JPH0693043B2 - Aspherical lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a base material among aspherical lenses constituting an optical system such as a camera for photography, a video camera, a microscope, a telescope or an optical disc pickup part. The present invention relates to an aspherical lens having an ultraviolet curable resin layer provided in a desired shape on the surface of a glass lens.

[Conventional technology]

Conventionally, there are many examples in which an ultraviolet curable resin is used for the resin layer of the aspherical lens as described above, but the conventional ultraviolet curable resin composition has good heat resistance after curing, moisture resistance and hardness. It has been impossible to achieve both of the above and the improvement of the shape accuracy at the time of curing and molding.

For example, among the photo-curable acrylate resins that have been used in the past, multifunctional resins have good light transmittance and hardness as lens materials, and also have high temperature and high humidity environment characteristics and good light resistance. However, there is a problem that the curing shrinkage rate is large and it is difficult to obtain shape accuracy.

Further, the recently developed UV-curable epoxy resin has a shrinkage rate of about 3%, which is smaller than the shrinkage rate of the conventional acrylate resin of about 8 to 9%, so that the desired shape accuracy can be easily obtained. . However, since photocurable epoxy resins use acid catalysts for polymerization initiation, etc., they have poor high-temperature and high-humidity environment resistance characteristics, and there is also a problem with the light resistance that is thought to be due to the unique coloring of epoxy. Yes, it was difficult to put into practical use.

There is known a lens provided with a resin layer having a two-layer structure in order to solve the above problems of the resin itself (Japanese Patent Laid-Open No. 60-5).
6544). This is because the shrinkage rate is relatively small and the shape accuracy is easy to obtain, but the hardness is low and it easily absorbs moisture. Therefore, the shrinkage rate is large but the high temperature resistance is high on the UV-curable acrylate resin layer, which has poor high temperature and high humidity environment characteristics. It is a lens provided with a thin layer of a multifunctional UV-curable acrylate resin having good wet environment characteristics and high hardness. This lens is excellent because it has the characteristics of each layer, but in order to manufacture it, the process of ultraviolet curing must be performed twice, the production equipment increases, the process becomes long and space is required, and it takes time. Since there are problems such as this and it leads to an increase in cost, it can be applied only to products in large lots and its range of practical application is narrow.

Further, in order to solve the above-mentioned problems of the resin itself, a molding method of applying pressure during curing is known.
This method is a method of pressing in a direction in which the distance between the base lens and the mold is narrowed when the resin composition made of a polyfunctional acrylate is cured. When this method is used, the shape accuracy of the resin to be molded is improved, but since it is not very effective at low pressure, it is necessary to apply a certain amount of pressure. As a result, the base material lens may be cracked during the process, and there is a problem that it can be used only for a lens made of a material having high strength or a thick lens.

The present invention has been made in view of the above problems, the purpose of the hardness of the ultraviolet effect type acrylate resin, high temperature and high humidity environment resistance, good light transmittance, light resistance, etc. Another object of the present invention is to provide an aspherical lens provided with a surface layer having a smaller curing shrinkage ratio without impairing the necessary physical properties. Another object of the present invention is to provide an aspherical lens having a single-layer surface layer (ultraviolet ray curable resin layer) and capable of providing excellent shape accuracy without pressing.

[Means for solving problems]

The above object of the present invention is to provide an aspherical lens in which an ultraviolet curable resin layer is provided in a desired shape on the surface of a glass lens as a base material, wherein the ultraviolet curable resin layer comprises (A) a polybasic acid and a polyhydric alcohol. A polyester oligomer obtained by the reaction with a diisocyanate and a (2) to 4 functional urethane-modified polyester (meth) acrylate obtained by reacting a (meth) acrylate having a hydroxyl group in the molecule, and (B) a trifunctional (meth) acrylate And (C) a monofunctional (meth) acrylate and (D) a photopolymerization initiator.

FIG. 1 shows the structure of the aspherical lens of the present invention.

The aspherical lens of the present invention comprises a base material 1 and an ultraviolet curable resin layer 2 laminated on the base material 1.

The base material is an inexpensive lens prepared by polishing the surface of ordinary optical glass. The ultraviolet curable resin layer 2 is thinner than the base material, usually has an average thickness of 10 to 300 μm, and has an aspherical shape rotationally symmetric with respect to the optical axis.

The lens of the present invention has a base material lens surface on which an aspherical surface is formed by pouring a certain amount of an ultraviolet-curable monomer liquid into an aspherical mold having a transfer layer opposite to a desired aspherical shape. Is fixed toward the surface of the mold so as to keep a constant distance from the mold, ultraviolet rays are irradiated from the lens side, the monomer is polymerized and cured without pressurization, and then the mold is peeled off.

The aspherical lens of the present invention is not limited to the one in which the resin layer is provided on the convex side of the base material as shown in FIG. 1, and as a modified example, as shown in FIG. 2, the resin layer is provided on the concave side of the base material lens. When provided, or as shown in FIG. 3, a resin layer may be provided on both surfaces of the base material lens. Further, in order to improve the adhesion between the resin and the glass, as shown in FIG. 5, a silane coupling material or the like which is usually used for improving the adhesive strength may be applied to the glass surface before the resin layer is provided. Also, after providing the resin layer,
As shown in FIG. 6, one or more layers may be provided on the resin layer with a moisture-proof protective layer and an anti-reflection vapor deposition film.

The present invention is intended for an aspherical lens, but it is also applicable to a Funnel lens, a focusing plate of a camera, and a mountain-shaped repeating shape as seen in a beam splitter element (Fig. 4). is there.

Component (A), component (B), component (C), (D) forming the ultraviolet curable resin layer 2 used in the aspherical lens of the present invention.
The components will be described below.

The component (A) has a main chain skeleton of a polyester oligomer composed of a polyhydric alcohol and a polybasic acid, and the polyester oligomer is at least a dihydric or tetrahydric alcohol or a dihydric alcohol.
.About.4 basic acids were used and synthesized. (A)
The component has a hydroxyl group at the end of the main chain and side chain of this polyester oligomer, an isocyanato group at one end of the diisocyanate is bonded, and at the isocyanato group at the other end of the diisocyanate has a hydroxyl group in the molecule (meth). It is a 2- to 4-functional urethane-modified polyester (meth) acrylate in which an acrylate is bound.

Examples of the tetrabasic acid include pyromellitic dianhydride, 2,3,3 ′,
4′-biphenyltetracarboxylic dianhydride, benzophenonetetracarboxylic dianhydride, bis (3,4-dicarboxylicoxyphenyl) methane dianhydride, etc. are used as the tribasic acid. Tribasic acid such as trimellitic anhydride; pyromellitic anhydride, 2,3,3 ', 4'-biphenyltetracarboxylic dianhydride, benzophenonetetracarboxylic dianhydride, bis (3.4-dicarboxyphenyl) methane A tribasic acid obtained by partially esterifying a tetrabasic acid such as dianhydride is used.

As the dibasic acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid (anhydrous), adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic anhydride,
Hexahydrophthalic anhydride, hymic acid anhydride, maleic anhydride, fumaric acid, itaconic acid and the like are used.

Examples of the tri- or tetrahydric alcohol include glycerin,
Trimethylolmethane, trimethylolethane, trimethylolpropane, pentaerythritol monoariether, pentaerythritol, etc. are used.

As the dihydric alcohol, ethylene glycol, propylene glycol, neopentyl glycol, diethylene glycol, dipropylene glycol, hydrogenated bisphenol A, 2,2'-di (4-hydroxypropoxyphenyl) propane, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, trimethylene glycol, triethylene glycol, pentaerythritol diallyl ether and the like are used.

As the diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, hydrogenated xylylene diisocyanate and the like are used.

Examples of the (meth) acrylate having a hydroxyl group in the molecule include 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, glycerin monoacrylate. , Glycerin diacrylate, etc. are used.

The component (A) is obtained by subjecting a polyhydric alcohol and a polybasic acid to a condensation reaction to obtain a polyester oligomer, followed by an addition reaction with a diisocyanate and then an addition reaction with a (meth) acrylate.

As the component (A), other general formula (R is hydrogen or a methyl group, R 'is -COOC _n H _2n - is (n 1 to 8 integer)) represented by, it is also possible to use isocyanates having an unsaturated group, in this case, A urethane-modified polyester (meth) acrylate can be obtained by reacting the hydroxyl groups of the main chain and the terminal portions of the side chains of the polyester oligomer with an isocyanato group. Examples of the isocyanates include 2-isocyanate methyl (meth) acrylate, 2-isocyanate ethyl (meth) acrylate, 2-isocyanate propyl (meth) acrylate, 2-isocyanate octyl (meth) acrylate, P-isopropenyl-α, α-dimethylbenzyl isocyanate, m-isopropenyl-
Examples include α, α-dimethylbenzyl isocyanate, P-ethylenyl-α, α-dimethylbenzyl isocyanate, m-ethylenyl-α, α-dimethylbenzyl isocyanate and the like.

As the trifunctional (meth) acrylate of the component (B),
Trimethylolpropane tri (meth) acrylate, tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate, tris (hydroxypropyl)
Examples include isocyanurate tri (meth) acrylate and the like.

As the monofunctional (meth) acrylate of the component (C),
For example, methyl (meth) acrylate, ethyl (meth) acrylate, cyclohexyl (meth) acrylate, dicyclopentyl (meth) acrylate, isobornyl (meth) acrylate, boronyl (meth) acrylate, phenyl (meth) acrylate, halogen-substituted phenyl (meth) acrylate. Examples thereof include acrylate, benzyl (meth) acrylate, α-naphthyl (meth) acrylate, β-naphthyl (meth) acrylate and dicyclopentyloxyethyl acrylate.

As the photopolymerization initiator of the component (D), benzophenone and hydroxybenzophenone methanesulfonate ester, 0-benzoyl-methylbenzoate, p-chlorobenzophenone, substituted derivatives of benzophenone such as p-dimethylaminebenzophenone, benzoin and benzoin allyl ether, Substituted derivatives of benzoin such as benzoin alkyl ether whose alkyl group is methyl, ethyl, isobutyl, isopropyl, etc., acetophenone and diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, benzyl dimethyl ketal, 2-hydroxy-2-methylpropiophenone , 1- (4-Isopropylphenyl) -2-hydroxy-2-methylpropiophenone and other substituted derivatives of acetophenone, benzyl, and 1-phenyl-1,2-propanedione 2-0 oxime compounds such as benzoyl oximes, one or more selected from, or the like is used.

The condensation reaction at the time of synthesizing the polyester oligomer of the components (A) and (B) may be carried out by heating reaction by a known method. For example, after charging the raw materials, the reaction is carried out at 150 to 250 ° C. under stirring to obtain an acid value. The reaction ends when the target value is reached. In the above, the use ratio of the polybasic acid and the polyhydric alcohol is preferably around 1: 2 in an equivalent ratio, but can be changed according to the molecular weight, the number of remaining alcohol groups, and the like.

In the ultraviolet curable resin layer of the aspherical lens of the present invention, the component (A) is a component for maintaining good environmental resistance such as humidity resistance, heat resistance and ultraviolet resistance, and is usually 10 to 90. %, Preferably 25-70% by weight. If it is less than 10% by weight, the environment resistance is poor, and if it exceeds 90% by weight, the viscosity is remarkably increased and the workability is deteriorated.

The component (B) is a component for improving physical properties such as hardness and heat distortion temperature, and is usually used in an amount of 10 to 70% by weight. This is because if the amount is 10% by weight or less, the improvement of the physical properties is not desired, and if the amount exceeds 70% by weight, the cured product becomes brittle, or the shrinkage rate at the time of curing becomes large and the processing accuracy deteriorates.

Further, the component (C) is a component for adjusting the balance of fluidity, viscosity, physical properties of the cured product, etc. at the time of molding the ultraviolet curable resin layer of the aspherical lens of the present invention, and is used in a desired blending amount. Usually has the above-mentioned (A) and (B)
It is about 20 to 400 parts by weight with respect to 100 parts by weight.

Further, the component (D) is a component having the ability to absorb irradiated light to initiate polymerization, and is used in a desired blending amount in view of curability, physical properties of a cured product, etc., but usually (A) to (C) above. 0.5 to 10 parts by weight with respect to the resin composition).

If necessary, known polymerization accelerators, polymerization inhibitors, mold release agents, surface smoothing agents, defoaming agents and the like can be added to the ultraviolet curable resin layer of the aspherical lens of the present invention.

A chemical lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, a carbon arc, a xeno lamp, etc. are used as a light source used for ultraviolet irradiation.

〔Example〕

Next, the present invention will be described more specifically by way of examples.

Production Example-1 96 g of trimetic anhydride, 228 g of propylene glycol, and 111 g of phthalic anhydride were charged into a four-necked flask equipped with a condenser, a nitrogen gas introduction tube, a thermometer, and a stirrer, and the mixture was heated and stirred under a nitrogen atmosphere.

After raising the temperature to 150 ° C, hold it for 2 hours, and then gradually raise the temperature to 2
The reaction proceeded at 00 ° C., and was terminated when the acid value became 5 or less. After cooling to room temperature, isophorone diisocyanate 27
After adding 7g, 174g of 2-hydroxyethyl acrylate and 0.17g of dibutyltin dilaurate and reacting for 3 hours while gently heating so that the temperature of the reaction system does not exceed 80 ° C, 100
The temperature was raised to 0 ° C over 1 hour, and the reaction was carried out for 3 hours to obtain a urethane-modified polyester acrylate (I).

Production Example-2 In the same manner as in Production Example-1, 54 g of trimethylolpropane,
Tetrahydrophthalic anhydride (182 g) and 1,3-butylene glycol (108 g) were charged, and the mixture was heated and stirred under a nitrogen atmosphere. After the temperature was raised to 150 ° C., the temperature was maintained for 2 hours, after which the temperature was gradually raised to proceed the reaction at 200 ° C., and the reaction was terminated when the acid value became 5 or less.

After cooling to room temperature, 222 g of isophorone diisocyanate, 156 g of hydroxypropyl acrylate and 0.14 g of dibutyltin dilaurate were added, and the reaction system was gently heated so that the temperature did not exceed 80 ° C for 3 hours, then 100 ° C for 1 hour. After heating, the reaction was carried out for 3 hours to obtain a urethane-modified polyester acrylate (II).

Aspherical lens physical property test Test Examples 1 to 6 The urethane-modified polyester acrylates obtained in the above Production Examples 1 and 2 were mixed with other components shown in Table 1 at a compounding ratio shown in the same table to obtain 6 types. (Compositions 1 and 2 of the resin layer according to the present invention and comparative compositions 1 to 4) were obtained.

With these compositions, φ = 40.5mm, R1 = 41.34mm convex, R2 = 2
03mm concave, center thickness = 11.33mm, base material spherical lens of material BK7
A spherical resin layer was provided on the convex surface side of R1 according to the above-described manufacturing method so that the center thickness was 150 μm and R = 41.49 mm, and 6 types of composite spherical lenses were obtained.

(1) Shape accuracy The surface shape of the composite spherical lens obtained as described above was observed by a Zygo interferometer, and the shape accuracy was obtained from the disturbance of the obtained interference fringes. The results are shown in Table 1.

(2) Curing shrinkage ratio Based on JISK-7112, measure the specific gravity before curing (liquid) and after curing (casting plate) using a pycnometer, and divide the difference in specific gravity by the specific gravity after curing. It was defined as the curing shrinkage rate.

(3) High-temperature and high-humidity environment characteristics The obtained lens was left in a high-temperature and high-humidity bath at 70 ° C and 85% RH for 500 hours, and the appearance before and after leaving, the microscopic observation (X200), and the shape accuracy were checked.

(4) Pencil hardness A scratch test was performed on the lens surface with a pencil of each hardness, and the highest hardness without scratches on the resin surface was taken as the pencil hardness.

In Comparative Compositions 1 to 4, the shape accuracy is ± 1.2 μm or more, and there is a change in appearance and a decrease in hardness when placed in a high temperature and high humidity environment. Shape accuracy of Compositions 1 and 2 of ± 0.6μ
It showed a favorable value of m or less, was sufficiently usable as an optical lens for photographing, and did not show resistance to high-temperature and high-humidity environment characteristics and hardness.

Example 1 A lens having the same shape as an aspherical lens used in a lens for a commercially available single-lens reflex camera was prepared using the composition 1 of the resin layer according to the present invention, and the shape was measured by a contact-type aspherical measuring machine. The measurement results are shown in FIG. When measured at n = 2,
The maximum error was within ± 0.5 μm, and it was confirmed that the aspherical shape was accurately formed by using this resin composition.

[Advantages of the Invention] As described above, the composite aspherical lens of the present invention has a high degree of shape accuracy without impairing various characteristics required for an optical lens such as high temperature and high humidity environment characteristics and hardness.・ Since the UV-curable resin layer has a single layer structure, no extra production equipment is needed, the production process is shortened, and the cost of descent is reduced, so small-lot production is possible. Since the resin layer has a small curing shrinkage and pressure is not required during curing, it can be used for lenses and thin-walled lenses that are easily broken when pressed, and the lens shape and material (refractive index) have a wide range. It has the effect of enabling optical design.

[Brief description of drawings]

FIG. 1 is a sectional view of an aspherical lens of the present invention.
FIG. 3, FIG. 5, FIG. 5 and FIG. 6 show another embodiment of the aspherical lens of the present invention, FIG. 4 shows a composite optical element having a repeating shape of a chevron, and FIG. It is a graph which shows the measurement result of the shape accuracy of a spherical lens. 1: Base glass substrate 1a: Composite optical element substrate 2: Aspherical resin layer 3: Resin layer with repeating chevron shape 4: Layer such as silane coupling material 5: Moisture-proof protective layer or antireflection film layer

Claims (1)

[Claims] 1. An aspherical lens having an ultraviolet curable resin layer formed in a desired shape on the surface of a glass lens as a base material,
The ultraviolet-curable resin layer is obtained by reacting (A) a polyester oligomer obtained by reacting a polybasic acid with a polyhydric alcohol with diisocyanate and (meth) acrylate having a hydroxyl group in the molecule. Polymerization and curing of a composition containing a tetrafunctional urethane-modified polyester (meth) acrylate, (B) trifunctional (meth) acrylate, (C) monofunctional (meth) acrylate, and (D) photopolymerization initiator by ultraviolet rays Is an aspherical lens.