JPS6258289B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to optical equipment parts, such as parts for cameras, projectors, telescopes, etc., which require dimensional accuracy and dimensional stability, and particularly to optical equipment parts made of filled thermoplastic resin, at least a portion of which is an exterior part. Here, camera parts, which are typical precision optical equipment parts, will be explained in detail. Since camera parts require sharp photographic images, dimensional accuracy and dimensional stability are particularly required. Dimensional stability is particularly important at high temperatures (e.g. 80°C inside a car under direct sunlight) and low temperatures (-30°C).
°C) and long-term conditions (considering the useful life of a camera to be 10 years, for example). This requirement is particularly strong in intermediate and high-end cameras, and for this reason, precision-machined aluminum die-casting, sheet metal, and the like with high precision and stability have been used. Acrylonitrile-butadiene-styrene (ABS)-based resin polycarbonate (PC) is used to reduce costs in parts of general-purpose small cameras and other devices that require less sharpness of photographic images, but it is used in intermediate-level cameras and above. is inappropriate. Recently, injection molded products of glass fiber-reinforced thermoplastic resins, such as glass fiber-mixed polycarbonate and glass fiber-mixed ABS resin, have been attracting attention as materials for optical equipment parts. Due to the presence of glass fibers in this material, dimensional stability is improved. However, in normal injection molding, the glass fibers are exposed on the surface, which makes them look bad and is not suitable for parts that form the exterior of a camera. It cannot be used as is and is limited to internal parts. In addition, if a screw-type lens cap is made of ABS resin or polycarbonate, the coefficient of thermal expansion is approximately 8 to 10 × 10 ^-5 /℃, so the screw may loosen and come off due to changes in the temperature environment. Warpage and twisting are likely to occur. Therefore, it is functionally unsuitable and cannot be put to practical use. When made from glass fiber reinforced thermoplastic resin, its coefficient of thermal expansion is 1 to 3.
Since the temperature is small at ×10 ^-5 /℃, I have never had a case where a screw loosened or came off due to environmental changes, but the appearance is poor and it cannot be put into practical use as it is. Furthermore, lens mounts have conventionally been made of metal, but if they are made of ABS resin or polycarbonate, their coefficient of thermal expansion is 8 to 10 x 10 ^-5 /°C, whereas lens mounts are made of metal. Since the coefficient of thermal expansion is 0.1 to 0.5×10 ^-5 /°C, there is a risk of cracking due to environmental changes. If it is made of glass fiber reinforced thermoplastic resin with a small coefficient of thermal expansion, it will not break due to environmental changes, but as mentioned above it will have a poor appearance. On the other hand, if the main parts such as the camera body or lens barrel could be made into an integral structure, it would be possible to reduce the cost to less than 1/5 due to the extreme reduction in the number of component parts and processing steps. Therefore, an object of the present invention is to provide an optical device component that satisfies all of the above-mentioned dimensional accuracy, dimensional stability, and appearance by specifying the synthetic resin used and forming a skin layer without fillers. It's about doing. That is, the present invention provides an optical device component made of a thermoplastic resin containing a filler, at least a portion of which is an external appearance portion, wherein the thermoplastic resin is an amorphous thermoplastic resin, and the thermoplastic resin substantially does not contain a filler. An injection-molded optical device part characterized by forming a skin layer of the invention. In particular, when the present invention is applied to a lens mount, it is possible to incorporate a slide mechanism therein because the filler (glass fiber) is not exposed on the surface. The present invention will be described in further detail below with reference to the accompanying drawings. An injection molding apparatus is shown in FIGS. 1 and 2. This example shows an inductor insertion method, and includes an injection molding machine and a high-frequency It consists of a high frequency induction heater consisting of an oscillating device 1 and an inductor 2 connected to the oscillating device 1 and placed near the mold surface. Thermoplastic synthetic resins for injection molding include, for example, acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer, acrylonitrile-butadiene-styrene-α-methylstyrene, and acrylonitrile-styrene copolymer.
Amorphous thermoplastic resins such as methyl methacrylate-butadiene-styrene (collectively referred to as ABS resin), polystyrene (PS), polycarbonate (PC), and polyphenylene ether (PPE). In addition, the filler mixed in with this is 5 to 20 mm in diameter.
5-40% by weight of μ glass fiber, preferably 20-40% by weight
30% by weight. Furthermore, as another filler,
CaCO ₃ , inorganic substances such as glass beads, and Fe,
Examples include metals and alloys such as Fe ₂ O ₃ , Al, and ZnO, and their oxides. The average particle size of such inorganic materials is 1 to 100μ, and the amount of inorganic filler is 20 to 100μ.
80% by weight. Such materials are injection molded, and at this time, as shown in the enlarged view of Fig. 2, the fixed side mold 4 is
A high-frequency induction heating inductor 2 is installed between the movable mold 5 and the movable mold 5. When the inductor 2 is inserted between the movable mold 5 and the stationary mold 4 and a high frequency is oscillated in the sandwiched state, only the mold surface (point A and point B) is oscillated as shown in Fig. 3. The temperature rises rapidly, and the temperature inside the mold (point C and point D) hardly rises due to high-frequency induction heating. In the case of the example shown in FIG. 3, the mold is not cooled with cooling water, but simply shows an example of the change over time in the temperature distribution of the mold due to high-frequency induction heating. Thereafter, the molds 4 and 5 are opened once, the inductor 2 is extracted from between the fixed side and movable side molds 4 and 5, the mold is closed again, and the above-mentioned filled thermoplastic resin is molded in the same manner as normal injection molding. Performs resin injection molding. FIG. 4 shows an optical microscope observation sketch of the cut surface in the thickness direction of the injection molded product thus obtained. The magnification is 440x. For reference, the same material was injection molded using the same mold at a mold temperature of 60°C without using inductor 2, and the same cross section was similarly observed and sketched.
It is a diagram. The magnification is 440x. In both drawings, the island pattern is made of glass fiber, and the horizontal line is the surface of the molded product. As is clear from a comparison between FIG. 4 and FIG. 5, in the case of the molded product according to the present invention, the filler glass fiber A' does not appear on the surface of the molded product, and at least 1~
It can be seen that a 30μ thick amorphous thermoplastic resin B' layer is formed on the surface layer of the molded product. In addition, as shown in Figure 4, when the glass fiber A' is located relatively close to the surface of the molded product, the thermoplastic resin B' layer forms the surface layer, and at the same time, the glass fiber causes some unevenness on the surface layer. Even when formed, compared to the case shown in FIG. 5, a molded product having a glossy appearance due to gentle unevenness is obtained. On the other hand, in the case of a normal molded product, as shown in Figure 5, the glass fiber A' protrudes from the surface of the molded product, or if the glass fiber A' is near the surface layer, that is, the resin on the mold surface Perhaps because the flow is disrupted, silver streak-like unevenness occurs on the surface, and only molded products with so-called dull and rough surfaces can be obtained. ASTM
The glossiness Gs (60°)% of the molded product was measured using D523 and was 98%. On the other hand, the molded product produced at a mold temperature of 660°C had a gloss level of 45%, demonstrating the smoothness and gloss of the molded product appearance of the present invention. In addition, the molded product of the present invention has less flow resistance during injection molding and is less likely to cause orientation distortion, so when the heating deformation temperature specified in JIS K6871 was measured, the heating deformation was lower than that of a normal molded product. The temperature is improved by 3 to 5°C, so-called practical heat resistance temperature is improved, and as a result of comparing the drop strength of molded products, practical toughness is also improved. Example 1 A lens cap was injection molded using ABS resin to which 30% by weight of glass fiber was added. Using NAK material (carbide mold steel), we created a mold that can form an externally threaded lens cap with a diameter of 52 mm, depth of 3 mm, and average wall thickness of 2.5 mm. The gate is a side gate and a mold with four cavities. The inductor was made by arranging 5 mm diameter copper tubes in a circular disk shape at 10 mm intervals, and in order to fix the shape, it was cast with a non-magnetic resin (epoxy resin) and solidified into a flat plate shape. As for the injection molding conditions, the cylinder temperature was set so that the temperature of the glass fiber reinforced ABS resin was 240°C. Before injecting the glass fiber reinforced ABS resin into the mold, the above-mentioned inductor is inserted between the molds, oscillated for 15 seconds with a 7KHz, 10KW high frequency oscillator, and then the mold is opened and the inductor is inserted into the mold. It was pulled out from the gap and the mold was closed again. In addition,
In this process, the temperature of the surface of the mold on which the molded product is to be formed is 120 to 130°C because only the vicinity of the surface of the mold is selectively heated by high-frequency induction heating immediately before injection molding of the resin. From the mold surface 3
The mold temperature within ~5 cm was 50-60°C. Thereafter, the resin was placed in a mold that was selectively heated only near the surface of the mold, and the resin was heated for 55 minutes in the same manner as in normal injection molding.
Injection was carried out for 10 seconds at an injection pressure of Kg/cm ² , and then cooling water was passed through the mold for 20 seconds, after which the molded product was taken out. The entire molding cycle was 60 seconds. The outer dimensions of the lens cap are 2500 shots, 1
Although 10,000 pieces were molded, it was within 52 ± 0.05 mm, and a molded product with stable dimensional accuracy and no twisting or warping was obtained. Also, the gloss Gs of the flat part of the lens cap
(60°)% was 98%, giving a lens cap with extremely high gloss and no flow marks, silver streaks, jetting, etc. Therefore, this lens cap did not need to be painted and finished as a finished product. In addition, the lens cap is rigid and has a small coefficient of linear expansion, so it
After being left for 2 hours, I repeated the cold/hot cycle test five times at 80°C, with one cycle of leaving it for 2 hours, but the lens cap did not crack or deform.
A lens cap was obtained that did not come off and had good cap sealing properties. Table 1 shows the performance of the camera component according to the present invention in comparison with conventional camera components.

[Table] In this table, judgment criterion A is used as a guide for dimensional accuracy (dimensions, warpage, etc.).If a part is 50 to 100 mm or more and has a deviation of 50 to 100μ or less from the design value, it is marked as ○, and if the deviation is 50 to 100μ or less from the design value, Cases were marked as △, and cases higher than that were marked as ×. Criterion B is -30 as a guideline for dimensional stability.
℃、2Hr80℃、2Hr cooling cycle test 5
Dimensional change after cycling and -30℃, 80
This is the dimensional change at °C.As an example, we comprehensively judge the deviation, twist, and hardness of the screw of a 52mm diameter external screw type lens cap (thread diameter 52mmφ, screw root diameter 50.5mmφ), and make a judgment of ○△×. did. Criterion C is based on visual judgment of appearance. As is clear from this table, the parts of the present invention have stable and excellent properties in all aspects of dimensional accuracy, dimensional stability, rigidity, appearance, and weight, and especially in terms of appearance, compared to conventional injection molded products. I was able to achieve excellent results.

[Brief explanation of the drawing]

Fig. 1 is a conceptual side view of an injection molding machine using an inductor sandwiching method used to manufacture parts of the present invention, Fig. 2 is a vertical sectional view of the mold and inductor, and Fig. 3 is a cross-sectional view of the injection molding machine of the inductor sandwiching method used for manufacturing parts of the present invention. FIG. 2 is a graph showing the temperature distribution of metal in an injection molding machine, FIG. 4 is an enlarged sketch of a cut surface of a part of the present invention, and FIG. 5 is a similar drawing of a conventional part. 1... High frequency oscillator, 2... Inductor,
3... Injection cylinder part, 4, 5... Mold.

Claims (1)

[Scope of Claims] 1. In an optical device part made of a filled thermoplastic resin, at least a portion of which is an external appearance part, the thermoplastic resin is an amorphous thermoplastic resin, and the thermoplastic resin substantially does not contain a filler. The plastic resin skin layer is integrally formed during injection molding without a bonding interface, resulting in dimensional accuracy of molding shrinkage of 0.3% or less, linear expansion coefficient of 3.5×10 ^-5 ℃ or less, and dimensional stability.
Glossiness Gs (60°)% specified by ASTM D523
Injection molded optical equipment parts characterized by having an appearance of 80% or more. 2. The optical device component according to claim 1, wherein the filler is glass fiber with a diameter of 5 to 20 μm, and the content thereof is 20 to 30% by weight. 3. The optical device component according to claim 1, wherein the filler is an inorganic filler with an average particle size of 1 to 100 μm, and the content thereof is 20 to 80% by weight. 4. The optical device component according to claim 3, wherein the inorganic filler is an inorganic material such as CaCO ₃ or glass beads, a metal or alloy such as Fe, Fe ₂ O ₃ , Al, or ZnO, or an oxide thereof. 5. The optical device component according to claim 1, wherein the amorphous thermoplastic resin is an acrylonitrile-butadiene-styrene resin, an acrylonitrile-styrene resin, polystyrene, polycarbonate, or polyphenylene ether.