JPH05224211A - Optical modulating element and active matrix substrate for the same - Google Patents

Abstract

PURPOSE:To improve the display grade of a display device by applying the above element to this device. CONSTITUTION:The optical modulating element having a liquid crystal layer 11, plural substrates 14 for clamping this layer and a voltage impressing means which is formed on the substrate and impresses a voltage to this liquid crystal layer is directly provided with oriented films 10 consisting of diagonally vapor deposited films having a so-called 'interstice structure' on the electrode 13 surfaces constituting the voltage impressing means and is so constituted that the charge transfer between the liquid crystal layer and the electrode surface is executed through the interstices. The diagonal vapor deposition is executed in the state that the shades of the projections by the thin-film transistors constituting the voltage impressing means are confined or substantially confined within the row electrodes or column electrodes likewise constituting the voltage impressing means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical modulator for displaying gradation and an active matrix substrate for the optical modulator, and more particularly to a liquid crystal having at least two stable states, such as a ferroelectric liquid crystal. The present invention relates to an optical modulation element suitable as a liquid crystal element for tonal display and an active matrix substrate for an optical modulation element having an oblique vapor deposition film as an alignment film.

[0002]

2. Description of the Related Art A conventional liquid crystal display device is generally a monochrome (binary) display in which an optical modulator is driven by a simple matrix. On the other hand, an active matrix driving method for the purpose of gradation display is disclosed in JP-A-2-1892.

In this active matrix driving method, a reset signal and a write signal are applied to one pixel with their phases shifted by one switching element, and a charge amount Q injected into a pixel electrode by this write signal is applied. Amount of charge cancellation ΔS · P _S (Δ due to reversal of spontaneous polarization P _S possessed by a ferroelectric liquid crystal (hereinafter referred to as FLC)
S is intended to realize domain gradation (area gradation) by balancing with the inversion area).

[0004]

Although the above driving method is a very effective means for gradation display using a bistable ferroelectric liquid crystal, it may have some drawbacks at the same time.

One of them is a hysteresis phenomenon in the voltage-transmittance characteristic. The phenomenon will be described below.

FIG. 14 is a block diagram of a commonly used ferroelectric liquid crystal element. In FIG. 14, 14 and 14 'are substrates, 13 and 13' are transparent conductive layers, 12 and 12 'are insulating layers, 10 and 10' are alignment layers, and 11 is a ferroelectric liquid crystal layer.

FIG. 15 is an equivalent circuit when gradation display is performed by active matrix charge control drive using the ferroelectric liquid crystal element of FIG. In FIG. 15, T ₁₁ ,
_{T 12, T 21, T 22} , ‥‥ uses a switching element of an active matrix driving thin film transistor (TFT)
Is shown. LC ₁₁ , LC ₁₂ , LC ₂₁ , LC ₂₂ , ...
Are thin film transistors T ₁₁ , T ₁₂ , T ₂₁ ,
T _22, ‥‥ drain electrodes 4,4 ', 4'', 4 ''', ‥
, And a counter electrode 8 sandwiching the counter electrode 8 from the ferroelectric liquid crystal.

Now, by using the above circuit, each pixel shown in FIG.
With a drive waveform as shown in (a), one cycle is 16.7 mS (60 H).
When the reset pulse 101 of z) and the write pulse 102 corresponding to each gradation are applied, the transmittance (T) as shown in FIG. 16B is generated. The transmittance indicated by 103 at this time is a transmittance substantially corresponding to the write pulse 102.
Next, a write pulse 1 having a drive waveform as shown in FIG.
A plot of the transmittance 103 with respect to the pulse height of 02 is the voltage-transmittance characteristic described above. An example thereof is shown in FIG. As is clear from the figure, when the voltage is boosted 104
There is a so-called hysteresis phenomenon in which the transmittance is different between the voltage drop and the step-down time 105.

FIG. 18 qualitatively explained the above hysteresis phenomenon. FIG. 18A corresponds to 104 in FIG. That is, in the direction of reducing the black domain, and from the viewpoint of driving, it is necessary to write white after reset. On the other hand, FIG. 18B shows a direction in which the black domain is increased, and it is not necessary to write white after reset from the viewpoint of driving. That is, in the case of the write pulse, the former (104) requires a larger voltage than the latter (105).

As described above, when the gradation display is performed by the charge control method by the driving method as shown in FIG. 16A, the voltage-transmittance characteristic inevitably has a hysteresis phenomenon.

In addition, in the case of performing the active matrix driving as described above, the continuous application of the direct current voltage (DC) component for a long time during driving hinders the response of the liquid crystal and gradually decreases the transmittance. A problem called "fading phenomenon" occurs.

FIG. 19 shows a fading phenomenon which occurs when a drive waveform as shown in FIG. 16 (a) is applied. FIG. 19
From this, it is clearly seen that the transmittance gradually decreases due to the repeated pulse application.

The fading phenomenon will be described with reference to FIG. In the waveform shown in FIG. 16A, a geometrically positive DC component is excessively applied when viewed from the liquid crystal. FIG. 20 shows how this DC component acts on the liquid crystal. That is, in FIG. 20, positive DC
By applying the components, the insulating layer portions 12 and 12 'and the liquid crystal portion 1
Electric charges are accumulated between 1 and 1, and the partial pressure of the liquid crystal due to the electric charge accumulating component is in the negative direction. As a result, it becomes difficult to write "white".

Similarly, when a voltage is applied to the liquid crystal, charge accumulation occurs due to the spontaneous polarization (P _S ) of the liquid crystal, and the transmittance is not constant during the relaxation time, which is so-called “unstable”. Phenomena also occur.

The above-mentioned hysteresis phenomenon, fading phenomenon and instability phenomenon are very serious problems when the gradation display is performed by the active matrix method because the pixel display voltage cannot be uniquely determined.

A first object of the present invention is to provide an optical modulation element which eliminates the above-mentioned drawbacks. More specifically, the above hysteresis, fading and instability phenomena are reduced, and the liquid crystal orientation is improved. To provide a good optical modulator.

On the other hand, it has been proposed to use an oblique vapor deposition film of SiO, ZrO ₂ or the like as an alignment film in the above optical modulation element.

FIG. 21 shows a conventional example of an active matrix substrate for a liquid crystal display device using such an oblique vapor deposition film. In FIG. 21, a row electrode 601 provided on the substrate
The display pixel (pixel) electrode 603 and the switching thin film transistor (TFT) 60 beside the intersection of the column electrode 602 and the column electrode 602.
4 is incorporated. An alignment film for aligning the liquid crystal is formed on these electrodes and the TFT by the oblique evaporation method. 22 is a sectional view taken along line I-II of the TFT 604 portion in FIG. In FIG. 22, 701
Is a gate electrode of Al, Cr, or the like. A gate insulating film 702 is provided on the gate electrode 701. Further, a drain electrode 705 and a source electrode 706 are provided via an amorphous Si layer 703 and an amorphous Si (n +) layer 704.
There is a pixel electrode 707 connected to this. A protective insulating film 708 and a liquid crystal alignment film 709 are stacked on these.

The oblique vapor deposition method will be described with reference to FIG. In the figure, reference numeral 801 is a vacuum chamber. A vacuum is maintained from the exhaust hole 804 by a diffusion pump, a turbo pump, or the like. From the vapor deposition source 802, vapor deposition is performed on the active matrix substrate 803 for liquid crystal display device at an incident angle θ. Usually, SiO, TiO, or the like is used as the vapor deposition source.
By this method, a vapor deposition film with dense columns is formed,
This vapor deposition film is used as an alignment film for aligning the liquid crystal.

A liquid crystal display device panel by bonding the first substrate (14 in FIG. 14) and the second substrate (14 ') having the counter electrode (13') and injecting liquid crystal (11). Is being made.

However, as shown in FIG. 13, since the transistor portion 604 is projected as compared with other portions,
During vapor deposition of the alignment film, the vapor deposition particles do not reach the shadow of the protrusion, and the vapor deposition film is not formed. Therefore, when injecting liquid crystal,
There has been a problem that alignment defects are generated in the portion where the alignment film is not formed and in the periphery thereof.

The second object of the present invention is to prevent the alignment defect from entering the pixel electrode and to display an image with good brightness and contrast. A third object is to increase the aperture ratio represented by the area occupied by the pixel electrode with respect to the area of the pixel region.

[0023]

In order to achieve the above first object, in a first aspect of the present invention, a liquid crystal layer, a plurality of substrates sandwiching the liquid crystal layer, and the liquid crystal formed on the substrate. In an optical modulation element comprising a voltage applying means for applying a voltage to a layer, on the electrode surface constituting the voltage applying means,
It is characterized in that an alignment film made of an oblique vapor deposition film having a so-called “gap structure” is directly provided, and electric charges are transferred between the liquid crystal layer and the electrode surface through the gap. That is, in the first aspect, layers corresponding to the insulating layers 12 and 12 'of FIG. 14 and the protective insulating film 708 of FIG. 22 are not provided.

In order to achieve the above second and third objects, in the second aspect of the present invention, the pixel electrodes arranged side by side in a matrix along the row electrodes and the column electrodes and the pixel electrodes are switched. On a substrate having a thin film transistor for
In an active matrix substrate for an optical modulation element, in which an alignment film for aligning liquid crystal is formed by an oblique evaporation method, when performing oblique evaporation, the thin film transistor is shaded by a projection of the thin film transistor in the row electrode or column electrode. It is characterized by being placed so that it fits in or is almost settled. In the second aspect, the layers corresponding to the insulating layers 12 and 12 ′ of FIG. 14 and the protective insulating film 708 of FIG. 22 may or may not be provided.

[0025]

According to the first aspect described above, since the liquid crystal layer and the electrodes are electrically conductive by using the orthorhombic vapor deposition film having a so-called gap structure as the alignment film, the above hysteresis and fading are caused in the active matrix driving. In addition, gradation display without instability can be made possible, and good alignment state can be made possible.

Further, according to the second aspect, since the arrangement of the thin film transistors is considered so that the alignment defect does not occur in the display pixel even if it occurs on the electrode, the aperture ratio is increased and the brightness is increased. , It is possible to display an image with good contrast.

The optical modulator that can be used in the present invention includes
Has a first optically stable state (eg, to form a bright state) and a second optically stable state (eg, to form a dark state) in response to an applied electric field; A substance having two stable states, particularly a liquid crystal having such a property, is optimal.

As the liquid crystal having at least two stable states which can be used in the optical modulation element of the present invention, a chiral smectic liquid crystal having ferroelectricity is most preferable, and a chiral smectic C phase (SmC) among them is most preferable.
^* ), H phase (SmH ^* ), I phase (SmI ^* ), F phase (S
Liquid crystals of mF ^* ) or G phase (SmG ^* ) are suitable.

More specifically, desiloxybenzylidene-P'-amino-2-methylbutyl cinnamate (DO
BAMBC), hexyloxybenzylidene-P'-amino-2-chloropropylcinnamate (HOBACP)
C) and 4-o- (2-methyl) -butylresorcylidene-4′-octylaniline (MBRA8) and the like.

When a device is constructed using these materials, the liquid crystal compound is composed of SmC ^* , SmH ^* , SmI.
^In order to maintain the temperature state such that ^* , SmF ^* , or SmG ^* , the element can be supported by a copper block or the like in which a heater is embedded, if necessary.

FIG. 24 is a schematic drawing of an example of a ferroelectric liquid crystal cell. 14 and 14 'are ITO (In
It is a substrate (glass plate) coated with a transparent electrode such as aluminum oxide (Din Tin Oxide), and an SmC ^* phase liquid crystal 11 oriented so that the liquid crystal molecular layer is perpendicular to the glass surface is enclosed between the substrates. A thick line 201 represents a liquid crystal molecule, and the liquid crystal molecule 201 has a dipole moment (P⊥) 202 in a direction orthogonal to the molecule. When a voltage above a certain threshold is applied between the electrodes (not shown) on the substrates 14 and 14 ', the helical structure of the liquid crystal molecules 201 is unraveled, and all the dipole moments (P⊥) 202 are oriented in the electric field direction. The alignment direction of the liquid crystal molecules 201 can be changed. The liquid crystal molecule 201 has an elongated shape, and exhibits refractive index anisotropy in the major axis direction and the minor axis direction thereof. Therefore, for example, if polarizers arranged in a crossed Nicol positional relationship are placed above and below a glass surface. It is easy to understand that the liquid crystal optical modulator has optical characteristics that change depending on the voltage application polarity.

When the thickness of the liquid crystal cell is made sufficiently thin (for example, 1 μm), when an electric field E or E ′ having different polarities equal to or higher than a certain threshold is applied, the dipole moment changes the electric field E as shown in FIG. Or, depending on the electric field vector of E ′, the direction is turned upward 203 or downward 204,
In response, the liquid crystal molecules are aligned in either the first stable state 205 (bright state) or the second stable state 206 (dark state).

There are two advantages of using such a ferroelectric liquid crystal as an optical modulator. Firstly, the response speed is extremely fast, and secondly, the alignment of the liquid crystal molecules has bistability. The second advantage will be described with reference to FIG. 25, for example. When an electric field E is applied, the liquid crystal molecules are in the first stable state 2
Although it is oriented to 05, this state is
Stable state 205 is maintained, and the opposite electric field E'is maintained.
When the voltage is applied, the liquid crystal molecules are oriented in the second stable state 206 and change their orientation, but they are kept in this state even when the electric field is cut off, and each stable state has a memory function. In order to effectively realize such a high response speed and bistability, the cell is preferably as thin as possible, generally 0.5 to 20 μm, and particularly 1 to 5 μm.
m is suitable.

A liquid crystal-electro-optical device having a matrix electrode structure using this type of ferroelectric liquid crystal has been proposed in, for example, US Pat. Nos. 4,367,924 and 4,840,4102.

[0035]

EXAMPLES Example 1 Examples of the present invention will be described below.

FIG. 1 is a basic configuration diagram of an optical modulator according to an embodiment of the present invention. In FIG. 1, 14, 14 '
Is a substrate, 13 and 13 'are transparent electrodes made of an ITO film, 1
Reference numerals 0 and 10 'are oblique vapor deposition alignment films made of Si0, and 11 is a ferroelectric liquid crystal.

The substrates 14 and 14 'were made of non-alkali glass having a thickness of 1.1 mm and having both sides polished (N made by HOYA).
A40). The ITO films 13 and 13 'were formed to 700 Å by the reactive ion plating method in O ₂ .

Further, the SiO oblique vapor deposition alignment films 10 and 10 '.
Was produced by the vapor deposition apparatus shown in FIG. In FIG. 2, 2
0 is a vacuum chamber, 21 is a substrate (substrate 14 or 14 'in FIG. 1), 22 is a chimney crucible which is a SiO evaporation source,
23 is the power source of the evaporation source 22, 24 is a slit, 25 is a roller for sending the substrate 21, 26 is a rotary pump, 27 is a mechanical booster pump, 28 is a cryopump, 2
9, 29 'are switching valves.

The SiO particles emitted from the evaporation source 22 reach the substrate 21 through the slit 24. On the other hand, the roller 25 rotates at the angular velocity ω, which causes the substrate 21 to move at a constant velocity v.
Are moving in. Further, the substrate has an inclination of θ as shown in the figure, and only the SiO particles having an angle component of θ can reach the substrate 21 by the slit 24. Table 1 shows vapor deposition conditions in this example.

[0040]

[Table 1]

The SiO oblique vapor deposition alignment film 10 was formed by the above method.
(FIG. 1) A spin coating of 1.5 μmφ silica beads as a gap agent is applied on the alignment film of the substrate 14 prepared in FIG.
A cell was prepared by superposing it on the counter substrate 14 ′ prepared with 0 ′, and a ferroelectric liquid crystal was vacuum-injected into the cell to prepare an optical modulation element.

FIG. 3 is an enlarged cross-sectional view of the pixel electrode side of the optical modulator of FIG. In FIG. 3, 11 is a ferroelectric liquid crystal, 14 is a glass substrate, 6 is a TFT, 13 is a pixel electrode made of ITO, 9 is an SiO column forming the SiO oblique vapor deposition alignment film 10, and 1a is a gate signal line. .. TFT6
Is connected to the pixel electrode 13 and switches the write signal V _W or the reset signal V _R by the gate signal to guide the signal to the pixel electrode 13. On the other hand, the alignment film (10 ') is also configured in the same manner as above on the counter electrode (13') side (not shown), and the electrode (13 ') is kept at the ground potential.

FIG. 1 shows an optical modulator having the above structure.
6 (a) constant reset and write voltage 10
4 shows write voltage-transmittance (VI) characteristics when continuously driven by a signal having 1, 102.
It is shown by 1. Compared with the VT characteristic 42 of the conventional polyimide rubbing cell corresponding to 104 and 105 in FIG. 17, it can be seen that the VT characteristic 41 of this embodiment has a clearly reduced hysteresis.

FIG. 5 shows the correlation of the all-white writing response time when the black reset leaving time is changed. In FIG.
Reference numeral 51 is the response time of the optical modulation element using the alignment film of this embodiment (corresponding to the characteristic 41 in FIG. 4), and 52 is the response time of the optical modulation element using the conventional polyimide rubbing alignment film (FIG. 4).
(Corresponding to the characteristic 42) of It can be seen that the above-mentioned instability is apparently eliminated by using the alignment film of this example.

FIG. 6 shows that after left "black" for a certain time, "white"
The change in transmissivity when halftone writing is performed is shown. In the figure,
Reference numeral 61 represents a change in transmittance of the optical modulator of the present embodiment. It can be seen that the above-mentioned fading phenomenon is extremely small and hardly seen compared with the transmittance change 62 of the element using the conventional polyimide rubbing alignment film.

The reason for solving the problem that occurs when performing the gradation display of the ferroelectric liquid crystal according to the present embodiment is explained as follows. That is, as schematically shown in FIG. 3, the SiO column 9 formed by oblique SiO vapor deposition.
Has a so-called "gap structure", the electrode 13
Are partially exposed, so that conductivity is generated at the interface with the liquid crystal layer 11, and as shown in FIG. 3, the write voltage V _W applied to the ferroelectric liquid crystal layer (FIG. 16A). Even if the ion 2 (negative ion in this case) is accumulated on the electrode due to the DC imbalance between the reset voltage V _R and the reset voltage V _R , if the electron e is exchanged at this interface, the ion is neutralized. Conceivable. It is considered that this neutralization phenomenon similarly occurs in the ground electrode 13 'facing the pixel electrode 13. Therefore, it is considered that the anti-electric field generated due to the accumulation of ions on the surface of the alignment film as in the above-mentioned conventional example is not formed.

Next, the alignment state of the optical modulation element of this example was observed by a polarization microscope, and it was found that uniform alignment was achieved. When the tilt angle was measured, θ
Considering that a = 14 to 14.5 ° and the cone angle Θ of the injected ferroelectric liquid crystal is about 15 °, the tilt angle of the element can be extended to a position almost close to the cone angle of the ferroelectric liquid crystal. I found out that Further substrates 14, 14 '
A similar device was prepared using 80 μm thick thin film glass, and the layer structure was measured by the X-ray diffraction method. The X-ray diffraction pattern is shown in FIG. In FIG. 7, the diffraction peak is 1
Since only one is seen, it can be seen that the layer structure of the optical modulation element of the present example is an oblique Bookschulf structure as shown in FIG.

Example 2 Using ZrO ₂ instead of SiO, an oblique vapor deposition alignment film similar to that in Example 1 was formed in the same apparatus as in Example 1. Base pressure -10 ^-7 torr. Deposition rate 5Å / sec, Fig. 2
Was 85 °, and the column length of the oblique deposition film was 400Å.

The above alignment film was used to form a device in the same manner as in Example 1, and the alignment state and the VT characteristic hysteresis, instability and fading phenomenon were measured. As a result, it was confirmed that the orientation was a uniform uniform orientation, and the hysteresis, instability and fading were significantly reduced.

Example 3 Using TiO ₂ instead of SiO, an oblique vapor deposition alignment film similar to that in Example 1 was formed by the same apparatus as in Example 1. Base pressure -10 ^-7 torr. The vapor deposition rate was 5Å / sec, θ in FIG. 2 was 85 °, and the oblique vapor deposition film column length was 400Å.

Using the above-mentioned alignment film, element formation was carried out in the same manner as in Example 1, and the alignment state and VT characteristic hysteresis, instability and fading phenomenon were measured. As a result, it was confirmed that the orientation was a uniform uniform orientation, and the hysteresis, instability and fading were significantly reduced.

Embodiment 4 FIG. 9 shows an active matrix substrate for a liquid crystal display device according to a fourth embodiment of the present invention. In the figure, 601 is a row electrode,
Reference numeral 602 is a column electrode, and 603 is a pixel electrode. A thin film transistor 604 is arranged on the column electrode adjacent to the intersection of the row electrode and the column electrode. The oblique vapor deposition is performed parallel to the column direction (vertical direction in the figure). Although the projection part of the thin film transistor 604 becomes a pillar and the alignment film is not formed in the shadow, the alignment film defect is as shown by 605 in the figure.
It is formed on the column electrode 602. When a panel is manufactured using this substrate, alignment defects due to the absence of the alignment film are hidden by the column electrodes 602. Further, even if the alignment defect extends from the alignment film defect 605 as a nucleus as indicated by 606 in the figure, it is hidden on both electrodes. Therefore, the alignment defect due to the alignment film defect 605 does not affect the pixel, and the following effects can be achieved.

Alignment defects formed because the alignment film is not formed are hidden on the electrodes and a high-contrast image can be obtained.

Since the thin film transistor is on the electrode, the effective pixel area is expanded and the aperture ratio can be increased.

Fifth Embodiment Next, a fifth embodiment of the present invention will be described with reference to FIG. In the figure, 601 is a row electrode, 602 is a column electrode,
Reference numeral 603 is a pixel electrode. A thin film transistor 604 is provided on the row electrode. The deposition direction of oblique deposition is parallel to the row electrodes. At this time, the alignment film defect formed in the shadow of the projection portion of the transistor 604 is formed as indicated by 605 in the drawing. When a panel is manufactured using this substrate, the alignment defects due to the formation of no alignment film are hidden by the row electrodes 601. Even if an alignment defect 606 is formed with the alignment film defect 605 as a nucleus, it is included in the row electrode.
Therefore, the influence on the pixel electrodes is suppressed, the aperture ratio is increased, and an image with high brightness and high contrast can be obtained.

Sixth Embodiment Next, a sixth embodiment of the present invention will be described with reference to FIG. In the figure, 601 is a row electrode, 602 is a column electrode, 6
Reference numeral 03 is a pixel electrode. 604 is a thin film transistor,
It is located at the corner of the pixel electrode adjacent to the intersection of the row electrode and the column electrode. The oblique vapor deposition is performed in the diagonal direction of the pixel electrodes. At this time, the alignment film defect formed in the shadow of the projection portion of the transistor 604 is formed as indicated by 605 in the drawing. When a panel is manufactured using this substrate, alignment defects due to the alignment film not being formed are hidden by both electrodes. Even if an alignment defect 606 is formed with the alignment film defect 605 as a nucleus, it is mostly contained in both electrodes. Therefore, the influence on the pixel electrodes is minimized, the aperture ratio is increased, and an image with high brightness and high contrast can be obtained.

Seventh Embodiment Next, a seventh embodiment of the present invention will be described with reference to FIG. In the figure, 601 is a row electrode, 602 is a column electrode, 6
Reference numeral 03 is a pixel electrode. Reference numeral 604 is a thin film transistor. The oblique vapor deposition is performed in the diagonal direction of the pixel electrodes. At this time, the alignment film defect formed in the shadow of the projection portion of the transistor 604 is formed as indicated by 605 in the drawing. A cross-sectional view of III-IV in the figure is shown in FIG. 6 in the figure
Reference numeral 04 is a thin film transistor protruding portion, and 602 is a column electrode. Further, θ is an incident angle of vapor deposition particles. The length L of the alignment film defect is L = d / tan θ, which is settled in the column electrode. When a panel is manufactured using this substrate, alignment defects due to the alignment film not being formed are hidden by the column electrodes. Even if the alignment defect 606 is formed by using the alignment film defect 605 of FIG. 12 as a nucleus, it is almost contained in the column electrode 602. Therefore, the influence on the pixel electrodes is minimized, the aperture ratio is increased, and an image with high brightness and high contrast can be obtained.

[0058]

As described above, according to the first aspect of the present invention, in a gradation display optical modulation element using a ferroelectric liquid crystal, an oblique vapor deposition film such as SiO is used as an alignment film, and By providing the alignment film directly on the electrode surface, the hysteresis phenomenon, instability and fading phenomenon of the VT characteristic peculiar to the active matrix drive gradation display using the ferroelectric liquid crystal in the uniform uniform orientation are almost eliminated. It has the effect of eliminating it.

According to the second aspect of the present invention, when an alignment film is formed on the active matrix substrate for an optical modulation element by oblique vapor deposition, the shadow of the projection by the thin film transistor for active matrix driving is formed on the substrate. Since the thin film transistors are arranged so as to fit or almost fit in the electrodes or the column electrodes, alignment defects do not enter into the pixel electrodes, and image display with good brightness and contrast can be performed.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of an optical modulator according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an apparatus for producing the alignment film of FIG.

FIG. 3 is a diagram showing a shape of an alignment film in the optical modulation element of FIG.

FIG. 4 is a graph showing a VT characteristic curve of the optical modulation element of FIG. 1 in comparison with a VT characteristic curve of a conventional element.

5 is a graph showing a correlation of all-white writing response time when the black reset leaving time is changed in the optical modulation element of FIG.

FIG. 6 is a time period of “black” in the optical modulator of FIG.
FIG. 6 is a graph showing a change in transmittance when “white” halftone writing is performed after standing.

7 is an X-ray diffraction pattern showing a layer structure of an alignment film in the optical modulation element of FIG.

FIG. 8 is a structural diagram schematically showing the layer structure.

9 to 12 are electrodes in an active matrix substrate for a liquid crystal display according to another embodiment of the present invention,
It is a figure which shows arrangement | positioning of a thin film transistor, an alignment film defect, and an alignment defect.

FIG. 13 shows (III-I of the thin film transistor portion of FIG.
V) is a sectional view.

14 to 18 are explanatory views of a conventional technique.

FIG. 19 is a phenomenon diagram of instability in the above conventional technique.

FIG. 20 is an explanatory diagram of instability in the above conventional technique.

FIG. 21 is a diagram showing an arrangement similar to that of FIG. 9 and the like in a conventional active matrix substrate.

FIG. 22 shows (I-II) of the thin film transistor portion of FIG.
FIG.

FIG. 23 is an explanatory diagram of an oblique vapor deposition method.

24 and 25 are principle explanatory views of an optical modulation element using a ferroelectric liquid crystal.

[Explanation of symbols]

10, 10 ': orientated vapor-deposited alignment film, 11: ferroelectric liquid crystal layer, 13, 13': transparent conductive film, 14, 14 ', 21:
Substrate, 20: vacuum chamber, 22: evaporation source, 23: power source of evaporation source, 24: slit, 25: roller, 26: rotary pump, 27: mechanical booster pump, 2
8: Cryopump, 29, 29 ': Valve, 601:
Row electrodes, 602: column electrodes, 603: picture element electrodes, 604:
Thin film transistor, 605: alignment film defect, 606: alignment defect.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tomoko Murakami 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tomoko Maruyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (16)

[Claims] 1. An optical modulation element comprising a liquid crystal layer, a plurality of substrates sandwiching the liquid crystal layer, and a voltage applying means which is formed on the substrate and applies a voltage to the liquid crystal layer. An optical device, which is formed directly on an electrode surface which constitutes the voltage applying means, has a gap structure in the alignment film, and through which the charge is transferred between the liquid crystal layer and the electrode surface. Modulation element. 2. The voltage applying means comprises at least a pixel electrode, a signal electrode, a scanning electrode and an active switching element, and resetting and writing of the liquid crystal layer are both performed by active matrix driving. The optical modulation element described. 3. The optical modulation element according to claim 1, wherein the material of the oblique vapor deposition alignment film is an inorganic oxide. 4. The optical modulation element according to claim 3, wherein the main component of the inorganic oxide is SiO. 5. The column length of the SiO oblique deposition film is 0.
The optical modulation element according to claim 4, wherein the optical modulation element has a diameter of not less than 01 μm and not more than 0.6 μm. 6. The column angle of the SiO oblique deposition film is 0.
The optical modulation element according to claim 4, wherein the optical modulation element has an angle of -60 °. 7. The optical modulator according to claim 3, wherein the material of the inorganic oxide is ZrO ₂ . 8. The optical modulation element according to claim 3, wherein the material of the inorganic oxide is TiO ₂ . 9. The optical modulation element according to claim 1, wherein the liquid crystal is a ferroelectric liquid crystal. 10. An oblique deposition method of forming an alignment film for aligning liquid crystals on a substrate having pixel electrodes arranged in a matrix along with row electrodes and column electrodes and a thin film transistor for switching the pixel electrodes. In the active matrix substrate for an optical modulation element formed by the above, the thin film transistor is arranged so that the shadow of the projection of the thin film transistor is set in the row electrode or the column electrode or is almost set when the oblique deposition is performed. Active matrix substrate for optical modulator. 11. The vapor deposition direction of the oblique vapor deposition is parallel to a column electrode, a thin film transistor is arranged in the column electrode, and the width of the thin film transistor is less than or equal to the width of the column electrode. Item 1. The active matrix substrate according to item 1. 12. A vapor deposition direction of the oblique vapor deposition is parallel to a row electrode, a thin film transistor is arranged in the row electrode, and a width of the thin film transistor is less than or equal to a width of the row electrode. Item 1. The active matrix substrate according to item 1. 13. The thin film transistor is arranged at a corner of a pixel opening portion adjacent to a crossing portion of a column electrode and a row electrode, and a vapor deposition direction of oblique vapor deposition at this time is a direction from the thin film transistor to the electrode. The active matrix substrate for a liquid crystal display device according to claim 1. 14. The thin film transistor is arranged in a row electrode or in a row electrode, the width of the thin film transistor is less than or equal to the column and row electrode width, and the height of the thin film transistor protrusion is d, and the vapor deposition particle incident angle. Θ,
2. L _min > d / tan θ, where L _min is the minimum value of the distance between the thin film transistor and a straight line extending in the deposition direction on the thin film transistor and intersecting the column or row electrodes. Active matrix substrate. 15. The active matrix substrate according to claim 10, wherein an optical modulation element for a liquid crystal display device is configured by sandwiching a liquid crystal layer together with a counter substrate. 16. The alignment film is formed in direct contact with the electrode surfaces of the rows, columns and picture elements, and the alignment film has a gap structure, and the liquid crystal layer and the electrodes are provided through the gap. 16. The active matrix substrate according to claim 15, wherein charges are transferred to and from the surface.