JP2000006216A - Injection and compression molding method of optical molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection and compression molding method, with which an excellent profile irregularity and favorable optical characteristics can be obtained. SOLUTION: In the injection and compression molding method of a thermoplastic resin optical molding, firstly, the volume of a cavity 3 is enlarged to be larger than that of an object optical molding. Secondly, a molten thermoplastic resin is injected through an injection cylinder in the enlarged cavity 3. Thirdly, after that, the enlarged cavity is compressed so as to obtain the regular thickness of the molding or a thickness thinner by 200 μm than its regular thickness. Fourthly, the resin pressure in the injection cylinder and the compression pressure in the cavity 3 are adjusted or changed so as not to exceed the width of change from the regular thickness of the molding over 100 μm in order to finally realize the regular thickness of the molding. 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]

The present invention is applied to a case where an optical molded product is obtained by an injection molding method. More specifically, the present invention relates to a method for producing a thermoplastic resin lens such as a spectacle lens made of a polycarbonate resin by an injection compression molding method, which relates to an injection compression molding method having excellent surface accuracy and excellent optical characteristics.

[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.

When a finish lens is molded by injection molding, optical distortion (sinking) is caused by resin shrinkage due to cooling and solidification.
Or surface accuracy is likely to be reduced. This phenomenon is more remarkable in a molded product having a large thickness difference and a lens having a large difference in shrinkage. As a typical method for resolving the difference in shrinkage due to cooling and solidification, there is a multi-stage compression method in which a resin amount corresponding to the amount of shrinkage is filled in advance as described in JP-B-6-71755. . However, such a method does not have sufficient surface accuracy and tends to cause variations in optical molded products. The surface accuracy described here means whether or not the curvature and flatness of the surface fall within a designed standard range.

[0006] These known injection compression molding methods have the following two disadvantages. First, since the cavity is filled with resin at the time of injection and the injection resin pressure is not sufficiently applied, the surface precision and optical distortion of the optical molded product are significantly affected. That is, at the time of completion of the injection for forming the optical molded product surface layer,
Insufficient injection resin pressure is applied. This causes optical distortion and surface defects. Such optical distortion includes optical distortion that can be easily confirmed with the naked eye, optical distortion that can be confirmed by anti-mapping of a fluorescent lamp on the lens surface, and optical distortion that is thinly confirmed by a polarizing plate in a ring shape. Observation with a polarizing plate makes it easier to find such a defective phenomenon.

These are fatal defects when used as lenses. These failure phenomena are likely to occur at the center of the plus lens (convex lens) and at the periphery of the minus lens (concave lens). This is mainly caused by insufficient resin pressure being applied to the inside of the cavity at the completion of the injection in which the surface layer of the lens is formed.

Second, the state of resin filling in the injection step of the injection molding machine includes the dispersion in the injection step and the dispersion in the metering step, and the state of the resin in the cavity before compression greatly increases for each molding shot. Often different.
For this reason, variations that exceed an allowable range from the viewpoint of quality control of the optical molded product often occur. Conventional injection compression molding is greatly affected by this variation.

Referring to FIG. 1, one method of forming a finish lens by a conventional injection compression molding method will be briefly described. A cavity 3 formed by opposing the fixed-side mirror surface 1 and the movable-side mirror surface 2 is provided with an extra width equal to the compression amount than a predetermined shape. The movable mirror surface is attached to the ejector plate 7 by a base 8. The compression amount adjusting rod 4 is also attached to the ejector plate, and a space 6 having a width equal to the compression amount is provided between the rod 6 and the fixed die set 5.

In the compression stroke, the compression plate 9 receives a compression force 10 from the compression cylinder provided on the platen of the molding machine, whereby the ejector plate advances, and the pedestal, the movable mirror surface, and the compression amount adjusting rod advance.

The compression amount adjusting rod moves in advance in a space equal to the compression amount, and comes into contact with the die set to generate a reaction force 11 against the compressive force. Compression to thickness, ie the point of this method, is to determine the cavity thickness by the mechanical advance limit.

However, this method has the following disadvantages. 1) Since a reaction force 11 is generated with respect to the compression force 10, a sufficient compression pressure does not act on the cavity. In the pressure holding and cooling steps, the compression pressure applied to the cavity cannot be controlled. For this reason, the radius of curvature was slightly changed between the thin portion and the thick portion, and the surface accuracy was not sufficient.

2) A load of several tens to several hundreds of tons is applied to the ejector plate due to the compressive force and the reaction force, and the ejector plate is bent. This bending causes the movable mirror surface to vibrate, thereby deteriorating the surface accuracy of a thin portion of the product.

3) Since a large stress is applied to the ejector plate, the compression amount adjusting rod, and the portion of the fixed die set where the compression amount adjusting rod comes into contact, it is necessary to have sufficient bending strength and buckling strength. In particular, the portion of the fixed-side die set where the compression amount adjusting rod and the approximate rod are in contact with each other requires a material that easily undergoes plastic deformation and has a sufficient contact area and strength. This complicates the mold structure and increases the size of the mold itself.

[0015]

SUMMARY OF THE INVENTION One of the objects of the present invention is to provide a method for molding an optical molded article having high precision and excellent properties. A second object is to provide a good quality lens molded article by using the molding method of the present invention.

[0016]

The present inventors 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 an optical molded product made of a thermoplastic resin, (1) The volume of the cavity is made larger than the desired volume of the optical molded product, (2) a molten thermoplastic resin is injected into the cavity through an injection cylinder, and (3) the enlarged cavity is then filled with a specified thickness of the molded product. Or (4) compressing the resin pressure in the injection cylinder and the compression pressure in the cavity so that the final thickness of the molded product becomes the prescribed thickness of the molded product. Adjust or fluctuate in the range where the fluctuation width does not exceed 100 μm,
(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. According to the method, it has been found that a sufficient compression pressure is applied to the cavity and that the compression pressure can be controlled even in the dwelling and cooling steps, so that it is possible to obtain an optical molded product with very good surface accuracy, and completed the present invention.

The optical molded product described herein refers to 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 caused by 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 a spectacle lens made of a polycarbonate resin.

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 may be any one that is compatible with compression molding, and may be any of a mold clamping compression method using opening and closing of a platen, a core compression method using a compression cylinder of a molding machine platen, and a ball screw. Available.

The mold clamping compression method is a method in which the mold parting surfaces of the fixed and movable sides are opened at a predetermined interval, resin is injected, and then the parting surfaces are brought into contact by a mold clamping force to be compressed. Point out. In the core compression method, in mold clamping before injection, the respective parting surfaces of the mold are brought into contact with each other, and a predetermined mold clamping force is applied to inject the resin. In the post-injection compression step, the mirror surface is installed in a molding machine, a mold, or the like, and is advanced by a 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.

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 preferable as the optical resin 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. Eyeglass 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 low-viscosity resin with good melt fluidity is desirable, but if the viscosity is too low The impact strength characteristic of polycarbonate resin cannot be maintained. In addition, the viscosity average molecular weight (M) mentioned here is obtained by using a 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.
In the prior art, as shown in FIG. 1, when the optical molded product reaches a predetermined thickness, the compression amount adjusting rod 4 comes into contact with the die set 5 to generate a reaction force 11 from the die set. Therefore, the compression force 10 is not sufficiently applied to the cavity 3, and even if the compression force 10 is increased or decreased, the compression force 10 is not increased.
Is absorbed as the reaction force 11 and is not reflected as the pressure of the cavity 3 during molding. For this reason, pressure is not sufficiently applied to a portion far from the gate or a thick portion, and surface deformation occurs.

FIG. 2 shows the concept of the injection compression molding method of the present invention. According to the present invention, instead of generating a reaction force to the compression force 10 from the mold structural parts, the resin pressure 13 from the injection cylinder is reduced.
Caused by Therefore, the compression pressure 10 is sufficiently transmitted to the cavity, and when the compression pressure 10 is increased and decreased, the compression pressure 10 is directly reflected as the pressure of the cavity. In the compression step, the resin pressure 13 is set lower than the compression pressure 10 to compress the cavity. Then, after the representative thickness of the cavity reaches the predetermined thickness of the optical molded product, the resin thickness and the compression pressure are adjusted or changed to set the representative thickness of the cavity, and finally the standard of the predetermined thickness of the optical molded product. To control within. According to the present invention, it is possible to control the pressure in the cavity 3 by the compression pressure 10 during the pressure holding process, which was not possible with the conventional technology, and it is possible to secure a sufficient compression pressure.

The compression step described here means that the representative thickness of the enlarged cavity is up to a predetermined thickness or to a thickness smaller by 200 μm, preferably 20 μm.
Refers to a process up to compression to a thickness of less than 200 μm, more preferably 20 to 180 μm. The pressure-holding step described here refers to a step from the completion of the compression step to the time when the injection molding machine starts measuring.

In the compression step and the dwelling step, in the prior art, a compression force ranging from tens to hundreds of tons depending on the type and size of the optical molded product and the number of shots per shot must be supported by the compression amount adjusting rod. Must. Therefore, the compression amount adjusting rod 4 must have sufficient buckling strength. In addition, a portion where the compression amount adjusting rod 4 and the die set 5 are in contact with each other needs to have sufficient strength against plastic deformation.
The ejector plate needs to have sufficient strength against bending stress. Therefore, the size of the mold component is increased, and an expensive and strong material is required. Therefore, the mold becomes large and the mold becomes expensive. As the mold becomes larger, a large-sized molding machine is required, which further increases the cost. In the molding method of the present invention, since a reaction force against the compressive force 10 is generated by the resin pressure 13, the strength of the movable mirror surface 2, the pedestal 8, the ejector plate 7, and the compressive plate 9 enough to withstand the compressive stress is considered. Good. Therefore, the mold can be reduced in size without requiring excessive strength. Also, calculation of the strength of the mold is easy.

The fundamental difference of the molding method of the present invention from the prior art is that the space of the compression amount adjusting rod is equal to the compression amount in the conventional method, but is set to be more than the compression amount in the molding method of the present invention. . As a result, the resin pressure 13 is applied in a state where the adjustment rod and the fixed die set do not come into contact with each other even when the adjustment rod is compressed by a predetermined amount to balance the compression pressure 10 and control the compression amount, thereby controlling the representative thickness of the optical molded product.

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.

The amount of compression described here refers to the difference between the representative thickness of the cavity before compression and the representative thickness of the cavity during or after compression.

The compression pressure described here is a value obtained by multiplying the maximum compression force generated by a molding machine or a compression mechanism of a mold by a set value with a maximum value of 1, and that value is a portion movable at the time of compression and in contact with the resin. This is a value obtained by dividing the projected area of the portion to be projected in the platen direction. The maximum compression force is determined by the design of the molding machine and the compression mechanism of the mold. The projected area of the part movable in compression and in contact with the resin is, for example, the projected area of the optical molded product in the platen direction in the case of the core compression method, and the projected area of the runner in the platen direction in the mold clamping compression method. Is added.

The resin pressure mentioned here indicates a resin pressure obtained by converting the hydraulic pressure of the injection cylinder from the ratio of the square of the diameter of the hydraulic injection cylinder to the square of the screw diameter, or a resin pressure measured by a pressure sensor. This value depends on the design of the molding machine.

The balance between the resin pressure and the compression pressure described herein means that (3) after the compression step, and (4) in the dwelling step, the resin thickness is adjusted so that the representative thickness of the cavity falls within a predetermined thickness standard. Adjusting (or fluctuating) pressure and compression pressure. Specifically, in the case of the embodiment, the resin pressure is 63.3M.
The compression pressure was 64.1 MPa with respect to Pa. The compression pressure is 0.8 MPa higher than the resin pressure. This is due to the accuracy of the mold, the resistance of the molding machine, and the accuracy of the oil pressure measurement at the molding machine and other errors. It is not necessary to make the resin pressure and the compression pressure the same, and the representative thickness of the cavity (the representative thickness of the optical molded product) may be set within a standard of a predetermined thickness. Further, the resin pressure and the compression pressure at the time of this balance differ depending on the mold design, the shape and size of the optical molded product, the type of the molding machine, and the type of the resin.

This will be described in detail with reference to FIG. The structure of FIG. 2 is basically the same as that of FIG. 1 except that a magnet scale 12 for measuring the amount of compression is attached to the ejector plate for adjusting the amount of compression.

The magnet scale is installed to measure the amount of movement of the ejector plate, but may be installed on a compression cylinder or the like. In addition to the magnet scale, it may be measured by a rotary encoder, linear scale, micrometer, dial gauge, laser displacement meter, infrared displacement meter, limit switch, etc.
In short, any method may be used as long as the amount of movement (the amount of compression) of the movable mold mirror surface is detected by some means.

First, the cavity is enlarged from the volume of the optical component to be obtained. When expanding the cavity, the percentage of the expanded cavity volume at the time of injection with respect to the optical component volume depends on the surface accuracy (surface deformation, etc.), optical characteristics (focal length, aberration, etc.) The range of the volume ratio of 110 to 500% calculated by the following formula is preferable from the viewpoint of easiness. It is more preferably in the range of 120 to 400%, and particularly preferably in the range of 150 to 350%. 5
If it exceeds 00%, a large amount of resin is discharged, so that the required compression pressure may be increased, the heat resistance of the molten resin may be deteriorated, and molding failure may be induced. The amount of compression caused by this compression refers to the difference between the product representative thickness of the optical part before compression and the optical part 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 preferable range of the enlarged volume ratio depends on the ratio of the wall thickness when a concave lens is formed.
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, it is important to prevent the occurrence of weld lines, optical distortion and surface defects or to enlarge the cavity to an acceptable limit. It is difficult to completely eliminate weld lines, optical distortion, and surface defects once generated before compression by any means.

After the resin is injected into the cavity in the injection step, the process proceeds to the compression step. As shown in FIG.
In step 9, the resin pressure 20 is set smaller than the compression pressure 21 to compress the resin to a predetermined thickness. The typical thickness of the cavity depends on the time of this compression process and the resin pressure and compression pressure.
(Representative thickness of optical molded product) is compressed to a predetermined thickness. The time for the compression step 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. Due to this high compression pressure, distortion may remain in the thin portion of the optical molded product.

Thereafter, the resin pressure 22 and the compression pressure 23 are balanced, and the process proceeds to the pressure maintaining step 37. At this time, the resin pressure 2
The movable mirror surface 2 may come into contact with the fixed mirror surface 1 due to the relationship between 2, the compression pressure 23 and the compression process time 19. For example, this corresponds to a case where the compression step time 19 is too long or a case where the compression pressure 21 is large. When the mirror surfaces come into contact with each other, the mirror surface is broken and the mirror surface becomes unusable. In order to avoid such a situation where mirror surfaces come into contact with each other, it is desirable to set the space 6 with the compression amount adjusting rod to be smaller by 0.2 to 0.6 mm of the product thickness.

In the compression step 19, as shown in FIG. 4, the thickness is within a range of 200 μm (preferably 20 to 2) from the specified thickness.
(More preferably, 20 to 180 μm), and it is desirable to control the resin pressure 20, the resin pressure time 18 in the compression step, the compression pressure 21, and the compression pressure time 17 in the compression step and push it back to a predetermined thickness. . An example of a specific setting is a time 1 for increasing the resin pressure from a time 17 for decreasing the compression pressure.
It is also possible by delaying from eight. By pushing back in this manner, excessive pressure applied to the thin portion of the molded product is released, and the pressure becomes uniform throughout the molded product. If the compression amount 25 is within 200 μm or less, the surface accuracy is improved and the optical distortion is reduced. If it exceeds 200 μm, the molding stability such as the stability of the lens power will deteriorate.

As described above, in the molding method of the present invention, the compression pressure can be controlled even in the pressure holding step. 3 and 4, in the pressure-holding step, the resin pressure 22 is hardly transmitted to the cavity because the sprue and the gate gradually solidify as the cooling progresses, and the compression pressure 23 exceeds the resin pressure 22 and the compression amount is increased. It gradually increases 24. Also, the compression amount gradually increases 24 due to the contraction of the resin. A change in the amount of compression over time causes a change in the radius of curvature between a thinned portion that is already solidified and a thickened portion that is solidifying.

As shown in FIG. 5, the resin pressure 27 and the compression pressure 28 are balanced in multiple stages with the progress of the cooling, and the variation in the representative thickness of the cavity, that is, the variation in the compression amount 24 (hereinafter, referred to as the variation 24)
The amount of change in the representative thickness of the cavity is referred to as the amount of change in the amount of compression. ) Is controlled to 100 μm or less, preferably 50 μm or less. By doing so, a uniform radius of curvature is obtained from the central portion to the peripheral portion. Explaining specifically how to set it, the measured value of the compression amount measuring device when the representative thickness of the cavity reaches a predetermined thickness is set to 0. When the amount of compression increases and the representative thickness of the cavity fluctuates, the resin pressure is increased or the compression pressure is decreased. If the amount of compression decreases and the representative thickness of the cavity fluctuates, the resin pressure is reduced or the compression pressure is increased. The measurement of the compression amount is performed by a compression amount measuring device such as the above-described magnet scale. In order to simplify the setting, it is preferable to feed back the displacement of the magnet scale or the like to the setting of the resin pressure and the compression pressure of the molding machine by using a loop circuit.

[0051]

The present invention will be described below in detail with reference to examples. In the examples and comparative examples, evaluation items and evaluation methods for optical molded products will be described below.

(1) Refractive power and radius of curvature Moire type laser interferometer OMS-40 manufactured by Rotorex Co., Ltd.
1 was used to evaluate the measurement of the radius of curvature. The refractive power is calculated by using the following equation to calculate the radius of curvature of the mirror surface of the mold used and the optical molded product (in this case, the lens) at a refractive index of 1.586 and a refractive power of
It was converted to ter and evaluated. The smaller the difference in refractive power between the mirror surface and the optical molded product, the better. Refractive power = 586 / (radius of curvature) Here, the unit of the radius of curvature is mm.

(2) Surface accuracy Moire type laser interferometer OMS-40 manufactured by Rotorex Co., Ltd.
1 was used to evaluate the surface accuracy. The evaluation of the surface accuracy was determined by the following five steps. 5 Moire interference fringes are not displaced. 4 Moire interference fringes are less than 25% of the fringe interval. 3 The displacement of the moire interference fringes is 50% or less of the fringe interval. 2 Moire interference fringes are less than 100% of the interference fringe interval. 1 Moire interference fringes are shifted by 100% or more of the interference fringe interval.

(3) Fluorescent Light Observation In fluorescent light observation, as shown in FIG. 6, the lens is formed about 30 cm below the eye 29 and approximately 15 cm above the lens at approximately the eye level and about 15 cm away from the eye. Tubular 30
This was performed by observing the reflected image of the W fluorescent lamp 30. The evaluation was made in the following five steps. 5. The image of the fluorescent lamp has a smooth and uniform curve. 4 The image of the fluorescent lamp is smooth, but the radius of curvature changes within two places. 3 The image of the fluorescent lamp is smooth, but the radius of curvature changes within four places. 2 The image of the fluorescent lamp is bent within two places. 1 The image of the fluorescent lamp is bent at two or more places.

(4) Observation of Polarizing Plate (Optical Distortion and Weld Line) The optical distortion and the weld line were measured by using a polarization distortion meter (manufactured by Riken Keiki Co., Ltd.).
Evaluation and length were measured using S-5), respectively. As shown in FIG.
4 (30W annular fluorescent lamp) as a light source, frosted glass 33
The optical diffused article was evaluated by placing an optical molded product 32 between two polarizing plates 31 whose polarization planes having an interval of about 15 cm are substantially perpendicular to each other. The evaluation was performed based on the following criteria. 5 There are no interference fringes in the part where the lens is used. 4 Interference fringes shifted by 0.5 wavelength are observed in the portion where the lens is used. 3 One interference fringe shifted by one wavelength is observed in the portion where the lens is used. 2 Two interference fringes shifted by one wavelength are confirmed in the portion where the lens is used. 1 Two or more interference fringes shifted by one wavelength are confirmed in the lens specification portion.

In the present embodiment, the portion using the lens described here indicates a range of 70 mm from the lens center with respect to the lens outer diameter of 77.5 mm. The weld line length 36 was measured using a caliper (CS-S15M manufactured by Mitutoyo) and the weld line length in FIG. 8 was measured.

(5) Amount of Compression The amount of compression was measured using a magnet scale (manufactured by LH-20B SONY) installed in a molding compression cylinder.

Example 1 An ultraviolet absorber 2- (2'-hydroxy-5'-t-octyl) -benzotriazole was added to 100 parts by weight of a polycarbonate resin having a viscosity average molecular weight of 22500 synthesized from bisphenol A and phosgene. 3 parts by weight, tris (nonylphenyl) phosphite 0.03 part by weight of heat stabilizer and 0.2 part by weight of monoglyceride stearate were mixed together, and the core was added to an injection molding machine (SYCAPSG220) manufactured by Sumitomo Heavy Industries, Ltd. Injection compression molding of a spectacle concave lens having the following specifications was performed using a compression 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

The movable lens mold is retracted, and the cavity is expanded to a lens center thickness of 7.6 mm (expansion volume ratio of about 215%) before injection, and then the resin is filled into the cavity, and the resin pressure is increased to 56.8 MPa. Figure 3
The molding was carried out by the method shown in FIG. In the compression step, the movable lens mold was compressed until the lens center thickness became 1.5 mm, and excess resin was returned to the injection cylinder. At this time, the compression amount adjusting rod and the die set are not in contact with each other. This was confirmed by attaching red chalk to the tip of the compression rod and not attaching red chalk to the die set. 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. The resin pressure in the compression process is 1
The time applied at 2.4 MPa is 2.14 seconds, and the compression pressure is 10
The time applied at 2.56 MPa was 2.14 seconds. Thereafter, in the pressure holding step, the resin pressure is 63.3 MPa, and the compression pressure is 6
The balance was set at 4.1 MPa. The compression amount fluctuated in the direction of thinning the optical molded product by 165 μm (a fluctuation range of the compression amount) in the pressure holding step. Thereafter, after cooling was completed, a minus spectacle lens (concave lens) made of a polycarbonate resin was taken out. Table 1 shows the evaluation results of the obtained minus spectacle lenses made of polycarbonate resin.

[Comparative Example 1] Using the mold of Example 1, the compression amount adjustment space was set to 1 mm, and the movable mold was opened by 1 mm more than a predetermined lens center thickness of 1.5 mm before injection.
5 mm. In the injection step, a resin of approximately 100 to 105% of the cavity volume was injected. In this case, there was no return of the resin to the cylinder. This was confirmed by the fact that the value measured by the injection stroke measuring device did not increase in the direction opposite to that at the time of injection. Then, 102.56MP
The compression force of a was applied, and the compression amount adjusting rod was compressed by coming into contact with the fixed-side die set. The contact of the compression amount adjusting rod with the die set was confirmed by the fact that the red chalk attached to the tip of the compression rod adhered to the die set. Table 1 shows the evaluation results of the obtained minus spectacle lenses made of polycarbonate resin.

[Embodiment 2] In Embodiment 1, in the compression step, the movable side lens mold is set to a lens center thickness of 1.5 mm.
Compress to an additional 100 μm (compression pushback amount)
Excess resin was returned to the injection cylinder. At this time, the compression amount adjusting rod and the die set are not in contact with each other. The resin pressure in the compression step was 12.4 MPa and the time taken was 2.10.
Seconds, the compression pressure is 102.56 MPa and the time applied is 2.1.
6 seconds. After that, in the pressure holding step, the resin pressure was set to 63.3MP.
a, The compression pressure was set to 64.1 MPa to balance. The amount of compression is 155 μm in the dwelling process (the fluctuation range of the amount of compression)
The optical molded product fluctuated in a direction to become thinner. Then, after cooling was completed, a polycarbonate resin minus was taken out. Table 1 shows the evaluation results of the obtained minus spectacle lenses made of polycarbonate resin.

Example 3 In Example 1, in the compression step, the movable-side lens mold was set to a lens center thickness of 1.5 mm.
Compress further by 100μm (compression return amount)
Excess resin was returned to the injection cylinder. At this time, the compression amount adjusting rod and the die set are not in contact with each other. The resin pressure in the compression step was 12.4 MPa and the time taken was 2.10.
Seconds, the compression pressure is 102.56 MPa and the time applied is 2.1.
6 seconds. After that, in the pressure holding step, the resin pressure was set to 63.3MP.
a, The compression pressure was set to 64.1 MPa to balance. Thereafter, the resin pressure was increased from 63.3 MPa to 90 seconds for 2 seconds.
It was gradually increased by 68.7 MPa at intervals of seconds.
After the balance of the compression pressure, the compression pressure was gradually decreased from 64.1 MPa to 42.5 MPa at intervals of 2 to 60 seconds. The compression amount fluctuated by 35 μm (a fluctuation width of the compression amount) in the pressure holding step. After the cooling was completed, the concave lens (minus lens) molded product was taken out. Table 1 shows the evaluation results of the obtained minus spectacle lenses made of polycarbonate resin.

Example 4 100 parts by weight of a polycarbonate resin having a viscosity average molecular weight of 22500 synthesized from bisphenol A and phosgene was added to 100 parts by weight of an ultraviolet absorbent 2- (2'-hydroxy-5'-t-octyl) -benzotriazole. 3 parts by weight, tris (nonylphenyl) phosphite 0.03 part by weight of heat stabilizer and 0.2 part by weight of monoglyceride stearate were mixed together, and the core was added to an injection molding machine (SYCAPSG220) manufactured by Sumitomo Heavy Industries, Ltd. Injection compression molding of a convex lens for spectacles having the following specifications was performed using a compression mold. Front curvature radius 97.67 mm Rear curvature radius -146.50 mm Center thickness 3.7 mm Edge thickness 1.0 mm Lens outer diameter 77.5 mm Rear vertex focal length 500.0 mm Injection resin pressure before compression 56.8 MPa

The movable lens mold is retracted, and the cavity is expanded to a center thickness of the lens of 5.1 mm (expansion volume ratio of about 160%) before injection, and then the resin is filled in the cavity, and the resin pressure is increased to 56.8 MPa. Figure 3
The molding was carried out by the method shown in FIG. In the compression step, the movable lens mold was compressed until the lens center thickness became 3.7 mm, and excess resin was returned to the injection cylinder. At this time, the compression amount adjusting rod and the die set are not in contact with each other. This was confirmed by attaching red chalk to the tip of the compression rod and not attaching red chalk to the die set. 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. The resin pressure in the compression process is 1
The time applied at 8.6 MPa is 0.42 seconds, and the compression pressure is 10
The time applied at 2.56 MPa was 0.42 seconds. Thereafter, in the pressure holding step, the resin pressure is 63.3 MPa, and the compression pressure is 6
The balance was set at 4.1 MPa. After this, after the cooling is completed, a plus spectacle lens made of polycarbonate resin
(Convex lens) was taken out. The amount of compression is 135μ in the holding process
m (fluctuation width of the amount of compression) The optical molded product fluctuated in a direction to become thinner. Table 1 shows the evaluation results of the obtained polycarbonate resin plus spectacle lenses.

[Comparative Example 2] Using the mold of Example 4, the compression amount adjustment space was set to 1 mm, and the movable mold was opened 1 mm more than a predetermined lens center thickness of 3.7 mm before injection.
7 mm. In the injection step, a resin of approximately 100 to 105% of the cavity volume was injected. In this case, there was no return of the resin to the cylinder. This was confirmed by the fact that the value measured by the injection stroke measuring device did not increase in the direction opposite to that at the time of injection. Then, 102.56MP
The compression force of a was applied, and the compression amount adjusting rod was compressed by coming into contact with the fixed-side die set. The contact of the compression amount adjusting rod with the die set was confirmed by the fact that the red chalk attached to the tip of the compression rod adhered to the die set. Except for the above, under the same conditions as in Example 4, a positive spectacle lens made of the same kind of polycarbonate resin was compression molded. Table 1 shows the evaluation results of the obtained polycarbonate resin plus spectacle lenses.

[Embodiment 5] In Embodiment 4, in the compression step, the movable lens mold is set to a lens center thickness of 3.7 mm.
Compress to an additional 100 μm (compression pushback amount)
Excess resin was returned to the injection cylinder. At this time, the compression amount adjusting rod and the die set are not in contact with each other. The resin pressure in the compression step was 18.6 MPa and the time applied was 0.39.
Seconds, the compression pressure is 102.56MPa and the time applied is 0.4
4 seconds. After that, in the pressure holding step, the resin pressure was set to 63.3MP.
a, The compression pressure was set to 64.1 MPa to balance. The amount of compression is 145 μm in the holding process (the fluctuation width of the amount of compression)
The optical molded product fluctuated in a direction to become thinner. Thereafter, after the cooling was completed, the plus spectacle lens made of polycarbonate resin was taken out. Table 1 shows the evaluation results of the obtained polycarbonate resin plus spectacle lenses.

[Embodiment 6] In Embodiment 4, in the compression step, the movable side lens mold is set to a lens center thickness of 3.7 mm.
Compress to an additional 100 μm (compression pushback amount)
Excess resin was returned to the injection cylinder. At this time, the compression amount adjusting rod and the die set are not in contact with each other. The resin pressure in the compression step was 18.6 MPa and the time applied was 0.39.
Seconds, the compression pressure is 102.56MPa and the time applied is 0.4
4 seconds. After that, in the pressure holding step, the resin pressure was set to 63.3MP.
a, The compression pressure was set to 64.1 MPa to balance. Thereafter, the resin pressure was increased from 63.3 MPa to 90 for 2 seconds.
It was gradually increased by 68.7 MPa at intervals of seconds.
The compression pressure was also gradually reduced from 64.1 MPa to 42.5 MPa at intervals of 2 to 60 seconds after balancing. The amount of compression fluctuated in the direction of decreasing the thickness of the optical molded product by 35 μm (the fluctuation width of the amount of compression) in the pressure holding step. After the cooling was completed, the plus spectacle lens made of polycarbonate resin was taken out. Table 1 shows the evaluation results of the obtained polycarbonate resin plus spectacle lenses.

[0068]

[Table 1]

[0069]

As described above, the detailed description and examples of the present invention,
As is clear from the comparative examples and the like, the injection compression molding method of the present invention can produce an optical molded product having extremely excellent transferability with a very simple mold structure and molding method. It is preferably used for injection compression molding.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a conventional injection compression molding method.

FIG. 2 is a conceptual diagram of the injection compression molding method of the present invention.

FIG. 3 is a diagram showing a relationship between a compression amount, a compression pressure, and a resin pressure.

FIG. 4 is a diagram showing the relationship between the compression amount, the compression pressure, and the resin pressure when the resin is compressed at a stretch by 20 to 200 μm beyond a specified thickness and pushed back to a predetermined thickness by adjusting the resin pressure and the compression pressure.

FIG. 5 is a diagram showing the relationship between the amount of compression, the compression pressure, and the resin pressure when the resin pressure is increased and the compression pressure is adjusted to decrease in multiple stages during the cooling process.

FIG. 6 is a schematic diagram of the positional relationship between eyes, a sample, and a fluorescent lamp during fluorescent lamp evaluation.

FIG. 7 is a schematic diagram of a structure of a strain inspection machine and a positional relationship of a sample.

FIG. 8 is a schematic view of a lens in which a weld line has occurred.

[Explanation of symbols]

 1. 1. Fixed side mirror surface Movable mirror surface 3. Cavity 4. 4. Compression amount adjustment rod 5. Fixed side die set 6. Space with width equal to compression amount Ejector plate 8. Pedestal 9. Compression plate 10. Compressive force 11. Reaction force 12. Magnet scale 13. Resin pressure 14. Compression amount 15. Compression pressure 16. Resin pressure 17. 17. Time of compression pressure in compression step 18. Time of resin pressure in compression step Compression process time 20. 21. Resin pressure in compression process Compression pressure in compression step 22. 23. Resin pressure in pressure holding process Compression pressure in the pressure holding process 24. 25. Fluctuation width of the compression amount after compression to a predetermined thickness Compression pushback amount 26. Pushing back step 27. Resin pressure multi-stage control unit 28. Injection pressure multi-stage control unit 29. 30. Positional relationship between eye and sample in fluorescent lamp evaluation Fluorescent light 31. Polarization plates whose polarization planes are orthogonal to each other 32. Sample (optical molded product) 33. Frosted glass 34. Fluorescent light 35. Sample (minus lens) 36. Weld line length 37. Packing time

Claims (5)

[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. The plastic resin is injected through an injection cylinder, (3) the enlarged cavity is then compressed to a specified thickness of the molded article or 200 μm less than the thickness, (4) the resin pressure in the injection cylinder and the compression pressure in the cavity. Is adjusted or varied so that the variation width does not exceed 100 μm from the prescribed thickness of the molded article so that the prescribed thickness of the molded article is finally obtained. Injection of an optical molded product characterized by holding until a target molded product is formed, and then (6) taking out the obtained molded product from the cavity. Shrinkage molding method. 2. In the step (3), the enlarged cavity is set to have a thickness of 20 to 180 μm more than a specified thickness of a molded article.
The injection compression molding method for an optical molded product according to claim 1, wherein the molding is performed to a small thickness. 3. In the step (4), the resin pressure in the injection cylinder and the compression pressure in the cavity are varied more than the specified thickness of the molded product so that the final thickness of the molded product becomes the specified thickness. The injection compression molding method for an optical molded product according to claim 1 or 2, wherein the method is varied within a range not exceeding 100 µm. 4. The optical molded product is a lens.
The injection compression molding method for an optical molded product according to any one of the above. 5. The injection compression molding method for an optical molded product according to claim 1, wherein the optical molded product is a spectacle lens made of polycarbonate.