JPH0413763A - Heat-resistant optical material having high refractive index and transparency - Google Patents

Abstract

PURPOSE:To obtain an optical material attaining high refractive index by low- temperature heat-treatment, having excellent light transmittance, etc., in visible range and suitable for micro-lens of color filter, etc., by compounding a specific polyimide and a specific transition element oxide at specific ratios. CONSTITUTION:The objective material can be produced by compounding (A) 80-99.9 pts.wt. of a polyimide having a light transmittance of >=90% at 400mum wavelength and having a recurring unit of formula [R is 6-30C aromatic ring; X is -O-, -SO2-, -CO-, -CH2 or -C(CH3)2; Q is 6-30C aromatic ring; at least one of the Q groups has a bond at 2- or 3-site in regard to X; Y is X except for -CO-; n is 1 or 2] and (B) 0.1-2 pts.wt. of oxide of transition elements of group IV and/or group V of the periodic table (e.g. titanium oxide, zirconium oxide or antimony oxide).

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a highly refractive, highly transparent, heat-resistant optical material, and more specifically to a polyimide optical material that has a large refractive index even when heat treated at a low temperature. It is something.

[Prior Art] In recent years, with the rapid development of video cameras, there has been a demand for smaller cameras, and the screen size of solid-state image sensors used for this purpose has also increased from 1.2 mm to 1.773 inches. Miniaturized (for example, Nikkei Microdevice 1)
(December 989 issue).

However, such miniaturization leads to a decrease in the sensitivity of the solid-state image sensor, so it is necessary to place a condenser lens directly on the top surface of the color filter that makes up the light-receiving part. Is it necessary to collect the light on the light receiving part to prevent a decrease in sensitivity?

Conventionally, acrylic polymers and silicone materials have been considered for the microlens part, or materials made of this type have a refractive index of about 1.5, so they are located at the bottom of the microlens. Since the difference in refractive index with the material constituting the color filter becomes smaller, it is necessary to increase the curvature of the microlens in order to effectively collect light. For this reason, it is difficult to actually produce a solid-state image sensor using such a material because of difficulties such as a thick film thickness and a high level of processing precision.

For this reason, polyimide resin, which has one of the highest refractive indexes among organic polymers, is being considered for this application, but ordinary polyimide resin has poor light transmittance and high It has not yet been put into practical use because it has problems such as the need for heat treatment at a temperature of 300 degrees or higher in order to obtain a good refractive index.

On the other hand, inorganic materials such as titanium oxide and thallium oxide are known as high refractive materials, and when these materials are applied thickly, the materials themselves are extremely brittle.
There are problems in that it is easy to crack and requires a high temperature of 400 degrees or more to obtain a high refractive index. Furthermore, when these materials are mixed into acrylic or silicone resins, there are problems with the heat resistance, mechanical properties, etc. of the resins, and the required performance cannot be achieved, making it difficult to put them into practical use. Ta.

In view of the current state of the conventional technology, the present inventors aimed to develop a material that can obtain a high refractive index through heat treatment at low temperatures, has excellent transmission performance in the visible light region, and has high heat resistance. As a result of intensive research into composites of resin and inorganic materials, we found that when polyimide with a specific structure is mixed with a special oxide, visible light transmittance with an unexpectedly large refractive index can be achieved through low-temperature heat treatment. The present inventors have discovered that a heat-resistant optical material with excellent mechanical properties can be obtained, and the present invention has been achieved.

[Invention or Problem to be Solved] Therefore, an object of the present invention is to provide an optical device that can obtain a high refractive index by heat treatment at low temperatures, has excellent light transmission performance in the visible light region, and has good mechanical properties and heat resistance. The purpose is to provide materials.

[Means for Solving the Problems] The object of the present invention is to provide 80.0 to 99.9 parts by weight of polyimide having a light transmittance of 90% or more at 400 nm, and a polyimide of Group Ⅰ and 7/or 7 of the periodic table. Oxide of group transition element 0. This is achieved by a highly refractive, highly transparent, heat-resistant optical material characterized by comprising 1 to 20 parts by weight.

The polyimide used in the present invention is required to be transparent to visible light, so at a wavelength of 400 nm, the polyimide
% or more.

Such a polyimide has the following general formula (R is an aromatic ring having 6 to 30 carbon atoms, X is -O---S
One type of O O--5O7--CH2
- and n are 1 or 2. ) It is preferable that it has a structure represented by
It can be produced by combining a tetracarboxylic acid corresponding to this structure and a diamine.

Specific examples of polyimides preferably used in the present invention include 3.3', 4.4'-biphenyltetracarboxylic acid and 1.3-bis(aminophenoxy)benzene.
3', 4.4'-biphenyltetracarboxylic acid and 3.3'-diaminodiphenylsulfone, 3.3'
, 4,4'-biphenyltetracarboxylic acid and 3,4'
-diaminodiphenyl ether, 3.3', 4.4'
-Biphenyltetracarboxylic acid and 3,4'-diaminodiphenylmethane, 3.3',4.4'-diphenyl ethertetracarboxylic acid and 1,3-bis(aminophenoxy)benzene, 3.3',4.4'- Diphenyl ether tetracarboxylic acid and 3.3'-diaminodiphenylsulfone, 3.3',4.4'-diphenyl ether tetracarboxylic acid and 3.4'-diaminodiphenyl ether, 3.3',4.4'-diphenyl ether tetracarboxylic acid. acid and 3.4'diaminodiphenylmethane, 2,2-bis(3°4-dicarboxyphenyl)-propane and 1.3bis(aminophenoxy)benzene, 2.2bis(3,4-dicarboxyphenyl) )-propane and 3,3′-diaminodiphenylsulfone, 2°2-bis(3,4-dicarboxyphenyl)
-propane and 3,4'-diaminodiphenyl ether,
2.2-bis(3,4-dicarboxyphenyl)-propane and 3.4′-diaminodiphenylmethane, 3.3
', 4.4'-diphenylsulfone tetracarboxylic acid and 3.3'-diaminodiphenylsulfone, 3.3
Examples include, but are not limited to, 4,4'-benzophenonetetracarboxylic acid, 3,3'-diaminodiphenylsulfone, and copolymers thereof.

The method for producing the polyimide of the present invention involves mixing the corresponding tetracarboxylic acid anhydride and diamine with a dipolar aprotic solvent such as N-methylpyrrolidone or dimethylformamide, or combining these dipolar aprotic solvents with xylene, calpitol, cellosolve, In a mixture of ethyl cellosolve acetate and aromatic hydrocarbons such as diisobutyl ketone, glycol solvents, ketone solvents, etc.
A corresponding polyimide precursor varnish can be obtained by reacting at a temperature ranging from 100 degrees to 100 degrees.

The polyimide of the present invention includes aromatic tetracarboxylic acids such as pyromellitic acid, aliphatic tetracarboxylic acids such as 1.2.3.4-butanetetracarboxylic acid, and 1.2.3.4-cyclopentanetetracarboxylic acid. Aromatic dicarboxylic acids such as tetracarboxylic acid and terephthalic acid, aliphatic dicarboxylic acids such as adipic acid, para-phenylene diamine, meta-phenylene diamine, 4,4'-diaminodiphenyl ether, 4. 4'-diaminodiphenylmethane, aromatic diamines such as benzidine, hexamethylene diamine,
Aliphatic diamines such as heptamethylene diamine can be copolymerized within a range that does not significantly reduce the transmittance of visible light.

The polyimide accounts for 80 to 99.9 parts by weight of the entire optical material.
It is preferable to mix within a range of parts by weight, more preferably 9 parts by weight.
The range is from 0 parts by weight to 99 parts by weight.

If the polyimide component is more than the above range, an improvement in the refractive index can be expected; if it is less than the above range, it will become brittle and good mechanical properties cannot be expected.

In addition, in order to improve adhesion to the substrate, siloxane diamine such as 1゜3-bis(aminopropyl)tetramethyldisiloxane is copolymerized with 1 to 5 mol% of the total diamine component, or oxypropyl Apply a silane coupling agent such as trimethoxysilane or γ-aminopropyltriethoxysilane, an aluminum chelate compound such as aluminum tris (ethyl acetoacetate), a titanium chelate compound such as titanium bis (acetylacetonate), etc. to the base in advance. It is also preferable to apply it to the surface.

The optical material of the present invention comprises the above-mentioned polyimide and Group Ⅰ and VIII of the periodic table. It is important that the oxide is composed of an oxide of a transition element of Group Ⅰ.

Examples of the oxides of the transition elements in group Ⅰ of the periodic table used in the present invention include titanium oxide and zirconium oxide, and examples of oxides of the transition elements in group Ⅰ of the periodic table include antimony oxide and niobium oxide. These are preferably added in the form of fine particles. Among the above, a particularly preferred oxide is zirconium oxide. These oxides of transition elements of Group 1 or Group 2 of the periodic table may be used alone, or both may be used in combination.

From the viewpoint of light scattering, the particle diameter of the oxide fine particles is preferably less than or equal to the wavelength of visible light, and more preferably 11
00n or less.

The oxide is preferably added in an amount of 0.1 part by weight or more and 20 parts by weight or less based on the entire optical material, more preferably 1 part by weight or more and 10 parts by weight or less. If the amount added is less than this range, no change in the refractive index will be observed, and if the amount added is more than this range, cracks are likely to occur, layer separation occurs, and the transmittance decreases, which is not preferable.

The highly refractive, highly transparent, heat-resistant optical material of the present invention is preferably used for microlenses of color filters, top coating agents, hard coating agents for optical lenses, and the like.

[Method for measuring characteristics] (1) Measurement of transmittance Using a self-recording spectrophotometer UV-260 manufactured by Shimadzu Corporation,
About 3 microns of polyimide was coated on Pyrex glass and heat treated at 100 degrees for 1 hour and at 170 degrees for 2 hours, and the transmittance from 300 to 500 nm was measured.

(2) Measurement of refractive index Polarization analyzer (Ellipsometer) DV manufactured by Mizojiri Optical Kogyo Co., Ltd.
-36L type was used to coat a silicon wafer with polyimide to a thickness of about 1000 angstroms, heat treatment was performed at 100 degrees for 1 hour and at 170 degrees for 2 hours, and the refractive index was measured.

EXAMPLES The present invention will be specifically explained below using examples, but the present invention is not limited thereto.

Example 1 31.02 g of 3.3',4.4'-diphenyl ether tetracarboxylic dianhydride and 24.85 g of 3,3'diaminodiphenylsulfone were mixed with N-methylpyrrolidone 2
00 g, 50 in 90 g of ethyl cellosolve acetate
The reaction was carried out at 80°C for 1 hour and 5 hours to obtain a polyimide precursor varnish.

200 parts by weight of this varnish and 1 part by weight of zirconium oxide with a particle size of 1100 nm were mixed, stirred at 30°C for 3 hours, filtered through a 5 micron filter, and the transmittance and refractive index were measured. However, the transmittance at 40Qnm was 95%, and the refractive index was 1.73, which were good values.

Further, when a film sample for transmittance measurement was evaluated, the obtained film was a strong film with self-supporting properties.

Example 2 29.42 g of 3.3',4.4'-biphenyltetracarboxylic dianhydride and 20.02 g of 3.4'-diaminodiphenyl ether were mixed with 200 g of N-methylpyrrolidone.
g, and reacted in 70 g of diisobutyl ketone at 50°C for 1 hour and at 80°C for 5 hours to obtain a polyimide precursor varnish. 200 parts by weight of this varnish and 1 part by weight of titanium oxide with a particle size of 40% m were mixed, stirred at 30°C for 3 hours, and then filtered through a 5 micron filter. When measured, the transmittance at 400 nm was 94%, and the refractive index was 1.72, which were good values. Moreover, the obtained film was a strong film with self-supporting properties.

Comparative Example 1 21.82 g of pyromellitic anhydride and 10.81 g of metaphenylenediamine were reacted in 150 g of N-methylpyrrolidone at 50'C for 1 hour and at 80C for 4 hours to obtain a polyimide precursor varnish.

When the transmittance and refractive index of the obtained varnish were measured, the transmittance at 400 nm was 50% and the refractive index was as low as 1.66.

Comparative Example 2 Using the polyimide precursor varnish synthesized in Comparative Example 1,
Heat treatment of polyimide at 100°C for 1 hour at 170°C
Similar evaluations were made for time and 300° 01 hours, and the refractive index was 1.74, which was good.
The transmittance was a low value of 48%.

Comparative Example 3 32.22 g of 3.3', 4.4'-benzophenone tetracarboxylic acid and 20.02 g of 4.4'-diaminodiphenyl ether were mixed in 250 g of N-methylpyrrolidone at 30°C for 1 hour and at 80°C for 3 hours. A polyimide precursor varnish was obtained by reaction.

When the transmittance and refractive index of this material were measured, the refractive index was 1.64.The transmittance at 400 nm was 53%.

[Effects of the Invention] Since the present invention is configured as described above, it is possible to obtain a high refractive index by heat treatment at low temperatures, to have excellent light transmission performance in the visible light region, and to have heat resistance with good mechanical properties. You can get it.

Claims (3)

[Claims] (1) 80.0 to 99.9 parts by weight of polyimide with a light transmittance of 90% or more at 400 nm and
Oxides of group IV and/or group V transition elements 0.1~
20 parts by weight of a highly refractive, highly transparent, heat-resistant optical material. (2) The high refractive, highly transparent, heat-resistant optical material according to claim 1, wherein the polyimide having a light transmittance of 90% or more at 400 nm has a repeating unit represented by the following formula. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, R is an aromatic ring with 6 to 30 carbon atoms,
-O-, -SO_2-, -CO-, -, -CH_2-
and ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and each Q is an aromatic ring having 6 to 30 carbon atoms, and at least one is bonded to the 2nd or 3rd position of X. It is an object with hands, and Y is -O-, -SO_2-, -CH_2-, and ▲Mathematical formulas, chemical formulas, tables, etc.▼
One type selected from the group of , and n is 1 or 2. ) (3) The oxide of a transition element of Group IV and/or Group V of the periodic table is at least one selected from the group of titanium oxide, zirconium oxide, antimony oxide, and niobium oxide.
The highly refractive and highly transparent heat-resistant optical material according to claim 1, which is a seed.