JPS63112132A - Molding die for plastic lens - Google Patents

Abstract

PURPOSE:To uniformize the cooling condition of a lens and consequently contrive to mold a highly accurate plastic lens and to shorten the molding time of the lens by a method wherein heat insulating material is provided in at least one lens bush out of lens bushes, which form the surfaces of the lens. CONSTITUTION:A fixed retainer plate 2 and a movable retainer plate 3 are arranged opposite to each other with a parting line 1 as the mold registering face. A fixed lens bush 4 is fittingly fixed to the fixed retainer plate 2. On the other hand, a movable lens bush 5 is slidably fitted to the movable retainer plate 3 so as to be arranged opposite to the fixed lens bush 4. Heat insulating materials 6 are respectively provided in the lens bushes 4 and 5 in such a manner that the distance between the material and the molding surface of lens changes continuously. During the cooling process in the molding of the plastic lens, the cooling speed of the molten resin, which is injected to and filled into a cavity 7, can be controlled by the heat insulating materials 6 provided in the lens bushes 4 and 5. Accordingly, a favorable surface accuracy can be obtained and a highly accurate plastic lens can be provided. In addition, because no heater or the like is necessary, the cooling time of the lens can be shortened.

Description

[Detailed Description of the Invention] [Prior Art] Conventionally, a mold for molding a plastic lens, as shown in FIG. 7, has been used to adjust the cooling temperature to uniformly shrink the lens when cooling the lens. , a cartridge heater 33 is provided near the center of the mold 31, and a heat sensing device is provided directly below the heater.
There is a method that performs temperature gradient control that changes over time according to the shape of
In addition, as shown in Fig. 8, a mold cavity 41.4 in which the mold itself is made of a material with low thermal conductivity to suppress the cooling rate and eliminate lens distortion is used.
2 has quartz glass as the material, and the mold base 43
．． 44 and molded with an injection molding machine (
41F Opening and Closing No. 60-244515), and furthermore, although no example of application to lenses is shown, a part of the surface of the mold is formed of a resin material and the cooling rate is controlled by differentiating the cooling conditions. As shown in FIG. 9, a part of the cavity 53 corresponding to the protrusion of the rib 54 of the plastic product is made of resin or inorganic material.

There is a thermal insulating material 55 made of one kind of rubber material or a composite material (Utility Model Application No. 52-120173). Consisting of a layer 62 of thermally responsive material 63 deposited on a surface, the material having a thickness of approximately 5.0 m or less, its insulating properties are such that energy flux is added to the surface and the surface layer and body are There is a surface temperature control device for a solid body that is selected such that when the temperature of the body changes, at least 50% of the parallel temperature gradient formed between the surface layer and the body resides within this layer (see No. 1983-39114).

[Problems to be Solved by the Invention] However, among the conventional molds of this type, the one shown in FIG. 7 is due to the material of the mold itself.

The mold has good thermal conductivity, and the heat from the cartridge heater 33 easily diffuses, making it insufficient to create a temperature difference between the center and peripheral parts of the lens, which is the intended purpose.
This has the disadvantage that the temperature of the mold itself becomes high, and the time required to cool down the lens and thus the processing time becomes longer. Moreover, what is shown in FIG. 8 is a mold cavity material 41.4.
Since the lens 2 itself was made of a single material, quartz glass, it was impossible to create a temperature difference between the center and peripheral parts of the lens and to create a difference in cooling rate. Furthermore, Figure 9 and Figure 101i? Since the products shown in the above are intended to be molded products with uniform layer thickness, no such effect could be expected for plastic lenses with different wall thicknesses.

This invention aims to solve these drawbacks, and in the process of molding a plastic lens whose central and peripheral parts have different wall thicknesses, the temperature of the central part and peripheral part is controlled within the mold when the lens is cooled. The objective is to mold plastic lenses with high precision and shorten the molding time by making the cooling conditions uniform for the lenses by using heat insulating materials.

[Means for Solving the Problems] Fig. 1 is a conceptual diagram of a mold for molding a plastic lens according to the present invention, in which a fixed side mold plate 2 and a movable side mold plate 3 face each other with a parting line 1 as a mold matching surface. It is located. A fixed lens insert 4 is fitted and fixed to the fixed side mold plate 2, and a movable lens insert 5 is fitted to the movable side mold plate 3 so as to be slidable so as to face the fixed lens insert 4. has been done. A heat insulating material is provided in the lens insert 4 (5) so that the distance from the lens molding surface changes continuously. Note that 7 is a cavity and 8 is a runner.

[Function] In the plastic lens mold of the present invention, during the cooling process of plastic lens molding, the cooling rate of the molten resin injected and filled into the cavity 7 is set in the lens insert 4 (5). This can be adjusted with additional insulation.

[Example] Hereinafter, an example of the mold for molding a plastic lens of the present invention will be described based on the drawings.

(First Embodiment) FIG. 2 is an IF example of the mold for molding a plastic lens of the present invention, and FIG. 1 shows a lens insert, a is a sectional view of the lens insert, and b is a bottom view thereof.

In the figure, reference numeral 9 denotes a lens insert, and a base material 10 of this lens insert 9 is usually molded from stainless steel. A hole 12 for loading a heat insulating material corresponding to the shape of the heat insulating material 11 provided in order to obtain a cooling rate corresponding to the uneven thickness of the lens during lens molding is formed in the center of the base material 10. There is.

The tip of the heat insulating material 11 (on the lens molding surface side of the lens insert) lla uniformly cools the molten resin 15 (see Figure i3) filled in the cavity (not shown) according to the uneven thickness of the lens. It is formed into a desired shape, for example, a curved shape such as a spherical or parabolic surface, and is loaded into the hole 12 by press-fitting or the like. The heat insulating material 11 is made of a heat-resistant material such as epoxy resin, Bakelite, ceramics, heat-resistant rubber, etc. whose thermal conductivity is J to small compared to the base material 10 of the lens insert.

Note that the heat insulating material 11 can be loaded into the L enlarged 12 by press-fitting or the like, and the blind plug 13 shown by the two-dot chain line is screwed into the hole 12 to attach the heat insulating material 11.

Next, with reference to FIG. 3, the operation in the cooling process of molding the plastic lens of this embodiment will be explained.

In the figure, 15 is the molten resin immediately after being filled into the gearbity, and this molten resin 15 has a temperature of about 240 to 260°C, and is transferred to the base material 10 of the lens insert, which is kept at about 100°C. The heat of the molten resin 15 moves rapidly.

In such a case, the heat insulating material 11 provided on the base material 10 becomes a heat resistor, and the distance at which this insulating material 11 is close to the molten resin 15 is short at the center and gradually becomes farther away toward the periphery. Some of the heat also flows into the heat insulating material 11, but most of it diffuses to the surroundings. Therefore, the amount of heat held by the molten resin 15 moves to the lens insert 10, and a few seconds after filling with the molten resin 15, As the surface layer solidifies, the heat insulating material 1
Due to the effect of 1, the temperature of the lens insert 10 increases relatively in the central part where the heat capacity is small compared to the peripheral part, so the degree of heat diffusion of the molten resin 15 is slow in the central part of the lens and In this case, the cooling of the lens becomes faster, that is, the cooling of the lens is uniformly performed despite the uneven thickness of the lens.In Figure 0, arrows 16 indicate the state of heat movement and diffusion. In this case, the insulation material 1
Needless to say, the lower the thermal conductivity is used for 1, the slower the cooling will be.

In this way, in the case of conventional lenses with this type of shape,
Since solidification is fastest in the thin-walled portion at the center, the amount of absorbed radiation is small and the surface shape at the center tends to swell, but in the present invention, a uniform and smooth surface shape can be obtained by the above-mentioned action.

(Second Embodiment) Fig. 4 shows a second embodiment of the plastic lens molding mold of the present invention, in which a lens insert is shown, a is a sectional view of the lens insert, and b is a bottom view of the same. . Note that the same parts as those in the first embodiment are given the same numbers, and the explanation thereof will be omitted.

In the figure, reference numeral 11 denotes a heat insulating material filled in a hole 12 formed in the base material lO of the lens-containing f-. Insert the rear blind plug 18 into the hole 12 from the opening 12a of the hole 12.
The hole 12 is filled with the epoxy resin 11, and then the epoxy resin 11 is heated and hardened. In FIG. 1, reference numeral 19 indicates a screw for screwing the blind stopper 13, and reference numeral 14 indicates a pore through which an excessive amount of the injected epoxy resin 11 flows out.

In this embodiment, the same effect and curing as in the first embodiment can be achieved.

(Third Embodiment) FIG. 5 shows a third embodiment of the mold for molding a plastic lens according to the present invention, and is a sectional view of a lens insert. Note that the same parts as those in the second embodiment are given the same numbers, and the explanation thereof will be omitted.

In this embodiment, the distance between the center surface 11a of the heat insulating material 11 and the center surface 10a of the lens molding surface of the lens insert, that is, the shortest distance, is defined as d =
1.5 mm, the diameter of the heat insulating material is set to D=81, and the diameter of the tip curvature of the heat insulating material is set to R=15R.

In the above configuration, when the pressure inside the cavity of the molten resin was 600 Kgf/c+*2, the shortest distance d = 1.5 mm was able to provide sufficient strength for the lens insert.

In this embodiment, the same functions and effects as in the first embodiment can be obtained.

(Fourth Embodiment) The lens insert in this embodiment is the same as that in the third embodiment, and only the numerical values are different, so it will be explained with reference to FIG. 5.

In this embodiment, the distance between the central surface 11a of the heat insulating material 11 and the central surface 10a of the lens molding surface of the lens insert, that is, the shortest distance, is d = 0.5 mm, and the diameter of the heat insulating material is D = 6 m. The lens insert is constructed by setting the radius of curvature of the tip to R=8H.

In the above configuration, the pressure inside the cavity of the molten resin is 6
00 Kgf/cm2, the strength of the central surface 11a of the lens insert is insufficient, so by using the blind plug 13, the lens insert 7-1 is inserted through the heat insulating material L.
It also serves as reinforcement from the inside of 0.

In this embodiment, the same functions and effects as in the first embodiment can be obtained, and since the shortest path gId is shorter than in the third embodiment, the heat capacity of the relevant portion is small, and the heat insulating material It is possible to enhance the cooling delay effect of the thin part of the lens.

(Fifth Embodiment) FIG. 6 shows a fifth embodiment of the plastic lens molding mold of the present invention, which is a convex lens molding mold that is different from the concave lens molding molds in the first to fourth embodiments. In this figure, a is a cross-sectional view of the lens insert, and b is an explanatory view of the molded lens. Note that the same parts as those in the first embodiment are given the same numbers, and the explanation thereof will be omitted.

In this embodiment, the thickness of the molded lens 20 is thicker and uneven toward the center, so contrary to the above embodiment, the distance from the lens insert surface is increased from the periphery toward the center. The structure is such that the length gradually increases.

In this embodiment, due to the heat insulating material, the cooling rate is fast at the center of the lens insert, and on the contrary, the cooling rate becomes slower toward the periphery, so that the entire lens is cooled uniformly. be.

It should be noted that the present invention is not limited to the numerical values limited in the third and fourth embodiments, and can be set to appropriate numerical values depending on the desired lens shape.

Furthermore, in each of the above embodiments, since the lens insert can be formed from a metal that has been used conventionally, surface roughness and surface accuracy (processing accuracy of the mold itself) can be maintained, and the joints can be maintained. It never appears on the surface.

[Effects of the Invention] The present invention provides a heat insulating material for at least one of the lens inserts in the mold, so that heat diffusion in the lens insert material can be carried out in accordance with the shape of the lens, and the cooling process is Up,
Since it is possible to create a partial cooling rate difference, it is possible to obtain good surface accuracy even when applied to lens molds that conventionally had poor surface accuracy due to shrinkage differences, making it possible to produce highly accurate plastic lenses. This is something that can be provided. Furthermore, since the above-mentioned configuration is adopted and no heater or the like is required, the mold is not heated more than necessary, and the lens cooling time is also reduced.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of the present invention, Fig. 2 is a sectional view showing the first embodiment of the invention, Fig. 3 is an explanatory diagram showing the operating state of the invention, and Figs. The sectional view and bottom view showing the second embodiment, and FIG. 5 are the third embodiment of the present invention. 6A is a sectional view showing the fifth embodiment of the present invention, FIG. 6 is an explanatory view showing a molded lens, and FIGS. 7 to 1O are views of the prior art It is an explanatory diagram. 4...Fixed side lens insert 5...Movable side lens insert 6.11...Insulating material patent applicant Olympus Optical Industry Co., Ltd. agent Patent attorney Takeshi Nara, F-6, Insulating material No. 2 Figure 4 (a) 7Δko (b) Figure 5 Figure 7 Figure 8 Figure 4J 44 Figure 9 Figure 10 Hand thread completion 1j original (self-motivated) November 27, 1986 1.7JG items Indication of 1986 Patent Application No. 259645 2, Name of the invention Plastic lens mold mold 3, Relationship to the person making the amendment case Patent applicant address 2-43-2 Hatagaya, Shibuya-ku, Tokyo Name Name (037) Olympus Optical Industry Co., Ltd. Representative Toshibe Shimoyama 4, Agent, −“ − (1) “Claims” column of the specification, 5,;9
4-. -10,--7,- (2) "Detailed Description of the Invention" column 1':, +
i,? H, -j6, Contents of amendment (1) The claims are amended as shown in the attached sheet. (R) "Lens insert 10" written in specification section 8, line 15, section 8, line 16, and line 18 of the same page is corrected to "lens insert 9." 7. List of attached documents (1) Attachment 1 Attachment 2, Claims (1) In a mold for molding a plastic lens having different wall thicknesses at the center and periphery, at least one of the lens inserts forming the lens surface is A mold for molding a plastic lens, characterized in that a heat insulating material is provided on the outer surface of the plastic lens. A plastic lens molding mold according to claim 1, characterized in that, in the case of a concave lens, the heat insulating material has a distance from the lens molding surface of the lens insert at the center of the lens insert. The plastic lens mold according to claim 1 or 2, characterized in that the mold is provided at a minimum position and has a diameter of 30 to 60% of the outer diameter of the lens insert. 4) The mold for plastic lens molding according to claim 3, wherein the heat insulating material is provided at a position with a minimum distance of 0.2 to 2 mm from the molding surface of the lens insert. (Tsukasa) In the case of a convex lens, the heat insulating material is provided at a position where the distance from the lens molding surface of the lens insert to the lens molding surface is minimized in the peripheral portion of claim 1 or f.
A mold for molding a plastic lens according to item rS2. (0 The mold for molding a plastic lens according to any one of claims 1 to 5, characterized in that the heat insulating material has a lower thermal conductivity than metal.) The heat insulating material is epoxy. Heat-resistant plastics such as resins,
The mold for molding a plastic lens according to any one of claims 1 to 6, characterized in that the mold is made of ceramic heat-resistant rubber.

Claims (7)

[Claims] (1) For plastic lens molding, in which a mold for plastic molding has different wall thicknesses at the center and periphery, at least one of the lens inserts for molding the lens surface is provided with a heat insulating material. Mold. (2) The mold for molding a plastic lens according to claim 1, wherein the heat insulating material is provided in a thinner part of the plastic lens at a position closer to the lens than in a thicker part. . (3) In the case of a concave lens, the heat insulating material is provided at the center of the lens insert at a position where the distance from the lens molding surface of the lens insert is the minimum, and the heat insulating material is provided at a position 30 to 60 mm of the outer diameter of the lens insert. % of the diameter of the plastic lens mold according to claim 1 or 2. (4) The mold for plastic lens molding according to claim 3, wherein the heat insulating material is provided at a position where the minimum distance from the molding surface of the lens insert is 0.2 to 2 mm. . (5) In the case of a convex lens, the heat insulating material is provided at a position where the distance from the lens molding surface of the lens insert to the lens molding surface is the minimum in the peripheral part. Mold for plastic lens molding. (6) The plastic lens mold according to any one of claims 1 to 5, wherein the heat insulating material has a lower thermal conductivity than metal. (7) The plastic lens mold according to any one of claims 1 to 6, wherein the heat insulating material is a heat-resistant plastic such as an epoxy resin, ceramics, or bakelite heat-resistant rubber.