JPH04348325A - Molecule oriented organic vapor deposition film - Google Patents

Abstract

PURPOSE:To obtain highly oriented molecules including the direction along the substrate plane with little optical loss by vapor depositing a specified org. compd. on a specified buffer layer. CONSTITUTION:On a substrate, there is provided a polymer buffer layer comprising a polyester polymer such as polyethylene terephthalate, etc., or polyimide polymer expressed by formula I which has no optical absorption max. in the visible and near infrared region. This layer is rubbed in one direction with a nylon cloth and the like to obtain the base substrate. Then a diacethylene compd. expressed by formula II is vapor deposited thereon and photopholymerized. By providing the polymer thin film which is almost transparent in visible and near infrared region on the substrate and treating the substrate by rubbing to give the orientation regulating force, the org. molecules vapor deposited on the substrate can be highly oriented including in the direction along the substrate plane when the org. molecule is deposited. Moreover, the base polymer thin film for orientation controlling has no strong absorption in the visible and near infrared region, which means little optical loss.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molecularly oriented organic vapor deposited film used in storage elements, nonlinear optical elements having an optical waveguide structure, etc. in the field of optoelectronics.

0002

BACKGROUND OF THE INVENTION Today, organic materials have been discovered that have properties superior to inorganic materials in terms of functionality, including nonlinear optical effects. These are caused by a non-localized electron system (π electron system) unique to organic molecules. In order to effectively utilize such organic materials as devices,
It is strongly desired to make the film thinner. This is because most organic crystals are molecular crystals with poor formability. Furthermore, since organic molecules generally have low symmetry, the obtained property tensor also has large anisotropy, and in order to maximize these properties, it is desirable to control the orientation of molecules within the thin film. Furthermore, by controlling the molecular orientation within the thin film, it is also possible to reduce scattering loss when formed into an optical waveguide.

[0003] As a method for producing an organic vapor-deposited film with controlled molecular orientation, a polydiacetylene layer is provided on a suitable substrate, and a diacetylene compound is vapor-deposited and photopolymerized on this layer by rubbing. 18470). but,
The polydiacetylene vapor-deposited film obtained by applying this method has a problem in that the degree of orientation defined by the polarization dichroic ratio is only about 20 at most. Furthermore, the polydiacetylene layer after the rubbing treatment has an absorption band around 540 nm in the visible light region, and since this wavelength is different from that of the absorption band of the vapor-deposited film, there is a problem in forming an optical waveguide with low attenuation.

0004

SUMMARY OF THE INVENTION An object of the present invention is to provide a molecularly oriented organic vapor deposited film suitable for memory elements, nonlinear optical elements having an optical waveguide structure, and the like. Specifically, the present invention provides a method for easily forming a vapor-deposited polydiacetylene film having a polarization dichroic ratio of more than 50 and with little light loss due to the underlying polymeric buffer layer.

[0005]

[Means for solving the problem] The above object is to optimize the material of the polymer used for the polymer buffer layer and the structure of the polymer buffer layer in the treatment method applied to the base substrate prior to vapor deposition. This is achieved by

[0006] The substrate in the present invention is a target to which the base substrate treatment described below is applied, and specifically, glass such as quartz glass, soda lime glass, borosilicate glass, lead glass, and polyester Methyl methacrylate, polycarbonate
Optical plastics such as carbonate, and single crystals such as magnesium oxide, barium difluoride, calcium difluoride, magnesium difluoride, and titanium dioxide are used. Among these, glasses whose refractive index can be controlled are desirable.

[0007] These substrates are subjected to a base substrate treatment consisting of forming a polymeric buffer layer on the substrate and rubbing it to form a base substrate suitable for producing a molecularly oriented organic vapor deposited film. Here, by providing a polymer buffer layer on the base substrate, the molecular orientation regulating force imparted by the rubbing effect can be significantly enhanced.

[0008] Furthermore, the reason why a polymer having a light absorption maximum outside the visible/near-infrared light region with a light wavelength of 400 to 1200 nm and which is nearly transparent in these wavelength regions is used for the buffer layer is because of the wavelength range of 400 to 1200 nm. This is to reduce optical loss in the polymer buffer layer portion when the optical waveguide used is formed by this method. Polymers that have a light absorption maximum outside the visible and near-infrared light wavelength range of 400 to 1200 nm include
Polyolefin such as polyethylene, polyvinyl alcohol, nylon 12, nylon 66
, polyamides such as nylon 69 and nylon 6TPA, polyesters such as polyoxycarbonyl-1-ethylene, polyethylene terephthalate, and polybutylene terephthalate, or polyimides described by the general formula, chemical formula 3, etc. used.

[0009]

[Chemical formula 3]

Among them, polymers such as polyethylene terephthalate in which the polyester component accounts for 80 mol% or more, or polyimide components as described by the general formula, chemical formula 3,
A polymer that accounts for 0 mol % or more is suitable because it also has a large effect of enhancing orientation regulating force.

These polymeric buffer layers can be formed on the underlying substrate by spinning or rolling coating a solution of a polyester polymer and then evaporating the residual solvent by heating, or by applying a solution of a polyester polymer by heating to evaporate the residual solvent, or This can be carried out by spin-coating or rolling-coating a monomer solution, which is a raw material, and then heating to evaporate the residual solvent and polymerize. By controlling the solvent, concentration, and coating conditions when applying the polymer solution, the thickness of the polymer buffer layer can be controlled to an appropriate value. Among these, it is particularly desirable to have a film thickness of 400 nm or less, which is shorter than the wavelength of visible light. This is to minimize the influence on the optical waveguide in which the polymer buffer layer provided to enhance the alignment regulating force is formed. This simplifies the waveguide design and Optical loss due to the refractive index distribution can be reduced.

[0012] The rubbing process refers to rubbing the surface of the base substrate treated as described above in one direction with a cloth. The cloth used may be buff cloth, polyester cloth, nylon cloth, etc., but nylon cloth is preferable for the polyester polymer buffer layer, and buff cloth is preferable for the polyimide polymer buffer layer. Using these cloths, friction treatment is performed in one direction.

[0013] An organic compound is vacuum-deposited on the base substrate that has been treated as described above. The organic compound used in the present invention is represented by the general formula (4).

[0014]

[C4]

Vacuum deposition is carried out by placing the above-mentioned substrate in a vacuum chamber with a degree of vacuum of about 10 to the -4 power Pa, and evaporating the above-mentioned compound in a crucible heated by a resistance wire. This is done by laminating layers. The deposition rate is controlled by the temperature of the crucible and the distance between the substrate and the crucible.
It is desirable that the speed is in the range of 0.1 nm/s to 10 nm/s. Further, the temperature of the crucible needs to be kept at 200° C. or lower to avoid decomposition of the compound. It is desirable that the substrate temperature is in the range of 10°C to 40°C. Depending on the molecules to be deposited, the substrate may be cooled to improve adhesion to the base substrate. The thickness of the vacuum-deposited layer is preferably in the range of 100 nm to 10 μm.

[0016] A film in which the diacetylene monomer compound described by the general formula (Chemical formula 4) is vapor-deposited can be made into a polymer film by irradiating the film with ultraviolet light with a light wavelength of around 250 nm during or after vacuum vapor deposition. be able to.

[0017]

[Operation] As described above, the present invention provides a thin polymer film that is almost transparent in the visible and near-infrared regions on a substrate, and then rubs it to impart an orientation regulating force to the substrate. When the organic molecules adhere to the substrate surface, high-order orientation control including the in-plane direction of the substrate becomes possible, making it possible to maximize the characteristics of the organic molecules. Moreover, since the base polymer thin film for orientation control does not have strong light absorption in the visible and near-infrared regions, an organic vapor deposited film with low optical loss suitable for nonlinear optical devices can be obtained.

[0018]

EXAMPLES Next, the present invention will be explained in more detail based on examples.

Example 1 A polyethylene terephthalate thin film having a thickness of 40 nm was provided on a glass substrate by spin coating. 8 in the air
Residual solvent was removed by keeping at 0°C for 1 hour. Thereafter, while maintaining the temperature at 80 DEG C., the surface of the polyethylene terephthalate thin film was rubbed several times in one direction using a nylon cloth to perform a rubbing treatment. A diacetylene monomer compound described by chemical formula 4 with m=4 and n=2 (hereinafter ET
It is abbreviated as CD. ) were laminated by vacuum evaporation to a film thickness of 100 mm.
Monomer films of nm and 400 nm were obtained. This monomer
The membrane has a visible light cut filter and a built-in ultraviolet lamp (2
By irradiating ultraviolet rays from 5W), solid phase polymerization was performed to obtain an ETCD polymer film. The area of the obtained molecularly oriented organic vapor deposited film was 10 square centimeters.

FIG. 1 shows the linearly polarized light spectrum of the obtained polymer film at normal incidence. The measurement was performed by inserting a Glan-Taylor prism (extinction ratio: 10 to the -5 power) in the optical path of a 340-type spectroscopic altimeter manufactured by Hitachi, Ltd. Parallel and perpendicular in the figure indicate that the electric field direction of the linearly polarized light is parallel and perpendicular to the rubbing direction, respectively. Further, the vertical axis of the spectrum in the perpendicular case is expanded five times as much as in the parallel case. From this figure, it can be seen that light absorption associated with excitons specific to the polydiacetylene main chain is strongly observed in the direction in which the polyethylene terephthalate thin film is rubbed. That is, it can be seen that the polydiacetylene molecules within the film are oriented such that the polydiacetylene main chain is parallel to the rubbing direction. In addition, the polarization dichroic ratio defined by equation 1 is the maximum position of light absorption by excitons (1.9 eV)
It was 105 in Japan.

[0021]

[Math 1]

Example 2 A polyimide (Hitachi Chemical Co., Ltd. polyimide-isoindoquinazolinedione) thin film having a thickness of 100 nm was provided on a glass substrate by spin coating. 20 minutes in the air
It was kept at 0° C. for 1 hour to remove residual solvent and allow polymerization. Thereafter, while maintaining the temperature at 200° C., the surface of this polyimide thin film was rubbed several times in one direction using a buff cloth to perform a rubbing treatment. On the substrate subjected to such surface treatment, diacetylene monomer ETCD was laminated by vacuum evaporation to a film thickness of 100 nm and 400 nm.
A monomer film of m was obtained. This monomer film was polymerized in the same manner as in Example 1, and the polarization dichroic ratio was determined. The result is 1
It was 01.

Example 3 A polyethylene terephthalate rubbing film with a film thickness of 400 nm was provided on a glass substrate with a refractive index of 1.52 in the same manner as in Example 1, and a polydiacetylene ETCD film with a film thickness of 1.03 μm was deposited on this. A film was formed. Using a prism coupler,
When light with a wavelength of 1.064 μm was incident on this film, a light waveguide phenomenon was observed.

Comparative Example 1 Using polyethylene terephthalate doped with a bis(chalcogenpyrrolo)methine organic dye having a light absorption maximum in the near-infrared region, a refractive index of 1 was obtained in the same manner as in Example 3. ．．
A polyethylene terephthalate rubbing film with a thickness of 1000 nm is provided on a glass substrate of No. 52, and a polyethylene terephthalate rubbing film with a thickness of 1.
A polydiacetylene ETCD film with a thickness of 0.03 μm was formed. When light with a wavelength of 1.064 μm was incident on this film using a prism coupler, a light waveguide phenomenon was observed, but the optical loss was greater than that of the film of Example 3.

[0025]

As is clear from Examples 1 and 2, by using the present invention, it is possible to effectively obtain a deposited film of a polydiacetylene compound with highly molecular orientation.

Furthermore, as is clear from the comparison between Example 3 and Comparative Example 3, by using the present invention, an organic optical waveguide with low optical loss can be formed.

[Brief explanation of drawings]

FIG. 1: Linearly polarized absorption spectrum of polydiacetylene ETCD laminated on a polyethylene terephthalate rubbed film.

Claims (5)

[Claims] Claim 1: Visible light with a wavelength of 400 to 1200 nm.
It is characterized in that it is obtained by depositing an organic compound on a base substrate obtained by providing a polymeric buffer layer with a light absorption maximum outside the near-infrared light region on a substrate and rubbing this in one direction. Molecularly oriented organic vapor deposited film. 2. In the base substrate treatment according to claim 1, the film thickness of the polymer buffer layer provided on the substrate is 400 nm.
A molecularly oriented organic vapor deposited film characterized by the following: 3. A molecularly oriented organic vapor deposited film characterized in that the polymer buffer layer according to claim 1 or 2 contains a polyester polymer or a polyimide polymer represented by the general formula (1). . [Chemical formula 1] 4. A diacetylene compound represented by the general formula, chemical formula 2, is deposited on a substrate treated by the method according to claim 1, or 2, or 3, and the diacetylene compound is photopolymerized. Features a molecularly oriented organic vapor deposited film. [Case 2] 5. An optical waveguide using the molecularly oriented organic vapor deposited film according to claim 4.