JPH11144526A - Fluorescent liquid crystalline charge transport material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charge transport material having charge transportability of high quality and excellent in thin layer forming property and various durabioities by providing a structure represented by a specified formula which include a skeleton structure having liquid crystallinity and showing fluorescent property and a core of liquid crystal. SOLUTION: When a display element such as electroluminescence is formed by use of a charge transport material, one represented by the formula (wherein each of R1 and R2 represents a saturated or unsaturated hydrocarbon group having a 1-2C straight chain, branched chain or cyclic structure, and R1 may be directly bonded to Z without through X1 ; each of X1 and X2 represents oxygen atom, sulfur atom, or -CO-, -OCO-, -COO-, -N=CH-, -CONH-, -NH-, -NHCO- or -CH2 - group) is used. In this case, the charge transport material has a skeleton structure (A) having liquid crystallinity in which Y shows fluorescent property and Z is the core of liquid crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystalline charge transporting material having a fluorescent property, and more particularly, to an organic material having both a liquid crystallinity and a fluorescent and a charge transporting property, and various elements or devices using the organic material. About.

[0002]

2. Description of the Related Art Conventionally, as a charge transporting material, a material in which a charge transporting molecule serving as a site for transporting a charge is dissolved or dispersed in a matrix material such as a polycarbonate resin, or a polymer main chain such as polyvinyl carbazole is used. There is known a material in which a charge transporting molecular structure is pendant. These materials are widely used as materials for photoconductors such as copiers and printers.

[0003]

In the above-mentioned conventional charge transport material, in the case of a dispersion type charge transport material, the charge transport molecule has high solubility in a polymer as a matrix to improve the charge transport performance. However, in practice, when the concentration of the charge transport molecules in the matrix is increased, the charge transport molecules crystallize in the matrix, and the concentration of the charge transport molecules varies depending on the type. % Concentration is the limit. As a result, 50% by weight or more of the entire matrix is occupied by the matrix having no charge transporting property, and there is a problem in that a sufficient charge transporting property and a sufficient response speed when the film is formed are limited by the matrix.

On the other hand, in the case of the pendant type charge transporting polymer, the proportion of the pendant having the charge transporting property is high, but the mechanical strength, environmental stability, durability and film forming property of the formed film are high. There are many practical problems in this respect. or,
This kind of charge transporting material is such that, because the charge transporting pendant is locally close to each other, such a locally adjacent portion becomes a stable site when hopping the charge, and acts as a kind of trap. There is a problem of lowering the mobility.

[0005] In any of the above materials, the characteristic of the above-mentioned amorphous material in terms of electric characteristics is that, unlike a crystalline material, a hopping site has fluctuations not only in space but also in energy. The problem exists. Therefore, the mobility largely depends on the concentration of the charge transport site, and the mobility is generally 10 ⁻⁶ to 10 ⁻⁵ cm ² / vs.
On the order of 0.1 to ¹ cm ² / vs for molecular crystals. Further, there is a problem that the charge transport characteristics have strong temperature dependence and electric field intensity dependence. This point is significantly different from a crystalline charge transport material.
In applications where a large-area charge-transporting layer is required, a polycrystalline charge-transporting material is expected in that a charge-transporting film can be formed uniformly over a large area. The material is essentially a non-uniform material microscopically, and has problems such as a need to suppress defects formed at the particle interface.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and simultaneously have the advantage of an amorphous material having structural flexibility and uniformity over a large area, and the advantage of a crystalline material having molecular orientation. Another object of the present invention is to provide a novel charge transporting material having high quality charge transporting property, thin layer forming property and various durability. Furthermore, the present inventor has also found that some of the novel charge transport materials themselves have fluorescence. For this reason, when a display element such as electroluminescence is formed using the charge transporting material, it is not necessary to introduce a fluorescent material that hinders the alignment of liquid crystal molecules. The present invention also provides a charge transport material that does not occur and can achieve high mobility.
Furthermore, since the liquid crystalline material of the present invention has both charge transporting properties and fluorescent properties, for example, when used as an electroluminescent element, a normal electroluminescent element is made of a material having electron transporting properties, hole transporting properties, and fluorescent properties. It is necessary to use a liquid crystal material to form an electroluminescent device by using only two or three layers composed of an electron transport layer, a hole transport layer, and a light emitting layer. Is possible.

[0007]

The above object is achieved by the present invention described below. That is, the present invention has a liquid crystal property,
The charge transport material is characterized in that Y has a skeletal structure exhibiting fluorescence, and Z has a structure (A) such that it is a liquid crystal core. (However, R ₁ in the above formula is a straight chain of 1 to 22 carbon atoms, a saturated or unsaturated hydrocarbon group having a branched chain or cyclic structure, R ₁ is directly Z without using the X ₁ They may be combined.
X ₁ and X ₂ represent an oxygen atom, a sulfur atom, a —CO— group, —O
CO- group, -COO- group, -N = CH- group, -CONH
— Group, —NH— group, —NHCO— group or —CH ₂ — group. )

[0008] Since liquid crystal molecules have self-orientation due to their molecular structure, the charge transport using this as a hopping site differs from the above-mentioned molecular dispersion material in that the spatial and energy dispersion of the hopping site is different. Suppressed and realizes band-like transport characteristics seen in molecular liquid crystals. For this reason, an extremely large mobility can be realized as compared with the conventional molecular dispersion material, and furthermore, there is a feature that its electric field dependence is not observed. Further, by introducing a skeleton structure exhibiting fluorescence into the liquid crystal molecules having self-orientation, a liquid crystal charge transporting material in which self-orientation is not hindered by addition of a fluorescent material.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments of the invention. The liquid crystal charge transporting materials of the present invention are listed below. Among the charge transporting materials exemplified below, preferred materials satisfy the above-mentioned criteria and are (6π-electron aromatic ring) _l , (10π-electron aromatic ring) _m or (14π-electron aromatic ring) _n (l + m + n = 1 to
4, l, m, and n each represent an integer of 0 to 4), and the 6π-electron aromatic ring in the charge transporting material having liquid crystallinity has a carbon-carbon double bond or carbon-carbon. Charge transport materials linked by a linking group having a triple bond may be mentioned. The number of aromatic rings connected is limited from the viewpoint of mobility. 6
As the π-electron aromatic ring, for example, a benzene ring, a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a tropolone ring, and as the 10π-electron aromatic ring, for example, a naphthalene ring, an azulene ring, a benzofuran ring, an indole ring, Examples of the indazole ring, benzothiazole ring, benzoxazole ring, benzimidazole ring, quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, and 14π electron aromatic ring include a phenanthrene ring and an anthracene ring. These π-electron-based aromatic rings are also known to exhibit fluorescence upon application of voltage, light irradiation, and the like, and the charge transporting material preferably used in the present invention includes these π-electron-based aromatic rings. Are linked, which is more preferable in terms of exhibiting fluorescence.

[0010]

[Table 1]

[0011]

[Table 2]

[0012]

[Table 3]

[0013]

[Table 4]

[0014]

[Table 5]

[0015]

[Table 6]

[0016]

[Table 7]

[0017]

[Table 8]

[0018]

[Table 9]

[0019]

[Table 10]

[0020]

[Table 11]

[0021]

[Table 12]

[0022]

[Table 13]

[0023]

[Table 14]

[0024]

[Table 15]

[0025]

[Table 16]

[0026]

[Table 17]

[0027]

[Table 18]

[0028]

[Table 19]

[0029]

[Table 20]

[0030]

[Table 21]

[0031]

[Table 22]

[0032]

[Table 23]

[0033]

[Table 24]

[0034]

[Table 25]

[0035]

[Table 26]

[0036]

[Table 27]

[0037]

[Table 28]

[0038]

[Table 29]

[0039]

[Table 30]

[0040]

[Table 31]

[0041]

[Table 32]

[0042]

[Table 33]

[0043]

[Table 34]

[0044]

[Table 35]

[0045]

[Table 36]

[0046]

[Table 37]

[0047]

[Table 38]

[0048]

[Table 39]

[0049]

[Table 40]

[0050]

[Table 41]

[0051]

[Table 42]

[0052]

[Table 43]

[0053]

[Table 44]

[0054]

[Table 45]

[0055]

[Table 46]

[0056]

[Table 47]

[0057]

[Table 48]

[0058]

[Table 49]

[0059]

[Table 50]

[0060]

[Table 51]

[0061]

[Table 52]

The liquid crystalline charge transporting material of the present invention as described above is useful for various uses such as an optical sensor, an electroluminescence element, a photoconductor, a spatial modulation element, and a thin film transistor. Since the liquid crystal charge transporting material of the present invention suppresses the formation of high-speed mobility and structural traps,
A first application is a high-speed response optical sensor. Next, since it has excellent charge transport performance and exhibits fluorescence itself, it can be used as a charge transport layer of an electroluminescent device that can be prepared while maintaining high mobility, and has an electric field orientation property and a photoconductive property. Can be simultaneously switched, so that it can be used for an image display device.

FIGS. 1 to 4 are diagrams illustrating the application of the charge transport material of the present invention to an electroluminescence device as a typical example. The simplest structure of the device is, as shown in FIG. 1, a light emitting layer and a charge transporting layer as a single layer sandwiched between a cathode and an anode. Only in the case of having both luminescence and fluorescence, it is possible to manufacture an electroluminescence element with this layer configuration. At this time, in order to obtain strong light emission, it is preferable that the cathode material that plays the role of electron injection has a small work function, and that the anode material has the same or larger work function value as the cathode. .

As the anode material, generally, for example, IT
O, indium oxide, tin oxide (doped with antimony, arsenic, or fluorine), Cd ₂ SnO ₄ , zinc oxide, copper iodide, or sodium, potassium, magnesium, lithium based on an alkali metal or alkaline earth metal; Sodium-potassium alloy, magnesium-indium alloy,
Magnesium-silver alloys, aluminum, gold, silver, gallium, indium, copper, etc., and the same materials as those used for the anode can also be used.

The materials used for the light emitting layer and the charge transport layer consist of a charge transport material and a light emitting material. The charge transporting material is preferably an electron and hole transporting material or a mixture of both transporting materials, or a mixture of an electron transporting material and a hole transporting material. May be used alone. In the present invention, since the charge transport material of the present invention itself has fluorescence, a light emitting material is not particularly required, but may be used in combination. When the layer structure is as shown in FIGS. 3 and 4, the thickness of the light-emitting layer (light-emitting material) is set to such an extent that the movement of electrons or holes is not hindered. The thickness of the light emitting layer is preferably 0.2 to 15 μm, and the thickness can be adjusted by dispersing spacer particles in the material or by using a sealant provided around the cell.

FIGS. 5 to 7 are diagrams for explaining application to an optical sensor as a representative example. As the configuration conditions of the optical sensor,
It is composed of the electrodes 13, 13 'and the liquid crystalline charge transporting material 14 of the present invention. As a property that can be used as an optical sensor, a change in current value due to light irradiation can be used.

FIG. 8 is a diagram illustrating application to an image display device as a representative example. In an image display device, a transparent substrate such as glass, a transparent electrode such as ITO (indium titanium oxide), a charge generation layer that generates carriers in response to exposure, a liquid crystal charge transport material of the present invention, a counter electrode (such as a gold electrode) ) Are sequentially image-exposed (input image) from the bottom of the schematic diagram to the element, the liquid crystal charge transporting material is oriented according to the exposure, and carriers flow to the counter electrode (gold electrode). By optically reading the orientation of the liquid crystal, an input image can be reproduced. If the smecticity of the liquid crystal is large, the orientation of the liquid crystal is stored for a long time, and the input information is stored for a long time.

FIG. 9 is a view for explaining an example in which the liquid crystal charge transporting material of the present invention is applied to a charge transporting layer of an image recording apparatus. As shown in FIG. 9, pattern exposure is performed from the upper part of the drawing while applying a voltage to the upper and lower electrodes 13 and 13 '. 1
At 4 ', carriers are generated in a pattern, and the charges transported by the charge transport layer 14 are discharged in the space 19 and reach the surface of the information recording layer 11.

The information recording layer is, for example, a liquid crystal polymer composite layer composed of a composite of a smectic liquid crystal and a polymer.
The liquid crystal is oriented in a pattern by the electric field due to the accumulated electric charges, is accumulated, and can be optically read.
In FIG. 10, voltage application exposure is performed in the same manner as in FIG.
The generated charges (images) are accumulated on the upper surface of the dielectric layer 20 and can be optically read. Further, the liquid crystalline charge transporting material of the present invention can be used for a spatial light modulator as schematically illustrated in FIG. Further, the liquid crystalline charge transporting material of the present invention can be used as an active layer of a thin film transistor. For example, as shown in FIG. 12, the liquid crystal material can be used by arranging it on a substrate on which source, drain, and gate electrodes are arranged.

[0070]

EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples. Example 1 4-Heptyloxybiphenylcarbon
ic acid (manufactured by Teikoku Chemical Industry Co., Ltd.) and 7-Hy
dropy-4-methyl-Cumarin (Literature: J. Chem. Soc. Chem. Commun.
(2) synthesized according to 225-6, 1995)
Dissolved in pyridylphenol, 1,3-Dicyclo
Dehydration condensation was performed at 90 ° C. using hexylcarbodiimide, and 7-hydroxy-6- (4-He
ptyroxybiphenylcarboxy) -4
-Methylcumarin was synthesized.

Example 2 An ITO electrode (surface resistance: 100 to 200) was formed by vacuum film formation.
A glass substrate provided with Ω / □ was provided with a gap by spacer particles so that the ITO electrode was opposed to the glass substrate, and a cell was prepared. The 7-Hydroxy-6- (4-Heptoxyb) obtained in Example 1 was added to the cell.
iphenylcarboxy) -4-methylc
Umarin was injected at 110 ° C. When a DC electric field of 250 V was applied to the cell, light emission derived from the compound was observed.

Example 3 An ITO electrode (with a surface resistance of 100 to 200) was formed by vacuum film formation.
Ω / □) and an Ag electrode (resistivity 1)
A cell was prepared by laminating a glass substrate provided with Ω / cm or less and a film thickness of 3000 °) with spacer particles so that the electrodes faced each other. The same liquid crystal material as the compound obtained in Example 1 was placed in the cell at 110 ° C.
Under the conditions described above. 250 in the above cell in the dark
When a DC electric field of V was applied, light emission derived from the liquid crystal material was observed.

Example 4 Using the same liquid crystal material as the compound obtained in Example 1, a cell having the layer configuration shown in FIG. 2 was prepared. In this cell, a liquid crystal material was injected into the cell at 110 ° C. When a DC electric field of 250 V was applied to the cell in a dark place, light emission derived from the liquid crystal material was observed.

Example 5 Using the same liquid crystal material as the compound obtained in Example 1, a cell having the layer configuration shown in FIG. 3 was prepared. In this cell, a liquid crystal material was injected into the cell at 110 ° C. When a DC electric field of 250 V was applied to the cell in a dark place, light emission derived from the liquid crystal material was observed.

Example 6 A cell having the layer structure shown in FIG. 4 was prepared using the same liquid crystal material as the compound obtained in Example 1. In this cell, a liquid crystal material was injected into the cell at 110 ° C. When a DC electric field of 250 V was applied to the cell in a dark place, light emission derived from the liquid crystal material was observed.

[0076]

According to the present invention as described above, a novel liquid crystal compound having a liquid crystallinity, a charge transporting property and a fluorescent property is provided. The novel liquid crystalline compound is useful as a material for an optical sensor utilizing charge transport properties, an electroluminescent element, a photoconductor, a spatial modulation element, a thin film transistor, and other sensors in addition to the use as a conventional liquid crystal. . In particular, the liquid crystalline compound of the present invention,
When used as a material for an electroluminescent element, light emission can be obtained while preventing a decrease in charge transportability and a change in liquid crystallinity due to introduction of a skeleton structure exhibiting fluorescence.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an electroluminescence element.

FIG. 2 is a schematic view of an electroluminescence element (an example of an electrode pattern).

FIG. 3 is a schematic view of an electroluminescence element.

FIG. 4 is a schematic view of an electroluminescence element.

FIG. 5 is a schematic diagram of an optical sensor.

FIG. 6 is a schematic diagram of an optical sensor.

FIG. 7 is a schematic diagram of an optical sensor.

FIG. 8 is a schematic diagram of an image display element.

FIG. 9 is a schematic diagram of an image recording apparatus.

FIG. 10 is a schematic diagram of an image recording apparatus.

FIG. 11 is a schematic diagram of a spatial modulation element.

FIG. 12 is a schematic view of a thin film transistor.

[Explanation of symbols]

 11: Information recording layer 13: Transparent electrode 13 ': Electrode (counter electrode) 14: Liquid crystalline charge transport material 14': Charge generation layer 15: Transparent substrate 15 ': Substrate 19: Space 20: Dielectric layer

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI C09K 19/06 C09K 19/06

Claims (11)

[Claims] 1. A charge-transporting material having a liquid crystallinity, a structure of (A) in which Y is a skeleton structure exhibiting fluorescence and Z is a liquid crystal core. (However, R ₁ in the above formula is a straight chain of 1 to 22 carbon atoms, a saturated or unsaturated hydrocarbon group having a branched chain or cyclic structure, R ₁ is directly Z without using the X ₁ They may be combined.
X ₁ and X ₂ represent an oxygen atom, a sulfur atom, a —CO— group, —O
CO- group, -COO- group, -N = CH- group, -CONH
— Group, —NH— group, —NHCO— group or —CH ₂ — group. ) 2. Z is Z ₁Or Z ₁-Z _Two-Z _ThreeComposed of
And Z ₁And Z _ThreeIs (6π electron aromatic ring)₁, (1
0π electron aromatic ring)_mOr (14π electron aromatic ring)_n(1
+ M + n = 1 to 4, l, m and n are each an integer of 0 to 4
And Z) _TwoIs a -CH = CH- group, -C≡C-
Group, -N = N- group, -CH = N- group, -COO- group or
The liquid crystalline charge transport material according to claim 1, which is a direct bond. 3. Y is a metal chelate compound, polycyclic fused or conjugated aromatic hydrocarbon, diphenylethylene derivative, triphenylamine derivative, diaminocarbazole derivative, bisstyryl derivative, benzothiazole derivative, benzoxazole derivative, aromatic diamine derivative. The liquid crystalline charge transporting material according to claim 1, which is selected from the group consisting of quinacridone-based compounds, perylene-based compounds, oxadiazole derivatives, coumarin-based compounds, and anthracene derivatives. 4. An electroluminescent device comprising at least one of the materials according to claim 1, 2 or 3 in a driving path. 5. An electroluminescent element, wherein the charge transporting portion and the light emitting portion are made of at least one of the materials according to claim 1, 2 or 3. 6. An electroluminescent device having at least one of the materials according to claim 1, 2 or 3 in a driving path, and wherein the charge transport section and the light emitting section have a single-layer structure. 7. An optical sensor comprising at least one of the materials according to claim 1, 2 or 3 in a drive path. 8. A photoconductor comprising at least one of the materials according to claim 1, 2 or 3 in a drive path. 9. An image display element comprising at least one of the materials according to claim 1, 2 or 3 in a drive path. 10. A spatial light modulator comprising at least one of the materials according to claim 1, 2 or 3 in a drive path. 11. A thin-film transistor comprising at least one of the materials according to claim 1, 2 or 3 in a driving path.