JPS61117501A - Near infrared transmittable material - Google Patents

Abstract

PURPOSE:To improve the transmittivity of near IR light by using an epoxy resin compsn. having the specific concn. of hydrogen functional group for the carbon atom of an aliphat. and/or alicyclic carbon-carbon satd. bond. CONSTITUTION:The epoxy resin compsn. having <=60mol/l concn. of the hydrogen functional group to be coupled to the carbon atom of the aliphat. and/or alicyclic carbon-carbon satd. bond is used. The absorption peak owing to 1.17-1.18mum C-H stretching vibration is attenuated and the tailing to 1.20mum band is eliminated or 1.13-1.14mum peak increases but the absorption peak as a whole decreases and the transmittivity of the near IR is increased. The liquid compsn. having low viscosity at an ordinary temp. is obtd. by using the epoxy resin as such org. material and the compsn. can be adjusted to the desired concn. of the hydrogen functional group by combination of the epoxy resin which is the principal material and hardener. The compsn. is liquid in an uncured state and therefore extraneous matter can be easily removed by filtration, by which the scattering loss is prevented and the compsn. is usable as the excellent near IR transmittable material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a near-infrared light transmitting material that has excellent transparency in the near-infrared region.

More specifically, by reducing the material-specific absorption loss at specific wavelengths in the near-infrared region, we are developing micro-optical components such as microlenses that have increased light transmittance at wavelengths of 1 μm or more.
The present invention relates to a near-infrared light transmitting material made of a suitable epoxy resin composition.

[Prior Art] Development of optical communication systems using optical fibers is progressing at a rapid pace in preparation for the information society that has progressed in recent years.

The core of the current optical communication system is a near-infrared optical communication system that uses optical 77 bars as a transmission path and near-infrared light of 0.8 μm or more as the transmitted light, and the material used for these is quartz. These include various glasses such as glass, and electro-optic crystals such as lithium niobate.

Compared to the widespread use of organic materials in the electronics field these days, the use of organic materials in the optical communications field is extremely small, and this is because there is almost no data on organic materials in the near-infrared region, making it difficult to determine whether or not to use them. This is because it is very important.

[Objective of the Invention 1] While studying the optical properties of organic materials in the near-infrared region, the present invention aims to develop materials with excellent light transmittance in the wavelength range that is used or expected to be used in optical communications. The present invention was achieved as a result of research aimed at obtaining a solution.

[Configuration 1 of the Invention The wavelength of light used for optical communication is determined by the loss characteristics of the quartz optical fiber and the semiconductor laser.

The wavelength bands currently used for optical communications are 0.8 to 0.9μ, which has relatively low loss in optical fibers, and 1, 1 to 1.35μ, and 0.2d, which have a low loss of less than 1dB/km.
There are three wavelength bands of 1 and 55 μm, which are ultra-low loss regions below B/ka+.

After examining the loss spectra of various organic materials in these three wavelength ranges, we found that 1 and 2 μm, which will be most frequently used in the future,
An extraordinary absorption peak was observed in the wavelength range centered on .

As a result of analysis, this is hydrogen bonded to the carbon of a saturated carbon-carbon bond, that is, methyl group (-CH3), methylene group (>CH
It was found that the vibration was caused by high-order harmonics of C-H stretching vibrations such as 2).

Absorption due to C-H stretching vibration of saturated hydrocarbons is 3.37~
On the other hand, absorption due to C--H stretching vibration of unsaturated hydrocarbons such as aromatics appears at 3.3 .mu.m or less, for example, in benzene, it appears at 3.25 to 3.28 .mu.m.

These third harmonics appear in a wavelength range slightly different from the calculated value due to anharmonicity, but the former is 1.17 to 1.18μ.
For ships, the latter is close to 1.12 to 1.14 μ-1.

Looking at the absorption of polymethyl methacrylate (PMMA), which is currently the most transparent and widely used material in the visible range, in the 1.2 μm region, a peak with an absorption maximum at 1.175 μm is observed, and the tail of the peak amount to 1.2 μm.

Assuming that there are 20 songs within the half-maximum spectrum of the semiconductor laser, the absorption peak at 1,175 μm is extremely harmful.

Furthermore, when considering the breakdown of the insertion loss of optical components, there are absorption loss due to the material, scattering loss, and Fresnel reflection loss at the connection surface.

Considering that the transmitted light is limited to near-infrared light of 1 μm or more, the scattering loss is 0°5 if the material can be filtered by a filter.
Since impurities of /7I11 or more can be considerably removed, and Rayleigh scattering is proportional to 1/4th power of the wavelength, it cannot become a major loss factor.

Furthermore, if the interface is smooth and the optical axis is perpendicular to the surface, the Fresnel reflection loss will be about 0.1 dB at most even if the difference in refractive index is large, and this will not result in a large scattering loss.

However, the material-specific absorption loss is Lambert-Beer (
According to Lambert-Beer's law, the transmittance in a wavelength range where absorption occurs decreases in proportion to the optical path length, which poses a major problem in the design of optical components.

As stated above, in order to obtain a material with improved transmittance, the first step is to reduce the absorption loss inherent in the material.

Here, the present invention provides a material with excellent transmittance in the near-infrared region, particularly in the 1.2μ band, and shows a specific method for obtaining an optical component suitable for near-infrared optical communication.

The present invention requires that the concentration of hydrogen functional groups bonded to carbon atoms of aliphatic and/or alicyclic carbon-carbon saturated bonds expressed in terms of functional group concentration (mol/l) is 60 mol/l or less. The present invention relates to a near-infrared light transmitting material that is characterized by excellent near-infrared light transmittance.

The near-infrared light transmitting material used in the present invention has a hydrogen concentration of aliphatic or alicyclic CH bonds, that is, a hydrogen concentration of methyl groups (-CH,), methylene groups (>CH2), etc., of 60 mol/l or less. Some organic materials, especially plastic materials.

The hydrogen functional group concentration here was determined by the following formula (1).

×Density (g/am3)X100O---(1)(
1) The hydrogen functional group concentration expressed by the formula is 601110+/
It must be less than 1, and if it exceeds 1.1
The absorption loss becomes large in the range of 7 to 1.18 μm, and it cannot be used as an optical component for optical communication unless there is a degree of freedom in design.

Plastics with a structure consisting mainly of aromatic rings are suitable as such organic materials, and plastics with a structure in which the hydrogen of a methyl group, methylene group, or methine group is replaced with halogen elements such as fluorine or chlorine or deuterium are suitable. Plastics with 300 mm are preferred.

Here, if a halogen element other than fluorine is contained, the refractive index will increase, and there is a concern that Fresnel reflection loss will increase when connecting to a glass optical fiber.

However, the ratio of the transmitted light power Pt to the incident light power Pi is now expressed by equation (2).

(Here, φ is the incident angle, and n1t12 is the refractive index of the medium.) Here, nl is the refractive index of quartz, which is 1.46, and n2 is the refractive index of the organic material, which is estimated to be 1.7. The loss (-10logPt/Pi) is about 0.025 dB (0.58%) even if some axis deviation is considered.

This value is insignificant compared to the absorption loss inherent to the material.

Plastics having an aromatic ring as a main structure include so-called engineering plastics such as bisphenol A polycarbonate, polysulfone, and polyetheretherketone, and aromatic epoxy resins such as a bisphenol A skeleton.

Epoxy resin has the following characteristics compared to the engineering plastics mentioned above.

By selecting an epoxy resin, a liquid composition with low viscosity at room temperature can be obtained.

Various variations can be obtained by combining the epoxy resin as the main ingredient and the curing agent, and the hydrogen functional group concentration represented by formula (1) can be adjusted in various ways.

If an acid anhydride is selected as the curing agent, purification (purification) and defiltration in a heated state is also possible.

Furthermore, the cured product has sufficiently high heat resistance, making it a very useful material for the purpose of the present invention.

In the epoxy resin composition, the epoxy resin is bisphenol A glycidyl ether, bisphenol F diglycidyl ether, tetrabromobisphenol A diglycidyl ether, hexafluorobisphenol A diglycidyl ether, etc., and the curing agent is m-xylene diamine, nadic anhydride (5 -Norbornene-2-3 dicarboxylic acid anhydride), chlorendic anhydride (1,4,5,6,
7,7-hexachloro-5-norbornene-2,3 dicarboxylic acid anhydride) and the like are suitable.

These compounds are in a liquid state in an uncured state, and scattering loss can be kept low by removing impurities such as dust of μm or more by filtration with a filter.

For this reason, compared to the extremely high melting point of thermoplastic plastics consisting of aromatic rings, epoxy resins are much better as resins for materials that transmit near-infrared light.

When using a halogen-carbon compound substituted with halogen, the halogen concentration of halogens other than fluorine is preferably 20 mol/l or less.

This is because if the halogen concentration is 20 mol/l or more, the stability against heat and light will be significantly impaired.

[Effect of the invention 1] When the above-mentioned near-infrared light transmitting material is used and the method of the present invention is followed, the absorption peak due to the C-H stretching vibration of 1.17 to 1.18 μm is attenuated, and the absorption peak in the 1.20 μm band is reduced. Although the skirt disappears or the peak at 1.13 to 1.14 μm increases, the overall absorption peak becomes lower and the transmittance of near-infrared light is significantly improved.

[Example 1 The present invention will be explained in detail below with reference to Examples.

The transmittance was measured using a monochromator G250 manufactured by Nippon Kogaku Co., Ltd. and a PbS detector manufactured by Zirco Co., Ltd.

Examples Bisphenol A diglycidyl ether (trade name Kobomic R-140, manufactured by Mitsui Petrochemical Industries, Ltd.) and methylnadic anhydride (methyl-5-norbornene-2,3-
dicarboxylic anhydride) and chlorendic anhydride (1,4,5
,6,7゜7-hexachloro-5-norbornene-2,
An epoxy resin composition consisting of 3-dicarboxylic anhydride) was heated to 80°C, passed through a Tetron membrane filter with an average pore size of 0.47 μm, and then poured between two glass plates. 1. A board with five wheels was obtained.

The concentration of hydrogen functional groups bonded to the carbon of the saturated carbon-carbon bond contained in this composition was 51 mol/l, and the halogen (chlorine) concentration was 4 mol/l.

The results of transmittance measurements are shown in FIG. 1 and Table 1.

Comparative Example 1 An epoxy resin composition consisting of an alicyclic epoxy resin (trade name: Celoxai #2021 (manufactured by Daicel Chemical Industries, Ltd.)) and methyl nadic anhydride was prepared in the same manner as in Example 1 to form a 1.5 mm thick plate. I got it.

The concentration of hydrogen functional groups bonded to the carbon of the saturated carbon-carbon bond contained in this composition was 85 mol/l.

The results of transmittance measurements are shown in FIG. 2 and Table 1.

Comparative Example 2 A 1.5-thick plate was obtained by injection molding polymethyl methacrylate (PMMA) (Parapetney 10-10 manufactured by Kyowa Gas Chemical Industry Co., Ltd.).

The concentration of hydrogen functional groups bonded to the carbons of the saturated carbon-carbon bonds contained in the second polymethyl methacrylate (PMMA) was 95%.

The transmittance measurement results are shown in FIG. 3 and Table 1.

[Brief explanation of the drawing]

Figure 1 shows the loss spectrum of the example sample at 1.1 to 1.3 μm, and Figure 2 shows the loss spectrum of the comparative example 1 sample at 1.1 to 1.3 μm.
Loss spectrum at 1.3μ-, Figure 3 is Comparative Example 2-1
It is a loss spectrum at 1 to 1.3μ. Patent applicant Nippon Telegraph and Telephone Public Corporation Sumitomo Bakelite Co., Ltd. Figure 1 WAVE LENGTH (7zm) Figure 2

Claims (1)

[Claims] Aliphatic and/or expressed as functional group concentration (mol/l)
Alternatively, a near-infrared light transmitting material comprising an epoxy resin composition having a concentration of hydrogen functional groups bonded to carbon atoms of an alicyclic carbon-carbon saturated bond of 60 mol/l or less.