JPH0433928A - Production of non-linear optical material - Google Patents

Abstract

PURPOSE:To readily and efficiently obtain the subject stable material having a high non-linear optical constant by applying an electric field or a magnetic field to a noncrystalline polymer at a specified temperature, then carrying out volume relaxation, subsequently cooling to room temperatures and suppressing the relaxation phenomenon. CONSTITUTION:An electric field or a magnetic field is applied to a noncrystalline polymer obtained by dispersing or dissolving a noncrystalline polymer or a low molecule compound in a polymer at a temperature higher than glass transition temperature of the polymer to introduce an asymmetric structure and volume relaxation is then generated at a constant temperature lower than its glass transition temperature. The electric field or the magnetic field is maintained until the specific volume of the polymer approaches its equilibrium specific volume and the polymer is then cooled to room temperatures to fix the asymmetric structure, thus obtaining the objective material. In addition, a polymer containing a non-linear optically active part in the main chain and containing a non-linear optically active part in the side chain is preferable as the above-mentioned polymer.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a method for producing a nonlinear optical material, which is a simple and simple method for producing a nonlinear optical material that suppresses relaxation phenomena and has a stable nonlinear optical constant. The present invention relates to a method for producing an effective nonlinear optical material.

[Prior art] Nonlinear optical materials can generate sum frequency, difference frequency, and
Second harmonic generation (SHG) that converts the wavelength by half, 1
It is a material that exhibits nonlinear optical effects such as third harmonic generation that converts to /3, and negative-order and second-order electro-optic effects. Utilizing such nonlinear optical effects makes it possible to realize various devices essential for the development of optical communication and information processing, such as optical-optical amplification, high-density optical disks, optical switching, and optical memory. For this reason, research and development of various inorganic and organic nonlinear optical materials are being actively conducted both domestically and internationally. In particular, organic nonlinear optical materials have made remarkable progress, and some have even been discovered that exhibit performance two orders of magnitude higher than that of inorganic materials.

However, there are many organic materials for which it is difficult to grow single crystals of high quality and sufficient size. Also,
Even if a single crystal is obtained, it often does not exhibit second-order nonlinear optical effects because its crystal structure has a centrosymmetric structure. Therefore, it is possible to combine a low-molecular compound with a large second-order supramolecular polarizability with a high-molecular compound (polymer) (host-guest nonlinear optical material), or to combine a part of the high-molecular compound (polymer) with a large second-order supramolecular polarizability. Attempts have been made to modify the material with an atomic group having a fine molecular fraction of 8i (polymer-based nonlinear optical material) and control it to have a non-centrosymmetric structure.

One way to control the structure of host-guest-based nonlinear optical materials and polymer-based nonlinear optical materials into non-centrosymmetric structures is to heat the material above the glass transition temperature of the polymer to free the movement of low-molecular-weight compounds and modifying groups. The so-called poling method is often used, in which an electric or magnetic field is applied to orient the materials in one direction, and in this state, the orientation is fixed by cooling below the glass transition temperature.

For example, after dissolving an azo dye in polymethyl methacrylate as a host polymer compound to form a thin film, poling with an electric field was performed to create a non-centrosymmetric structure.
A nonlinear optical constant of 9 esu has been observed. (K,
D, Singer, J, E, 5hon.

and S, J., Lalama, Appl, P.
hys, Lett, 49°248, 1986) Also, JP-A-1-99033 and JP-A-1-1637
No. 26 discloses a nonlinear optical material in which a host-guest material is made into a non-centrosymmetric structure by poling with an electric or magnetic field.

Furthermore, regarding nonlinear optical materials in which a polymer material is made into a non-centrosymmetric structure by poling with an electric field, Japanese Patent Laid-Open No. 63
-312304.

A nonlinear optical material in which such a host-guest material or a polymer material is formed into a non-centrosymmetric structure by poling has excellent processability such as thin film formation and fine patterning, and is a material that can be used to create devices.

[Problems to be Solved by the Invention] Guest molecules and modification groups oriented by poling gradually try to take random directions due to their own thermal vibrations. Since the mobility of surrounding polymers is low in polymers below the glass transition temperature, it is expected that the thermal vibrations of guest molecules and modifying groups will be suppressed and the orientation given by poling will be maintained. A so-called relaxation phenomenon has been observed in which the non-central symmetry is gradually lost in the system, and the nonlinear optical properties are accordingly attenuated. Attenuation of the nonlinear optical constant due to relaxation is at least about 30%, and in severe cases, the nonlinear optical characteristics may be completely lost.

This relaxation phenomenon not only significantly reduces the nonlinear optical constant of the material but also impairs the performance stability of the device, so it is a very serious problem for all nonlinear optical materials that introduce noncentrosymmetric structures by poling. .

Previous attempts have been made to use polymers with high glass transition temperatures as a means of suppressing relaxation phenomena.6 However, in this case the poling also needs to be carried out at higher temperatures.

In general, the effectiveness of polling decreases as the temperature at which it is carried out increases. There is also the problem that dielectric breakdown and thermal decomposition of the material are likely to occur, so this method cannot be said to be a sufficient solution.

The present invention was made to solve the problems of the prior art, and its purpose is to provide a simple and effective method for suppressing relaxation phenomena and producing a nonlinear optical material having stable nonlinear optical constants. The purpose of the present invention is to provide a method for manufacturing a nonlinear optical material.

[Means and effects for solving the problem] The method for producing a nonlinear optical material according to claim (1) applies electric field or In manufacturing nonlinear optical materials by applying a magnetic field to impart a non-centrosymmetric structure, an electric or magnetic field is applied at a temperature above the glass transition temperature of the polymer to introduce a non-centrosymmetric structure, and then a constant temperature lower than the glass transition temperature is applied. Claim (2) characterized in that the electric or magnetic field is maintained until volume relaxation occurs at a temperature of , and the specific volume of the polymer approaches the equilibrium specific volume, and then the non-centrosymmetric structure is fixed by cooling to room temperature. A method for producing a nonlinear optical material is defined in claim (1).
), wherein the amorphous polymer is a polymer containing a nonlinear optically active site in the main chain, the method for producing a nonlinear optical material according to claim (3)
The method for producing a nonlinear optical material according to claim (4), wherein the amorphous polymer is a polymer containing a nonlinear optically active site in the side chain, is the method according to claim (1).
In the method of (5), the amorphous polymer in which the low-molecular compound is dispersed or dissolved in the polymer is a vinyl polymer having a hydrogen-bonding modification group. The law requires claims (4
), wherein the amorphous polymer in which the low-molecular compound is dispersed or dissolved in the polymer is polyvinylcarbazole or a derivative thereof. Term (4
), wherein the amorphous polymer in which the low molecular weight compound is dispersed or dissolved in the polymer is polyvinylpyrrolidone or a derivative thereof. (4
), wherein the amorphous polymer in which the low-molecular compound is dispersed or dissolved in the polymer is polyvinylpyridine or a derivative thereof. (4
The method for producing a nonlinear optical material according to claim (9), characterized in that the amorphous polymer in which the low-molecular compound is dispersed or dissolved in the polymer is polyamide or a derivative thereof. 4
The method for producing a nonlinear optical material according to claim (10), wherein the amorphous polymer in which the low-molecular compound is dispersed or dissolved in the polymer is borisulfone or a derivative thereof.
The method for producing a nonlinear optical material according to claim 11, wherein in the method 1), the low molecular compound to be dispersed or dissolved in the polymer is N-methoxymethyl-4-nitroaniline or a derivative thereof. Claims (
The nonlinear method according to claim 12, wherein in the method of 1), the low molecular compound to be dispersed or dissolved in the polymer is N,N'-bis-(4-nitrophenyl)-methanediamine or a derivative thereof. The manufacturing method of the optical material is described in the claim (
In the method of claim 1), the low molecular weight compound to be dispersed or dissolved in the polymer is N,N'-bis-(4-methoxycarbophenyl)-methanediamine or a derivative thereof. The method for producing a nonlinear optical material is characterized in that, in the method of claim (1), the low molecular compound to be dispersed or dissolved in the polymer is chalcone or a derivative thereof.

The present inventors have already found that volume reduction due to annealing below the glass transition temperature affects the strength of piezoelectricity and remanent polarization when poling polyvinylidene cyanide-vinyl acetate copolymer (Yon
Sun Jo Publishing Shigeru, Miya 1) Smooth layer, "Journal of the Japan Textile Society," Vol. 39, No. 11, p. 451, 1983). The present inventors conducted further intensive research based on this knowledge, and as a result, they arrived at the present invention.

The present invention will be explained in detail below.

The amorphous polymer produced in the present invention or the nonlinear optical material in which a low molecular weight compound is dispersed in the amorphous polymer preferably has a shape suitable for poling by an electric field or a magnetic field. - Numerically, the material is produced in a thin film on electrodes etc. by methods such as spin coding. Since the thickness of the thin film and the strength of the electric or magnetic field applied to the material are inversely proportional, the poling effect is better when the film is thinner, but if it is too thin, dielectric breakdown is likely to occur, so the film thickness should be 0.5 to 100μ.
It is preferable that it be before or after.

In the present invention, when polling is performed using an electric field,
The structure of the electrode is always open-ended. -Although sufficient effects can be obtained with numerical parallel plate electrodes, it is preferable to use the corona poling method if the material is prone to dielectric breakdown. Further, spreading a thin film of an insulating liquid such as silicone oil on the thin film is an effective means for preventing dielectric breakdown.

The corona polling method is described in detail in the paper by MortaZaVi et al.
zavi.

A. Knoesen and S. T. Kow
el, J, Opt, Sac.

Am, a, vol, δ, No, 4.1989)
The first poling carried out at a temperature equal to or higher than the glass transition temperature of the polymer is preferably carried out at a temperature about 5 to 50°C higher than the glass transition temperature, more preferably 5 to 10°C higher than the glass transition temperature. It is preferable that the poling is continued until a sufficient alignment effect is achieved;
It is preferable to do this for about 0 minutes.

In the present invention, poling is performed at a temperature equal to or higher than the glass transition temperature of the polymer, followed by so-called aging in which an electric or magnetic field is maintained at a temperature lower than the glass transition temperature until the apparent volume of the polymer decreases.

The aging temperature is preferably about 2 to 20 degrees Celsius above the glass transition temperature, more preferably about 2 degrees Celsius below the glass transition temperature.
The temperature is ~10°C lower. It is desirable to carry out the aging until the volume of the polymer approaches the equilibrium volume, and the longer the aging is carried out, the greater the effect of suppressing the relaxation phenomenon. -Number 1 to 10
About an hour is preferable.

After aging, cooling the material to near room temperature while maintaining the electric or magnetic field, and then removing the electric or magnetic field is no different from a normal poling operation.

The nonlinear optical material produced by the method of the present invention has a smaller decrease in the nonlinear optical constant due to relaxation than a nonlinear optical material poled by a conventional method.
It has stable and high nonlinear optical constants.

Furthermore, the nonlinear optical constant immediately after the electric field or magnetic field is removed is higher than that of the conventional method, and the method of the present invention is also superior in terms of poling efficiency.

The method of the present invention can be applied to all host-guest materials using an amorphous polymer or a polymer as a host, which introduces a non-centrosymmetric structure by poling.

Amorphous polymers that can exhibit nonlinear optical activity include polymers that have a nonlinear optically active site in the main chain and polymers that have a nonlinear optically active site in the side chain, and the method of the present invention can be applied to either type of polymer. Examples of the former include polybenzimidazole, polybenzothiazole, polybenzoxazole, and epoxy. Examples of the latter include polystyrene derivatives, polyalkyl acrylate derivatives, polyalkyl methacrylate derivatives, polyvinylpyridine derivatives, polyvinyl alcohol derivatives, and the like. Also,
For the purpose of improving nonlinear optical activity, improving thermal and mechanical strength, improving processability, etc., the above amorphous polymers or the above amorphous polymer and a polymer that does not have a nonlinear optically active site are mixed. Blend polymers are also included in the polymer-based materials referred to in the present invention.

In the present invention, host-guest materials using a polymer as a host include systems in which the polymer itself has a nonlinear optically active site, and systems in which the polymer itself does not have a nonlinear optically active site and only the polymer guest low molecular compound is nonlinear. There are optically active systems. As the former polymer, the above-mentioned amorphous polymer capable of exhibiting nonlinear optical activity can be used. on the other hand,
For the latter, amorphous polymers with excellent optical properties such as polystyrene, polyalkyl acrylate, polyalkyl methacrylate, polycarbonate, polyacrylonitrile, and copolymers thereof can be used. In addition, polyvinylpyridine, polyvinylpyrrolidone, polyvinylcarbazole, polyamide, polysulfone, etc. have a hydrogen-bonding polar group in their structure, so their glass inversion temperature is relatively high, and they are susceptible to twin-column properties with highly polar low molecules. It is suitable as a host polymer because it has excellent properties and good optical properties.

Nonlinear optically active low-molecular compounds used in host-guest materials do not necessarily have a large macroscopic nonlinear optical constant d.
However, it is desirable that the supramolecular polarizability β, which is a measure of molecular nonlinearity, be at least 1×10−”esu, preferably at least 10×10−”esu. In addition, when using a host-guest type nonlinear optical material for optical modulation, optical switching, etc. using electro-optic effects, the optical absorption edge of the material is 1 μm or less, preferably 0.7 μm.
Must be less than or equal to Similarly, when used for second harmonic generation, the absorption edge is 0.5 μm or less, preferably 0.3 μm.
Must be less than m. For low-molecular compounds that meet these conditions, rNONLINEROPT[AL
PROPERTIIESOF 0RGANICMOLE
CIILES AND DRYSTALS VOL, I
J(ACADEMIC PRESS, ING, 19
87) is described in detail.

In addition, chalcone and its derivatives that we discovered earlier,
N-methoxymethyl-4-nitroaniline and its derivatives, N,N'-bis-(4-nitrophenyl)-methanediamine and its derivatives, N,N'-bis(4-methoxycarbophenyl)-methanediamine and Derivatives thereof have an absorption edge closer to the short wavelength side and a large β, and are very preferable as guest low-molecular compounds. Regarding the structures of these compounds, chalcone and chalcone derivatives are described in JP-A-63-239427 and JP-A-1-12627.
N-Methoxymethyl-4-nitroaniline and its derivatives are disclosed in Japanese Patent Application No. 63-303712 and Japanese Patent Application No. 63-30.
No. 3713, N,N'-bis-(4-nitrophenyl)-methanediamine and its derivatives are disclosed in Japanese Patent Application No. 1983-20.
8589 and Japanese Patent Application No. 63-219669, N, N'
-Bis-(4-methoxycarbophenyl)-methanediamine and its derivatives are disclosed in Japanese Patent Application No. 1-108119.
, N'-bis-(4-methoxycarbophenyl)-methanediamine are each described in detail in Japanese Patent Application No. 1-175280.

[Examples] Examples of the present invention are shown below, but it goes without saying that these do not limit the scope of the present invention in any way.

Example 1 Poly-4-vinylpyridine/styrene copolymer (styrene content 10no1%) o, ag and N, N'-bis-(
0.2 g of 4-nitrophenyl)-methanediamine was dissolved in dimethylformamide to prepare a 10 wt % solution. When the thermal behavior of a poly-4-vinylpyridine/styrene copolymer-N,N'-bis-(4-nitrophenyl)-methanediamine film prepared from this solution was measured by DSC, it was found that this host-guest material The glass transition temperature of was 98°C.

The same solution was then spin-coded onto a glass substrate coated with ITO on one side to obtain three 6 μm thick transparent films. After applying a voltage of 3.4 kV to these films at 105° C. and performing corona poling for 40 minutes, one film was cooled without aging to fix the orientation. remaining 2
The sheets were aged at 92° C. for 2 hours and 5 hours, respectively, while applying the same voltage as during poling, and then cooled to fix the orientation.

The second-order nonlinear optical constant d of these three films was measured by the manufacturer's fringe method, and the residual rate was determined. The results are shown in Table 1. From this, the effect of suppressing orientation relaxation due to aging was clearly recognized.

Table 1 dl: d constant (pm/V) dr after electric field removal
:d constant (pm/V) residual rate after 120 hours:
d,/d, Polymethyl methacrylate-Disper Red 19 made from this solution
When the thermal behavior of the film was measured by DSC, the glass transition temperature of this host-guest material was 62°C.

Next, the same solution was spin-coded onto a glass substrate coated with ITO on one side to obtain two transparent films with a thickness of 3 μm. After applying a voltage of 3.4 kV to these films at 70° C. and performing corona poling for 40 minutes, IPi was cooled without aging to fix the orientation. remaining 1
While applying the same voltage as during polling at 60'C,
Aging was performed for a certain period of time, and then the orientation was fixed by cooling.

The degree of orientation Φ of Disbird's Red 19 molecules in these two films was measured from the change in absorbance at the maximum absorption wavelength λmax=480 nm, and the residual rate was determined. Here, Φ is a value determined by the following formula.

Φ=0. 5 (3<cos'θ>-1)=1
-A↓ /AO θ: Angle A between the poling direction and the transition moment of the molecule: Absorbance of oriented sample Ao: Absorbance of unoriented sample Note that details regarding this measurement method can be found in the above-mentioned document by Mortazavi et al. is explained in. The measurement results are shown in Table 2. In this system as well, the effect of suppressing orientation relaxation due to aging was clearly observed.

Table 2 ΦI: Orientation degree Φ immediately after electric field removal: Orientation degree residual rate after 120 hours: Φr/Φ, X100 [Effects of the Invention] As detailed above, according to the method for producing a nonlinear optical material of the present invention , it is possible to easily and efficiently produce a nonlinear optical material that suppresses relaxation phenomena and has a stable and high nonlinear optical constant.

Claims (13)

[Claims] (1) When manufacturing a nonlinear optical material by applying an electric or magnetic field to an amorphous polymer or an amorphous polymer in which a low-molecular-weight compound is dispersed or dissolved in the polymer, a non-centrosymmetric structure is imparted to the amorphous polymer. After introducing a non-centrosymmetric structure by applying an electric or magnetic field above the glass transition temperature, volume relaxation is caused at a certain temperature lower than the glass transition temperature, and the electric or magnetic field is applied until the specific volume of the polymer approaches the equilibrium specific volume. A method for producing a nonlinear optical material, which is characterized by holding the nonlinear optical material and then cooling it to room temperature to fix the non-centrosymmetric structure. (2) The method according to claim 1, wherein the amorphous polymer is a polymer containing a nonlinear optically active site in its main chain. (3) The method according to claim 1, wherein the amorphous polymer is a polymer containing a nonlinear optically active site in its side chain. (4) The method according to claim 1, wherein the amorphous polymer in which the low molecular weight compound is dispersed or dissolved in the polymer is a vinyl polymer having a hydrogen bonding modifying group. (5) The method according to claim 4, wherein the amorphous polymer in which the low molecular weight compound is dispersed or dissolved in the polymer is polyvinylcarbazole or a derivative thereof. (6) The method according to claim 4, wherein the amorphous polymer in which the low molecular weight compound is dispersed or dissolved is polyvinylpyrrolidone or a derivative thereof. (7) The method according to claim 4, wherein the amorphous polymer in which the low molecular weight compound is dispersed or dissolved in the polymer is polyvinylpyridine or a derivative thereof. (8) The method according to claim 4, wherein the amorphous polymer in which the low molecular weight compound is dispersed or dissolved is polyamide or a derivative thereof. (9) The method according to claim 4, wherein the amorphous polymer in which the low molecular weight compound is dispersed or dissolved is polysulfone or a derivative thereof. (10) The method according to claim 1, wherein the low molecular compound to be dispersed or dissolved in the polymer is N-methoxymethyl-4-nitroaniline or a derivative thereof. (11) The method according to claim 1, wherein the low molecular compound to be dispersed or dissolved in the polymer is N,N'-bis-(4-nitrophenyl)-methanediamine or a derivative thereof. (12) The low molecular compound to be dispersed or dissolved in the polymer is N,N'-bis-(4-methoxycarbophenyl)
-Methanediamine or a derivative thereof.The method according to claim 1. (13) Claim 1, wherein the low molecular compound to be dispersed or dissolved in the polymer is chalcone or a derivative thereof.
The method described in section.