JPH08187793A - Plastic optical member and production thereof - Google Patents

Abstract

PURPOSE: To produce a plastic optical member inexpensively with high accuracy. CONSTITUTION: A core lens element 1 is molded from a synthetic resin and used as an insert to mold resin films 2, 3 composed of the same material quality on the upper and rear surfaces of the core lens element 1. A convex lens part 10 and an outer flange part 11 are provided to the core lens element 1 and the resin films are molded in such a state that the core lens element 1 is suspended by bringing support pins into contact with the outer flange part 11. By this structure, since wall thickness at the time of molding becomes thin, the internal stress of the resin films is reduced and the generation of strain, warpage and internal bubbles is suppressed and a highly accurate refraction surface can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic optical member and a manufacturing method thereof, and more particularly to a technique suitable for forming a plastic lens using a synthetic resin with high precision.

[0002]

2. Description of the Related Art Conventionally, the number of cases in which an optical member made of plastic, that is, a lens, a prism, etc., is manufactured by injection molding has been increasing due to its advantages such as ease of processing and light weight. Injection molding is performed by injecting the plasticized resin in the molding machine cylinder into the mold and applying a predetermined holding pressure to remove heat from the inner surface of the cavity to cool and solidify the resin and open the mold. This is carried out by the usual means of taking out the molded product.

[0003]

The above-mentioned injection-molded plastic optical member has advantages that it can be easily molded into an arbitrary shape, the manufacturing time is short, and it is suitable for mass production. However, on the other hand, if it is attempted to improve the shape accuracy of the molded product to a certain extent or more, fine correction of the cavity shape of the mold is required, which increases the manufacturing cost and this correction is difficult in processing and work. Therefore, there is a problem in that the optical dimensions of the optical member, for example, the refraction surface cannot be sufficiently highly accurate because it is extremely unrealizable. This is because the shrinkage of the resin when it cures in the cavity causes sink marks and warpage in the molded product.

In recent years, in particular, the demand for producing large or thick optical parts by the resin molding has increased, but as the thickness of the molded product increases, the resin surface portion which is cured first and the resin surface portion are cured later. There is a problem that stress due to curing shrinkage occurs between the inside of the resin, vacuum bubbles (voids) occur inside the resin, and internal stress remains in the molded product. Further, for such a thick optical member, there is also a problem that the cooling cycle in the mold is drastically lengthened due to the increase of the thickness, so that the molding cycle is significantly increased.

Therefore, the present invention is to solve the above-mentioned problems, and the problem thereof is the structure of an optical member which can be molded with high accuracy and speed and at low cost even if the optical member has a large thickness. , And to establish a manufacturing method thereof.

[0006]

In order to solve the above-mentioned problems, a plastic optical member of the present invention has a core member made of synthetic resin housed therein, and at least in the thickness direction of the core member. It is formed by covering with a synthetic resin of the same material.

In this case, the shape of the core member is
At least in an optically effective range, it is preferable to make the shape similar to that of the optical member coated with the synthetic resin.

Further, it is preferable that the thickness of the core member and the thickness of the synthetic resin coating the core member are substantially the same.

Further, it is desirable that the thickness of the synthetic resin coating the core member is thinner than the thickness of the core member.

Further, it is preferable that the core member and the synthetic resin layer are formed so as to mesh with each other.

It is preferable that the synthetic resin layers coated on the front and back of the core member are formed in a mutually connected state.

As a method of manufacturing a plastic optical member, after a core member made of synthetic resin is formed, the core member is introduced into a cavity of a mold, and a synthetic resin of the same material as the core member is introduced into the cavity. It is injected to cover the core member with the synthetic resin.

In this case, a support member for supporting the core member in the cavity is provided in the mold so as to be retractable, and the synthetic resin is injected while the core member is supported by the support member. It is preferable that the support member be retracted from the cavity after the injection of the synthetic resin and before the curing of the synthetic resin.

[0014]

According to the present invention, by covering the core member in its thickness direction with the synthetic resin of the same material, the wall thickness at the time of molding becomes thinner than before, and internal stress and strain at the time of molding occur. Since the risk of deformation such as warpage and warp, formation of internal bubbles, etc. is reduced, a highly accurate plastic optical member can be obtained, and the cooling time at the time of molding is shortened, so that the molding cycle can be shortened. .

According to the second aspect, by making the shape of the core member similar to that of the optical member within the optically effective range, the thickness of the synthetic resin layer to be coated becomes substantially uniform. The risk of generation of internal stress, deformation such as distortion and warpage, formation of internal bubbles, etc. can be further reduced, and a highly accurate optical surface can be obtained.

According to the third aspect of the present invention, the thickness of the core member and the thickness of the synthetic resin coating the core member are made substantially equal to each other, whereby the thickness of the core member can be reduced in both the molding process and the synthetic resin coating process. Therefore, the total cooling time at the time of molding can be minimized, and efficient manufacturing can be achieved.

According to the present invention, by making the thickness of the synthetic resin covering the core member smaller than that of the core member, the molding time of the core member is somewhat increased, but the synthetic resin layer covering the core member is thin. The transferability of the mold is improved and an extremely accurate optical member can be manufactured.

According to the fifth aspect, by forming the core member and the synthetic resin layer so as to mesh with each other, it is possible to prevent the synthetic resin layer from peeling off at the time of mold release or upon receiving heat or impact. .

According to the sixth aspect, by molding the synthetic resin layers formed on the front and back surfaces of the core member so as to be connected to each other, the synthetic resin layers at the time of mold release or when subjected to heat or impact are formed. Peeling can be prevented.

According to the seventh aspect, by covering the core member in its thickness direction with the synthetic resin of the same material, the wall thickness at the time of molding becomes thinner than before, and the generation of internal stress and strain at the time of molding. Since the risk of deformation such as warpage and warp, formation of internal bubbles, etc. is reduced, a highly accurate plastic optical member can be obtained, and the cooling time at the time of molding is shortened, so that the molding cycle can be shortened. .

According to the present invention, a support member for supporting the core member is provided so as to be retractable, and the support member is retracted from the inside of the cavity after the injection of the resin. Can be manufactured, and it is not necessary to previously provide a portion for supporting the optical member.

[0022]

Embodiments of the plastic optical member according to the present invention will now be described with reference to the drawings. Although a plurality of examples described below are configured by taking a convex lens or a concave lens as an example, the present invention is not limited to the above lens,
It can be widely applied to various optical members such as various lenses such as a convex meniscus lens, a concave meniscus lens, a cylindrical lens, an fθ lens and a Fresnel lens, a prism and a grating.

[First Embodiment] FIG. 1 shows a first embodiment according to the present invention.
It shows a convex lens formed as. In this convex lens, the core lens body 1 is formed by injection molding with a methacrylic resin such as PMMA, a transparent resin such as polycarbonate or polystyrene. The core lens body 1 has a convex lens portion 1 having spherical surfaces on the front and back formed in the central portion.
0, and a flat plate-like outer collar portion 11 formed around the convex lens portion 10 are provided.

Next, the core lens body 1 is housed in a mold of an injection molding machine, the core lens body 1 is used as an insert, and insert molding is performed using the same resin as the core lens body 1 resin. Resin coatings 2 and 3 are formed on the front and back surfaces of the core lens body 1. The resin coatings 2 and 3 are similarly provided with convex lens portions 20 and 30 each formed of a spherical surface and flat outer flange portions 21 and 31. The convex lens portions 10, 20, 30 form an integral convex lens shape and have an optically effective diameter OP.

In this embodiment thus formed,
Two-step resin molding by presetting the maximum value d1 of the thickness of the core lens body 1, the maximum value d2 of the thickness of the resin film 2, and the maximum value d3 of the thickness of the resin film 3, that is, the core lens body It is manufactured by the molding process of No. 1 and the molding process of the resin coatings 2 and 3 using the core lens body 1 as an insert.

In the molding process of the core lens body 1, the thickness D = d1 + d2 when the entire convex lens is molded in one step
Since the thickness is as thin as d1 as compared with + d3, generation of internal stress at the time of molding is suppressed, and the cooling time of the resin is significantly shortened. Further, in this step, the surface D1 of the convex lens portion 10 of the core lens body 1 may be formed into a convex surface that is substantially along the refracting surfaces D2 and D3 of the finally formed convex lens. No. 1 requires no precision and can be easily molded.

In the step of molding the resin coatings 2 and 3, the refracting surfaces D2 and D formed by the surfaces of the resin coatings 2 and 3 are formed.
Although the accuracy of 3 is required, the molding of the resin coatings 2 and 3 is almost the same on the entire surface because the surface D1 of the core lens body 1 is formed in a similar shape along the refracting surfaces D2 and D3. Since they are formed to have the same thickness, there is almost no change in thickness, so the transferability of the cavity is improved, and the dimensional and shape accuracy is improved.

In the latter molding step, in order to simultaneously form a resin film on the front and back surfaces of the core lens body 1, the core lens body 1 is supported in a suspended state in the cavity for resin molding. At this time, usually, a plurality of support pins projecting into the cavity come into contact with and support the surface of the outer flange portion 11 of the core lens body 1.

Here, the molding step of the core lens body 1 and
Even if you add the time with the molding process of resin coatings 2 and 3,
The process time is considerably shortened as compared with the case of molding in a single process. Further, when the molding is performed by the above-mentioned two steps, the molding thickness of one time can be reduced, so that the internal stress caused by the curing shrinkage of the resin can be significantly reduced, and the problem of internal bubbles and internal stress Almost no residue occurs.

[Second Embodiment] Next, a second embodiment according to the present invention.
Will be explained. In this embodiment, the outer collar portion 1 of the core lens body 1 is
Recesses 12 and 13 are formed in three places on the front and back sides of 1, and resin coatings 2 and 3 are formed on the recesses 12 and 13. The outer flanges 21 and 31 of the resin coatings 2 and 3 have the above-mentioned recesses 12 and 1, respectively.
The convex portions 22 and 32 are formed in correspondence with No. 3. The other parts are the same as those in the first embodiment, and the same parts are denoted by the same reference numerals and the description thereof is omitted.

The bases of the recesses 12 and 13 are narrower than the tips, and undercut portions are formed when the resin coatings 2 and 3 are molded. With this shape, the core lens body 1 and the resin coatings 2 and 3 are formed so as to mesh with each other, so that the adhesion force between them is enhanced. Therefore, in the subsequent molding step of molding the resin film, the resin films 2 and 3 are prevented from peeling off from the core lens body 1 at the time of releasing the core film, and the core lens body is not affected by heat or impact after manufacturing. 1 and the resin coatings 2 and 3 are not separated.

[Third Embodiment] FIG. 3 shows a third embodiment according to the present invention.
Is shown. In the third embodiment, the through holes 14 are formed at three locations on the outer flange portion 11 of the core lens body 1, and the resin coatings 2 and 3 are formed on the through holes 14 in the subsequent molding process.
To communicate through. By connecting the resin coatings 2 and 3 to each other, it is possible to prevent the resin coatings 2 and 3 from peeling off from the core lens body 1 at the time of mold release, and also to prevent peeling due to heat or impact after manufacturing. To be done.

[Fourth Embodiment] FIG. 4 shows a fourth embodiment of the present invention, in which the core lens body 4 is not provided with an outer flange portion, and the entire surface thereof is covered with a resin film 5. In this embodiment, since the outer peripheral edge of the core lens body 4 is covered with the peripheral edge portion 5a of the resin coating 5, the risk of the resin coating 5 peeling from the core lens body 4 can be completely eliminated. Further, since the core lens body 4 is not provided with an outer flange portion and the entire outer peripheral edge is covered, there is no need to secure the accuracy of the outer diameter dimension of the core lens body 4, and the core lens body 4 can be easily molded. it can.

In this case, at the time of insert molding, by bringing the support pin into contact with the outside of the range of the optically effective diameter OP, molding can be performed without affecting the refracting surface. Here, an outer collar portion is partially provided on the outer peripheral edge of the core lens body 4,
The resin film may not be formed on the surface of the outer flange portion, and the resin films on the front and back sides may be formed to be connected only to the portion without the outer flange portion. Further, according to the mold structure described later, even if the support pin is brought into contact with the support within the range of the optically effective diameter OP, it can be manufactured without affecting the refracting surface.

[Fifth Embodiment] FIG. 5 shows the shape of a fifth embodiment according to the present invention. In this embodiment, an outer flange portion 61 is formed on the core lens body 6, and the resin film 7 completely covers the surface including the outer flange portion 61. A support pin is brought into contact with the outer flange portion 61 of the core lens body 6, and the resin film 7 is formed by the support of the support pin.

In each of the above embodiments, the thickness of the core lens body and the resin coating are substantially the same (d in Embodiment 1).
1 = ~ d2 = ~ d3), the thickness at the time of molding can be minimized, the internal stress, the overall strain and the amount of warp can be reduced, and the cooling time at the time of molding can be minimized. The molding cycle can be shortened.

[Sixth Embodiment] FIG. 6 shows a sixth embodiment according to the present invention.
It shows the structure of. In this embodiment, the core lens body 8
Is formed thick enough to be slightly smaller than the final thickness of the convex lens, and the resin film 9 is thinly formed on the core lens body 8. In this embodiment, the relationship between the maximum thickness d8 of the core lens body 8 and the thickness d9 of the resin coating 9 is d8 >> d9. Therefore, the curing shrinkage amount of the resin coating 9 is extremely small. The shape transfer property is remarkably improved, and a highly accurate refracting surface can be obtained. Further, in this embodiment, since the thickness of the resin film 9 is inevitably almost uniform, the molding quality can be further improved easily.

In this case, on the contrary, the core lens body 8 has a thickness d
9 increases, the cooling time at the time of molding increases and the shape accuracy decreases. However, the core lens body 8 does not require shape accuracy, and if only the molding quality is taken into consideration, the quality of the final product will be better than that of the above embodiment. If the molding time becomes long enough to cause a problem, it is possible to shorten the molding time by forming the core lens body 8 in a plurality of molding steps as in the above-described embodiments.

In Examples 1 to 6 described above, for example, when it is desired to form the refracting surface of the convex lens of the final product to be an aspherical surface, the convex surface of the core lens body is a spherical surface and only the surface of the resin film is an aspherical surface. As a result, the core lens body can be easily manufactured at low cost without degrading the quality of the final product. However, by making the convex surface of the core lens body to have substantially the same shape as the surface of the resin coating, the dimensional accuracy can be further improved. In particular, in Example 6, the thickness of the resin coating 9 is extremely thin. It is desirable that the shape of the lens body 8 be similar to that of the final product, at least within the range of the optically effective diameter, in order to improve the surface accuracy of the final refracting surface.

[Seventh Embodiment] FIG. 7 shows a seventh embodiment according to the present invention.
The core lens body 15 having the concave surface 15a and the resin film 1 having the concave surface 16a are shown in FIG.
6 and. This embodiment is the same as the above-mentioned fourth embodiment except that it is a concave lens.

Next, in order to explain the method of manufacturing the plastic lens shown in each of the above embodiments, an example of the structure of the molding die in the subsequent molding step of insert molding the core lens body as an insert will be described. As shown in FIG. 8, a fixed die plate 102 is attached to a fixed die plate 101 of the molding machine, and a fixed core 103 is fixed in the fixed die plate 102. A mounting plate 104 and a driving plate 105 are slidably housed in the fixed core 103 in a mold opening direction, and the mounting plate 104 and the driving plate 105 sandwich a plurality of support pins 107 and pressure receiving pins 108 therebetween. They are fixed to each other in the state of Drive plate 105 and fixed die plate 1
The elastic spring 106 is held between 01 and 01 in a compressed state.

A movable die plate 202 is attached to the movable die plate 201, and a movable core 203 is fixed inside the movable die plate 202. Movable core 203
A mounting plate 204 and a drive plate 205 are slidably housed inside the mold, and a plurality of support pins 207 and pressure receiving pins 208 are provided between the mounting plate 204 and the drive plate 205.
Are clamped to each other and fixed to each other. Drive plate 20
5 between the movable die plate 201 and the movable die plate 20.
6 is held in a compressed state. Movable die plate 2
A projecting rod 209 is formed so as to be retractable through a through hole provided at 01, and the tip of the projecting rod 209 is arranged so as to be able to press the drive plate 205.

Resin supplied from an injection nozzle (not shown) is introduced from the gate 303 through the introduction holes 301 and 302,
It is injected into the cavity 304 formed by the contact surfaces of the fixed core 103 and the movable core 203. Introduction hole 30
The pressure receiving surface formed at the tip of the pressure receiving pins 108 and 208 faces 1. Usually, the elastic springs 106, 20
By the elastic force of 6, the support pin 10 is inserted in the cavity 304.
When the core lens body 6, which is an insert, is introduced into a state where it is supported by the support pin 107 and mold closing is performed, as shown in FIG. The position of the support pin 107 is held by the elastic coefficient, and the elastic spring 206 having an elastic coefficient smaller than that of the elastic spring 106 is slightly compressed and the support pin 207 is retracted to some extent. In this way, the core lens body 6 is sandwiched by the support pins 107 and 207 by the elastic force.

When the resin is introduced from the introduction hole 301 in this state, as shown in FIG. 9, the resin is injected from the gate 303 into the cavity 304 to fill the periphery of the core lens body 6, and The pressure receiving surface facing the introduction hole 301 is pressed by the injection pressure, so that the pressure receiving pin 1
The support pins 107 and 207 retreat from the inside of the cavity 304 because the drive plates 105 and 205 retreat against the elasticity of the elastic springs 106 and 206 by retracting the drive plates 08 and 208. In this way, the resin is cured in the cavity 304 with the core lens body 6 floating in the center, and a convex lens as in the fifth embodiment is formed.

Generally, the resin injection pressure is the cavity 304.
Since the temperature rises as the resin is injected into the inside, the pressure receiving areas of the pressure receiving pins 108 and 208 and the maximum pressure of the resin are set so that the support pins retract when almost all of the periphery of the core lens body 6 is filled with the resin. , And the elastic coefficients of the elastic springs 106 and 206 are mutually considered and designed.

Finally, when the resin in the cavity 304 is cured, the fixed side mold plate 102 and the movable side mold plate 202 are opened, and the projecting rod 209 projects the drive plate 205 to form the support pin and the pressure receiving pin. Stick out.
Here, the protrusion of the molded product may be performed by a drive plate and a protrusion pin which are separately provided.

As described above, since the support pin automatically projects and retracts due to the resin pressure, the entire periphery can be covered without leaving the tip shape of the support pin in the molded product. However, as shown in the above-mentioned embodiment, the support pin is usually arranged so as to abut the outer flange portion of the core lens body, so that the support pin may be molded in the protruding state without protruding and retracting. Absent. When the support pin is brought into contact with a flat plate-like portion such as the outer flange portion as described above, the tip end surface of the support pin may be a flat surface, but like the convex portion, it is brought into contact with the curved surface of the core lens body. In this case, it is desirable to form the tip end surface of the support pin into a curved surface. In particular, by forming a front end surface that matches the outer surface of the molded product, the front end surface of the retracted support pin can be configured to be continuous with the inner surface of the cavity 304. Even if the portion is not provided, it can be molded so that the trace of the support pin is hardly left.

[0048]

As described above, the present invention has the following effects. According to claim 1, since the core member is covered with the synthetic resin of the same material in its thickness direction, the wall thickness at the time of molding becomes thinner than before, and the generation of internal stress at the time of molding, distortion, warpage, etc. Since it is possible to obtain a plastic optical member with high precision because the risk of deformation, formation of internal bubbles and the like can be reduced, the cooling time at the time of molding can be shortened, so that the molding cycle can be shortened.

According to the second aspect, by making the shape of the core member similar to that of the optical member within the optically effective range, the thickness of the synthetic resin layer to be coated becomes substantially uniform. The risk of generation of internal stress, deformation such as distortion and warpage, formation of internal bubbles, etc. can be further reduced, and a highly accurate optical surface can be obtained.

According to the third aspect, by making the thickness of the core member substantially equal to the thickness of the synthetic resin coating the core member, it is possible to reduce the wall thickness in both the molding process of the core member and the synthetic resin coating process. Therefore, the total cooling time at the time of molding can be minimized, and efficient manufacturing can be achieved.

According to the fourth aspect, by making the thickness of the synthetic resin covering the core member smaller than the thickness of the core member, the molding time of the core member becomes somewhat longer, but the synthetic resin layer covering the core member is thin. The transferability of the mold is improved and an extremely accurate optical member can be manufactured.

According to the fifth aspect, by forming the core member and the synthetic resin layer so as to mesh with each other, it is possible to prevent the synthetic resin layer from peeling off at the time of mold release or upon receiving heat or impact. .

According to the sixth aspect, by molding the synthetic resin layers formed on the front and back surfaces of the core member so as to be connected to each other, the synthetic resin layers can be formed at the time of mold release or when subjected to heat or impact. Peeling can be prevented.

According to the seventh aspect, by covering the core member in its thickness direction with the synthetic resin of the same material, the thickness at the time of molding becomes thinner than before, and the generation of internal stress and distortion at the time of molding. Since the risk of deformation such as warpage and warp, formation of internal bubbles, etc. is reduced, a highly accurate plastic optical member can be obtained, and the cooling time at the time of molding is shortened, so that the molding cycle can be shortened. .

According to the eighth aspect, a support member for supporting the core member is provided so as to be retractable, and the support member is retracted from the inside of the cavity after the resin is injected, so that there is no trace of the support member on the periphery. Can be manufactured, and it is not necessary to previously provide a portion for supporting the optical member.

[Brief description of drawings]

FIG. 1 is a first embodiment of a plastic optical member according to the present invention.
FIG. 3 is a cross-sectional view showing the structure of FIG.

FIG. 2 is a second example of the plastic optical member according to the present invention.
FIG. 3 is a cross-sectional view (a) and a plan view (b) showing the structure of FIG.

FIG. 3 is a third example of the plastic optical member according to the present invention.
FIG. 3 is a cross-sectional view (a) and a plan view (b) showing the structure of FIG.

FIG. 4 is a fourth example of the plastic optical member according to the present invention.
FIG. 3 is a cross-sectional view showing the structure of FIG.

FIG. 5 is a fifth embodiment of the plastic optical member according to the present invention.
FIG. 3 is a cross-sectional view showing the structure of FIG.

FIG. 6 is a sixth embodiment of the plastic optical member according to the present invention.
FIG. 3 is a cross-sectional view showing the structure of FIG.

FIG. 7 is a seventh embodiment of the plastic optical member according to the present invention.
FIG. 3 is a cross-sectional view showing the structure of FIG.

FIG. 8 is a cross-sectional view showing a mold structure for insert molding suitable for manufacturing the plastic optical member of Example 5;

FIG. 9 is a cross-sectional view showing a state of resin injection in the mold structure.

[Explanation of symbols]

 1 Core Lens Body 2, 3 Resin Coating 11 Outer Collar Part OP Optical Effective Diameter D2, D3 Refractive Surface 12, 13 Recess 14 Through Hole

Claims (8)

[Claims] 1. A synthetic resin core member is housed inside,
A plastic optical member formed by molding a synthetic resin of the same material as that of the core member in at least a thickness direction of the core member. 2. The plastic optical member according to claim 1, wherein the shape of the core member is similar to that of the optical member coated with the synthetic resin at least in an optically effective range. 3. The plastic optical member according to claim 1, wherein the core member and the synthetic resin coating the core member have substantially the same thickness. 4. The plastic optical member according to claim 1, wherein the thickness of the synthetic resin coating the core member is smaller than the thickness of the core member. 5. The plastic optical member according to claim 1, wherein the core member and the synthetic resin layer are formed so as to mesh with each other. 6. The plastic optical member according to claim 1, wherein synthetic resin layers respectively covering the front and back surfaces of the core member are formed in a state of being connected to each other. 7. After forming a synthetic resin core member, the core member is introduced into a cavity of a mold, and a synthetic resin of the same material as the core member is injected into the cavity to form the core member. A method for manufacturing a plastic optical member, which comprises coating with the synthetic resin. 8. The mold according to claim 7, wherein a support member that supports the core member in the cavity is provided in the mold so as to be retractable, and the synthetic resin is supported in a state where the support member supports the core member. A method for manufacturing a plastic optical member, characterized in that the support member is retracted from the inside of the cavity after the injection and after the injection of the synthetic resin and before the curing of the synthetic resin.