lens sheet and a releasing force.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Thermoplastic resin sheet 2 ... Die 3 ... Resin molding die (press resin type) 4 ... Support (reinforcement sheet) 5 ... Transparent substrate 6 ... Photocurable resin (ultraviolet curable resin) 7 ... Molded product (Fresnel lens) Sheet)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 101: 12 B29L 11:00 F term (Reference) 4F202 AA44 AH75 AJ03 AJ09 AJ11 CA27 CB01 CD02 CD23 CD26 4F209 AA44 AH75 PA02 PA15 PB01 PC05 PN09

Claims (8)

[Claims] 1. A resin mold having a concave-convex pattern on one side of a thermoplastic resin sheet is hot-pressed, and the concave-convex pattern of the mold is transferred to a thermoplastic resin sheet to produce a resin mold. A method for producing a molded product, comprising transferring a concave / convex pattern to a photocurable resin using the method and curing the photocurable resin to produce a molded product. 2. The method according to claim 1, wherein the surface of the thermoplastic resin sheet to which the concave and convex pattern of the mold is transferred is formed of a material having a wetting index of 40 or less. 3. The difference between the wetting index of the material forming the thermoplastic resin sheet surface to which the concave and convex pattern of the mold is transferred and the wetting index of the cured photocurable resin is 4 or more.
Or the method for producing a molded article according to 2. 4. The thermoplastic resin sheet to which a concave / convex pattern of a mold is transferred has a multilayer structure of two or more layers composed of two or more thermoplastic resins.
A method for producing a molded article according to the above item. 5. A thermoplastic resin sheet to which a concave and convex pattern of a mold is transferred, wherein the thermoplastic resin sheet material is formed by laminating a film made of a thermoplastic resin of a type different from the thermoplastic resin. A method for producing a molded article according to claim 4. 6. The production of a molded article according to claim 4, wherein the thermoplastic resin sheet to which the concave / convex pattern of the mold is transferred is molded by a multilayer extrusion method using two or more kinds of thermoplastic resins. Method. 7. The resin molding die according to claim 1, wherein a surface different from the surface on which the concave / convex pattern of the mold is transferred is lined with a rigid support.
A method for producing a molded article according to the item. 8. The method according to claim 7, wherein the rigid support is a cylindrical roll.