JP2008216792A - Optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element which does not cause striae or clouding by photopolymerization of a polymerizable compound. <P>SOLUTION: The optical element is obtained by the photopolymerization of a polymerizable composition that contains a polymerizable compound and a photopolymerization initiator, wherein the shortest wavelength λ1 in the light absorption region of the polymerizable compound to be photopolymerized and the wavelength λ2 in the longest wavelength side in the light absorption region of the photopolymerization initiator have a relation of λ2-λ1≥40 nm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical element used in an optical system such as an imaging optical system such as a camera, a projection optical system such as a display device, an observation optical system such as an image display device, and particularly prevents striae and cloudiness during molding. In addition, the optical element has excellent light resistance.

Small optical elements such as modules for digital cameras and portable cameras are rapidly spreading. In pursuing miniaturization, not only the lens processing / molding technology but also the optical properties of the material itself are regarded as important.
If a material having a high refractive index is used, a lens having a small curvature radius can be produced. If a material having a low dispersion is used, a lens group for correcting chromatic aberration is not required. Thus, if there is a material with high refraction and low dispersion or an inexpensive material, it can contribute to miniaturization, weight reduction and cost reduction of the optical system.

  In recent years, optical elements have been formed by potting or pressing a transparent resin into a predetermined shape. However, when used outdoors, since the transparent resin is a synthetic resin, there are problems such as striae or discoloration due to ultraviolet rays or the like. Therefore, an ultraviolet absorber is added to improve the light resistance against ultraviolet rays.

The present invention solves that, depending on the shape of the optical element to be molded, UV rays from the light source do not reach the depth direction from the irradiation surface sufficiently, and streaks and white turbidity occur during molding due to uneven curing. To do.
In addition, when an ultraviolet absorber is blended with the transparent resin, the ultraviolet absorber absorbs the ultraviolet rays necessary for activating the photopolymerization initiator, so that striae and cloudiness caused by uneven curing are eliminated. It is a solution to prevent.

In the present invention, λ2−λ1 ≧ 40 nm between the wavelength λ1 on the shortest wavelength side of the light absorption region of the polymerizable compound to be photopolymerized and the wavelength λ2 on the longest wavelength side of the light absorption region of the photopolymerization initiator. An optical element obtained by photopolymerization of a polymerizable composition containing the polymerizable compound and a photopolymerization initiator having the relationship:
In addition, the light-absorbing region of the polymerizable compound contains an ultraviolet absorber in which the absorbance of the photopolymerization initiator in the light-absorbing region longer than the wavelength λ1 on the shortest wavelength side is larger than the absorbance of the ultraviolet absorber. Said optical element.
The present invention relates to the relationship between the wavelength on the shortest wavelength side of the light absorption region of the polymerizable compound to be photopolymerized as described above and the wavelength on the longest wavelength side of the light absorption region of the photopolymerization initiator, or further ultraviolet absorption. It has been found that an optical element free from white turbidity, striae, etc. can be produced by specifying the ultraviolet absorption characteristics, photopolymerization initiator and ultraviolet absorption characteristics of the agent.

When the wavelength λ2 on the longest wavelength side of the light absorption region of the photopolymerization initiator is larger than the wavelength λ3 on the longest wavelength side of the light absorption region of the ultraviolet absorber, the absorption of the photopolymerization initiator is In the above-described optical element, the region where the absorption is larger than the absorption is present in the region between λ3 and λ2.
When the wavelength λ2 on the longest wavelength side of the light absorption region of the photopolymerization initiator is smaller than the wavelength λ3 on the longest wavelength side of the light absorption region of the ultraviolet absorber, the absorption of the photopolymerization initiator is more than the absorption of the ultraviolet absorber. In the optical element, a region having a large absorption exists in a region between wavelengths λ1 and λ2 on the shortest wavelength side of the light absorption region of the polymerizable compound.

  The relationship between the wavelength of the shortest wavelength side of the light absorption region of the polymerizable compound to be photopolymerized and the wavelength of the longest wavelength side of the light absorption region of the photopolymerization initiator, or the ultraviolet absorption characteristics and photopolymerization of the ultraviolet absorber. By specifying the ultraviolet absorption characteristics of the initiator, it is possible to provide an optical element that does not cause white turbidity, striae or the like.

The present invention pays attention to the fact that striae and white turbidity generated in an optical element produced by photopolymerization are caused by non-uniform curing at the time of molding, and the light absorption characteristics of a photopolymerizable polymerizable compound and a photopolymerization initiator are predetermined. It has been found that a uniform curing reaction can be realized.
For curing by the photopolymerization reaction of the optical element of the present invention, a high pressure mercury lamp, a metal halide lamp, a xenon lamp or the like can be used as a light source. Further, by selecting the characteristics of the photopolymerization initiator, not only ultraviolet rays from 100 nm to 400 nm but also visible rays from 400 nm to 800 nm can be used.

In the photopolymerization reaction by light in the wavelength region as described above, when the light absorption region of the polymerizable compound to be photopolymerized and the start wavelength of the photopolymerization initiator overlap, the light absorbed by the polymerizable compound. When the amount of is increased, the polymerization reaction is less likely to occur, and even if cured by polymerization, non-uniform curing occurs, resulting in phenomena such as striae and white turbidity of the cured product.
In the present invention, between the wavelength λ1 on the shortest wavelength side of the light absorption region of the polymerizable compound to be photopolymerized and the wavelength λ2 on the longest wavelength side of the light absorption region of the photopolymerization initiator, λ2−λ1 ≧ It has been found that the use of the polymerizable compound having a relationship of 40 nm and a photopolymerization initiator can prevent striae and cloudiness as a result of the uniform polymerization reaction.

The light absorption of the polymerizable compound in the present invention was measured with a compound having a polymerizable functional group contained in the composition used for the production of the optical element by light of 300 nm to 800 nm with a measuring cell having an optical path length of 10 mm. The wavelength λ1 obtained from the light absorption curve and having the shortest wavelength side in the light absorption region of the polymerizable compound to be photopolymerized is specifically the shortest wavelength at which the transmittance is 1%.
When the polymerizable compound contained in the composition is one kind, the light absorption of the polymerizable compound can be measured as described above, but plural kinds of polymerizable compounds are contained. In this case, the light absorption of the polymerizable compound blended at a blending ratio equal to the blending ratio in the composition can be measured.

  In addition, the wavelength λ2 on the longest wavelength side of the light absorption region of the photopolymerization initiator is prepared by preparing a chloroform solution of the photopolymerization initiator having a concentration equal to the concentration of the photopolymerization initiator contained in the composition. It is obtained from a light absorption curve measured with light of 300 nm to 800 nm by a measuring cell having an optical path length of 1 cm, and is the longest wavelength among wavelengths at which absorption starts.

  In the present invention, when a predetermined relationship is established between the wavelength λ1 on the shortest wavelength side of the light absorption wave region of the photopolymerizable compound and the wavelength λ2 at which the photopolymerization initiator starts to absorb light, Even if the light irradiated for the polymerization is somewhat absorbed by the photopolymerizable compound, sufficient light is given to the photopolymerization initiator. It becomes possible to provide.

As the polymerizable compound that can be used in the production of the optical element, a compound that undergoes a photocuring reaction by photopolymerization in the presence of a photopolymerization initiator and has one or more reactive groups can be used.
Specific examples include acrylate, methacrylate, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth) acrylate, nonylphenyl ( (Meth) acrylate, 2-hydroxypropyl methacrylate, 2-ethylhexyl (meth) acrylate, dimethylol tricyclodecane dimethacrylate, isobornyl methacrylate, trimethylpropane tri (meth) acrylate, nonylphenyl (meth) acrylate, cyclohexyl (meth) Acrylate, bisphenol A di (meth) acrylate, polyethylene glycol di (meth) acrylate, 2-methacryloyloxyethylisocinane , Mention may be made of urethane acrylate, and epoxy acrylate.
These polymerizable compounds may be used singly or as a mixture of a plurality of types, and are not limited to monomers but may be oligomers thereof. In the present invention, (meth) acrylate means one containing at least one of acrylate and methacrylate.

As photopolymerization initiators, benzophenone, 1-hydroxycyclohexyl phenyl ketone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenyl-propane Examples thereof include -1-one, 2,2-dimethoxy-1, 2-diphenylethane-1-one, and the like.
When forming an optical element, if the amount of the photopolymerization initiator is large, molding abnormalities such as sink marks are likely to occur, and therefore the amount is preferably 2% by mass or less.

Moreover, you may mix | blend a ultraviolet absorber with the composition for formation of the optical element of this invention. The ultraviolet absorber has a region where the absorbance of the photopolymerization initiator in the light absorption region on the longer wavelength side than the wavelength λ1 on the shortest wavelength side of the light absorption region of the polymerizable compound is larger than the absorbance of the ultraviolet absorber. It is necessary to do. Here, the absorbance of the ultraviolet absorber is determined by preparing a chloroform solution of the ultraviolet absorber having a concentration equal to the concentration of the ultraviolet absorber contained in the composition, and by measuring 300 nm to 800 nm with a measuring cell having an optical path length of 10 mm. It is obtained from the measured light absorption curve.
When the absorbance of the UV absorber is greater than the absorption of the photopolymerization initiator, the light energy that is irradiated from the light source and contributes to the photopolymerization initiator is reduced by the UV absorber, and the polymerization reaction hardly occurs. It causes phenomena such as reason and turbidity.

  Usable ultraviolet absorbers that can be used include those that satisfy the relationship described above in relation to the photopolymerizable compound used and the light absorption wavelength of the photopolymerization initiator. Specifically, salicylic acid ester type compounds such as phenyl salicylate, p-tertiary butylphenyl salicylate, p-octylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-acetoxyethoxybenzophenone, 2-hydroxy- 4-methoxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2,2′-dihydroxy Benzophenone series such as -4,4'-dimethoxy-5,5'-disulfobenzophenone disodium salt, 2 (2'-hydroxy-5'-methylphenyl) benzotriazole, 2 (2'-hydroxy- 3 ', 5'-Jitasi Libutylphenyl) benzotriazole, 2 (2′-hydroxy-3′-tertiarybutyl-5′-methylphenyl) -5-chlorobenzotriazole, 2 (2′-hydroxy-3 ′, 5′-ditertiarybutyl Phenyl) -5-chlorobenzotriazole, 2 (2′-hydroxy-3 ′, 5′-ditertiary amylphenyl) benzotriazole, 2 (2′-hydroxy-5′-tertiarybutylphenyl) benzotriazole, 2 ( Benzotriazoles such as 2′-hydroxy-5′-tertiary octylphenyl) benzotriazole, benzoates such as 2 ′, 4′-ditertiarybutylphenyl-3,5-ditertiarybutyl-4-hydroxybenzoate , Ethyl-2-cyano-3,3-diphe Those cyanoacrylate such as Le acrylate, p- aminobenzoic acid butyl-like amino benzoic acid and the like. One or more of these can be mixed and used.

The polymerizable compound is an optical element in which dimethylol-tricyclodecanediacrylate is used, and the photopolymerization initiator is an equivalent mixture of 1-hydroxy-cyclohexyl-phenyl-ketone and benzophenone.
In the optical element, the polymerizable compound contains N-allylcarbazole in addition to dimethylol-tricyclodecane diacrylate.
The polymerizable compound is an ethylene oxide adduct dimethacrylate of bisphenol A, and the photopolymerization initiator is bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide and 2-hydroxy-2-methyl. The optical element as described above, wherein an equal amount mixture of -1-phenyl-propan-1-one and the ultraviolet absorber is 2- (2-hydroxy-5-methylphenyl) -2H-benzoate.
The polymerizable compound is dimethylol-tricyclodecane diacrylate and N-allylcarbazole, the photopolymerization initiator is an equivalent mixture of 1-hydroxy-cyclohexyl-phenyl-ketone and benzophenone, and the ultraviolet absorber is 4- The optical element is dodecyloxy-2-hydroxybenzophenone.
Hereinafter, the present invention will be described with reference to examples and comparative examples.

Example 1
10 g of dimethylol-tricyclodecane diacrylate (DCP-A manufactured by Kyoeisha Chemical Co., Ltd.) as a polymerizable compound to be photopolymerized, and an equivalent mixture of 1-hydroxy-cyclohexyl-phenyl-ketone and benzophenone (Ciba Specialty) as a photopolymerization initiator Chemicals Irgacure 500) 0.2 g was mixed and dissolved at 50 ° C. and vacuum degassing was performed.

Next, 120 mg is applied to a glass substrate coated with a silicone mold release material, and a mold coated with a silicone mold release material having a diameter of 12 mm is set so that the distance from the glass substrate is 1 mm from above, and the high pressure is applied from the substrate side. Curing was performed by irradiating 100 mW / cm ² at a wavelength of 365 nm with a mercury lamp for 100 seconds, and the cured product was peeled off from the mold and the glass substrate to obtain an optical element having a diameter of 12 mm and a thickness of 1 mm.

Measurement of Light Absorption Characteristics of Polymerizable Compound As a polymerizable compound to be photopolymerized, dimethylol-tricyclodecane diacrylate (DCP-A manufactured by Kyoeisha Chemical Co., Ltd.) was used with a spectrophotometer (U4100 manufactured by Hitachi High-Technologies), and the optical path length of 10 mm The light absorption characteristics were measured, and the results are shown in FIG. The shortest wavelength in the light absorption region: λ1 was 305 nm.

Measurement of Light Absorption Characteristics of Photopolymerization Initiator A 2.0 mass% chloroform solution of 1-hydroxy-cyclohexyl-phenyl-ketone and benzophenone equivalent mixture (Irgacure 500 manufactured by Ciba Specialty Chemicals) used as a photopolymerization initiator. The light absorption characteristics of the sample were measured with a spectrophotometer (U4100, manufactured by Hitachi High-Technologies Corporation) with an optical path length of 10 mm, and the results are shown in FIG. The longest wavelength of the light absorption region: λ2 was 390 nm.
From the above measurement results, λ2−λ1 = 85 nm.

Evaluation of Optical Element When the striae and white turbidity of the obtained optical element were visually observed, no striae or white turbidity occurred.

Example 2
An optical element was produced and evaluated in the same manner as in Example 1 except that 0.75 g of N-allylcarbazole (manufactured by Nippon Distilled Industries) was added in addition to the polymerizable compound to be photopolymerized in Example 1. In the same manner as in Example 1, the light absorption characteristics of the polymerizable composition that photopolymerized were measured. The measurement result of the light absorption characteristic is shown in FIG. The shortest wavelength of the light absorption region: λ1 was 350 nm. The longest wavelength of the light absorption region of the photopolymerization initiator: λ2 was 390 nm.
From the above measurement results, λ2−λ1 = 40 nm.
No striae or white turbidity occurred in the obtained optical element.

Example 3
Bisphenol A ethylene oxide adduct dimethacrylate (BP-6EM manufactured by Kyoeisha Chemical Co., Ltd.) 10 g as a photopolymerizable polymerizable compound, and bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl- as a photosensitive polymerization initiator 0.1 g of an equivalent mixture of pentylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Irgacure 1700, manufactured by Ciba Specialty Chemicals), 2- (2-hydroxy-5 as an ultraviolet absorber) -Methylphenyl) -2H-benzoate (SEPRORB701 manufactured by Cypro Kasei) 0.0025 g was mixed and dissolved at 50 ° C., and after vacuum degassing, an optical element was produced in the same manner as in Example 1.

While producing and evaluating an optical element similarly to Example 1, the light absorption characteristic of the polymerizable composition photopolymerized similarly to Example 1 and the light absorption characteristic of the photopolymerization initiator were measured. The measurement results of the light absorption characteristics are shown in FIG. The shortest wavelength of the light absorption region: λ1 was 305 nm. The longest wavelength of the light absorption region of the photopolymerization initiator: λ2 was 445 nm.
From the above measurement results, λ2−λ1 = 140 nm.

Further, the light absorption characteristics of a chloroform solution having a UV absorber concentration of 0.025% by mass were measured in the same manner, and the results are shown in FIG. The absorption start wavelength, that is, the wavelength λ3 on the longest wavelength side of the light absorption region was 400 nm. In the region from 445 nm to 390 nm, the absorbance of the photopolymerization initiator was larger than that of the ultraviolet absorber.
No striae or white turbidity occurred in the obtained optical element.

Example 4
10 g of the same components as in Example 1 as a polymerizable compound to be photopolymerized, an equivalent mixture of 1-hydroxy-cyclohexyl-phenyl-ketone and benzophenone (Irgacure 500 manufactured by Ciba Specialty Chemicals), and 2- (2- Hydroxy-5-methylphenyl) -2H-benzoate (SEPRORB 701 manufactured by Cypro Kasei) 0.0025 g was mixed and dissolved at 50 ° C., vacuum degassing was performed, and then an optical element was produced in the same manner as in Example 1.

While producing and evaluating an optical element like Example 1, the light absorption characteristic of the polymeric composition photopolymerized and the light absorption characteristic of a photoinitiator were measured similarly to Example 1. FIG. The measurement results of the light absorption characteristics are shown in FIG. The shortest wavelength of the light absorption region: λ1 was 305 nm. The longest wavelength of the light absorption region of the photopolymerization initiator: λ2 was 390 nm.
From the above measurement results, λ2−λ1 = 85 nm.

Further, the light absorption characteristics of a chloroform solution having a UV absorber concentration of 0.025% by mass were similarly measured, and the results are shown in FIG. The absorption start wavelength, that is, the wavelength λ3 on the longest wavelength side of the light absorption region was 400 nm. Further, in the region from 385 nm to 360 nm, the absorbance of the photopolymerization initiator was larger than that of the ultraviolet absorber.
No striae or white turbidity occurred in the obtained optical element.

Comparative Example 1
An optical element was prepared and evaluated in the same manner as in Example 1 except that 1 g of N-allylcarbazole was added in addition to the polymerizable compound to be photopolymerized in Example 1, and photopolymerized in the same manner as in Example 1. The light absorption property of the polymerizable composition was measured. The measurement results of the light absorption characteristics are shown in FIG. The shortest wavelength: λ1 of the light absorption region was 360 nm, and the longest wavelength: λ2 of the light absorption region of the photopolymerization initiator was 390 nm.
From the above measurement results, λ2−λ1 = 30 nm.
In the obtained optical element, striae and white turbidity occurred.

  The optical element obtained by adding a photopolymerization initiator to the photopolymerizable polymerizable compound of the present invention and polymerizing the photopolymerizable compound, the photopolymerization initiator, and the light absorbing region of the ultraviolet absorber has a predetermined value. As a result, the curing reaction can proceed uniformly, no striae or white turbidity occurs during the polymerization, and it is possible to prevent deterioration due to coloring by sunlight and to provide an optical element with excellent characteristics. Become.

FIG. 1 is a diagram for explaining the light absorption region of each component of the composition for producing an optical element of one example of the present invention. FIG. 2 is a diagram for explaining the light absorption regions of the respective components of the composition for producing an optical element of another example of the present invention. FIG. 3 is a diagram for explaining the light absorption regions of the respective components of the composition for manufacturing an optical element according to another embodiment of the present invention. FIG. 4 is a diagram for explaining the light absorption regions of the respective components of the composition for producing an optical element of another example of the present invention. FIG. 5 is a diagram for explaining the light absorption regions of the respective components of the composition for manufacturing an optical element of a comparative example of the present invention.

Claims (4)

The polymerization having a relationship of λ2−λ1 ≧ 40 nm between the shortest wavelength λ1 of the light absorption region of the polymerizable compound to be photopolymerized and the wavelength λ2 of the longest wavelength side of the light absorption region of the photopolymerization initiator. An optical element obtained by photopolymerization of a polymerizable composition containing a polymerizable compound and a photopolymerization initiator. The absorbance of the photopolymerization initiator at a concentration in the polymerizable composition in the light absorption region longer than the wavelength λ1 on the shortest wavelength side of the light absorption region of the polymerizable compound is 2. The optical element according to claim 1, further comprising an ultraviolet absorber having a concentration higher than the absorbance of the ultraviolet absorber. When the wavelength λ2 on the longest wavelength side of the light absorption region of the photopolymerization initiator is larger than the wavelength λ3 on the longest wavelength side of the light absorption region of the ultraviolet absorber, the absorption of the photopolymerization initiator is absorbed more than the ultraviolet absorber. The optical element according to claim 2, wherein a region having a large value exists in a region between λ3 and λ2. When the wavelength λ2 on the longest wavelength side of the light absorption region of the photopolymerization initiator is smaller than the wavelength λ3 on the longest wavelength side of the light absorption region of the ultraviolet absorber, the absorption of the photopolymerization initiator is more than that of the ultraviolet absorber. 3. The optical element according to claim 2, wherein the region having a large absorption exists in a region between wavelengths [lambda] 1 and [lambda] 2 on the shortest wavelength side of the light absorption region of the polymerizable compound.

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