JPH0240243B2 - BUNSHIHAIKOSEIHAKUMAKU - Google Patents

Description

[Detailed description of the invention]

(3-1) Industrial Application Field The present invention relates to a molecularly oriented thin film used in nonlinear optical devices, chromism devices, photoelectric conversion devices, etc. in the electronics and optoelectronics fields. (3-2) Prior art Diacetylene compounds are known as extremely unique substances that generate crystalline polymers when exposed to heat, light, or gamma rays, and are used as conductive materials, chromic materials, photoelectric conversion materials, nonlinear optical materials, etc. It is expected that For example, due to nonlinear optical effects,
An ultra-fast switch phenomenon of about 10 ^-12 seconds is predicted,
It is seen as promising for future optical information processing systems. For application in these fields, particularly in the field of nonlinear optics, it is important to process thin films with good crystallinity. Good crystalline thin film, i.e.
Molecularly oriented thin films can also be used as optical waveguides, opening up a wide variety of applications. JP-A No. 59-62608 describes the polymerization of diacetylene monomer thin films prepared by spraying or spinner methods from solutions or suspensions of diacetylene compounds onto substrates, or by vacuum evaporation methods of diacetylene compounds onto substrates. A method is described for producing thin films by. However, thin films obtained from diacetylene compounds by these methods usually have extremely poor crystallinity. For example, there are many defects such as cracks, domain structure, poor stacking, and poor flatness. A method to improve this point and create a single crystal thin film is now available.
Macromolecules 1985, 18 , 2341-2344. This is a method of heating a diacetylene compound above its melting point and applying a shearing force to orient and crystallize it. However, diacetylene compounds may undergo thermal polymerization by increasing the temperature.
It has drawbacks such as incomplete shear orientation and no improvement in crystallinity. On the other hand, many methods have been reported in which diacetylene compounds having a hydrophobic group and a hydrophilic group are accumulated by the Langmire-Blodget method to form a thin film.
However, the thin film obtained by this method also has drawbacks such as having a domain structure, and its crystallinity is not good. (3-3) Purpose of the Invention The present invention provides a fluorine-containing polydiacetylene-based molecular orientation system in which a specific crystal plane is preferentially oriented in a specific direction and is suitable for devices in the electronics and optoelectronics fields such as nonlinear optical devices. The purpose is to provide thin films. (3-4) Summary of the Invention As a result of intensive technical studies, the present inventors found that the general formula R ¹ -C≡C-C≡C-R ² (R ¹ and R ² are phenyl groups or substituted phenyl groups) (However, at least one of R ¹ or R ² is a fluorine-substituted phenyl group.)
In the diffraction pattern obtained by wide-angle X-ray diffraction, the diffraction angle 2θ = 2sin ^-1 (nλ/2d) (n is an integer of 1 or more, n A molecularly oriented thin film characterized by the presence of three or more diffraction peaks corresponding to the following Bragg reflection, where d is a constant indicating the interplanar spacing of the crystal, and λ is the wavelength of X-rays. They discovered this and arrived at the present invention. (3-5) Specific description of the invention [Fluorine-containing diacetylene monomer] The fluorine-containing diacetylene monomer used in the present invention has the general formula R ¹ -C≡C-C≡C-R ² (R ¹ , R ² is
Phenyl group or substituted phenyl group, provided that R ¹ or
At least one of R ² is a fluorine-substituted phenyl group. ). Specifically, R ¹ and R ² are phenyl group, halogen-substituted phenyl group, alkyl group-substituted phenyl group,
Mention may be made of phenyl groups substituted with halogenated alkyl groups. The number of carbon atoms in the alkyl group or halogenated alkyl group substituted on the phenyl group is preferably in the range of 1 to 6. Preferred substituted phenyl groups include 2, 3,
5,6-tetrafluoro-4-n-butylphenyl group, 2,3,5,6-tetrafluoro-4-
(n-pentyl) phenyl group, pentafluorophenyl group, 2-trifluoromethylphenyl group,
Examples include 2,5-bis(trifluoromethyl)phenyl group, 2,4-bis(trifluoromethyl)phenyl group, and 3,5-bis(trifluoromethyl)phenyl group. More preferably, R ₁ =R ₂ and both are diacetylene monomers comprising the above-mentioned fluorine-containing phenyl group. Other comonomers can be added as long as they do not interfere with the invention. Such comonomers include diphenyl diacetylene and the like. The comonomer content is generally 10 mol% or less, preferably 5
It is less than mol%. [Preparation of molecularly oriented thin film] The molecularly oriented thin film in the present invention is produced by forming the aforementioned diacetylene monomer into a thin film by a dry process such as a vacuum evaporation method or by a melt shear oriented crystallization method (Macromolecules 1985, 18 , 2341-2344). It is produced by oxidation and subsequent polymerization. In the case of vacuum evaporation method, it is produced under the following conditions.
The deposition pressure is 10 ^-1 torr or less, preferably 10 ^-2 torr or less. Substrate temperature is below 45℃, preferably 40℃
It is as follows. The evaporation source temperature (temperature of the diacetylene monomer on the evaporation boat) is (Tm-25)°C or less, preferably (Tm-30)°C or less, where Tm is the melting point of the diacetylene monomer. The fluorine-containing diphenyl diacetylene of the present invention is a compound having sublimation properties. By utilizing this property under the above-mentioned controlled conditions, it becomes possible to perform oriented crystallization while depositing on a substrate. The temperature of the board
If the temperature is higher than 45°C, phenomena such as the deposited monomer sublimating again occur, which is not preferable. When setting the evaporation pressure lower, set the evaporation source temperature lower (e.g., (Tm-50)℃ for 10 ^-6 torr,
It is important to control the sublimation rate within the above conditions, such as (Tm - 40) °C for 10 ^-4 torr. Table 1 shows the melting points of typical fluorine-containing diphenyl diacetylene monomers of the present invention.

[Molecular orientation]

In the present invention, molecular orientation can be measured by X-ray wide-angle diffraction, and in the measured diffraction pattern, the diffraction angle 2θ=2sin ^-1 (nλ/
2d) (where d is a constant indicating the interplanar spacing of the crystal, λ is the wavelength of the X-ray, and n is an integer greater than or equal to 1, which corresponds to the n-th order Bragg reflection.) There are three diffraction peaks with the following relationship. The determination is made based on whether or not there are more than one. Specifically, the diffraction peak that is relatively strong in intensity and located at the minimum diffraction angle is set to n=1, and its diffraction angle is set to 2θ ₁ . d ₀ =λ/2sinθ ₁
Find d ₀ from Next, from 2θ=2sin ^-1 (nλ/2d ₀ ), the diffraction angles θ ₂ , θ ₃ , corresponding to n=2, 3, 4...
θ ₄ ... is calculated, and it is determined whether two or more diffraction peaks actually exist at that angle. If the film exists, it is determined that the film is a molecularly oriented thin film in which a specific crystal plane having a crystal spacing d ₀ is oriented with respect to the substrate, and the molecules constituting the crystal are also oriented. Here, the agreement between the calculated value and the measured value of the diffraction angle 2θ is less than ±0.3 degrees,
Preferably it is ±0.2 degrees or less. If there is no diffraction peak, d ₀ is determined from a diffraction peak with a larger diffraction angle, and the presence or absence of a diffraction peak is determined in the same manner. If it is present, it is determined that the crystal plane is oriented. If the crystal system, space group, unit cell constant, and angle between crystal axes are known by crystal structure analysis, calculate d _hkl corresponding to the crystal plane (h, k, l), then d _hkl
The diffraction angles corresponding to n=1, 2, 3, 4... are calculated using The diffraction angle of the actually measured periodic diffraction peak is compared with the calculated value, and the final best fit (h ₀ , k ₀ , l ₀ ) is determined. From this, a specific crystal plane oriented with respect to the substrate (h ₀ ,
k ₀ , l ₀ ), which reveals how the molecules are oriented with respect to the substrate. In the present invention, the upper limit of n is not particularly limited, but if the orientation state is good, n reaches 5th to 10th order. In some cases, there are also orders whose reflection intensity is so small that they are not detected as diffraction peaks. for example,
Although 1st, 2nd, 3rd, and 5th order diffraction peaks are observed, 4
The following cases are not permitted, and such cases are also included in the present invention. In the present invention, the diffraction angle 2θ=2sin ^-1 (nλ/
In addition to the diffraction peaks that periodically exist in 2d), 1
There may be more than one small diffraction peak. In general, these diffraction peaks appear to have extremely low intensities when measured using the powder method, and in general, the intensity of the diffraction peak in a thin film is less than 1/5 of the corresponding diffraction peak intensity when measured using the powder method. If it is preferably 1/10 or less, there is no problem in using it as the thin film of the present invention. Generally, it is desirable that three or more periodically appearing diffraction peaks have higher intensity than other diffraction peaks. Most preferably, all of the measured diffraction peaks constitute a constant diffraction angle equation. The present invention will be explained in detail by examples below.
The present invention is not limited to this. (4) Example (4-1) Example 1 2,2',5,5'- as diacetylene monomer
Tetrakis(trifluoromethyl)diphenyl diacetylene (melting point = 101-102°C) was used. Approximately 10 mg of sample was placed in a tungsten board and evaporation pressure = 4
×10 ^-4 torr, substrate temperature = 25℃, evaporation source temperature = 56℃
A diacetylene monomer thin film was prepared by vapor deposition on well-washed polymethyl methacrylate (PMMA) (15 x 35 mm) under the following conditions. The film thickness was determined to be 0.7 μm by multiple reflection interferometry. A xenon lamp and a bandpass filter (UV-
UV light (240-400nm) obtained using D33S)
was irradiated at 10 mW/cm ² for 10 minutes to polymerize the monomer and produce a red polydiacetylene thin film. The CuK〓 line (λ=
Measurements were made using a reflection diffractometer method using a radiation source of 1.5418 Å). The diffraction pattern is shown in FIG. Among the diffraction peaks, the one having the smallest angle 2θ ₁ =6.71° is set as n=1. From d ₀ = λ/2sinθ _1, d ₀ =
It becomes 13.17Å. Next, find the 2θ corresponding to n=2, 3, 4, 5, 6, 7 from 2θ=2sin ^-1 (nλ/2d ₀ ): 13.44°, 20.22°, 27.08°, 34.03°, 41.12°,
It becomes 48.37°. The actual value corresponding to this calculated value is
13.40°, 20.20°, 27.05°, 34.00°, 41.10°, 48.
The angle is 35°, which is a very good match. The diffraction peak is the diffraction angle
It was found that seven lines exist periodically at 2θ=2sin ^-1 (nλ/2d). Further, in this case, no diffraction peaks other than n=1 to 7 were observed. However, the halo around 13° and 30° is due to the PMMA of the substrate. From the above, it was found that this thin film was a molecularly oriented thin film with extremely excellent crystallinity, in which polydiacetylene molecules were oriented and crystallized in a specific direction with respect to the substrate. Figure 2 shows the visible light absorption spectrum. Peak A is a peak corresponding to a π-π ^* exciton, and peak A' corresponds to a phonon sideband associated with an exciton. The sharpness of the peak indicates the good development of the π-electron role system in this thin film, that is, the good crystallinity. On the other hand, since this absorption spectrum was measured with the light incident perpendicularly to the thin film, it is presumed that the polydiacetylene molecules are oriented parallel to the substrate. (4-2) Comparative Example 1 The same 2,2',5,5'-tetrakis(trifluoromethyl)diphenyl diacetylene as in Example 1 (melting point = 101-102) was used as the diacetylene monomer.
°C) was used. Approximately 10 mg of the sample was placed in a tungsten boat, the evaporation pressure was set to 5 torr, the substrate temperature was set to 25°C, the evaporation source temperature was rapidly heated to 82°C, and PMMA (15
x 35 mm). Under these conditions, the diacetylene monomer did not form into a thin film, but instead adhered only in patches (relatively large islands) on the substrate. From the above, it was found that a molecularly oriented thin film could not be obtained under these deposition conditions. (4-3) Example 2 As a diacetylene monomer, R-C≡C-C
In ≡C-R, R was a 2,3,5,6-tetrafluoro-4-n-butylphenyl group (melting point: 102 to 103°C). Approximately 8 mg of sample was placed in a tungsten boat, and evaporation pressure = 5×
A diacetylene monomer thin film was produced by vapor deposition on PMMA (15 x 35 mm) under the conditions of 10 ^-6 torr, substrate temperature = 25 °C, and evaporation source temperature = 52 °C. Film thickness is 0.6μm
It was hot. This thin film was exposed to ultraviolet light in the same manner as in Example 1.
It was irradiated at 10 mW/cm ² for 12 minutes to polymerize the monomer and produce a blue polydiacetylene thin film. The wide-angle X-ray diffraction pattern of this thin film was measured in the same manner as in Example 1. Figure 3 shows the diffraction pattern. Among the diffraction peaks, the one with the smallest angle 2θ ₁ = 7.95° is n
=1. From d ₀ =λ/2sinθ ₁ , d ₀ =11.12. Next, from 2θ=2sin ^-1 (nλ/2d ₀ ), n=2,3,
Finding 2θ corresponding to 4 and 5 is 15.93°, 24.01°,
They become 32.19° and 40.56°. The actual measured values corresponding to this calculated value are 15.90°, 24.05°, not detected, and 40.70°, which are in excellent agreement. However, the peak corresponding to n=4 overlapped with the halo of PMMA of the substrate and was not detected. Further, no diffraction peaks other than those corresponding to n=1, 2, 3, and 5 were observed. From the above, it was found that this thin film was a molecularly oriented thin film with extremely excellent crystallinity, in which polydiacetylene molecules were oriented and crystallized in a specific direction with respect to the substrate. Figure 4 shows the visible light absorption spectrum. As in Example 1, a sharp peak based on π-π ^* excitons is observed. The sharpness of the peak indicates the good development of the π-electron conjugated system in this thin film, that is, the good crystallinity. On the other hand, since this absorption spectrum was measured by entering the thin film perpendicularly, it is presumed that the polydiacetylene molecules are aligned parallel to the substrate. (4-4) Comparative Example 2 The same diacetylene monomer as in Example 2 was used (melting point 102-103°C). Approximately 20 mg of sample was placed in a tungsten boat, evaporation pressure = 1 torr,
Under the conditions of substrate temperature = 25℃ and evaporation source temperature = 80℃,
Deposited on PMMA (15 x 35 mm). It was deposited on the substrate in a rough state with severe surface irregularities, and did not form into a clean thin film. This material was irradiated with ultraviolet rays in the same manner as in Example 1 to polymerize, and the wide-angle X-ray diffraction pattern was measured. The results are shown in FIG.
By comparison with FIG. 3, it is determined that this is simply a randomly deposited microcrystal. (4-5) Example 3 As a diacetylene monomer, R-C≡C-C
In ≡C-R, a compound in which R is a 2,3,5,6-tetrafluoro-4-(n-pentyl)phenyl group (melting point: 107 to 109°C) was used. Sample approximately 15mg
into a tungsten boat, evaporation pressure = 1×
A well-washed slide glass (15 ^x 35
mm) to produce a diacetylene monomer thin film. The film thickness was 0.75 μm. This thin film has γ
A blue polydiacetylene thin film was produced by irradiating the monomer with 84 Mrad radiation and polymerizing the monomer. The wide-angle X-ray diffraction pattern of this thin film was measured in the same manner as in Example 1.
Figure 6 shows the diffraction pattern. Among the diffraction peaks, the one having the minimum angle 2θ ₁ =7.85° is set as n=1. From d ₀ =λ/2sinθ ₁ , d ₀ =11.26. Then 2θ
=2sin ^-1 (nλ/2d ₀ ), 2θ corresponding to n=2,3
Calculating these results in 15.74° and 23.70°. The measured values corresponding to these calculated values are 15.80° and 23.90°, which are in good agreement. In addition to the main diffraction peaks corresponding to n=1, 2, and 3, small diffraction peaks are observed around diffraction angles of 11.0° and 17.5° (the halo around 25° is caused by glass). However, the intensity of this minute diffraction peak is less than 1/10 of the intensity of the diffraction peak determined by the powder method. From the above, it was found that this thin film was a molecularly oriented thin film with excellent crystallinity in which polydiacetylene molecules were oriented and crystallized in a specific direction with respect to the substrate. (4-6) Example 4 R-C≡C-C≡ as diacetylene monomer
CR in which R is a 2,4-bis(trifluoromethyl)phenyl group (melting point 145-146
°C) was used. Approximately 12 mg of sample was placed in a tungsten boat, evaporation pressure = 5 x 10 ^-6 torr, substrate temperature = 20
℃, evaporation source temperature = 60℃, and deposited on a slide glass (15 x 35 mm) to prepare a diacetylene monomer thin film. The film thickness was 0.7 μm. This thin film was irradiated with ultraviolet light at 10 mW/cm ² for 60 minutes in the same manner as in Example 1, and the monomer was polymerized to produce a blue polydiacetylene thin film. The wide-angle X-ray diffraction pattern of this thin film was measured in the same manner as in Example 1. FIG. 7 shows the diffraction pattern. Minimum angle among diffraction peaks
The one having 2θ ₁ =9.30 is set as n=1. d ₀ =
λ/2sinθ ₁ , d ₀ =9.51. Then 2θ=2sin ^-1
If we calculate 2θ corresponding to n=2 and 3 from (nλ/2d ₀ ), we get 18.60° and 28.05°. The actual measured values corresponding to this calculated value are 18.70° and 28.25°, which are in good agreement. In addition to the main diffraction peaks corresponding to n=1, 2, and 3, small diffraction peaks are observed around diffraction angles of 10.9°, 13.2°, 16.0°, and 22.5°. but,
The intensity of this minute diffraction peak is less than 1/5 of the intensity of the diffraction peak determined by the powder method. From the above, it was found that this thin film was a molecularly oriented thin film in which polydiacetylene molecules were oriented in a specific direction with respect to the substrate and crystallized.

[Brief explanation of drawings]

FIG. 1, FIG. 3, FIG. 6, and FIG. 7 show wide-angle X-ray diffraction patterns in Examples 1, 2, 3, and 4. FIG. 2 and FIG. 4 show visible light absorption spectra in Examples 1 and 2. FIG. 5 shows a wide-angle X-ray diffraction pattern in Comparative Example 2.

Claims (1)

[Claims] 1 General formula R ¹ -C≡C-C≡C-R ² (R ¹ and R ² are
Phenyl group or substituted phenyl group, provided that R ¹ or
At least one of R ² is a fluorine-substituted phenyl group. ), and in the diffraction pattern determined by wide-angle X-ray diffraction, the diffraction angle 2θ=2sin ^-1 (nλ/
2d) (n is an integer greater than or equal to 1 and corresponds to n-th order Bragg reflection, d is a constant indicating the interplanar spacing of the crystal, and λ indicates the wavelength of the X-ray). A molecularly oriented thin film characterized by the presence of more than one molecule.