JP2006044246A - Injection mold and injection molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an injection mold enhanced in transfer properties, capable of effectively preventing the occurrence of warpage in a molded product and not damaging high cycling properties, and an injection molding method. <P>SOLUTION: The injection mold has a movable mold 10 and a fixed mold 20 and is adapted to the injection molding of an optical element comprising a resin material. Heat insulating materials 13 and 23 are interposed between core molds 12 and 22 and between surface processing layers 14 and 24 in both of the movable mold 10 and the fixed mold 20. Since the heat insulating materials 13 and 23 are arranged to both of the movable mold 10 and the fixed mold 20, the surface and back of the resin charged in a resin molding space 30 are thermally insulated without causing a temperature difference and the flowability of a resin is kept slightly longer than before temporarily. By this constitution, the transfer properties of a fine shape 14a are enhanced and the occurrence of warpage in the molded product is prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an injection mold and an injection molding method, and more particularly to an injection mold for molding a small and light optical element such as a lens and a light guide plate, and an injection molding method for manufacturing the optical element.

  In recent years, various developments in resin materials and injection molding technologies have led to the development of various types of small and lightweight lenses, prism plates (LED lighting plates used in mobile devices, etc.), light guide plates, etc. Demand for optical elements is increasing. In this type of optical element, there is a demand for a mold and a molding method capable of transferring a fine shape for diffraction, a fine shape such as a prism surface or a blaze surface, or a smooth surface with high accuracy. .

  In particular, in a molded product having a thin and fine shape such as a prism plate and a light guide plate, reduction of warpage as well as transferability of the fine shape is a problem. That is, since this type of optical element is incorporated in a narrow space in a cellular phone or the like, if warping occurs, the incorporation becomes extremely difficult or impossible.

  Conventionally, Patent Document 1 has proposed a molding die in which a ceramic heat insulating layer is provided between a die base material and a surface processed layer in order to achieve high-precision transferability. However, in this mold, only a heat insulating layer is provided between one mold base material for transferring the blaze surface and the surface processed layer, and there is a possibility that the molded product may be warped. ing.

On the other hand, in resin molding, shortening of the molding cycle (high cycle) is required, and it is important to meet this type of request. Even if the molding accuracy is improved by some means, it is not necessarily a preferable means as long as the high cycle is impaired.
JP 2002-96335 A

  Accordingly, an object of the present invention is to provide an injection mold and an injection molding method that can effectively prevent warping of a molded product while improving transferability and not impairing high cycle. There is to do.

  In order to achieve the above object, a first invention is an injection mold for injection molding an optical element made of a resin material, and at least a movable mold and a fixed mold are brought into close contact with each other. A mold core for forming a resin molding space and molding an optical surface is combined with a mold cavity arranged so as to surround the mold core, and the mold core is made of resin by a heat insulating material. A surface constituting the molding space is formed. The mold core may be composed of only a heat insulating material, or may be provided with a core mold that holds the heat insulating material.

  In the injection mold according to the first invention, since the mold core for molding the optical surface has a surface constituting the resin molding space formed by a heat insulating material, the resin injected into the resin molding space The front and back surfaces of the resin are kept warm without any temperature difference, and the fluidity of the resin is kept slightly longer than before, which improves the transferability of the optical surface and prevents the molded product from warping. . Therefore, the molded product can be easily incorporated even in a narrow space.

  Also, the molding cycle compared to the method of forcibly heating the mold to a higher temperature to maintain the fluidity of the resin (heat cycle molding) or the method of coating the resin molding space component with a bulk material with a large heat capacity Will not cause a long time.

  A second invention is an injection mold for injection molding of an optical element made of a resin material, and at least a movable mold and a fixed mold are in close contact to form a resin molding space. A mold core for molding a surface and a mold cavity arranged so as to surround the mold core are configured, and the mold core includes a heat insulating material, and is separately provided on the surface of the heat insulating material. The surface which comprises resin molding space is formed with the raw material of this, It is characterized by the above-mentioned. The mold core may be constituted only by a heat insulating material and a resin molding space constituting surface, or may be provided with a core mold for holding the heat insulating material.

  In the injection mold according to the second invention, since the mold core for molding the optical surface has a heat insulating material, the resin mold is similar to the injection mold according to the first invention. The fluidity of the resin injected into the space is kept slightly longer than before, so that the transferability of the optical surface is improved and the warping of the molded product is prevented. In addition, the molding cycle is not prolonged.

  In the mold for injection molding according to the first and second inventions, the heat conductivity of the heat insulating material is preferably 20 W / m · K or less. It is preferable to use any of stainless steel, titanium alloy, nickel alloy or ceramic as the heat insulating material.

  Further, a fine shape may be formed on the surface of the movable mold and / or the surface of the fixed mold. Furthermore, at least one mold core of the movable mold and the fixed mold may be provided with a flat molding transfer surface, or may be provided with a curved molding transfer surface. A fine shape may be formed on these molding and transfer surfaces.

  An injection molding method according to a third invention is characterized in that an optical element is molded from a resin material using the injection mold according to the first or second invention.

  A fourth invention is an injection molding method for molding an optical element made of a resin material using an injection mold having at least a movable mold and a fixed mold, and the movable mold and the fixed mold In any of the molds, an optical element is formed of a resin material with a heat insulating material interposed between the mold core and the surface processed layer.

  In the injection molding method according to the fourth invention, an optical element is molded from a resin material by interposing a heat insulating material between the mold core and the surface processed layer in both the movable side mold and the fixed side mold. Therefore, the front and back surfaces of the resin injected into the mold are kept warm without any temperature difference, and the fluidity of the resin is kept slightly longer than before, improving the transferability of the optical surface and the molded product. Warpage is prevented from occurring. Therefore, the molded optical element can be incorporated without difficulty even in a narrow space. In addition, the high cycle is not impaired.

  Hereinafter, embodiments of an injection mold and an injection molding method according to the present invention will be described with reference to the accompanying drawings. In the drawings showing the embodiments, common members are given the same reference numerals, and redundant descriptions are omitted.

(See the first embodiment, FIG. 1)
A mold 1 </ b> A according to the first embodiment includes a movable mold 10 and a fixed mold 20 as shown in FIG. 1. The movable mold 10 includes a template 11, a core mold 12, a heat insulating material 13, and a surface processing layer 14. The fixed-side mold 20 includes a template 21, a core mold 22, a heat insulating material 23, and a surface processing layer 24. The core molds 12 and 22, the heat insulating materials 13 and 23, and the surface processed layers 14 and 24 are referred to as mold cores, and the mold plates 11 and 21 are referred to as mold cavities.

  The surface processed layers 14 and 24 are finished corresponding to the front and back surface shapes of molded products (optical elements) such as lenses, mirrors, prism plates, and light guide plates, and constitute a resin molding space 30. In the first embodiment, fine shapes 14 a such as a diffraction grating, a prism surface, and a blazed surface are formed on a planar molding transfer surface of the surface processing layer 14 of the movable mold 10.

The mold plates 11 and 21 and the core molds 12 and 22 are made of a normal mold base material, for example, a metal material such as carbon steel or stainless steel. The heat insulating materials 13 and 23 are ceramics sprayed on the core molds 12 and 22, an organic material (heat resistant polymer) such as polyimide resin, a sintered ceramic that is a low thermal conductive material, a titanium alloy (Ti-6Al-4V, Ti-3Al-2.5V, Ti-6Al-7Nb, etc.), cermet (aluminum titanate, TiO ₂ -Al ₂ O ₃ ), stainless steel (martensite, austenite, etc.), nickel alloy (Inconel, FeNi) It is formed by. As the ceramic, zirconia, silicon nitride, titanium nitride, or the like can be used. The surface processed layers 14 and 24 are formed on the heat insulating materials 13 and 23 by plating a non-ferrous metal material, for example, nickel.

  The heat insulating materials 13 and 23 are not limited to the above-described materials, and are materials having a lower thermal conductivity than the mold plates 11 and 21 and the core molds 12 and 22, for example, a thermal conductivity of 20 W / m · Any material may be used as long as it is K or less.

(See the second embodiment, FIG. 2)
As shown in FIG. 2, the mold 1 </ b> B according to the second embodiment is obtained by forming a fine shape 24 a such as a diffraction grating, a prism surface, or a blaze surface on the surface processing layer 24 of the fixed-side mold 20. Other members and their materials are the same as those of the mold 1A of the first embodiment.

(Refer to the third embodiment, FIG. 3)
As shown in FIG. 3, the mold 1C according to the third embodiment has a diffraction grating, a prism surface, a blaze surface, etc. on any of the surface processed layers 14 and 24 of the movable mold 10 and the fixed mold 20. The fine shapes 14a and 24a are formed. Other members and their materials are the same as those of the mold 1A of the first embodiment.

(Refer to the fourth to sixth embodiments, FIGS. 4 to 6)
The following fourth to sixth embodiments mainly relate to the configuration of a mold core for molding an optical surface. Basically, it will be described as a modification of the mold 1A shown as the first embodiment, but it can also be applied as a modification of the second and third embodiments.

  FIG. 4 shows a fourth embodiment. In this mold 1A, the core mold is composed of the heat insulating materials 31 and 41, and the surfaces of the heat insulating materials 31 and 41 are the surface processed surfaces of the molded product.

  FIG. 5 shows a fifth embodiment. In this mold 1A, the core mold is composed of heat insulating materials 31 and 41, and surface processed layers 32 and 42 are provided on the heat insulating materials 31 and 41, respectively. The surface processed layers 32 and 42 are formed by plating a non-ferrous metal material, for example, nickel.

  FIG. 6 shows a sixth embodiment. In the mold 1A, the core molds 12 and 22 are provided with heat insulating materials 31 and 41, and the surfaces of the heat insulating materials 31 and 41 are used as surface processed surfaces of molded products. .

(Refer to the seventh embodiment, FIG. 7)
FIG. 7 shows a seventh embodiment, and this mold 1A is formed by forming a fine shape 14a with a molding transfer surface as a curved surface. Although the seventh embodiment is shown as corresponding to the first embodiment, even in the second to sixth embodiments, the molding transfer surface may be curved and a fine shape may be formed. Good.

(Molding method)
Here, an injection molding method using the molds 1A to 1C will be described.

  First, a resin (for example, amorphous polyolefin resin) melted at a predetermined temperature is filled into the resin molding space 30, and immediately after the filling is completed, the pressure holding step is started. The pressure holding step is a step of maintaining a predetermined pressure on the resin in order to compensate for the amount of shrinkage of the resin filled in the resin molding space 30 due to a decrease in temperature. After the pressure-holding step, the cooling step (natural cooling) is entered, and at least when the surface of the resin (molded product) is lowered to the heat deformation temperature or lower, the mold is opened, and the molded product is ejected with an eject pin (not shown).

  In the resin molding space 30, the resin begins to decrease immediately after the completion of filling. However, in the molds 1 </ b> A to 1 </ b> C, since the heat insulating materials 13 and 23 are arranged in both the movable mold 10 and the fixed mold 20, the front and back surfaces of the resin injected into the resin molding space 30. Is kept warm without temperature difference. Therefore, the fluidity of the resin in the resin molding space 30 is kept slightly longer than before, and the transferability of the fine shapes 14a and 24a is improved and the molded product is warped. Is prevented.

  In the mold 1 </ b> A, the fine shape 14 a transferred to the optical element that is a molded product is formed on the surface processing layer 14 of the movable mold 10. In this case, it is possible to prevent the turning of the fine shape and the occurrence of scratches due to the axis deviation that occurs when opening the mold 1A.

  In the mold 1 </ b> B, the fine shape 24 a transferred to the optical element that is a molded product is formed on the surface processing layer 24 of the fixed mold 20. In this case, it is possible to prevent occurrence of fine shape turning and scratching when the molded product is ejected by the eject pin.

  Further, in the mold 1C, the fine shapes 14a and 24a transferred to the optical element as a molded product are either the surface processed layer 14 of the movable mold 10 or the surface processed layer 24 of the fixed mold 20. It is also formed. In this case, a good optical element having a fine shape on both the front and back surfaces of the molded product can be obtained.

  In addition, as a method of maintaining the fluidity of the resin filled in the resin molding space 30, for example, a method of forcibly heating the mold to a higher temperature (heat cycle molding) in addition to using the mold according to the present invention. It is conceivable to employ a method of covering a member constituting the resin molding space with a bulk material having a large heat capacity.

  However, forcibly heating the mold to maintain the fluidity of the resin immediately after filling requires a forced cooling process before the molded product is taken out after the pressure-holding process, requiring a high cycle. Damage. Also, in the method using a bulk material, since it takes time to cool the bulk material, the high cycle is similarly impaired.

  On the other hand, the present invention enables preferable temperature control simply by providing a heat insulating material in the mold and keeping the temperature, and it takes a short time until the temperature of the molded product is reduced to a temperature at which it can be taken out. There is no loss.

(Other examples)
The injection mold and the injection molding method according to the present invention are not limited to the above-described embodiments, and can be variously changed within the scope of the gist.

  In particular, the details of the mold structure are arbitrary, and it is needless to say that the specific materials shown in the above-described embodiments are examples. 1 to 7, the mold 10 may be a fixed side, and the mold 20 may be a movable side. Alternatively, it may be a sleep rate type molding die provided with an intermediate die member.

It is sectional drawing which shows 1st Example of the metal mold | die which concerns on this invention. It is sectional drawing which shows 2nd Example of the metal mold | die which concerns on this invention. It is sectional drawing which shows 3rd Example of the metal mold | die which concerns on this invention. It is sectional drawing which shows 4th Example of the metal mold | die which concerns on this invention. It is sectional drawing which shows 5th Example of the metal mold | die which concerns on this invention. It is sectional drawing which shows 6th Example of the metal mold | die which concerns on this invention. It is sectional drawing which shows 7th Example of the metal mold | die which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A-1C ... Metal mold | die 11,21 ... Template 12,22 ... Core type | mold 13,23 ... Heat insulating material 14,24 ... Surface processed layer 30 ... Resin molding space

Claims (12)

An injection mold for injection molding an optical element made of a resin material,
At least a movable mold and a fixed mold are in close contact to form a resin molding space, and a mold core for molding an optical surface, and a mold cavity arranged so as to surround the mold core Composed of a combination,
The mold core has a surface forming a resin molding space formed of a heat insulating material,
Mold for injection molding characterized by   2. The injection mold according to claim 1, wherein the mold core includes a core mold for holding the heat insulating material. An injection mold for injection molding an optical element made of a resin material,
At least a movable mold and a fixed mold are in close contact to form a resin molding space, and a mold core for molding an optical surface, and a mold cavity arranged so as to surround the mold core Composed of a combination,
The mold core is provided with a heat insulating material, and a surface constituting a resin molding space with another material is formed on the surface of the heat insulating material,
Mold for injection molding characterized by   The injection mold according to claim 3, wherein the mold core includes a core mold for holding the heat insulating material.   The injection mold according to any one of claims 1 to 4, wherein the heat conductivity of the heat insulating material is 20 W / m · K or less.   6. The injection mold according to claim 1, wherein the heat insulating material is made of any one of stainless steel, titanium alloy, nickel alloy, and ceramic.   The injection mold according to any one of claims 1 to 6, wherein a fine shape is formed on a surface of the movable mold and / or a surface of the fixed mold.   The injection molding according to any one of claims 1 to 6, wherein the mold core of at least one of the movable mold and the fixed mold includes a planar molding transfer surface. Mold.   The injection molding according to any one of claims 1 to 6, wherein the mold core of at least one of the movable mold and the fixed mold includes a curved molding transfer surface. Mold.   The injection mold according to claim 8 or 9, wherein a fine shape is formed on the molding transfer surface.   An injection molding method comprising molding an optical element with a resin material using the injection mold according to any one of claims 1 to 10. In an injection molding method for molding an optical element made of a resin material using an injection mold having at least a movable mold and a fixed mold,
Molding an optical element with a resin material by interposing a heat insulating material between the mold core and the surface processed layer in both the movable mold and the fixed mold;
An injection molding method characterized by the above.

Images