JP2000006214A - Injection and compression molding method of optical molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the molding method of high precision excellent optical molding having neither weldline nor sinkmark. SOLUTION: In the injection and compression molding method of a thermoplastic resin optical molding, firstly, the volume of a cavity is enlarged to be larger than that of an object optical molding. Secondly, a molten thermoplastic resin is filled through an injection cylinder in the cavity. Thirdly, after that, the enlarged cavity is compressed to obtain the regular thickness of the molding. Fourthly, the excess thermoplastic resin caused by a pre-compression is sent back to the injection molder. Fifthly, the molten thermoplastic resin is held until an object molding is formed in the cavity. Lastly, the obtained molding is unloaded from the cavity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is suitable for the production of optical molded products in which almost no weld is generated by the injection compression molding method. More particularly, the present invention relates to an injection compression molding method for producing a high-precision optical molded product such as a spectacle lens with almost no weld.

[0002]

2. Description of the Related Art In recent years, the demand for plastic lenses has greatly increased. Plastic lenses are roughly classified into cast thermosetting allyl resins and transparent thermoplastic resin lenses such as polycarbonate resins and polyacryl resins manufactured by injection molding.

[0003] Recently, polycarbonate resin lenses have attracted attention and have been widely used as spectacle lenses which can be manufactured by an injection molding method, have a high refractive index, are light, have good ultraviolet absorbing performance, and have high impact resistance and high safety. It has come to be.

[0004] A number of methods for producing spectacle lenses by injection molding have been proposed. According to a known method, a semi-finished lens is molded by an injection molding method,
Thereafter, there is a method of finishing to a target optical shape by cutting and polishing, and a method of obtaining a lens having an optical shape as a finish lens by a single injection molding method. Especially in the latter case, when a concave lens is injection-molded as a fundamental problem due to the lens shape, since the portion corresponding to the outer peripheral portion of the lens is thick in the cavity, the flow of molten resin flowing from the gate is faster at the outer peripheral portion, and The part flows thinly because it is thin.

[0005] As a result, finally, the resin flows in the outer peripheral portion meet each other, and a weld line is generated. This becomes more remarkable as the focal length of the concave lens becomes shorter, not only deteriorating the optical characteristics but also significantly deteriorating the appearance. Depending on the outer diameter of the lens, a lens having a focal length of approximately -1 m or less rarely causes a weld line which is a problem in quality. However, concave lenses having a focal length of -1 m or more, particularly concave lenses having a focal length of -0.5 m or more, are liable to cause weld lines, which is problematic.

Various methods have been proposed to solve the problems caused by injection molding of these spectacle lenses. Among them, a typical method for eliminating the weld line is a method described in JP-B-61-19409, in which an overflow pocket is formed in the outer peripheral portion to relatively restrict the resin flow in the outer peripheral portion. Japanese Patent Application Laid-Open No. 62-83121 discloses a method of providing a side core in a cavity, and a method described in Japanese Patent Application Laid-Open No. 1-90716 in which minute irregularities are provided at the outermost periphery of a lens to restrict the flow of resin in the outer periphery. There is.

However, for example, when an overflow pocket or a side core is provided, the mold structure becomes complicated, and the thickness of the outer peripheral portion (edge) of a concave lens having a high number of lenses (sometimes called a minus lens) becomes very large. Instead, the weld line is not essentially eliminated by such a method.

In the side core method and the method of providing unevenness in the cavity, the flow of the molten resin in the cavity is disturbed, so that molding defects such as a flow mark and a cold flow are easily induced, and the mold releasability of the lens molded product is hindered. Or Further, these methods can hardly cope with a cylindrical surface or a toric surface in which the thickness of the outermost peripheral portion varies.

Further, the production of the spectacle lens by injection molding is as follows.
In general, since the method is carried out by a method of simultaneously molding a large number of kinds / a large number of lenses, installation and removal of accessories in the cavity become extremely complicated, and the kinds that can be molded are greatly limited.

On the other hand, the multi-stage compression method is a method for obtaining a lens with excellent surface accuracy, but it is a method for filling a resin amount corresponding to the amount of shrinkage, so that generation of a weld line is basically not eliminated.

Many other methods have been proposed as a countermeasure for such a weld line, for example, a method of controlling the temperature of a mold in a complicated manner, a method of using ultrasonic waves, and the like. Since the lens design is often limited, an optical lens molding method substantially free of weld lines has not been established.

[0012]

That is, an object of the present invention is to provide a high-precision optical molded product which hardly generates a weld line and which has excellent precision, and a molding method therefor.

[0013]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on a method for solving the above-mentioned drawbacks of the conventional method. As a result, in the method for injection-compression molding of an optical molded article made of a thermoplastic resin, the following method was used. The volume of the cavity is made larger than the desired volume of the optical molded product, (2) the molten thermoplastic resin is filled into the cavity through an injection cylinder, and (3) the enlarged cavity is then filled with the specified thickness of the molded product. (4) return the excess thermoplastic resin generated by the pre-compression to the injection cylinder, (5) hold the molten thermoplastic resin in the cavity until the desired molded article is formed, and then (6) Injection compression molding of optical molded products, characterized in that the molded product obtained is taken out of the cavity. Little optical molded articles and have completed the present invention found that the resulting.

The optical molded product described herein is an optical system that forms an image of an object by using refraction and reflection of light, and diverges or converges a light beam, and an interference phenomenon due to a phase difference between laser beams. Optical molded product using divergence. Specific examples thereof include a plastic spectacle lens and a projector lens. In particular, the present invention is suitable for molding minus spectacle lenses made of polycarbonate resin.

In the conventional injection compression molding method, compression is performed after shutting off by means of a runner or the like with a gate seal or the like, so that an excess amount of resin is stored in an overflow pocket or the like. In addition, since the amount of resin is small enough to compensate for the amount of shrinkage, a complicated mold structure such as a side core, unevenness, mold temperature control, and ultrasonic treatment was required to suppress the generation of weld lines.

The inventors of the present invention have intensively studied a method of returning molten resin to an injection cylinder, which was considered inappropriate with the conventional injection molding technology. As a result, the amount of excess resin can be reduced from a small amount to a large amount by a very simple method. It was possible to establish an injection compression molding method in which weld lines were hardly generated for lenses of any shape.

Hereinafter, the molding method of the present invention will be described in more detail. Although the injection molding machine used in the present invention is not particularly limited, it has a mold clamping force necessary as a basis for injection molding of an optical molded product, and a mechanism capable of controlling injection, compression, dwelling and the like with high accuracy in several steps. It is desirable to have. The shape of the screw mechanism is not particularly limited as long as it has a backflow prevention mechanism.
This molding machine may be any injection molding machine such as an in-line screw or a plunger type.

The mold used in the present invention is not particularly limited as long as it corresponds to compression molding. For example, a mold clamping compression method utilizing opening and closing of a platen (plate on which the mold is mounted), a compression cylinder of a molding machine platen, Either of the core compression methods using a ball screw or the like can be used. However, in order to completely eliminate the weld line, the cavity needs to be greatly opened, and the core compression method is preferable.

The mold clamping compression method is a method in which the mold parting surfaces on the fixed side and the movable side are opened at a predetermined interval, resin is injected, and then the parting surfaces are brought into contact by the mold clamping force. A compression method. The term "core compression method" refers to a means for contacting the respective parting surfaces of a mold during mold clamping before injection, injecting resin with a predetermined mold clamping force, and then compressing the resin. In the step of compressing after injection, the movable mirror surface is set in a molding machine, a mold, or the like, and is advanced by the compression mechanism in a direction in which the volume of the cavity is reduced, and compressed. Here, the compression mechanism refers to a hydraulic cylinder, a ball screw, or the like.

In the molding method of the present invention, it is not necessary to provide a complicated mechanism such as an overflow pocket and a side core in the mold, so that a mold having an extremely simple structure can be used.

As the thermoplastic resin used in the present invention, a transparent resin such as a polycarbonate resin, a polyacryl resin and a modified polyolefin resin can be used. Among them, polycarbonate resin is most preferred as an optical molded product, particularly as a minus spectacle lens material.

The polycarbonate resin which can be used in the present invention has a viscosity average molecular weight of up to 17,000 to 40,000 obtained by an interfacial polymerization method or a transesterification method, and more preferably has a viscosity average molecular weight of 20,000 to 30,000. good. Optical molded products, especially spectacle lenses are precision molded, it is important to accurately transfer the mirror surface of the mold to give a specified curvature and frequency, and a resin with good melt fluidity and low viscosity is desirable, If the viscosity is too low, the impact strength characteristic of the polycarbonate resin cannot be maintained. In addition,
The viscosity average molecular weight (M) as used herein is determined by using an Ostwald viscometer to determine the intrinsic viscosity [η] of a solution measured at 20 ° C. using methylene chloride as a solvent, and the following Schnell viscosity equation [η] = 1.23 × 10 ^-4 M ^0.83 .

Bisphenols for producing a polycarbonate resin are particularly preferably bisphenol A, but there is no particular limitation on polycarbonate resins polymerized from other known phenols.

The polycarbonate resin used in the present invention is:
An aromatic polycarbonate resin obtained by reacting a dihydric phenol with a carbonate precursor. Specific examples of the dihydric phenol used here include, for example, 2,2-bis (4-hydroxyphenyl) propane (commonly known as bisphenol A), bis (4-hydroxyphenyl) methane,
1,1-bis (4-hydroxyphenyl) ethane, 2,
2-bis (4-hydroxyphenyl) butane, 2,2-
Bis (4-hydroxyphenyl) octane, 2,2-bis (4-hydroxyphenyl) phenylmethane, 2,2
-Bis (4-hydroxy-3-methylphenyl) propane, 1,1-bis (4-hydroxy-3-tert-butylphenyl) propane, 2,2-bis (4-hydroxy-3-bromophenyl) propane, 2,2-bis (4
-Hydroxy-3,5-dibromophenyl) propane,
Bis (hydroxyaryl) alkanes such as 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane; 1,1-bis (hydroxyphenyl) cyclopentane, 1,1-bis (hydroxyphenyl) cyclohexane and the like Bis (hydroxyphenyl) cycloalkanes; 4,4′-dihydroxydiphenyl ether, 4,
Dihydroxyaryl ethers such as 4'-dihydroxy-3,3'-dimethyldiphenylether; 4,4 '
Dihydroxydiaryl sulfides such as -dihydroxydiphenyl sulfide and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide; 4,4'-dihydroxydiphenyl sulphoxide, 4,4'-dihydroxy-3,3'-dimethyldiphenyl Dihydroxydiaryl sulfoxides such as sulfoxide; 4,4′-
And dihydroxydiarylsulfones such as dihydroxydiphenylsulfone and 4,4′-dihydroxy-3,3′-dimethyldiphenylsulfone. These dihydric phenols may be used alone or in combination of two or more.

Of the above dihydric phenols, it is preferable that 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) be the main dihydric phenol component,
In particular, 70 mol% or more, particularly 8 mol%, of all dihydric phenol components.
Those in which 0 mol% or more is bisphenol A are preferred. Most preferred are aromatic polycarbonate resins wherein the dihydric phenol component is substantially bisphenol A.

The interfacial polymerization method and transesterification method for producing a polycarbonate resin will be briefly described. In the interfacial polymerization method using phosgene as a carbonate precursor, a reaction between a dihydric phenol component and phosgene is usually performed in the presence of an acid binder and an organic solvent. As the acid binder, for example, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide or an amine compound such as pyridine is used. As the organic solvent, for example, halogenated hydrocarbons such as methylene chloride and chlorobenzene are used. Further, a catalyst such as a tertiary amine or a quaternary ammonium salt can be used to promote the reaction, and a terminal stopper such as an alkyl-substituted phenol such as phenol or p-tert-butylphenol can be used as a molecular weight regulator. It is desirable to use. The reaction temperature is usually 0 to 40 ° C., the reaction time is preferably several minutes to 5 hours, and the pH during the reaction is preferably maintained at 10 or more.

In the transesterification method (melting method) using a carbonic acid diester as a carbonate precursor, a predetermined ratio of a dihydric phenol component and a carbonic acid diester are stirred while heating in the presence of an inert gas to form an alcohol or phenol formed. It is a method of distilling off kinds. The reaction temperature varies depending on the boiling point of the alcohol or phenol to be formed, but is usually in the range of 120 to 330 ° C. The reaction is carried out under reduced pressure from the beginning while distilling off alcohol or phenols produced. Further, a normal transesterification catalyst can be used to promote the reaction. Examples of the carbonic acid diester used in this transesterification reaction include diphenyl carbonate, dinaphthyl carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate and the like, and diphenyl carbonate is particularly preferred.

The polycarbonate resin of the present invention can contain a release agent, and this gives a favorable result. As the release agent, a saturated fatty acid ester is generally used. Erythritol esters are used. The release agent is used in an amount of 0.03 to 1 part by weight per 100 parts by weight of the polycarbonate resin. If necessary, a phosphite-based heat stabilizer may be added in an amount of 0.1 to 100 parts by weight of the polycarbonate resin.
001 to 0.1 part by weight may be blended. As a phosphite heat stabilizer, tris (nonylphenyl) phosphite, triphenylphosphite, tris (2,4-
Di-tert-butylphenyl) phosphite, tetrakis (2,4-di-tert-butylphenyl) -4,
4'-biphenylenediphosphonite, bis- (2,6-
Di-tert-butyl-4-methylphenyl) pentaerythritol-di-phosphite, bis (2,4-di-
tert-butylphenyl) pentaerythritol di-phosphite, tris (ethylphenyl) phosphite, tris (butylphenyl) phosphite and tris (hydroxyphenyl) phosphite are preferred,
Tris (nonylphenyl) phosphite and tetrakis (2,4-di-tert-butylphenyl) -4,
4'-biphenylenediphosphonite is particularly preferred.

For the purpose of improving weather resistance and cutting off harmful ultraviolet rays, the polycarbonate resin of the present invention may further contain an ultraviolet absorbent. As such an ultraviolet absorber, for example, a benzophenone-based ultraviolet absorber represented by 2,2'-dihydroxy-4-methoxybenzophenone; for example, 2- (3-tert-butyl-5-methyl-2-hydroxyphenyl) -5 -Chlorobenzotriazole, 2- (3,5-di-tert-butyl-2)
-Hydroxyphenyl) -5-chlorobenzotriazole, 2,2′-methylenebis [4- (1,1,3,3-
Tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- [2-hydroxy-
3,5-bis (α, α-dimethylbenzyl) phenyl]
-2H-benzotriazole and 2- (3,5-di-
Examples thereof include benzotriazole-based ultraviolet absorbers represented by (tert-amyl-2-hydroxyphenyl) benzotriazole, and these may be used alone or in combination of two or more. Among these ultraviolet absorbers, benzotriazole-based ultraviolet absorbers are preferred.

The polycarbonate resin of the present invention may further contain a bluing agent for canceling the yellow tint of the lens based on the polycarbonate resin or the ultraviolet absorber. As the bluing agent, any one can be used without any particular difficulty as long as it is used for a polycarbonate resin. Generally, anthraquinone dyes are easily available and preferred.

Next, the compression molding method of the present invention will be specifically described with reference to FIGS. FIG. 1 is a schematic diagram showing a cavity enlarged larger than the optical molded product volume before injection, FIG. 2 is a schematic diagram showing a state in which the enlarged cavity is filled with a molten thermoplastic resin, and FIG. FIG. 7 is a schematic diagram showing that a cavity formed is compressed to a prescribed thickness (center thickness) and excess molten thermoplastic resin is returned to the injection cylinder.

In the present invention, since a weld line occurs in an optical molded product having a difference in thickness, the minimum thickness and the maximum thickness of the optical molded product, for example, the thickness at the center of the concave lens (minimum thickness)
And the thickness of the outer peripheral portion of the lens (maximum thickness). Depending on the shape of the optical molded article, the ratio of its maximum thickness to its minimum thickness (100
X maximum thickness / minimum thickness) is 150% or more, especially 300%
If the content exceeds%, a weld line is generated.

Therefore, the cavity is enlarged before injection, and this ratio is reduced to a limit level at which almost no weld line is generated, that is, smaller than 150%, and more preferably 14%.
After the cavity is expanded to 0% or less and the molten resin is filled, the excess resin is returned to the injection cylinder to obtain an optical molded product, for example, a concave lens having a short focal length and having almost no weld line. The return of the resin to the cylinder can be confirmed by the fact that the measurement value of the injection stroke measuring device attached to the injection unit increases in the direction opposite to the injection of the resin.

The amount of compression of the cavity is determined by the design value of the type and representative thickness of the optical molded product (for example, in the case of a concave lens, the thickness of the central portion), molding conditions such as cylinder temperature and mold temperature, and the molding machine and mold to be used. In the case of forming a concave lens, which is a typical example of an optical molded product, it is necessary to increase the focal length as the focal length becomes shorter. The enlarged volume of the cavity at the time of injection with respect to the lens volume is calculated by the following formula based on the surface accuracy (deformation of surface, etc.), optical characteristics (focal length, aberration, etc.) of the optical molded product, and ease of molding. The volume ratio is preferably in the range of 110 to 500%. It is more preferably in the range of 120 to 400%, and particularly preferably in the range of 150 to 350%. If it exceeds 500%, the amount of resin to be discharged is large, so that the required compression pressure is increased, the heat resistance of the molten resin is deteriorated, and molding failure may be induced. The amount of compression caused by this compression refers to the difference between the representative thickness of the optical molded product before compression and the representative thickness of the optical molded product after compression. Expanded volume ratio (%) = 100 × (expanded cavity amount / cavity amount after compression) Here, the units of the expanded cavity amount and the cavity amount after compression are expressed in ml.

The preferred range of the enlarged volume ratio depends on the ratio of the wall thickness when forming a concave lens.
For example, the enlarged volume ratio is determined when the thickness ratio is small (for example, 3
(In the case of 00% or less) is preferably in the range of 110 to 200%, while when the wall thickness ratio is larger than that, 200 to 500%.
% Is preferred.

In the molding method of the present invention, the purpose is to enlarge the cavity so that no weld line is generated or to an allowable limit. It is difficult to completely eliminate the weld line once generated before compression by any means.

If the cavity is expanded to a predetermined thickness and cooled without compression to take out the lens, it is possible to confirm whether or not a weld line has occurred before compression. The compression amount is
The smaller the amount, the easier the molding, and it is preferable that the compression amount can be adjusted in terms of the mold structure.

In the present invention, in the injection stage, an excessive amount of the molten resin with respect to the weight of the optical molded product is charged. Immediately after filling is completed, it is compressed to a specified center thickness in a short time. The compression time depends on the type of the filling resin and the molding conditions, but is preferably within 5 seconds. When this time elapses for 5 seconds or more, the molten resin is cooled and a very high compression pressure is required due to an increase in viscosity.

The specified thickness mentioned here means a thickness within a standard range of a thickness represented by quality control of an optical molded product. For example, the thickness at the center of the lens, the average thickness at the mirror surface, and the like.

In the compression, after the injection is completed, the resin pressure is made lower than the cavity pressure by the compression, and the volume of the cavity is reduced by the compression, and the excess molten resin flows back into the injection cylinder from the gate via the runner and the sprue. The resin that has flowed back is kneaded with the resin that has been plasticized in the next cycle and re-injected. After the completion of the compression, cooling is performed by applying a holding pressure to compensate for the shrinkage of the molten resin to obtain a molded product.

[0041]

The present invention will be described in detail below with reference to examples and comparative examples. In the examples, the length of the weld line was measured using a polarization strain meter (PS-5, manufactured by Riken Keiki Co., Ltd.). What is the measurement of the weld line with a polarization distortion meter?
As shown in FIG. 4, light diffused by frosted glass is emitted from a fluorescent lamp (30 W annular fluorescent lamp) at a distance of approximately 1
An optical molded product is placed between two polarizing plates whose polarization planes of about 5 cm are substantially perpendicular to each other, and the weld line length of the optical molded product is measured. At this time, the length of the weld line was measured using a caliper (CS-S15M manufactured by Mitutoyo) as shown in FIG.
Was measured for weld line length.

Example 1 100 parts by weight of a polycarbonate resin having a viscosity average molecular weight of 22,500 synthesized from bisphenol A and phosgene was added to 100 parts by weight of an ultraviolet absorber 2- (2'-hydroxy-5'-t-octyl) -benzotriazole. 3 parts by weight, heat stabilizer 0.03 parts by weight of tris (nonylphenyl) phosphite and 0.2 parts by weight of a release agent stearic acid monoglyceride were blended, and the core was compressed into an injection molding machine (SYCAPSG220) manufactured by Sumitomo Heavy Industries, Ltd. Injection compression molding of the following polycarbonate resin minus spectacle lens was performed using a mold. Front curvature radius 293.00mm Rear curvature radius -73.25mm Center thickness 1.5mm Edge thickness 10.0mm Lens outer diameter 77.5mm Rear vertex focal length -166.67mm The main molding conditions at this time are as follows. It was as follows. Cylinder temperature 280 to 300 ° C Mold temperature 125 ° C Molding cycle 240 seconds

After the movable lens mold was retracted, the cavity was expanded to a lens center thickness of 7.6 mm (expanded volume ratio of about 215%) before injection, and then the resin was filled into the cavity, and the resin pressure became 30 MPa. As shown in FIG. 6, the movable-side lens mold was compressed until the compression amount adjusting rod came into contact with the die set so that the lens center thickness became 1.5 mm, and excess resin was returned to the injection cylinder. The return of the surplus resin to the cylinder was confirmed by the fact that the value measured by the injection stroke measuring device increased in the direction opposite to that at the time of injection. Thereafter, after cooling was completed, the concave lens (minus lens) molded product was taken out. In the obtained concave lens, no weld line was observed by measurement with a polarization distortion meter.

[Comparative Example 1] The same conditions as in Example 1 except that the cavity before injection was set to have a lens center thickness of 1.6 mm and the excess resin was compressed without returning to the injection cylinder. Then, the same type of polycarbonate resin minus spectacle lens was compression molded. The obtained concave lens (minus lens) molded product has a weld line of 25 to
35 mm was generated, and the lens was of low quality.

[0045]

As described above, the detailed description and examples of the present invention,
As is apparent from the comparative examples and the like, the injection compression molding method of the present invention can produce an optical molded product having no weld line with an extremely simple mold structure and molding method, and is suitable for injection compression molding of eyeglass lenses and the like. It is used for
In particular, it is useful for injection compression molding of minus spectacle lenses made of polycarbonate resin.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a cavity enlarged beyond the optical molded product volume before injection.

FIG. 2 is a schematic diagram showing a state in which an expanded cavity is filled with a molten thermoplastic resin.

FIG. 3 is a schematic diagram showing that an enlarged cavity is compressed to a predetermined thickness (center thickness) and excess molten thermoplastic resin is returned to an injection cylinder.

FIG. 4 is a schematic diagram showing a structure of a strain measuring device.

FIG. 5 is a schematic view of a lens in which a weld line has occurred.

FIG. 6 is a schematic diagram showing a mold structure and a state of compression.

[Explanation of symbols]

 1. 1. enlarged cavity 2. Fixed side mirror surface Movable mirror surface 4. Molten resin 5. Screw 6. 6. compressed cavity 7. Polarization plates whose polarization planes are perpendicular to each other Sample (optical molded product) 9. Frosted glass 10. Fluorescent light 11. Sample (minus spectacle lens) 12. Weld line length Compression amount adjustment rod 14. Die set 15. Movable mirror surface 16. Enlarged cavity 17. Fixed mirror surface 18. Compressed cavity

Claims (3)

[Claims] In a method of injection-compression molding an optical molded product made of a thermoplastic resin, (1) the volume of a cavity is larger than the volume of a target optical molded product, and (2) the heat of melting is formed in the cavity. Filling the plastic through an injection cylinder, (3) then compressing the enlarged cavity to a specified thickness of the molded article, (4) returning excess thermoplastic resin generated by pre-compression to the injection cylinder,
(5) Injection compression molding of an optical molded product, wherein the molten thermoplastic resin is held in a cavity until a desired molded product is formed, and (6) the obtained molded product is taken out of the cavity. Method. 2. The injection compression molding method for an optical molded product according to claim 1, wherein the optical molded product is a minus spectacle lens made of a polycarbonate resin. 3. A minus spectacle lens made of polycarbonate resin having a weld line of 20 mm or less.