JPH0534741A - Organic nonlinear optical material and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Objective] Regarding a nonlinear optical material, an object thereof is to put into practical use an optical material having a large second-order nonlinear optical constant and a small orientation relaxation. [Structure] A one-dimensional polymer having at least one epoxy group in a side chain, preferably having a secondary molecular polarizability, and at least one substituent having an epoxy group-bonding ability, and a secondary A monomer with a molecular polarizability of 2 is mixed and heated while applying an electric field to chemically bond the polymer and the monomer, and the molecular orientation of the monomer is fixed, or at least one epoxy compound is attached to the side chain. A one-dimensional polymer having a group, preferably having a secondary molecular polarizability, and two or more kinds of functional groups capable of binding to an epoxy group but different in reactivity, and having a secondary molecular polarizability. After mixing with the monomer having the same and heating to a predetermined temperature while applying an electric field to bond the specific functional group of the oriented monomer with the epoxy group of the polymer, while applying a higher electric field, Higher than temperature The organic non-linear optical material is constructed by a method of fixing the molecular orientation of the monomer by heating to a predetermined temperature to bond the other functional group of the monomer to the epoxy group of the polymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic nonlinear optical material having excellent second-order nonlinear optical characteristics. Optical communication has been put to practical use because it is necessary to process a large amount of information quickly, and nonlinear optical materials are used for optical components such as optical polarizers, optical switches, and modulators used for this purpose.

Heretofore, lithium niobate (LiNb
Inorganic crystals such as O ₃ ) and lithium tantalate (LiTaO ₃ ) are used, but these materials have a large non-linear optical effect and a large permittivity, and are compatible with high-speed signals. There is a problem that can not be done.

Therefore, attention has been paid to organic compound crystals such as methylnitroaniline and urea as materials having a low dielectric constant and exhibiting a nonlinear optical effect. However, these organic crystals have problems that they are brittle and weak and difficult to handle, and it is difficult to form a thin film.

Therefore, an organic polymer nonlinear optical material which does not have such a problem is drawing attention.

[0005]

2. Description of the Related Art As an organic nonlinear optical material, there is a dispersed electric field oriented polymer in which polar molecules are added to a polymer material and oriented by applying an electric field in a dispersed state.

This polymer has features that it can be made into a thin film, the film forming process is simple, and the cost is low. However, there is a problem that the concentration cannot be increased.

On the other hand, it has been studied to prepare a copolymerized polymer containing polar molecules exhibiting second-order non-linearity and to subject this polymer to an electric field orientation by applying an electric field at a temperature higher than its glass transition temperature. A material with a sufficiently high value has not been found.

The second-order nonlinear optical effect (Pockels effect) does not appear in a substance having inversion symmetry. Therefore,
Also in the case of a dispersion type polymer or a copolymerization type polymer, polar molecules are oriented in the direction of the electric field by holding the polymer at a temperature higher than the glass transition temperature of the polymer and applying an electric field.

However, when such a method is adopted, (1) the orientation is disturbed by thermal motion in order to orient the molecules at a high temperature. (2) Orientation is hindered by steric hindrance between molecules. (3) Polarization is lost due to inversion of polar molecules over time. However, it is difficult to obtain a polymer having excellent electro-optical characteristics.

Here, as an example of the countermeasure of the problem (3), when an epoxy-amine is chemically bonded while applying an electric field, polar molecules are fixed because of three-dimensional cross-linking, and therefore orientation relaxation is small. It has been reported that a nonlinear material thin film can be formed. [Manfred Eich et al. J. Appl. Phys. 66 (7), 1 O
ctober (1989) 3241 to 3247] However, according to this document, when heated in a monomer state, the molecule sublimes before the binding reaction occurs, so it is necessary to polymerize the molecule to a certain degree before applying an electric field. It is stated that there is.

However, when the precure is performed in this manner, steric hindrance is caused due to the three-dimensional crosslinking of the monomers, and the orientation is inevitably lowered.

[0012]

As a material showing a second-order nonlinear optical effect, a copolymer containing polar molecules is prepared,
Organic non-linear optical materials have been studied in which an electric field is applied while heating the polymer to a temperature higher than the glass transition temperature to orient the polymer, but a material having a sufficiently high electro-optical constant and a stable material have not been found.

Therefore, it is a problem to put into practical use an organic nonlinear optical material which has a sufficiently high electro-optical constant and hardly causes orientation relaxation.

[0014]

[Means for Solving the Problems] The above-mentioned problems include a one-dimensional polymer having at least one epoxy group in a side chain, preferably having a secondary molecular polarizability, and a substituent having a binding ability with the epoxy group. Is there a method of fixing the molecular orientation of the monomer by mixing with a monomer having at least one and having a second-order molecular polarizability and heating while applying an electric field to chemically bond the polymer and the monomer. , Or one-dimensional polymer having at least one epoxy group in the side chain, preferably having a secondary molecular polarizability, and two or more kinds of functional groups capable of binding to the epoxy group but having different reactivities. After mixing with a monomer having a secondary molecular polarizability and heating to a predetermined temperature while applying an electric field, a specific functional group of the oriented monomer is bonded to the epoxy group of the polymer. , Higher electric field The organic nonlinear optical material is constructed by a method of fixing the molecular orientation of the monomer by heating it to a predetermined temperature higher than the previous temperature while applying it to bond other functional groups of the monomer to the epoxy group of the polymer. It can be solved by doing.

[0015]

The present invention suppresses steric hindrance that occurs when the side chains of polymers or polar parts of dispersed monomers are oriented, and as a method of eliminating orientation relaxation, it has at least one epoxy group in the side chains. In a state where a one-dimensional polymer and a monomer having at least one substituent (-NH ₂ , -OH, -COOH, etc.) capable of binding to an epoxy group and having a secondary molecular polarizability are uniformly mixed. An electric field is applied to orient the monomer, and the temperature is raised in this state to react with the epoxy group, thereby fixing the molecular orientation of the monomer.

Here, the one-dimensional polymer having at least one epoxy group in the side chain is a polymer represented by the general formula (1), and a polymer having a secondary molecular polarizability is generally It is a polymer represented by the formula (2), and the molecule represented by R ₂ is configured with an electron-donating substituent or an electron-withdrawing substituent.

Further, the monomer having one substituent that bonds to the epoxy group of such a polymer and having a secondary polarizability is an organic compound represented by the general formulas (3) to (5) in FIG. .

Further, a monomer having two substituents that bond to an epoxy group and having a secondary polarizability is an organic compound represented by the general formulas (6) and (7) in FIG. After uniformly mixing such a polymer and a monomer, an electric field is applied to raise the temperature in a state in which the monomer is oriented, and the epoxy group of the polymer and the substituent of the monomer are reacted to form a two-dimensional polymer through the monomer. The molecular orientation of the monomer can be fixed by cross-linking and polymerizing.

Next, a problem in using this monomer / polymer dispersion system is that when an electric field is applied, a polar monomer flows, so that dielectric breakdown easily occurs. Therefore, a sufficiently high electric field can be applied. Therefore, it is difficult to obtain sufficient molecular orientation force against thermal motion.

In this case, electric field orientation (poling) may be performed in two steps. That is, as a monomer, a substituent (-NH
_(2- , -OH, -COOH, etc.), and after mixing it uniformly with the polymer, heat it to the reaction initiation temperature of one type of substituent while applying an electric field to react with the epoxy group. , One end of the monomer is attached to the polymer backbone.

Next, when a higher electric field is applied and the temperature is raised to the reaction initiation temperature of the other substituent, the substituent and the epoxy group chemically bond, and as a result, the molecular orientation of the monomer is fixed. can do.

Here, the one-dimensional polymer having at least one epoxy group in the side chain is a polymer represented by the general formula (8) in FIG. A monomer having two polarizabilities while having two is an organic compound represented by the general formulas (9) to (11) in FIG.

[0023]

【Example】

Example 1: (corresponding to claim 1) In FIG. 7, a general formula (12)
The polymer shown in and the monomer shown in the general formula (13) were used.

First, 5 g of both were taken in a molar equivalent ratio and mixed, and this was dissolved in methyl cellosolve to prepare a 30 wt% liquid. Next, tin oxide (SnO ₂ ) and indium oxide (In
₂ O ₃ ) and a 50 mm square glass substrate equipped with a transparent electrode made of a solid solution (ITO for short), prepared with two polyimide insulating films coated on it, and spin coated with the above solution. Then, a thin film having a thickness of 1 μm was formed and dried at 40 ° C. for 5 hours.

The two substrates were pressure-bonded in opposite directions to form a sample, which was heated to 80 ° C. in a glass heater, and a voltage of 600 V was applied between both electrodes in this state. The electric field strength in this case was 1 MV / cm or more, and the molecules were oriented for 1 hour.

Next, the temperature was raised to 140 ° C. until the voltage was applied, and the epoxy and amine were reacted for 5 hours to form a three-dimensional polymer. The thin film thus obtained has d ₃₃ =
It has a high non-linear optical constant of 30 pm / V, and almost no deterioration in performance was observed even over a month. Example 2: (corresponding to claim 2) In Fig. 7, the polymer represented by the general formula (12) and the monomer represented by the general formula (14) were used.

First, 5 g of both were sampled and mixed at a molar equivalent ratio, and this was dissolved in methyl cellosolve to prepare a 30 wt% liquid. Next, prepare two pieces of polyimide insulating film coated on a 50 mm square glass substrate equipped with a transparent electrode made of ITO, and spin-coat the above solution on this to form a thin film with a thickness of 1 μm. It was made and dried at 40 ° C. for 5 hours.

The two substrates were pressure-bonded in opposite directions to make a sample, which was heated to 80 ° C. in a glass heater, and a voltage of 600 V was applied between both electrodes in this state for 1 hour. The molecules were oriented.

Next, the temperature is raised to 140 ° C. until voltage is applied,
By holding for 2 hours, the epoxy and amine were reacted to form a two-dimensional polymer. Then, the voltage was raised to 1 KV and kept for 1 hour to orient the monomer, and the temperature was raised to 180 ° C. under the condition of voltage application, and the epoxy and the OH group were reacted to form a three-dimensional polymer.

The thin film thus obtained has d ₃₃ = 40 p
It has a high nonlinear optical constant of m / V, and almost no deterioration in performance was observed even for a month. The thin film of the example in which the reaction was stopped in the state of the two-dimensional polymer which was applied with 600 V and kept at 140 ° C. for 2 hours had d ₃₃ = 25 pm / V.

From this, it was found that the organic nonlinear optical material having high orientation and stability over time can be obtained by performing the electric field orientation in two steps.

[0032]

As a result of the practice of the present invention, the orientation relaxation is small,
Also, an electric field oriented polymer having a large second-order nonlinear optical constant can be obtained.

[Brief description of drawings]

FIG. 1 is a general formula of a one-dimensional polymer having an epoxy group in a side chain.

FIG. 2 is a general formula of another one-dimensional polymer having an epoxy group in a side chain.

FIG. 3 is a general formula of a monomer having a second-order polarizability.

FIG. 4 is a general formula of a monomer having two substituents.

FIG. 5 is a general formula of another one-dimensional polymer having an epoxy group in a side chain.

FIG. 6 is a general formula of another monomer having two substituents.

FIG. 7 is a general formula of a polymer and a monomer used in Examples.

Claims (2)

[Claims] 1. A one-dimensional polymer having at least one epoxy group in a side chain, preferably having a secondary molecular polarizability, and at least one substituent having an epoxy group-bonding ability, and An organic nonlinear optical material characterized by mixing a monomer having a second-order molecular polarizability, heating the polymer while applying an electric field to chemically bond the polymer and the monomer, and fixing the molecular orientation of the monomer. Production method. 2. A one-dimensional polymer having at least one epoxy group in a side chain, preferably having a secondary molecular polarizability, and two or more kinds of functional groups having an epoxy group-binding ability but different reactivity. A monomer having a group and having a secondary molecular polarizability is mixed and heated to a predetermined temperature while applying an electric field to obtain a specific functional group of the oriented monomer and the epoxy group of the polymer. After bonding with, the polymer is heated to a predetermined temperature higher than the above temperature while applying a higher electric field to bond the other functional groups of the monomer and the epoxy group of the polymer, and the molecular orientation of the monomer is fixed. An organic nonlinear optical material and a method for manufacturing the same.