KR20060048245A - Forming method of thick leading light plate and forming die - Google Patents

Abstract

Provided is a molding method capable of forming a high quality thick light guide plate in a short molding cycle.

A grant space constituted by a stamper 8 provided in the cavity side nest 4 of the stationary side mold, the core side nest 23 of the movable side mold, and the peripheral side wall side nests 30 and 30 ( K) is filled with a predetermined amount of molten resin. Then, the valve gate is closed and compressed by the core side nest 23. The compression improves the transferability and shortens the molding cycle. When compressing, the temperature of the circumferential side wall side nests 30 and 30 is made higher than the temperature of the cavity side nest 4 and the core side nest 23. Thereby, the cooling rate of the peripheral side wall side nests 30 and 30 becomes slow, a compression effect is raised, and generation | occurrence | production of a plate sag is suppressed.

Injection process, compression process, nest

Description

Forming method and forming mold of thick light guide plate {FORMING METHOD OF THICK LEADING LIGHT PLATE AND FORMING DIE}

1: is sectional drawing which shows typically the metal mold | die for shaping | molding of the light guide plate which concerns on embodiment of this invention in the open state.

2 is a view showing a state of molding using a mold according to an embodiment of the present invention, (a) is a cross-sectional view showing a state in which a predetermined amount of molten resin is filled by closing the mold; It is sectional drawing which displays the molten resin filled with predetermined amount in the compressed state.

3 is a cross-sectional view showing a mold in an open state to take out a thick light guide plate.

※ Explanation of code ※

1. Fixed side mold 4. Cavity side nest

8. Stamper 10. Valve gate

13. Valve rod 18. Hot runner

20. Movable Side Mold 23. Core Side Nest

30. Perimeter sidewall nest

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method and a mold for molding a light guide plate made of a synthetic resin used for a backlight of a liquid crystal display, but is not limited thereto, and is suitable for molding and molding die suitable for molding a large light guide plate having a thickness of 6 mm or more. It is about.

Liquid crystal display devices, such as a computer and a liquid crystal television, consist of a liquid crystal display and a light guide plate. And a light source is arrange | positioned at the side part of the light guide plate. Therefore, the light emitted from this light source is reflected by the light reflection layer formed on one surface of the light guide plate and exits from the light exit surface. The front of the liquid crystal display is illuminated by this light.

Such a light guide plate is manufactured by cutting an acryl plate into predetermined size, and printing a pattern, such as a dot and a groove shape, on the surface. However, in the field of monitor applications, there is a transition phenomenon from the CRT to the liquid crystal display by the cathode ray tube, the supply of acrylic plates, especially thick acrylic plates, is insufficient, and supply of light guide plates by injection molding is required.

The injection molding method conventionally consists of a heating cylinder and the screw which drive is freely provided in the rotation direction and the axial direction in this heating cylinder. Therefore, when the resin material is supplied to the heating cylinder and the screw is rotated, the resin material is melted by heat applied from the outer peripheral portion of the heating cylinder and heat generated by the rotational friction force or shear force of the screw in the process of being sent forward by the screw. And accumulate in the metering chamber in front of the heating cylinder. Thus, a molded article is obtained when the mold is injected into the imparting space of the clamped mold, and the mold is opened while waiting for cooling solidification. By the way, the light reflecting surface of the light guide plate is required to have high high reflectivity, and a high quality molded article having no welding point or the like is required. When the transferability to the light guide plate of the pattern used as a light reflection surface is made high, the flow temperature of a molten resin will improve and transferability will improve. However, it takes longer for cooling and solidification time to take out of the mold, and the molding cycle becomes longer. Therefore, Patent Documents 1 to 4 propose a sheet cycle method of forcibly heating a molten resin when injection filling and forcibly cooling the filling when the filling is completed and the pressure is preserved.

[Patent Document 1] Japanese Patent Application Publication No. 45-22020

[Patent Document 2] Japanese Patent Application Laid-Open No. 51-22759

[Patent Document 3] Japanese Patent Application Laid-Open No. 55-109639

[Patent Document 4] Japanese Patent Application Laid-Open No. 57-16522

[Patent Document 5] Japanese Patent Laid-Open No. 2001-18229

[Patent Document 6] Japanese Patent Laid-Open No. 2002-210795

[Patent Document 7] Japanese Patent Application Laid-Open No. 9-155875

[Patent Document 8] Japanese Patent Laid-Open No. 2002-46159

Patent document 5 proposes a molding method that further improves the above heat cycle method. That is, a mold is proposed in which a heat insulation layer is provided between the mold and the inlet, and a heating medium and a cooling medium are introduced in the vicinity of the cavity surface of the nest. Patent Literature 6 also proposes a mold in which the resin supply passage is a semi-hot runner method, a heating / cooling medium flow path is provided in a part of the resin passage, and the surface of the cavity is alternately heated and cooled.

Patent Documents 7 and 8 propose a method for forming a light guide plate by an injection molding method. That is, Patent Literature 7 shows a mold for injection molding in which a heat insulation layer is provided between a surface constituting the mold surface of the mold and a metal plate having a pattern surface of a rough surface.

In addition, Patent Document 8 discloses a molding method in which a molten resin has a viscosity in a range of 50 to 5,000 Pa · sec, through which a gate is passed and injection-filled into a cavity of a mold at an injection rate in the range of 1 to 15 cm 3 / sec. Is indicated.

According to the molding method proposed by Patent Documents 1 to 4, since the surface of the cavity is heated and filled at a high temperature, a molded article having excellent transferability is obtained, and is forcibly cooled, so that the molding cycle is shortened. It is admitted. Moreover, according to the method of patent document 5, the switching of heating and cooling of the cavity surface of a metal mold | die can be carried out in a short time, and the fluidity | liquidity of molten resin increases by heating a metal mold | die, and the characteristic that thin molding is recognized is recognized. In addition, according to the invention described in Patent Document 6, since the heat cycle method is applied and a heat insulation layer is provided in a part of the resin supply path, occurrence of minute sagging, hesitation, etc. appearing on the surface of the molded article is suppressed. The effect is recognized. According to the invention described in Patent Literature 7, a heat insulating layer is provided between the mold and the metal plate having the pattern surface, so that when the plasticized hot molten resin is injected, the mold is temporarily heated and the mold surface is sufficiently transferred. Moreover, according to invention of patent document 8, since it injects at low speed, generation | occurrence | production of a sag is suppressed and a thick large area product is obtained.

However, in the conventional molding method as described above, there is a drawback that it takes too long to form a thick light guide plate such as 6 mm or more. In particular, according to the invention of Patent Literature 8, when the viscosity of the molten resin is in the range of 50 to 5,000 Pa · sec, the gate is passed through and injected in the range of 1 to 15 cm 3 / sec. have. In addition, when attempting to mold a thick light guide plate having a thickness of 6 mm or more by the heat cycle molding method as described above, the holding step is lengthened, for example, 90 seconds, and there is a problem in carrying out.

On the other hand, injection and compression molding methods are also known in which a predetermined amount of molten resin is filled into a mold providing space of a mold, a movable mold is driven in the clamping direction, and the molten resin filled is compressed. Therefore, in combination with this injection / compression molding method and the above-described heat cycle molding method, if the gate, which is a passage of the molten resin, is closed and compressed after a predetermined amount of filling, the packing process time becomes substantially zero. The molding cycle can be shortened because the screw can be immediately driven to enter the weighing process to melt the resin material. However, the surface of the thick light guide plate may be concave, that is, sag or sink marks, and the quality of the light guide plate may be remarkably impaired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a method for forming a thick light guide plate and a mold for forming a high thickness light guide plate in a short molding cycle.

In order to achieve the object of the present invention, the present invention employs the following means.

(1) Reduction of holding time: When molding by injection molding, in order to prevent sagging on the surface of the molded product due to reduction in volume due to cooling solidification, a holding pressure step is applied to apply a constant resin pressure from the gate. The process requires a long time, such as 90 seconds, when forming a thick molded article in a general-purpose general purpose mold.

However, after injection of a predetermined amount of molten resin into the mold providing space of the mold, the gate, which is the passage of the molten resin, is closed, and the movable mold is driven in the clamping direction to compress the pressure, and the pressure retention time becomes substantially zero. It can be driven into the weighing process to melt the resin material by rotating. Thus, in the present invention, injection and compression molding methods are applied. The valve gate is applied to the gate and the hot runner is applied to the runner.

According to the present invention, the imparting space for forming a thick light guide plate includes a cavity for forming both sides of the thick light guide plate and a circumferential side wall for forming a core and a peripheral cross section, but the molten resin filled with a predetermined amount by driving the mold in the clamping direction. Is compressed so that the temperature of the circumferential sidewall is higher than the temperature of the cavity and core. The cooling rate of the imparting space formed in the mold is larger in the peripheral side wall than in the cavity or core side. Since the cooling rate is large, it cannot be replenished only by the compression operation of the heat shrinkage according to the progress of cooling, and the surface of the thick light guide plate is sag, but the temperature of the peripheral side wall is increased and the cooling is delayed, thereby obtaining sufficient compression effect and sag. The occurrence of is suppressed. For example, when forming a thick light guide plate with an acrylic resin, the temperature of the peripheral side wall is maintained at 120 to 130 ° C. in order to smooth the cooling rate of the peripheral side wall and increase the compression effect.

(2) Shortening of the charging time: Generally, when the charging time is short, appearance defects such as weld and silver are generated around the gate, so that the charging time is long enough. The diameter, the opening and closing stroke, and the thickness of the gate are made larger in a possible range depending on the thickness of the thick light guide plate. As a result, the filling time is shortened without causing any appearance defects, and further, the molding cycle is shortened.

(3) Lowering the resin temperature and the mold temperature: By lowering the resin temperature and the mold temperature, the cooling and solidification time is shortened, thereby shortening the molding cycle, but when the temperature of the resin and the mold is low, The molten resin starts to solidify before the compression pressure is applied to the wall contacting the wall constituting the imparting space, and is inferior in transferability to a thick light guide plate. Therefore, in the present invention, a so-called heat cycle molding method is applied in which the mold is rapidly heated to improve the transferability during injection and compression, and is rapidly cooled after filling. Specifically, in the case where the resin is a methacryl resin, the resin temperature is 230 ° C., the mold temperature is 75 ° C. or higher, and after injection injection, the temperature is rapidly cooled to 40 ° C., and the molded article surface temperature of the thick light guide plate is For example, it falls to 65 degreeC and is taken out.

(4) Adoption of heat insulation layer: In this way, when the mold temperature is lowered, the temperature of the molten resin charged in the imparting space is lowered and transferability is lowered. In the present invention, the heat insulating layer is provided on the wall surface of the imparting space. By providing the heat insulation layer, the wall surface constituting the imparting space is temporarily heated by the molten resin to be injected, the compression pressure is sufficiently applied, and the transferability is improved. Such a heat insulating layer is formed of an amorphous heat-resistant polymer such as polysulfone, polyethersulfone, polyimide, epoxy resin and the like. For example, in order to make polyimide adhere to a metal mold | die, the precursor solution of linear polymeric polyimide is apply | coated to a metal mold | die, and it heats. Then, the polyimide layer which is a heat insulation layer is formed in the surface of a metal mold | die.

(5) Employment of nests (boxes which can be nested in order of size): The above-mentioned cavity, core and peripheral side wall are heated and cooled, so that the mold is provided with heating means or cooling means. Therefore, a nest is preferably provided. That is, a cavity side nest, a core side nest, and a peripheral side wall side nest are provided. And these nests are provided with a heat pipe and a coolant pipe that are individually temperature-controlled independently. In addition, since these nests are rapidly heated and quenched, they are preferably formed by an alloy having high thermal conductivity, for example, beryllium-copper alloy. By using such a high thermal conductivity alloy, the temperature rise time and fall time of the nest are shortened to about 1/2 compared with that of the stainless steel nest.

(6) Use of a stamper: According to the present invention, in order to form a light reflection layer on the surface of a thick light guide plate, a pattern such as a dot shape or a groove shape is formed on the cavity side frame plate or the core side frame plate, but the cavity When the side nests and the core side nests are applied, they are formed in their nests. Alternatively, a stamper in which a dot or groove pattern is formed is used. Such a stamper is produced as disclosed in patent document 7, for example. At this time, the heat insulation layer as mentioned above can also be provided in the back surface of a stamper.

In this way, the molding method of the thick light guide plate according to the present invention comprises a cavity side frame plate of a stationary side mold and a core side frame plate of a movable side mold, and the cavity side frame plate and a core side frame plate to achieve the above object. An injection step of filling a predetermined amount of molten resin through a hot runner and a valve gate in a grant space that is a circumferential side wall blocking the circumferential side of the open space, and the valve side is attached to the movable side mold by attaching the valve gate after the injection step. A pattern for driving in the clamping direction with respect to the mold to compress the filled molten resin, and cooling after the compression process to open the movable side mold to form a light reflecting layer by the cavity side frame plate or the core side frame plate A molding method which is a drawing step of taking out the transferred light guide plate, wherein at the time of the injection step, the cavity-side mold While adjusting the temperature of the plate, the core side frame plate and the circumferential side wall, the compression step is configured so that the temperature of the circumferential side wall is higher than the temperature of the cavity side frame plate and the core side frame plate. do.

Further, the method for forming a thick light guide plate according to the present invention includes a circumferential side wall which blocks a circumferential side portion of an open space including a cavity side nest of a stationary side mold, a core side nest of a movable side mold, and the cavity side nest and a core side nest. An injection step of filling a predetermined amount of molten resin through a hot runner and a valve gate in the imparting space to be the side nest; and closing the valve gate after the injection step to drive the movable mold in the clamping direction with respect to the fixed mold. A compression step of compressing the filled molten resin and a drawing step of cooling after the compression step to open the movable side mold to take out the light guide plate on which the pattern of the light reflection layer is transferred by the cavity side nest or the core side nest. A molding method, wherein the cavity side nest and the core side during the injection process While controlling the temperature of the nest and the circumferential side wall side nest, the compression step is configured to be performed in a state where the temperature of the circumferential side wall side nest is higher than the temperature of the cavity side nest and the core side nest.

Moreover, according to this invention, it forms by providing the stamper which forms the pattern which becomes a light reflection layer in the said cavity side nest or the said core side nest.

Moreover, according to this invention, the stamper for transferring the pattern which becomes a light reflection layer to the said cavity side nest, and the heat insulation layer are provided in the surface of the said core side nest, and the said core side nest is always cooled by cooling water, Mold.

Moreover, according to this invention, the stamper for transferring the pattern which becomes a light reflection layer on the surface of the said cavity side nest, and the heat insulation layer are provided in the back of the said stamper and the surface of the said core side nest, and the said cavity side nest And the core side nest are molded while being always cooled by cooling water.

In addition, according to the present invention, heating and cooling of the cavity-side frame plate, the core-side frame plate, and the circumferential side wall are performed in a set of heating and cooling devices, and the heating medium, the refrigerant body, and the switching timing are performed in a molding cycle. Adjust to individual.

In addition, according to the present invention, heating and cooling of the cavity side nest, the core side nest, and the circumferential side wall side nest are performed by a set of heating and cooling devices, and the switching timing of the heat medium and the refrigerant body is performed in a molding cycle. Adjust to individual.

Further, according to the present invention, the thick light guide plate obtained by the molding method is placed on the cooled lower cooling jig, and similarly pressed by the cooled upper cooling jig to cool the thick light guide plate and sandwiched by both jigs, The deflection is corrected by applying a load in the pushing direction.

The mold for forming a thick light guide plate according to the present invention is a fixed side mold and a movable side mold which can be compressed in the clamping direction after a predetermined amount of molten resin is filled, and in the imparting space formed of these molds during clamping, The hot runner communicates through the valve gate through which the resin passage is opened and closed, and when the molten resin is injected and charged from the hot runner into the given space, the light reflecting surface is transferred to the thick light guide plate by the fixed side mold or the movable side mold. As the mold, the fixed side mold and the movable side mold are heated and cooled, and the temperature of the circumferential side wall constituting the circumferential side of the provision space is independent of the fixed side mold and the movable side mold. It's supposed to be adjustable.

Moreover, the metal mold | die for shaping | molding of the thick light-guide plate which concerns on this invention becomes a movable side metal mold | die which can be compressed to a clamping direction after the fixed side metal mold | die and a predetermined amount of molten resin are filled, and a cavity side nest | substrate is provided in the said fixed metal mold | die, A core side nest is installed in the movable side mold, and a circumferential side wall side nest is installed in the circumferential side portion of the cavity side nest or the gore side nest, and when the movable side mold is clamped with respect to the fixed side mold, The imparting space is constituted by the core side nest and the circumferential side wall side nest, and a hot runner communicates with the imparting space through a valve gate through which the resin passage is opened and closed, and molten resin is injected into the imparting space from the hot runner. When charged, light is reflected on a thick light guide plate by the cavity side nest or the core side nest. As the mold to be transferred, the cavity side nest and the core side nest are heated and cooled, and the temperature of the circumferential side wall side nest is adjusted independently of the cavity side nest and the core side nest. It is supposed to be.

Moreover, according to this invention, the said stamper for transferring the pattern which becomes a light reflection layer is provided in the cavity side nest on the surface of a thick light-guide plate.

Moreover, according to this invention, a heat insulation layer is provided in the surface of the said core side nest.

Moreover, according to this invention, a heat insulation layer is provided between the surface of the said core side nest, the back surface of the said stamper, and the said cavity side nest.

According to the present invention, the cavity side nest, the core side nest, and the circumferential side wall side nest are made of beryllium-copper alloy.

First, the metal mold | die which concerns on embodiment of this invention is demonstrated by FIG.

As shown in FIG. 1, in the mold according to the preferred embodiment of the present invention, the cavity-side nest 4 is fixed to the stationary side mold 1, and the core-side nest 23 is movable to the movable side mold 20. Peripheral side wall side nests 30 and 30 are provided on the outer circumferential portion of the core side nest 23, respectively. And the movable side metal mold | die 20 is comprised with the mold which can be compressed.

The stationary side die 1 is attached to the frame mounting plate 15. A first recess 2 having a predetermined size is formed on the parting line P side of the stationary mold 1, and a relatively shallow second recess is formed around the first recess 2. The recessed part 3 is formed. A cavity-side nest 4 is attached to the first concave portion 2 by the storage bracket 5, and the second concave portion 3 is inclined toward the taper as it moves away from the parting line P. The guide member 7 which has (6) is provided. The guide member 7 guides the circumferential side wall side nests 30 and 30 described later. The cavity-side nest 4 is made of, for example, beryllium-copper alloy having high thermal conductivity, and although not shown in FIG. 1, the heating / cooling of a heating medium of about 150 ° C. and a cooling medium of about 20 ° C. alternately flows. Dragon pipe is installed. In addition, a stamper 8 in which a pattern such as a dot shape, a groove shape, or the like is formed on the surface of the cavity-side nest 4 is mounted by the storage tool 9. Or it adsorb | sucks by several vacuum suction openings from the cavity side nest 4 back side.

The front end of the valve gate 10 is opened at the side of the cavity side nest 4 configured in this manner. FIG. 1 is a cross-sectional view schematically showing an embodiment of the present invention, which is not exactly shown, but is a diameter of the tip portion of the valve gate 10, an opening / closing stroke, and a gate which is an inlet of the resin into the imparting space. The thickness is chosen as large as possible. For example, a light guide plate having an 18-inch size and a thickness of 12 mm and a product weight of 1500 gr, the valve gate diameter is 5 mm and the needle stroke is 30 to 1.5 times larger than a conventional valve gate, such as 30 mm. The thickness of the gate is 12 mm which is substantially the same as the thickness of the molded article. As a result, in the conventional valve gate, the charging time required for 25 to 30 seconds can be rapidly charged to 12 to 15 seconds.

Since it is large in this way, even if it ejects in a short time in order to shorten a shaping | molding cycle, appearance defects, such as a weld (silver) and silver, will not generate | occur | produce in the periphery of a gate. According to the present embodiment, the valve gate 10 is hot, and the sheet 12 which is tightened in a tapered shape is formed in the internal resin passage 11. The resin passage 11 is provided with a valve rod 13 reaching the plate 15 with a fixing frame. The valve rod 13 is driven in the axial direction by the hydraulic or pneumatic piston cylinder unit 14 incorporated in the fixed frame attachment plate 15, seated on the seat 15, and spaced apart. As a result, the resin passage 11 of the valve gate 10 is closed or opened. The locator ring 16 is attached to the fixed side frame attaching plate 15, and the spool 17 is a hot runner 18 provided between the fixed side frame attaching plate 15 and the fixed side mold 1. It is in communication with the resin passage 11 of the valve gate 10 through).

According to the present embodiment, the movable side mold 20 paired with the fixed side mold 1 is movably attached to the parting line P on the movable side die attach plate 21. It consists of the spacer block 22 and the core side nest 23 located inside it. More specifically, the spacer block 22 and the core-side nest are freely attached to the parting line P side by a plurality of guide pins 26, and the spacer block 22 is provided with a plurality of springs ( 27) is spring-operated to the parting line P side. Therefore, as shown in FIG. 1, in the frame open state, a predetermined compression zone D is generated between the rear surface of the spacer block 22 and the front surface of the movable side mold attachment plate 21. It is also possible to return the back surface of the core side nest 23 to be in contact with the front surface of the movable side mold attaching plate 21. The core-side nest 23 configured as described above is made of beryllium-copper alloy like the cavity-side nest 4 described above. Although not shown in FIG. 1, the core-side nest 23 has a heating medium of about 150 ° C and about 20 ° C. The heating and cooling pipes through which the refrigerant bodies flow alternately are provided.

A plurality of divided circumferential side wall side nests 30 and 30 are provided on the circumferential side portion of the core side nest 23 configured as described above. These peripheral side wall-side nests 30 and 30 are formed to slide four peripheral sides of a thick thick light guide plate, for example, and are slide-type to facilitate the extraction of the thick light guide plate. That is, according to the present embodiment, the thick light guide plate forms a square, but is slidable in the direction of narrowing and widening the area of the square. Since it is divided and slidable, in the frame open state shown in Fig. 1, the gap s between the inner side surfaces of the circumferential side wall side nests 30 and 30 and the outer circumferential end surface of the core side nest 23 is shown. ) (s) is present, but clamping eliminates this gap (s). The circumferential side wall-side nests 30 and 30 thus constructed are also made of beryllium-copper alloy, and inside thereof, a tube for heating and cooling in which a heating medium and a refrigerant body alternately flow is provided. On the parting line P side, a concave portion 31 is formed which engages with the preservation opening 9 of the stamper 8 at the time of clamping, and tapered surfaces 32 and 32 which are inclined toward the tip portion on the outer circumferential side thereof. Is formed. These tapered surfaces 32, 32 are in contact with the inclined surface 6 of the guide member 7 at the time of clamping, and the peripheral side nests 32, 32 are guided inward.

As described above, the cavity-side nest 4, the core-side nest 23, and the circumferential side-side nests 30, 30 are particularly different from the circumferential side-side nests 30, 30. The heating medium and the refrigerant body flow independently of the steps 23 and 23, but the heat-cooling source serving as the temperature control unit, the cooling unit, and the heat exchanger is not shown in FIG. In addition, according to the present embodiment, the thick light guide plate is withdrawn from the mold when the surface temperature of the molded article is cooled to about 65 ° C., for example, to shorten the molding cycle, but at such temperature, the pattern transferred to the surface of the thick light guide plate is retained by the heat of retention. There is a risk of deformation. Therefore, in the present embodiment, the thick light guide plate drawn out is cooled by an external cooling device. Although the external cooling device is not shown in FIG. 1, the external cooling device includes a lower cooling jig and an upper cooling jig representing a shallow box shape. These cooling papers are to be cooled by the refrigerant. In addition, the upper cooling jig has the same effect as the pressing lid, the thick light guide plate drawn out of the mold is placed on the lower cooling jig, and the upper cooling jig is put on it and inserted by both jigs, Applying an appropriate load in the pressing direction cools the thick light guide plate and corrects the warpage.

In addition, in order to prevent damage to the thick light guide plate, a protective sheet made of epoxy resin or the like may be provided on the surface of the cooling jig.

Next, the shaping | molding example of the thick light-guide plate using the said metal mold | die is demonstrated. The movable side mold 20 is clamped with respect to the fixed side mold 1. Then, the space | interval of the stamper 8 attached to the cavity side nest 4, and the core side nest 23 becomes 12 mm, for example. The tapered surfaces 32 and 32 of the circumferential side wall side nests 30 and 30 are guided by the tapered surfaces 6 and 6 of the guide members 7 and 7 by the clamping operation. , The inner surface thereof is in contact with the side surface of the core-side nest 23. Thereby, as shown in FIG. 2 (a), the imparting space sealed by the surface of the stamper 8 and the core side nest 23 and the inner surface of the peripheral side wall side nests 30 and 30 ( K) is configured. At this time, the compression table D is secured between the rear face of the spacer block 22 and the front face of the movable side die attach plate 21. Cavity side nests 4, core side nests 23, and circumferential side wall side nests 30, 30 are heated with, for example, 150 ° C heated water through a heat pipe.

Although not shown in the drawing, injection molding materials such as acrylic resin, polystyrene, polycarbonate, and the like, such as acrylic resin, are plasticized in a predetermined amount by conventionally known injection molding machines. In this way, injection is performed. The molten resin is filled in the given space K through the valve gate 10 in which the spool 17, the hot runner 18, and the valve rod 13 are open to avoid. The state in which the predetermined amount of charge is filled and the unfilled space remains is shown in Fig. 2A. The front end of the valve rod 13 is seated on the seat 12 by the hydraulic piston cylinder unit 14, and the resin passage 11 is closed. Thus, the movable die 20 is driven by the clamping machine in the clamping direction to start compression. When the resin is cooled and the resin is cooled, the compression zone D gradually approaches zero. In FIG. 2B, the state just before opening the frame is displayed in the state where the compression zone D becomes almost zero. When the compression is started, the cavity-side nest 4 and the core-side nest 23 have a large heat capacity in order to shorten the molding cycle, so that cooling may be started by, for example, 20 ° C cooling water. The circumferential side wall side nests 30 and 30 continue to flow the heating medium and maintain a higher temperature than the cavity side nest 4 and the core side nest 23. In the case of acrylic resin, since the solidification of the thick light guide plate is suppressed by maintaining the circumferential side wall side nests 30 and 30 at a high temperature of 120 to 130 ° C. above the glass transition point of acrylic, the imparting space K The compression operation is well followed by the volume shrinkage caused by the cooling process of the molten resin filled therein. Therefore, sag generated on the surface of the molded article is suppressed. When the compression is finished, the cooling medium flows to the circumferential side wall side nests 30 and 30 to cool. When the temperature of the molded article surface becomes 65 ° C., for example, the movable side mold 20 is opened. The state which opened the movable side metal mold | die 20 is shown in FIG. The thick light guide plate S is sucked out by, for example, an adsorption board, placed on a lower cooling jig of an external cooling device, and an upper cooling jig is mounted on the upper surface thereof, sandwiched by both jigs, and pressed by a pneumatic cylinder punch well or the like. By applying the proper load, the thick light guide plate is sufficiently cooled to the inside and the warpage is also corrected. As a result, a high quality thick light guide plate is obtained. The molding is performed in the same manner below.

The present invention can be modified in various forms without being limited to the above embodiment.

According to the embodiment described above, since the nests 4, 23, and 30 are provided, these nests 4, 23, and 30 are made of a material having high thermal conductivity, and are heated. Although the responsiveness of cooling can be improved and a heat pipe or a coolant pipe can be easily installed, it is clear that it can be implemented even without these nests 4, 23, and 30. In addition, the cavity side nest 4 or the core side nest 23 may be always cooled with cooling water at 30 ° C., for example, to shorten the molding cycle, and a heat insulating layer may be provided on the surfaces of these nests 4 and 23. By providing the heat insulation layer, it is possible to prevent the wall surface constituting the given space from the filled molten resin from being temporarily heated and inferior in transferability.

Moreover, when providing a stamper in a core side nest, it can also be implemented so that the thickness may be formed in 1-5 mm, and it adsorb | sucks by several magnet attached to the core side nest 23. As shown in FIG. In addition, a plurality of bosses may be provided on the back surface of the stamper, and these bosses may be attached by screws from the core-side nest 23. In addition, according to the above embodiment, although the stamper 8 is provided in the cavity side nest 4, a pattern may be directly formed in the cavity side nest 4 or the core side nest 23. It is also possible to form a pattern directly on the mold.

Examples (Comparative Examples) Various molding methods for mounting a light guide plate having a thickness of 12 mm by mounting a stamper having a dot formed on a cavity side nest, and a core side nest using a mirror-shaped mold (Comparative Example 1, Example) 1, 2, and 3), and compared with the molding cycle, the molded article quality as a light guide plate such as sag, transferability, and warpage was compared. The results are shown in Table 1. In addition, the deflection was calculated as the maximum thickness-minimum thickness by measuring the thickness of the square of the molded article which is liable to be drooped using the dial carry package. Test Example 1 displays Comparative Example 1, and Test Examples 2, 3, and 4 show Examples 1, 2, and 3, respectively.

Comparative Example 1: The molding was performed by a conventional injection molding method in which the molding temperature of the mold was set at 80 ° C. The quality of the molded product was about good quality, but the molding cycle was long as 372 seconds.

Example 1: The circumferential side wall side nest and the core side nest were made into 90 degreeC constant, and only the cavity side nest was compression-molded by heat-cooling between 85 degreeC and 40 degreeC. The molding cycle could be shortened to 260 seconds but the quality was insufficient in sag, transferability and warpage.

Example 2: The circumferential side wall side nest was made high at 110 degreeC, and the cavity side nest heated and cooled the core side nest between 83 degreeC and 38 degreeC between 104 degreeC and 45 degreeC, and compression-molded.

Although the molding cycle was shortened to 200 seconds and sag was slightly unsatisfactory, good results were obtained in terms of transferability and bending.

Example 3: The circumferential side wall side nest is heated and cooled between 130 ° C and 35 ° C, and the cavity side nest is heated and cooled between 110 ° C and 35 ° C, and the core side nest forms a heat insulating layer on the surface to 35 ° C. Cooled to compression molding.

It was confirmed that the molding cycle was shortened to 175 seconds when the temperature of the peripheral side nest was higher than the temperature of the cavity side nest, and the compression molding was shortened to 175 seconds, and the quality was improved in sag, transferability, and bending.

As described above, the present invention makes the compression step part of the constituent requirements of the invention, so that the resin material can be plasticized and the molding cycle can be shortened when the compression step is performed. At this time, the temperature of the cavity, the core and the circumferential sidewall is controlled during the injection process, so that, for example, it is heated, so that the flowability of the molten resin can be maintained high. By doing so, the unique effects of the present invention can be obtained in that the excellent light transferability, the occurrence of sagging on the surface of the thick light guide plate can be suppressed, and an optically excellent thick light guide plate can be obtained in a short molding cycle.

Further, according to another invention, since the imparting space is constituted by the nest, the effect of easily installing the heating or cooling means in these nests, the effect of being able to construct by the material suitable for the nest, and the like are further obtained. According to the invention provided with the stamper, in addition to the above effects, a thick light guide plate excellent in transferability can be obtained. In addition, according to the invention in which the heat insulation layer is provided in the cavity side nest or the core side nest, even if the cavity side nest or the core side nest is injected and filled with the cooling state at all times, the imparting space is temporarily filled with the hot molten resin filled. There is no such thing as being heated and inferior in transferability. Since the cavity side nest or the core side nest is always cooled, the effect of shortening the molding cycle according to the cooling time is further obtained.

Claims (14)

A hot runner and a hot runner in a provision space including a cavity side frame plate of the stationary side mold, a core side frame plate of the movable side mold, and a circumferential side wall blocking the circumferential side of the open space composed of the cavity side frame plate and the core side frame plate. An injection process of filling a predetermined amount of molten resin through a valve gate; A compression process of compressing the filled molten resin by driving the movable side mold in the clamping direction with respect to the fixed side mold by attaching the valve gate after the injection process; A molding method comprising a drawing step of cooling after the compression step to open a movable mold, and taking out a light guide plate on which a pattern of a light reflection layer is transferred by the cavity side mold plate or the core side mold plate, During the injection process, the temperature of the cavity side frame plate, the core side frame plate and the circumferential side wall is adjusted, and the compression process has a temperature of the cavity side frame plate and the core side frame plate. A method of forming a thick light guide plate, which is carried out in a higher state. The hot runner and the valve are provided in the cavity space of the cavity of the stationary side, the core side of the movable mold, and the circumferential side of the nest that blocks the circumferential side of the open space composed of the cavity side nest and the core side nest. An injection process for filling a predetermined amount of molten resin through a gate; A compression process of compressing the filled molten resin by driving the movable side mold in the clamping direction with respect to the fixed side mold by attaching the valve gate after the injection process; A molding method comprising a drawing step of cooling after the compression step to open a movable mold and taking out a light guide plate on which a pattern, which becomes a light reflection layer, is transferred by the cavity side nest or the core side nest. During the injection process, the temperature of the cavity side nest, the core side nest, and the circumferential side wall side nest is adjusted, and the compression process is performed such that the temperature of the circumferential side nest is nested between the cavity side nest and the core side nest. A method of forming a thick light guide plate, which is carried out at a temperature higher than the temperature. The method of claim 2, A method for forming a thick light guide plate, wherein the cavity is formed by forming a stamper for molding a pattern of a light reflection layer on the cavity side nest or the core side nest. The method of claim 2, A method of forming a thick light guide plate in which a stamper for transferring a pattern of a light reflection layer is transferred to the cavity side nest, and a heat insulation layer is provided on the surface of the core side nest, and the core side nest is molded while being always cooled by cooling water. . The method of claim 2, A stamper for transferring a pattern of a light reflective layer on the surface of the cavity side nest, and a heat insulating layer is provided on the back of the stamper and the surface of the core side nest, and the cavity side nest and the core side nest are cooling water. A method of forming a thick light guide plate that is molded while being always cooled by The method of claim 1, The heating and cooling of the cavity side frame plate, the core side frame plate, and the circumferential side wall is performed by a single heating and cooling device, and the switching timing of the heat medium and the refrigerant body is individually adjusted within the molding cycle. Forming method of light guide plate. The method of claim 2, The heating and cooling of the cavity side nest, the core side nest, and the circumferential side wall side nest are carried out by a heating and cooling apparatus of one type, and the switching timing of the heat medium and the refrigerant body is thickly adjusted separately in the molding cycle. Forming method of light guide plate. The method according to claim 1 or 2, The resulting thick light guide plate is placed on a cooled lower cooling jig, and likewise pressed by the cooled upper cooling jig to cool the thick light guide plate while correcting the warpage by applying a load in the direction of being inserted and pressed by both jigs. Method of forming a thick light guide plate. The fixed side mold and the movable side mold which can be compressed in the clamping direction after being filled with a predetermined amount of molten metal, and in the imparting space composed of these molds at the time of clamping, the hot runner through the valve gate through which the resin passage is opened and closed. Is communicating, When the molten resin is injected and charged into the imparting space from the hot runner, the mold is configured to transfer the light reflection surface to the thick light guide plate by the fixed side mold or the movable side mold. The stationary side mold and the movable side mold are heated and cooled, and the temperature of the circumferential side wall constituting the circumferential side of the provision space is controlled independently of the stationary side mold and the movable side mold. Mold for forming a thick light guide plate, characterized in that. After the fixed side mold and the predetermined amount of molten resin are filled, the movable side mold is compressible in the clamping direction, and the cavity side nest is formed in the stationary mold, the core side nest is formed in the movable side mold, and the cavity side nest is formed. Or a peripheral side wall side nest is provided in the circumferential side part of the said core side nest, and when the said movable side metal mold | die is clamped with respect to the said fixed side metal mold | die, it is provided by the said cavity side nest, the said core side nest, and the said peripheral side wall side nest. A space is formed, and the hot runner communicates with the given space through a valve gate through which the resin passage is opened and closed. When the molten resin is injected and charged into the imparting space from the hot runner, the mold is configured to transfer the light reflection surface to the thick light guide plate by the cavity side nest or the core side nest. The cavity side nest and the core side nest are to be heated and cooled, and the temperature of the circumferential side wall side nest is adjusted independently of the cavity side nest and the core side nest. Mold for molding. The method of claim 10, A mold for forming a thick light guide plate, wherein a stamper for transferring a pattern, which becomes a light reflection layer, is provided on a surface of the thick light guide plate on the cavity side nest. The method of claim 10, A mold for molding a thick light guide plate having a heat insulating layer provided on a surface of the core side nest. The method of claim 11, A mold for forming a thick light guide plate, wherein a heat insulation layer is provided between the surface of the core side nest, the back surface of the stamper, and the cavity side nest. The method of claim 10, A mold for forming a thick light guide plate, wherein the cavity side nest, the core side nest, and the circumferential side wall side nest are made of beryllium-copper alloy.

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