JPH04293573A - Preparation of organic non-linear optical material - Google Patents

Abstract

PURPOSE:To easily prepare a stable and highly reliable membrane of an org. non-linear optical material having a large area and a multilayer structure by an LB method. CONSTITUTION:Monomolecular films 2 composed of a non-linear optically active substance and films 14 composed of a polymerizable substance are alternately accumulated on a substrate 10 by an LB method and the polymerizable substance is polymerized to form a strong and stable polymer membrane. Usually, about three - twenty non-linear optically active films are provided. The polymerizable substance is formed in a single-layer or multilayer structure and irradiated with ultraviolet rays to be polymerized. The outermost layer is formed as the polymerized layer of the polymerizable substance.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is based on LB (Langmuir).
To explain in more detail the method for producing organic nonlinear optical materials using the Blodgett method, a monomolecular film of a nonlinear optically active substance and a film of a polymerizable substance are alternately accumulated on a substrate, and then polymerized to form an organic material. The present invention relates to a method of manufacturing a nonlinear optical material.

0002

2. Description of the Related Art In order to produce organic nonlinear optical materials, a method is generally employed in which a nonlinear optically active substance is dissolved in a solvent, aligned by applying an electric field, and then recrystallized. However, this method has the drawback that some substances may not crystallize, or even if they do crystallize, they may form needle-like minute crystals, making it difficult to obtain large, high-quality crystals.

[0003] Recently, L
Attempts have been made to utilize the characteristics of method B to produce organic nonlinear optical materials. In the LB method, a stable monomolecular film is formed on the water surface using film-forming molecules with an appropriate balance of hydrophilic and hydrophobic groups, then transferred to the surface of a substrate, and the process is repeated to form a monomolecular film. This is a method of producing a thin film called an LB film by accumulating them. LB films have a stable Y-type structure (if the substrate surface is hydrophobic, layers with the hydrophobic groups facing the substrate and hydrophilic groups facing outward, and layers with the opposite orientation stacked alternately) ) is common. In this Y-type structure, the bilayer is a unit and has inversion symmetry. Therefore, in a normal homofilm made of monomolecular layers of all the same type of nonlinear optically active substance, the nonlinear optical effects in each layer cancel each other out. However, this problem can be solved by creating an alternating heterostructure (for example, a structure in which monolayers with nonlinear optical activity and monolayers without nonlinear optical activity are alternately accumulated).

0004

[Problem to be solved by the invention] By forming an alternating heterostructure in which substances with and without nonlinear optical activity are alternately accumulated, it is possible to produce a nonlinear optical effect as a whole film. In practical terms, it is important to fix the crystals of nonlinear optically active substances and maintain the film stably so that the alignment is not impaired. However, in the prior art, this point is not particularly considered. Therefore, there was a problem in that it was difficult to increase the membrane area or create a multilayer structure.

An object of the present invention is to provide a method for producing an organic nonlinear optical material that can solve the problems of the prior art as described above and easily realize a stable film with a large area and multilayer structure.

[0006]

[Means for Solving the Problems] As shown in FIG. 1, the present invention consists of alternately depositing a monomolecular film 12 of a nonlinear optically active substance and a film 14 of a polymeric substance on a substrate 10 by the LB method.
This is a method for producing an organic nonlinear optical material, in which the polymerizable substance is polymerized to form a strong and stable thin film. Note that, contrary to FIG. 1, a configuration may be adopted in which a film of a polymerizable substance and a monomolecular film of a nonlinear optically active substance are alternately accumulated so that the film of a polymerizable substance is first located on the substrate. Here, the nonlinear optically active material is, for example, a material that has the effect of optical frequency multiplication (changing the wavelength of laser light to 1/2 or 1/3). Further, a polymerizable substance is a substance that has a polymerizable functional group (double bond or triple bond) and is polymerized by ultraviolet rays, gamma rays, electron beams, etc. to form a polymer.

[0007] The monomolecular film 12 of the nonlinear optically active substance is usually provided with three or more layers and about 20 or less layers. Polymerizable substances may be polymerized and polymerized by irradiating them with ultraviolet rays each time they are formed, but it is better to polymerize and polymerize them at once by irradiating them with ultraviolet rays after they have been accumulated into multiple layers. Practical and easy to work with. The layer of the polymerizable substance may have a structure in which a plurality of monomolecular layers are accumulated, but the layer of the nonlinear optically active substance must necessarily be a monomolecular layer sandwiched between the polymerizable substances. The outermost layer is preferably a layer of polymerizable material.

[0008]

[Operation] By the LB method, each film-forming molecule is arranged uniformly to form a thin film. The monolayers of nonlinear optically active material are placed alternately between the polymerizable materials, so that the nonlinear optical effect in each monolayer is not impaired. The polymerizable substance is then irradiated with ultraviolet rays or the like to polymerize and form a polymer film, fixing the crystals of the nonlinear optically active substance and stabilizing the film.

[0009]

[Example] When the nonlinear optically active substance is A and the polymerizable substance is B, ABAB... or BAB is formed as an LB film on the substrate.
The monomolecular layers are accumulated in order so that A... is obtained. The substrate on which the LB film is deposited is glass, quartz, silicon wafer, etc., and the surface of these is preferably either completely hydrophilic or hydrophobic.

Examples of nonlinear optically active substances include p-nitroaniline derivatives containing a long-chain alkyl group (having 15 or more carbon atoms) in the side chain. Examples are shown in Chemical Formulas 1 to 3.

[Chemical formula 1]

[Case 2]

[Chemical 3]

As the polymerizable substance, there is a long-chain carboxylic acid (with 15 or more carbon atoms, n=20, ω-tricosenic acid) containing a polymerizable functional group at the end of the hydrophobic chain, as shown in Chemical Formula 4.

[C4]

In addition, substances containing a polymerizable functional group in the side chain and having 15 or more carbon atoms, such as long-chain acrylic acid shown in Chemical Formula 5 (α-octadecyl acrylic acid when n=17), long-chain acrylic acid shown in Chemical Formula 6, chain vinyl acrylate (n=17, octadecyl acrylate), long chain diyic acid shown in chemical formula 7 (n=13,
m=8, heptacosal-10,12-diynoic acid), etc.

[C5]

[C6]

[C7]

[0013] The layers of the polymerizable material are polymerized layer by layer by irradiation with ultraviolet rays, gamma rays, or electron beams after each layer has been accumulated or after all layers have been accumulated.

[0014] In the thin film thus obtained, two types of layers, a polymer layer in which layers of a polymerizable substance are polymerized and a layer of a nonlinear optically active substance, are stacked alternately for each monomolecular layer. The number of layers to be accumulated depends on the properties of the nonlinear optically active material used and the necessary nonlinear optical properties, but at least three or more layers of the nonlinear optically active material are used. Further, considering the advantage as a thin film, the number of nonlinear optically active material layers is usually up to about 20, but the number may be more than this. The first layer on the substrate side may be a layer of a nonlinear optically active substance or a polymer layer (
It may be a layer in which a polymerizable substance is polymerized to form a polymer, but the outermost layer is preferably a polymer layer in order to provide film strength.

[0015]

Effects of the Invention In the present invention, the film-forming molecules are uniformly arranged by the LB method, and the monomolecular layers of the nonlinear optically active substance are accumulated alternately between the polymerizable substances, so that each monomolecular layer is oriented in the same direction. As a result, the nonlinear optical effect is not impaired. Then, by irradiating it with ultraviolet rays or the like, the polymerizable substance is polymerized and becomes a polymer film, so that the crystals of the nonlinear optically active substance are fixed and the film is stabilized. As a result, according to the present invention, a thin film of a stable and highly reliable organic nonlinear optical material having a large area and a multilayer structure can be easily realized.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing the principle of thin film formation by the LB method according to the present invention.

[Explanation of symbols]

10 Substrate 12 Monomolecular film of nonlinear optically active substance 14 Film of polymerizable substance

Claims (3)

[Claims] 1. An organic nonlinear optical material, characterized in that a monomolecular film of a nonlinear optically active substance and a film of a polymerizable substance are alternately accumulated on a substrate, and the polymerizable substance is polymerized to form a polymer. manufacturing method. [Claim 2] The polymerizable substance has a polymerizable functional group,
2. The manufacturing method according to claim 1, wherein the material is a substance that is polymerized and polymerized by ultraviolet rays, gamma rays, or electron beams. 3. On the substrate, a nonlinear optically active film and a polymer film are alternately accumulated for each monolayer, and there are three or more layers of nonlinear optically active films, and the outermost layer is a polymer film. organic nonlinear optical materials.