JP4040377B2 - Method for manufacturing liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for monostabilizing a state so as to eliminate an alignment defect by solving a problem of appearance of the alignment defect subsequent to monostabilization, for example, the alignment defect resulting in appearance of two states in a case of no voltage application, inherent in a conventional monostabilization method. SOLUTION: The method for solving the problem comprises applying a first voltage to a liquid crystal from a temperature of a chiral nematic phase state or of an isotropic phase state as shown in the figure 1 and applying a second voltage with polarity reverse of, and with a magnitude identical to, the first voltage to the liquid crystal at a temperature higher than that to start a phase transition between the chiral nematic phase and a chiral smectic phase, for example, a chiral smectic C phase in carrying out monostabilization treatment.

Description

[0001]
[Field of the Invention]
The present invention relates to a method for manufacturing a liquid crystal display device. More particularly, the present invention relates to a method for manufacturing a liquid crystal display device using a liquid crystal having a smectic phase, for example, a ferroelectric liquid crystal.
[0002]
[Prior art]
Liquid crystal display devices have been growing in demand as flat panel displays due to the advantages of being thin, lightweight, and capable of being driven with low power consumption. Up to now, active matrix type liquid crystal display devices adopting a TN mode using nematic liquid crystals have a problem of narrow viewing angle and slow response speed.
[0003]
In recent years, with respect to the problem of viewing angle, when an observer looks at the display, a film that adjusts to observe the image through a medium with the same refractive index over a wide range is added, and gradation inversion and color are added. Methods such as improving viewing angle characteristics such as misalignment, and improving the viewing characteristics by dividing the alignment direction of the liquid crystal into a plurality of parts have been put into practical use and are effective.
[0004]
However, sufficient characteristics have not been obtained with respect to the response speed of the nematic liquid crystal. Improvements to about 10 ms have been made by reviewing the viscosity of liquid crystal materials, but improvements are still required for application to moving images.
[0005]
As a liquid crystal mode having a response speed faster than that of a nematic liquid crystal, there is a liquid crystal display device using a ferroelectric liquid crystal (Ferroelectric Liquid Crystal: FLC) proposed by Clark and Lagerval (JP-A-56-107216). This FLC has a spontaneous polarization 202 perpendicular to the major axis direction of the liquid crystal molecules 201 as shown in FIG. 12 (A). Since this spontaneous polarization contributes to the response, the FLC uses dielectric anisotropy. It is known that the response speed is one to two digits faster than the nematic liquid crystal.
[0006]
Furthermore, the FLC moves on a virtual cone by applying a voltage, so that it can move in a plane. Therefore, in the viewing angle characteristics, as in the IPS (In Plane Switching) mode, good characteristics can be obtained without adding a special process or using an additive such as a film.
[0007]
When this FLC is applied as a display, the distance between the two substrates is reduced so that the FLC molecules between the substrates have a stable state on either the left or right side of the cone when viewed from the upper side of the substrate, that is, bistable. It can be used as a surface stabilized ferroelectric liquid crystal (Surface Stabilized FLC: SSFLC) display. The potential energy of the FLC molecule at this time is as shown in FIG. 12B, where the horizontal axis is the azimuth angle Ψ 204 of the c-director 203. In this way, since the potential energy has a minimum value at two locations, it takes two stable states, that is, a bistable state.
[0008]
However, in this bistable state, only switching between the two states can be performed, so the polarizer is set to one of the stable states, and the transmitted light with respect to the voltage when the analyzer is placed perpendicularly to it, only displays binary values in black and white. There was a problem that it was difficult to display halftones.
[0009]
Two methods have been reported as methods for solving this problem. For example, a method of changing the driving method is a method of a digital gradation display method using pixel area division gradation, time division gradation, or a combination thereof.
[0010]
The digital gray scale display method can be said to be a drive system that is not easily affected by changes in optical characteristics due to temperature changes of the ferroelectric or antiferroelectric liquid crystal material in gray display. In the pixel area division gradation method, the gradation is realized by selecting a pixel electrode having a weighted and divided area. In the time division gradation method, the time of light passing through the pixel with the weight is set. It is for control.
[0011]
However, in the pixel area division gradation method, a circuit to be controlled and an occupied area increase because one pixel is divided into a plurality of regions. For this reason, the number of gradations that can be realized is limited, and it is difficult to achieve high definition. In the time-division gray scale method, it is necessary to prepare and control a plurality of subframes within the time for displaying one image in order to obtain a gray scale by changing the light transmission time. For this reason, the peripheral circuit for controlling the video is required to operate at high speed.
[0012]
The digital drive method requires complex hardware and software to divide the video in both methods, which requires an increase in circuit and operating frequency, which not only increases power consumption but also increases cost. Leads to an increase.
[0013]
Another method is to use monostable FLC. As one of the methods, there has been reported a method using FLC in which the phase sequence shows an isotropic-chiral nematic phase-chiral smectic C phase. FIG. 13 shows the relationship between this FLC phase sequence and the orientation of liquid crystal molecules. In this liquid crystal, when it is cooled from the isotropic phase 211 or the chiral nematic phase 212 to the chiral smectic C phase 213 as shown in FIG. The FLC molecule tilts. At that time, the normals 214 and 215 of the layers take two states that are bilaterally symmetric with respect to the rubbing direction 216, and the FLC molecule 217 is in a stable state when it is slightly tilted to the left and right from the rubbing direction. On the other hand, uniform orientation can be obtained by applying a mono-stabilization treatment by applying a DC voltage as shown in FIG. 14 when phase transition from at least a chiral nematic phase to a chiral smectic C phase is performed. Is oriented in one direction, and the FLC molecule 219 exhibits monostability in which the stability direction is substantially the rubbing direction 216. As described above, Japanese Patent Application Laid-Open No. 2001-81466 describes a treatment method in which at least a phase transition from a chiral nematic phase to a chiral smectic C phase is effected by cooling while applying a direct-current voltage.
[0014]
In such a monostable FLC mode, since the potential energy of the FLC molecule has only one stable state as shown in FIG. 15, the liquid crystal molecules are tilted when a voltage having a polarity opposite to that of the DC voltage during the monostabilization process is applied. When the voltage is removed, the original stable state is restored. Since this inclination angle can be controlled by the strength of the applied voltage, analog gradation is possible. On the other hand, when a voltage is applied in the direction of mono-stabilization, the liquid crystal molecules hardly move because almost the end of the cone is in a stable state.
[0015]
Therefore, the voltage-transmittance characteristics in the state where the polarizer is aligned in the monostable direction of the FLC molecule and the analyzer is placed in the direction perpendicular thereto show a dark state in one polarity as shown in FIG. The polarity is a Half-V-shaped curve in which the transmitted light intensity increases with the applied voltage. Such a Half-V-shaped monostable FLC mode is said to be a CDR (Continuous Director Rotation) -FLC mode.
[0016]
This CDR-FLC mode is expected to be a liquid crystal display device having a wide viewing angle and a high-speed response. In addition, one of the color display methods taking advantage of high-speed response, which is a field-sequential method using a time-mixing method in which R, G, and B are sequentially blinked at time intervals that human eyes cannot perceive. Application is also expected.
[0017]
This method, when realizing gray scale display such as gray display, has a drawback that it is more susceptible to changes in optical properties due to temperature changes of ferroelectric or antiferroelectric liquid crystal materials than digital gray scale display methods. However, there is a feature that the configuration is simple and the circuit scale can be reduced, and the processing of video data is simple, and a relatively high-definition display device can be made inexpensive.
[0018]
Furthermore, using the Half-V-shaped electro-optic response characteristics, by repeatedly displaying the video display period and the black display period, the outline of the moving object, which is called moving image blurring, becomes unclear when displaying moving images. It is effective against this. The conventional LCD display panel holds the same image until the display cycle of the next frame, but in this method, black is displayed during image display and the previous display is reset. is there.
[0019]
For this reason, in order to suppress the flickering of the display, it is necessary to move at a frequency of at least about twice in this method. When one frame is normally displayed at 16.6 ms, in this method, it is preferable to move the image by a 8.3 ms subframe for video display and an 8.3 ms subframe for black display.
[0020]
That is, the response speed of the liquid crystal needs to be 4 ms or less, more preferably 1 ms or less in consideration of the writing time to the pixel. This is difficult to achieve with current nematic liquid crystal materials.
[0021]
[Problems to be solved by the invention]
When dealing with moving images including high definition, it is desirable to use the Half-V characteristics described above. In order to achieve this, it is necessary to uniformly align and mono-stabilize a liquid crystal material having spontaneous polarization, which is difficult to control the alignment, without defects.
[0022]
However, if a DC voltage is applied to the liquid crystal during monostabilization, charges are accumulated at the interface between the alignment film and the liquid crystal, which adversely affects the alignment of the liquid crystal. In particular, a liquid crystal having spontaneous polarization such as FLC has a great influence on the alignment due to charge accumulation.
[0023]
Therefore, in the conventional monostabilization method as shown in FIG. 14, there is a problem that an orientation failure such as two orientations appearing when no voltage is applied as shown in FIG. The present invention solves the above-described problems, and an object thereof is to provide a monostabilization method that eliminates alignment defects.
[0024]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention applies a first voltage from a chiral nematic phase or an isotropic phase as shown in FIG. 1 when performing a monostabilization treatment, and a chiral nematic phase and a chiral smectic phase, for example, A second voltage having a polarity opposite to that of the first voltage and having the same magnitude is applied at a temperature higher than the temperature at which the phase transition with the chiral smectic C phase starts.
[0025]
That is, the present invention has the following configuration.
[0026]
In a method for manufacturing a liquid crystal display device, which includes a step of applying a voltage to the liquid crystal and monostabilizing the alignment of the liquid crystal after injecting a liquid crystal having a chiral smectic phase, Applying a first voltage at a high temperature, then applying a second voltage having a polarity different from that of the first voltage to the first voltage, and a temperature exhibiting a chiral smectic phase while the second voltage is applied A method for manufacturing a liquid crystal display device.
[0027]
Injecting a liquid crystal having a chiral smectic C phase and then applying a voltage to the liquid crystal to mono-stabilize the alignment of the liquid crystal, a chiral nematic phase-chiral smectic C phase transition is started. A first voltage is applied at a temperature higher than the temperature, and then the second voltage having a polarity different from the first voltage is applied to the first voltage, and the chiral smectic C phase is applied while the second voltage is applied. A method for manufacturing a liquid crystal display device, characterized by cooling to a temperature indicating
[0028]
Using a liquid crystal having an isotropic phase-chiral nematic phase-chiral smectic C phase from the high temperature side, applying a first voltage at a temperature higher than the temperature at which the chiral nematic phase-chiral smectic C phase transition starts, and then A liquid crystal display device, wherein the first voltage is applied to a second voltage having a polarity different from that of the first voltage, and is cooled to a temperature showing a chiral smectic C phase while the second voltage is applied. Manufacturing method.
[0029]
In a method for manufacturing a liquid crystal display device, which includes a step of applying a voltage to the liquid crystal and monostabilizing the alignment of the liquid crystal after injecting a liquid crystal having a chiral smectic phase, the first is performed at a temperature showing an isotropic phase or a chiral nematic phase. The liquid crystal is started to cool while applying a voltage of the first voltage, and the first voltage is applied at a temperature higher than the temperature at which the chiral nematic phase-chiral smectic phase transition starts, and a second voltage having a polarity different from the first voltage is applied. And cooling to a temperature exhibiting a chiral smectic phase.
[0030]
In a method for manufacturing a liquid crystal display device, which includes a step of injecting a liquid crystal having a chiral smectic C phase and then applying a voltage to the liquid crystal to monostabilize the alignment of the liquid crystal, the liquid crystal display device has a temperature at which the isotropic phase or chiral nematic phase is exhibited. The liquid crystal starts to cool while applying a voltage of 1, and the first voltage is changed to a second voltage having a polarity different from that of the first voltage at a temperature higher than a temperature at which a chiral nematic phase-chiral smectic C phase transition starts. Is applied to cool to a temperature exhibiting a chiral smectic C phase.
[0031]
Using a liquid crystal having an isotropic phase-chiral nematic phase-chiral smectic C phase from the high temperature side, starting to cool the liquid crystal while applying the first voltage at a temperature showing the isotropic phase or the chiral nematic phase, Apply a second voltage having a polarity different from that of the first voltage at a temperature higher than a temperature at which a chiral nematic phase-chiral smectic C phase transition is initiated, and cool to a temperature indicating a chiral smectic C phase. A method for manufacturing a liquid crystal display device.
[0032]
The method for manufacturing a liquid crystal display device according to any one of the above structures, wherein the first voltage and the second voltage are DC voltages.
[0033]
In each of the above configurations, the absolute value of the first voltage and the second voltage is a voltage value that is 50% or more of the maximum value of transmittance in the voltage-transmittance characteristics. Manufacturing method.
[0034]
In each of the above-described configurations, the absolute value of the first voltage and the second voltage is a voltage value that is 90% or more of the maximum transmittance in the voltage-transmittance characteristics. Manufacturing method.
[0035]
In each of the above structures, a method for manufacturing a liquid crystal display device, wherein the absolute value of the second voltage is reduced after at least the phase transition to the chiral smectic phase or the chiral smectic C phase is completed.
[0036]
In each of the above structures, a method for manufacturing a liquid crystal display device is characterized in that the absolute value of the second voltage is set to zero before cooling to room temperature from at least the temperature at which the phase transition ends.
[0037]
In each of the above configurations, the liquid crystal display device includes pixel electrodes arranged in a matrix, transistors connected to the pixel electrodes, and a common electrode arranged via the pixel electrodes and the liquid crystal, A method for manufacturing a liquid crystal display device, wherein the first voltage and the second voltage are applied between a pixel electrode and the common electrode.
[0038]
As a result, it is possible to eliminate the bias of charge in the liquid crystal and to obtain good alignment.
[0039]
The present invention described above will be described in detail in the following examples and embodiments. In addition, an Example and embodiment can be combined suitably.
DETAILED DESCRIPTION OF THE INVENTION
Examples of embodiments of the present invention are shown below.
[0040]
A light shielding film is formed on the counter substrate, and a transparent conductive film is formed on the light shielding film. As the transparent conductive film, an indium tin oxide (ITO) film can be used.
[0041]
An alignment film is formed on the active matrix substrate and the counter substrate, and alignment processing is performed. When an alignment film having a low pretilt is used, alignment defects of the ferroelectric liquid crystal can be suppressed, so the pretilt value is preferably 2.0 ° or less, more preferably 1.0 ° or less.
[0042]
Here, polyimide or polyamic acid-based alignment film material is formed by a printing method, baked and then rubbed, but photo-alignment is used, an inorganic film is obliquely deposited, or an ion beam is applied to the dielectric film. The orientation may be controlled by irradiation.
[0043]
Since the scattering spacer is randomly distributed, it is also disposed on the pixel electrode. In the vicinity of the spacer, the alignment of the liquid crystal is disturbed and alignment defects are likely to occur, causing light leakage. Accordingly, it is preferable to provide a photosensitive resin by patterning a predetermined position, for example, above the TFT, the gate wiring, or the source wiring. This not only suppresses liquid crystal defects, but also improves black level display.
[0044]
Furthermore, in order to obtain a good white level, in the case of a transmissive display device, the cell gap is 1.4 to 2.0 μm, although the height of the spacer depends on the value of the refractive index anisotropy of the liquid crystal material. It forms so that it becomes. Here, the cell gap was set to 1.8 μm. Since the scattering spacer and the spacer by the photolithographic technique also cause defects, the cell gap may be formed without being used if the size of the display area of the panel is about 1 inch or less.
[0045]
Next, the counter substrate and the active matrix substrate are bonded with a sealant. When bonded, the rubbing directions of the counter substrate and the active matrix substrate are made parallel or antiparallel to each other. After the sealant is cured, the counter substrate and the active matrix substrate are separated.
[0046]
Subsequently, a liquid crystal material is injected. The liquid crystal material used in the present embodiment is a ferroelectric liquid crystal material having an isotropic phase-chiral nematic phase-chiral smectic C phase series. This material is desirable in that a material having a low viscosity is a high-speed response.
[0047]
After confirming that the liquid crystal material has been injected, the injection port is sealed with a UV curable sealant. In addition, you may perform this sealing after the monostabilization process performed after this.
[0048]
Thereafter, the mono-stabilization process of the ferroelectric liquid crystal is performed as shown in FIG. In FIG. 1, the horizontal axis is temperature, and the vertical axis is applied voltage. The phase sequence of the liquid crystal is isotropic, chiral nematic, and chiral smectic C phase from the high temperature side.
[0049]
Therefore, a phase transition occurs during cooling. Here, the phase transition refers to a phenomenon in which a substance moves to a different phase due to a change in temperature or the like, and occurs over several degrees Celsius. This phase transition can be determined by a differential scanning calorimeter or observation with a polarizing microscope. When measured with a differential scanning calorimeter, the difference between the amount of heat absorbed and the amount of heat generated during phase transition appears as a peak. The temperature width of this peak indicates the temperature width of the phase transition. The temperature at which phase transition starts is the first time when Δq / ΔT <0 or Δq / ΔT> 0 when the horizontal axis is temperature T and the vertical axis is endothermic amount or calorific value q in differential scanning calorimetry. Temperature. In this embodiment, since the monostabilization process is performed while cooling, the temperature at which the phase transition starts is the higher temperature side of the phase transition temperature.
[0050]
The conditions that should be kept at a minimum in performing the mono-stabilization process are the temperature range to which the second voltage is applied and the magnitude of the second voltage.
[0051]
A second voltage is applied in the temperature range in which the state of the chiral smectic C phase is reached after the phase transition from the chiral nematic phase to the chiral smectic C phase. Note that it is desirable to make the period during which the second voltage is applied as narrow as possible. This is to avoid applying a DC voltage to the liquid crystal for a long time.
[0052]
In addition, the second voltage needs to be applied with a voltage sufficient for monostabilization. When this voltage is small, the normal of the layer takes two states that are bilaterally symmetric with respect to the rubbing direction, and the FLC molecules are in a stable state when tilted slightly left and right from the rubbing direction, so that the liquid crystal molecules cannot be aligned in one direction. Therefore, the magnitude of the second voltage may be a voltage value indicating a transmittance of at least 50% of the maximum value of the transmittance in the voltage-transmittance characteristics, and more preferably a voltage value indicating a transmittance of 90% or more. . In an actual panel, the voltage applied to the liquid crystal is about 0 to 10 V. Therefore, the voltage applied to the monostabilization process may be considered as a voltage value therebetween.
[0053]
The monostabilization process starts cooling while applying the first voltage from the chiral nematic phase or the isotropic phase. The temperature at which the first voltage is applied is not particularly limited as long as it is an isotropic phase or a chiral nematic phase. However, the temperature range in which the first voltage is applied is preferably as narrow as possible, similarly to the temperature range in which the second voltage is applied. In order to suppress the bias of the direct current component applied to the liquid crystal, the temperature range in which the first voltage is applied and the temperature range in which the second voltage is applied are preferably approximately the same.
[0054]
Since a large temperature gradient during cooling causes defects, the temperature gradient is preferably −3.0 ° C./min or less, particularly preferably around −1.0 ° C./min.
[0055]
The magnitude of the first voltage is not particularly limited, but a voltage having the same magnitude as the second voltage is preferable.
[0056]
Subsequently, a second voltage having a polarity different from the first voltage is applied at a temperature higher than the temperature at which the chiral nematic phase-chiral smectic C phase transition starts. The temperature at which the application of the second voltage is started is preferably as close to the temperature at which the phase transition is started as much as possible in order to avoid applying a DC voltage to the liquid crystal for a long time. For example, the application of the second voltage is preferably started from a temperature higher than the temperature at which the phase transition between the chiral nematic phase and the chiral smectic C phase starts, more preferably from 0.1 ° C. to 1 ° C. higher. Then, the second voltage is removed immediately after the phase transition. In this way, the temperature range for applying the second voltage is made as narrow as possible.
[0057]
At this time, in the case where ionic impurities are mixed in the panel, if the second voltage is suddenly removed, there is a possibility that alignment failure is caused by the influence of the counter electromotive force. Therefore, the second voltage is preferably set to 0 V while gradually decreasing the voltage after the phase transition. In this way, good orientation is obtained.
[0058]
In this embodiment, the temperature range in which the first voltage is applied and the temperature range in which the second voltage is applied are made as narrow as possible, and orientation caused by accumulation of impurity ions at the interface by applying a DC voltage, etc. Reduce the impact on Further, by making the magnitudes of the first voltage and the second voltage applied to the liquid crystal during cooling equal, it is possible to cancel the bias of the DC component applied to the liquid crystal.
[0059]
【Example】
[Example 1]
In this example, a ferroelectric liquid crystal R2402 manufactured by Clariant Japan was used as the liquid crystal material. The phase transition temperature of this liquid crystal is isotropic phase / chiral nematic phase = 88.6 to 85.9 ° C., chiral nematic phase / chiral smectic C phase 65.8 ° C. (catalog value).
[0060]
A liquid crystal material was injected into the active matrix substrate using a capillary phenomenon, and the injection port was sealed with a UV curable sealant.
[0061]
Thereafter, a monostabilization treatment was performed as shown in FIG. The monostabilization treatment start temperature was 75.0 ° C., and after maintaining in this state for 180 seconds, cooling was started at a cooling rate of −1.2 ° C./min. Simultaneously with the start of cooling, a DC voltage of +6 V as the first voltage was applied to the ferroelectric liquid crystal R2402. The temperature controller used here was a Mettler FP80 manufactured by Mettler.
[0062]
Thereafter, a DC voltage of −6 V, which is the second voltage, was applied at 66.8 ° C., which is 1.0 ° C. higher than the temperature at which the chiral nematic phase-chiral smectic C phase transition is initiated, to cause phase transition. After the transition to the chiral smectic C phase, cooling was performed while applying a constant DC voltage to 62.0 ° C., and then the DC voltage was gradually removed, and good orientation was obtained by cooling to room temperature.
[0063]
[Comparative Example]
In this comparative example, the alignment state of the liquid crystal when the liquid crystal panel used in Example 1 is mono-stabilized while applying a single polarity DC voltage will be described.
[0064]
Once CDR-FLC is monostabilized, the temperature is raised and the phase is changed to a higher temperature phase than the chiral smectic C phase, for example, isotropic phase or chiral nematic phase, and then cooled without voltage application. When transitioning to the C phase, as shown in FIG. 13, the FLC molecule takes two states 217 inclined symmetrically with respect to the rubbing direction 216, and a monostable state cannot be obtained. However, it is possible to regain the original monostable state by performing the monostabilization process again.
[0065]
Therefore, by using the liquid crystal display device used in Example 1 and performing a mono-stabilization process in which only one polarity voltage as shown in FIG. 3 is applied during cooling, a comparison with the method according to the present invention was performed. .
[0066]
As the temperature controller, Mettler FP80 manufactured by Mettler was used. After maintaining the chiral nematic phase at 75.0 ° C. for 180 seconds, cooling was started at a cooling rate of −1.2 ° C./min. At this time, no voltage is applied.
[0067]
Next, a DC voltage of −6 V was applied at 66.9 ° C., which was 1.0 ° C. higher than the temperature at which the chiral nematic phase-chiral smectic C phase transition was initiated, to cause phase transition. Then, after the transition to the chiral smectic C phase, the DC voltage was gradually removed at 62.0 ° C. and then cooled to room temperature to complete the monostabilization treatment.
[0068]
The orientation of the liquid crystal after the monostabilization treatment in which only the voltage of one polarity was applied during cooling was examined. In a configuration in which a liquid crystal panel is sandwiched between two polarizing plates, the angle formed by the optical axis of the polarizing plate is adjusted to make the alignment failure conspicuous, and the alignment after the monostabilization treatment of the present invention shown in Example 1 The number of pixels with poor alignment was confirmed to be large.
[0069]
[Example 2]
In this embodiment, a method for manufacturing an active matrix substrate in which a pixel matrix circuit and a CMOS circuit which is a basic form of a driver circuit provided in the periphery thereof are simultaneously formed will be described with reference to FIGS. A process of manufacturing an active matrix type liquid crystal display device from an active matrix substrate using the above will be described.
[0070]
First, a silicon nitride oxide film 302a was formed as a base film on the substrate 301 to a thickness of 50 to 500 nm, typically 100 nm. The silicon nitride oxide film 302a is made of SiH. _Four And N ₂ O and NH _Three The nitrogen concentration contained is set to be 25 atomic% or more and less than 50 atomic%. After that, heat treatment at 450 to 650 ° C. was performed in a nitrogen atmosphere to densify the silicon nitride oxide film 302a.
[0071]
Further, a silicon nitride oxide film 302b was formed to a thickness of 100 to 500 nm, typically 200 nm, and an amorphous semiconductor film (not shown) was continuously formed to a thickness of 20 to 80 nm. In this embodiment, an amorphous silicon film is used as the amorphous semiconductor film, but a microcrystalline silicon film or an amorphous silicon germanium film may be used.
[0072]
Then, the amorphous silicon film was crystallized by a crystallization means described in Japanese Patent Laid-Open No. 7-130652 (corresponding to US Pat. No. 5,643,826) to form a crystalline silicon film (not shown). . The technology described in the publication is a catalyst element (one or more elements selected from nickel, cobalt, germanium, tin, lead, palladium, iron, and copper) that promotes crystallization when crystallizing an amorphous silicon film. , Typically nickel). Specifically, heat treatment is performed with the catalytic element held on the surface of the amorphous silicon film to change the amorphous silicon film into a crystalline silicon film.
[0073]
After the crystalline silicon film is formed in this way, the remaining amorphous component is crystallized by irradiating with excimer laser light, thereby improving the overall crystallinity. The excimer laser light may be either a pulse oscillation type or a continuous oscillation type, but can be applied to a large substrate by processing the beam shape into a linear shape and irradiating it.
[0074]
Next, the crystalline silicon film was patterned to form active layers 303 to 306, and a gate insulating film 307 was formed to cover them. The gate insulating film 307 is made of SiH _Four And N ₂ A silicon nitride oxide film formed from O, which is formed to have a thickness of 10 to 200 nm, preferably 50 to 150 nm. (Fig. 4 (A))
[0075]
Next, resist masks 308 to 311 were formed to cover the entire surfaces of the active layers 303 and 306 and part of the active layers 304 and 305 (including the channel formation region). And phosphine (PH _Three N) which becomes an Lov region or a Loff region after an impurity element imparting n-type (phosphorus in this embodiment) is added by an ion doping method using ^- Regions 312 to 314 were formed. In this step, the acceleration voltage was set to 65 keV in order to add phosphorus to the active layer therebelow through the gate insulating film 307. The concentration of phosphorus added to the active layer is 2 × 10 ¹⁶ ~ 5x10 ¹⁹ atoms / cm ^Three In the range of 1 × 10 ¹⁸ atoms / cm ^Three It was. (Fig. 4 (B))
[0076]
Next, the first conductive film 315 was formed using tantalum nitride (TaN) by a sputtering method. Subsequently, a second conductive film 316 containing aluminum (Al) as a main component was formed to a thickness of 100 to 300 nm. (Fig. 4 (C))
[0077]
Then, the wiring 317 was formed by etching the second conductive film. In the case of this example, since the second conductive film is Al, the selectivity with respect to the underlying TaN film by the phosphoric acid solution was good. Further, a third conductive film 318 was formed using tantalum (Ta) to a thickness of 100 to 400 nm (200 nm in this embodiment) over the first conductive layer 315 and the wiring 317. A tantalum nitride film may be further formed on the tantalum film. (Fig. 4 (D))
[0078]
Next, resist masks 319 to 324 are formed, and the first conductive film and a part of the third conductive film are removed by etching, so that the low resistance connection wiring 325, the gate wiring 326 of the p-channel TFT, the pixel matrix A gate wiring 327 of the circuit was formed. Note that the conductive films 328 to 330 are left over a region to be an n-channel TFT. The connection wiring 325 is formed in a portion where the wiring resistance is minimized (for example, a wiring portion from the input / output terminal of the external signal to the input / output terminal of the driver circuit). However, since the wiring width is increased to some extent due to the structure, it is not suitable for a portion requiring fine wiring.
[0079]
The etching of the first conductive film (TaN film) and the second conductive film (Ta film) is CF _Four And O ₂ It was possible to carry out with a mixed gas of Then, a process of adding an impurity element imparting p-type to a part of the active layer 303 where the p-channel TFT is formed is performed while leaving the resist masks 319 to 324 as they are. Here, boron is used as the impurity element and diborane (B ₂ H ₆ ) Using an ion doping method (of course, an ion implantation method may be used). Boron concentration is 5 × 10 ²⁰ ~ 3x10 ^{twenty one} atoms / cm ^Three (In this embodiment, 2 × 10 ^{twenty one} atoms / cm ^Three ). And p with boron added at high concentration ⁺⁺ Regions 331 and 332 were formed. (Fig. 5 (A))
[0080]
Note that in this step, the gate insulating film 307 may be etched using the resist masks 319 to 324 as a mask to expose part of the active layer 303, and then boron may be added. In that case, since the acceleration voltage is low, the damage to the active layer is small and the throughput is improved.
[0081]
Next, after removing the resist masks 319 to 324, new resist masks 333 to 338 were formed. This is for forming the gate wiring of the n-channel TFT, and the gate wirings 339 to 341 of the n-channel TFT were formed by the dry etching method. At this time, the gate wirings 339 and 340 are n ^- It was formed so as to overlap with a part of the regions 312 to 314. (Fig. 5 (B))
[0082]
Next, after removing the resist masks 333 to 338, new resist masks 342 to 346 were formed. The resist masks 344 and 346 are n-channel TFT gate wirings 340 and 341 and n ^- It was formed so as to cover a part of the region.
[0083]
Then, an impurity element imparting n-type (phosphorus in this embodiment) is added at 1 × 10 ²⁰ ~ 1x10 ^{twenty one} atoms / cm ^Three (In this embodiment, 5 × 10 ²⁰ atoms / cm ^Three ) To the active layers 304 to 306 ⁺ Regions 347 to 353 were formed. (Fig. 5 (C))
[0084]
Note that in this step, a step of adding phosphorus may be performed after the gate insulating film 307 is removed by etching using the resist masks 342 to 346 to expose part of the active layers 304 to 306. In that case, since the acceleration voltage is low, the damage to the active layer is small and the throughput is improved.
[0085]
Next, a step of removing the resist masks 342 to 346 and adding an impurity element imparting n-type (phosphorus in this embodiment) to the active layer 306 to be an n-channel TFT of the pixel matrix circuit was performed. Thus, the n ^- A concentration of 1/2 to 1/10 of the region (specifically, 1 × 10 ¹⁶ ~ 5x10 ¹⁸ atoms / cm ^Three ) With phosphorus added ^- Regions 354 to 357 were formed.
[0086]
In this step, all impurity regions except for the impurity regions 358 to 360 hidden by the gate wiring are formed in n. ^- Phosphorus was added at a concentration of. In fact, the concentration is so low that it can be ignored. However, strictly speaking, the region indicated by 359 and 360 is n ^- The area indicated by 361 and 362 is (n ^- + N ^- ) Region, and said n ^- It contains phosphorus at a slightly higher concentration than regions 359, 360. (Fig. 6 (A))
[0087]
Next, a protective insulating film 363 having a thickness of 100 to 400 nm is formed on the SiH film by plasma CVD. _Four , N ₂ O, NH _Three The silicon nitride oxide film was used as a raw material. It was desirable to form the silicon nitride oxide film so that the hydrogen concentration in the silicon nitride oxide film was 1 to 30 atomic%. As the protective insulating film 344, a silicon oxide film, a silicon nitride film, or a stacked film including a combination thereof can be used.
[0088]
Thereafter, a heat treatment process was performed to activate the impurity element imparting n-type or p-type added at each concentration. This step can be performed by a furnace annealing method, a laser annealing method, or a rapid thermal annealing method (RTA method). Here, the activation process was performed by furnace annealing. The heat treatment was performed in a nitrogen atmosphere at 300 to 650 ° C., preferably 400 to 550 ° C., here 450 ° C. for 2 hours.
[0089]
Further, a process of hydrogenating the active layer was performed by performing heat treatment at 300 to 450 ° C. for 1 to 12 hours in an atmosphere containing 3 to 100% hydrogen. This step is a step of terminating dangling bonds in the semiconductor layer with thermally excited hydrogen. As another means of hydrogenation, plasma hydrogenation (using hydrogen excited by plasma) may be performed. (Fig. 6 (B))
[0090]
After the activation process, an interlayer insulating film 364 having a thickness of 0.5 to 1.5 μm was formed on the protective insulating film 363. A laminated film composed of the protective insulating film 363 and the interlayer insulating film 364 was used as a first interlayer insulating film.
[0091]
Thereafter, contact holes reaching the source region or the drain region of each TFT were formed, and source wirings 365 to 368 and drain wirings 369 to 372 were formed. Although not shown, the drain wirings 369 and 370 are connected as the same wiring in order to form a CMOS circuit. Further, connection wirings 373 and 374 connecting the input / output terminals and the circuits were formed at the same time. Although not shown, in this embodiment, this electrode is a laminated film having a three-layer structure in which a Ti film is formed to 100 nm, an aluminum film containing Ti is 300 nm, and a Ti film is formed to 150 nm by sputtering.
[0092]
Next, a passivation film 375 was formed using a silicon nitride film, a silicon oxide film, or a silicon nitride oxide film with a thickness of 50 to 500 nm (typically 200 to 300 nm). The passivation film 375 is formed by plasma CVD using SiH. _Four , N ₂ O, NH _Three Silicon nitride oxide film formed from SiH or SiH _Four , N ₂ , NH _Three It may be formed of a silicon nitride film manufactured from the above.
[0093]
First, prior to film formation, N ₂ O, N ₂ , NH _Three Etc. were introduced and a hydrogenation step was performed by plasma hydrogenation treatment. Hydrogen excited by the plasma treatment is supplied into the first interlayer insulating film, and if the substrate is heated to 200 to 400 ° C., the active layer can be hydrogenated by diffusing the hydrogen to the lower layer side. did it. The conditions for producing this passivation film are not particularly limited, but a dense film is desirable.
[0094]
Further, after forming the passivation film, a hydrogenation step may be further performed. For example, heat treatment may be performed at 300 to 450 ° C. for 1 to 12 hours in an atmosphere containing 3 to 100% hydrogen, or the same effect can be obtained by using a plasma hydrogenation method. Note that an opening may be formed in the passivation film 375 at a position where a contact hole for connecting the pixel electrode and the drain wiring is formed later.
[0095]
Thereafter, a second interlayer insulating film 376 made of an organic resin was formed to a thickness of about 1 μm. As the organic resin, polyimide, acrylic, polyamide, polyimide amide, BCB (benzocyclobutene), or the like can be used. Advantages of using the organic resin film are that the film forming method is simple, the relative dielectric constant is low, the parasitic capacitance can be reduced, and the flatness is excellent. Note that organic resin films other than those described above, organic SiO compounds, and the like can also be used. Here, it was formed by baking at 300 ° C. using a type of polyimide that is thermally polymerized after being applied to the substrate.
[0096]
Next, a shielding film 377 was formed over the second interlayer insulating film 376 in a region to be a pixel matrix circuit. The shielding film 377 is a film having an element selected from aluminum (Al), titanium (Ti), and tantalum (Ta) or any one of them as a main component and formed to a thickness of 100 to 300 nm. Note that when an insulating film such as a silicon oxide film was formed to a thickness of 5 to 50 nm on the second interlayer insulating film 376, the adhesion of the shielding film formed thereon could be improved. Further, CF is formed on the surface of the second interlayer insulating film 376 formed of an organic resin. _Four When the plasma treatment using gas was performed, the adhesion of the shielding film formed on the film by surface modification could be improved.
[0097]
In addition to the shielding film, other connection wirings can be formed. For example, it is possible to form a connection wiring that connects the circuits in the driver circuit. However, in that case, it is necessary to form a contact hole in the second interlayer insulating film in advance before forming the material for forming the shielding film or the connection wiring.
[0098]
Next, an anodic oxide film 378 having a thickness of 10 to 100 nm (preferably 15 to 75 nm) was formed on the surface of the shielding film 377 by an anodic oxidation method. In this embodiment, since an aluminum film or a film mainly composed of aluminum is used as the shielding film 377, an aluminum oxide film (alumina film) is formed as the anodic oxide film 378.
[0099]
At the time of anodizing treatment, an ethylene glycol tartrate solution having a sufficiently low alkali ion concentration was first prepared. This was a solution in which 15% ammonium tartrate aqueous solution and ethylene glycol were mixed at a ratio of 2: 8, and aqueous ammonia was added thereto to adjust the pH to 7 ± 0.5. Then, a platinum electrode serving as a cathode is provided in the solution, the substrate on which the shielding film 377 is formed is immersed in the solution, and a constant (several mA to several hundred mA) direct current is passed using the shielding film 377 as an anode. . The current density is 1.0 mA / cm ² ~ 20.0mA / cm ² It is preferable to perform anodization while controlling within this range.
[0100]
In this example, a current of 100 mA was passed through one substrate, and the voltage value per unit time was 87 to 430 V / min. The voltage between the cathode and the anode in the solution changes with time as the oxide film grows. However, the voltage was adjusted so that the current became constant, and the operation was terminated when the voltage reached 35V. The anodic oxidation process time in this example was 7 seconds.
[0101]
Thus, an anodic oxide film 378 having a thickness of 20 to 30 nm could be formed on the side surface of the end portion of the shielding film 377. The numerical values related to the anodic oxidation method shown here are only examples, and the optimum values can naturally vary depending on the size of the element to be manufactured.
[0102]
Although the insulating film is provided only on the surface of the shielding film here, the insulating film may be formed by a vapor phase method such as a plasma CVD method, a thermal CVD method, or a sputtering method. In that case also, the film thickness is preferably 30 to 150 nm (preferably 50 to 75 nm). Alternatively, a silicon oxide film, a silicon nitride film, a silicon nitride oxide film, a DLC (Diamond like carbon) film, or an organic resin film may be used. Further, a laminated film combining these may be used.
[0103]
Next, a contact hole reaching the drain wiring 372 was formed in the second interlayer insulating film 376 and the passivation film 375, and a pixel electrode 379 was formed. Note that the pixel electrodes 380 and 381 are pixel electrodes of different adjacent pixels. The pixel electrodes 379 to 381 use a transparent conductive film in the case of a transmissive liquid crystal display device, and a reflective metal film (for example, aluminum, silver, Al-Ag) in the case of a reflective liquid crystal display device. An alloy or the like) may be used. Here, in order to obtain a transmissive liquid crystal display device, an indium tin oxide (ITO) film was formed to a thickness of 100 nm by sputtering.
[0104]
At this time, a region 382 in which the pixel electrode 379 and the shielding film 377 overlap with each other with the anodic oxide film 378 formed a storage capacitor.
[0105]
Thus, an active matrix substrate having a CMOS circuit and a pixel matrix circuit as a driver circuit on the same substrate was completed. Note that a p-channel TFT 501 and n-channel TFTs 502 and 503 are formed in the driver circuit, and a pixel TFT 504 made of an n-channel TFT is formed in the pixel matrix circuit. (Fig. 6 (C))
[0106]
In the p-channel TFT 501 of the CMOS circuit, a channel formation region 401, a source region 402, and a drain region 403 are each p. ⁺ Formed in the region.
[0107]
In the n-channel TFT 502, a channel formation region 404, a source region 405, a drain region 406, and a Lov region 407 are formed on one side of the channel formation region. At this time, the source region 405 has (n ^- + N ⁺ ) Region and drain region 406 are (n ^- + N ^- + N ⁺ ) Region, and the Lov region 407 is n ^- Formed in the region. The Lov region 407 is formed so as to overlap with the gate wiring.
[0108]
In the n-channel TFT 503, a channel formation region 408, a source region 409, a drain region 410, and Lov regions 411a and 412a and Loff regions 411b and 412b are formed on both sides of the channel formation region. At this time, the source region 409 and the drain region 410 are (n ^- + N ^- + N ⁺ ) Region, Lov regions 411a, 412a are n ^- Region, Loff regions 411b and 412b are (n ^- + N ^- ) Formed in each region. In this structure, the Lov region and the Loff region are realized because part of the LDD region is arranged so as to overlap the gate wiring.
[0109]
Further, the pixel TFT 504 includes n in contact with the channel formation regions 413 and 414, the source region 415, the drain region 416, the Loff regions 417 to 420, and the Loff regions 418 and 419. ⁺ Region 421 was formed. At this time, the source region 415 and the drain region 416 are each (n ^- + N ⁺ ) Region, and the Loff regions 417 to 420 are n ^- Formed in the region.
[0110]
In this example, the structure of the TFT forming each circuit was optimized according to the circuit specifications required by the pixel matrix circuit and the driver circuit, and the operation performance and reliability of the semiconductor device could be improved. Specifically, n-channel TFTs have a low LDD region arrangement according to circuit specifications and use different Lov regions or Loff regions. A TFT structure with an emphasis on off-current operation was realized.
[0111]
For example, in the case of an active matrix liquid crystal display device, the n-channel TFT 502 is suitable for logic circuits such as a shift register circuit, a frequency dividing circuit, a signal dividing circuit, a level shifter circuit, and a buffer circuit that place importance on high-speed operation. That is, by arranging the Lov region only on one side (drain region side) of the channel formation region, a structure in which the resistance component is reduced as much as possible and the hot carrier countermeasure is emphasized. This is because in the case of the above circuit group, the functions of the source region and the drain region are not changed, and the direction in which carriers (electrons) move is constant. However, Lov regions can be arranged on both sides of the channel formation region as necessary.
[0112]
Further, the n-channel TFT 503 is suitable for a sampling circuit (sample hold circuit) that places importance on both hot carrier countermeasures and low off-current operation. That is, the arrangement of the Lov region is used as a countermeasure against hot carriers, and further, the low off current operation is realized by arranging the Loff region. In addition, since the functions of the source region and the drain region are inverted and the carrier moving direction is changed by 180 °, the sampling circuit must be structured so as to be symmetric with respect to the gate wiring. In some cases, only the Lov region may be used.
[0113]
The n-channel TFT 504 is suitable for a pixel matrix circuit and a sampling circuit (sample hold circuit) that place importance on low off-current operation. That is, a low off-current operation is realized by arranging only the Loff region without arranging the Lov region that can increase the off-current value. Further, by using an LDD region having a lower concentration than the LDD region of the driver circuit as the Loff region, a measure is taken to thoroughly reduce the off-current value even if the on-current value slightly decreases. N ⁺ It has been confirmed that the region 321 is very effective in reducing the off-current value.
[0114]
The length (width) of the Lov region 407 of the n-channel TFT 502 may be 0.5 to 3.0 μm, typically 1.0 to 1.5 μm, with respect to the channel length of 3 to 7 μm. The length (width) of the Lov regions 411a and 412a of the n-channel TFT 503 is 0.5 to 3.0 μm, typically 1.0 to 1.5 μm, and the length (width) of the Loff regions 411b and 412b. May be 1.0 to 3.5 μm, typically 1.5 to 2.0 μm. The length (width) of the Loff regions 417 to 420 provided in the pixel TFT 504 may be 0.5 to 3.5 μm, typically 2.0 to 2.5 μm.
[0115]
Another feature is that the p-channel TFT 501 is formed in a self-aligned manner and the n-channel TFTs 502 to 504 are formed in a non-self-aligned manner (non-self-aligned).
[0116]
Next, a process for manufacturing an active matrix liquid crystal display device from an active matrix substrate will be described.
[0117]
As shown in FIG. 7, an alignment film 601 is formed on the substrate in the state of FIG. Usually, a polyimide resin is often used for the alignment film of the liquid crystal display element. A counter electrode 603 made of a transparent conductive film and an alignment film 604 were formed on the counter substrate 602. After the alignment film was formed, rubbing treatment was performed so that the liquid crystal molecules were aligned with a certain pretilt angle. Then, the pixel matrix circuit, the active matrix substrate on which the CMOS circuit is formed, and the counter substrate are bonded to each other through a sealing material, a spacer (both not shown), or the like by a known cell assembling process. Thereafter, a liquid crystal material 605 was injected between both substrates and completely sealed with a sealant (not shown). A liquid crystal material having a known smectic phase may be used as the liquid crystal material. In this example, a ferroelectric liquid crystal R2402 manufactured by Clariant Japan was used as the liquid crystal material.
[0118]
Subsequently, a monostabilization process was performed as shown in FIG. The monostabilization treatment start temperature was 75.0 ° C., and after maintaining in this state for 180 seconds, cooling was started at a cooling rate of −1.2 ° C./min. Simultaneously with the start of cooling, a DC voltage of +6 V as the first voltage was applied to the ferroelectric liquid crystal R2402. Note that a voltage was applied to the liquid crystal using a drive circuit so that a DC voltage could be applied to all the pixels simultaneously.
[0119]
Thereafter, a DC voltage of −6 V, which is the second voltage, was applied at 66.8 ° C., which is 1.0 ° C. higher than the temperature at which the chiral nematic phase-chiral smectic C phase transition is initiated, to cause phase transition. After the transition to the chiral smectic C phase, cooling was performed while applying a constant DC voltage to 62.0 ° C., and then the DC voltage was gradually removed, and good orientation was obtained by cooling to room temperature. In this way, the active matrix type liquid crystal display device shown in FIG. 7 was completed.
[0120]
In this embodiment, an alumina film having a high relative dielectric constant of 7 to 9 is used as the dielectric of the storage capacitor, so that the storage capacitor can be increased. Therefore, even when a smectic liquid crystal having spontaneous polarization is used as the liquid crystal material, the amount of voltage drop due to inversion of the spontaneous polarization can be reduced.
[0121]
Example 3
A perspective view of the liquid crystal display device fabricated in Example 2 is shown in FIG. Note that FIG. 8 uses common reference numerals in order to correspond to the cross-sectional structure diagrams of FIGS.
[0122]
The active matrix substrate includes a pixel matrix circuit 1401, a scanning (gate) line driving circuit 1402, and a signal (source) line driving circuit 1403 formed on the glass substrate 301. A pixel TFT 504 of the pixel matrix circuit is an n-channel TFT, and a driver circuit provided in the periphery is configured based on a CMOS circuit. The scanning (gate) line driving circuit 1402 and the signal (source) line driving circuit 1403 are connected to the pixel matrix circuit 1401 by a gate wiring 341 and a source wiring 368, respectively. In addition, connection wirings 1407 and 1408 are provided from the external input / output terminal 1405 to which the FPC 1404 is connected to the input / output terminal of the driver circuit.
[0123]
Example 4
The liquid crystal display device formed by implementing any one of Embodiments 1 to 3 can be used for various electro-optical devices. That is, the present invention can be applied to all electronic devices in which these electro-optical devices are incorporated in a display unit.
[0124]
Such electronic devices include video cameras, digital cameras, projectors, head-mounted displays (goggles type displays), car navigation systems, car stereos, personal computers, personal digital assistants (mobile computers, mobile phones, electronic books, etc.), etc. Can be mentioned. Examples of these are shown in FIGS. 9, 10 and 11.
[0125]
FIG. 9A illustrates a personal computer, which includes a main body 2001, an image input portion 2002, a display portion 2003, a keyboard 2004, and the like. The present invention can be applied to the display portion 2003.
[0126]
FIG. 9B shows a video camera, which includes a main body 2101, a display portion 2102, an audio input portion 2103, operation switches 2104, a battery 2105, an image receiving portion 2106, and the like. The present invention can be applied to the display portion 2102.
[0127]
FIG. 9C illustrates a mobile computer, which includes a main body 2201, a camera unit 2202, an image receiving unit 2203, an operation switch 2204, a display unit 2205, and the like. The present invention can be applied to the display portion 2205.
[0128]
FIG. 9D shows a goggle type display, which includes a main body 2301, a display portion 2302, an arm portion 2303, and the like. The present invention can be applied to the display portion 2302.
[0129]
FIG. 9E shows a player using a recording medium (hereinafter referred to as a recording medium) on which a program is recorded, and includes a main body 2401, a display portion 2402, a speaker portion 2403, a recording medium 2404, an operation switch 2405, and the like. This player uses a DVD (Digital Versatile Disc), CD, or the like as a recording medium, and can perform music appreciation, movie appreciation, games, and the Internet. The present invention can be applied to the display portion 2402.
[0130]
FIG. 9F shows a digital camera, which includes a main body 2501, a display portion 2502, an eyepiece portion 2503, operation switches 2504, an image receiving portion (not shown), and the like. The present invention can be applied to the display portion 2502.
[0131]
FIG. 10A illustrates a front type projector, which includes a projection device 2601, a screen 2602, and the like. The present invention can be applied to a liquid crystal display device 2808 that constitutes a part of the projection device 2601.
[0132]
FIG. 10B illustrates a rear projector, which includes a main body 2701, a projection device 2702, a mirror 2703, a screen 2704, and the like. The present invention can be applied to a liquid crystal display device 2808 that constitutes a part of the projection device 2702.
[0133]
FIG. 10C is a diagram showing an example of the structure of the projection devices 2601 and 2702 in FIGS. 10A and 10B. The projection devices 2601 and 2702 include a light source optical system 2801, mirrors 2802, 2804 to 2806, a dichroic mirror 2803, a prism 2807, a liquid crystal display device 2808, a phase difference plate 2809, and a projection optical system 2810. Projection optical system 2810 includes an optical system including a projection lens. Although the present embodiment shows a three-plate type example, it is not particularly limited, and for example, a single-plate type may be used. Further, the practitioner may appropriately provide an optical system such as an optical lens, a film having a polarization function, a film for adjusting a phase difference, or an IR film in the optical path indicated by an arrow in FIG. Good.
[0134]
FIG. 10D is a diagram showing an example of the structure of the light source optical system 2801 in FIG. In this embodiment, the light source optical system 2801 includes a reflector 2811, a light source 2812, lens arrays 2813 and 2814, a polarization conversion element 2815, and a condenser lens 2816. Note that the light source optical system illustrated in FIG. 10D is an example and is not particularly limited. For example, the practitioner may appropriately provide an optical system such as an optical lens, a film having a polarization function, a film for adjusting a phase difference, or an IR film in the light source optical system.
[0135]
However, the projector shown in FIG. 10 shows a case where a transmissive electro-optical device is used, and an application example in a reflective electro-optical device is not shown.
[0136]
FIG. 11A illustrates a mobile phone, which includes a main body 2901, an audio output portion 2902, an audio input portion 2903, a display portion 2904, operation switches 2905, an antenna 2906, and the like. The present invention can be applied to the display portion 2904.
[0137]
FIG. 11B illustrates a portable book (electronic book), which includes a main body 3001, display portions 3002 and 3003, a storage medium 3004, operation switches 3005, an antenna 3006, and the like. The present invention can be applied to the display portions 3002 and 3003.
[0138]
FIG. 11C illustrates a display, which includes a main body 3101, a support base 3102, a display portion 3103, and the like. The present invention can be applied to the display portion 3103.
[0139]
As described above, the application range of the present invention is extremely wide and can be applied to electronic devices in various fields. Moreover, the electronic device of a present Example is realizable even if it uses the structure which consists of what combination of Examples 1-3.
[0140]
As described above, the application range of the present invention is extremely wide and can be applied to electronic devices in various fields. By using the present invention, it is possible to obtain a favorable display state in which moving image blur and display flicker are suppressed.
[0141]
Example 5
In this example, the liquid crystal display panel mono-stabilized by Examples 1 to 3 shows the state of liquid crystal alignment with respect to the first voltage.
FIG. 17 shows a surface photograph (the number of pixels is 42 × 31, and the total number of pixels is 320 × 240) when the liquid crystal panel is observed with an optical microscope when the first voltage is changed. These liquid crystal panels are set at a monostabilization treatment start temperature of 75.0 ° C., maintained in this state for 180 seconds, and then started cooling at a cooling rate of −1.2 ° C./min. A first voltage was applied to R2402. Note that in the liquid crystal panels of FIGS. 17A, 17B, and 17C, the first applied voltages were set to +1 V, +2 V, and +5 V, respectively. Thereafter, a DC voltage of −6 V, which is the second voltage, was applied at 66.5 ° C., which is 0.7 ° C. higher than the temperature at which the chiral nematic phase-chiral smectic C phase transition was initiated, to cause phase transition. Then, after transitioning to the chiral smectic C phase, cooling was performed while applying a DC voltage having a constant magnitude to 61.0 ° C., and then the DC voltage was gradually removed.
[0142]
In FIG. 17, white stripes are poorly aligned parts. It can be seen that as the absolute value of the first voltage approaches the absolute value of the second voltage, white stripes indicating poor alignment decrease.
[0143]
Next, FIG. 18 will be described. FIG. 18 shows the number of pixels with poor alignment of the liquid crystal panel shown in FIGS. 17 (A) to 17 (C). From FIG. 17, the closer the absolute value of the first voltage is to the absolute value of the second voltage, that is, the closer the difference between the absolute values of the first voltage and the second voltage is to 0, the alignment of the liquid crystal. It can be seen that defects are decreasing. From this, by performing the monostabilization of the present invention, it is possible to reduce liquid crystal alignment defects derived from charges accumulated at the interface due to the presence of impurity ions or the like in the conventional monostabilization. Preferably, the alignment defect can be further reduced by making the absolute value of the first voltage equal to the absolute value of the second voltage. As described above, by applying the liquid crystal display device manufactured according to the first to third embodiments to the electronic device according to the fourth embodiment, an electronic device having a good display state with reduced moving image blur and display flicker is obtained. be able to.
【The invention's effect】
In the present invention, the DC voltage applied at least immediately before the start of the phase transition of the chiral smectic C phase at the time of cooling during monostabilization is applied to the polarity of the DC voltage applied immediately before the phase transition to the chiral smectic C phase starts. By making it different from the above, it is possible to manufacture a liquid crystal display device that realizes good orientation.
[Brief description of the drawings]
FIG. 1 is a diagram showing a method of monostabilization processing.
FIG. 2 is a diagram showing a method of mono-stabilization processing.
FIG. 3 is a diagram showing a method of mono-stabilization processing.
4A and 4B are diagrams illustrating a manufacturing process of an AM-LCD.
FIGS. 5A and 5B are diagrams illustrating a manufacturing process of an AM-LCD. FIGS.
6A and 6B are diagrams illustrating a manufacturing process of an AM-LCD.
FIG. 7 is a cross-sectional structure diagram of an active matrix liquid crystal display device.
FIG. 8 is a diagram showing an external appearance of an AM-LCD.
FIG 9 illustrates an example of an electronic device.
FIG 10 illustrates an example of an electronic device.
FIG 11 illustrates an example of an electronic device.
FIG. 12 is a diagram illustrating ferroelectric liquid crystal and bistability.
FIG. 13 is a diagram showing the phase sequence of CDR-FLC and the orientation of liquid crystal molecules.
FIG. 14 is a diagram showing a method of mono-stabilization processing (conventional example).
FIG. 15 shows a monostable potential.
FIG. 16 is a graph showing voltage-transmittance characteristics of a HALF-V shape.
FIG. 17 shows a display photograph of a liquid crystal panel manufactured according to the present invention.
FIG. 18 is a diagram showing the number of alignment defects of a liquid crystal panel manufactured according to the present invention.

Claims (11)

After injecting the liquid crystal, a manufacturing method of a liquid crystal display device comprising the step of single-stabilize alignment of the liquid crystal by applying a voltage twice to the liquid crystal,
Cooling while applying a first voltage at a temperature higher than the temperature at which the chiral nematic phase-chiral smectic phase transition is initiated ,
Subsequently, a second voltage having a polarity different from that of the first voltage is applied at a temperature higher than a temperature at which the phase transition starts .
Cooling to a temperature exhibiting a chiral smectic phase while applying the second voltage ;
A method for manufacturing a liquid crystal display device, wherein the second voltage is gradually removed after the phase transition to the chiral smectic phase is completed . After injecting the liquid crystal, a manufacturing method of a liquid crystal display device comprising the step of single-stabilize alignment of the liquid crystal by applying a voltage twice to the liquid crystal,
Cooling while applying a first voltage at a temperature higher than the temperature at which the chiral nematic phase-chiral smectic C phase transition is initiated ,
Subsequently, a second voltage having a polarity different from that of the first voltage is applied at a temperature higher than a temperature at which the phase transition starts .
Cooling to a temperature exhibiting chiral smectic C phase while applying the second voltage ;
A method for manufacturing a liquid crystal display device, wherein the second voltage is gradually removed after the phase transition to the chiral smectic C phase is completed . A method for producing a liquid crystal display device comprising a step of applying voltage twice to a liquid crystal whose phase series is isotropic phase-chiral nematic phase-chiral smectic C phase from a high temperature side to monostabilize the alignment of the liquid crystal ,
Cooling while applying a first voltage at a temperature higher than the temperature at which the chiral nematic phase-chiral smectic C phase transition is initiated ,
Subsequently, a second voltage having a polarity different from that of the first voltage is applied at a temperature higher than a temperature at which the phase transition starts .
Cooling to a temperature exhibiting chiral smectic C phase while applying the second voltage ;
A method for manufacturing a liquid crystal display device, wherein the second voltage is gradually removed after the phase transition to the chiral smectic C phase is completed . After injecting the liquid crystal, a manufacturing method of a liquid crystal display device comprising the step of single-stabilize alignment of the liquid crystal by applying a voltage twice to the liquid crystal,
Starting to cool the liquid crystal while applying a first voltage at a temperature exhibiting an isotropic or chiral nematic phase;
Chiral nematic phases - a second voltage having a polarity different from the previous SL first voltage at a temperature higher than the temperature for starting the chiral smectic phase transition is applied,
It cooled to a temperature showing a chiral smectic phase,
A method for manufacturing a liquid crystal display device, wherein the second voltage is gradually removed after the phase transition to the chiral smectic phase is completed . After injecting the liquid crystal, a manufacturing method of a liquid crystal display device comprising the step of single-stabilize alignment of the liquid crystal by applying a voltage twice to the liquid crystal,
Starting to cool the liquid crystal while applying a first voltage at a temperature exhibiting an isotropic or chiral nematic phase;
Chiral nematic phases - a second voltage having a polarity different from the previous SL first voltage at a temperature higher than the temperature for starting the chiral smectic C phase transition applied,
Cool to a temperature showing the chiral smectic C phase ,
A method for manufacturing a liquid crystal display device, wherein the second voltage is gradually removed after the phase transition to the chiral smectic C phase is completed . A method for producing a liquid crystal display device comprising a step of applying voltage twice to a liquid crystal whose phase series is isotropic phase-chiral nematic phase-chiral smectic C phase from the high temperature side to monostabilize the alignment of the liquid crystal ,
Starting to cool the liquid crystal while applying a first voltage at a temperature exhibiting an isotropic or chiral nematic phase;
Chiral nematic phases - a second voltage having a polarity different from the previous SL first voltage at a temperature higher than the temperature for starting the chiral smectic C phase transition applied,
Cool to a temperature showing the chiral smectic C phase ,
A method for manufacturing a liquid crystal display device, wherein the second voltage is gradually removed after the phase transition to the chiral smectic C phase is completed .   The method for manufacturing a liquid crystal display device according to claim 1, wherein the first voltage and the second voltage are DC voltages.   8. The absolute value of the first voltage and the second voltage is a voltage value that is 50% or more of the maximum value of the transmittance in the voltage-transmittance characteristic according to claim 1. A method for manufacturing a liquid crystal display device.   8. The absolute value of the first voltage and the second voltage according to claim 1 is a voltage value that is 90% or more of the maximum value of transmittance in the voltage-transmittance characteristic. A method for manufacturing a liquid crystal display device. In any one of Claims 1 thru | or 9,
The method for manufacturing a liquid crystal display device, wherein an absolute value of the first voltage is equal to an absolute value of the second voltage. In any one of claims 1 to 10, wherein the liquid crystal display device, pixel electrodes arranged in a matrix, and transistors connected to the pixel electrode, which is arranged through the said pixel electrode liquid crystal common An electrode,
A method for manufacturing a liquid crystal display device, wherein the first voltage and the second voltage are applied between the pixel electrode and the common electrode.

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