JP2001188113A - Optical reflective member made of thermoplastic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical reflective member made of a thermoplastic resin and having an optical reflective surface very excellent in specular properties. SOLUTION: The optical reflective member 10 has at least one optical reflective surface 13, a part 11 of the member constituting the entire region of the surface 13 has a hollow 14 formed by introducing a pressurized fluid and a part 12 of the member extended form the part 11 and constituting no optical reflective surface is solid. The optical reflective member 10 has a thickness decrease region 15 in which the thickness of the member decreases along the extension directions of the pressurized fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical reflecting member made of a thermoplastic resin and having an optical reflecting surface with extremely excellent mirror finish.

[0002]

2. Description of the Related Art Optical scanning reflectors used in digital devices such as copiers and laser beam printers,
Conventionally, optical reflecting members such as reflecting mirrors for automobiles and motorcycles, represented by rearview mirrors and reflectors,
Although it has been manufactured using glass, the shift to thermoplastic resin is advancing from the viewpoint of cost reduction, weight reduction, and the degree of freedom in shape due to the improvement in required functionality.

[0003] Generally, as a method of manufacturing a molded article made of a thermoplastic resin, a mold having a cavity is used.
An injection molding method has been used in which a molten thermoplastic resin is injected and filled into a cavity of a mold maintained at a constant temperature, and the thermoplastic resin in the cavity is cooled and solidified. However, such as an optical reflection member, (1) a thick molded product, (2) a molded product having an uneven thickness portion, or (3)
In the case of molding a long molded product, (1) and (2) correspond to the portion between the thick portion and the thin portion of the molded product, and (3) corresponds to the center portion and the end portion. As a result, there is a difference in the cooling rate of the molten thermoplastic resin in the cavity, and as a result, distortion tends to occur in the molded product. Therefore,
There is a problem that it is difficult to transfer the mold surface of the cavity having high mirror finish to the molded product with high accuracy, that is, it is difficult to enhance the mirror transfer accuracy.

[0004] In order to improve the mirror surface transfer accuracy in this type of molded article molding method, for example, the following measures have been conventionally adopted.

Injection compression molding method Glass transition temperature T of thermoplastic resin_gOver heated
Injection and filling of molten thermoplastic resin into the cavity of the mold
After sealing, the gate is sealed and the
Gradually cool the thermoplastic resin in the
Pressure is 0kg / cm ^Two-Take out the molded product when it becomes G
Molding method (see Japanese Patent Application Laid-Open No. 64-38421) A resin base material pre-processed to almost the final shape is formed by another mold.
Glass transition temperature T of base resin_gHeat again and heat
Molding method of gradually cooling to below the forming temperature
No. 19) Materials of two opposite mold surfaces provided in the cavity
Change the quality and surface roughness and melt the thermoplastic inside the cavity
Immediately before filling completely with the thermoplastic resin, the molten thermoplastic resin
Finish injection into the cavity and apply the pressure without applying pressure.
By cooling and solidifying the thermoplastic resin in the cavity
Mold surface on which the optical reflecting surface of the optical reflecting member is to be formed.
Adhesion to thermoplastic resin is higher than that of the other mold
(Japanese Patent Publication No. Hei 6-98642 and Japanese Patent Laid-Open No.
No. 51218) A mold for forming an optical reflecting surface of an optical reflecting member.
Keep the mold surface of the tee above the thermal deformation temperature of the thermoplastic resin
While cooling other mold surfaces,
Molding method for generating resin sink marks intensively on other mold surfaces
(Refer to JSME '94 Proceedings P237-P240)

[0006]

However, in the above method, it is difficult to obtain sufficient mirror-like transfer accuracy depending on the size of the shape of the optical reflecting member and the distribution of uneven thickness. In the methods (1) and (2), since the cooling is performed, the molding cycle is lengthened, and the productivity is reduced. In addition, in order to improve productivity, there are economical problems such as separate processes in which each of filling, slow cooling, and unloading processes can be continuously performed, and a need for a plurality of molds with high mirror surface accuracy. . In the method of (1), the adhesive force is reversed depending on the material of the mold portion constituting each mold surface (transfer surface and rough surface) of the cavity or the thermoplastic resin used, and the optical reflection surface of the optical reflection member is changed. Sinks occur in the portion of the thermoplastic resin that is in contact with the mold surface on which is to be formed. Further, when the timing of stopping the filling of the molten thermoplastic resin is shifted, the relationship between the adhesiveness between the molten thermoplastic resin and the mold surface is reversed, and the mold surface on which the optical reflecting surface of the optical reflecting member is to be formed. Sinking occurs in the portion of the thermoplastic resin that is in contact, or the amount of the molten thermoplastic resin to be filled in the cavity becomes insufficient. In the method of
There is a problem of stability such that the optical reflection member is warped due to a mold temperature difference.

Accordingly, it is an object of the present invention to provide an optical reflecting member made of a thermoplastic resin having an optical reflecting surface with extremely excellent mirror finish.

[0008]

An optical reflecting member made of a thermoplastic resin according to the present invention for attaining the above object has at least one optical reflecting surface, and covers the entire area of the optical reflecting surface. A hollow portion formed by introducing a pressurized fluid is provided in a portion of the optical reflecting member to be configured,
The portion of the optical reflection member that does not constitute the optical reflection surface and extends from the portion of the optical reflection member that constitutes the entire area of the optical reflection surface is solid, and the optical reflection member extends along the extension direction of the pressurized fluid. The optical reflection member is provided with a thickness reduction region where the thickness of the optical reflection member is reduced.

[0009] In the optical reflecting member of the present invention, the extension direction of the pressurized fluid (the direction in which the front part (front) of the pressurized fluid introduced into the molten thermoplastic resin moves). Since the thickness of the optical reflecting member is reduced in the optical reflecting member, the thickness of the optical reflecting member is reduced. Therefore, even if the direction of extension of the pressurized fluid is not one direction but extends in multiple directions, it is hollow. The extension speed of the part (the moving speed of the front part (front) of the hollow part in the molten thermoplastic resin when the hollow part is formed by the pressurized fluid) should be as equal as possible in the entire extension direction of the pressurized fluid. Becomes possible. That is, the hollow portion can be formed uniformly over the entire area of the optical reflecting member where the hollow portion needs to be formed. In the following, the portion of the optical reflecting member that forms the optical reflecting surface may be referred to as a hollow component for convenience, and the portion of the optical reflecting member that does not form the optical reflecting surface is hereinafter referred to as a convenience. It may be called a solid part.

On the other hand, when the thickness reducing region is not provided in the optical reflecting member, when the optical reflecting member is molded,
FIG. 15A shows a schematic partial cross-sectional view when the optical reflecting member is cut in the thickness direction, and FIG. 15B shows the optical reflecting member on a plane orthogonal to the thickness direction. As shown in a schematic partial cross-sectional view at the time of cutting, the hollow portion may not extend uniformly toward the solid component portion. That is, when the thickness of the optical reflecting member is made constant or increased along the direction of extension of the pressurized fluid, the extension direction of the hollow portion (the hollow portion is formed in the molten thermoplastic resin) Direction), the stretching speed is not uniform, and a portion where the formation of the hollow portion progresses and a portion where the hollow portion stops are generated. As a result, a resin pool is formed due to the difference in the extension speed, and it is difficult to uniformly form the hollow portion over the entire area of the optical reflection surface. As described above, when the hollow portion cannot be formed uniformly over the entire area of the optical reflecting surface, the mirror surface of the optical reflecting surface deteriorates.

Further, in the present invention, since the hollow portion is provided with the hollow portion, that is, the hollow portion formed by the introduction of the pressurized fluid during the production of the optical reflecting member has the hollow portion. Since the shrinkage of the thermoplastic resin in the portion can be suppressed and the hollow portion can be formed uniformly along the entire extension direction of the hollow portion, mirror-likeness can be achieved over the entire optical reflecting surface. A very good optical reflection member can be obtained.

[0012] In the optical reflecting member of the present invention, an injection molding die provided with a cavity having a die surface for forming an optical reflecting surface is used. The molten thermoplastic resin injected into the cavity is converted from the portion of the optical reflection member constituting the optical reflection surface (hollow portion constituting portion) to the portion of the optical reflection member not constituting the optical reflection surface (solid portion constitution) Direction), and the direction of extension of the pressurized fluid is changed from the portion of the optical reflection member (hollow portion constituting portion) constituting the optical reflection surface to the portion of the optical reflection member not constituting the optical reflection surface (hollow portion constituting portion). It is preferable to adopt a configuration in which the direction is toward the solid part.

The thickness reduction region is desirably provided at a portion of the optical reflection member constituting the optical reflection surface, but is not limited to this, and depends on the structure of the optical reflection member. I do.

In the thickness reduction region, the thickness of the optical reflection member at the portion where the thickness starts to decrease is t ₁ , and the thickness of the optical reflection member at the portion where the thickness reduction ends is t ₂ . In this case, it is desirable to satisfy 0.1 ≦ t ₂ / t ₁ ≦ 0.9, preferably 0.1 ≦ t ₂ / t ₁ ≦ 0.5. The thickness reduction ratio of the optical reflection member in the thickness reduction region (when the thickness is t and the axis along an arbitrary extending direction of the pressurized fluid is the x-axis, the thickness reduction ratio is Δt / Δx ) May or may not be constant. Further, the thickness of the optical reflection member in the thickness reduction region may be reduced stepwise. Alternatively, the thickness of the optical reflection member in the thickness reduction region may be reduced in an uneven shape. However, in these cases, it is preferable that the outer surface of the optical reflecting member in the thickness reduction region has no sharp corner. The thickness reduction ratio (Δt / Δx) of the optical reflection member in the thickness reduction region, or the reduction ratio of the thickness in a stepped or uneven shape is the same along the entire elongation direction of the pressurized fluid. Or it may be different along each direction of extension of the pressurized fluid. The thickness of the hollow component from the portion of the optical reflection member where the thickness reduction region ends to the solid component may be constant or may be increased.

The optical reflecting member made of a thermoplastic resin of the present invention uses an injection molding die provided with a cavity having a die surface for forming an optical reflecting surface.
Injecting a molten thermoplastic resin into the cavity;
(B) a step of introducing a pressurized fluid into the molten thermoplastic resin in the cavity to form a hollow portion in the portion of the optical reflecting member constituting the entire area of the optical reflecting surface; Until the plastic resin is solidified and cooled, a step of maintaining the pressure in the hollow portion within a desired pressure range, and (d) after removing the pressurized fluid in the hollow portion, open the mold and remove the optical reflecting member. And a removing step.

In the above method for producing the optical reflecting member of the present invention, the desired pressure range in the step (c) is set to a gauge pressure of 1 × 10 ⁵ Pa (1 kgf / cm ² -G).
Not less than 1 × 10 ⁷ Pa (1 × 10 ² kgf / cm ² -G), more preferably 5 × 10 ⁵ Pa (5 k
gf / cm ² -G) or more and 7.5 × 10 ⁶ Pa (7.5 × 1
0 kgf / cm ² -G) or less, more preferably, 1.0 × 10 ⁶ Pa (10 kgf / cm ² -G) or more and 5 × 10 ⁶ Pa (5 × 10 kgf / cm ² -G) or less at a gauge pressure. It is desirable. When the hollow portion is formed in the hollow portion, it is sufficient to maintain the inside of the hollow portion at a pressure sufficient to carry out the contraction of the thermoplastic resin in the hollow portion by the introduction of the pressurized fluid on the hollow side. For this reason, the pressure in the hollow portion may be maintained within a desired pressure range of such a relatively low pressure. When the desired pressure range (hereinafter, referred to as gauge pressure) is 1 × 10 ⁵ Pa or more, the hollow portion can be reliably formed in the hollow portion constituting portion. on the other hand,
By setting the desired pressure range to 1 × 10 ⁷ Pa or less, the pressure for pressing the molten thermoplastic resin in the cavity from the hollow portion against the mold surface for forming the optical reflecting surface is reduced by the thermoplastic resin. It is unlikely that an excessive pressure exceeding the pressure that causes shrinkage will occur, a residual stress will not easily occur in the optical reflecting member, and there is little problem in releasing the optical reflecting member from the mold. As a result, the specularity of the optical reflection surface of the optical reflection member is less likely to be impaired.

In the above method for producing an optical reflecting member of the present invention, the desired pressure range in the step (c) is set as follows:
(A) Until the thermoplastic resin in the cavity is solidified and cooled, the pressure may be controlled by the pressure of the pressurized fluid that pressurizes the hollow portion, or the pressurized fluid introduced in the step (B) may be used. Or (C) the mold may further include a movable core, and may be controlled by position control of the movable core. In the method (C), specifically,
The movement of the movable core increases the volume of the optical reflecting member and further increases the volume of the hollow portion.

In the optical reflecting member of the present invention, an injection molding die provided with a cavity having a mold surface for forming an optical reflecting surface is used, and the optical molding formed in the cavity is performed. It is preferable that there is only a gap of 1 μm or less per 10 mm ² of the optical reflection surface between the optical reflection surface of the reflection member and a mold surface for forming the optical reflection surface.

In the optical reflecting member of the present invention, the volume occupied by the solid portion is 5 to 5 times the volume of the optical reflecting member.
It is desirably 30%, preferably 5 to 15%.
If the optical reflecting member does not have a solid component,
In some cases, the hollow portion can be formed only in a part of the optical reflecting member constituting the optical reflecting surface, and as a result, the mirror surface of the optical reflecting surface may be deteriorated. Furthermore, when the solid portion is not formed at all, depending on the structure of the mold, the pressure in the hollow portion should be maintained in a desired pressure range until the thermoplastic resin in the cavity is solidified and cooled. In such a case, the pressure in the hollow portion cannot be maintained in a desired pressure range, and the specularity of the optical reflection surface may be reduced.

In the optical reflecting member of the present invention, the optical reflecting surface may be a flat surface or a flat surface depending on the specifications of the optical reflecting member.
It may have any three-dimensional shape such as a spherical surface, a spheroid, a paraboloid of revolution, and the like.

In the mold used in the optical reflecting member or the method of manufacturing the same according to the present invention, the resin injection portion (so-called gate portion) for injecting the molten thermoplastic resin into the cavity is provided with an optical reflecting surface. Can be provided as long as it is a part of the mold other than the mold surface for forming the pattern. When the optical reflecting member is manufactured, the molten thermoplastic resin injected into the cavity is a portion of the cavity where the portion of the optical reflecting member (hollow portion constituting portion) constituting the entire area of the optical reflecting surface is to be formed. Therefore, it is desirable to dispose the resin injection portion in the mold so as to flow toward the portion of the cavity where the portion of the optical reflection member (solid portion constituting portion) that does not constitute the optical reflection surface flows. .

In the mold used in the optical reflecting member or the method of manufacturing the same according to the present invention, the pressurized fluid introducing portion also includes:
Any part of the mold other than the mold surface for forming the optical reflection surface can be provided without any particular positional restrictions.
Specifically, the pressurized fluid introduction unit may be arranged near the resin injection unit, may be arranged separately from the resin injection unit, or may be arranged inside the resin injection unit. In addition, the number of pressurized fluid introduction sections is not limited.

The pressurized fluid used is a gaseous substance at normal temperature and normal pressure, and is preferably one which does not react with or mix with the thermoplastic resin used. Specifically, nitrogen gas, air, carbon dioxide gas, helium and the like can be mentioned, but from the viewpoint of safety and economy, nitrogen gas and helium gas are preferable. The timing of starting the introduction of the pressurized fluid into the molten thermoplastic resin in the cavity is preferably 0.1 second to 25 seconds from the start of the injection of the molten thermoplastic resin into the cavity. The lower limit of the time when the introduction of the pressurized fluid is started is that when the pressurized fluid is introduced into the molten thermoplastic resin in the cavity while being injected into the cavity of the molten thermoplastic resin, the introduced pressurized fluid is injected into the cavity. The time may be such that the molten thermoplastic resin is not blown off. On the other hand, if the introduction start time of the pressurized fluid exceeds 25 seconds, a desired hollow portion cannot be formed due to solidification of the molten thermoplastic resin in the cavity, and sinks occur on the optical reflection surface, and the mirror surface of the optical reflection surface May impair the performance. The timing of starting the introduction of the pressurized fluid into the molten thermoplastic resin in the cavity may be during injection of the molten thermoplastic resin into the cavity, simultaneously with the completion of the injection, or after the completion of the injection.

The volume of the molten thermoplastic resin to be injected into the cavity may be any volume that can mold a desired optical reflection member, and depends on the volume occupied by the hollow portion in the optical reflection member. That is, the volume of the molten thermoplastic resin to be injected into the cavity may be a volume that completely fills the cavity or a volume that does not completely fill the cavity. If desired, an overflow portion into which excess molten thermoplastic resin flows from the cavity may be provided in the mold in communication with the cavity, and the entire optical reflection surface may be formed as a hollow portion.

The thermoplastic resin used in the optical reflecting member of the present invention or the method for producing the same may be any thermoplastic resin, such as polycarbonate resin; olefinic resin such as polyethylene resin and polypropylene resin; polystyrene resin; Styrene resins such as resin, ABS resin and AES resin; methacrylic resins such as PMMA resin;
Polyoxymethylene (polyacetal) resin; polyamide resin such as polyamide 6, polyamide 66, polyamide MXD; modified polyphenylene ether (PPE) resin; polyphenylene sulfide resin; polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin Polyester resins; thermoplastic resins such as liquid crystal polymers, and polymer alloys composed of at least two or more of these thermoplastic resins. Among them, polycarbonate resin,
It is preferable to use a thermoplastic resin selected from the group consisting of a polyamide resin, a polyphenylene ether resin, a polyester resin, and a polymer alloy resin composition of a polycarbonate resin / polyester resin.

It is desirable to use an aromatic polycarbonate as the polycarbonate resin. In particular,
2,2 bis (4-hydroxyphenyl) -propane, 2,
A polymer obtained by a known method from one or more divalent phenolic compounds exemplified by 2-bis (3,5-dibromo-4-hydroxyphenyl) propane and a carbonate precursor exemplified by phosgene Can be exemplified. In particular, in the present invention, in addition to high rigidity, transparency,
From the requirements of heat resistance and impact resistance, the viscosity average molecular weight calculated from the melt viscosity of methylene chloride at 25 ° C is 1
5000 to 30000 aromatic polycarbonate resins are preferred.

A dye may be added to the optical reflecting member of the present invention or the thermoplastic resin used in the method for producing the same in order to give an arbitrary color tone. For example, it can be selected from those usually used for coloring thermoplastic resins, such as azo dyes, cyanine dyes, quinoline dyes, and perylene dyes. The compounding amount may be appropriately selected, for example, within a range that does not impair transparency. Further, within a range that does not impair the object of the present invention, for example, an effective expression amount of a stabilizer, a release agent, and an ultraviolet absorber may be blended in the thermoplastic resin.

In the optical reflecting member of the present invention, an optical reflecting film may be provided on the surface of the optical reflecting surface. In the method for manufacturing an optical reflection member according to the present invention, after the step (d), an optical reflection film may be formed on the surface of the optical reflection surface. The thickness of the optical reflection film may be a thickness that can effectively reflect light, and is at least 50.
nm, preferably 50 nm to 500 nm, more preferably 100 nm to 300 nm.
If it is less than 50 nm, the reflectivity may not be sufficient. On the other hand, if it exceeds 500 nm, the surface smoothness of the optical reflection surface may be reduced, and a problem may occur in the mirror surface.

As a material constituting the optical reflection film, for example, gold, platinum, silver, chromium, nickel, phosphorus nickel,
Examples thereof include metals such as aluminum, copper, beryllium, beryllium copper, and zinc, and metal compounds and alloys thereof. As the film forming method, (a) various kinds of vacuum evaporation methods such as an electron beam heating method, a resistance heating method, and flash evaporation; (b) a plasma evaporation method; (c) a bipolar sputtering method, a DC sputtering method, a DC magnetron sputtering method, and a high-frequency sputtering method Methods, magnetron sputtering method, ion beam sputtering method, bias sputtering method, etc. (d) DC (direct current) method, RF method, multi-cathode method, activation reaction method, electric field evaporation method, high frequency ion plating method And PVD (Physical Vapor Deposition) methods such as various ion plating methods such as a reactive ion plating method. From the viewpoints of reflectivity and cost, it is most preferable to form the optical reflection film from an aluminum vapor-deposited film obtained by vacuum-depositing aluminum.

The optical reflecting member of the present invention thus obtained is required to have high specularity, dimensional accuracy, light weight, safety, durability, and economy, and is required for electric and electronic parts, automobile parts, medical use, and security. It is an optical reflecting member suitable for many uses, such as for building, building materials, and household goods. As an embodiment of the optical reflection member of the present invention, a mirror can be given. More specifically, vehicle mirrors such as room mirrors, door mirrors, fender mirrors, mirrors built into speedometers, roof mirrors for cameras, optical mirrors for copiers,
An optical system mirror such as a polygon mirror for a laser beam printer can be exemplified. Further, as another form, a reflector can be cited. More specifically, headlamps, turnlamps, searchlights,
A reflector incorporated in a rotating light, an emergency light or the like can be exemplified.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings based on preferred embodiments. The optical reflecting member made of a thermoplastic resin to be manufactured in the examples and comparative examples was a circular rear-view mirror. Here, the outer dimensions of the optical reflecting member are 110 mm in diameter, the dimensions of the optical reflecting surface are 100 mm in diameter, and the optical reflecting surface is r = 100.
It has a radius of curvature of 0 mm. Further, the specularity of the optical reflection surface was evaluated by measuring a strain value based on JISD5705.

FIG. 1 is a schematic sectional view of the optical reflecting member 10. The optical reflecting member 10 has one optical reflecting surface 13 (one surface), and the hollow component 11 is provided with a hollow portion 14 formed by introducing a pressurized fluid. I have. In addition, a solid component 12 extends from the hollow component 11 toward the outer edge of the optical reflection member 10. Although the hollow component 11 and the solid component 12 are integrally manufactured from the same material,
In the schematic cross-sectional view of the optical reflecting member 10, the hatching pattern is changed in order to clearly distinguish the hollow part 11 from the solid part 12. On the other hand, traces of the injection of the molten thermoplastic resin (traces of the resin injection portion) 16 and a pressurized fluid are introduced into the central portion of the hollow component portion 11 where the optical reflection surface 13 is not formed. A trace 17 (trace of the pressurized fluid introduction part) remains.

In FIG. 1, the direction in which the pressurized fluid extends is indicated by an arrow. The extension direction of the pressurized fluid in the first embodiment is a direction of 360 degrees around the trace 16 of the resin injection portion. In the optical reflecting member 10, a thickness reduction region 15 in which the thickness of the optical reflecting member 10 decreases is provided along the extension direction of the pressurized fluid. Specifically, in the first embodiment, the thickness reduction region 15 coincides with the entire region of the hollow portion constituting portion 11. Then, the thickness t ₁ of the optical reflecting member 10 in the portion where the thickness of the optical reflecting member 10 starts to decrease (the portion of the optical reflecting member 10 near the trace 16 of the resin injection portion) in the thickness reduction region 15. Is 10 mm, and the optical reflection member (the portion of the optical reflection member 10 at the boundary between the hollow part 11 and the solid part 12) at the end of the reduction of the thickness of the optical reflection member 10. the thickness t ₂ is 3.5mm. The thickness of the optical reflection member 10 in the thickness reduction region 15 is gradually and smoothly reduced. The thickness reduction ratio (Δt / Δx) of the optical reflection member in the thickness reduction region 15 is the largest at the portion where the thickness of the optical reflection member 10 starts to decrease, gradually decreases, and gradually decreases. 10 is the minimum at the end of the thickness reduction.

Example 1 In Example 1, an injection molding machine equipped with an injection molding die 20 whose schematic sectional view is shown in FIG. 2 was used. Except for the heating cylinder 26, the components of the injection molding machine are not shown. Mold 20
Has a cavity 24, and a nest 2 forming a stationary mold portion 21 and a mold surface for forming the optical reflection surface 13.
3 is provided. When the fixed mold part 21 and the movable mold part 22 are clamped, a cavity 24 is formed. The mold 20 has a cavity 24
A resin injection section 25 is provided, which is open to the outside. The resin injection section 25 communicates with a heating cylinder 26. Further, a pressurized fluid introduction unit 27 is provided inside the distal end of the heating cylinder 26, and one end of the pressurized fluid introduction unit 27 opens toward the resin injection unit 25. On the other hand, the other end of the pressurized fluid introducing section 27 is connected to a pressurized fluid source 28. A check valve (not shown) is provided between the other end of the pressurized fluid introduction unit 27 and the pressurized fluid source 28 so that the molten thermoplastic resin moves toward the pressurized fluid source 28. It is configured not to flow backward. The resin injection section 25 is provided on a mold surface that is the center of the cavity 24 and does not form the optical reflection surface 13. The thickness of the cavity 24 where the hollow part 11 is to be formed is the largest in the vicinity of the resin injection part 25, and gradually decreases toward the part of the cavity 24 where the solid part 12 is to be formed. are doing. The nest 23, the fixed mold part 21, and the movable mold part 22 were made of a stainless steel material. The surface roughness _Ry of the mold surface of the insert 23 was set to 0.01 μm. The measurement of the surface roughness R _y was in accordance with JIS B0601.

In Example 1, an SH-100 injection molding machine manufactured by Sumitomo Heavy Industries, Ltd. was used as the injection molding machine, the heating cylinder 26 was heated to 300 ° C., and the mold temperature was raised to 1 °.
00 ° C. As the thermoplastic resin, a polycarbonate resin having a viscosity average molecular weight of 21,000 (trade name: Iupilon S-3000, manufactured by Mitsubishi Engineering-Plastics Corporation), which is a thermoplastic resin for injection molding, was used. Nitrogen gas was used as the pressurized fluid.

In the first embodiment, the thermoplastic resin is supplied into the heating cylinder 26,
After being kneaded and plasticized in 6 and melted, the molten thermoplastic resin 30 was injected into the cavity 24 of the mold 20 via the resin injection section 25. FIG. 3 schematically shows a state in which the molten thermoplastic resin 30 is being injected. The injection time is set to 7 seconds, and the volume of the injected molten thermoplastic resin is set to 8 times the volume of the cavity 24.
5%. And the cavity 2 of the molten thermoplastic resin.
Simultaneously with the completion of the injection into 4, the pressurized fluid is introduced into the molten thermoplastic resin 30 in the cavity 24 from the pressurized fluid introduction portion 27, whereby the hollow portion 14 is formed in the hollow component portion 11 ( (See FIG. 4). The pressure of the pressurized fluid when introducing the pressurized fluid into the molten thermoplastic resin 30 in the cavity 24,
3.5 × 10 ⁶ Pa (3.5 × 10 kgf /
cm ² -G).

Thereafter, the pressure in the hollow portion 14 is introduced through the pressurized fluid introducing portion 27 for 60 seconds after the completion of the injection of the molten thermoplastic resin into the cavity without performing the pressure holding operation. Controlled by the volume of pressurized fluid of 2.5
It was maintained at × 10 ⁶ Pa (2.5 × 10 kgf / cm ² -G). After that, the thermoplastic resin in the cavity 24 is
Cooled and solidified for seconds. During the 20 seconds, the pressurized fluid in the hollow portion 14 was released to the atmosphere via the pressurized fluid introduction portion 27. Then, the mold is opened, and the optical reflecting member 1 is opened.
0 was taken out. Optical reflection member 10 thus obtained
In the example, the volume of the hollow portion 14 was 15% of the volume of the optical reflecting member 10, and the volume occupied by the solid portion constituting portion 12 was 5% of the volume of the optical reflecting member 10.

Table 1 below shows the results of measurement of the specularity of the optical reflection surface of the optical reflection member thus obtained.

On the optical reflecting surface 13 of the molded optical reflecting member 10, an aluminum vapor-deposited film is formed by a vacuum vapor deposition method.
A mirror was formed by depositing a film having a thickness of 20 nm. As a result, the optical reflection member 10 had excellent image clarity (specularity) equivalent to that of a normal glass mirror, and the subject was clearly displayed.

(Example 2) The hollow portion 14 is kept until the thermoplastic resin in the cavity 24 is solidified and cooled (for 60 seconds after the injection of the molten thermoplastic resin into the cavity is completed).
Is controlled by the volume of the pressurized fluid when introduced through the pressurized fluid introduction unit 27, and 8.5 × 10 ⁶ Pa
(8.5 × 10 kgf / cm ² -G) An optical reflection member made of a thermoplastic resin was produced based on the same method as in Example 1 except that the temperature was maintained at (8.5 × 10 kgf / cm ² -G). Table 1 below shows the measurement results of the specularity of the optical reflection surface of the optical reflection member obtained as described above.

(Embodiment 3) The pressure in the hollow portion 14 is maintained in a desired pressure range until the thermoplastic resin in the cavity 24 is solidified and cooled. The range was controlled by the pressure of the pressurized fluid when the pressurized fluid was introduced into the molten thermoplastic resin in cavity 24.

More specifically, in the third embodiment, the thermoplastic resin is supplied into the heating cylinder 26, kneaded and plasticized in the heating cylinder 26 and melted, and then injected into the cavity 24 of the mold 20. The molten thermoplastic resin 30 was injected through the part 25. The injection time is 7 seconds, and the volume of the injected molten thermoplastic resin is 85% of the volume of the cavity 24.
And Then, simultaneously with the completion of the injection of the molten thermoplastic resin into the cavity 24, the pressurized fluid is introduced into the molten thermoplastic resin 30 in the cavity 24 from the pressurized fluid introduction part 27, and thus the hollow part 11 is A hollow portion 14 was formed. 1. The pressure of the pressurized fluid at the time of introducing the pressurized fluid into the molten thermoplastic resin 30 in the cavity 24 is expressed as a gauge pressure.
The pressure was set to 5 × 10 ⁶ Pa (2.5 × 10 kgf / cm ² -G).

Thereafter, the pressure in the hollow portion 14 is increased until the thermoplastic resin in the cavity 24 is solidified and cooled (60 seconds after the completion of the injection of the molten thermoplastic resin into the cavity). It was controlled by the pressure of the pressurized fluid introduced into it. The pressure in the hollow portion 14 immediately before opening the mold is 2.5 × 10 ⁶ Pa (2.5 × 10 kg
f / cm ² -G). After that, the pressurized fluid in the hollow portion 14 was released into the atmosphere via the pressurized fluid introduction portion 27, the mold was opened, and the optical reflection member 10 was taken out. In the optical reflecting member 10 thus obtained, the hollow portion 1
The volume of No. 4 was 15% of the volume of the optical reflection member 10. Table 1 below shows the measurement results of the specularity of the optical reflection surface of the optical reflection member obtained as described above.

(Embodiment 4) The pressure in the hollow portion 14 is maintained in a desired pressure range until the thermoplastic resin in the cavity 24 is solidified and cooled. A movable core 29 is further provided in place of the nest 23, and the movable core 29 is provided with a mold surface for forming an optical reflection surface. Then, the desired pressure range is controlled by controlling the position of the movable core 29.

Specifically, as shown in a schematic sectional view of FIG. 5, a movable core 29 which can be moved by, for example, a hydraulic cylinder (not shown) may be provided in the movable mold portion 22. . And in molding the optical reflection member,
At the time of mold clamping, the fixed mold part 21 and the movable mold part 22 are clamped so that the volume (V _C ) of the cavity 24 is smaller than the volume (V _M ) of the optical reflection member to be molded. In addition, the position of the movable core 29 in the cavity is controlled. Then, the molten thermoplastic resin is injected into the cavity (volume: V _C ) 24, and further, a pressurized fluid is introduced into the molten thermoplastic resin in the cavity 24, and the hollow part 14 is formed in the hollow part 11. Form. Thereafter, the movable core 29 is moved by the operation of a hydraulic cylinder (not shown) to gradually or continuously increase the volume of the cavity 24 up to the volume (V _M ) of the optical reflecting member to be molded.
Or increase it all at once. Thus, the cavity 24
Until the thermoplastic resin inside solidifies and cools, the hollow part 1
The pressure in 4 is maintained in the desired pressure range.

Comparative Example 1 In Comparative Example 1, an optical reflecting member having no hollow portion was formed without introducing a pressurized fluid. Specifically, the same injection molding machine, mold, and thermoplastic resin as those in Example 1 were used, and the thermoplastic resin was supplied into the heating cylinder 26, and kneaded and plasticized in the heating cylinder 26 to be melted. Thereafter, the molten thermoplastic resin was injected into the cavity 24 of the mold 20 via the resin injection section 25. The injection time was 7 seconds, and the volume of the injected molten thermoplastic resin was 100% of the volume of the cavity 24. After the injection of molten thermoplastic resin is completed, heating cylinder 2
From the 6 side, the holding pressure is 1 × 10 ⁸ Pa (1 × 10 ³ kgf /
cm ² -G), a pressure holding operation is performed for 60 seconds,
Next, the thermoplastic resin in the cavity 24 is applied for 20 seconds.
Cooled and solidified. Thereafter, the mold was opened, and the optical reflection member was taken out. Table 1 below shows the measurement results of the specularity of the optical reflection surface of the optical reflection member obtained as described above.

Comparative Example 2 The same as Comparative Example 1 except that after the injection of the molten thermoplastic resin was completed, the thermoplastic resin in the cavity 24 was cooled and solidified without performing a pressure-holding operation from the heating cylinder 26 side. The optical reflection member was produced by the method described in the above. Table 1 below shows the measurement results of the specularity of the optical reflection surface of the optical reflection member obtained as described above.

(Comparative Example 3) The volume of the molten thermoplastic resin injected into the cavity 24 was reduced to 9 times the volume of the cavity 24.
The hollow portion was formed only in a part of the optical reflecting member constituting the optical reflecting surface. Except for this point, an optical reflection member made of a thermoplastic resin was manufactured based on the same method as in Example 1. Table 1 below shows the measurement results of the specularity of the optical reflection surface of the optical reflection member obtained as described above.

[Table 1] Pressurized fluid Gas holding pressure Molding machine holding pressure Specularity measurement result Example 1 Yes 2.5 MPa No 2.0 Example 2 Yes 8.5 MPa No 3.0 Example 3 Yes 2.5 MPa None 2.5 Comparative Example 1 None None 100MPa 5.0 Comparative Example 2 None None None 6.6 Comparative Example 3 Yes 2.5MPa None 7.5

Although the present invention has been described based on the preferred embodiments, the present invention is not limited to these embodiments. The injection molding machine, the mold, and the thermoplastic resin used in the embodiments are merely examples, and can be appropriately changed.
The structure, shape, and dimensions of the optical reflecting member are also examples, and the design can be changed as appropriate.

FIGS. 6A to 6C and FIGS.
(C) shows a modified example of the thickness reduction region in the circular optical reflecting member 10A (the optical reflecting surface is a flat surface). still,
The cross-sectional shape of the thickness reduction region shown in FIGS.
The present invention can be applied to all optical reflecting members of the present invention.

In the example shown in FIG. 6A, the thickness reduction ratio (Δt / Δx) of the optical reflection member 10A in the thickness reduction region 15 is constant.

In the example shown in FIG. 6B, the thickness reduction region 15 starts from the portion of the optical reflection member 10A near the mark 16 of the resin injection portion, and starts from the hollow portion 1
1 and the thickness of the hollow portion 11A from the middle of the hollow portion 11 to the start of the solid portion 12 is constant. In some cases, the thickness of the hollow portion 11A from the middle of the hollow portion 11 to the start of the solid portion 12 may be increased. In FIGS. 6 and 7, the hollow portions 11A and 11B of the hollow portion are blacked out for clarity.

In the example shown in FIG. 6C, the thickness of the hollow portion 11B from the vicinity of the trace 16 of the resin injection portion to the middle of the hollow portion 11 is constant. From the end of the component portion 11B to the boundary portion with the solid component portion 12, the thickness reduction region 15
It has become.

In the example shown in FIG. 7A, the thickness of the portion 11B of the hollow component from the vicinity of the trace 16 of the resin injection portion to the middle of the hollow component 11 is constant, and the thickness reduction region Reference numeral 15 denotes a portion starting from the end of the portion 11B of the hollow portion, ending at a position on the outer peripheral side of the portion 11 of the hollow portion, and starting from a portion of the portion 11 of the hollow portion. The thickness of the portion 11A of the hollow component before the start of the process is constant.

In the example shown in FIG. 7B, the thickness of the optical reflection member 10A in the thickness reduction region 15 decreases stepwise. In the example shown in FIG. 7B, similarly to the example shown in FIG. 6B, the step-like thickness reduction region 15 is formed by the optical reflection member 10A near the mark 16 of the resin injection portion. Starting with the hollow part 11
The thickness of the hollow part 11A from the middle of the hollow part 11 to the start of the solid part 12 is constant. In some cases,
From the middle of the hollow part 11 to the solid part 1
The thickness of the portion of the hollow portion before the start of Step 2 may be increased. Further, the step-shaped thickness reduction region 15 may occupy all of the hollow portion constituting portion. Further, as shown in FIG. 6C, the thickness of the hollow part from the vicinity of the trace 16 of the resin injection part to the middle of the hollow part 11 is constant, and the hollow part The portion from the end of the portion to the boundary with the solid portion constituting portion 12 may be a step-like thickness reduction region 15, and similarly as shown in FIG. , Trace of resin injection part 1
6, the thickness of the hollow component portion in the middle of the hollow component portion 11 is constant, and the thickness of the step-like reduced thickness region 15 is constant.
Starts at the end of the hollow part, ends at a position closer to the outer peripheral side of the hollow part 11, and the solid part 12 starts at the middle of the hollow part 11. The thickness of the portion of the hollow portion may be constant.

In the example shown in FIG. 7C,
The thickness of the optical reflection member 10 </ b> A in the thickness reduction region 15 changes in an uneven shape. In the example shown in FIG. 7C, similarly to the example shown in FIG. 7A, the thickness of the portion of the hollow component from the vicinity of the trace 16 of the resin injection portion to the middle of the hollow component 11 is shown. The thickness-reduced region 15 having an irregular shape starts at the end of the hollow component portion and ends at a more intermediate position on the outer peripheral side of the hollow component portion 11. The thickness of the hollow part from the middle of the part 11 to the start of the solid part 12 is constant. Incidentally, as shown in FIG. 6B, the uneven thickness-reduced region 15 is formed by the trace 1 of the resin injection portion.
6, starting from the portion of the optical reflection member 10A and ending in the middle of the hollow component 11, and the portion of the hollow component from the middle of the hollow component 11 to the start of the solid component 12. The thickness of 11A may be constant. In some cases, the thickness of the hollow part from the middle of the hollow part 11 to the start of the solid part 12 may be increased. Further, the uneven thickness-reducing region 15 may occupy all of the hollow part. Further, as shown in FIG. 6C, the thickness of the hollow part from the vicinity of the trace 16 of the resin injection part to the middle of the hollow part 11 is constant, and the hollow part The portion from the end of the portion to the boundary portion with the solid portion constituting portion 12 may be the uneven thickness reduction region 15.

FIG. 8A is a schematic sectional view of a polygon mirror 10B which is an example of the optical reflecting member of the present invention. Also, the polygon mirror 10B shown in FIG.
FIG. 8B is a schematic cross-sectional view taken along line BB of FIG. 8 is a schematic sectional view similar to FIG. 8A of a polygon mirror 10C, 10D, 10E, 10F, which is a polygon mirror which is an example of the optical reflecting member of the present invention and has a slightly different structure from FIG. Are shown in FIGS. 9 and 10.

In the polygon mirror 10B shown in FIG. 8, a portion 1 of the optical reflecting member which does not constitute the optical reflecting surface
2A, a reduced thickness region 15 is formed. The portion 12A has a mark 16 of the resin injection portion, the hollow component 11 is located at the extension of the portion 12A, and the solid component 12 is located at the extension of the hollow component 11. I do. In the polygon mirror 10 </ b> C shown in FIG. 9A, a reduced thickness region 15 is formed in the hollow component 11. More specifically, the reduced thickness region 15 occupies the entire hollow component 11. Also in the polygon mirror 10 </ b> D shown in FIG. 9B, the thickness reduction region 15 is formed in the hollow component 11. More specifically,
The thickness reduction region 15 is provided from the middle of the hollow component 11 to the solid component 12.

The polygon mirror 10 shown in FIG.
In E, unlike the polygon mirror shown in FIG. 9A, the structure of the solid portion constituting portion 12 extends outward, and the hollow portion 14 extends further downward. FIG.
The polygon mirror 10F shown in FIG. 9B differs from the polygon mirror shown in FIG. 9A in the structure of the solid portion constituting portion 12 and extends outward, and the hollow portion 14 extends outward. Extending into the solid component 12. The thickness reduction region 15 is provided from the middle of the hollow component 11 to the solid component 12.

FIGS. 11 and 12 are schematic cross-sectional views of reflectors 10G and 10H, which are examples of the optical reflection member of the present invention. The reflector 10G shown in FIG. 11 and the reflector 10H shown in FIG. 12 are different in the structure of the hollow portion 14 and the solid portion 12. In the reflector 10G shown in FIG.
Is gradually increased, and
It is decreasing smoothly. The thickness of the optical reflection member in the thickness reduction region 15 is maximum near the mark 16 of the resin injection portion, gradually decreases, and at the boundary between the hollow component 11 and the solid component 12. Is the smallest. The reduced thickness region 15 occupies the entire region of the hollow component 11. In the reflector 10H shown in FIG. 12, the thickness of most of the hollow component 11 is constant,
A reduced thickness region 15 is provided in the hollow component 11 near the solid component 12. FIG.
In the reflector 10H shown in the figure, the direction of extension of the pressurized fluid is indicated by an arrow. At the boundary between the hollow part 11 and the solid part 12, the extension direction of the pressurized fluid changes by about 90 degrees. The thickness reduction region 15 is provided in the hollow component 11 where the extension direction of the pressurized fluid changes by about 90 degrees.

FIG. 13A is a schematic plan view of a mirror (mirror) 10J having a sector shape in a plan view, and FIG.
FIG. 13B is a cross-sectional view taken along the arrow BB of FIG.
In FIG. 13B, the hollow part 11 is shown by a dotted line. The thickness-reduced region 15 is a mark 16 of the resin injection portion.
Starting from the portion of the optical reflection member 10J in the vicinity,
Ending in the middle of the hollow component 11, the thickness of the hollow component 11A from the middle of the hollow component 11 to the start of the solid component 12 increases. The extension direction of the pressurized fluid is approximately 180 degrees around the trace 16 of the resin injection section.

FIG. 14A is a schematic side view of the optical reflecting member 10K composed of an optical reflecting mirror for a laser beam printer in the long side direction.
Optical reflection member 10K on a vertical surface including the bisector of the short side of
Is shown in FIG. 14B, and a schematic sectional view in the short side direction of the optical reflecting member 10K is shown in FIG. The extension direction of the pressurized fluid in the optical reflection member 10K goes from the right side to the left side in FIG. 14A (in other words, the trace 1 of the resin injection unit).
6 and one direction perpendicular to the paper surface of FIG. 14A (upper and lower sides), that is, a direction toward the left and right sides of the paper surface of FIG. 14C (in other words, resin (A direction branching within a direction of about 180 degrees from a direction heading in one direction from the trace 16 of the injection unit). A thickness reduction area 15A is provided from the right side to the left side of the sheet of FIG. 14A, and a thickness reduction area 15B is provided in the left and right direction of the sheet of FIG. 14C. .

[0064]

According to the present invention, a high-precision thermoplastic resin optical reflecting member having an optical reflecting surface (mirror surface) such as a mirror or a reflector can be prepared without requiring a separate process or a post-process. It can be manufactured efficiently and economically with stable, high quality.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an optical reflecting member (a rearview mirror) formed in an example.

FIG. 2 is a schematic cross-sectional view of an injection molding machine and a mold used in Examples and Comparative Examples.

FIG. 3 is a schematic cross-sectional view of a mold and the like for explaining a method of manufacturing the optical reflecting member of the present invention.

FIG. 4 is a schematic cross-sectional view of a mold and the like for explaining a method of manufacturing the optical reflecting member of the present invention, following FIG.

FIG. 5 is a schematic sectional view of a mold used in Example 4.

FIG. 6 is a schematic cross-sectional view of an optical reflecting member, showing a modified example of a thickness reduction region in the optical reflecting member.

FIG. 7 is a schematic cross-sectional view of an optical reflecting member, showing a modified example of a thickness reduction region in the optical reflecting member.

FIG. 8 is a schematic sectional view of a polygon mirror which is an example of the optical reflection member of the present invention.

FIG. 9 is a schematic cross-sectional view of a modified example of a polygon mirror which is an example of the optical reflecting member of the present invention.

FIG. 10 is a schematic sectional view of another modified example of the polygon mirror which is an example of the optical reflecting member of the present invention.

FIG. 11 is a schematic cross-sectional view of a reflector that is an example of the optical reflecting member of the present invention.

FIG. 12 is a schematic cross-sectional view of a reflector that is an example of the optical reflection member of the present invention and has a structure different from that of FIG. 11;

FIG. 13 is a schematic plan view and a cross-sectional view of a mirror having a fan shape in plan view.

FIG. 14 is a schematic sectional view of an optical reflection mirror for a laser beam printer, which is an example of the optical reflection member of the present invention.

FIG. 15 is a schematic cross-sectional view of an optical reflecting section for describing a problem when a thickness reduction region is not provided in an optical reflecting member.

[Explanation of symbols]

10, 10B, 10C, 10D, 10E, 10F, 10
G, 10H, 10J, 10K: optical reflection member, 1
1, 11A, 11B ... hollow part constituent part, 12 ...
Solid part constituent part, 13 ... optical reflection surface, 14 ...
Hollow part, 15, 15A, 15B ... thickness reduction area, 1
6 ... mark of resin injection part, 17 ... mark of pressurized fluid introduction part, 20 ... mold for injection molding, 21 ... fixed mold part, 22 ... movable mold part , 23 ... nesting, 24
..Cavity, 25 resin injection section, 26 heating cylinder, 27 pressurized fluid introduction section, 28
Pressurized fluid source, 29: movable core, 30: molten thermoplastic resin

Continued on the front page (72) Inventor Yoshihiro Chino 5-6-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Prefecture Inside the Technology Center of Mitsubishi Engineering Plastics Co., Ltd. (72) Inventor Kazuaki Ochiai 5-6-Higashi-Hachiman, Hiratsuka-shi, Kanagawa Prefecture No.2 Mitsubishi Engineering Plastics Co., Ltd. Technology Center F term (reference) 2H042 DA02 DA11 DB07 DB08 DC02 DC11 DD03 DD06 DD09 DE01 DE07 4F206 AF14 AH73 AM32 AM35 AR12 JA07 JL02 JM05 JN25 JN27 JQ81

Claims (4)

[Claims] An optical reflecting member made of a thermoplastic resin having at least one optical reflecting surface, wherein a pressurized fluid is applied to a portion of the optical reflecting member that constitutes the entire area of the optical reflecting surface. A hollow portion formed by the introduction is provided, and the portion of the optical reflecting member that does not constitute the optical reflecting surface that extends from the portion of the optical reflecting member that constitutes the entire area of the optical reflecting surface is medium. The thickness of the optical reflecting member is reduced along the direction in which the pressurized fluid extends, and the thickness of the optical reflecting member is reduced in the optical reflecting member. Element. 2. A method for manufacturing an optical reflecting member, comprising: using a mold for injection molding provided with a cavity having a mold surface for forming an optical reflecting surface; The plastic resin flows from the portion of the optical reflection member that forms the optical reflection surface to the portion of the optical reflection member that does not form the optical reflection surface, and the direction in which the pressurized fluid extends extends through the optical reflection surface. The thermoplastic resin optical reflecting member according to claim 1, wherein the direction is from the part of the optical reflecting member to be configured to the part of the optical reflecting member that does not form the optical reflecting surface. 3. The thermoplastic resin optical device according to claim 1, wherein the thickness reduction region is provided in a portion of the optical reflection member constituting the optical reflection surface. Reflective member. 4. In the thickness reduction region, the thickness of the optical reflection member at the portion where the thickness of the optical reflection member starts to decrease is set to t ₁ , and the optical portion at the end of the decrease in the thickness of the optical reflection member ends. 0.1 ≦ t ₂ / t, where the thickness of the reflective member is t _2
The optical reflection member made of a thermoplastic resin according to any one of claims 1 to 3, wherein ₁ ≤ 0.9 is satisfied.