JPH0580370A - Organic functional thin film and its production - Google Patents

Abstract

(57) [Abstract] [Purpose] The objective is to realize organic functional thin films useful as various organic functional materials such as nonlinear optical materials and organic semiconductor materials. [Structure] A polymer obtained by linking a plurality of types of molecules that are bound by a double or triple bond, wherein the polymer has a continuous π electron conjugation length of 10Å or more, or a double or triple bond A polymer obtained by linking a plurality of types of molecules that are bound to each other, wherein a part of the conjugated system between the molecular units involved in the binding is divided by a single bond. This polymer may have a donor property or an acceptor property in at least a part of the molecular unit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic functional thin film and a method for producing the same. The organic functional thin film according to the present invention,
In particular, it can be advantageously used as a nonlinear optical material or an organic semiconductor material.

[0002]

2. Description of the Related Art Conjugated polymers are known as a promising material system for organic functional materials such as nonlinear optical materials and organic semiconductor materials. In order to improve the performance of such materials, it is necessary to realize a long conjugated π-electron system with little disorder. Further, it is necessary to selectively add or dope a donor group or an acceptor group to the conjugated polymer, or to control the conjugated chain length.
Various polymers such as polydiacetylene and polyphenylene vinylene have been developed as conjugated polymers. However, the former has a large optical confusion loss, a low degree of freedom in the molecular structure, and MLD (Molecular Laye).
It was difficult to obtain a high-performance film with little scattering by using this because it is difficult to form a film by the r Deposition) method. Regarding the latter, in addition to the difficulty of film formation by the MLD method, the disorder of the conjugated system is large, the control of the conjugated chain length is difficult, and the control of the donor group and the acceptor group is difficult. there were.

On the other hand, the following equation

[Chemical 1] As shown in, the reaction between the -CHO group and the -NH ₂ group results in 2
It is known that a heavy bond (azomethine bond) occurs. For example, Iijima et al. Have succeeded in thinning a polymer by vapor deposition polymerization using the above reaction (Nikkei New Material, December 11, 1989, 93-101).
page). Further, the present inventors have developed an MLD method capable of molecular arrangement on the order of one molecule (Japanese Patent Application No. 3-13244).
8).

[0004]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems of the prior art.

Therefore, an object of the present invention is to utilize a reaction in which molecules are bound to each other by a double or triple bond so that the disorder of the conjugated system and the variation of the conjugated chain length are small, and the conjugated structure is controlled. It is to realize an organic functional thin film made of a polymer.

Another object of the present invention is to selectively add or dope a donor group or an acceptor group by utilizing a reaction in which molecules are bound by a double or triple bond, or to conjugate chain length. To realize organic functional thin films useful as various organic functional materials such as nonlinear optical materials and organic semiconductor materials, and to realize devices using them.

[0007]

According to the present invention, in order to solve the above-mentioned problems, a polymer obtained by linking a plurality of kinds of molecules which are bound by a double or triple bond,
Provided is an organic functional thin film made of a polymer having a continuous π-electron conjugate length of 10 Å or more.

The polymer is preferably a plurality of --CHO.
It is a polymer in which a molecule having a group and a molecule having a plurality of —NH ₂ groups are alternately bonded, and may be microcrystalline.

According to the present invention, a polymer obtained by linking a plurality of types of molecules which are bound by a double or triple bond, wherein a part of the conjugation system between the molecular units involved in the binding is There is provided an organic functional thin film composed of a polymer separated by a single bond.

Preferably, the single bond is formed by a bond with another molecule of the group contained in at least a part of the plurality of kinds of unit molecules, or includes two or more continuous single bonds. It was introduced by copolymerizing molecules.

According to the present invention, there is further provided a polymer obtained by linking a plurality of types of molecules which are bound by a double or triple bond, wherein at least a part of the molecular unit has a donor property and / or an acceptor property. There is provided an organic functional thin film made of a polymer having:

This donor property is, for example, --NH ₂ ,-N (C
H _{3) 2,} -OCH _3, provided by a donor group such as -OH, also acceptor property, for example, -NO _2, -CN, given by the acceptor group such as -CF _3. Further, this polymer is a polymer obtained by alternately binding molecules having a plurality of —CHO groups and molecules having a plurality of —NH ₂ groups, and may be microcrystalline. Alternatively, this polymer is preferably a polymer in which a part of a conjugated system between molecular units involved in a bond is divided by a single bond, and the single bond is contained in at least a part of the plurality of kinds of unit molecules. It may be formed by a bond with another molecule of the present group or introduced by copolymerizing a molecule containing two or more continuous single bonds.

According to the present invention, in forming the organic functional thin film as described above, the molecules are introduced into a vacuum or evaporated in a vacuum, and are bound and / or polymerized on a substrate to form a thin film. A method characterized by the above is provided.

The organic functional thin film of the present invention comprises a non-linear optical material, an optical waveguide, a p or n type semiconductor, a pn junction and a TF.
It can be used in a wide range for T, light emitting elements and the like.

[0015]

The preferred embodiments of the present invention will be further described below. Examples of molecules useful in obtaining the polymers of the present invention are shown below.

Examples of molecules having a weak donor property or acceptor property or having no such property and having two or more --CHO groups

[Chemical 2]

[Chemical 3]

[Chemical 4]

[Chemical 5]

Examples of molecules having a weak donor property or acceptor property or having no such property and having two or more --NH ₂ groups

[Chemical 6]

[Chemical 7]

[Chemical 8]

[Chemical 9]

Examples of molecules containing two or more consecutive single bonds and having two or more --CHO groups

[Chemical 10]

[Chemical 11]

[Chemical formula 12]

Examples of molecules containing two or more consecutive single bonds and having two or more --NH ₂ groups

[Chemical 13]

[Chemical 14]

[Chemical 15]

Examples of molecules having an acceptor property and having two or more -CHO groups

[Chemical 16]

[Chemical 17]

[Chemical 18]

[Chemical 19]

[Chemical 20]

Examples of molecules having an acceptor property and having two or more —NH ₂ groups

[Chemical 21]

[Chemical formula 22]

[Chemical formula 23]

[Chemical formula 24]

[Chemical 25]

Examples of molecules having a donor property and having two or more -CHO groups

[Chemical formula 26]

[Chemical 27]

[Chemical 28]

[Chemical 29]

[Chemical 30]

Examples of molecules having a donor property and having two or more --NH ₂ groups

[Chemical 31]

[Chemical 32]

[Chemical 33]

[Chemical 34]

[Chemical 35]

Examples of molecules having acceptor and donor properties and having two or more --CHO groups

[Chemical 36]

[Chemical 37]

[Chemical 38]

An example of a molecule having two or more —NH ₂ groups having an acceptor property and a donor property

[Chemical Formula 39]

[Chemical 40]

[Chemical 41]

Further, as described above, examples of the group forming a single bond by the reaction with another molecule include the following.

[Chemical 42]

[Chemical 43]

Now, for example, using a film forming apparatus shown in FIG. 10, terephthalaldehyde (TPA) and paraphenylenediamine (PPDA) are subjected to CVD (Chemical Vapor) under various conditions.
The absorption spectrum of the film formed by the (Deposition) method
This is shown in FIGS. Figure 1 shows the gas pressure of 2 to 10 × 10 ^-3 to
rr, the substrate temperature is 24 ° C., the absorption spectrum of the film is prepared at a rate of 100 to 300 Å / min, and the absorption of the methanol solution of PPDA and TPA is also shown. PPDA or TPA alone is transparent in the visible region. On the other hand, the film shows strong absorption in the region of 500 to 350 nm. From this, it can be seen that a long conjugated bond of 10 Å or more is obtained. Furthermore, as can be confirmed by the sharp absorption peak near 480 nm, the film of the present invention enabled the production of excitons. This also encourages the formation of long conjugated polymers. On the other hand, as shown in FIG. 2, when measuring the absorption spectrum, if the substrate is tilted with respect to the incident light,
When the deposition rate is as high as 100 Å / min, the incident angle θ of light is 0.
Exciton absorption decreases with changes from ° to 45 ° and 60 °. From this, it is understood that when the film formation rate is high, a clean conjugated chain tends to grow parallel to the substrate. On the other hand, when the film is formed at a rate of 20 to 60Å / min as in the case of FIG. 3, conversely, exciton absorption becomes remarkable as the tilt of the substrate increases. Therefore, it can be seen that a clean conjugated system tends to extend in the direction perpendicular to the substrate. As described above, according to the present invention, the orientation can be controlled by the film forming conditions. Incidentally, as in the case of FIG. 4, when the film thickness is thin or the rate is extremely slow at 0.5 Å / min, excitons may hardly appear. Further, when the substrate was cooled to 0 ° C. or lower to form a film, sharp exciton absorption was observed. From these, it can be said that proper film formation conditions are indispensable for the production of conjugated polymers.

In the polymer of the present invention, an example of the polymer in which a part of the conjugated system between the molecular units is divided by a single bond is shown below.

[Chemical 44]

This polymer can be obtained, for example, by binding the following molecules in an appropriate order.

[Chemical 45]

Other examples of such polymers are as follows:

[Chemical 46]

This polymer can be obtained, for example, by binding the following molecules in an appropriate order.

[Chemical 47]

By binding these molecules in an appropriate order, for example, a polymer having a potential well as shown in FIG. 5 can be obtained. Such a polymer is effective not only for producing the quantum effect but also for making the conjugation length uniform.

FIG. 13 is a diagram showing absorption curves measured for an example of the polymer having the quantum well structure according to the present invention. In the figure, (A) shows the measured absorption of each of the molecules constituting the polymer, that is, terephthalaldehyde (TPA), paraphenylenediamine (PPDA) and 4,4′-diaminodiphenyl ether (DDE), and (B) ) And (C) show the absorption of these polymers. The constitution of these molecules is shown in FIG. In (C), the quantum well structure is not formed. -O in (B)
-The bond serves as a barrier, and a quantum well with a length of about 20Å is formed that includes three benzene rings. (C) is a quantum well having a short well length consisting of one benzene ring.
The absorption band shifts to the short wavelength side in the order of (C), (B), and (A). It is considered that this is due to electron confinement by the quantum well.

When the absorption peak due to the difference in the bonding group of the barrier portion of the polymer was measured, the results shown in FIG. 7 were obtained. The linking group is -O-, as shown below.
-S- or instead of - (CH ₂₎ - -S- or by using molecules with - (CH ₂₎ - to be changed. -S-,
_{-O -, - (CH 2)} - in this order, the absorption peak position (reflecting the energy gap) are shifted to a higher energy side, that the order increases the barrier height, electron confinement effect is increased I understand. For the polymer molecule of the present invention as shown in FIG. 5 and as a specific example, the relationship between the length of the well portion and the absorption peak was measured. As shown in FIG. 6, the length was shortened and the peak was blue. The result of shifting (shown by a circle) is in good agreement with the calculated curve of the well potential model.

[Chemical 48]

FIG. 8 schematically shows the cross-sectional structure of the film when the conjugated chain is intentionally divided by a single bond. In the figure, 1 is a conjugated portion (well portion), and 2 is a non-conjugated portion (barrier portion). The orientation of the molecules is not limited to the vertical orientation shown in the figure, but may be horizontal, oblique, or a mixed state thereof.

As a method for forming the above film, there is a conventionally used CVD method. Further, as a further advanced method, there is the previously proposed MLD method. M
The principle of the LD method is shown in FIG. As shown in the figure, according to the MLD method, for example, a layer 4 of molecules having a donor property, a layer 5 of molecules having an acceptor property, and a layer 6 of molecules serving as a barrier are sequentially deposited on the substrate 3 one by one. Can be formed into a film. Needless to say, the kinds of molecules, the stacking order, and the number of stacks are not limited to those shown in the drawings and can be arbitrarily changed.

The MLD method can be carried out, for example, by using a film forming apparatus as shown in FIG. Also,
The CVD method can also be performed by using the same apparatus. This apparatus comprises two K cells 7 for molecular evaporation (with shutters 8) and two monomer gas cylinders or monomer gas supply cells 9 (with valves 10). In this device, the substrate 3 supported by the substrate holder 11 can be heated and cooled, and the electrodes 12 formed on the substrate can be heated and cooled.
A voltage can be applied between and 13. However, electrode formation and electric field application are not always necessary. Further, the film thickness of the polymer film formed on the substrate 3 can be monitored by the film thickness monitor 14, and the substrate temperature can be controlled via the thermocouple 15. Of course, the number of molecular evaporation K cells and monomer gas cylinders or monomer gas supply cells is not limited to the examples. Further, as the film thickness monitoring method, it is desirable to use various methods such as an optical monitor in combination. FIG. 22 shows an example of MLD using TPA and PPDA. 1 by switching valve of gas molecule
Film formation at the molecular layer step is observed on the film thickness monitor. The film formation speed can be changed by the substrate temperature, gas pressure and the like.

As described above, the MLD method is not only very effective because it can form a film on the order of one molecule,
As shown in FIG. 11, it is also effective in improving the flatness of the film. That is, in the conventional method (a), since each molecular chain extends randomly at each place, the surface is likely to be roughened. On the other hand, M
In the LD method (b), each molecular chain extends one molecule at a time, so the surface tends to be smooth.

In the MLD method, the orientation of polymer molecules can be controlled by treating the substrate. For example, as shown in FIG. 12, when the substrate 3 is previously treated with a silane-based surfactant having an amino proton at the terminal, a film on the substrate 3 tends to stand and grow from the substrate. Also, 1,10−
It is known that when a diaminodecane film is formed in advance, the film above it is vertically aligned (Reference 1: A.
Kubono, N. Okui, K. Tanaka, S. Umemoto and T. Saka
i, Thin Solid Films, 199 , 385 (1991)), and using this is one method. These alignment treatment methods are MLD
Not only can it be applied to CVD.

Further, examples of polymers having a donor group and an acceptor group in the polymer of the present invention are shown below.

[Chemical 49]

This polymer can be obtained, for example, by binding the following molecules in an appropriate order.

[Chemical 50]

Other examples of such polymers are as follows:

[Chemical 51]

This polymer can be obtained, for example, by binding the following molecules in an appropriate order.

[Chemical 52]

Still other examples of such polymers are as follows:

[Chemical 53]

This polymer can be obtained, for example, by binding the following molecules in an appropriate order.

[Chemical 54]

FIG. 15 is a schematic drawing of the cross-sectional structure of the film when the conjugated chain is intentionally divided by a single bond.
In the figure, 16 is a conjugate portion (well portion), and 17 is a non-conjugation portion (barrier portion). In this case, the conjugate group has a donor group (D) and an acceptor group (A). still,
The molecular orientation is not limited to the vertical orientation shown in the figure,
It may be diagonal or a mixture thereof.

In the polymer shown in the schematic view of FIG. 16, the conjugated system is connected, but the neutral molecular unit (H) having neither donor property nor acceptor property is inserted. FIG. 17 shows the addition of D and A to the conjugated chain, n-type, p
This is an example in which a type semiconductor is used. The electrons flow along the conjugated chain. The strength of n and p can be adjusted by the addition amount of D and A. In this example, a pn junction was created. The n-type and the p-type can be made independently. These also have the functions of a photodiode and an LED. Furthermore, laser oscillation is possible by introducing a resonator structure.

FIG. 18 is an example of a TFT using the conjugated polymer according to the present invention, and a polymer having D and A is used as a constituent material of the organic thin film layer 18. 1 in the figure
Reference numeral 9 is a gate insulator. FIG. 19 is an example of an optical waveguide. Buffer layer 20 / Nonlinear optical material layer 2
The 1 / buffer layer 20 is made to appear continuously on the polymer chains. The buffer layer is a layer composed of a single bond and having a low refractive index. In this case, the buffer layer may be formed of a conjugated polymer. The difference in refractive index between the non-linear optical layer and the buffer layer can be controlled by adjusting the ratio of conjugated bond and single bond, adjusting substituents, and the like.

Further, another example of the polymer of the present invention is shown in FIG.
0 is shown in a schematic diagram. In the figure, 3 is a substrate. In addition, FIG. 21 is a diagram showing absorption curves measured for another example of the polymer according to the present invention. In the figure, TPA represents terephthalaldehyde and NPDA represents 2-nitro-
1,4-phenylenediamine, T _S is the substrate temperature. Absorption of NPDA alone due to polymerization has disappeared. It goes without saying that the above-mentioned introduction of the donor and / or the acceptor, the formation of the quantum well, and the device using them can be formed not only by the MLD method but also by CVD with controlled film thickness.

As described above, according to the present invention,
It is possible to obtain a conjugated polymer having a clean conjugated chain, and to realize a conjugated polymer in which the conjugation length is controlled and quantum wells are formed. In addition, high-performance non-linear optical materials, organic functional thin films such as organic semiconductor materials, and devices using them can be realized.

[Brief description of drawings]

FIG. 1 is an absorption spectrum diagram of an example of a film according to the present invention.

FIG. 2 is an absorption spectrum diagram of another example of the film according to the present invention.

FIG. 3 is an absorption spectrum diagram of another example of the film according to the present invention.

FIG. 4 is an absorption spectrum diagram of another example of the film according to the present invention.

FIG. 5 is a schematic view showing an example of the polymer of the present invention in which a potential well is formed.

FIG. 6 is a diagram showing a relationship between the length of a well portion and an absorption peak in the polymer molecule of the present invention.

FIG. 7 is a diagram showing absorption peaks in the polymer molecule of the present invention due to the difference in the binding group of the paria part.

FIG. 8 is a diagram schematically showing a cross-sectional structure of a film when a conjugated chain is intentionally divided by a single bond.

FIG. 9 is a diagram showing the principle of the MLD method.

FIG. 10 is a schematic diagram showing a film forming apparatus useful for carrying out the MLD method.

FIG. 11 is a diagram for explaining one of the advantages of film formation by the MLD method.

FIG. 12 is an explanatory diagram of a case where a substrate is previously treated with a silane-based surfactant having an amino proton at a terminal.

FIG. 13 is a diagram showing absorption curves measured for an example of the polymer according to the present invention.

FIG. 14 is a diagram showing a structure of a molecule in FIG. 13.

FIG. 15 is a diagram schematically showing a cross-sectional structure of another example of the membrane when the conjugated chain is intentionally divided by a single bond.

FIG. 16 is a schematic diagram of a polymer in which a neutral molecular unit having neither donor property nor acceptor property is inserted.

FIG. 17 shows a polymer according to the present invention with n-type, p-type
It is a figure which shows the example made into a type semiconductor.

FIG. 18 is a diagram showing an example of a TFT using the conjugated polymer according to the present invention.

FIG. 19 is a diagram showing an example of an optical waveguide using the conjugated polymer according to the present invention.

FIG. 20 is a schematic view of another example of the polymer of the present invention obtained by the MLD method.

FIG. 21 is a diagram showing absorption curves measured for another example of the polymer according to the present invention.

FIG. 22 is a diagram illustrating an example of MLD using TPA and PPDA.

[Explanation of symbols]

 1, 16 ... Conjugated portion (well portion) 2, 17 ... Non-conjugated portion (barrier portion) 3 ... Substrate 4 ... Layer of molecule having donor property 5 ... Layer of molecule having acceptor property 6 ... Layer of molecule serving as barrier 7 ... K cell for molecular evaporation 7 8 ... Shutter 9 ... Monomer gas cylinder or monomer gas supply cell 10 ... Valve 11 ... Substrate holder 12, 13 ... Electrode 14 ... Film thickness monitor 15 ... Thermocouple 18 ... Organic thin film layer 19 ... Gate insulator 20 ... Buffer layer 21 ... Non-linear optical material layer

Claims (26)

[Claims] 1. An organic functional thin film comprising a polymer obtained by linking a plurality of types of molecules that are bound by a double or triple bond, the polymer having a continuous π electron conjugation length of 10 Å or more. 2. The thin film according to claim 1, wherein the polymer is a polymer obtained by alternately binding molecules having a plurality of —CHO groups and molecules having a plurality of —NH ₂ groups. 3. The thin film according to claim 1, wherein the polymer is microcrystalline. 4. A polymer obtained by linking a plurality of types of molecules which are bound by a double or triple bond, wherein a part of the conjugated system between molecular units involved in the bond is separated by a single bond. Organic functional thin film made of polymer. 5. The thin film according to claim 4, wherein the single bond is formed by bonding with another molecule of a group contained in at least a part of the plurality of kinds of unit molecules. 6. The thin film according to claim 4, wherein the single bond is introduced by copolymerizing a molecule containing two or more continuous single bonds. 7. A polymer obtained by linking a plurality of types of molecules which are bound by a double or triple bond, wherein at least a part of the molecular unit is a polymer having a donor property and / or an acceptor property Functional thin film. 8. The donor property is --NH ₂ , --N (CH ₃ ) ₂ , --OCH ₃ , --OH.
The organic functional thin film according to claim 7, which is provided by a donor group such as. 9. The organic functional thin film according to claim 7, wherein the acceptor property is provided by an acceptor group such as —NO ₂ , —CN, and —CF ₃ . 10. The thin film according to claim 7, wherein at least one of the donor groups is a group other than a —NH ₂ group. 11. The thin film according to claim 7, wherein the polymer is a polymer in which a molecule having a plurality of —CHO groups and a molecule having a plurality of —NH ₂ groups are alternately bonded. 12. The thin film according to claim 7, wherein the polymer is microcrystalline. 13. The thin film according to claim 7, wherein the polymer is a polymer in which a part of a conjugated system between molecular units involved in a bond is separated by a single bond. 14. The thin film according to claim 13, wherein the single bond is formed by bonding with another molecule of a group contained in at least a part of the plurality of types of unit molecules. 15. The thin film according to claim 13, wherein the single bond is introduced by copolymerizing a molecule containing two or more continuous single bonds. 16. When preparing the organic functional thin film according to any one of claims 1 to 15, molecules are introduced into a vacuum or evaporated in a vacuum, and are bound and / or polymerized on a substrate to form a thin film. A method of making the shape of. 17. The method according to claim 16, wherein the MLD method is used to sequentially deposit molecules to be polymerized onto a substrate to form a film. 18. The substrate according to claim 1, which has been previously treated with a silane-based surfactant having an amino proton at a terminal.
The method according to 6 or 17. 19. The method according to claim 16, wherein a film formed of a molecule having an amino proton is previously formed. 20. The molecule is 1,10-diaminodecane,
The method according to claim 19. 21. A non-linear optical material using the film according to claim 1. 22. An optical waveguide using the film according to claim 1. 23. A p-type or n-type semiconductor using the film according to claim 1. 24. A pn junction using the film according to claim 1. 25. A TFT using the film according to claim 1. 26. A light emitting device using the film according to claim 1.