JP2008032853A - Liquid crystal alignment film, method for manufacturing liquid crystal alignment film, and liquid crystal element - Google Patents

Abstract

A liquid crystal alignment film having high light durability and a method for producing the liquid crystal alignment film by a simple method are provided.
A liquid crystal alignment film having a plurality of pores formed perpendicularly or substantially perpendicular to a substrate, the liquid crystal alignment film comprising silicon, germanium, or one of silicon and germanium, oxygen Containing. A method for producing a liquid crystal alignment film having a plurality of pores formed perpendicular or substantially perpendicular to a substrate, wherein a columnar substance containing aluminum forms a eutectic with the aluminum on the substrate, A step of forming a structure thin film dispersed in a member containing germanium or silicon and germanium; and a step of removing the columnar substance to form a plurality of pores.
[Selection] Figure 1

Description

  The present invention relates to a liquid crystal alignment film that is hardly deteriorated by high-intensity light used in projectors and the like, a simple method for producing a liquid crystal alignment film, and a liquid crystal element using the liquid crystal alignment film.

  A liquid crystal element used for a PC monitor, a thin television, a projector, or the like has a configuration in which a liquid crystal composition is introduced between a pair of substrates on which a pixel electrode and a counter electrode are formed. In order for the liquid crystal element to have an optical switching function, it is necessary that the liquid crystal alignment has a certain regularity during and before and after the application of an electric field to the liquid crystal. A liquid crystal alignment film is formed that regulates in a certain direction.

  As the liquid crystal alignment film, an organic alignment film typified by polyimide is widely used. However, in a liquid crystal element used for a high-luminance projector, there is a problem that the alignment film is light-degraded because the intensity of light applied to the alignment film is high. This problem is solved by adopting an inorganic alignment film instead of the organic alignment film.

The inorganic alignment film is formed by using a vapor deposition method generally called an oblique vapor deposition method. This is a method in which vapor deposition is performed in a state where a line segment connecting the substrate normal line and the substrate center-vapor deposition source is maintained at a certain angle, and this angle is generally called a vapor deposition angle. As a material, silicon oxide (SiO _x : x = 1 to 2) is generally used, and silicon oxide in a boat or a crucible is evaporated by a resistance heating method or electron beam irradiation. By using such an oblique vapor deposition method, a columnar structure (column structure) made of SiO _x grown obliquely on the substrate is formed. The surface of the thin film having the SiO _x column structure has shape anisotropy corresponding to the deposition angle and the deposition direction, and it is said that the liquid crystal is oriented in a specific direction.

  The inorganic alignment film formed by the oblique deposition method is roughly classified into a 60 degree deposition system and an 80 degree deposition system. When a general Np type liquid crystal (nematic liquid crystal with positive dielectric anisotropy) is used, in a 60 degree vapor deposition film, liquid crystal molecules are arranged in a direction perpendicular to the vapor deposition direction, and the pretilt angle shown in FIG. (An angle formed by the average direction of the liquid crystal director and the substrate normal when no voltage is applied) is 90 degrees. On the other hand, in 80 degree system vapor deposition, the liquid crystal director is oriented in the same direction as the vapor deposition direction, and a pretilt angle of about 55 degrees to 80 degrees occurs. Further, when Nn type liquid crystal (nematic liquid crystal having negative dielectric anisotropy) that is aligned perpendicularly to the surface of the alignment film is used, the pretilt angle is 0 degree in the alignment film of 60 degree vapor deposition system, and 80 In the case of a vapor deposition type alignment film, the pretilt angle is 10 to 35 degrees.

Recently, an example of forming an alignment film using surface shape anisotropy of another organic material or inorganic material instead of the obliquely deposited film has been reported. This is an attempt to obtain surface anisotropy necessary for liquid crystal alignment by a method other than oblique deposition. For example, silicon oxide produced by sputtering is irradiated with an ion beam from an oblique direction (see Non-Patent Document 1), or anodized with nanometer-order pores formed on the surface as a liquid crystal alignment film (for example, a patent) References 1, 2) have been reported. In addition, an example (Patent Document 3) in which a thin film having a plurality of holes produced by a process such as a photolithography process is used as an alignment film has been reported.
Japanese Patent No. 2764997 JP 2005-275194 A JP 2004-240117 A Japan Journal of Applied Physics, Volume 44, pp. 8071-8076 (2005)

  However, in the method using porous alumite as shown in Patent Documents 1 and 2, it is necessary to perform anodization in an acid aqueous solution after forming an aluminum film, and the process becomes complicated. Further, as shown in Patent Document 3, in order to produce a thin film having a hole with a diameter of 5 nm to 100 nm, there is a region that cannot be substantially produced by ordinary photolithography, and it is necessary to use a technique such as electron beam lithography. is there.

  The present invention has been made in view of the above problems, and provides a liquid crystal alignment film having high light durability using an inorganic material having a nanometer-order structure. Moreover, the manufacturing method of the liquid crystal aligning film, and the liquid endurance liquid crystal element using the liquid crystal aligning film are provided.

  That is, the first invention according to the present invention is a liquid crystal alignment film having a plurality of pores formed perpendicularly or substantially perpendicular to the substrate, and the liquid crystal alignment film is made of silicon, germanium, or silicon germanium. It is characterized by containing 1 type and oxygen.

  A metal columnar substance having a diameter equal to or smaller than the diameter of the pores is installed at the bottom of the plurality of pores, the length of the columnar substance in the major axis direction is L, and the film thickness of the liquid crystal alignment film is T. In this case, it is preferable that L <T.

The average diameter of the plurality of pores is preferably 1 nm or more and 30 nm or less, and the average interval between the plurality of pores is preferably 3 nm or more and 50 nm or less.
It is preferable that the material of the metal columnar substance placed at the bottom of the pore contains Al.

  According to a second aspect of the present invention, there is provided a method for producing a liquid crystal alignment film having a plurality of pores formed perpendicularly or substantially perpendicular to a substrate, the first component being contained on the substrate. Forming a structure thin film in which a columnar substance is dispersed in a member containing a second component capable of forming a eutectic with the first component; and removing the columnar substance to form a plurality of pores It has the process of forming.

In the step of removing the columnar substance to form a plurality of pores, it is preferable that the columnar substance is not completely removed and the columnar substance is left at the bottom of the pores.
It is preferable that the step of removing the columnar substance to form a plurality of pores is wet etching using a solution.

The step of removing the columnar substance to form a plurality of pores is preferably dry etching.
It is preferable to have a step of irradiating the liquid crystal alignment film with an ion beam obliquely after the step of removing the columnar substance to form a plurality of pores.

Preferably, the first component is aluminum and the second component is silicon, germanium, or any one of silicon and germanium.
According to a third aspect of the present invention, a liquid crystal layer is sandwiched between a pair of substrates disposed to face each other, a plurality of pixel electrodes are provided on one substrate of the pair of substrates, and the other 5. A liquid crystal element in which a counter electrode is provided on the substrate and a liquid crystal alignment film is provided on the pixel electrode and the counter electrode, respectively, wherein at least one of the liquid crystal alignment films is any one of claims 1 to 4. It is characterized by comprising the liquid crystal alignment film as described above.

  The liquid crystal alignment film provided on the substrate provided with the pixel electrode is a liquid crystal alignment film in which a metal columnar substance is provided at the bottom of a plurality of pores, and provided on the substrate provided with the counter electrode. The liquid crystal alignment film is a liquid crystal alignment film in which a metal columnar substance is not provided at the bottom of a plurality of pores, and the metal columnar substance is used as a pixel electrode and a reflective electrode having a function of reflecting incident light. Is preferred.

  According to the present invention, it is possible to provide a liquid crystal alignment film having high light durability and a method for producing the liquid crystal alignment film by a simpler method than the liquid crystal alignment film. In addition, a liquid crystal element having high light durability using the liquid crystal alignment film can be provided.

Hereinafter, the present invention will be described in detail.
First, the liquid crystal alignment film of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing an example of the configuration of the liquid crystal alignment film of the present invention. As shown in FIG. 1, the liquid crystal alignment film 11 is provided on a substrate 14, and the liquid crystal alignment film 11 has a plurality of pores 12 formed perpendicular or nearly perpendicular to the substrate 14. A reflective electrode 13 is provided on the bottom of the substrate. The reflective electrode 13 provided at the bottom of the pore is made of a columnar material, and L <T, where L is the length of the columnar material in the major axis direction and T is the thickness of the liquid crystal alignment film.

First, the substrate 14 will be described. The substrate 14 includes a Si substrate on which a transistor for driving a liquid crystal is formed, a TFT substrate formed on a glass substrate, tin-doped indium oxide (ITO), tin oxide (SnO ₂ ), zinc oxide (ZnO), and the like. A glass substrate or the like on which a transparent electrode is formed is used. Of the above substrates, basically any substrate may be used as long as a thin film can be formed on the upper surface of the substrate by a film forming method such as sputtering.

  Next, the liquid crystal alignment film 11 will be described. FIG. 2 is a schematic view of a structure thin film produced in the manufacturing process of the liquid crystal alignment film of the present invention. The liquid crystal alignment film includes a base material 24 in which the columnar substance 21 including the first component shown in FIG. 2A includes a second component capable of forming a eutectic with the first component. It is formed by removing the columnar substance 21 from the structure thin film 23 dispersed therein. This liquid crystal alignment film is shown in FIG. In FIG. 2B, the liquid crystal alignment film 25 is a porous thin film formed by partially or completely removing the columnar substance 21, and the columnar substance 21 is removed in the base material 24. There are formed pores 26.

  Here, the columnar substance 21 including the first component is made of, for example, a material mainly composed of aluminum. The content of aluminum contained in the columnar substance is 60% or more, preferably 80% or more. Moreover, the element contained other than aluminum is a 2nd component which can form a eutectic with the 1st component mentioned later, for example, silicon, germanium, etc. are mentioned.

  The base material 24 including the second component that can form a eutectic with the first component is made of, for example, germanium, silicon, or a mixture of germanium and silicon. The base material 24 is preferably composed mainly of silicon or germanium. It is also possible to use a mixture of silicon and germanium as a main component. The content of germanium, silicon, or a mixture of germanium and silicon contained in the base material is 40% or more, preferably 60% or more.

  The base material 24 is preferably composed mainly of silicon or germanium, but aluminum (Al), oxygen (O), argon (Ar), nitrogen (N) of several atomic% to several tens atomic%. Various elements such as hydrogen (H) may be contained.

  The base material 24 is preferably an oxide. However, if the surface of the porous thin film and the surface of the pores are oxidized, the inside of the base material may be crystalline or amorphous silicon or germanium which is not an oxide, or a mixture of silicon and germanium.

  The thickness of the liquid crystal alignment film 25 is not particularly limited as long as it is a film thickness capable of forming pores, but when used as a liquid crystal alignment film, it is preferably 1 nm or more and 1 μm or less, and more preferably 50 nm or more and 300 nm or less. .

  The diameter of the pores 26 formed in the liquid crystal alignment film 25 is not particularly limited, but is desirably 1 nm to 30 nm, preferably 3 nm to 25 nm. This is because a good liquid crystal alignment characteristic can be obtained by having such a pore size. The average interval between the pores is 3 nm to 50 nm, preferably 6 nm to 15 nm.

Next, a cross section of the liquid crystal alignment film is shown in FIG. A liquid crystal alignment film 11 is disposed on the substrate 14, and a reflective electrode 13 is formed at the bottom of the pores 12 formed in the liquid crystal alignment film 11.
When the columnar substance 21 in FIG. 2A is removed, the reflective electrode 13 is preferably formed by leaving the columnar substance 21 at the bottom of the pore without completely removing the columnar substance 21. By forming by such a method, the reflective electrode 13 can be easily formed. However, the method of forming the reflective electrode 13 in the pores 12 is not particularly limited to the above method, and may be formed by other methods. The material of the reflective electrode 13 inevitably becomes the same as the columnar substance when formed by a method in which the columnar substance remains, and is a material mainly composed of aluminum as described above. In other cases, the material is not particularly limited. However, since it is necessary to efficiently reflect light introduced into the liquid crystal element, a material having high light reflectance is preferable, and for example, aluminum, aluminum alloy, silver, and the like are preferable.

  FIG. 3 is a cross-sectional view showing an example of the configuration of the liquid crystal alignment film of the present invention. As shown in FIG. 3A, a liquid crystal alignment film may be formed on a substrate on which a reflective electrode is originally formed. In that case, as shown in FIG. 3A, the upper reflective electrode 33 may be provided, or when the lower reflective electrode 34 functions sufficiently, the upper reflective electrode 33 may not be provided. However, the presence of the upper reflective electrode 33 is preferable because it provides sufficient adhesion between the lower reflective electrode 34 and the liquid crystal alignment film 31. Moreover, the material of the upper reflective electrode 33 and the lower reflective electrode 34 is not particularly required to be the same material, and different materials may be used.

  Further, when forming a liquid crystal element, at least one of the two substrates on which the liquid crystal alignment film is formed needs to use a transparent substrate in which a transparent electrode is formed on a glass substrate. In the case of using a transparent substrate, it is not necessary to form a reflective electrode. In this case, the columnar substance 21 in FIG. 2 may be completely removed.

Next, the manufacturing method of a liquid crystal aligning film is demonstrated.
The steps of one embodiment of the method for producing a liquid crystal alignment film are shown below. The manufacturing method of a liquid crystal aligning film has the following process (a) and process (b).

Step (a): A columnar substance containing a first component is dispersed on a substrate in a member containing a second component capable of forming a eutectic with the first component. Forming a structure thin film;
Step (b): A step of removing the columnar substance and forming a liquid crystal alignment film and a reflective electrode.

Next, process (a) is demonstrated.
As shown in FIG. 2A, a columnar substance 21 including a first component on a substrate includes a second component capable of forming a eutectic with the first component. A structure thin film 23 dispersed in the material 24 is prepared. For example, a base material (second component) and a material that forms a columnar material (first component) in the base material (second component) are prepared. For example, aluminum and silicon (or germanium, or a mixture of silicon and germanium) are prepared. Next, a mixed film (aluminum silicon mixed film, aluminum germanium mixed film, or aluminum silicon germanium mixed film) that is a structure thin film on a substrate by a method capable of forming a substance in a non-equilibrium state such as sputtering or electron beam evaporation. Form.

  When an aluminum silicon mixed film (or aluminum germanium mixed film or aluminum silicon germanium mixed film) is formed by such a method, an eutectic structure in which aluminum and silicon (or germanium, or a mixture of silicon and germanium) are metastable. It becomes. Then, a nanostructure (columnar structure) in which aluminum is in the level of several nanometers to several tens of nanometers in a base material composed of amorphous silicon (or amorphous germanium, or a mixture of amorphous silicon and germanium). And self-organizing.

  Note that in a mixed film of aluminum and amorphous silicon (or amorphous germanium, or a mixture of amorphous silicon and germanium), the amount of silicon (or germanium, or a mixture of silicon and germanium) in the formed film is the same as that of aluminum. It is 20 atomic% or more and 70 atomic% or less, preferably 25 atomic% or more and 65 atomic% or less, based on the total amount of silicon (or germanium, or a mixture of silicon and germanium). If the amount of silicon (or germanium, or a mixture of silicon and germanium) is within such a range, the columnar material of aluminum is present in the matrix material of amorphous silicon (or amorphous germanium, or a mixture of silicon and germanium in an amorphous state). A dispersed aluminum silicon mixed film (or aluminum germanium mixed film or aluminum silicon germanium mixed film) is obtained. The shape of the columnar substance varies depending on the ratio of aluminum and silicon (or germanium, or a mixture of silicon and germanium) in the mixed film.

  The atomic% indicating the ratio of aluminum and silicon (or germanium, or a mixture of silicon and germanium) indicates the ratio of the number of atoms of silicon (or germanium, or a mixture of silicon and germanium) and aluminum, and atom% Alternatively, it is also described as at%. For example, silicon (or germanium, or silicon and germanium) in an aluminum silicon mixed film (or aluminum germanium mixed film or aluminum silicon germanium mixed film) by inductively coupled plasma emission spectrometry (ICP method). It is the value when the amount of aluminum is quantitatively analyzed.

Next, step (b) will be described.
The columnar substance 21 is removed, and a liquid crystal alignment film 25 is prepared. For example, aluminum, which is a columnar substance in the aluminum silicon mixed film (or aluminum germanium mixed film or aluminum silicon germanium mixed film), is etched with a solution (wet etching) or a gas (dry etching) to form a matrix (here, silicon). Alternatively, pores 56 are formed in germanium or silicon germanium). Thereby, a porous thin film as shown in FIG. 2B is formed. The pore shape of the porous thin film varies depending on the ratio of aluminum and silicon (or germanium or silicon and germanium) in the aluminum silicon mixed film (or aluminum germanium mixed film or aluminum silicon germanium mixed film). As it increases, the pore shape changes from a circular shape to an elliptical shape and an irregular shape.

  The solution used for wet etching is preferably an acid that dissolves aluminum and hardly dissolves silicon (or germanium), and does not affect the transistor, TFT, transparent electrode, or the like formed on the substrate. For example, acids such as phosphoric acid, sulfuric acid, hydrochloric acid, and chromic acid solution are preferable. However, under conditions where there is no inconvenience to the formation of pores by etching and the substrate, for example, conditions where etching is performed by contacting the solution only with the structure thin film 23 without touching the substrate, acids other than those described above or hydroxylation An alkali such as sodium or ammonia can be used. The kind of acid and the kind of alkali are not particularly limited, and several kinds of acid solutions or a mixture of several kinds of alkali solutions may be used. In addition, for example, the etching conditions, solution temperature, concentration, time, etc. can be appropriately set according to the porous thin film to be produced.

Further, the gas used in the method of removing the columnar substance 21 in the structure thin film 23 by dry etching using a gas does not cause any inconvenience to the substrate as in the case of the solution, and the base material 24 such as silicon (or germanium). It is preferable to use a gas that hardly etches. Examples of such a gas include chlorine-based gases such as Cl ₂ and BCl ₃ , and mixed gases of these chlorine-based gases.

  When the columnar substance 21 in FIG. 2A is partially removed and a reflective electrode is formed in the base material 24, the thickness of the reflective electrode can be controlled by the etching time. In this case, when wet etching is used, the film thickness can be controlled more precisely by the etchant concentration and composition, and when dry etching is used, the gas flow rate and the type of gas to be mixed.

  Alternatively, all the columnar substances 21 may be removed, and then the pores 26 may be filled with a substance that becomes a reflective electrode. Examples of the filling method include electrodeposition methods and electroless plating methods. When the electrodeposition method is used, a conductive thin film needs to be formed below the base material 24. Such a configuration is not particularly necessary in the case of electroless plating.

  In the case of a reflective liquid crystal element, one of the two substrates sandwiching the liquid crystal layer must always transmit light. In the case of a transmissive liquid crystal element, both of the two substrates need to transmit light. Such a liquid crystal alignment film formed on a substrate that needs to transmit light needs to transmit light well like the substrate. In order to realize this light transmittance, it is necessary to form a liquid crystal alignment film from which all columnar substances are removed as shown in FIG. In this case, the columnar substance can be removed by wet etching or dry etching as described above, and the removal conditions can be optimized by controlling the etching time and etching conditions.

  Further, after the step (b), a step of irradiating the liquid crystal alignment film with an ion beam (step (c)) may be added. By producing a liquid crystal element using a liquid crystal alignment film produced by adding the step (c), the pretilt angle of the liquid crystal molecules shown in FIG. 6 can be controlled more precisely than when no ion beam is irradiated. . As a result, alignment defects such as disclination lines due to the reverse-tist domain can be reduced.

This process will be described with reference to FIG. FIG. 4 is an explanatory diagram for explaining an ion beam irradiation method for the liquid crystal alignment film. FIG. 4A is a schematic diagram showing a state in which ions are irradiated onto the substrate. The irradiation substrate 42 on which the liquid crystal alignment film is formed is irradiated with ions emitted from the ion source 41. At that time, it is preferable that a line segment connecting the substrate normal 43, the ion source, and the substrate center has a certain angle (irradiation angle 44). By irradiating the substrate with an ion beam obliquely in this way, shape anisotropy is imparted to the surface of the liquid crystal alignment film, and a pretilt angle is easily imparted. The irradiation angle 44 can be set to an appropriate size in order to develop a desired pretilt angle. The ion species to be irradiated is not particularly limited as long as it does not significantly reduce the characteristics of the liquid crystal alignment film and the reflective electrode to be irradiated. Argon (Ar) ions, oxygen (O ₂ ) ions, nitrogen (N ₂ ) Ions, helium (He) ions, xenon (Xe) ions, or the like can be used. Among these, it is preferable to use ions such as argon (Ar) ions, oxygen (O ₂ ) ions, and nitrogen ions.

Next, the liquid crystal element of the present invention will be described.
The liquid crystal element of the present invention is a reflective liquid crystal element, and is composed of (a) two substrates on which a liquid crystal alignment film is formed, (b) a spacer, (c) a sealing agent, and (d) a liquid crystal composition. . Each will be described below.

(A) Two substrates on which a liquid crystal alignment film is formed The liquid crystal alignment film is formed on a substrate on which a liquid crystal driving element such as a transistor is formed or on a glass substrate on which a transparent electrode is formed. Here, as described above, one of the two substrates on which the liquid crystal alignment film is formed needs to transmit light. Therefore, one of the two substrates with alignment films uses a liquid crystal alignment film and a substrate that transmit light. Further, the other substrate with the alignment film is used on which the reflective electrode is formed. In the liquid crystal element of the present invention, a liquid crystal alignment film in which the aforementioned Al columnar substance is disposed at the bottom of the pore is used.

  After providing a spacer and a sealant, which will be described later, on one of the two substrates, they are bonded together to form an empty cell. At this time, in order to make the display quality of the liquid crystal element uniform within the element, it is necessary to bond the liquid crystal elements so that the gap between the two substrates is formed uniformly. As long as the uniformity of the gap is maintained, the substrates may be bonded by basically any method.

(B) Spacer A spacer is used to keep the gap between the two substrates uniform. There are no particular restrictions on the material and shape of the spacer as long as the object can be achieved, but in the present invention, a spacer in the form of fine particles such as silica (SiO ₂ ) fine particles is preferably used because of high gap controllability. Is done. The shape and size of the spacer are selected in accordance with the cell gap suitable for the purpose of the liquid crystal element. The spacer may be dispersed in an appropriate amount on the alignment film, or as described later, the spacer may be mixed in advance with a sealant used for fixing two substrates. When a small liquid crystal display used for a projector or the like is used, it is preferable to take the latter configuration in order to prevent the influence of light leakage or the like by the spacer to the minimum, and from the simplicity of the manufacturing method.

(C) Sealing agent Used to bond two substrates on the alignment film substrate. There are various types of sealing agents such as thermosetting type and ultraviolet curing type, and an appropriate one can be selected and used according to the purpose. In addition, as described in (b), spacers and the like may be mixed in the sealing agent in advance, and the steps of spraying the spacer and applying the seal may be performed at the same time, especially when producing a small liquid crystal display. It can be said that it is preferable from the viewpoint of process simplification. There are various methods for applying the seal, such as drawing a seal pattern on the substrate using a dispenser, and transferring the seal pattern onto the substrate by screen printing, which significantly impairs the liquid crystal alignment function of the deposited thin film. Otherwise, basically, any method may be used to apply the sealing agent.

(D) Liquid crystal composition The liquid crystal composition is held in the aforementioned empty cell. The liquid crystal composition can be introduced into the empty cell by any method as long as the liquid crystal is uniformly introduced into the cell. However, when the liquid crystal is introduced using a liquid crystal injection apparatus or the like. This is a preferable method because the liquid crystal can be uniformly introduced into the cell. The liquid crystal is introduced into the cell and then sealed to prevent the liquid crystal composition from flowing out of the cell. Thereafter, the cell temperature is raised above the isotropic phase temperature of the liquid crystal composition and then cooled down to align the liquid crystal composition in the cell in one direction.

  As the liquid crystal to be injected, various types of liquid crystal compositions can be used depending on the liquid crystal mode, for example, TN mode, VA mode, OCB mode, IPS mode, and the like. When the liquid crystal alignment film of the present invention is used, it is preferable to use a liquid crystal composition having negative dielectric anisotropy (Δε <0) for VA mode.

Hereinafter, the present embodiment will be described in more detail using examples, but the present invention is not limited to those described in the examples.
Example 1
In this example, the liquid crystal alignment film shown in FIG. 1 is manufactured, and a liquid crystal element is manufactured using the liquid crystal alignment film.

  First, an Si substrate (hereinafter referred to as an Si-MOS substrate) on which a large number of reflective liquid crystal element driving panels are formed, on which MOS transistors are formed, is prepared. The size of the Si-MOS substrate is 20 cm (8 inches) in diameter. On this Si-MOS substrate, an aluminum silicon structure thin film containing 65 atomic% of aluminum with respect to the total amount of aluminum and silicon is formed to a thickness of about 130 nm by RF magnetron sputtering. A circular aluminum silicon mixed target having a diameter of 4 inches (101.6 mm) is used as the target. The aluminum silicon mixed target is obtained by sintering aluminum powder and silicon powder at a ratio of 65 atomic%: 35 atomic%. Sputtering conditions were as follows: using an RF power source, Ar flow rate: 30 sccm, discharge pressure: 0.15 Pa, input power: 100 W, and substrate temperature: 100 ° C.

  In addition, when the said aluminum silicon structure thin film is observed with FE-SEM (field emission scanning electron microscope), the shape of the surface seen from the substrate diagonally upward direction is a base material as shown in FIG. It can be observed that circular aluminum columnar substances surrounded by a certain silicon are arranged two-dimensionally. At this time, the average diameter of the aluminum columnar substance is 12 nm. Moreover, when a cross section is observed by FE-SEM, it is observed that each aluminum columnar substance is independent of each other.

  A 5 wt% phosphoric acid solution is dropped onto the surface of the aluminum silicon structure thin film thus produced. The amount of dripping is such that the solution spreads over the entire surface of the substrate, and by maintaining this state for 60 minutes, only the aluminum columnar substance portion is selectively etched to form a liquid crystal alignment film having pores and reflective electrodes. Thereafter, the substrate surface is sufficiently washed with pure water and then dried.

  It can be confirmed by visual observation that the substrate surface on which the liquid crystal alignment film is formed is a mirror surface and reflects light well. Further, according to the visible light reflectance measurement, the reflectance of the liquid crystal alignment film having the aluminum columnar substance at the bottom of the pore is about 70%.

  Next, the aluminum silicon structure thin film etched with 5 wt% phosphoric acid is observed with an FE-SEM (field emission scanning electron microscope). As shown in FIG. 1B, the cross section of the substrate is such that the pores surrounded by the silicon oxide member are two-dimensionally arranged, and the aluminum columnar substance serving as the reflective electrode is not etched at the bottom of the pore. Can be confirmed. The thickness of the remaining aluminum is about 50 nm from the cross-sectional SEM image, the pore diameter of the pores and the remaining aluminum columnar substance is about 12 nm, and the average interval between the pores is about 16 nm. Further, in the prepared liquid crystal alignment film, the silicon oxide portion is in an amorphous state from the diffraction peak shape by X-ray diffraction, and only the peak due to the remaining aluminum columnar substance is observed. I understand that there is.

Next, an etching mask is formed on a portion where an electrode is to be formed on the liquid crystal alignment film manufactured by the above method, and then aluminum in a portion where the etching mask is not formed is removed by dry etching. Boron trichloride (BCl ₃ ) is used as an etching gas, and aluminum can be removed by performing etching for an appropriate time under conditions of, for example, 1 Pa, 400 W, and 50 sccm. Thereafter, the etching mask is removed with an oxygen plasma asher.

  When the cross-sectional structure of the aluminum silicon structure thin film after dry etching is observed using FE-SEM, only the portion where the etching mask is formed, the aluminum columnar substance that becomes the reflective electrode remains, and the portion where the etching mask is not formed It can be confirmed that no aluminum is present at the bottom of the pores. Further, when the surface structure is observed, it can be confirmed that the reflective electrode pattern is formed.

  Next, an aluminum silicon structure thin film is formed on the glass substrate with ITO by the same method as described above. This time, the film is formed so that the thickness of the aluminum silicon structure thin film is about 80 nm. Thereafter, 5 wt% phosphoric acid is dropped on the surface of the aluminum silicon structure thin film, and the aluminum columnar substance is etched for about 2 hours to form a liquid crystal alignment film on the glass substrate surface with ITO.

  When the fine structure of the liquid crystal alignment film is observed with an FE-SEM, it can be seen that pores having a pore diameter of about 12 nm are formed on the surface of the alignment film as in the case of the Si-MOS substrate. The average interval between the pores was 16 nm. Further, when the cross section of the alignment film is observed, it can be confirmed that the aluminum columnar substance does not remain and the pores are formed up to the interface between the liquid crystal alignment film and ITO. That is, the reflective electrode is not formed on the glass substrate with ITO, but only the liquid crystal alignment film is formed. The thickness of the liquid crystal alignment film is 130 nm.

  Next, the liquid crystal alignment film formed on these substrates is irradiated with an Ar ion beam. For both the Si-MOS substrate and the glass substrate with ITO, the Ar ion beam has an irradiation angle shown in FIG. 4A set to about 45 degrees and a substrate rotation angle shown in FIG. 4B set to about 45 degrees.

  Next, both the Si-MOS substrate and the glass substrate with ITO are cut into a size of about 20 mm × 16 mm with a scriber. Thereafter, a sealing agent containing a silica spacer having a particle size of 3 μm is applied onto the Si-MOS substrate, and as shown in FIG. 5, irradiation of the ion beam applied to the liquid crystal alignment film formed on the Si-MOS substrate is performed. Direction and the substrate so that the irradiation direction of the ion beam irradiated to the liquid crystal alignment film formed on the glass substrate is antiparallel (anti-parallel), and then the sealant is thermally cured at about 120 ° C., An empty cell (a cell in which no liquid crystal is injected) is produced.

  Next, MLC-6608 (manufactured by Merck), which is a liquid crystal mixture for VA (Vertical Alignment) mode, is injected into the above empty cell, then sealed, and heated to a temperature higher than the nematic-isotropic phase transition temperature. A liquid crystal cell can be produced by performing an alignment treatment after cooling.

  Here, in order to measure the pretilt angle, a transmissive liquid crystal cell is manufactured by using both of the two substrates with alignment films to be bonded together as glass substrates. When the pretilt angle is measured by the crystal rotation method, a pretilt angle of about 2 degrees can be obtained. The definition of the pretilt angle at this time is an angle formed between the normal line of the substrate and the director of the liquid crystal as shown in FIG.

  When a liquid crystal element is manufactured using a liquid crystal cell having such a pretilt angle, a three-plate reflective projector is manufactured using three of them, and an image is projected onto a screen, a good display can be obtained. .

Example 2
In this example, instead of forming the aluminum silicon structure thin film in Example 1, an aluminum silicon germanium structure thin film was formed.

  In the same manner as in Example 1, aluminum silicon germanium structure thin films are formed on a Si-MOS substrate and a glass substrate with ITO, respectively, at 130 nm and 80 nm. As the aluminum silicon germanium mixed target, an aluminum powder, a silicon powder, and a germanium powder are sintered at a ratio of 70 atomic%: 20 atomic%: 10 atomic%. Sputtering conditions are as follows: using an RF power source, Ar flow rate: 20 sccm, discharge pressure: 0.075 Pa, input power: 80 W, and substrate temperature: 100 ° C.

  When the aluminum silicon germanium structure thin film is observed with an FE-SEM (field emission scanning electron microscope), it can be confirmed that the same structure as the aluminum silicon structure thin film is formed. At this time, the average diameter of the aluminum columnar substance is 18 nm, and the average interval is 25 nm. Further, as in the case of Example 1, each aluminum columnar substance is independent of each other.

  The thus prepared aluminum silicon germanium structure thin film is subjected to wet etching and dry etching under the same conditions as in Example 1 to form a liquid crystal alignment film having an aluminum reflecting electrode at the bottom of the pores on the Si-MOS substrate. Then, a liquid crystal alignment film from which the aluminum columnar substance has been completely removed is formed on the glass substrate with ITO.

  The surface of the liquid crystal alignment film produced on the Si-MOS substrate is visually mirror-like as in Example 1 and can be confirmed to reflect light well. Further, according to the visible light reflectance measurement, the reflectance of the liquid crystal alignment film containing the residual aluminum columnar substance is about 65%.

  Further, FE-SEM observation of the liquid crystal alignment film is performed, and it can be confirmed that both the liquid crystal alignment film on the Si-MOS substrate and the glass substrate with ITO have an average pore diameter of 18 nm and an average interval between the pores of 25 nm.

  After this, when Ar ions are irradiated, a liquid crystal element is produced, and a projection display device is produced in the same manner as in Example 1, and an image is projected onto the screen, a good display can be obtained as in Example 1.

  The present invention can be used for a liquid crystal element using a liquid crystal alignment film, and can also be used for a display device using the liquid crystal element, for example, a projection display device such as a projector, a liquid crystal monitor, and a liquid crystal television.

It is the schematic which shows an example of a structure of the liquid crystal aligning film of this invention. It is the schematic of the structure thin film produced in the manufacture process of the liquid crystal aligning film of this invention. It is sectional drawing which shows an example of a structure of the liquid crystal aligning film of this invention. It is explanatory drawing explaining the ion beam irradiation method to a liquid crystal aligning film. It is explanatory drawing explaining the bonding method of the board | substrate in which the liquid crystal aligning film was formed. It is explanatory drawing explaining the pretilt angle (theta) _p .

Explanation of symbols

11, 25, 31, 36, 55, 63 Liquid crystal alignment film 12, 32, 37 Pore 13 Reflective electrode 14, 22, 35, 39, 48 Substrate 21 Columnar material 23 Structure thin film 24 Base material 33 Upper reflective electrode 34 Lower reflective electrode 38, 54 Transparent electrode 41 Ion source 42 Irradiated substrate 43 Substrate normal 44 Irradiation angle 45 Substrate rotation angle 46 Ion beam irradiation direction 47 Long side direction of panel 51 Si substrate 52 Liquid crystal alignment film with reflective electrode 53, 64 Glass Substrate 56 Irradiation direction of ion beam irradiated to alignment film on Si substrate 57 Irradiation direction of ion beam irradiated to alignment film on glass substrate 61 Pretilt angle θ _p
62 Liquid crystal molecules

Claims (12)

  A liquid crystal alignment film having a plurality of pores formed perpendicularly or substantially perpendicular to a substrate, wherein the liquid crystal alignment film contains any one of silicon, germanium, or silicon germanium and oxygen. A liquid crystal alignment film.   A metal columnar substance having a diameter equal to or smaller than the diameter of the pores is installed at the bottom of the plurality of pores, the length of the columnar substance in the major axis direction is L, and the film thickness of the liquid crystal alignment film is T. The liquid crystal alignment film according to claim 1, wherein L <T is established.   3. The liquid crystal alignment film according to claim 1, wherein an average diameter of the plurality of pores is 1 nm or more and 30 nm or less, and an average interval between the plurality of pores is 3 nm or more and 50 nm or less.   4. The liquid crystal alignment film according to claim 2, wherein the material of the metal columnar substance placed at the bottom of the pore contains Al.   A method for producing a liquid crystal alignment film having a plurality of pores formed perpendicularly or substantially perpendicular to a substrate, wherein a columnar substance containing a first component is a eutectic with the first component. A liquid crystal comprising: a step of forming a structural thin film dispersed in a member containing a second component capable of forming a liquid crystal; and a step of removing the columnar substance to form a plurality of pores. A method for producing an alignment film.   6. The liquid crystal alignment film according to claim 5, wherein in the step of removing the columnar substance to form a plurality of pores, the columnar substance is not completely removed and the columnar substance is left at the bottom of the pores. Manufacturing method.   The method for producing a liquid crystal alignment film according to claim 5 or 6, wherein the step of forming the plurality of pores by removing the columnar substance is wet etching using a solution.   The method for producing a liquid crystal alignment film according to claim 5 or 6, wherein the step of removing the columnar substance to form a plurality of pores is dry etching.   9. The method according to claim 5, further comprising a step of irradiating the liquid crystal alignment film with an ion beam obliquely after the step of removing the columnar substance to form a plurality of pores. 10. A method for producing a liquid crystal alignment film.   10. The liquid crystal alignment film according to claim 5, wherein the first component is aluminum, and the second component is silicon, germanium, or any one of silicon and germanium. Manufacturing method.   A liquid crystal layer is sandwiched between a pair of substrates disposed to face each other, a plurality of pixel electrodes are provided on one substrate of the pair of substrates, and a counter electrode is provided on the other substrate. A liquid crystal element in which a liquid crystal alignment film is provided on each of an electrode and a counter electrode, wherein at least one of the liquid crystal alignment films is composed of the liquid crystal alignment film according to claim 1. A liquid crystal element.   The liquid crystal alignment film provided on the substrate provided with the pixel electrode is a liquid crystal alignment film in which a metal columnar substance is provided at the bottom of a plurality of pores, and provided on the substrate provided with the counter electrode. The liquid crystal alignment film is a liquid crystal alignment film in which a metal columnar substance is not provided at the bottom of a plurality of pores, and the metal columnar substance is used as a pixel electrode and a reflective electrode having a function of reflecting incident light. The liquid crystal element according to claim 11.

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