JPH1076553A - Gate cut method of light guide plate molding die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the deterioration of brightness or light permeability of a cut part due to becoming clouded and the like by a method wherein a gate part between a sprue runner and a molded form is cut immediately after injection by a gate cut pin, provided between an ejector pin for extruding the sprue runner and a product ejection pin and equipped with a spring for buffering shock. SOLUTION: Molten resin is filled into a cavity 14 from an injection device. A gate cut pin 12 is pushed forward to separate a sprue runner 9 from a product 10 while resin is still soft immediately after injection. In this case, a spring 13 for buffering shock is acted so that buckling is not generated in the gate cut pin 12 even when an excessive or repeated load is applied on the same. A mold is opened after the filled resin in the cavity 14 is cooled and cured to eject the sprue runner 9 by an ejector pin 7 for pushing out the sprue runner and eject the product 10 by a project ejector pin 8 respectively. According to this method, the cut part will not become clouded and remaining stress or warpage will hardly be generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cutting a gate of a light guide plate using an injection molding machine.

[0002]

2. Description of the Related Art A light guide plate is a liquid crystal display (LCD).
Acrylic plate incorporated in the backlight unit that guides light to the liquid crystal inside, and is a member that guides light to the liquid crystal from the edge of the plate or directly below it. (1) Foreign matter that causes brightness and black spots Or, there is no yellowing that causes a decrease in light transmittance. (2) There is no sink or warp which causes uneven brightness. (3) No residual stress. (4) The weight and dimensions are stable. Etc. are required.

[0003]

Many of the general molded products other than the light guide plate cut the sprue runner and the molded product after removing the molded product from the mold, but as described above, the light guide plate transmits light. The gate cut of the cooled and hardened molded product causes clouding at the cut portion, and lowers the brightness and light transmittance.

An object of the present invention is to provide a method for cutting a gate of a mold for molding a light guide plate, which eliminates the drawbacks such that the cut portion becomes cloudy due to the above-described gate cut and lowers the luminance and light transmittance. To provide.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a light guide plate molding metal which is an acrylic plate incorporated in a backlight unit for guiding light to a liquid crystal in a liquid crystal display (LCD). In the gate cutting method of the mold, a gate cut pin with a shock absorbing spring is provided between the ejector pin for sprue runner extrusion and the product protruding pin that projects the molded product from the mold, and the resin is injected into the mold cavity Immediately after the completion of the injection, a gate portion between the sprue runner and the molded product is cut by the gate cut pin.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION A gate cut pin provided with a shock absorbing spring is provided between an ejector pin for pushing out a sprue runner of a mold for molding and molding a light guide plate and a product projecting pin for projecting a molded article from the mold. Immediately after the injection of injecting the resin into the mold cavity is completed, the gate cut pin is used to cut the gate between the sprue runner and the molded product.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. 1 to 3. Reference numeral 1 denotes a movable mold for forming a light guide plate, and a cavity 14 is formed when the movable mold comes into contact with a fixed mold (not shown). After that, the molten resin is injected into the cavity 14 from an injection device (not shown). The movable mold 1
Is composed of a movable mold 2, a mounting plate 3, a pin 5 for maintaining a space 4 with the members 2 and 3 being separated, and a protruding plate 6 mounted in the space 4.

The projecting plate 6 is provided with a sprue runner ejector pin 7, a product projecting pin 8, and a gate cut pin 12 for separating the sprue runner 9 from the product 10 by a gate 11. The gate cut pin 12 has a shock absorbing spring 13 for preventing buckling during gate cut.
Is provided.

The operation is described below. To explain the operation, the movable mold 1 comes into contact with a fixed mold (not shown), the cavity 14 is formed, and the mold of the mold clamping device is formed. When the tightening pressure reaches a predetermined value, the injection device fills the cavity 14 with molten resin. At this time, the sprue runner 9 and the product (light guide plate) 10 are in communication with each other through a gate 11 as shown in detail in section A.

Then, immediately after the injection is completed, while the resin is not yet cured, the pressure cut oil acts on a hydraulic pipe (not shown) from the rear end (left side in the figure) of the gate cut pin 12 while the resin is not yet cured. To the front (right side in the figure) about 2m
Pressing about m, the sprue runner 9 and the product 10 are separated at the gate 11 as shown in FIG. At this time, an excessive load is applied to the gate cut pin 12 or a repeated load is applied to the gate cut pin 12.
The impact buffer spring 13 works so that buckling does not occur.

When the filling resin in the cavity 14 is cooled and hardened, the mold is opened this time, and as shown in FIG. 3, the sprue runner 9 is ejected by a sprue runner ejector pin 7 and the product 10 is ejected by a product projection pin 8. Protruded.

[0012]

As described above, since the gate cut is performed immediately after the completion of the injection and in a soft state in which the resin has not yet been cured, not only the cut portion does not become cloudy, but also residual stress and warpage can be generated. It becomes harder and the flaws originally fried are removed. In addition, by performing the gate cut during the molding, the gate cutting step after the molding can be omitted, and the molding cycle can be shortened and the production cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is an explanatory view of a gate cut in detail A of FIG.

FIG. 3 is a view showing one embodiment of the present invention, and is an explanatory view of a product and a sprue runner protrusion.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 movable mold for forming light guide plate 2 movable mold 3 mounting plate 4 space 5 pin 6 projecting plate 7 ejector pin for pushing out sprue runner 8 product projecting pin 9 sprue runner 10 product 11 gate 12 gate cut pin 13 spring 14 cavity

Claims (1)

[Claims] 1. A gate cutting method for a mold for molding a light guide plate, which is an acrylic plate, incorporated in a backlight unit for guiding light to a liquid crystal in a liquid crystal display (LCD). A gate cut pin provided with a shock-absorbing spring is provided between product protruding pins for projecting the product from inside the mold. Immediately after injection is completed to inject resin into the mold cavity, a sprue runner is formed by the gate cut pin. A gate cutting method for a light guide plate molding die, comprising cutting a gate portion between products.