JP2784164B2 - Plastic moldings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic molded product, and more particularly, to a plastic molded product having a rib and having a longitudinal sectional shape having a predetermined dimensional ratio, such as a copying machine and a facsimile machine. Optical reading system,
It is applied to mirrors and lenses for writing systems and housings that require high shape accuracy and internal uniformity.

[0002]

2. Description of the Related Art As a method of molding high-precision optical parts such as lenses and mirrors from plastic, mainly,
Injection molding and injection compression molding are used. In these molding methods, the plastic is heated to a temperature equal to or higher than the glass transition temperature Tg, and is injected and filled into a cavity of an injection mold at a predetermined temperature.
A predetermined pressure is applied for a predetermined time, the temperature is gradually lowered, the mold is opened, and the molded product is taken out. However, the molten plastic injected into the cavity has a non-uniform temperature distribution in the cavity due to a temperature difference from the cavity having thermal resistance, and a non-uniform pressure due to a viscosity change due to a temperature change. These temperatures and pressures change over time,
Furthermore, due to differences in the coefficient of thermal expansion between the molding resin material and the molding die, internal distortion occurs in the molded product, and sinks and distortions occur because the density distribution is not constant. It was difficult to obtain molded articles.

In order to solve such a problem, in order to plastically mold a high-precision optical component such as a lens, the present applicant has disclosed an "injection molding method" disclosed in Japanese Patent Publication No. Hei 5-73570 and Japanese Patent Laid-Open Publication No. Hei 4-163119. A "method of manufacturing plastic molded articles" by the gazette was proposed.

Japanese Patent Publication No. Hei 5-73570 aims to form a high-precision injection molded product such as a plastic lens by heating the cavity temperature of an injection mold to a temperature higher than the glass transition temperature of the molding material. After injection filling the cavity, the gate of the cavity is closed, the temperature of the injection mold is gradually cooled, lowered to the glass transition temperature, and the molding material is cured and molded in the cavity.

[0005] Also, JP-A-4-163119 discloses that
In order to produce a plastic molded product with a short cycle time, the resin heated to a temperature higher than the flowable temperature is injected into a mold held at a temperature lower than the heat deformation temperature of the resin, in order to produce a plastic molded product with a shorter cycle time. An injection molding step of performing gate sealing and heating the molded product obtained in the injection molding step to a temperature equal to or higher than the glass transition temperature, and holding this temperature for a predetermined time until the temperature becomes equal to or lower than the heat deformation temperature. The present invention relates to a method for producing a plastic by an aging step of slow cooling.

[0006] The molded articles described in the above-mentioned prior art are mainly described as plastic lenses, mirrors and the like, but their specific shapes are not described. However, a rib structure is often employed for a highly accurate plastic molded product. This is because the rib structure has the following features. (1) Improve the strength of molded products. (2) Uniform thickness of molded product. (Because the uniform thickness is easier to prevent sinking in molding, it is easier to obtain accuracy.) (3) Reduction of molding cycle. (4) Saving of molding materials. (5) Improved handling of molded products. (For optical parts such as lenses and mirrors)

[0007]

The advantages described above are obtained by adopting a rib structure for a plastic molded product. However, on the other hand, if a rib structure is adopted for optical components such as lenses and mirrors with higher precision, when the molding resin falls below the glass transition temperature Tg due to non-uniform deformation of the mold cavity piece due to the resin pressure, the pressure increases. It has been found from experiments by the present inventors that an imbalance occurs in the molded product, which causes a reduction in the precision of the molded product.

The present invention provides a molded article having a rib structure,
It is an object of the present invention to provide a molded product shape capable of obtaining high shape accuracy and internal uniformity.

[0009]

According to a first aspect of the present invention, there is provided a plastic molded product having ribs and requiring high shape accuracy and internal uniformity in a longitudinal direction including a rib of the molded product. The ratio b / a of the width dimension a to the width dimension b excluding the ribs of the molded article is 0.5 or less, and the height dimension c including the ribs of the molded article and the height dimension d excluding the ribs are: By setting the ratio d / c to 0.3 or more, it is possible to obtain a precision molded product having ribs and having high shape accuracy and internal uniformity.

[0010] The invention according to claim 2 has a high shape precision and a high cross-sectional shape of a plastic molded product having a rib and requiring high shape accuracy and internal uniformity only in a part of the molded product.
Only the portion requiring internal uniformity has the cross-sectional shape according to claim 1, and only the portion requiring high shape accuracy and internal uniformity has the cross-sectional dimension of claim 1, and the portion requiring no accuracy has the b dimension. Larger and smaller d dimensions reduce material.

According to a third aspect of the present invention, there is provided a molded product for molding a plastic optical component having a rib and requiring high shape accuracy and internal uniformity such as a lens and a mirror. The width dimension b other than the width and the height dimension d other than the ribs are the dimensions of the optically effective range of the lens / mirror.
To achieve high shape accuracy and internal uniformity, and improve the molding cycle.

According to a fourth aspect of the present invention, a plasticized resin is injected and filled into a mold cavity heated to a temperature not lower than the glass transition temperature of the resin in advance, and then the gate is sealed. The invention of claim 1 is made more effective by using a high-precision molded product manufacturing method based on a molding method in which the temperature is gradually cooled to a temperature equal to or lower than the thermal deformation temperature of the resin.

According to a fifth aspect of the present invention, there is provided an injection molding step of performing injection molding of a plasticized resin in a mold maintained at a temperature not higher than the thermal deformation temperature of the resin to perform gate sealing, Forming a mold filled with the resin so as to have a temperature equal to or higher than the glass transition temperature, holding the mold at a temperature equal to or higher than the glass transition temperature of the resin for a predetermined time, and gradually cooling the resin to a temperature equal to or lower than the thermal deformation temperature of the resin By using a highly accurate molded article manufacturing method by the method, the invention of claim 1 is made more effective.

According to a sixth aspect of the present invention, the material of the cavity piece of the mold is a steel-based material having a high longitudinal elastic modulus.
The amount of deformation of the cavity wall surface is reduced so that a highly accurate molded product can be easily obtained.

According to a seventh aspect of the present invention, the material of the cavity piece of the mold is made of a copper alloy having a moderately high elastic modulus and a high thermal conductivity to improve the molding cycle.

According to the eighth aspect of the present invention, the ribs of the molded article are provided with a taper so that the molded article is not deformed when the mold is released from the mold, thereby preventing the precision from being lowered due to the deformation.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to obtain a plastic molded product having high shape accuracy and internal uniformity having ribs, the present invention optimally determines the dimensional ratio of the cross-sectional shape in the longitudinal direction of the plastic molded product. First, a plastic molded product having a longitudinal cross-sectional shape without ribs and a plastic molded product with ribs are filled with molten resin in the cavity of an injection mold. The state of the shape change of the cross-sectional shape in the longitudinal direction of each molded product in the process from when the molded product is gradually cooled until the molded product is taken out will be described.

FIG. 1 is a view for explaining a change in the longitudinal sectional shape of a molded article having no ribs.
0 is a rectangular PQRS, and the width dimension of each side is PQ = RS =
a and the height dimension are respectively QR = SP = c.

When a high-pressure molten resin is injected and filled into a cavity (not shown) of a mold, the cavity wall surface is elastically deformed by a displacement x as shown by a broken line due to the internal pressure generated by the resin. When the mold is cooled from this state, the resin temperature falls accordingly. Since the coefficient of thermal expansion of the resin is larger than the coefficient of thermal expansion of the mold, when the resin temperature decreases, the resin pressure decreases, and the amount of elastic deformation (deflection) of the mold that is in proportion to the resin pressure decreases. At this time, even if the cross-sectional shape in the longitudinal direction of the molded product is an uneven thickness shape having a different cross-sectional area in the longitudinal direction, the deformation amount of the mold cavity wall surface does not change depending on the location and is constant, The amount of elastic deformation of the mold recovers as the resin pressure decreases in the cooling process, and becomes a rectangular PQRS indicated by a solid line, so that a relatively high-precision molded product is easily obtained.

FIG. 2 is a view for explaining changes in the cross-sectional shape in the longitudinal direction of a molded article having ribs. In the figure, reference numeral 1 denotes a rib portion, 2 denotes a rectangular portion, and 3 denotes a molded article surface portion. The shape is ABCDEFGH composed of a rectangular portion 2 including the molded product surface portion 3 and a rib portion 1 protruding from both ends of the rear surface of the rectangular portion 2. The length of the molded product surface portion 3, that is, the width direction including the rib portion 1 A of the side AB is a, the dimension in the height direction (between AB and EF) not including the rib 1 is d, the width of the side EF not including the rib 1 is b, and the height including the rib 1 Direction side AH
Is c.

When a mold having a rib 1 shown in FIG. 2 and having a longitudinal section is filled with a molten resin, the shape of the mold is
Therefore, even if the internal pressure P generated by the resin is constant, the amount of elastic deformation varies depending on the location, and the width AB including the rib portion 1 and the height including the rib portion 1 as shown by the broken line in the cavity of the mold. The displacement at BC = AH = c is X, the inner side EF excluding the rib 1 is 0.5X, and the inner side of the rib 1 (ED = F
In G), it becomes 0.5X.

From this state, the mold is cooled, and the temperature of the resin in the cavity is lowered, and the resin shrinks.
However, comparing the dimensions of the rectangular portion 2 and the rib portion 1, the width a of the rectangular portion 2 including the rib portion 1 is equal to the width dimension D of the rib portion 1.
Since C = HG = (ab) / 2, the heat shrinkage is also large. In the temperature range above the glass transition temperature Tg of the resin, the movement of the resin is relatively easy to occur, so the temperature decreases by slow cooling. Moves from the small rib portion 1 to the rectangular portion 2 having a large heat shrinkage, and there is no pressure difference between the rib portion 1 and the rectangular portion 2, and the pressure becomes uniform. The elastic deformation of the mold also decreases uniformly following the temperature decrease.

However, when the resin temperature is lower than the glass transition temperature Tg, the resin hardly moves. As a result, even if the temperature decreases, the resin cannot move from the rib portion 1 to the rectangular portion 2, and the rib portion 1 has a large displacement of the mold cavity wall surface, so that the pressure does not decrease. For this reason, pressure imbalance occurs in the cavity, and the precision of the molded product decreases. The degree of pressure imbalance in the cavity is determined by the dimensional ratio of the cross-sectional dimensions a, b, c, and d in the longitudinal direction of the molded product. For example, the closer to the cross-sectional shape in the longitudinal direction of the simple molded product without the rib shown in FIG. 1, the less likely it is for the imbalance in pressure to occur and the easier the accuracy of the molded product is to be obtained, but the longer the cross-sectional shape in the longitudinal direction shown in FIG. In the case of a molded product having a rib and easily causing pressure imbalance, accuracy is reduced.

The present inventors molded optical components requiring high surface precision, such as optical lenses and mirrors having ribs and having a longitudinal cross-sectional shape in the longitudinal direction, from plastic to obtain a usable cross-sectional shape with high precision. (B / a) ≦ 0.5 (1) (d / c) ≧ 0.3 (preferably (d / c) ≧ 0.5) (2) It was found that the dimensional ratio satisfied the following.

When (b / a)> 0.5, the width of the rib portion 1 becomes narrow, so that the pressure difference when the temperature of the rib portion 1 and the rectangular portion 2 decreases by a unit temperature becomes large, and the glass dislocation becomes large. When the temperature is equal to or lower than the temperature Tg, the pressure does not easily decrease. Also, (d /
c) <0.3, and when the height of the rib portion 1 becomes relatively high, the rib portion 1 and the rectangular portion 2 applied to the molded product surface portion 3
The effect of the pressure difference becomes large, and the precision of the molded product cannot be obtained. In particular, when there is uneven thickness in the longitudinal direction of the molded product, the pressure difference becomes large, and the precision of the molded product cannot be obtained.

FIGS. 3 and 4 are views for explaining the quality of the molding accuracy when the ribs shown in FIG. 2 have different heights and widths. 1 width (a
-B) / 2 is the widest in FIG. 4 and the narrowest in FIG. The height (cd) / 2 is the lowest in FIG. 4 and the highest in FIG. As a result, the shape accuracy and internal uniformity of the molded product are the highest in FIG. 4 and the lowest in FIG.

A, b, which satisfy the above equations (1) and (2),
The conditions for the c and d dimensions are not limited to the case where the cross-sectional shape in the longitudinal direction of the molded product shown in FIG. 2 is a shape having ribs 1 at both ends of the back surface of the rectangle 2, and is shown in FIGS. It has been confirmed that the above holds true in the case of the cross-sectional shape. In the drawings following FIG. 5, parts having the same operation as FIG.
The same reference numerals as in FIG. 2 are used.

The longitudinal cross-sectional shape of the molded product shown in FIG. 5 is such that the width dimension a including the rib 1 and the width dimension a −b) /
2. This is a molded product having an H-shaped cross section and having a rib 1 having a height (cd) / 2.

The cross-sectional shape in the longitudinal direction of the molded product shown in FIG. 6 has an arc-shaped portion 4, and has a width dimension a including a rib portion 1 serving as a lens portion having an axially symmetric shape in the width direction and the height direction. , Rib 1
Is provided with an arc-shaped portion 4 having an effective range b 'protruding toward the front and back sides of the lens portion at a portion having a width b not including the lens portion, and having a width of (ab) / 2 at both ends of the arc-shaped portion 4. , Height dimension is (c-
At d) / 2, a rib 1 having an effective range height d 'corresponding to the effective range width b' of the circular portion 4 is provided.

The cross-sectional shape in the longitudinal direction of the molded product shown in FIG. 7 is axially symmetrical in the width direction and the height direction and is long in the width direction. Dimensions (a
A plurality of ribs 1 of -b) / 2 and a dimension (cd) / 2 in the height direction are arranged at equal intervals on the front and back surfaces.

In the longitudinal section of the molded product shown in FIG. 8, a rib 1 having a height (cd) protrudes radially from each vertex of the regular hexagonal section 5. Where dimension c
Is the distance from the center O of the regular hexagonal cross section 5 to the height surface of the rib portion 1, and the dimension d is the distance from the regular hexagonal cross section 5 to the contact point of the rib portion 1. Also, width a including the rib portion a
Is the maximum distance between the height surface portions of the adjacent ribs 1, and the width b not including the ribs 1 is the distance between the adjacent ribs 1 of the regular hexagonal cross section 5.

The cross-sectional shape in the longitudinal direction of the molded product shown in FIG. 9 is symmetrical only in the height direction, the width of the rib 1 is (ab) / 2, and the maximum height of the rib 1 is The size is (c-
d) / 2, and accordingly, the rectangular portion 2 not including the rib portion 1 has the minimum height dimension d, and the height dimension changes stepwise according to the width dimension a including the rib portion 1. It has a complicated shape.

As described above, the molded product having the ribs shown in FIGS. 2 to 9 and having a longitudinal sectional shape has the lengths of a, b, c, and d satisfying the conditions of the above equations (1) and (2). By selecting the dimensional ratio, a highly accurate molded product can be obtained.
The part giving the dimensional ratio satisfying the expression (2) does not have to be applied to all the molded products, but only to a portion requiring a high surface accuracy, such as the molded product surface 3. For example, the housing is a mounting surface for mounting other parts (corresponding to claim 2).

The cross-sectional shape of an optical component such as a lens or a mirror that requires high shape / dimensional accuracy and internal uniformity is, for example, an arc-shaped portion 4 shown in FIG. Width dimension b and height dimension d other than rib 1
Uses the dimensions of the optically effective range of optical components such as lenses and mirrors. In the example shown in FIG. 6, the effective width dimension is b 'and the effective height dimension is d'. By applying such an effective width dimension, only the optically effective portion has high shape accuracy and internal uniformity. (See claim 3).

Further, a molded article having a longitudinal cross-sectional shape having a rib defined by width dimensions a and b and height dimensions c and d satisfying the above-mentioned equations (1) and (2) is provided by the above-mentioned feature. Fairness 5-7
No. 3570, "Injection molding method", that is, width dimensions a and b of a mold previously heated to a temperature equal to or higher than the glass transition temperature of a resin, satisfying the above equations (1) and (2).
Claims 1. A mold formed by injection-filling a plasticized resin into a cavity having a height dimension c or d, sealing the gate, and gradually cooling the temperature of the mold to a temperature equal to or lower than a thermal deformation temperature of the resin. The effect of the first invention becomes more effective,
It is possible to obtain a molded product having high dimensional accuracy and ribs with uniform inside (corresponding to claim 4).

Furthermore, a plastic manufacturing method disclosed in Japanese Patent Application Laid-Open No. 4-163119, that is, an injection molding step of performing injection molding on a mold maintained at a temperature equal to or lower than the thermal deformation temperature of a resin to perform gate sealing, The temperature of the mold filled with the resin is increased so that the temperature is equal to or higher than the glass transition point of the injection-molded resin, the temperature is maintained at a temperature equal to or higher than the glass transition point of the resin for a predetermined time, and the temperature is gradually lowered to a temperature equal to or lower than the thermal deformation temperature of the resin. Using a molding method including a cooling step, a molded product having a longitudinal cross-sectional shape having ribs having width dimensions a and b and height dimensions c and d that satisfies the expressions (1) and (2) is formed. By doing
Similarly to the fourth aspect, the effect of the first aspect becomes more effective, and an optical component having high dimensional accuracy and internal uniformity is molded (corresponding to the fifth aspect).

Further, in a mold for molding a plastic molded product, when the mold is filled with resin, a high internal pressure is generated in the cavity of the mold, and the shape of the cavity is elastically deformed to change the wall surface shape of the cavity. Even a plastic molded product having a longitudinal cross-sectional shape having a rib having a width dimension a, b and a height dimension c, d that satisfies the above formulas (1) and (2), has a high precision shape and dimension. Internal uniformity cannot be obtained.

For this reason, the material of the cavity piece of the mold is a steel material having a large longitudinal elasticity E, for example, E = 21000 kg / mm ² , and a width dimension a satisfying the above-mentioned equations (1) and (2). , B and height c, d, plastic molded products having ribs and having a longitudinal cross-sectional shape are less affected by changes in wall shape due to cavity internal pressure, and have high dimensional accuracy and uniform inside. Can be manufactured (corresponding to claim 6).

However, the resin filled in the cavity is heated to a temperature higher than the glass transition temperature Tg. After filling, the resin is gradually cooled in the mold. The distribution is affected by the thermal conductivity of the mold. As the resin temperature in the cavity is constant, a highly accurate molded product can be obtained in a short time. Therefore, when the cavity piece is made of a material having poor thermal conductivity, the molding cycle becomes long. For this reason, the longitudinal elastic modulus E is small (E = 14) where the cavity inner wall deformation due to the resin internal pressure is small as a mold material.
000 kg / mm ² ) and using a copper alloy having excellent thermal conductivity, using a copper alloy cavity piece,
By molding a plastic molded product having a rib having the width dimensions a and b and the height dimensions c and d satisfying the expression (2), the plastic molded article has high dimensional accuracy and internal uniformity. A molded article can be manufactured (corresponding to claim 7).

Each of the ribs 1 of the plastic molded product shown in FIGS. 2 to 4 has a constant width (ab) / 2 and a height (cd) / 2. It is provided behind the front surface 3. For this reason, there is a risk that the rib portion 1 may be deformed due to contact with the mold during release.

FIG. 10 is a view for explaining a molded product in which the rib having the rib shown in FIG. 2 has a tapered shape in the longitudinal cross-sectional shape. (C-d) / 2 in the portion of the dimension c, (ab-) / 2 (b <b ") in the portion of the height (cd), and inwardly inclined (cd). / (Bb ′).

The rib portion 1 of a plastic molded product having a cross section in the longitudinal direction having ribs of width dimensions a and b and height dimensions c and d satisfying the equations (1) and (2) shown in FIG. As shown in FIG. 10, the rib 1b having a taper makes it easy to release the mold, thereby preventing deformation from occurring at the time of release.

[0043]

【The invention's effect】

Effect corresponding to claim 1: Having ribs, high shape accuracy
Regarding the longitudinal cross-sectional shape of the plastic molded product requiring internal uniformity, the ratio b / a of the width dimension a including the rib of the molded product to the width dimension b excluding the rib of the molded product is 0.5 or less, In addition, since the ratio d / c of the height c including the ribs of the molded article including the ribs to the height d excluding the ribs is set to 0.3 or more, the ribs have high shape accuracy and high internal uniformity. A precision molded product is obtained.

According to the second aspect of the present invention, the cross-sectional shape of a plastic molded product that has ribs and requires high shape accuracy and internal uniformity only in a part of the molded product has high shape accuracy and high precision.
Since only the portions requiring internal uniformity have the cross-sectional shape according to claim 1, only the portions requiring high shape accuracy and internal uniformity have the cross-sectional dimensions of claim 1, and the portions requiring no accuracy are ribs. The material b is reduced by increasing the dimension b not including the rib and decreasing the height dimension d not including the rib.

According to a third aspect of the present invention, the cross-sectional shape of a molded article for molding a plastic optical component having a rib and requiring high shape accuracy and internal uniformity such as a lens and a mirror is other than the rib of the molded article. The width dimension b and the height dimension d other than the ribs are the dimensions of the optically effective range of the lens / mirror, and the cross-sectional shape of claim 1 is used. And improve the molding cycle.

According to a fourth aspect of the present invention, a plasticized resin is injected and filled into a cavity of a mold which has been heated to a temperature equal to or higher than the glass transition temperature of the resin, and then a gate seal is performed. The invention of claim 1 becomes more effective by using a high-precision molded product manufacturing method based on a molding method in which is gradually cooled to a temperature not higher than the heat deformation temperature of the resin.

According to a fifth aspect of the present invention, an injection molding step of performing injection molding on a mold maintained at a temperature equal to or lower than the thermal deformation temperature of the resin and performing gate sealing, and maintaining the temperature at or above the glass transition point of the injection molded resin. Raise the temperature of the mold filled with the resin, and hold at a temperature equal to or higher than the glass transition point of the resin for a predetermined time,
Furthermore, by using a high-precision molded product manufacturing method by a molding method comprising a step of gradually cooling the resin to a temperature not higher than the thermal deformation temperature,
The invention of claim 1 becomes more effective.

According to the sixth aspect, the material of the cavity piece of the mold is a steel-based material having a high longitudinal elastic modulus, and the mold is resin-molded in the dimension ratio shape according to the first aspect. By reducing the amount of deformation of the wall surface, a highly accurate molded product can be easily obtained.

Effect corresponding to claim 7: The material of the cavity piece of the mold is a copper alloy having a moderately high elastic modulus and a high thermal conductivity, and this mold has a dimensional ratio shape corresponding to claim 1. Since the resin is molded, the molding cycle is improved.

According to the eighth aspect, since the ribs of the molded product are provided with a taper, deformation at the time of releasing from the mold can be prevented, and a decrease in accuracy can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a change in a longitudinal cross-sectional shape of a molded product having no rib.

FIG. 2 is a first longitudinal direction of a plastic molded product having a width a including a rib, a width b excluding a rib, a height c including a rib, and a height d excluding a rib of the molded product. It is a figure showing a section shape.

FIG. 3 is a view for explaining the quality of molding accuracy when the ribs shown in FIG. 2 are provided and the height and width of the ribs are different.

FIG. 4 is a diagram for explaining the quality of molding accuracy when the ribs shown in FIG. 2 are provided and the heights and widths of the ribs are different.

FIG. 5 is a view showing a second longitudinal cross-sectional shape of the plastic molded product having the rib dimensions shown in FIG. 2;

FIG. 6 is a view showing a third longitudinal cross-sectional shape of the plastic molded product having the rib dimensions shown in FIG. 2;

FIG. 7 is a view showing a fourth longitudinal cross-sectional shape of the plastic molded product having the rib dimensions shown in FIG. 2;

FIG. 8 is a view showing a fifth longitudinal cross-sectional shape of the plastic molded product having the rib dimensions shown in FIG. 2;

9 is a view showing a sixth longitudinal cross-sectional shape of the plastic molded product having the rib dimensions shown in FIG. 2;

FIG. 10 is a view for explaining a molded product having a longitudinal cross-sectional shape having a tapered rib in FIG. 2;

[Explanation of symbols]

 1 ... rib part, 2 ... rectangular part, 3 ... molded product surface part.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-142105 (JP, A) JP-A-5-200793 (JP, A) JP-A-5-111937 (JP, A) JP-A-8-108 294934 (JP, A) JP-A-7-125099 (JP, A) JP-A-4-163119 (JP, A) JP-B 5-73570 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) B29C 45/00-45/84 B29D 11/00 B29L 11:00

Claims (8)

(57) [Claims] 1. With respect to the longitudinal cross-sectional shape of a plastic molded product having a rib and requiring high shape accuracy and internal uniformity, a width dimension a including the rib of the molded product and a rib of the molded product are excluded. The ratio b / a of the width dimension b is 0.5 or less, and the ratio d / c of the height dimension c including the ribs of the molded article and the height dimension d excluding the ribs is 0.3 or more. Plastic molded products characterized by: 2. A cross-sectional shape of a plastic molded product having ribs and requiring high shape accuracy and internal uniformity only in a part of the molded product, only in a portion requiring high shape accuracy and internal uniformity. A plastic molded product characterized by having a cross-sectional shape as described in (1). 3. A cross-sectional shape of a molded product having a rib for molding a plastic optical component such as a lens and a mirror which requires high shape accuracy and internal uniformity, and a width b and a rib other than the rib of the molded product. 2. A plastic molded product characterized in that the height d other than the above is a cross-sectional shape according to claim 1, using a dimension of the optically effective range of the lens / mirror. 4. A plasticized resin is injected and filled into a cavity of a mold which has been heated to a temperature equal to or higher than the glass transition temperature of the resin in advance, and the gate is sealed. The plastic molded article according to claim 1, wherein the plastic molded article is obtained by a molding method of gradually cooling to below. 5. An injection molding step of injection-molding a plasticized resin into a mold held at a temperature equal to or lower than a thermal deformation temperature of the resin to perform gate sealing, and a step of making the temperature higher than the glass transition point of the injection-molded resin. To raise the temperature of the mold filled with the resin,
2. The plastic molded article according to claim 1, wherein the molded article is obtained by a molding method comprising a step of holding the resin at a temperature not lower than the glass transition point of the resin for a predetermined time and further gradually cooling the resin to a temperature not higher than the thermal deformation temperature of the resin. 6. The plastic molded product according to claim 1, wherein the cavity piece of the mold is formed by a mold whose material is a steel-based material. 7. The plastic molded article according to claim 1, wherein the cavity piece of the mold is molded by a mold whose material is a copper alloy. 8. The plastic molded product according to claim 1, wherein a taper is provided in a rib portion of the molded product.