JP2016064579A - Method for manufacturing injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for an injection molding, capable of manufacturing an injection molding closer to a design value.SOLUTION: A method for manufacturing an injection molding includes: a mold clamping step of moving a slide core 53 to a predetermined position in a cavity SPC formed between a first die 51 and a second die 52 in a direction orthogonal to a mold clamping direction while mold clamping the first die 51 and the second die 52 or before and after the mold clamping; an injection step of injecting a molten resin to the cavity SPC; a cooling step of cooling the molten resin injected to the cavity SPC; and a mold opening step of separating the slide core 53 from the predetermined position in the direction orthogonal to the mold clamping direction while mold opening the first die 51 and the second die 52 or before and after the mold opening. A heat insulation layer 55 having a lower thermal effusivity than those of the dies 51 and 52 and the slide core 53 is formed on the surface on the cavity SPC side in the slide core 53, and a moth-eye pattern 56 is formed on the surface of the heat insulation layer 55.SELECTED DRAWING: Figure 2

Description

  The present invention is suitable for manufacturing an injection molded product closer to the design value.

  An injection-molded article is manufactured by injecting molten resin into a cavity formed by clamping a pair of molds and then cooling. As a mold used in such a method for producing an injection-molded product, there is a mold in which a mold part constituting a cavity is made of a low thermal conductive material (for example, see Patent Document 1 below).

  In the following Patent Document 1, a nesting made of a low thermal conductive material is used for a mold part constituting a cavity, and unevenness is formed on the surface of the nesting.

JP 2007-237445 A

  By the way, there is a demand to provide unevenness on the side surface which is a direction orthogonal to the direction in which the pair of molds are clamped. However, when such unevenness is provided on the side surfaces of a pair of molds forming a cavity, an injection molded product that is destroyed by being caught by the unevenness when the mold is opened and is far from the design value. There are prisoners who become.

  Therefore, the present invention intends to propose an injection molded product manufacturing method capable of manufacturing an injection molded product closer to the design value.

  In order to solve such a problem, the present invention is a method for manufacturing an injection-molded product, wherein the first mold and the second mold are clamped between before and after the first mold and the second mold are clamped. The slide core is moved to a predetermined position in the cavity formed between the first mold and the second mold along a direction orthogonal to the mold clamping direction in which the two molds are clamped. A mold clamping step, an injection step of injecting molten resin into the cavity, a cooling step of cooling the molten resin injected into the cavity, and opening the first mold and the second mold, Or a mold opening step of separating the slide core from the predetermined position along a direction orthogonal to the mold clamping direction before and after the mold opening, and on the cavity side surface of the slide core, A thermal insulation layer with a thermal permeability lower than the thermal permeability is formed. On the surface of the heat insulating layer is characterized in that the moth-eye pattern is formed.

In this manufacturing method, the slide core having the moth-eye pattern is clamped from a predetermined position in the cavity in conjunction with the opening of the first mold and the second mold or by a hydraulic cylinder or the like before and after the mold opening. It is separated along a direction orthogonal to the direction. For this reason, it is transferred to the molten resin by the moth-eye pattern, and the fine irregularities obtained by cooling the molten resin are broken by the moth-eye pattern of the slide core when the first mold and the second mold are opened. Is avoided.
By the way, the temperature of the slide core is generally difficult to control as compared with the first mold and the second mold, and the temperature of the slide core tends to be lower than the temperature of the first mold and the second mold. Therefore, unless the temperatures of the first mold and the second mold are set higher than the reference value, the transferability of the moth-eye pattern provided on the slide core cannot be maintained. Only productivity will be reduced.
In this regard, in the present invention, a heat insulating layer having a heat permeability lower than that of the slide core is formed on the surface of the slide core on the cavity side, and a moth-eye pattern is formed on the surface of the heat insulating layer. For this reason, rapid cooling in the moth-eye pattern is reduced by the heat insulating layer. Therefore, even if the temperature of the first mold and the second mold is not set higher than the reference value, the development of the solidified layer formed on the surface of the molten resin is delayed to improve the transferability of the moth-eye pattern. Can do.
Thus, an injection molded product manufacturing method capable of manufacturing an injection molded product closer to the design value is realized.

  The moth-eye pattern is preferably disposed at a flow end of the molten resin that flows in the cavity. Alternatively, it is preferable that the moth-eye pattern is disposed at a position farthest from an injection gate portion that injects molten resin into the cavity.

  As the molten resin flowing in the cavity is further away from the injection gate portion, the injection pressure at the flow end is lower than that at the injection gate portion side, and the transferability at the flow end tends to decrease. In this regard, when the moth-eye pattern formed on the surface of the heat insulating layer is disposed at the position farthest from the flow end of the molten resin or the injection gate, the injection pressure at the flow end is lower than that at the injection gate. However, the development of the solidified layer formed on the surface of the molten resin can be delayed to maintain the transferability of the moth-eye pattern.

  In addition, when the maximum distance between the surface of the first mold and the surface of the second mold that forms the cavity in the mold clamping step is less than 0.5 mm, the flow resistance of the molten resin is In particular, the injection pressure at the flow end tends to decrease. Therefore, when molding such a thin product, the significance of providing a heat insulating layer on the cavity-side surface of the slide core increases.

  When the injection-molded product is a light guide plate, if the injection pressure is increased to increase the transferability of the moth-eye pattern at the flow end, a large amount of residual stress remains in the molded product, causing a decrease in brightness and unevenness. As a result, the performance as a light guide plate is significantly reduced. Therefore, when the injection-molded product is a light guide plate, the significance of providing a heat insulating layer on the surface of the slide core on the cavity side is enhanced from the viewpoint of improving the yield of the light guide plate. In addition, since the light incident side end of the light guide plate tends to be slightly thicker, it can be relatively easily manufactured by a method of shearing a film obtained by film formation or the like.

  The molten resin may be polycarbonate.

  As described above, according to the present invention, there is provided an injection molded product manufacturing method capable of manufacturing an injection molded product close to the design value even if the injection molded product is thin.

It is a figure which shows the cross section along the thickness direction of a light-guide plate. It is a figure which shows the cross section of a metal mold unit. It is a flowchart which shows the manufacturing method of an injection molded product. It is a figure which shows the mode of an injection process. It is a figure which shows the mode of a mold opening process.

  Hereinafter, a preferred embodiment of a method for producing an injection molded product according to the present invention will be described in detail with reference to the drawings.

  The injection molded product in the present embodiment is a light guide plate, for example, a rectangular parallelepiped shape. FIG. 1 is a view showing a cross section along the thickness direction of the light guide plate 1. As shown in FIG. 1, a concavo-convex portion 10 is formed on one wide surface of the light guide plate 1 of the present embodiment, and a moth-eye pattern 20 in which concavo-convex portions are arranged with a period equal to or less than the wavelength of light is formed on the side surface S1 on the light incident side. It is formed.

  The unevenness level difference (height difference) in the moth-eye pattern 20 is about several hundred nm. In addition, although the space | interval and level | step difference of the unevenness | corrugation 10 are not specifically limited by the relationship with the moth-eye pattern 20, For example, they are about several micrometers-several tens of micrometers.

  Further, in the light guide plate 1 of the present embodiment, the thickness T1 of the end portion on the side surface S1 side that is the light incident side is larger than the thickness T2 other than the end portion. The thickness T1 of the end on the side surface S1 side of the light guide plate 1 is about 0.5 mm, and the thickness T2 other than the end is substantially constant at 0.4 mm or less.

  Although the kind of resin used for the light-guide plate 1 of this embodiment is not specifically limited, Specifically, a polycarbonate, a methacryl resin, a cycloolefin polymer, etc. can be illustrated.

  The resin used for the light guide plate 1 includes one or more of a release agent, a plasticizer, an antioxidant, an antistatic agent, a flame retardant, a lubricant, a colorant, an impact resistance enhancer, a filler, and the like. May be mixed.

  In the case where light is incident from the side surface S1 at the end of the light guide plate 1 on the light incident side, since the moth-eye pattern 20 is formed on the side surface S1, the light reflectance at the side surface S1 is high. Reduced. When light is incident from the side surface S1, the light is transmitted through the light guide plate 1 by total reflection. Further, the light hitting the unevenness 10 of the light guide plate 1 changes its path, and light having an angle smaller than the total reflection angle is emitted from the light guide plate 1.

  Next, a mold unit used when manufacturing the light guide plate 1 will be described. FIG. 2 is a view showing a cross section of the mold unit 50. As shown in FIG. 2, the mold unit 50 includes a first mold 51, a second mold 52, and a slide core 53.

  The first mold 51 and the second mold 52 are relatively movable in a mold clamping direction D1 approaching each other or a mold opening direction D2 separated from each other. In the present embodiment, the first mold 51 is a fixed mold, and the second mold 52 is a movable mold. FIG. 2 shows the first mold 51 and the second mold 52 in the mold-clamping state.

  An injection gate portion GT for injecting molten resin in a direction orthogonal to the mold clamping direction D1 is provided on the surface portion of the second mold 52 facing the first mold 51, and the injection gate portion The second mold 52 is clamped so that the GT is sandwiched between the first mold 51. Concavities and convexities 54 corresponding to the concavities and convexities 10 are formed on the surface of the second mold 52 facing the first mold 51.

  The slide core 53 is provided in a direction orthogonal to the mold clamping direction D1, and the second mold is placed in the cavity SPC formed between the first mold 51 and the second mold 52 in the mold clamped state. In association with the mold 52, it can slide in the approach direction D3 or the separation direction D4 perpendicular to the mold clamping direction D1. The cavity SPC is a space corresponding to the light guide plate 1 that is the injection molded product of the present embodiment.

  That is, when the first mold 51 and the second mold 52 are clamped, the front end surface of the slide core 53 reaches a predetermined position in the cavity SPC along the approach direction D3 orthogonal to the mold clamping direction D1. The slide core 53 is moved so as to enter. When the first mold 51 and the second mold 52 are opened, the front end surface of the slide core 53 leaves the cavity SPC from a predetermined position along the separation direction D4 orthogonal to the mold clamping direction D1. Then, the slide core 53 is moved.

  As a method for moving the slide core 53, for example, an angular pin is provided so as to protrude obliquely from the surface with respect to the first mold 51, and the first mold 51 and the second mold 52 are opened. Accordingly, there is a method of providing a hole in the slide core 53 that can move along the angular pin.

  In this embodiment, the predetermined position in the cavity SPC in which the tip surface of the slide core 53 is to be disposed is the side facing the injection port in the injection gate portion GT, and the molten resin flowing in the cavity SPC The flow end is the farthest position from the injection gate part GT.

  A heat insulating layer 55 is formed on the surface of the slide core 53 on the cavity SPC side, and a moth eye pattern 56 corresponding to the moth eye pattern 20 is formed on the surface of the heat insulating layer 55.

The heat insulating layer 55 has a heat permeability lower than that of the first mold 51, the second mold 52, and the slide core 53, and can withstand the injection pressure of the resin and the pressing force of the mold. Is done. The thickness of the heat insulating layer 55 is in the range of about 0.2 mm to 10 mm, and is determined by the heat permeability of the heat insulating layer. For example, when the heat insulation layer 55 is zirconia having a thermal permeability of about 2900 J / s ^0.5 m ² k, the thickness of the heat insulation layer is about 5 mm to 10 mm.

  Examples of the material of the heat insulating layer 55 include ceramics such as alumina and zirconia, glass, thermosetting resin, super engineering plastics, and the like. Further, as a method for forming the heat insulating layer 55, for example, there is a method of coating the heat insulating layer 55 by a thermal spraying method such as a plasma powder spray method or HVOF (High Velocity Oxygen Fuel), or a method of installing the heat insulating layer 55 as a nest. Can be mentioned.

  As described above, the moth-eye pattern 56 is a pattern in which concaves and convexes are arranged with a period equal to or shorter than the wavelength of light, and the step of the concaves and convexes is about several hundred nm. Examples of the moth-eye pattern 56 forming method include a plasma etching method.

  Next, the manufacturing method of the injection molded product in this embodiment is demonstrated. As shown in FIG. 3, the manufacturing method of the injection molded product according to the present embodiment includes a mold clamping process P1, an injection process P2, a pressure holding process P3, a cooling process P4, and a mold opening process P5 as main processes. .

<Clamping process P1>
In the mold clamping process P1, as shown in FIG. 2, the second mold 52 is moved along the direction approaching the first mold 51 so as to sandwich the injection gate portion GT, and the second mold 52 is moved. In conjunction with this, the slide core 53 is moved to a predetermined position in the cavity SPC along the approach direction D3 orthogonal to the mold clamping direction D1.

  Accordingly, the cavity SPC formed between the first mold 51 and the second mold 52 so as to sandwich the injection gate part GT is closed by the slide core 53.

<Injection process P2>
In this injection process P2, as shown in FIG. 4, a prescribed injection amount of the molten resin MS starts to be injected from the injection gate part GT into the cavity SPC formed in the mold clamping process P1. The injection pressure of the molten resin MS is, for example, in the range of 100 MPa to 300 MPa, and the temperature of the molten resin MS is set to a temperature equal to or higher than the glass transition temperature.

<Pressure holding process P3>
In this pressure holding step P3, after the specified injection amount of the molten resin MS is injected, the injection pressure of the molten resin is lowered from the injection pressure at the start of injection, and the reduced injection pressure is used for a certain period of time. Pressurized.

<Cooling process P4>
In the cooling process P4, the molten resin MS filled in the cavity SPC formed in the mold clamping process is cooled by cooling the first mold 51 and the second mold 52, for example.

<Mold opening process P5>
In this mold opening process P5, as shown in FIG. 5, the second mold 52 is moved along the direction D2 away from the first mold 51, and the mold clamping direction D1 is linked to the second mold 52. The slide core 53 is separated from a predetermined position in the cavity SPC along a perpendicular separation direction D4.

  At this time, the molded body CA solidified in the cavity by being cooled in the cooling step P4 is separated from the first mold 51 which is the fixed mold, and while being separated from the moth-eye pattern 56 of the slide core 53, the movable side mold It moves together with the second mold 52 that is a mold. After the molded body CA is removed from the second mold 52, unnecessary portions of the molded body are removed, and the light guide plate 1 as shown in FIG. 1 is obtained as an injection molded product.

  As described above, in the method of manufacturing an injection molded product according to this embodiment, the slide core 53 having the moth-eye pattern 56 is coupled to the cavity SPC in conjunction with the mold opening between the first mold 51 and the second mold 52. It moves away from the predetermined position along the separating direction D4 orthogonal to the mold clamping direction D1.

  For this reason, the fine unevenness (moth eye pattern 20) transferred to the molten resin by the moth-eye pattern 56 formed in the heat insulating layer 55 and obtained by cooling the molten resin becomes the first mold 51 and the second mold 52. It is avoided that the moth-eye pattern 56 of the heat insulating layer 55 is broken when the mold is opened.

  By the way, in general, the temperature of the slide core 53 is harder to control than the first mold 51 and the second mold 52, and the temperature of the slide core 53 is lower than the temperature of the first mold 51 and the second mold 52. Tend to be. Therefore, unless the temperature of the first mold 51 and the second mold 52 is set higher than the reference value, the transferability of the moth-eye pattern 56 provided on the slide core 53 cannot be maintained, and the temperature is set. If it is increased, productivity will decrease accordingly.

  In this regard, in the present embodiment, a heat insulating layer 55 having a heat permeability lower than that of the first mold 51 and the second mold 52 is formed on the surface of the slide core 53 on the cavity side, and the heat insulating layer 55. A moth-eye pattern 56 is formed on the surface.

  For this reason, the rapid cooling in the moth-eye pattern 56 is reduced by the heat insulating layer 55. Therefore, even if the temperature of the first mold 51 and the second mold 52 is not set higher than the reference value, the development of the solidified layer formed on the surface of the molten resin is delayed and the transferability of the moth-eye pattern 56 is improved. Can be improved. In this way, an injection molded product manufacturing method that can manufacture an injection molded product close to the design value even if the injection molded product is thin is realized.

  In addition, as the molten resin MS flowing in the cavity SPC is farther from the injection gate part GT, the injection pressure at the flow end is lower than that at the injection gate part GT side, and the transferability at the flow end tends to decrease.

  In the case of this embodiment, the moth-eye pattern 56 formed on the surface of the heat insulating layer 55 in the slide core 53 is disposed at the flow end of the molten resin MS that flows in the cavity SPC. The flow end is the farthest position from the injection gate part GT. Therefore, even if the injection pressure at the flow end is lower than that on the injection gate portion GT side, the development of the solidified layer formed on the surface of the molten resin can be delayed to maintain the transferability of the moth-eye pattern 56.

  In the present embodiment, the maximum distance between the surface of the first mold 51 and the surface of the second mold 52 that form the cavity SPC in the mold clamping process P1 is set to be smaller than 0.5 mm. Thus, when the cavity SPC is a narrow space, the flow resistance of the molten resin increases, and in particular, the injection pressure at the flow end tends to decrease. Therefore, when molding such a thin product, the significance of providing the heat insulating layer 55 on the surface of the slide core 53 on the cavity SPC side is enhanced.

  The injection molded product in the present embodiment is the light guide plate 1. In this case, if the injection pressure is increased in order to improve the transferability of the moth-eye pattern at the flow end, a large amount of residual stress remains in the molded product, and the performance as the light guide plate 1 becomes a factor of luminance reduction and unevenness. It drops significantly. Therefore, also from the viewpoint of improving the yield of the light guide plate 1, the significance of providing the heat insulating layer 55 on the surface of the slide core 53 on the cavity SPC side is increased. In addition, since the light incident side end of the light guide plate 1 tends to be slightly thicker, according to the method of manufacturing an injection molded product in the present embodiment, the film obtained by film formation or the like is comparatively produced by the manufacturing method. It can be manufactured easily.

  The above embodiment is merely an example, and the present invention is not limited to the above embodiment.

  For example, in the above embodiment, the heat insulating layer is not provided on the surfaces of the first mold 51 and the second mold 52 facing each other, but a heat insulating layer similar to the heat insulating layer 55 may be formed. In this way, it is possible to further improve the transferability of the molten resin by delaying the solidification of the molten resin injected into the cavity SPC.

  In the above embodiment, the second mold 52 is moved to the first mold 51 and clamped. However, the first mold 51 may be moved to the second mold 52 and clamped. In short, the first mold 51 and the second mold 52 may be clamped.

  In the mold clamping process P1 of the above embodiment, the slide core 53 is moved to a predetermined position in the cavity SPC while the first mold 51 and the second mold 52 are clamped, and in the mold opening process P5, the first mold 51 and the second mold 52 are clamped. The slide core 53 was moved to a predetermined position in the cavity SPC while the first mold 51 and the second mold 52 were opened. However, in the mold clamping process P1, the slide core 53 is moved by a hydraulic cylinder or the like after the first mold 51 and the second mold 52 are clamped. In the mold opening process P5, the first mold 51 and the second mold 52 are moved. The slide core 53 may be moved by a hydraulic cylinder or the like before the two molds 52 are opened. In the mold clamping process P1, the slide core 53 is moved by a hydraulic cylinder or the like before the first mold 51 and the second mold 52 are clamped. In the mold opening process P5, the first mold 51 and the second mold 52 are moved. The slide core 53 may be moved by a hydraulic cylinder or the like after the second mold 52 is opened.

    In the said embodiment, the light-guide plate 1 was applied as an injection molded product. However, an optical element other than the light guide plate 1 may be applied, or an article other than the optical element may be applied.

  The present invention can be used in the field of handling injection molded articles.

DESCRIPTION OF SYMBOLS 1 ... Light guide plate 50 ... Mold unit 51 ... 1st metal mold 52 ... 2nd metal mold 53 ... Slide core 54 ... Concavity and convexity 55 ... Thermal insulation layer 56 ... Moss eye pattern SPC ... Cavity GT ... Injection gate P1 ... Clamping process P2 ... Injection process P3 ... Pressure holding process P4 ... Cooling process P5 ... Die opening process

Claims (6)

While clamping the first mold and the second mold, or before and after clamping, along the direction perpendicular to the clamping direction in which the first mold and the second mold are clamped A mold clamping step of moving the slide core to a predetermined position in a cavity formed between the first mold and the second mold;
An injection step of injecting molten resin into the cavity;
A cooling step for cooling the molten resin injected into the cavity;
A mold opening step of separating the slide core from the predetermined position along a direction orthogonal to the mold clamping direction while opening the first mold and the second mold or before and after the mold opening. Prepared,
On the surface of the slide core on the cavity side, a heat insulating layer having a heat permeability lower than that of the slide core is formed,
A moth-eye pattern is formed on the surface of the heat insulating layer. The method for producing an injection-molded product according to claim 1, wherein the moth-eye pattern is disposed at a flow end of the molten resin flowing in the cavity. 3. The method of manufacturing an injection-molded product according to claim 2, wherein the moth-eye pattern is disposed at a position farthest from an injection gate portion that injects molten resin into the cavity. The maximum distance between the surface of the first mold and the surface of the second mold that form the cavity in the mold clamping step is set to be smaller than 0.5 mm. Item 4. A method for producing an injection-molded article according to any one of Items 3 to 3. 5. The method of manufacturing an injection molded product according to claim 4, wherein the injection molded product is a light guide plate. The method for manufacturing an injection-molded product according to any one of claims 1 to 5, wherein the molten resin is polycarbonate.

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