JP2005059334A - Manufacturing method of optical molded product by direct pressure type injection molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase a production speed and to enhance quality while reducing a production cost using direct pressure type injection molding in place of injection molding in a known method for forming a precise dot pattern. <P>SOLUTION: An injection molding machine is constituted of an upper mold 3, a lower mold 4 and a material supply device 5. The upper mold 3 and the lower mold 4 are installed at vertically opposed upper and lower positions and the material supply device 5 is moved laterally to supply a material at a high speed. Next, the upper mold 3 is moved downward and the core 31 of the upper mold 3 is fitted in the cavity 41 of the lower mold 4 under pressure to perform pressurizing operation. Finally, the upper mold 3 is raised and the solidified optical molded product is taken out of the cavity 41 of the lower mold 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

    The present invention relates to a method for manufacturing an optical molded product by direct pressure injection molding, and more particularly to a manufacturing method capable of improving production efficiency and improving product quality.

  With the rapid growth of electronic science and technology, many electronic products are appearing in the world. Among them, in particular, mobile phones and computers bring convenience in people's lives and work, and all of the above electronic products use liquid crystal displays, and display various information on the screen.

  In addition to the liquid crystal display substrate, the liquid crystal display is composed of optical molded products such as a light guide plate, a diffuser plate, and a light collecting sheet. The main mechanism is to apply a light source to the light guide plate and use it as a reflective dot on the light guide plate reflection surface. After reflection, the light exits from the light exit surface, and after the unevenness is eliminated by the diffusion plate, the brightness is enhanced by the light collecting sheet, and the sufficiently uniform light is projected onto the liquid crystal substrate, and the screen is projected onto the liquid crystal display substrate. To project. That is, optical molded products such as a light guide plate, a diffusion plate, and a light collecting sheet are extremely important components in a liquid crystal display.

  Taking a light guide plate manufacturing method as an example, there are many products in which a resin is molded by an injection molding method. As shown in FIG. 1, a known manufacturing method moves an upright male mold 1 in a lateral direction and a female mold 2. The core 11 and the cavity 21 of the female mold 2 corresponding to the central part of the female mold 2 are pressed and held in a sealed state, molten resin is injected from the gate of the female mold 2, filled in the cavity 21 of the female mold 2, and the resin is cooled. Thereafter, the male mold 1 is moved to the original position, and the cured resin is taken out from the cavity 21 to be manufactured.

  However, since the light guide plate is plate-shaped and its thickness is directly proportional to the area, if the cavity 21 is relatively large in a situation where high-temperature resin flows into the cavity 21 after injecting resin from the gate 22, filling of the resin is performed. The speed is naturally reduced, and the time for filling the cavity with the resin also becomes longer.

  Since the mold is made of metal and the temperature at the time of resin filling is lower than that of the resin and the thermal conductivity is high, the molten resin at high temperature is injected into the cavity 21 from the gate 22 and then touched to the mold. The temperature of the remaining portion is cooled, and a phenomenon in which the previously injected resin is solidified easily when the resin is not filled in the cavity 21 easily occurs.

  It is necessary to heat the male mold 1 and the female mold 2 to a high temperature state in order to prevent the resin from being cooled and solidifying too quickly during the injection of the resin, and to produce defective products. It can reach every corner of the cavity 21.

  However, after the resin injection is completed, the temperature of the male mold 1 and the female mold 2 must be lowered, and the resin cannot be removed from the mold until after the resin is solidified. Then, it is necessary to heat the male mold 1 and the female mold 2 again, and it takes time to heat and cool the mold, so that the production efficiency is lowered and the manufacturing cost is accordingly increased.

  It is necessary to always install reflective dots on the reflective surface of the light guide plate. There are several methods for forming the reflective dots, but there are three types that are relatively commonly used. A method of printing special ink on the reflective surface. There are a method of etching the reflective surface and a method of simultaneous molding at the time of injection molding, and among the above-mentioned three methods, the method of simultaneous molding at the time of injection molding is the most convenient and the cost is low.

  However, since the design of the reflective dots is extremely fine, this simultaneous molding method is not so difficult in the case of a light guide plate with a relatively small area for a cellular phone or the like, but it is not very difficult. In the case of a light guide plate having a relatively large area, such as a large area during injection molding, the thickness becomes 1 cm or more, and the time from injection of resin to cooling becomes too long. Therefore, the manufacturer does not heat the male mold 1 and the female mold 2 at a high temperature, and the mold temperature only needs to be a temperature at which the molten resin in a high temperature can be cooled immediately after the injection is completed. Thereby, the cooling time is shortened.

  However, since the resin has already begun to solidify gradually when the molten resin is injected, the extremely fine reflection dot design cannot be completely projected onto the light guide plate. Therefore, as shown in FIG. If the mold 1 is moved slightly in the lateral direction and pressed against the resin that has already solidified, correct reflective dots cannot be formed.

  It is not easy to balance the time for applying high pressure, the magnitude of the pressure, the time for injecting the resin, the time for the resin to solidify, etc. Therefore, it will easily produce defective products that lack the precision of the design. .

  In order to apply high pressure, the mold clamping force of the molding machine increases, which requires a relatively large space, increases power consumption, and increases costs.

  Since the light guide plate is molded at a high temperature and high pressure, stress is easily generated at the time of molding, thereby increasing the incidence of defective products.

  Similarly, in the diffusion plate and the light collecting sheet, it is necessary to provide a large number of continuous unevenness having the effect of diffusing and condensing light on the surface, and the unevenness includes arc-shaped unevenness and sawtooth unevenness. There is a shape.

  However, in any type of shape, the required precision is very high as with the reflective dots, and it is impossible to obtain a good effect by molding by a known method. Therefore, the known manufacturing method is appropriate. It is not a manufacturing method.

  The problem to be solved is that the production efficiency is high and the precision is high while the production efficiency is poor, the quality is unstable and the production cost cannot be reduced by the molding by the known method. Can be molded.

  The present invention is a method of manufacturing an optical molded product by direct pressure injection molding, and has a structure in which the mold is moved up and down, and after the upper mold is lifted, the material supply device sets the material to the lower mold at a set speed. The main feature is that the upper mold is pressed with the lower mold after the material supply device is moved backward and the light guide plate is formed.

  In the method of manufacturing an optical molded product by direct pressure injection molding according to the present invention, a fixed amount of material is supplied to the cavity at a high speed by the material supply device 5, so that the material can be supplied in the shortest time. It is possible to prevent the material from solidifying only by keeping 4 slightly heated. Therefore, after pressing the upper and lower molds 3 and 4, it is necessary to cool the mold over a long time. Therefore, the molding time can be shortened and the cost can be reduced.

  Since the material supply speed is high, after the material supply is completed, the resin in the cavity 41 has not started to solidify. Therefore, after the upper and lower molds are pressed together, further pressure is applied as in a known method for reflection. There is no need to form dots, and the time can be reduced accordingly. That is, since the resin has not yet solidified, the reflection dots, the fineness for light diffusion and light collection, can be sufficiently applied by the pressure when the core 31 of the upper mold 3 is pressed into the cavity 41 of the lower mold 4. Unevenness can be formed, the incidence of defective optical molded products such as reflective dots, diffuser plates, and light condensing sheets can be greatly reduced, and an increase in cost can be prevented.

  Further, since it is not necessary to apply pressure, it is not necessary to increase the clamping force of the molding machine, and accordingly, the use space is reduced, the power consumption is reduced, and the manufacturing cost can be reduced.

  After supplying a certain amount of material, the upper mold 3 moves downward and the lower mold 4 also moves upward, so that the time required for pressing the upper and lower molds 3 and 4 can be shortened. , 4 move and press fit, the pressure on the resin is increased correspondingly, and the incidence of defective products can be reduced in the molding of optical molded products.

  As shown in FIG. 4, since the material supply device 5 can supply materials continuously to a plurality of molds simultaneously, not only can the equipment cost be reduced, but also the resin can be cooled. There is no need to wait, and production efficiency can be increased accordingly.

  As shown in FIG. 3, the present invention is a method for manufacturing an optical molded product, and mainly includes an upper mold 3, a lower mold 4, and a material supply device 5.

  The upper mold 3 and the lower mold 4 are installed at positions facing vertically upright, and the material supply device 5 supplies the material at a high speed by moving sideways.

  A core 31 is provided on the bottom side of the upper mold 3, and the core 31 has a size corresponding to the cavity 41 provided on the upper end surface of the lower mold 4. The pattern of the reflective dots to be molded or the irregularities for diffusing and collecting the light are processed.

Next, a manufacturing method is shown.
The material supply device 5 moves in the lateral direction, and the material supply port 51 comes to the position of the front end of the cavity 41.

  Subsequently, the material is retreated at the set speed, and at the same time, the material is supplied into the cavity 41 at high speed in a short time. The quantitative supply amount of the material is set according to the size of the optical molded product. When the molten resin is filled into the cavity 41 at a high speed, the material supply device 5 has returned to the original position.

  Next, the upper mold 3 is moved downward, the core 31 of the upper mold 3 is pressed into the cavity 41 of the lower mold 4, and a pressure compression operation is performed.

  Finally, the upper mold rises, and the solidified optical molded product is taken out from the cavity 41 of the lower mold 4 to be completed.

It is the figure which showed shaping | molding of the light-guide plate in a well-known structure. It is the figure which showed the mode of the pressurization of the light-guide plate in a well-known structure. It is the figure which showed the manufacturing method of this invention. It is the figure which showed another Example of this invention.

Explanation of symbols

1 Male 11 Core 2 Female 21 Cavity 22 Gate 3 Upper Mold 31 Core 4 Female 41 Cavity 5 Material Supply Device 51 Material Supply Port

Claims (3)

Mainly composed of upper mold, lower mold and material supply device,
The upper mold and the lower mold are installed at positions facing vertically up and down, and the material supply device moves in the horizontal direction to supply the material to the molds facing each other at high speed, and then the upper mold and the lower mold. An optical molded article manufacturing method by direct pressure injection molding, wherein an optical molded article is molded by pressing a material with a mold.   A method of manufacturing an optical molded article by direct pressure injection molding, wherein the upper and lower molds can move together to pressurize the material after the material supply device supplies the material.   A method of manufacturing an optical molded product by direct pressure injection molding, wherein the material supply device can continuously supply material to a plurality of molds.

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