JPH111593A - Thin film of oriented molecule - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject thin film, having an ultrahigh anisotropy of refractive index without absorption of visible radiations and without coloring by specifying the thickness, anisotropy of the refractive index, etc., of a thin film of oriented molecules deposited on a substrate. SOLUTION: This thin film of oriented molecules is obtained by regulating the thickness of the thin film of the oriented molecules deposited on a substrate or an oriented film of a fluororesin on the substrate to >=10 and <=5,000 nm, preferably >=50 and <=1,000 nm and further the anisotropy of refractive index to >=0.5, preferably >=0.55 so as not to have the absorption maximum in a region of 400-800 nm in a light absorption spectrum but have preferably <=1, more preferably <=0.1 absorbance in the range. A conjugated system molecule of a structure represented by formula I (Y is a conjugated system group obtained by binding at least two groups represented by formulae II to IV, etc.) (e.g. a compound of a structure represented by formula V) is preferred as the molecules. The number of the structures constituting the Y is preferably 2-12, more preferably 2-8, especially preferably 2-4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an oriented molecular thin film useful in the field of optoelectronic technology.

[0002]

2. Description of the Related Art Thin films having high anisotropy are expected to have many uses in the fields of optical materials and electronic materials. Depending on the kind of optical or electrical anisotropy generally required, the kind of molecule to be oriented and the required degree of orientation differ. However, in general, a high orientation tends to be preferable in any case. This is because the optical or electrical anisotropy of the thin film, for example, the refractive index anisotropy, dichroism, mobility, etc. is significantly affected by the orientation of the molecules constituting the thin film. Therefore, it is desired to use a highly oriented thin film for each molecule that needs to be oriented depending on the type of anisotropy. However, in general, it has been difficult to obtain such an oriented molecular thin film of highly oriented conjugated molecules.

On the other hand, J. A. C. Wittmann et al. Have shown that an oriented PTFE thin film can be obtained by heating and rubbing polytetrafluoroethylene (hereinafter sometimes referred to as PTFE) on a glass substrate while applying pressure. By using this as a fluororesin alignment film, alkanes, liquid crystal molecules, polymers, oligomers,
It has been reported that an inorganic salt or the like can be oriented [Nature 352, 414
P. (1991)]. By using this technique, a polarizing film or the like having high dichroism in the visible light region can be manufactured and used for a liquid crystal display device to improve the display performance. For example, Andreata et al. Produced a highly oriented thin film of a dichroic dye and showed that it was useful as a polarizing element of a liquid crystal display device (International Patent Application WO 96/07941). Also,
According to this technique, an organic semiconductor can be oriented to form a thin film having a large carrier mobility in a specific direction, and can be applied to an electronic element such as a transistor. For example, Wakita et al. Manufactured an electronic device using a thin film of thiophene oligomer (JP-A-7-206599).

However, a thin film of a conjugated molecule having a very high refractive index anisotropy and no absorption of visible light and no coloring has not yet been known, and these anisotropic thin films have been formed on an oriented PTFE thin film. To obtain a thin film of a conjugated molecule having a high molecular weight is not known.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly oriented oriented molecular thin film having an extremely high refractive index anisotropy. More specifically, an object of the present invention is to provide an oriented molecular thin film of a conjugated molecule having extremely high refractive index anisotropy, no absorption of visible light, and no coloring.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, when certain conjugated molecules are deposited on a fluororesin alignment film, highly oriented alignment molecules are obtained. The present inventors have found that a thin film can be obtained, and that a thin film of a conjugated molecule having high refractive index anisotropy and having no absorption of visible light and having no coloring can be obtained, and the present invention has been achieved. That is,
In the present invention, [1] a thin film in which molecules are oriented is deposited on a substrate, the thickness of the thin film is 10 nm or more and 5000 nm or less, and the refractive index anisotropy of the thin film is 0.5 or more; And 400 nm to 80 nm in the light absorption spectrum of the thin film.
The present invention relates to an oriented molecular thin film having no absorption maximum in a region of 0 nm. The present invention further provides [2] a thin film in which molecules are oriented, which is deposited on a fluororesin oriented film on a substrate [1].
The present invention relates to the oriented molecular thin film described above. Furthermore, the present invention relates to the oriented molecular thin film according to [1] or [2], wherein the molecule [3] is a conjugated molecule having a structure represented by the following general formula (1).

[0007]

Embedded image (Where Y represents the following groups independently of each other at least 2
This is a conjugated group obtained by bonding.

Embedded image

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The oriented molecular thin film [1] of the present invention is a thin film in which molecules are uniaxially oriented and deposited on a substrate, and the thickness of the thin film is 10 nm or more and 5000 nm or less. The preferred thickness of the oriented molecular thin film of the present invention is generally thicker from the viewpoint of forming a uniform thin film without pinholes, and thinner is more advantageous for achieving a high degree of orientation. Therefore, the film thickness is preferably 10 nm or more and 5000 n
m or less, more preferably 50 nm or more and 1000 nm or less.

Further, the oriented molecular thin film of the present invention is characterized in that the thin film has a refractive index anisotropy of 0.5 or more, preferably 0.55 or more. In the present invention, the refractive index anisotropy is defined as a refractive index for linearly polarized light in which the orientation direction of the oriented molecular thin film is perpendicular to the optical axis of linearly polarized light and the orientation direction is within the vibration plane of the electric field of the linearly polarized light ( B1) and the refractive index (B2) for linearly polarized light in which the orientation direction of the oriented molecular thin film is perpendicular to the optical axis of the linearly polarized light and the vibration direction of the electric field of the linearly polarized light is perpendicular to the orientation direction. The wavelength of the linearly polarized light is 589 nm.

## EQU1 ## Refractive index anisotropy = | B1-B2 | (where || represents an absolute value)

The oriented molecular thin film is characterized in that it does not have an absorption maximum in a region of 400 nm to 800 nm in a light absorption spectrum.
The absorbance is preferably 1 or less, more preferably 0.1 or less, in the range of ~ 800 nm,
It is particularly preferred that it is 0.05 or less.

Further, the oriented molecular thin film [2] of the present invention is characterized in that a thin film in which molecules are oriented is deposited on a fluororesin oriented film on a substrate. The fluororesin alignment film can be formed on a substrate by a known method.For example, a method of rubbing a fluororesin against a substrate under heating, a method of rubbing a thin film of a fluororesin or a surface of a film, and the like are preferable. Can be used for Among these various methods, a method of forming a fluororesin thin film by vapor-depositing PTFE from a gas phase on a substrate and rubbing the surface thereof is particularly preferable. The substrate is
Although a smooth material can be used, it is appropriately selected and used depending on the purpose and the method for forming the fluororesin alignment film.
Substrates considered in such selection include glass, polymer films, calcium fluoride, strontium fluoride, sapphire and the like.

In the present invention, the method of depositing molecules on the fluororesin alignment film on the substrate includes a method of depositing the molecules from a gas phase on the fluororesin alignment film on the substrate, and a method including the molecules. A method of applying a melt, a method of applying a solution containing the molecule, and the like can be mentioned, but a method of vapor-depositing the molecule from a gas phase is preferable in that a uniform thin film can be formed.

Next, in the present invention, the molecules deposited on the substrate or on the fluororesin alignment film on the substrate will be described in detail. As the molecule, it is preferable to use a conjugated molecule having a structure represented by the general formula (1) from the viewpoint of increasing the refractive index anisotropy of the obtained oriented molecular thin film. Also,
In this case, it is preferable that the type of the structure constituting Y in the general formula (1) is composed of a paraphenylene group and an acetylene group. If the number of structures constituting Y in the general formula (1) is too small, the orientation of the obtained oriented molecular thin film is not sufficient, and if it is too large, the film is colored. Therefore, the optimum number is appropriately selected and used depending on the individual case, but generally 2 to 12 is preferable, 2 to 8 is more preferable, and 2 to 4 is preferable. Particularly preferred. Specific examples of the conjugated molecule having such a structure include the molecules shown in Table 1, and among them, the compound having the structure of the number (a) is preferable.

[Table 1]

The purity of the conjugated molecule used in the present invention differs depending on the type of the conjugated molecule. Usually, the range of 90 to 100% can be used, preferably the range of 95 to 100%, more preferably the range of 98 to 100%, and particularly preferably the range of 99 to 100%.

The production of an oriented molecular thin film by vapor deposition from a gas phase is performed, for example, by heating a conjugated molecule at a decomposition temperature or lower to sublimate it and deposit it on a substrate provided with a fluororesin oriented film. Therefore, as the conjugated molecule, one that sublimates without being decomposed by heating required for evaporation is used, and it is preferable that the temperature of the evaporation source be equal to or lower than the decomposition temperature of the conjugated molecule. The specific temperature varies depending on the structure of the conjugated molecule. From the general characteristics of conjugated molecules, 400
C. or less, more preferably 300.degree. C. or less. The temperature of the substrate is generally used below the melting point of the conjugated molecule, but is preferably -10 ° C or more and 200 ° C or less or the melting point of the conjugated molecule or less, and 0 ° C or more and 150 ° C or less or the melting point of the conjugated molecule or less. The temperature is more preferably 0 ° C. or higher and 100 ° C. or lower or the melting point of the conjugated molecule or lower.

The degree of vacuum at the time of vapor deposition can be lower than the atmospheric pressure. However, in order to lower the heating temperature of the conjugated molecule and to secure the distance between the evaporation source and the substrate, the vacuum is exhausted as much as possible. Is preferred. Specifically 1
It is preferably 0 ^-5 torr or less.

[0017]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited by these examples. Example 1 <Formation of Fluororesin Alignment Film> PTFE (Molecular weight 5000
２０20000) was deposited on a glass substrate to a thickness of about 50 nm. The surface of this PTFE thin film is chamois leather (5mm ×
20mm), and rubs in one direction.
A TFE alignment film was obtained. At this time, the chamois was pressed against the substrate with a pressure of 5 kg weight and moved at a speed of 5 mm / sec in a direction perpendicular to the long side of the chamois to perform friction. <Formation of Alignment Molecular Thin Film> The compound of the number (a) in Table 1 was deposited on the obtained PTFE resin alignment film. The degree of vacuum at the time of vapor deposition is 10 ⁻⁵ Torr or less. The thickness of the deposited film was about 0.52 μm.

<Evaluation of Refractive Index Anisotropy>
[Tsuruta, Applied Optics II, Baifukan (1991)] 5:19
It was measured by the Senarmont method described in Section 2. Wavelength 589n
The refractive index anisotropy was determined by measuring the retardation at m and dividing by the film thickness measured by a stylus-type surface profiler. As a result of the above measurement, the refractive index anisotropy was 0.6. Further, the obtained thin film was slightly colored white due to scattering, but had no absorption peak at 400 to 800 nm when the absorption spectrum was measured.

[0019]

Industrial Applicability The oriented molecular thin film of the present invention has a very high refractive index anisotropy and is a highly oriented thin film. Further, a thin film having no visible light absorption and no coloring can be obtained. Is big. Thin-film optical elements using this oriented molecular thin film as a polarizing plate or retardation film are extremely thin and lightweight,
And because of its high performance, it has high industrial value.

Claims (3)

[Claims] A thin film having oriented molecules is deposited on a substrate, the thickness of the thin film is 10 nm or more and 5000 nm or less, the refractive index anisotropy of the thin film is 0.5 or more, and 400 nm to 800 n in the light absorption spectrum of the thin film
An oriented molecular thin film having no absorption maximum in a region of m. 2. The oriented molecular thin film according to claim 1, wherein the oriented thin film is deposited on a fluororesin oriented film on a substrate. 3. The oriented molecular thin film according to claim 1, wherein the molecule is a conjugated molecule having a structure represented by the following general formula (1). Embedded image (Where Y represents the following groups independently of each other at least 2
This is a conjugated group obtained by bonding. Embedded image )