JPH10278077A - Injection molded form and molding method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molded form having a configuration capable of providing a sink mark at a place whereat the sink mark is required and transferring mirror surfaces surely at places whereat the transfer of mirror surfaces is required, in molding the injection molded form by employing an injection molding tool. SOLUTION: An injection molded form 1 is molded by an injection molding tool 10 constituted so as to generate a pressure difference or an air pressure between a mirror surface part, corresponding to the mirror surface of a molding material 20 and a venting port unit, corresponding to the venting port 18 of the same, to generate a sink mark in the venting port part. In such an injection molded form 1, steps 6 are provided between the venting port 18 and the mirror surface parts 2, 3 in the cavity 17 of the injection molding tool 10. Concretely, the steps 6, intercepting between the venting port 18 and the mirror surfaces 2, 3, are provided on a surface 4 at the venting port side of the injection molding molded form 1 whereby the area of sink mark ca be controlled so as to be in the steps and the arrival of sink mark at the mirror surfaces 2, 3 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molded article such as a plastic optical element (lens, mirror, prism, etc.) molded by an injection mold and a molding method thereof.

[0002]

2. Description of the Related Art Conventionally, a molding surface defining a cavity having a predetermined volume, a transfer surface formed on the molding surface and transferring a mirror surface to a molded product, and a gate having a predetermined area opening on the molding surface are provided. 2. Description of the Related Art Injection molding dies are known in which a molten resin is injected and filled into a cavity through a gate and cooled to mold a molded product, for example, a plastic optical element such as a mirror, a lens, or a prism with high precision. High precision mirror surfaces and uniformity of refractive index are required especially for optical elements in molded products molded by this type of injection mold, but surface precision is required due to shrinkage when the molten resin solidifies. There was a problem that sinks occurred on the mirror surface.

As a conventional technique for solving such a problem, for example, Japanese Patent Application Laid-Open No. HEI 3-128218,
JP-A-8-234005, JP-A-3-15121
No. 8 or JP-A-3-281213 discloses an injection mold and a molding method. In this injection molding die and a molding method using the die, the molding surface facing the transfer surface is roughened, injection is stopped immediately before completion of filling of the cavity with the molten resin, and a holding pressure is applied. By cooling and solidifying without cooling, sink marks are generated on the rough surface side due to the difference in adhesion between the molten resin and the transfer surface and the rough surface, thereby preventing sinks from occurring on the mirror surface. Japanese Patent Application Laid-Open No. 3-151218 discloses that: a molding surface facing a transfer surface is roughened, and an overflow portion into which excess molten resin flows is provided outside the cavity, and when filling into the overflow portion is started. An injection mold and a molding method are described, in which injection is stopped, and solidification is performed by cooling without applying a holding pressure, thereby causing sink marks on the rough surface side due to a difference in adhesion between the molten resin and the transfer surface and the rough surface. .

However, in such a conventional example, in order to make the molding surface facing the transfer surface of the mold rough,
An optical element (for example, a mirror) that requires only one mirror surface can be formed, but the position of forming the mirror surface and the number of mirror surfaces are limited, and it is impossible to form an optical element such as a lens or a prism. . In addition, depending on the material constituting the transfer surface and the rough surface and the material of the molten resin, there is a problem that the adhesion force is reversed and sink occurs in the mirror surface.
Also, in the above, it is very difficult to stop the injection immediately before the completion of filling, and if the timing of the stop is shifted, the adhesion of the transfer surface and the rough surface is reversed to cause sink in the mirror surface or insufficient molten resin. Would. Further, in the above, it is possible to extend the time range of the timing of stopping the filling of the molten resin, but it is necessary to remove the overflow portion because the overflow portion is integrally formed with the molded product, In addition to the increase in cost, if the opening area of the gate through which the molten resin flows into the overflow area is too small, the adhesion between the transfer surface and the rough surface will be reversed, causing the mirror surface to sink, and if too large, the molten resin will be insufficient. There was a problem of doing it.

In order to solve such a problem,
The present applicant previously generated sink marks outside the mirror surface of the molded product without strict control of the molding material by generating an air pressure difference between the mirror surface portion of the molding material and a predetermined location,
An injection mold capable of forming a molded product having a highly accurate mirror surface without internal distortion has been provided (Japanese Patent Laid-Open No. 6-304973).

The injection molding die includes a molding surface defining a cavity having a predetermined volume, a transfer surface formed on at least one of the molding surfaces and transferring a mirror surface to a molded product, and a cavity opened in the molding surface. A gate for injection-filling the molten molding material into the mold, and a mold having a pair of molds, wherein the molten molding material is injected and filled in the cavity through the gate, cooled and molded into a molded product. At least one opening with a predetermined area outside the transfer surface of the molding surface
One or more vents, and at least one or more communicating holes communicating with the vents and applying a predetermined air pressure to the molding material are provided, and correspond to the mirror portion corresponding to the mirror surface of the molding material and the vents. It is characterized in that a pressure difference is generated between the air vent and the air vent to cause sink marks. That is, according to this injection molding die, air is brought into contact with the molding material transferred outside the mirror surface by the transfer surface through the air hole and the communication hole to reduce the cooling rate and to apply a predetermined air pressure to the air hole portion. Since a predetermined pressure difference is generated between the mirror surface portion of the molding material and the ventilation hole, sink marks can be selectively generated in the ventilation hole portion, and the mold can be formed without generating sink marks in the mirror surface portion. The transfer surface can be transferred with high precision.
Also, since sink marks are selectively generated in the vent, the control of the filling amount of the molding material into the cavity can be simplified, and the molded article can be molded without generating internal distortion. As a result, a molded article having a highly accurate mirror surface without internal distortion can be easily molded.

Japanese Unexamined Patent Publication No. Hei 6-304973 discloses that in the above-mentioned injection mold, the communication hole is formed so that a predetermined air pressure is applied to the ventilation port of the molding material through the ventilation port. Is formed so as to be connectable to a compression device that feeds in. Thus, by forming the communication hole so as to be connectable to the compression device, the compression device allows a space between the mirror surface portion of the molding material and the vent hole to be formed. An air pressure difference can be arbitrarily generated, and sink marks can be generated in the vent. In addition, the pressure difference can be easily adjusted, and a mirror surface can be formed with higher accuracy without causing internal distortion.

[0008]

FIG. 12 is a sectional view of an essential part showing an example of a conventional injection molding die.
Is a fixed mold, 12 is a movable mold, 13 and 14 are mirror pieces having a transfer surface for transferring a mirror surface to a molded product, 15
Reference numeral 16 denotes a reference surface side nest having a molding surface on the side to be the reference surface (C surface) of the molded product, and 16 denotes a surface nest having a molding surface on the side to be the sink surface (B surface) of the molded product. ,
A cavity 17 having a predetermined volume is defined by the molding surfaces of these mold parts. A molding material (for example, a molten resin) melted through a gate (not shown) in the cavity 17.
20 is injection-filled. In addition, face side nesting 1
The molding surface 6 is provided with a vent 18 opening in a predetermined area and a communication hole 19 communicating with the vent 18 and applying a predetermined air pressure to the molding material 20. FIG. 13 shows an example of the ventilation hole 18 formed on the molding surface (surface B) of the surface side insert 16 to be shrunk. The ventilation from the ventilation port 18 is performed by natural ventilation utilizing a pressure difference between the mirror surface portion and the ventilation port portion, and by connecting a compression device (not shown) to the communication hole 19 and using the compression device to form the mirror surface portion of the molding material. And forced ventilation that arbitrarily generates an air pressure difference between the air pressure and the ventilation port.

Injection mold 1 having the structure shown in FIGS.
0, the vent 18
The sink can be guided to the surface by a method in which air enters the cavity 17 through the ventilation hole 18 through the communication hole 19 (for details, see JP-A-6-30).
No. 4973). In addition, mirror surface piece 1
Mirror surfaces of 3, 14 can be satisfactorily transferred, and an injection molded article having low internal distortion can be obtained. FIGS. 14A and 14B are views showing an example of an injection-molded product formed by the above-mentioned injection mold, wherein FIG. 14A is a perspective view of the injection-molded product, FIG. 14B is a side view of the injection-molded product,
(C) is a sectional view of a part A of the injection molded product. This injection molded product 21 is an example of a rectangular lens molded product in which mirror surfaces (optical surfaces) 22 and 23 are transferred to two surfaces by mirror surface pieces 13 and 14 of the injection molding die 10, and FIG. The side surface shown is the surface (B surface) 24 on the side of the lens molded product 21 on which the sink is desired to be sinker, and the shaded area indicated by reference numeral 27 indicates the sink region. The surface 25 opposite to the B surface 24 is a mounting reference surface (C surface). As shown in FIG.
By inducing the target sink mark on the B surface 24 of 1, it is possible to obtain a lens molded product having a low internal distortion in which the mirror surfaces 22 and 23 are well transferred.

However, the cavity 17 of the injection mold 10 is composed of a plurality of mold parts 11 to 16, and if the part accuracy and the assembling accuracy are poor, as shown in FIG. A gap d is formed, air enters from the gap d, and air flows into the cavity 17, so that the target surface may not be reduced. FIG. 15 is a diagram showing an example of a lens molded product molded in a state where air flows into the reference surface (C surface) side in the cavity 17, (a) is a side view of the lens molded product, b) is a sectional view of a part A of the lens molded product. FIG.
As shown in (1), in the lens molded product 21 molded in a state where air flows into the C surface side in the cavity 17, the sink on the target surface (B surface) side becomes small (or the sink may occur). In the worst case, sinking occurs on the C surface 25 side opposite to the B surface 24, and the surface accuracy as a reference surface is reduced.

In the method of blowing air from the vent 18 (naturally or forcedly), air enters the mirror 17 due to the difference in the amount of resin filled in the cavity 17 and the setting of the amount of air. It can cause you to sink. FIG. 16 is a diagram showing an example of a lens molded product whose sink reaches the mirror surface portion, where (a) is a top view of the lens molded product,
(B) is a side view of the lens molded product, and (c) is a cross-sectional view of a part A of the lens molded product. When air enters the mirror surface during injection molding, and the sink region 27 guided to the surface B reaches the mirror surface 22 side as shown in FIG. Deteriorates.

The present invention has been made in view of the above circumstances, and when molding an injection-molded product using the same injection-molding mold as in the prior application, only a portion to be shrunk is cut off to transfer a mirror surface. It is an object of the present invention to provide an injection-molded product having a shape that can be reliably transferred at a desired location, and a method of molding the injection-molded product.

[0013]

In order to achieve the above-mentioned object, according to the first aspect of the present invention, there is provided a molding surface which defines a cavity having a predetermined volume, and at least one or more molding surfaces formed on the molding surface have mirror surfaces. And a gate having an opening in the molding surface and a gate for injecting and filling a molten molding material into the cavity, and the molding material melted in the cavity is injected and filled through the gate. An injection molding die for cooling and cooling to form a molded product, wherein at least one or more vents opening in a predetermined area outside the transfer surface of the molding surface, and the molding material communicates with the vent. At least one or more communication holes for providing a predetermined air pressure are provided, and a pressure difference is generated between a mirror surface portion corresponding to a mirror surface of the molding material and a ventilation hole portion corresponding to the ventilation hole, and the ventilation hole portion is formed. Specially to cause sink Injection mold and, or,
It is formed so as to be connectable to a compression device that sends air so as to apply a predetermined air pressure to the ventilation port of the molding material through the communication hole and the ventilation port, and corresponds to the mirror surface portion and the ventilation hole with respect to the mirror surface of the molding material. In an injection-molded product molded by an injection molding die characterized by generating air pressure between the vent and the vent, the sink is generated, and between the vent in the cavity and the mirror surface. It is characterized by providing a step.

According to a second aspect of the present invention, in the injection molded product according to the first aspect, a step is provided on a surface on the side of the vent. According to a third aspect of the present invention, there is provided the injection molded article according to the first or second aspect, wherein a step is provided so as to block between the vent and the mirror surface. The invention described in claim 1
Or the injection-molded article according to 2, wherein a step is provided so as to surround the vent.
According to a fifth aspect of the present invention, in the injection molded product according to the first or second aspect, a step having a shape substantially similar to the side surface shape on the side of the vent hole is provided.

According to a sixth aspect of the present invention, in the injection molded article of the first aspect, the step is formed in a convex shape. In the injection-molded article, the step is concave.

According to an eighth aspect of the present invention, in the injection molded article of the first aspect, a step is provided on the mirror surface side. The invention according to claim 9 is
In the injection molded article according to the first or eighth aspect, a step is provided so as to sandwich the surface on the longitudinal side of the mirror surface portion. The invention according to the tenth aspect is the invention according to the first or eighth aspect. In the above injection molded product, a step is provided so as to surround the outer periphery of the mirror surface portion.

According to an eleventh aspect of the present invention, there is provided an injection molded article according to the first aspect, wherein a step having a tapered shape is provided. The injection-molded article is provided with a triangular step, and the invention according to claim 13 is characterized in that an arc-shaped step is provided in the injection-molded article according to claim 1. According to a fourteenth aspect of the present invention, in the injection molded product according to the first aspect, the step is set to 0.1 mm or more.

According to a fifteenth aspect of the present invention, there is provided a molding surface defining a cavity having a predetermined volume, a transfer surface formed at least one or more on the molding surface and transferring a mirror surface to a molded product, and an opening formed in the molding surface. A pair of molds having a gate for injecting and filling the molten molding material into the cavity, and an injection molding mold for injecting and cooling the molten molding material into the cavity via the gate, and cooling to form a molded product. And
Outside the transfer surface of the molding surface, at least one or more air holes that open with a predetermined area, and at least one or more communication holes that communicate with the air holes and apply a predetermined air pressure to the molding material are provided. An injection mold, characterized in that a pressure difference is generated between a mirror surface portion corresponding to a mirror surface of the molding material and a ventilation hole portion corresponding to the ventilation hole to generate sink marks in the ventilation hole portion,
Alternatively, it is formed so as to be connectable to a compression device that feeds air so as to apply a predetermined air pressure to the ventilation port of the molding material through the communication hole and the ventilation port. In a molding method for molding a molded product by an injection molding die, wherein air pressure is generated between a corresponding vent and a vent is generated in the vent, the resin pressure in the cavity is reduced to zero. It is characterized in that the air pressure is generated through the ventilation port for a longer time than it takes. According to a sixteenth aspect of the present invention, in the method for molding an injection-molded article according to the fifteenth aspect, the air pressure is not less than atmospheric pressure (about 0.1 MPa) and not more than 2 MPa.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 17 shows a positional relationship between a conventional injection molded product 21 and a vent. In the case where there is a vent at such a position, as described above, a method of flowing air from the vent 18 of the injection molding die 10 (natural ventilation or forced compression by connecting a compression device through the communication hole 19). Regardless of the ventilation), air enters the mirror surface due to the difference in the amount of resin and the amount of air filled in the cavity, and as shown in FIG. There is a risk of spreading to the 22nd side. In order to eliminate this, in the present invention, the injection-molded article has a shape in which a step is provided between the vent in the cavity and the mirror surface portion (claim 1). Hereinafter, examples of the present invention will be described.

FIG. 1 is a view showing an embodiment of an injection molded product according to the present invention and an injection mold for molding the molded product.
(A) is a perspective view of an injection-molded product, and (b) is a cross-sectional view of a main part of an injection mold. The basic configuration of an injection mold for molding the injection molded product of the present invention is the same as that shown in FIG. 12, and the same components are denoted by the same reference numerals.
In the injection mold 10 shown in (b), the vent 18 in the cavity 17 corresponds to the step 6 provided in the molded product 1.
A step is provided on the molding surface between the mirror surface portion. FIG.
The injection molded product 1 shown in FIG. 1A is a rectangular lens molded product having two mirror surfaces (optical surfaces) 2 and 3 serving as lens surfaces. This is an example in which a step 6 for blocking between the vent 18 and the mirror surfaces 2 and 3 is provided on the surface (surface B) 4 on the vent side of the product 1 on the vent side (claims 2 and 3). Hereinafter, the effect of the step will be described.

FIG. 1B shows an injection molding die 10 for molding a molded product 1 having a shape having a step.
An inverted step for forming the step 6 on the molded product 1 side is provided on the molding surface between the vent 18 in the 7 and the mirror surface portion. Immediately after filling the molten resin 20 as a molding material into the cavity 17 of the mold, the internal pressure of the resin is high, so that it is difficult for the air to exist in the cavity 17 and flows out from the vent 18 to the communication hole 19. When the resin pressure in the mold decreases with cooling and becomes lower than the atmospheric pressure or the compression pressure (when air is compressed and injected through the communication holes 19 and the ventilation holes 18 by the compression device), air flows in from the ventilation holes 18. Then, the resin 20 starts to separate from the mold vent 18 (generation of sink marks). At this time, if there is no step in the molded product, the sink may continue to grow and reach the mirror surface portion. However, as shown in FIG. In the case where a step 6 is provided to block between the vent and the mirror surfaces 2 and 3, the step tends to contract in the direction of the arrow in FIG. However, shrinkage of the step does not progress because it interferes with the step on the mold side. Therefore, the resin and the mold are in close contact with each other, and the sink does not grow beyond the step, and the area of the sink can be controlled within the step. As a result, only the portion that is to be shrunk is shrunk, and the mirror surface 2, 3
Is reliably transferred to the lens molded product 1.

FIG. 2 is a perspective view of an injection-molded product showing another embodiment of the present invention. In this embodiment, a step 6 is arranged on the B side 4 on the side of the vent of the lens molded product 1 having the same shape as that of FIG. 1A so as to surround the periphery of the vent. . By arranging the step 6 so as to surround the periphery of the ventilation hole in this manner, the air does not flow around as compared with FIG. 1A, and the sink region can be more reliably controlled.

Next, FIG. 3 is an explanatory view of an injection-molded product showing another embodiment of the present invention. FIG. 3 (a) is a perspective view of the injection-molded product, and FIG. (C) is a cross-sectional view of the injection-molded product at A2. In this embodiment, FIG.
A molded article 1 having the same lens shape as that of FIG. 1A is provided with a step 6 having a shape substantially similar to the side surface shape on the side surface (B surface) 4 on the side of the vent hole (Claim 5). More specifically, when the molded product 1 is a rectangular lens as shown in FIG. 3, the surface (B surface) 4 on the side of the vent is substantially similar in shape to the side surface of the lens so as to surround the periphery of the vent. Is provided. As a result, the sink area can be controlled at the same ratio as the cross-sectional area of each cross-section of the molded article 1 (eg, cross-sections A1 and A2 shown in FIGS. 3B and 3C). Accuracy of uniformity is achieved, resulting in a more accurate lens molded product.

In each of the above embodiments, the shape of the step 6 of the injection-molded article 1 in the height direction is shown as a convex shape as shown in the sectional view of FIG. (3) Even if a concave step is formed as shown in the cross-sectional view of FIG. However, when a convex step is provided on the surface (B surface) 4 on the vent side of the molded product 1, a concave step is provided on the molding surface around the vent 18 of the injection molding die 10. In the case where a concave step is provided on the surface (B surface) 4 on the vent side of the product 1, the vent 1 of the injection mold 10 is used.
A convex step is provided on the molding surface around 8.

Next, a case where a step is provided on the mirror side of the injection molded product will be described. 5A and 5B are explanatory views of an injection-molded product showing another embodiment of the present invention, in which FIG. 5A is a perspective view of the injection-molded product, and FIG. This is an example in which a step 6 is provided on the mirror surfaces 2 and 3 on the side of the article 1 on which the sink is desired (claim 8). In order to block the inflow of air from the ventilation port, a step 6 may be provided on the mirror surfaces 2 and 3 on the side of the injection-molded product 1 to be recessed as shown in FIG. Since the step 6 and the step on the mold side are in close contact with each other, it is possible to prevent air from entering the mirror surfaces 2 and 3 and prevent sinks from occurring in the mirror surfaces.

FIG. 6 is an explanatory view of an injection-molded product showing another embodiment of the present invention, wherein (a) is a perspective view of the injection-molded product,
(B) is a sectional view of a part A of the injection molded product, and shows an injection molded product 1;
This is an example in which a step 6 is provided in a part of the mirror portions 2 and 3 on the side to be subtracted. As shown in FIG. 16, when it is known that air flows around a part of the mirror surface of the molded article and sinks only in a part of the molded product, there is a possibility that the mirror surfaces 2 and 3 may sink as shown in FIG. A step 6 of only a part provided at a certain location may be used. In this case, since the step is a part, the processing cost for forming the step in the mold can be reduced.

FIG. 7 is an explanatory view of an injection-molded product showing another embodiment of the present invention, wherein (a) is a perspective view of the injection-molded product,
(B) is a sectional view of a part A of the injection molded product, and shows an injection molded product 1;
This is an example in which a step 6 is provided on the B surface 4 side and the C surface 5 side of the mirror surfaces 2 and 3 so as to sandwich the longitudinal surfaces of the mirror surfaces 2 and 3 (claim 9). In the case where the assembling accuracy of the mold 10 is poor as shown in FIG. 12, there is a possibility that air may enter from an unpredictable place, and for example, as shown in FIG.
There is a case where air flows into the (surface) side to cause sink marks. However, the air may flow to the mirror surface portion and sink may occur in the mirror surface portion. Fig. 7
By providing the steps 6 on both sides of the mirror surfaces 2 and 3 as described above, it is possible to prevent air from flowing around to the mirror surfaces and prevent sink marks from occurring on the mirror surfaces.

FIG. 8 is an explanatory view of an injection-molded product showing another embodiment of the present invention, wherein (a) is a perspective view of the injection-molded product,
(B) is a sectional view of a part A of the injection molded product, and shows an injection molded product 1;
This is an example in which a step 6 is provided so as to surround the outer circumferences of the mirror portions 2 and 3 (claim 10). By providing the step 6 so as to surround the outer circumferences of the mirror portions 2 and 3 as described above, it is possible to more reliably prevent air from entering and to surely prevent sinks from occurring in the mirror portions.

In order to prevent air from entering the mirror portions 2 and 3 of the injection-molded article 1, it is only necessary to have a step shape as shown in FIG. 7 (b) and FIG. 8 (b). However, considering the releasability from the mold, as in the embodiment shown in FIG.
Preferably, a step 6 having a tapered draft angle is provided (claim 11), so that the molded product can be released from the mold without deteriorating the shape accuracy.

As shown in FIG. 10 (a), a triangular step 6 is provided on both sides of the mirror portions 2 and 3 of the injection molded product 1.
(Claim 12) or by providing arc-shaped steps 6 on both sides of the mirror surfaces 2 and 3 of the injection-molded article 1 as in the embodiment shown in FIG. In addition to the improvement of the moldability, the processing for forming the steps on the mold side such as the mirror pieces 13 and 14 can be simplified.

The height h of the step 6 provided in the injection-molded article 1 is h = 0.1 mm or more. That is, the present inventors have experimentally confirmed that a sufficient air blocking effect can be obtained when the height of the step is 0.1 mm or more.

Next, a method for molding an injection-molded article according to the present invention will be described with reference to an example using an injection mold having the structure shown in FIG. First, with respect to the fixed mold 11 on which the mirror piece 13 and the face side nest 16 to be shrunk are mounted, the mirror piece 1
The cavity 4 having a predetermined volume is defined by the molding surfaces of the pair of dies by bringing the mold 4 into close contact with the movable-side mold 12 on which the nest 15 is mounted. The cavity 1 is formed on a molding surface (not shown) of the injection mold 10.
7 is provided with a gate communicating with the outside to inject the molten molding material into the cavity, and a known injection filling machine (not shown) is connected to the gate. Is injected and filled. Immediately after filling the molten resin 20 as a molding material into the cavity 17 of the mold 10, since the resin internal pressure is high,
Air is difficult to exist in the cavity 17 and flows out of the vent 18. When the resin pressure in the mold decreases with cooling of the molten resin 20 and becomes equal to or lower than the atmospheric pressure or the compression pressure (when air is compressed and injected through the communication hole 19 and the ventilation port 18 by a compression device (not shown)), Numeral 20 begins to separate from the mold vent 18, and air flows in through the vent 18 (generation of sink marks). At this time, for example, as shown in FIG. 1A, in a shape in which a step 6 is provided on the surface (B surface) 4 on the vent side of the molded product 1 so as to block between the mirror surfaces 2 and 3, The step portion shrinks, for example, in the direction of the arrow in FIG. 1B, but does not shrink in the step portion because it interferes with the step on the mold side. Therefore, the resin and the mold adhere to each other, the sink does not grow beyond the step, and a molded article in which the sink region is controlled to be within the step can be formed.

FIG. 11 is a diagram showing the internal pressure of the resin in the cavity from the start of the filling of the molten resin to the completion of the cooling, and the timing of switching the air pressure when the compressed air is injected from the vent 18. In the molding method of the present invention, when the compressed air is injected from the vent 18, as shown in FIG. 11, the air continues to flow until the internal pressure of the resin in the cavity 17 becomes zero or more, and the air pressure is applied to the vent. (Claim 15). The present inventors have set the ventilation port 1 longer for a longer time than when the resin pressure in the cavity 17 becomes zero.
It has been experimentally confirmed that the generation of the air pressure via 8 can reliably control the sink area.

Since the resin is in close contact with the mold until the internal pressure of the resin in the cavity becomes zero, and the sink grows over a longer period of time, it is necessary to apply air pressure slightly longer than when the internal pressure is zero. This is necessary. For example, in the case of the lens shape of the injection-molded article 1 as shown in the embodiment, the sink area can be controlled by applying air pressure for 5 seconds or more after the resin internal pressure becomes zero. Sufficient control can be obtained when the air pressure at that time is not less than the atmospheric pressure (about 0.1 MPa) and not more than 2 MPa.

In the embodiment described above, an example is shown in which a rectangular lens (having two mirror surfaces (optical surfaces)) is used as the injection molded product 1, but the present invention is not limited to this. Instead, a mirror having one mirror surface (optical surface) such as a mirror, or a mirror having a plurality of mirror surfaces (optical surfaces) such as a prism can be dealt with by providing a similar concept and a step having a shape.

[0037]

As described above, according to the first aspect of the present invention, a pressure difference or an air pressure is generated between the mirror surface portion corresponding to the mirror surface of the molding material and the ventilation port corresponding to the ventilation port. In an injection-molded product formed by an injection mold having a configuration in which a sink is generated in a vent portion, a step is provided between a vent in a cavity and a mirror portion, so that the resin shrinks when the resin is cooled. The resin does not progress from the portion, and the adhesion between the resin and the mold in the portion other than the surface to be recessed is maintained, the sink region does not grow beyond the step, and the sink region can be controlled within the step.

According to the second aspect of the present invention, the injection molded article
By providing the step on the surface on the vent side, the sink region can be controlled within the surface on the vent side. According to the third aspect of the present invention, since the step is provided so as to block between the vent hole and the mirror surface portion, it is possible to prevent sink marks from reaching the mirror surface. In the invention according to claim 4, by providing a step so as to surround the vent, it is possible to prevent air from flowing into the mirror surface portion, and to control the sink area within the step on the side of the vent.
It is possible to reliably prevent sink marks from reaching the mirror surface. Claim 5
In the invention described, by providing a step having a shape substantially similar to the side surface shape on the side of the ventilation port, the sink region can be controlled at the same ratio as the cross-sectional area of the molded product. Thus, a more accurate molded product can be obtained.

In the sixth aspect of the present invention, the step of the injection molded article has a convex shape, and in the seventh aspect of the present invention, the step has a concave shape. In any case, the effect of controlling the sink area can be obtained. .

According to the eighth aspect of the present invention, by providing a step on the mirror surface side of the injection molded product, it is possible to block the entry of air from the ventilation port to the mirror surface portion, and to prevent the occurrence of sink marks on the mirror surface portion. it can. According to the ninth aspect of the present invention, the step is provided so as to sandwich the surface on the longitudinal side of the mirror surface portion, so that the air from the vent hole and the air circulating from other places can be prevented from entering the mirror surface portion. In addition, the occurrence of sink marks in the mirror surface can be reliably prevented. According to the tenth aspect of the present invention, the step is provided so as to surround the outer periphery of the mirror surface portion, so that air can be more reliably prevented from entering the mirror surface portion, and the occurrence of sink marks on the mirror surface portion can be reduced. It can be reliably prevented.

According to the eleventh aspect of the present invention, by providing a tapered step in the injection molded product, the area of the sink can be controlled within the step, and the shape accuracy of the molded product is not deteriorated. The releasability from the mold can be improved. Further, by providing a triangular or arc-shaped step in the injection-molded article as in the invention according to the twelfth and thirteenth aspects, it is possible to improve not only the releasability but also the processing at the time of forming the step on the mold side. Can be simplified. Incidentally, as in the invention according to claim 14, if the step is 0.1 mm or more, a sufficient air blocking effect can be obtained.

According to the fifteenth aspect of the present invention, a pressure difference or air pressure is generated between the mirror surface portion corresponding to the mirror surface of the molding material and the ventilation hole corresponding to the ventilation hole, and the sink is generated in the ventilation hole. When molding an injection-molded product with an injection molding die having the above configuration, it is possible to reliably control the sink area by generating air pressure through the ventilation port for a longer time than when the resin pressure in the cavity becomes zero. Can be. Also,
When the air pressure is equal to or higher than the atmospheric pressure (about 0.1 MPa) and equal to or lower than 2 MPa, the sink region can be sufficiently controlled.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of an injection molded product according to the present invention and an injection molding die for molding the molded product, (a) is a perspective view of the injection molded product, and (b) is an injection molding die. It is principal part sectional drawing of.

FIG. 2 is a perspective view of an injection-molded product showing another embodiment of the present invention.

3A and 3B are explanatory views of an injection-molded product showing another embodiment of the present invention, wherein FIG. 3A is a perspective view of the injection-molded product, FIG. FIG. 3 is a cross-sectional view of an injection-molded product at A2.

FIG. 4 is a diagram showing an example of a shape of an injection-molded product according to the present invention in a height direction of a step.

FIGS. 5A and 5B are explanatory views of an injection-molded product showing another embodiment of the present invention, wherein FIG. 5A is a perspective view of the injection-molded product, and FIG.

FIGS. 6A and 6B are explanatory views of an injection-molded product showing another embodiment of the present invention, wherein FIG. 6A is a perspective view of the injection-molded product, and FIG.

7A and 7B are explanatory views of an injection molded product showing another embodiment of the present invention, wherein FIG. 7A is a perspective view of the injection molded product, and FIG.

FIGS. 8A and 8B are explanatory views of an injection-molded product showing another embodiment of the present invention, wherein FIG. 8A is a perspective view of the injection-molded product, and FIG.

FIG. 9 is a view showing another embodiment of the present invention, and is a cross-sectional view of an injection-molded article provided with a tapered step.

FIG. 10 is a view showing another embodiment of the present invention,
(A) is a cross-sectional view of an injection molded product provided with a triangular step,
(B) is a cross-sectional view of an injection-molded product provided with an arc-shaped step.

FIG. 11 is a diagram showing the internal pressure of the resin in the cavity from the start of filling of the molten resin to the completion of cooling, and the air pressure switching timing when compressed air is injected from the vent.

FIG. 12 is a sectional view of a main part showing an example of a conventional injection molding die.

FIG. 13 is a plan view showing an example of a ventilation hole formed in a molding surface of a surface side nest to be sink in the injection molding die shown in FIG.

14A and 14B are diagrams illustrating an example of an injection molded product molded by the injection molding die illustrated in FIG. 12, wherein FIG. 14A is a perspective view of the injection molded product, FIG. 14B is a side view of the injection molded product, (c) is a sectional view of a part A of the injection molded product.

15A and 15B are diagrams illustrating an example of an injection-molded product molded in a state where air flows into a reference surface side in a cavity, wherein FIG. 15A is a side view of the injection-molded product, and FIG. It is A section sectional drawing of a molded article.

FIGS. 16A and 16B are diagrams showing an example of an injection-molded product in which sink marks have reached the mirror surface portion, wherein FIG. 16A is a top view of the injection-molded product, FIG. 16B is a side view of the injection-molded product, and FIG. It is A section sectional drawing of a product.

FIG. 17 is a diagram showing a positional relationship between an injection molded product molded by the injection molding die shown in FIG. 12 and a vent.

[Explanation of symbols]

 1: Injection molded product (lens molded product) 2, 3: Mirror surface (optical surface) 4: Surface on vent side (surface to be shrunk (B surface)) 5: Reference mounting surface (C surface) 6: Step 10: Injection molding mold 11: Fixed mold 12: Movable mold 13, 14: Mirror surface piece 15: Reference surface side insert 16: Surface side insert to be shrunk 17: Cavity 18: Vent hole 19: Communication hole 20: Molding material (Molten resin)

Claims (16)

[Claims] 1. A molding surface defining a cavity having a predetermined volume, a transfer surface formed on at least one of the molding surfaces and transferring a mirror surface to a molded product, and a molding opening in the molding surface and being melted in the cavity. And a gate for injection-filling the material, comprising a pair of molds, wherein the molding material melted in the cavity is injection-filled via the gate, cooled, and molded to form a molded product, wherein the molding is performed. Outside the transfer surface of the surface, at least one or more vents opening in a predetermined area, and at least one or more communication holes communicating with the vents and applying a predetermined air pressure to the molding material are provided; An injection mold or a communication hole, wherein a pressure difference is generated between a mirror surface portion corresponding to a mirror surface of a material and a ventilation hole portion corresponding to a ventilation hole to generate sink marks in the ventilation hole portion. And through the vent It is formed so as to be connectable to a compression device that feeds air so as to apply air pressure to the vent of the molding material, and generates air pressure between a mirror surface portion with respect to a mirror surface of the molding material and a vent corresponding to the vent. An injection-molded product formed by an injection molding die characterized by generating sink marks in the vent, wherein a step is provided between the vent in the cavity and the mirror surface. Goods. 2. The injection-molded article according to claim 1, wherein a step is provided on the surface on the side of the ventilation port. 3. The injection-molded article according to claim 1, wherein a step is provided so as to block between the vent and the mirror surface. 4. An injection molded article according to claim 1, wherein a step is provided so as to surround said vent. 5. An injection-molded article according to claim 1, wherein a step having a shape substantially similar to the side surface shape on the side of the ventilation port is provided. 6. The injection-molded article according to claim 1, wherein said step is made convex. 7. The injection-molded article according to claim 1, wherein said step is concave. 8. The injection-molded article according to claim 1, wherein a step is provided on the mirror surface side. 9. The injection-molded article according to claim 1, wherein a step is provided so as to sandwich a surface on a longitudinal side of the mirror surface portion. 10. The injection-molded article according to claim 1, wherein a step is provided so as to surround an outer periphery of said mirror surface portion. 11. The injection-molded article according to claim 1, wherein a step having a tapered shape is provided. 12. The injection-molded article according to claim 1, wherein a triangular step is provided. 13. The injection-molded article according to claim 1, wherein an arc-shaped step is provided. 14. An injection-molded article according to claim 1, wherein said step is 0.1 mm or more. 15. A molding surface defining a cavity having a predetermined volume, a transfer surface formed on at least one of the molding surfaces and transferring a mirror surface to a molded product, and a molding opening in the molding surface and being melted in the cavity. And a gate for injecting and filling a material, comprising: a mold having a pair of molds, wherein the molding material melted in the cavity is injected and cooled through a gate, and is cooled to form a molded product. Outside the transfer surface of the surface, at least one or more vents opening in a predetermined area, and at least one or more communication holes communicating with the vents and applying a predetermined air pressure to the molding material are provided; An injection mold or a communication hole, wherein a pressure difference is generated between a mirror surface portion corresponding to a mirror surface of a material and a ventilation hole portion corresponding to a ventilation hole to generate sink marks in the ventilation hole portion. And through the vent It is formed so as to be connectable to a compression device that sends air so as to apply air pressure to the vent of the molding material, and generates air pressure between a mirror surface portion with respect to a mirror surface of the molding material and a vent corresponding to the vent. In a molding method for molding a molded product by using an injection mold, wherein a sink is generated in the vent, the air pressure is increased through the vent for a longer time than when the resin pressure in the cavity becomes zero. A method for molding an injection-molded article, characterized in that the method comprises: 16. The method according to claim 15, wherein the air pressure is not less than atmospheric pressure (about 0.1 MPa) and not more than 2 MPa.