JPH0784123A - Optical filter - Google Patents

Abstract

PURPOSE:To provide an optical filter made of a synthetic resin having high absorptivity of light in a near infrared region, small specific gravity, and good moisture resistance which can be easily subjected to such as forming, machining and polishing. CONSTITUTION:The base body of the filter consists of a copolymer obtd. by copolymn. of monomers containing phosphate groups expressed by formula and monomers copolymerizable with these monomers, and an ioninc metal component essentially comprising copper ion bonded to the phosphate groups of the copolymer. The surface of the filter base body is coated with a coating layer comprising a polyfunctional acryl resin.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an optical filter,
More specifically, the present invention relates to an optical filter made of synthetic resin, which has a high light absorption rate in the near infrared region, has a light absorption characteristic suitable for luminosity correction, and has high moisture resistance.

[0002]

2. Description of the Related Art Conventionally, a glass optical filter in which copper ion is contained in a special phosphoric acid glass has been used as a photometric filter and a visual sensitivity correction filter of a camera. However, these glass optical filters have a large specific gravity, have low moisture resistance and are likely to cause devitrification over time, and in manufacturing the optical filter, molding, cutting, polishing, etc. It has many problems such as difficult processing. Therefore, the appearance of an optical filter having a small specific gravity, easy processing, and excellent moisture resistance has been strongly desired.

[0003]

SUMMARY OF THE INVENTION The present invention has been made under these circumstances, and its purpose is to have a high absorptance of light in the near infrared region, a small specific gravity,
An object of the present invention is to provide an optical filter made of synthetic resin, which is easy to process such as cutting and polishing and has high moisture resistance.

[0004]

The optical filter of the present invention is a copolymer obtained by copolymerizing a phosphoric acid group-containing monomer represented by the following chemical formula 1 and a monomer copolymerizable therewith. And a coating layer made of a polyfunctional acrylic resin is formed on the surface of the filter substrate containing the ionic metal component mainly composed of copper ions, which is bonded to the phosphate group of the copolymer. It is characterized by

[0005]

[Chemical 2]

In the optical filter of the present invention, the coat layer preferably has a thickness of 0.3 to 20 μm.

[0007]

In the optical filter of the present invention, the copolymer constituting the filter substrate constituting the optical filter contains a phosphate group and a copper ion in its chemical structure,
These interactions efficiently absorb light in the near-infrared region, and moreover, a coat layer made of a polyfunctional acrylic resin is formed on the surface of this filter substrate, and the non-coating layer Since the moisture permeability is high, the filter substrate does not absorb moisture, and as a result, devitrification does not occur over time.

The present invention will be described in detail below. The optical filter of the present invention comprises a monomer represented by the above chemical formula 2 (hereinafter, also referred to as “specific phosphoric acid group-containing monomer”) and a monomer copolymerizable therewith (hereinafter, “copolymer”). Polymerizable monomer "
Also called. ) In a copolymer of mixed monomers consisting of
An optical filter made of synthetic resin, comprising a filter substrate containing an ionic metal component mainly containing copper ions, and a coating layer made of a polyfunctional acrylic resin formed on the surface of the filter substrate.

A specific phosphoric acid group-containing monomer is used as an essential component in the mixed monomer for obtaining the copolymer constituting the filter substrate. As is clear from the above chemical formula 2, this specific phosphoric acid group-containing monomer has a phosphoric acid group in the molecular structure that forms a coordinate bond with an ionic metal component such as copper ion. Further, the specific phosphoric acid group-containing monomer has, in its molecular structure, an acryloyloxy group or a methacryloyloxy group, which is a radically polymerizable functional group, through an ethylene oxide group, and thus the specific phosphoric acid group The group-containing monomer is extremely rich in copolymerizability and forms a copolymer with various monomers.

In the above chemical formula 2 representing the molecular structure of a specific phosphoric acid group-containing monomer, R is an acryloyloxy group (when X is a hydrogen atom) or a methacryloyloxy group (where X is a methyl group) bonded to an ethylene oxide group. In the case of a group). Here, the repeating number m of the ethylene oxide group is an integer of 0 to 5. When the value of m exceeds 5, the hardness of the obtained copolymer is significantly reduced, and the practicality as an optical filter becomes insufficient.

The number n of hydroxyl groups is 1 or 2 depending on the molding method of the filter substrate and the purpose of use of the optical filter.
Either value of When the value of n is 2, that is, the specific phosphoric acid group-containing monomer in which the number of radical-polymerizable functional groups bonded to the phosphorus atom is 1, is bound to an ionic metal component such as copper ion. It has a great effect. On the other hand, the specific phosphoric acid group-containing monomer in which the value of n is 1, that is, the specific phosphoric acid group-containing monomer in which the number of the functional groups is 2, is crosslinkable. Therefore, when the filter substrate is manufactured by an injection molding method or an extrusion molding method which is a general molding process for thermoplastic resins, a specific phosphoric acid group-containing monomer having a value of n of 2 is used. It is preferable. However, the method for molding the filter substrate is not limited to these.

As described above, the value of n can be selected according to the molding method of the filter substrate, the performance of the optical filter and the purpose of use. In practice, however, a specific phosphate group having a value of n of 1 is selected. It is preferable to use the contained monomer and a specific phosphoric acid group-containing monomer having a value of n of 2, in combination,
A specific phosphoric acid group-containing monomer in which the value of n is 1 and a specific phosphoric acid group-containing monomer in which the value of n is 2 are in a molar ratio of 1:
When it is used in a ratio of 5 to 5: 1, the solubility of a metal compound containing a copper compound, which will be described later, as a main component in the mixed monomer is improved, which is preferable.

The mixed monomer contains a copolymerizable monomer together with the specific phosphoric acid group-containing monomer. By copolymerizing a specific phosphoric acid group-containing monomer with a copolymerizable monomer, the resulting copolymer has a light absorption property due to an interaction with an ionic metal component described below, and an optical filter. Satisfies the hardness requirements required for
With such a copolymer, it is possible to obtain a filter substrate having excellent shape retention.

Such a copolymerizable monomer is (1) uniformly dissolved and mixed with a specific phosphoric acid group-containing monomer,
There is no particular limitation as long as it satisfies (2) good radical copolymerizability with a specific phosphoric acid group-containing monomer and (3) an optically transparent copolymer can be obtained. Not something.

Specific examples of these copolymerizable monomers include an alkyl group having 1 to 8 carbon atoms such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate and n-propyl methacrylate. Modified alkyl acrylate obtained by substituting an alkyl group such as certain lower alkyl acrylate or lower alkyl methacrylate, glycidyl acrylate, glycidyl methacrylate, and 2-hydroxybutyl methacrylate with a glycidyl group or a hydroxyl group, modified alkyl methacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate. ,
Diethylene glycol diacrylate, diethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,4-
Butanediol dimethacrylate, 2,2-bis [4-
Acryloxyethoxyphenyl] propane, 2,2-bis [4- (methacryloxyethoxy) phenyl] propane, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate. Examples thereof include polyfunctional acrylates or polyfunctional methacrylates, carboxylic acids such as acrylic acid and methacrylic acid, and aromatic vinyl compounds such as styrene, α-methylstyrene, halogenated styrene, methoxystyrene, and divinylbenzene. These compounds alone
Alternatively, two or more kinds may be mixed to form the copolymerizable monomer.

In the mixed monomer for obtaining the copolymer constituting the filter substrate, the ratio of the specific phosphoric acid group-containing monomer and the copolymerizable monomer is such that the specific phosphoric acid group-containing monomer is contained. Weight ratio of monomer: copolymerizable monomer is 3:97 to 60:40.
It is preferably in the range of, and more preferably 20: 8.
It is 0 to 50:50. When the proportion of the specific phosphoric acid group-containing monomer is less than 3% by weight, the light absorption characteristics suitable as an optical filter are hardly exhibited. On the other hand, when the proportion of the specific phosphoric acid group-containing monomer exceeds 60% by weight, the copolymer obtained has excessive flexibility, and tends to be flexible which cannot satisfy the required hardness condition.

The copolymer constituting the filter substrate is obtained by radical polymerization of a mixed monomer comprising a specific phosphoric acid group-containing monomer and a copolymerizable monomer. The radical polymerization method is not particularly limited, and a bulk (cast) polymerization method using an ordinary radical polymerization initiator,
Known methods such as suspension polymerization method, emulsion polymerization method and solution polymerization method can be used.

The filter substrate constituting the optical filter of the present invention comprises the above copolymer containing an ionic metal component mainly containing copper ions. The ionic metal component mainly composed of this copper ion is held in the copolymer by being coordinately bonded with the phosphate group contained in the copolymer as a ligand, and the phosphate group Has the effect of efficiently absorbing light in the near infrared region. Therefore, the copolymer containing an ionic metal component containing copper ions as a main component exhibits a light absorption characteristic in the near infrared region.

Such an ionic metal component containing copper ions as a main component is prepared by adding a metal compound containing a copper compound as a main component to the above copolymer or mixed monomer.
It can be contained in the copolymer. As used herein, the term "mainly containing a copper compound" means that the proportion of copper ions in all the ionic metal components contained in the metal compound is 8%.
It means 0% by weight or more. Specifically, it is a compound in which a compound composed of divalent copper ions and a compound composed of another metal ion are contained under the conditions satisfying the above ratio. When the proportion of copper ions is less than 80% by weight, the obtained filter substrate has low absorption of light in the near infrared region.

Various copper compounds are used as the above-mentioned metal compound, and specific examples thereof are as follows.
Examples thereof include anhydrides and hydrates such as copper acetate, copper chloride, copper formate, copper stearate, copper benzoate, copper ethylacetoacetate, copper pyrophosphate, copper naphthenate, and copper citrate. The copper compound is not limited to these.

Further, as the compound with other metal ions constituting the above metal compound, a compound containing sodium, potassium, calcium, iron, manganese, cobalt, magnesium, nickel or the like as a metal ion component is used.

In the present invention, the metal compound containing a copper compound as a main component is used in a proportion of copolymer or mixed monomer 1.
The amount is preferably 0.1 to 50 parts by weight, more preferably 0.1 to 30 parts by weight, relative to 00 parts by weight. When the ratio of the metal compound used is less than 0.1 part by weight, the obtained filter substrate has low absorption of light in the near infrared region. On the other hand, when the amount of the metal compound used exceeds 50 parts by weight, it becomes difficult for the ionic metal component to be uniformly contained in the copolymer.

The content of copper ions in the filter substrate is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the copolymer.

The method for obtaining the copolymer containing the ionic metal component is not particularly limited, but the following two methods can be mentioned as preferred methods.

(1) Before the radical polymerization of the mixed monomer, the metal compound and a specific phosphoric acid group-containing unit amount are added by adding and dissolving the metal compound in the mixed monomer. A method of preparing a monomer mixture comprising a polymer and a copolymerizable monomer, and radically polymerizing the monomer mixture.

(2) A method in which the metal compound is added to and mixed with the copolymer obtained by radical polymerization of mixed monomers. As this method, a method of adding and mixing a metal compound to the melted copolymer, a method of dissolving the copolymer in an organic solvent and adding and mixing the metal compound to this solution can be used.

By the methods described in (1) and (2) above, an optical filter material which is a copolymer containing an ionic metal component mainly containing copper ions can be obtained. This optical filter material, depending on the purpose, use
The filter substrate can be manufactured by molding and polishing into a plate shape, a column shape, a lens shape, or the like.

In the above, the copper ion of the added copper compound is bonded to the phosphate group as a ligand in the mixed monomer or copolymer, and the counter ion of copper ion is discharged. As a method of removing the counter ions, a method of extracting and removing the obtained optical filter material by immersing it in water or various organic solvents can be used. When a copolymer containing an ionic metal component is obtained by the above method (1), the monomer mixture before polymerization is removed by performing filtration, heating, vacuum suction treatment, or the like. Any method can be used. Further, when the counter ion is small, it can be used as it is as an optical filter material without performing the above removing operation.

Since the above-mentioned filter substrate contains copper ions and phosphoric acid groups, it may absorb moisture under severe conditions of high temperature and high humidity to reduce transparency. However, in the optical filter of the present invention, since the coat layer made of the polyfunctional acrylic resin is formed on the surface of the filter substrate, it has excellent moisture resistance.

The coating layer made of this polyfunctional acrylic resin contains at least 30% by weight of a polyfunctional acrylic monomer having two or more radically polymerizable acrylic groups or methacrylic groups in one molecule. It is formed by applying a coating layer forming liquid containing a monomeric component, a photopolymerization initiator, and an organic solvent on the surface of the filter substrate and curing the coating film by ultraviolet irradiation or the like.

In such a photopolymerization method, since the coating layer forming liquid has a long pot life and can be cured without heating, the coating layer is formed with almost no influence of heat on the filter substrate. can do. Further, since the formed coat layer has a high cross-linking density, it has high surface hardness, moisture-proof effect, chemical resistance, and
It is excellent in various properties such as heat resistance.

The polyfunctional acrylic monomer may be the same as the polyfunctional acrylate or polyfunctional methacrylate exemplified as the copolymerizable monomer for obtaining the copolymer in the filter substrate. Of these, particularly preferred are trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate,
Examples include trifunctional or higher-functional polyfunctional acrylic monomers such as pentaerythritol trimethacrylate, pentaerythritol tetraacrylate, and pentaerythritol tetramethacrylate.

Examples of the monomer other than the polyfunctional acrylic monomer include the same as those exemplified as the copolymerizable monomer for obtaining the copolymer in the filter substrate. For example, methyl acrylate. , Methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-
Propyl acrylate, n-propyl methacrylate,
Lower alkyl acrylates and lower alkyl methacrylates such as n-butyl acrylate and n-butyl methacrylate, modified alkyl acrylates and modified alkyl methacrylates such as glycidyl acrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate, styrene,
Examples thereof include aromatic vinyl compounds such as α-methylstyrene and divinylbenzene, and carboxylic acids such as acrylic acid and methacrylic acid.

Examples of the organic solvent used in the coating layer forming liquid include various alcohols, ethers, ketones and esters.

In the above, when the content ratio of the polyfunctional acrylic monomer in the acrylic monomer component in the coating layer forming liquid is less than 30%, the hardness of the formed coating layer is low, and The resulting optical filter has insufficient moisture resistance.

The ratio of the acrylic monomer component and the organic solvent used in the coating layer forming liquid is in the range of 10:90 to 60:40 by weight ratio acrylic monomer component: organic solvent. It is preferable. When the proportion of the acrylic monomer component is less than 10% by weight, the formed coat layer has a small thickness and the optical filter obtained has insufficient moisture resistance. On the other hand, when the proportion of the acrylic monomer component exceeds 60% by weight, the formed coat layer has a large thickness and is easily peeled off.

Such a coating layer forming liquid is applied to the surface of the filter substrate by, for example, a dipping method, a spraying method, a spinner method or the like, and the filter substrate coated with the coating layer forming liquid is applied to a low pressure mercury lamp, The coating layer is formed by irradiating with ultraviolet rays using a high pressure mercury lamp, an X-ray lamp, or various halogen lamps.

In the present invention, the thickness of the coat layer made of this polyfunctional acrylic resin is preferably 0.2 to 30 μm, more preferably 0.3 to 20 μm. When the thickness of the coat layer is less than 0.2 μm, the optical filter has insufficient moisture resistance. On the other hand, when the thickness of the coat layer exceeds 30 μm, the coat layer is easily peeled off, and cracks are easily generated in the coat layer during heating or deformation,
The optical filter has insufficient moisture resistance.

The optical filter of the present invention obtained as described above has a high absorptivity of light in the near infrared region as compared with a conventional glass filter, but has a small specific gravity and is easy to process. In addition, since it has excellent moisture resistance, it can be suitably used as a photometric filter for adjusting the characteristics of the photodiode, and particularly as a red visibility correction filter.

[0040]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited thereto. In the following, "part" means "part by weight".

[Example 1] 10 parts of a specific phosphoric acid group-containing monomer represented by the following chemical formula 3, 10 parts of a specific phosphoric acid group-containing monomer represented by the following chemical formula 4, and methyl methacrylate 5
8.5 parts and diethylene glycol dimethacrylate 2
A mixed monomer was prepared by thoroughly mixing 0 part and 1.5 parts of α-methylstyrene. To this mixed monomer, 14 parts of anhydrous copper benzoate (the content of copper ion with respect to 100 parts of the mixed monomer was 2.9 parts) was added, and fully mixed by stirring and mixing at 60 ° C. A monomer mixture was obtained in which copper benzoate was dissolved in the mixed monomer.

[0042]

[Chemical 3]

[0043]

[Chemical 4]

To the monomer mixture prepared as described above, 2.0 parts of t-butylperoxypivalate was added, and the mixture was added at 45 ° C. for 16 hours, then at 60 ° C. for 8 hours, and further 9 times.
By performing casting polymerization by heating at 0 ° C. for 3 hours at different temperatures in sequence, an optical filter material made of a cross-linked polymer containing copper ions was obtained. This optical filter material was cut to form a plate-shaped body having a thickness of 1 mm, and the plate-shaped body was dipped in methanol to give an amount of benzoic acid of about 95% by weight based on the amount of the acid group component of the copper benzoate used. After being extracted and removed, surface polishing was performed to produce a filter substrate. The specific gravity of this filter substrate was as small as 1.24, and the refractive index was 1.505.

Next, 60 parts of pentaerythritol tetraacrylate and 40 parts of diethylene glycol diacrylate were mixed, 2 parts of "IRGACURE 184" manufactured by Ciba-Geigy Co., Ltd. was added as a photopolymerization initiator, and methyl ethyl ketone was used as an organic solvent. To prepare a coating layer forming liquid by diluting so that the proportion of the monomer components becomes 40% by weight, and applying the coating layer forming liquid on the surface of the filter substrate by a spinner method, followed by air drying, and then A coating layer was formed on the surface of the filter substrate by irradiating with a high pressure mercury lamp for 1 hour. The thickness of the coat layer is 3 μm
Met.

The spectral transmittance curve of the obtained optical filter was measured using a spectrophotometer. The results are shown in Fig. 1.

The obtained optical filter was heated at a temperature of 60.
A humidity resistance test was conducted under conditions of ° C and 90% relative humidity. When the optical filter was observed after 1000 hours of the humidity resistance test, no apparent change was observed. Further, when the spectral transmittance curve of this optical filter was measured, no change was observed as compared with the spectral transmittance curve before the moisture resistance test.

[Comparative Example 1] A filter substrate manufactured in the same manner as in Example 1 was subjected to a moisture resistance test under the same conditions as in Example 1. When the filter substrate was observed after 800 hours of the moisture resistance test, some very thin white spots were observed on the surface of the filter substrate, but when the spectral transmittance curve was measured, the spectral transmittance curve of the optical filter of Example 1 was found. No difference was observed compared to. However, when the filter substrate was observed after 1000 hours of the moisture resistance test, many white spots were formed on the surface of the filter substrate, and when the spectral transmittance curve was measured, the transmittance in the visible region (about 350 to 700 nm) was observed. The rate was reduced by about 10%.

Example 2 15 parts of the specific phosphoric acid group-containing monomer represented by the above Chemical formula 3, 15 parts of the specific phosphoric acid group-containing monomer represented by the above Chemical formula 4, methyl methacrylate Four
A mixed monomer was prepared by thoroughly mixing 5 parts, 20 parts of 1,4-butanediol diacrylate, and 5 parts of methacrylic acid. To this mixed monomer, 15 parts of anhydrous copper acetate (copper ion content per 100 parts of mixed monomer is 5.3 parts)
And iron (II) oxalate dihydrate (FeC ₂ O ₄ .2H ₂
O) 1 part (the content ratio of iron ions to all metals is 5.4.
%) And were sufficiently dissolved by stirring and mixing at 60 ° C. to obtain a monomer mixture in which anhydrous copper acetate and iron oxalate were dissolved in the mixed monomer.

Using the monomer mixture prepared as described above, cast polymerization was carried out in the same manner as in Example 1 to obtain an optical filter material comprising a crosslinked polymer containing copper ions and iron ions. Got This optical filter material was cut to prepare a plate-shaped body having a thickness of 1 mm, and the plate-shaped body was immersed in methanol to obtain the total amount of acid group components of anhydrous copper acetate and iron (II) oxalate dihydrate used. After extracting and removing about 92% by weight of acetic acid and oxalic acid, surface polishing was performed to prepare a filter substrate.
This filter substrate has a specific gravity of 1.29 and a refractive index of 1.
It was 511.

Next, 40 parts of pentaerythritol tetraacrylate, 35 parts of trimethylolpropane trimethacrylate, and 25 parts of n-butyl acrylate were mixed, and "Irgacure 18" as a photopolymerization initiator was mixed therein.
4 "was added and mixed, and then the mixture was diluted with a mixed solvent of methyl ethyl ketone and dioxane so that the ratio of the monomer components was 35% by weight to prepare a coating layer forming liquid. A coating layer was formed on the surface of the filter substrate in the same manner as in Example 1 using the forming liquid. The coat layer had a thickness of about 2.6 μm.

The spectral transmittance curve of the obtained optical filter was measured using a spectrophotometer. The results are shown in Fig. 1.

Further, regarding the obtained optical filter,
A moisture resistance test was conducted in the same manner as in Example 1, and the moisture resistance test 1
When the optical filter was observed after 000 hours, no change was apparently observed. Further, when the spectral transmittance curve of this optical filter was measured, no change was observed as compared with the spectral transmittance curve before the moisture resistance test.

[Comparative Example 2] A filter substrate produced in the same manner as in Example 2 was subjected to a moisture resistance test under the same conditions as in Example 1. When the filter substrate was observed after 800 hours of the humidity resistance test, extremely thin white spots were observed on the surface of the filter substrate. Also, the humidity resistance test 100
When the spectral transmittance curve of the filter substrate was measured after the lapse of 0 hours, it was compared with the spectral transmittance curve of the optical filter of Example 2, and the visible region (about 350 to
At 700 nm), the transmittance was reduced by about 8%.

[0055]

As described above, in the optical filter of the present invention, the filter substrate constituting the optical filter comprises a mixed monomer composed of a specific phosphoric acid group-containing monomer and a copolymerizable monomer. Since the copolymer obtained by copolymerization contains an ionic metal component mainly composed of copper ions, it has a high absorptivity for light in the near infrared region, has a small specific gravity, and It is easy to process. Further, since the coat layer made of a polyfunctional acrylic resin is formed on the surface of the filter substrate, it does not absorb moisture and devitrify with time, and thus has excellent moisture resistance. Therefore, it can be suitably used as a photometric filter or a visibility correction filter of a camera.

[Brief description of drawings]

FIG. 1 is a spectral transmittance curve diagram of optical filters according to Example 1 and Example 2.

[Explanation of symbols]

 1 Spectral transmittance curve of optical filter of Example 1 2 Spectral transmittance curve of optical filter of Example 2

Claims (2)

[Claims] 1. A copolymer obtained by copolymerizing a phosphoric acid group-containing monomer represented by the following chemical formula 1 and a monomer copolymerizable therewith, and a phosphoric acid group of the copolymer. An optical filter comprising a filter substrate containing a bonded ionic metal component mainly composed of copper ions, and a coating layer made of a polyfunctional acrylic resin formed on the surface of the filter substrate. [Chemical 1] 2. The optical filter according to claim 1, wherein the coat layer has a thickness of 0.3 to 20 μm.