JPH06294980A - Organic polymer nonlinear optical material - Google Patents

Abstract

PURPOSE:To obtain a nonlinear optical material having the absorption edge in a short wavelength region which is suitable for conversion of wavelength in blue color and having excellent transparency and high nonlinear optical effect by incorporating a specified repeating unit in the main chain. CONSTITUTION:The repeating unit expressed by formula is included in the main chain. In formula, R<1> is an electron attracting group such as carbonyl group, aminocarbonyl group, carboxyester group, R<2> is an electron-donating group such as aryl group, alkoxy group, alkylthio group. By using an org. polymer material having the repeating unit of the specified structure that has an electron attracting group and an electron donating group in same alpha- posiion carbon as the main chain, the dipole moment can be increased by orienting treatment with an electric field. The obtd. material shows excellent nonlinear optical characteristics. The repeating unit has no pi-electron substituent having large electric deviation so that the obtd. material has the absorption edge in a short wavelength region and is amorphous or divided into single domains which gives little scattering loss and has transparency suitable for wavelength conversion in blue color.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer organic nonlinear optical material which exhibits nonlinear optical characteristics by electrolytic orientation.

[0002]

2. Description of the Related Art Polyvinylidene fluoride having ferroelectricity has a hydrogen atom as an electron donating group and a fluorine atom as an attracting group, and has dipole moments of 1.4 Debye and 0.4 Debye, respectively. Further, it is known that the monomer has a permanent dipole moment of 2.1 debye per monomer unit when the bond angle is 108 degrees with tetrahedral. On the other hand, the monomer unit of vinylidene cyanide-based polymer, which is considered to be a ferroelectric material, has a permanent dipole moment of 4 Debye, which is about twice that of vinylidene fluoride, and these polymers are Curie. It is known to have second-order non-linear optical properties by electric field orientation treatment at temperature.

A nonlinear optical material is a material that exhibits a non-linear response of second order or higher and an electro-optical effect under a strong electric field of laser light, such as wavelength conversion, amplification, modulation, ultrafast optical switching, bistable memory, and logic element. Since it brings many element functions such as KDP (KH ₂ PO), it has attracted attention as a basic material for optoelectronics and optical computers.
₄ ), strong inorganic derivatives such as LiNbO ₃ and semiconductors have been developed.

Recently, urea, 2-methyl-4-nitroaniline, methyl- (2,4-dinitrophenyl) -aminopropanate, 3-methyl-4-nitropyridine-1-
It has been found that organic compounds such as oxides far exceed the non-linear response of conventional inorganic compounds, and research and development of organic non-linear optical materials have been attracting attention.

Some organic crystals have a performance index η (η = d ² / n ³ , d: NLO constant, which has a second-order nonlinear optical effect of about 1000 times in the ultraviolet to near infrared region as compared with inorganic crystals.
n: refractive index). It has been confirmed that the photoresponse speed is much faster than that of inorganic crystals because the lattice vibration is not involved, and the threshold value for photodamage is large. However, organic low molecular weight single crystal materials have problems such as unpredictable crystal structure, inability to extract large tensor components, difficulty in obtaining large crystals, and difficulty in processing such as cutting and polishing. There is.

At present, it is required to shorten the conversion wavelength, that is, to change from the conventional green color to blue color. Therefore, it is required to develop a highly transparent organic polymer nonlinear optical material having an absorption edge at a short wavelength. There is. In general, amorphous polymer materials are often used in so-called poled polymers that exhibit a nonlinear optical effect by electric field orientation treatment. In such an amorphous polymer, after electric field orientation,
There is a big problem that the deorientation phenomenon of the alignment is inevitably caused by the thermal relaxation action.

As a polymer material which does not cause the thermal relaxation deorientation, vinylidene fluoride and vinylidene cyanide-based polymers having ferroelectricity are known. It is known that, due to the spontaneous polarization of these materials, the nonlinear optical constants hardly change with time after electric field orientation, even in the case of polymers alone or in the system in which low molecular weight organic dyes are mixed with these polymers.

However, the non-linear optical constant of the polymer alone is too small, and when the organic dye is mixed, the absorption edge shifts to the long wavelength side, which is not suitable for blue wavelength conversion. Therefore, there is a demand for the development of a polymeric organic material that does not include a π-electron-based organic dye structure that is generally used as a nonlinear optical dye and has large nonlinear optical characteristics.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polymer organic nonlinear optical material having an absorption edge in a short wavelength region suitable for blue wavelength conversion, excellent transparency, and exhibiting a high nonlinear optical effect. Especially.

[0010]

According to the present invention, there is provided a polymer organic nonlinear optical material characterized in that it has a repeating unit represented by the following general formula (2) (hereinafter referred to as repeating unit A) in its main chain. Provided.

[0011]

[Chemical 2]

The present invention will be described in more detail below.

The polymer organic non-linear optical material of the present invention is a polymer organic material having a repeating unit A represented by the above general formula 2 in the main chain, which exhibits non-linear optical characteristics. ¹ is a carbonyl group; dimethylaminocarbonyl group; aminocarbonyl group; carboxyl ester groups such as methyl ester carboxy group, ethyl ester carboxy group, tert-butyl ester carboxy group, trimethylsilyl ester carboxy group; carboxylic acid group;
Acetyl group; cyano group; represents an electron-withdrawing group consisting of nitro group, R ² is an aryl group such as benzyl group, phenyl group; alkoxy group such as methoxy group, ethoxy group, tert-butoxy group; methylthio group, ethylthio group , Ter
Alkylthio group such as t-butylthio group; phenylthio group; thioalkoxy group; amino group; N-methyl-N-phenylaminoethyl group, N-methylacetylaminomethyl group, dimethylamino group, diethylamino group, alkylaminocarbonylamino group And the like, a morpholino group, a piperidino group, a trimethylsilyloxy group, an amide group, and an electron-donating group composed of a substituted amide group such as a methylamide group, a propylamide group, and an N-methylpropylamide group.

The electron withdrawing and electron donating properties of R ¹ and / or R ² in the repeating unit A are preferably the same as or higher than those of vinylidene fluoride and vinylidene cyanide, and R ¹ and / or Alternatively, it is preferable that the permanent dipole moment of R ² is the same as that of the vinylidene cyanide unit or about twice that of the vinylidene fluoride unit. Such a polymeric organic material is stable and reacts with various comonomers to obtain a stable copolymer.

The polymer organic material constituting the polymer organic nonlinear optical material of the present invention may be a homopolymer of the monomer constituting the repeating unit A, as long as it has the repeating unit A in the main chain, It may be a copolymer with another monomer, and its molecular weight is preferably 10,000 to 100,000. Further, the content ratio of the repeating unit A in the polymer organic material is preferably 10% or more. When the content of the repeating unit A is less than 10%, it is difficult to impart a desired nonlinear optical effect, which is not preferable.

As the monomer constituting the repeating unit A, CH ₂ ═CR ¹ R ² (wherein R ¹ and R ² are the above
It is the same as R ¹ and R ² in the above. The monomer represented by the formula ()), specifically, a monomer having a combination of R ¹ and R ² shown in Table 1 and the like can be preferably mentioned, and in particular, α-methylthioacrylonitrile, α-methyl methyl acrylate, α- ( Propylamide) methyl acrylate, methyl α-ethylthioacrylate and the like can be preferably mentioned.

[0017]

[Table 1]

Examples of the other monomer copolymerizable with the monomer constituting the repeating unit A include styrene, acrylonitrile, ethyl-α-chloroacrylate, methylmethacrylate, butadiene and methylacrylate. The polymer organic material using such another monomer may be any of a random polymer, a block polymer and a graft polymer.

To prepare the polymer organic material, for example, the report of T. Tanaka et al. (J. Penelle, AB Padias, HK Hal
l, Jr., H. Tanaka, Advances in Polymer Science, Vol.10
2; (Springer-Verlag, 1992) pp73-103.) And the like. Specifically, for example,
Azobisisobutyronitrile (AI) is added to the monomer constituting the repeating unit A and, if necessary, the other monomer.
It can be obtained by a method such as solution polymerization using a radical initiator such as BN). At this time, the polymerization conditions are preferably such that the polymerization temperature is room temperature to 100 ° C. for 1 to 20 hours. Further, the purification can be carried out by a known reprecipitation method or the like.

To prepare the polymer organic nonlinear optical material of the present invention, the polymer organic material having the specific repeating unit A in the main chain is formed into, for example, a thin film, and then electric field orientation is performed. Can be obtained by Specifically, for example, Mortazavi.MA, knoesen, A., Kowel.ST, Higgins.B.
G., Diencs.A., J.Opt.Soc.Am., B-6,733 (1989), etc., on a transparent conductive glass substrate such as ITO, spin coating the polymer organic material solution. After film formation and drying, the polymer organic material is heated to a temperature near the glass transition temperature of 10 to 100 MV / cm, preferably 40 to
20 to 1 while applying a high voltage of about 70 MV / cm
After holding for about 20 minutes, it can be obtained by a method of cooling to room temperature and removing an electric field. When the polymer organic nonlinear optical material is formed into a thin film, the film thickness is preferably 0.1 to 100 μm.

The second-order nonlinear optical constant of the polymer organic nonlinear optical material of the present invention is reported by KDSinger et al. (KDSinge
r, JESohn, SJLalama, Appl.Phys.Lett. 49 .248 (198
6)) polymer electric field orientation and Nd-
It can be measured using a maker fringe method or the like using YAG laser light as a fundamental wave.

[0022]

The polymer organic nonlinear optical material of the present invention is
Since a polymer organic material having a repeating unit of a specific structure having an electron-donating group and an attracting group on the same α-position carbon in the main chain is used, the dipole moment is large by the electric field orientation treatment, and the excellent nonlinearity is obtained. The optical characteristics are shown. Further, the repeating unit does not have a π-electron-based substituent having a large electronic bias, has an absorption edge in the short wavelength region, and is amorphous or has a single domain, so scattering loss is also small. , Has transparency suitable for blue wavelength conversion. Therefore, it becomes possible to obtain blue light with high efficiency by wavelength exchange by various lasers, especially wavelength conversion of red semiconductor laser, which is useful as a practical device material for optoelectronics, and is excellent in such blue transparency. A material exhibiting a second-order nonlinear optical effect can be used as a coherent blue light source using a semiconductor laser by forming a channel and an IC in a polymer waveguide. It can be used as a device for amplification, modulation, and switching, and from a logic circuit using these to a large-capacity, ultrahigh-speed optical computer.

[0023]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

[0024]

Example 1 10 g of methyl α-methoxyacrylate was subjected to a polymerization reaction at 60 ° C. for 5 hours in a solvent of toluene using 0.1 g of azobisisobutyronitrile as a polymerization initiator. The obtained polymer was a homopolymer of R ¹ : COOCH ₃ and R ² : OCH _{3 in} the repeating unit A (Mn = 5.6 × 10 ⁴ ). A thin film substrate was prepared by forming a film of this polymer on a Pyrex glass substrate using a spin coater. When this thin film substrate was sufficiently dried by heating, the film thickness was 1.8 μm. The UV-visible spectrum of the obtained thin film substrate was measured under the trade name "U-best5".
0 "(manufactured by JASCO Corporation), the absorption overlapped with that of Pyrex glass. From this, it was found that the blue transparency of the thin film substrate was sufficient.

Next, in an oven at 100 ° C., the needle electrode side was used as a positive electrode and the brass flat electrode on the back surface of the substrate was used as a negative electrode.
An electric field of MV / cm was applied to the thin film substrate, and after cooling to room temperature, the electric field was removed. Next, while rotating the thin film substrate,
The p-polarized and s-polarized pulse-oscillated Nd-YAG lasers (1.064 μm, 10 mW) are irradiated to generate p
The second harmonic optical intensity of polarized light is measured, and the second-order nonlinear optical constant is calculated from the relative intensity of the second harmonic intensity using the second-order nonlinear optical constant of quartz (d ₁₁ = 0.4 pm / V) as a reference sample. When found, d ₃₃ = 14 pm / V, d ₃₁ = 5.0 pm / V
Met.

[0026]

Example 2 10 g of α-ethoxyacrylonitrile and 5 g of methyl methacrylate were polymerized in the same manner as in Example 1. The polymer obtained was R ² : OC ₂ H ₅ , R ¹ : CN in the repeating unit A, and Mn = 3.2 × 10 5.
⁴ , monomer reactivity ratio r1 = 5.29, r2 = 0.03
Was a comonomer of. A thin film substrate was prepared by forming a film of this comonomer on a Pyrex glass substrate using a spin coater. When this thin film substrate was sufficiently dried by heating, the film thickness was 0.8 μm. When the ultraviolet-visible spectrum of the obtained thin film substrate was measured, the absorption overlapped with the absorption of Pyrex glass. From this, it was found that the blue transparency of the thin film substrate was sufficient. Then, electrolytic orientation was carried out in the same manner as in Example 1 to determine the second-order nonlinear optical constants. D ₃₃ = 8.0 pm / V, d ₃₁ = 2.3 pm /
It was V.

[0027]

Example 3 10 g of α-methylthioacrylonitrile was polymerized in the same manner as in Example 1. The resulting polymer was a homopolymer of R ² : SCH ₃ and R ¹ : CN in the repeating unit A (polymerization rate 92%, Mn = 1.5 × 10 ⁴ ). A thin film substrate was prepared by forming a film of this polymer on a Pyrex glass substrate using a spin coater. When this thin film substrate was sufficiently dried by heating, the film thickness was 1.2 μm. When the ultraviolet-visible spectrum of the obtained thin film substrate was measured, the absorption overlapped with the absorption of Pyrex glass. From this, it was found that the blue transparency of the thin film substrate was sufficient. Then, electrolytic orientation was carried out in the same manner as in Example 1 to determine the second-order nonlinear optical constant. D ₃₃ = 1
6.0pm / V, was d ₃₁ = 4.8pm / V.

Claims (1)

[Claims] 1. A polymer organic non-linear optical material having a repeating unit represented by the following general formula 1 in the main chain. [Chemical 1]