JP2820486B2 - Material for forming LB film and organic nonlinear optical thin film element using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel material capable of forming a homogeneous LB film and an organic nonlinear optical thin-film element using the same, and particularly to a film alone. An LB film forming material which can improve the film quality of the LB film by being mixed with an aromatic functional LB film forming material which is difficult to form, and an organic non-linear optical thin film element formed using this material It is about.

(Prior Art) Conventionally, Langmuir Blodget (Langmuir jet) has been used as one method of producing a thin film in which the orientation of organic molecules is controlled.
The ir-Blodgett method is known. For a detailed description,
For example, it is disclosed in a literature ("LB film and electronics", edited by Kiyonari Fukuda, published by CMC (1986)). The outline is as follows.

When an amphipathic molecule having a hydrophilic functional group at one end of a long hydrophobic alkyl group is floated on the water surface and an appropriate pressure is applied from the lateral direction (the direction along the water surface), the hydrophilic group comes into contact with the water surface To form a monomolecular film.

Next, a fixed substrate (for example, a glass substrate) is immersed in water across the monomolecular film, and then the substrate is pulled up, whereby the monomolecular film is transferred onto the substrate. By repeating this operation, an accumulated monomolecular film can be obtained.

According to the LB method, a thin film of a material in which a long alkyl chain is bonded to a functional organic molecule (generally, an aromatic molecule including a benzene ring or the like) can be formed into a thin film. Optical devices, sensors, and the like can be manufactured.

Even when producing organic nonlinear optical thin film elements, this LB
The law is used. For example, an organic compound in which a long-chain alkyl group is introduced into p-nitroaniline, which is known to have a large nonlinear polarizability of the molecule, the molecule is made amphiphilic, a thin film is formed from this material by the LB method, and the orientation of molecular polarization is controlled. Attempts to produce a functional organic thin film (Japanese Patent Laid-Open No. 62-39827).

(Problems to be Solved by the Invention) However, an aromatic functional LB film forming material such as a compound in which a long-chain alkyl group is introduced into p-nitroaniline forms a stable monolayer alone. There are many things that are difficult to do.

Therefore, when an LB film is manufactured using such an aromatic functional LB film forming material, the LB film forming material composed of a long chain fatty acid such as arachiic acid is mixed with the material to form the LB film. A film was being made.

However, in this case, since the interaction between the aromatic molecules is strong, the compatibility between the aromatic molecules and the fatty acid is poor, and the aromatic molecules may form an aggregate. For this reason,
There are problems such as difficulty in forming a uniform LB film and difficulty in forming a uniformly molecularly oriented LB film. Actually, in the LB film-forming material obtained by mixing N-stearyl-2-methyl-4-nitroaniline obtained by introducing a long-chain alkyl group into p-nitroaniline and arachinic acid, only p-nitroaniline is present on the water surface. It has been reported that it has been difficult to form a stable monomolecular film due to aggregation of three-dimensional microcrystals (for example, literature: Japanese Journal of Applied Physics (Japa)).
nese Journal OF Applied Physics) Vol.27, No.9 (198
8.9) pp. 1635-1637).

This application has been made in view of such a point, and accordingly, an object of the first invention of this application is to provide an LB film forming material having good compatibility with an aromatic functional LB film forming material and It is an object of the present invention to provide a novel LB film forming material which enables a uniform LB film to be formed by using a material.

It is a further object of the second invention of this application to provide an organic nonlinear optical thin film element having a homogeneous thin film without aggregation.

(Means for Solving the Problems) In order to achieve the object of the first invention of the present application, the LB film forming material of the first invention is constituted by a substance represented by the following formula (1). (Where n in equation (1)
Is an integer from 12 to 28).

Also, in order to achieve the object of the second invention of this application,
In the organic nonlinear optical thin film element of the second invention, a plurality of monomolecular films composed of a compound represented by the following formula (2) and a compound represented by the following formula (3) are accumulated. It is characterized by having a thin film structure (however, n in the formula (2) is an integer of 12 to 28, and m in the formula (3) is an integer of 13 to 29).

The term “accumulation” used herein refers to not only the case where only a monomolecular film composed of the compound represented by the above (2) and the compound represented by the formula (3) is accumulated, but also The case where an intermediate film is interposed between the monomolecular films to improve the film forming property is also included.

(Function) As is clear from the experimental results described later, the material for forming the LB film of the first invention can provide a good LB film by itself, and can also provide an aromatic functional LB film. When used together with the forming material, it contributes to improving the film quality of the formed LB film.

Further, the organic nonlinear optical thin film element of the second invention includes a compound in which a long chain is introduced into p-nitroaniline, which is known to have a large nonlinear polarizability of a molecule, and a compound of such a compound.
When the LB film is formed, the structure has a thin film structure including the LB film forming material of the first invention, which has an effect of improving the film quality, so that a non-linear optical element in which the arrangement orientation of molecules is controlled is described later. As is clear from the experimental results, a remarkable nonlinear optical effect of emitting light corresponding to the second harmonic of the light incident thereon is exhibited.

(Examples) Hereinafter, with reference to the drawings, examples of the LB film forming material of the first invention, and examples of the nonlinear optical thin film element (hereinafter, may be abbreviated as an organic thin film element) of the second invention. Will be described respectively.

Description of LB film forming material First, an example of the LB film forming material of the first invention will be described.

<-> Synthesis of LB film forming material First, as an example of the organic compound represented by the above formula (1), p- represented by the following formula (4) where n in the formula (1) is 17 is as follows. An example of a method for synthesizing stearylaminophenylacetic acid (hereinafter sometimes abbreviated as SAPAA) will be described.

However, it should be understood that the chemicals used, numerical conditions, treatment methods, and the like described in the following synthesis examples are merely examples.

First, 7.55 g (0.05 mol) of p-aminophenylacetic acid,
25.0 g (0.075 mol) of stearyl bromide and 4.2 g of sodium hydrogen carbonate are dissolved in 100 ml of hexamethylphosphoric triamide, and then reacted at a temperature of 100 ° C. for 7 hours. Then, after allowing it to cool to room temperature, the reaction mixture is added to 1 water. At this time, a precipitate is formed. The precipitate is collected by filtration, washed with water, and then dried to obtain a crude product. Next, the crude product is washed by suspending it in hexane and then recrystallized from ethanol for purification.

The organic compound thus synthesized is identified by elemental analysis and infrared absorption spectrum, respectively.

 The results of the elemental analysis were as shown below.

C: 77.12% H: 11.14% N: 3.39% The calculated values are C: 77.37, H: 11.24, and N: 3.47.

The measurement result of the infrared absorption spectrum shows that the wave number 29
Absorption of methylene group around 00 cm ^-1 , absorption of amino group around 3400 cm ^-1 wave number, absorption of carboxyl group around 1700 cm ^-1 ,
Absorption of the aromatic ring was observed at around each of the wave numbers of 1600 and 1500 cm ^-1 .

<-> Preparation of LB Film (Part 1) Next, a plurality of monolayers of SAPAA synthesized as described above are laminated by the LB method.

In this lamination, first, a surface pressure-area curve of SAPAA is measured to evaluate the characteristics of the developed film.

The subphase aqueous solution contains 4 × 10 ⁻⁴ mol / mol of cadmium chloride (CdCl ₂ ) and 5 × 1 mol of potassium hydrogen carbonate (KHCO ₃ ).
0 ^-5 mol / include and shall water temperature to a pH of 6.8 was set to 20 ° C.. The sample was prepared by adding 2.5 × 10 SAPAA to chloroform.
Dissolve at a concentration of ^-3 mol /. Then, the sample is developed in a subphase aqueous solution to form a developed film on the water surface.

Fig. 1 shows the SAPA plotting the area of the developed film (Å ² / molecule) on the horizontal axis and the surface pressure (dyn / cm) of the developed film on the vertical axis.
It is a surface pressure-area curve of A. As can be understood from FIG. 1, since SAPAA exhibits a surface pressure-area characteristic having a steep slope, it is understood that a condensed film can be formed.

Next, with the surface pressure of the SAPAA development film kept constant at 30 dyn / cm, the SAPAA development film is accumulated on the quartz glass plate by the vertical immersion method of the LB method to form a cumulative film. Whether or not the accumulation has been performed successfully can be evaluated by the ratio of the area of the quartz glass substrate crossing the water surface to the decrease in the area of the spread film on the water surface at that time (referred to as the accumulation ratio). SAPAA
The accumulation of the developed film was successfully performed at an accumulation ratio of 1.

<−> Preparation of LB Film (Part 2) Next, an LB film is prepared using SAPAA together with an aromatic functional LB film forming material. Here, aromatic functional LB
In the case of this example, N-stearoyl-p-nitroniline represented by the following formula (5) (hereinafter, referred to as a film forming material)
It may be abbreviated as sto-pNA. ) Is used.

An example of the synthesis of sto-pNA will be described later in the section of Examples of the organic thin film element of the second invention.

As the subphase aqueous solution, the one used in the above-mentioned-section is used. In addition, the mixing ratio (molar ratio) of sto-pNA and SAPAA was 1: 0 (that is, sto-pNA alone), 2: 1, 1: 1, 1: 2,
A plurality of samples are prepared by changing the ratio to 1: 4. The sample was prepared using chloroform.

Next, the surface pressure-area characteristics of each sample are measured.
FIG. 2 is a surface pressure-area curve of the developed film of each sample, with the horizontal axis representing the area of the developed film (Å ² / molecule) and the vertical axis representing the surface pressure (dyn / cm) of the developed film. is there. Here, in FIG. 2, I is that of a developed film of sto-pNA alone, and II is sto-pNA.
Spread film with a mixture ratio of 2: 1 with SAPAA, III with a 1: 1 spread film, IV with a 1: 2 spread film, V with a 1: 4 spread film It is. As can be understood from FIG. 2, st
It can be seen that in the case of o-pNA alone, the developed film is unstable.
In other words, the surface pressure rises as the developed film is compressed (as the area of the developed film is reduced). At a certain pressure (where the area is slightly smaller than 30 面積² / molecule), the surface pressure decreases. Can be seen. This indicates that the collapse of the developed film or a sudden change in the structure of the developed film has occurred. On the other hand, since any of the developed films mixed with SAPAA shows a characteristic having a steep slope, it is understood that a condensed film can be formed.

Next, for a sample in which the mixing ratio of sto-pNA and SAPAA was 1: 1, the surface pressure of the developed film was kept constant at 30 dyn / cm, and the sample was vertically immersed in a quartz glass plate by the LB method. The development film is accumulated by the method to form an accumulation film. This accumulation was successfully performed at an accumulation ratio of 1.

Further, for a sample in which the mixing ratio of sto-pNA and SAPAA is 1: 1, the cumulative number is variously changed to form a cumulative film. Then, an absorption spectrum is measured for each of the cumulative films having different cumulative numbers. FIG. 3 shows the wavelength for each cumulative film with the cumulative number changed.
FIG. 3 is a characteristic diagram in which absorbance with respect to light of 310 nm is plotted with respect to a cumulative number. The reason for using light with a wavelength of 310 nm is that
This is because this accumulated film has an absorption peak at this wavelength (see FIG. 6). As can be understood from FIG. 3, since the absorbance increases in proportion to the cumulative number of the cumulative films,
It can be seen that the accumulation of the developed film is performed well.

In addition, for a sample in which the mixing ratio of sto-pNA and SAPAA is 1: 1, 60 developed films are accumulated on a quartz glass substrate by the vertical immersion method of the LB method. Next, the dichroism of the absorption spectrum of the accumulated film is measured. FIG. 4 is an absorption spectrum showing the measurement results of the dichroism of the accumulated film, with the absorbance on the vertical axis and the wavelength on the horizontal axis. In FIG. 4, the characteristic diagram indicated by A is the absorption spectrum of the accumulated film with respect to the polarized light parallel to the immersion direction of the substrate when the accumulated film is formed, and the characteristic indicated by B is the polarized light perpendicular to the immersion direction of the substrate. FIG. As shown in FIG. 4, this accumulation film shows a remarkable dichroism in the absorption spectrum, and it is understood that the film is a film in which molecules are well oriented.

Further, when the above-described accumulated film obtained by accumulating 60 layers of the developed film was observed with the naked eye, it was found that light scattering was not observed and uniform transparency was exhibited. Further, when the accumulated film was observed with a scanning electron microscope, it had a flat surface and no aggregate was observed.

<-> Preparation of LB film (Comparative Example) Next, SAPA was used as an LB film forming material used with sto-pNA.
Using arachiic acid as a fatty acid instead of A, a cumulative film of a comparative example is prepared as described below.

As the subphase aqueous solution, the one used in the above-mentioned-section is used. The mixing ratio of sto-pNA and arachiic acid is 1:
A sample is prepared as 1 (molar ratio). The sample was prepared using chloroform.

After developing this sample in the above-mentioned subphase aqueous solution, the surface pressure of this developed film was kept constant at 30 dyn / cm in the same manner as in the example, and 60 layers of the developed film were accumulated on the quartz glass substrate by the vertical immersion method of the LB method. Let it. The dichroism of the absorption spectrum of the thus-prepared cumulative film of the comparative example is measured in the same manner as in the example. FIG. 5 shows the measurement results. In FIG. 5, the characteristic diagram indicated by A is the absorption spectrum of the accumulated film with respect to the polarized light parallel to the immersion direction of the substrate when the accumulated film is formed, and the characteristic indicated by B is the polarized light perpendicular to the immersion direction of the substrate. FIG. In the cumulative film of the comparative example,
As shown in FIG. 5, little difference was observed between the absorption spectra for the polarized light parallel and perpendicular to the immersion direction of the substrate. This indicates that the cumulative film of the comparative example has no in-plane anisotropy.

Next, the compound represented by the above formula (2) (that is, (1)
(The LB film forming material of the first invention represented by the formula) and (3)
An embodiment of the organic nonlinear optical thin film element according to the second invention, which has a thin film structure in which a plurality of monomolecular films composed of the compound represented by the formula are accumulated.
The compound represented by the formula (2) in the embodiment of the second invention is the same as the SAPAA synthesized in the embodiment of the first invention.
Is used.

<-> Synthesis Example of Compound Example of Formula (3) First, as an example of the organic compound represented by the above formula (3), N stearoyl-p- in which m in the formula (3) is 16 is shown.
An example of a method for synthesizing nitroniline (abbreviated as sto-pNA represented by the above formula (5)) will be described. However, it should be understood that the names of chemicals used, numerical conditions, treatment methods, and the like described in the following synthesis examples are merely examples.

First, 6.9 g (0.05 mol) of p-nitroaniline is dissolved in 150 ml of tetrahydrofuran (THF), and 18.2 g (0.06 mol) of stearoyl chloride is added dropwise while stirring this solution. Then, triethylamine (TEA) 3.9 was added to the solution.
After the dropwise addition of g (0.06 mol), the mixture is further stirred for 30 minutes. Next, the formed precipitate (TEA-HCl) is filtered off, and the filtrate is concentrated to dryness. This is heated and dissolved in 300 ml of ethanol, filtered hot, allowed to cool, and the resulting precipitate is collected by filtration. The precipitate obtained by filtration is dissolved in 300 ml of toluene by heating, and the resulting precipitate is collected by filtration after cooling.

The organic compound synthesized as described above is identified by elemental analysis and infrared absorption spectrum, respectively.

 The results of the elemental analysis were as shown below.

C: 70.78% H: 9.90% N: 6.95% The calculated values are C: 71.25, H: 9.97, and N: 6.92%.

In addition, the measurement result of the infrared absorption spectrum shows that the wave number is 2900.
cm ^-1 near the absorption of the methylene groups, wavenumber 3340cm ^-1, 1680cm ^-1
And absorption of the secondary amide group at 1540 cm ^-1, absorption of the aromatic ring were observed respectively at a wavenumber of 1600 cm ^-1.

<−> Preparation of Organic Thin Film Element Next, a sample in which sto-pNA synthesized as described above and SAPAA were mixed at a molar ratio of 1: 1 was developed in a subphase aqueous solution, and the developed film was formed on a quartz glass substrate. Then, 30 layers are accumulated by the vertical immersion method of the LB method to produce the organic thin film element of the example. In addition, the subphase aqueous solution used in the above-mentioned-section is used.

The absorption spectrum of the organic thin-film element of the example thus manufactured is measured. The measurement results are shown in FIG. 6, in which the vertical axis indicates absorbance and the horizontal axis indicates wavelength. 310n absorption peak
m, and was found to be transparent to light having a wavelength of 400 nm or more.

<-> Measurement of Nonlinear Optical Properties of Organic Thin Film Element of Example Next, the nonlinear optical properties of the organic thin film element produced as described above are confirmed according to the method described below. The nonlinear optical effect is evaluated by optical second harmonic generation (SHG).

First, an apparatus for measuring the presence / absence of harmonic generation is used. In this embodiment, an apparatus as described below is used. FIG. 7 is a block diagram schematically showing the measuring device. It is clear that the measuring device may have another configuration.

In FIG. 7, reference numeral 11 denotes a laser light source that emits laser light. The laser light source 11 in this embodiment is a Nd: YAG pulse laser (wavelength 1064 nm, pulse energy 10 mJ)
Is used. Further, 15 is a spectroscope, 17 is a photomultiplier tube,
19 is a current amplifier, 21 is an integrator, and 23 is a recorder. Reference numeral 25 denotes a synchronization circuit for synchronizing the laser light source 11 and the integrator 21.

In this apparatus, the manufactured organic thin-film element is incorporated into such an apparatus so that the laser light of the laser light source 11 is irradiated from a direction perpendicular to the main surface of the glass substrate of the organic thin-film element in this embodiment (FIG. 7). (See FIG. 7 for an organic thin-film element.)

The principle of the measurement is as follows. Organic thin film element 31
The scattered light is dispersed by the spectroscope 15, and the light is received by the photomultiplier tube 17. The spectroscope 17 has a variable resolution. In this embodiment, the spectroscope 17 sequentially scans at a certain resolution over a wavelength of 300 to 600 nm. And
The spectroscope 15 outputs information (wavelength information) indicating the wavelength band at that time to the recorder 23 each time. Also, the current corresponding to the light received by the photomultiplier tube 17 is amplified by the current amplifier 19,
The averaging process is performed by the integrator 21 synchronized with the laser oscillation, and the data is recorded by the recorder 23. Thus, a scattered light spectrum is obtained.

As a result, it was found that the organic thin film element of the example had a sharp peak at a wavelength of 532 nm. Since the light of this wavelength corresponds to the second harmonic of the laser light wavelength (1064 nm) incident on the organic thin film element, it is understood that the organic thin film element according to the present invention has nonlinear optical characteristics.

Further, with respect to a sample in which the mixing ratio of sto-pNA and SAPAA is 1: 1, several kinds of organic thin film elements are produced by changing the cumulative number of spread films variously. Then, the square root of the SHG intensity observed in each of the organic thin film elements having different cumulative numbers is plotted against the cumulative number. The result is shown in FIG. As can be understood from FIG. 8, it is understood that the cumulative number of the developed films and the square root of the SHG intensity are in a proportional relationship.

An organic thin film element of a comparative example was formed in the same manner as in the example except that arachiic acid as a fatty acid was used instead of SAPAA. Then, for the organic thin film element of this comparative example, the presence or absence of generation of SHG is measured in the same manner as in the example.
However, no SHG was observed in the organic thin film element of the comparative example. However, in the organic thin film element of the comparative example, SHG was generated when heat treatment was applied thereto. The detailed description of the organic thin film element of this comparative example is described in Japanese Patent Application No. 1-243086 of the present applicant.

According to the organic nonlinear optical thin film element of the second invention, LB
It can be seen that a remarkable nonlinear optical effect can be obtained when the film is formed by the method.

In the above, the embodiment of the material for forming the LB film of the first invention and the embodiment of the organic nonlinear optical thin film element of the second invention have been described, but these inventions are not limited to only the above-mentioned embodiment. Instead, various changes as described below can be made.

For example, the above-described embodiment of the first invention employs n in the general formula (1).
Was an example using a compound in which is 17, but the object of the present invention is not attained only by the above-mentioned compound, and n in the range in which an LB film can be formed is 12 to 16, 18
This can be achieved even with the compounds of Nos. To 28.

Further, in the above-described embodiment of the first invention, the material used together with the material for forming the LB film of the first invention is sto-pNA.
The material from which a good LB film is obtained by mixing and using the LB film forming material of the first invention is not limited to sto-pNA, and may be a material containing another aromatic amphiphilic molecule. .

Further, in the embodiment of the second invention, the monolayer composed of SAPAA in which n in the formula (2) is 17 and sto-pNA in which m in the formula (3) is 16 is a multilayer film. The organic thin film element having the thin film structure described above has been described. However, these values of n and m are determined under the condition that a thin film without aggregation is obtained and a desired nonlinear optical effect is obtained, and the values are not limited to these. Although it is not clear, n is a value in the range of 12 to 16, 18 to 28, and m is 13 to 1
5, the same effect as in the embodiment can be expected even if the value is in the range of 17 to 29.

Further, in the embodiment of the second invention, a quartz glass substrate was used for manufacturing the organic thin film element, but this was used only for measuring an absorption spectrum, and the substrate is not limited to this.

(Effects of the Invention) As is clear from the above description, according to the LB film forming material of the first invention of this application, the present invention relates to an aromatic amphiphilic molecule which is difficult to form an LB film by itself. By using a mixture of materials, the orientation of molecules is more uniform and better than before.
An LB film is obtained.

Further, according to the organic non-linear optical thin film element of the second invention of the present application, light corresponding to the second harmonic of the incident light is emitted and a remarkable nonlinear optical effect is exhibited. Therefore, according to the organic nonlinear optical thin film element of the present invention, it is possible to realize elements such as a high-performance light-light conversion element, light modulation element, and optical switch. Further, by applying these elements, it becomes possible to realize a basic element for an optical computer.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a material for forming an LB film of an example, and is a diagram showing a surface pressure-area curve of a developed film of p-stearylaminophenylacetic acid (SAPAA). FIG. FIG. 3 is a diagram provided for explaining a material for forming the LB film of FIG. 3, showing a surface pressure-area curve of each of the developed films in which the mixing ratio of sto-pNA and SAPAA is changed. FIG. FIG. 4 is a diagram for explaining the forming material, showing the relationship between the cumulative number of developed films and the absorbance. FIG. 4 shows the dichroism of the absorption spectrum of the cumulative film using the forming material of the LB film of the example. FIG. 5 is a diagram showing the dichroism of the absorption spectrum of the cumulative film using the material for forming the LB film of the comparative example. FIG. 6 is a diagram showing the absorption spectrum of the organic thin film element of the example. FIG. 7 is a block diagram showing a measuring device used for confirming the nonlinear optical effect, and FIG. And the cumulative number of Hirakimaku,
FIG. 4 is a diagram showing a relationship with SHG intensity. 11 Laser light source 15 Spectroscope 17 Photomultiplier tube 19 Current amplifier 21 Integrator 23 Recorder 25 Synchronous circuit 31 Organic thin film element

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Koyano 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (72) Masakazu Kato 1-7-12 Toranomon, Minato-ku, Tokyo No. Oki Electric Industry Co., Ltd. (58) Fields investigated (Int. Cl. ⁶ , DB name) C07C 229/42 G02F 1/35 CA (STN) REGISTRY (STN) WPI (DIALOG)

Claims (2)

(57) [Claims] 1. A material for forming a thin film (LB film) by a Langmuir-Blodgett method characterized by the following formula (1) (where n in the formula (1) is an integer of 12 to 28) Is). 2. A thin film structure in which a plurality of monomolecular films composed of a compound represented by the following formula (2) and a compound represented by the following formula (3) are accumulated. Characteristic organic nonlinear optical thin film element (where n in the formula (2) is 12 to
Integer of 28, and m in the formula (3) is an integer of 13 to 29. ).