JP2009216980A - Method of manufacturing liquid crystal device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress variation of a common voltage and to improve a display quality. <P>SOLUTION: A method of manufacturing a liquid crystal device which comprises first and second substrates, first and second electrodes, and a first liquid crystal comprises: a process (S1) of determining a relation between each film-forming condition of third or fourth electrode and the variation of the common voltage of a test cell when a voltage is applied between the third and fourth electrodes, as for the test cell in which a second liquid crystal is interposed between the third substrate and the fourth substrate; a process (S2) of determining the variation of the common voltage of the liquid crystal device when the first and second electrodes are film-formed under the same condition as each other; a process (S3) of determining the film-forming condition of the first and second electrodes, on the basis of the relation between the film-forming conditions of the third and fourth electrodes and the variation of the common voltage of the test cell, and the variation of a common voltage of the liquid crystal device; and a process (S4) of performing the film-formation of the first and second electrodes on the first and second substrates, on the basis of the determined film-forming condition of the first and second electrodes, and manufacturing the liquid crystal device. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a liquid crystal device in which fluctuations in common voltage are suppressed.

  The liquid crystal device is configured by sealing liquid crystal between two substrates such as a glass substrate and a quartz substrate. In such a liquid crystal device, active elements such as thin film transistors (hereinafter referred to as TFTs), for example, are arranged in a matrix on one substrate, and a counter electrode is arranged on the other substrate. An image can be displayed by changing the optical characteristics of the sealed liquid crystal layer according to the image signal.

  That is, an image signal is supplied to pixel electrodes (ITO) arranged in a matrix by TFT elements, and a voltage based on the image signal is applied to the liquid crystal layer between the pixel electrode and the counter electrode to change the state of liquid crystal molecules. Let As a result, the transmittance of the pixel is changed, and light passing through the pixel electrode and the liquid crystal layer is changed according to the image signal to perform image display.

  In order to define the alignment of liquid crystal molecules when no voltage is applied, an alignment film is formed on the surface of one substrate (active matrix substrate (also referred to as an element substrate)) and the other substrate (counter substrate) in contact with the liquid crystal layer. . As the alignment film, an inorganic alignment film formed by being deposited on the target substrate with a predetermined angle corresponding to the pretilt angle may be employed. Such a method for forming an inorganic alignment film is referred to as oblique deposition.

  Polarizing plates are provided on the front surface and the back surface of the liquid crystal panel, and only a predetermined polarization component of light entering and exiting is allowed to pass through. When a voltage is applied to the liquid crystal, the state of the liquid crystal changes. By applying a voltage corresponding to the image signal to the liquid crystal, light can be transmitted with a transmittance corresponding to the image signal, and an image can be displayed.

  By the way, in the liquid crystal device, application of a DC voltage to the liquid crystal causes deterioration of the liquid crystal such as decomposition of liquid crystal components, contamination by impurities generated in the liquid crystal cell, and burn-in of a display image. Therefore, in general, a technique for preventing display defects such as burn-in of a display image by performing known inversion driving in which the polarity of the driving voltage of each pixel is inverted for each field in an image signal, for example. is there.

  In the liquid crystal device, as is well known, a drive voltage is applied to the pixel electrode only for a certain period in consideration of the capacitance. However, during a period in which the drive voltage is not applied to the pixel electrode, the voltage held in the pixel gradually decreases due to the influence of coupling capacitance and charge leakage.

  However, the amount of decrease in holding voltage differs between positive polarity driving and negative polarity driving in inversion driving, and a decrease in electrode applied voltage during positive polarity driving is lower than a decrease in electrode applied voltage during negative polarity driving. Also grows. For this reason, a negative or positive charge is likely to be accumulated in the pixel electrode according to the drive polarity. Due to such charge accumulation, the above-described impurity ions (hereinafter referred to as impurity ions) are likely to remain at the interface between the pixel electrode and the counter electrode portion and the liquid crystal.

  In general, a voltage applied to the counter electrode (hereinafter referred to as an optimum common voltage) at a level where the effective values of the positive image signal and the negative image signal coincide with each other so that no DC component is applied to the liquid crystal layer. Set. However, due to the influence of impurity ions, the effective voltage value actually applied to the liquid crystal capacitance differs between positive polarity writing and negative polarity writing, and the substantial common voltage varies with respect to the optimum common voltage. For this reason, a DC component is applied to the liquid crystal capacitor in spite of AC driving, and a burn-in phenomenon occurs, and flickering occurs during positive polarity writing and negative polarity writing. The display quality is significantly reduced.

Therefore, Patent Document 1 discloses a technique for preventing a DC component from being applied to the liquid crystal by changing the composition of the alignment film between the TFT substrate side and the counter substrate side.
JP 2006-267882 A

  However, the technique of Patent Document 1 has a problem that the orientation itself may be affected, and as a result, the display quality may be deteriorated.

  The present invention has been made in view of the above-mentioned problems, and it is possible to apply a direct current component to a liquid crystal by changing the film formation conditions of an ITO film, which is a base material of an alignment film, between a pair of substrates. An object of the present invention is to provide a method of manufacturing a liquid crystal device that can prevent and improve display quality.

  In the method for manufacturing a liquid crystal device according to the present invention, a first liquid crystal is interposed between a first substrate and a second substrate facing the first substrate, and the first liquid crystal device is formed on the first substrate. A method for manufacturing a liquid crystal device that performs display by applying a voltage for driving the first liquid crystal between the second electrode formed on the second substrate and the second electrode formed on the second substrate, Test cells in which a second liquid crystal is interposed between the third substrate and a fourth substrate having the same structure as the third substrate are formed on the third and fourth substrates, respectively. Each film formation condition of the third or fourth electrode having the same shape, and fluctuation of the common voltage of the test cell when a voltage for driving the second liquid crystal is applied between the third and fourth electrodes. And the liquid crystal when the first and second electrodes are formed under the same conditions as each other. Based on the step of determining the variation of the common voltage of the device, the relationship between the film forming conditions of the third and fourth electrodes and the variation of the common voltage of the test cell, and the variation of the common voltage of the liquid crystal device, Based on the step of determining the film formation conditions of the first and second electrodes and the determined film formation conditions of the first and second electrodes, the first and second electrodes are formed on the first and second substrates. And a step of forming the second electrode to manufacture the liquid crystal device.

  According to such a configuration, the common voltage of the test cell varies by changing the film formation conditions of the third and fourth electrodes of the test cell. The relationship between the film forming conditions and the common voltage fluctuation is obtained in advance. Further, the fluctuation of the common voltage when the first and second electrodes are formed under the same film formation conditions for the actual cell is obtained. Then, based on the relationship between the film formation conditions of the test cell and the fluctuation of the common voltage and the fluctuation of the common voltage of the real cell, the first and second of the real cell are canceled so as to cancel the fluctuation of the common voltage of the real cell. The film forming conditions for the electrodes are determined. By forming the first and second electrodes of the real cell based on the determined film formation conditions and manufacturing the real cell, fluctuations in the common voltage of the real cell can be suppressed. Thereby, it is possible to prevent a DC voltage from being applied to the first liquid crystal of the actual cell, and to suppress the occurrence of image sticking and flicker.

  The film formation conditions for the first electrode are determined so that a first film quality is obtained, and the second electrode is formed so that a second film quality different from the first film quality is obtained. The film condition is determined.

  According to such a configuration, the first electrode has a first film quality, and the second electrode has a second film quality different from the first film quality. Thereby, the fluctuation | variation of the common voltage of a real cell is suppressed.

  The first and second electrodes are formed so that at least one film quality of composition, roughness, film thickness, and surface state is different from each other.

  According to such a configuration, since at least one film quality of composition, roughness, film thickness, and surface state is different from each other, fluctuations in the common voltage of the actual cell are suppressed.

  The first electrode may be formed under a first sputtering condition, and the second electrode may be formed under a second sputtering condition different from the first sputtering condition. .

  According to such a configuration, since the first sputtering condition and the second sputtering condition are different, the first and second electrodes are configured to have different film qualities, and the fluctuation of the common voltage of the actual cell is suppressed. Is done.

  The first and second electrodes may be formed by changing the sputtering conditions for either temperature or oxygen partial pressure.

  According to such a configuration, since either one of the sputtering conditions of temperature and oxygen partial pressure is different from each other, the first and second electrodes are configured to have different film qualities, and fluctuations in the common voltage of the actual cell Is suppressed.

  The first electrode is subjected to surface treatment under a first treatment condition after film formation, and the second electrode is subjected to surface treatment under a second treatment condition different from the first treatment condition after film formation. It is processed.

  According to such a configuration, the first and second electrodes after film formation are subjected to surface treatment according to the first or second processing condition having different processing conditions, so the first and second electrodes Are configured to have different film qualities, and fluctuations in the common voltage of the actual cell are suppressed.

  In addition, the first and second electrodes are formed by changing the surface treatment of either one of the heat treatment and the plasma treatment after the film formation.

  According to such a configuration, the first and second electrodes have different film qualities because the surface treatment of either the heat treatment or the plasma treatment after the film formation is different from each other. The variation of the common voltage of the actual cell is suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
In this embodiment, a light transmission type liquid crystal device will be described as an example of the liquid crystal device.

  FIG. 1 is a flowchart showing a method for manufacturing a liquid crystal device according to an embodiment of the present invention. FIG. 2 is a flowchart specifically showing the procedure of step S1 in FIG. FIG. 3 is a plan view showing the entire configuration of the liquid crystal device manufactured by the manufacturing method shown in FIG. 4 is a cross-sectional view taken along line H-H ′ in FIG. 3. In each drawing, the scale is different for each layer and each member in order to make each layer and each member recognizable on the drawing.

  3 and 4, the liquid crystal device 100 includes a liquid crystal 50 sandwiched between a TFT substrate 10 made of glass, quartz, or the like and a counter substrate 20, and changes the alignment state of the liquid crystal 50, thereby displaying an image. By modulating the light incident on the region 10a from the counter substrate 20 side and emitting from the TFT substrate 10 side, an image is displayed in the image display region 10a.

  In the liquid crystal device 100, the TFT substrate 10 and the counter substrate 20 are disposed to face each other. The TFT substrate 10 and the counter substrate 20 are bonded to each other by a seal material 52 provided in a seal region located around the image display region 10a, and the TFT substrate 10 and the counter substrate 20 are bonded by the seal material 52. Liquid crystal 50 is sealed between them. Further, in the sealing material 52, a gap material such as a glass fiber or a glass bead (not shown) is provided for setting the distance between the TFT substrate 10 and the counter substrate 20 to a predetermined value.

  A light-shielding frame light-shielding film 53 that defines the frame area of the image display area 10a is provided on the counter substrate 20 side in parallel with the inside of the seal area where the sealing material 52 is disposed. A part or all of the frame light shielding film 53 may be provided as a built-in light shielding film on the TFT substrate 10 side.

  The periphery of the image display area 10a is a non-display area. In the non-display area, the data line driving circuit 101 and the mounting terminal 102 are provided along one side of the TFT substrate 10 in an area located outside the seal area where the seal material 52 is disposed. Although not shown, by connecting a flexible printed circuit board or the like to the mounting terminals 102 exposed on the surface of the TFT substrate 10, electrical connection between the liquid crystal device 100 and the outside such as a control device of an electronic device is performed. Is called.

  The scanning line driving circuit 104 is provided along two sides adjacent to one side of the TFT substrate 10 on which the data line driving circuit 101 and the mounting terminals 102 are provided, and is covered with the frame light shielding film 53. Further, a plurality of wirings 105 are covered by the frame light shielding film 53 along the remaining side of the TFT substrate 10, that is, the side facing the one side of the TFT substrate 10 on which the data line driving circuit 101 and the mounting terminal 102 are provided. Provided. The two scanning line driving circuits 104 are electrically connected to each other by the plurality of wirings 105.

  In addition, at least one corner of the counter substrate 20 is provided with a vertical conductive material 106 that electrically connects the TFT substrate 10 and the counter substrate 20. On the other hand, the TFT substrate 10 is provided with vertical conduction terminals in a region corresponding to the vertical conduction material 106. Electrical connection is made between the TFT substrate 10 and the counter substrate 20 via the vertical conductive member 106 and the vertical conductive terminal.

  In FIG. 4, an inorganic alignment film 16 is formed on the TFT substrate 10 on the pixel electrode 9a after the formation of pixel switching TFTs, scanning lines, data lines, and the like. On the other hand, on the counter substrate 20, in addition to the counter electrode 21, a light shielding film 23 having a lattice shape or a stripe shape is formed, and an inorganic alignment film 22 is formed on the uppermost layer portion. The inorganic alignment films 16 and 22 formed on the surfaces of the TFT substrate 10 and the counter substrate 20 that are in contact with the liquid crystal 50 are thin films made of an inorganic material such as SiO 2, SiO, or MgF 2.

  Thin films made of these inorganic materials are formed by vapor deposition. The liquid crystal 50 is, for example, a mixture of one kind or several kinds of liquid crystals, and takes a predetermined alignment state between the pair of inorganic alignment films 16 and 22.

  Further, for example, a TN (twisted nematic) mode, an STN (super TN) mode, and a D-STN (double-STN) are respectively provided on the side on which the incident light of the counter substrate 20 enters and the side on which the outgoing light of the TFT substrate 10 exits. ) Mode, VA (vertical alignment) mode, and other modes, and a normally white mode / normally black mode, a polarizing film, a retardation film, a polarizing plate, and the like are arranged in a predetermined direction.

  Thus, in the liquid crystal device 100, the alignment film for regulating the alignment of liquid crystal molecules is formed of an inorganic alignment film that is a thin film made of an inorganic material such as SiO2, SiO, or MgF2. An inorganic alignment film composed of an inorganic material is superior in light resistance and heat resistance to an alignment film composed of an organic material such as polyimide, so that a liquid crystal device that does not deteriorate over time and does not deteriorate display quality is used. realizable.

  Note that, in this embodiment mode, an example in which the alignment film is formed using an inorganic material has been described, but the alignment film may be formed using an organic material.

  Further, in the display area 10a of the TFT substrate 10, a plurality of scanning lines (not shown) and a plurality of data lines (not shown) are arranged so as to intersect with each other, and a pixel electrode is formed in an area partitioned by the scanning lines and the data lines. 9a are arranged in a matrix. A thin film transistor (TFT) (not shown) is provided corresponding to each intersection of the scanning line and the data line, and the pixel electrode 9a is electrically connected to each TFT.

  The TFT is turned on by an ON signal supplied from the scanning line driving circuit 104 to the scanning line, whereby an image signal supplied from the data line driving circuit 101 to the data line is supplied to the pixel electrode 9a. Thus, the drive voltage is applied to the liquid crystal 50 between the pixel electrode 9a and the counter electrode 21.

  Next, a method for manufacturing a liquid crystal device will be described with reference to FIGS. FIG. 5 shows a specific procedure of step S4 of FIG.

  First, a manufacturing method of a liquid crystal device (hereinafter also referred to as an actual cell) that is actually used will be described with reference to FIG.

  In step S <b> 11 of FIG. 5, a stacked structure is formed on the TFT substrate 10. For example, data lines, scanning lines, TFTs, and the like are formed by film formation by CVD or sputtering, patterning by photolithography, heat treatment, or the like. Next, in step S12, an interlayer insulating film is formed on the formed laminated structure, and then a pixel electrode 9a is formed using an ITO film.

  On the other hand, in step S <b> 21, a stacked structure is formed on the counter substrate 20. For example, the light shielding film 23 is formed by film formation by CVD or sputtering, patterning by photolithography, or the like. Next, in step S21, the counter electrode 21 is formed on the formed laminated structure with an ITO film.

  Next, for the TFT substrate 10, for example, a SiO 2 material is deposited on the pixel electrode 9 a of the TFT substrate 10 in the inorganic alignment film forming step, and the inorganic alignment film 16 is formed by patterning (step S 13). Next, in the cleaning process, a cleaning liquid is supplied onto the surface of the inorganic alignment film 16 formed on the TFT substrate 10 to clean the surface of the inorganic alignment film 16 (step S14).

  On the other hand, an inorganic alignment film 22 made of SiO 2 is formed on the counter electrode 21 by vapor deposition on the counter substrate 20 (step S23). Thereby, the inorganic alignment film 22 having the same structure as the inorganic alignment film 16 is formed. Next, a cleaning liquid is supplied onto the surface of the inorganic alignment film 22 to clean the surface of the inorganic alignment film 22 (step S23).

  Then, after the pre-process of the TFT substrate 10 and the counter substrate 20 is completed, in the bonding process, the TFT substrate 10 and the counter substrate 20 are bonded to each other with a predetermined alignment adjusted via the seal material 52 (step S31). ). Next, in the liquid crystal injection process, the liquid crystal 50 is injected and sealed in the region formed by the TFT substrate 10 and the counter substrate 20 bonded through the sealing material 52, and the liquid crystal device 100 is completed (step S32). .

  In the present embodiment, the ITO films formed in step S12 and step S22 are formed under different film forming conditions. For example, the pixel electrode 9a and the counter electrode 21 can be formed by sputtering. In this case, the pixel electrode 9a is formed under the first sputtering condition, and the counter electrode 21 is formed under the second sputtering condition different from the first sputtering condition.

  Due to the difference in film forming conditions, the film quality of the ITO film of the pixel electrode 9a and the counter electrode 21, for example, composition, roughness, film thickness, surface state, and the like are different from each other. As a result, it is possible to prevent the DC component from being applied to the liquid crystal by suppressing the fluctuation of the common voltage.

  When an ITO film is formed by sputtering, it is necessary to define values of parameters such as film thickness, oxygen partial pressure, and heating as film forming conditions. In this embodiment, these values are set to the pixel electrode 9a. It is changed between the formation time and the counter electrode 21 formation time.

  In the present embodiment, in step S1 of FIG. 1, the optimum setting value of such a film forming condition is grasped in advance by a test using a test cell. FIG. 6 is an explanatory diagram showing a test apparatus for obtaining optimum sputtering conditions.

  In order to obtain the sputtering conditions, a test cell 61 is prepared. As the test cell 61, first and second substrates 62 and 63 having the same structure are used. An electrode 64 is formed on the entire surface of the first substrate 62, and an electrode 65 having the same shape as the electrode 64 is also formed on the entire surface of the second substrate 62. Film formation conditions are appropriately set for the electrodes 64 and 65. For example, the electrode 64 is formed by sputtering an ITO film on the entire surface of the first substrate 62 under a first sputtering condition, and the electrode 65 is formed on the entire surface of the second substrate 63 under a second sputtering condition. It is formed by sputtering an ITO film.

  Alignment films 66 and 67 are formed on the entire surfaces of the electrodes 64 and 65, respectively. The first and second substrates 62 and 63 thus formed with the laminated structure are bonded together with a sealant 69, and the liquid crystal 68 is sealed.

  If the first sputtering condition and the second sputtering condition are the same, and the film quality of the ITO film constituting the electrodes 64 and 65 is the same, the interface between the alignment film 66 and the liquid crystal 68 is the same. The amount of attached ions and the amount of ions attached to the interface between the alignment film 67 and the liquid crystal 68 are the same. Accordingly, the common voltage between the electrodes 64 and 65 when the test cell 61 is driven in an inversion manner matches the optimum common voltage, and the fluctuation amount is 0V.

  When the first sputtering condition and the second sputtering condition are different, the film quality of the ITO films constituting the electrodes 64 and 65 differ from each other according to the conditions. As a result, the common voltage between the electrodes 64 and 65 when the test cell 61 is driven in an inverted manner deviates from the optimum common voltage. That is, it is considered that the common voltage can be changed to an appropriate value by appropriately setting the sputtering conditions for the electrodes 64 and 65.

  Table 1 below shows changes in the surface roughness characteristics when the temperature is changed as the sputtering conditions when forming the electrodes 64 and 65. Table 1 below shows characteristics when an inorganic alignment film is employed as the alignment film.

[Table 1]
Deposition temperature Surface roughness Ra
Room temperature 1.870E + 00 [nm]
400 ° C 2.210E + 00 [nm]
Of the film quality of the electrodes 64 and 65, the surface roughness Ra [nm] varies depending on the temperature condition among the sputtering conditions. That is, Table 1 shows that 1.870E + 00 [nm] was obtained as the surface roughness Ra when the sputtering process was performed at room temperature when the electrodes 64 and 65 were formed. Table 1 shows that when the electrodes 64 and 65 were formed by sputtering, the surface roughness Ra was 2.210E + 00 [nm] when the sputtering process was performed at a temperature of 400 ° C. ing.

  Thus, the electrodes 64 and 65 having different surface roughness Ra can be formed by changing the temperature conditions at the time of film formation of the electrodes 64 and 65.

  If both the electrodes 64 and 65 of the first and second substrates 62 and 63 of the test cell of FIG. 6 are formed at room temperature, the deviation of the common voltage is 0V. This is the case where the film thickness of the electrodes 64 and 65 to be formed is uniform, for example, about 150 nm.

  On the other hand, when the first substrate 62 is sputtered at room temperature and the second substrate 63 is sputtered at 400 ° C. to form the test cell of FIG. It was found that the voltage increased by + 0.2V.

  In step S5 of FIG. 2, film formation conditions for the electrodes 64 and 65 of the test cell 61 are set, and the test cell 61 is configured according to the film formation conditions (step S6). And the fluctuation | variation of a common voltage is measured by the measurement part 70 (step S7). Thereafter, new test cells are sequentially formed while changing the film forming conditions, and the fluctuation of the common voltage is obtained. In this way, the relationship between the film formation conditions of the test cell and the fluctuation of the common voltage can be obtained.

  On the other hand, for the actual cell, the fluctuation of the common voltage is obtained when the ITO film forming conditions are set to be the same for the TFT substrate 10 and the counter substrate 20 (step S2).

  In the actual liquid crystal device 100, the common voltage shifts from the optimum common voltage to the positive side or shifts to the negative side as described above due to the difference in structure between the TFT substrate 10 and the counter substrate 20. The variation amount of the common voltage is determined by the structure of the liquid crystal device 100, and it is considered that the common voltage varies similarly for the liquid crystal device 100 having the same structure. Therefore, the fluctuations in the common voltage of the liquid crystal device manufactured with the same sputtering conditions for the pixel electrode 9a and the counter electrode 21 are obtained, and the first and second sputtering conditions are set so as to cancel the fluctuations in the common voltage. That's fine.

  For example, in the case where a common voltage shifts by −0.2 V in a liquid crystal device manufactured by using the same sputtering conditions for the pixel electrode 9a and the counter electrode 21, as shown in Table 1, the pixel electrode 9a is sputtered at room temperature. By processing and forming the counter electrode 21 by sputtering at 400 ° C., fluctuations in the common voltage can be suppressed.

  In step S3, film formation conditions (step S12 described above) for canceling the fluctuation of the common voltage of the real cell based on the amount of fluctuation of the common voltage of the real cell obtained in step S2 and the measurement result of step S1. , S22, the first and second sputtering conditions) are set. In step S4, as described above, the first sputtering condition and the second sputtering condition are applied to form an ITO film, and the pixel electrode 9a and the counter electrode 21 are formed. As a result, a liquid crystal device in which fluctuation of the common voltage is suppressed can be manufactured.

  In addition to the heating conditions shown in Table 1, it is conceivable to change the film thickness and oxygen partial pressure conditions as film formation conditions. For example, when the electrodes 64 and 65 are formed thick, the common voltage can be shifted to the positive side.

  As described above, in the present embodiment, by setting the film quality of the ITO film, which is the base material of the alignment film, to different film qualities on the TFT substrate side and the counter substrate side, the variation in the common voltage is offset, and the liquid crystal It is possible to prevent a DC component from being applied to the. As a result, it is possible to improve the display quality by preventing the occurrence of image sticking and flicker.

(Second Embodiment)
FIG. 7 is a flowchart showing the second embodiment of the present invention.

  In the first embodiment, the film quality of the ITO film is different between the first substrate and the second substrate by changing the conditions at the time of forming the ITO film. On the other hand, in the present embodiment, after the ITO film is formed, surface treatment for film quality modification is performed, so that the film quality of the ITO film differs between the first substrate and the second substrate. This is an example.

  FIG. 7 differs from the first embodiment in that steps S42 and S43 are employed instead of step S12 in FIG. 5, and steps S52 and S53 are employed instead of step S22. . The processing in steps S42 and S52 is a normal ITO film forming process, in which an ITO film is formed on the TFT substrate 10 and the counter substrate 20 under the same sputtering conditions.

  In step S43, a surface treatment is performed on the deposited ITO film under the first treatment condition. In step S53, a second treatment different from the first treatment condition is performed on the deposited ITO film. Surface treatment is performed under conditions. By performing the surface treatment on the TFT substrate 10 and the counter substrate 20 under different processing conditions, the film quality of the ITO film of the pixel electrode 9a and the counter electrode 21 to be formed can be made different from each other. As a result, it is possible to prevent the DC component from being applied to the liquid crystal by suppressing the fluctuation of the common voltage.

  Examples of the surface treatment include heat treatment, UV irradiation treatment, and plasma treatment. In the present embodiment, these processing conditions are changed when the pixel electrode 9a is formed and when the counter electrode 21 is formed. These processing conditions can also be grasped in advance by a test using the test cell of FIG.

  Table 2 below shows changes in wettability and the work function of the ITO film surface with or without the plasma treatment when O2 plasma treatment is adopted as the surface treatment after the electrodes 64 and 65 are formed. Table 2 below shows characteristics when an inorganic alignment film is employed as the alignment film.

[Table 2]
Execution of plasma treatment Wettability Work function Available 32 ° 5.3 eV
None 85 ° 4.8 eV
Of the film quality of the electrodes 64 and 65, the wettability and the work function of the surface vary depending on the presence or absence of the plasma treatment. In Table 2, when the plasma treatment was performed after the electrodes 64 and 65 were formed, the electrodes 64 and 65 having a wettability of 32 ° and a work function of the surface of the electrodes 64 and 65 of 5.3 eV were obtained. It is shown that. Further, it is shown that when the plasma treatment is not performed after the electrodes 64 and 65 are formed, the electrodes 64 and 65 having a wettability of 85 ° and a work function of 4.8 eV are obtained.

  As described above, the electrodes 64 and 65 having different wettability and work function can be formed by changing the surface treatment conditions after the electrodes 64 and 65 are formed.

  If the same O 2 plasma treatment was performed on both the electrodes 64 and 65 of the test cell of FIG. 6, the common voltage deviation was 0V. On the other hand, when the plasma processing of Table 2 was applied only to the first substrate 62 to form the test cell of FIG. 6, the common voltage changed by −0.2 V as a result of the measurement in the measurement unit 70. I understood.

  Accordingly, when the common voltage is shifted by 0.2 V to the positive side in a liquid crystal device manufactured with the same sputtering conditions for the pixel electrode 9a and the counter electrode 21, plasma processing is not performed after the pixel electrode 9a is formed. By performing the O 2 plasma treatment after the counter electrode 21 is formed, fluctuations in the common voltage can be suppressed.

  Note that the film quality can be changed not only by the O 2 plasma treatment but also by heat treatment using an oven or UV.

  As described above, also in this embodiment, by setting the film quality of the ITO film, which is the base material of the alignment film, to different film qualities on the TFT substrate side and the counter substrate side, the fluctuation of the common voltage is offset, and the liquid crystal It is possible to prevent a DC component from being applied to the. As a result, it is possible to improve the display quality by preventing the occurrence of image sticking and flicker.

  In each of the above embodiments, examples of forming an inorganic alignment film have been described. However, even when an organic alignment film is formed, fluctuations in common voltage are suppressed according to the film quality of the ITO film that is the base material. Has the effect of

  Further, the liquid crystal device is not limited to the above-described illustrated examples, and it is needless to say that various changes can be made without departing from the gist of the present invention. For example, the above-described liquid crystal device has been described by taking an active matrix type liquid crystal display module using an active element (active element) such as a TFT (thin film transistor) as an example. An active matrix type liquid crystal display module using the active element (active element) may be used.

  Further, the liquid crystal device may be a display device for forming an element on a semiconductor substrate, for example, LCOS (Liquid Crystal On Silicon). In LCOS, a single crystal silicon substrate is used as an element substrate, and a transistor is formed on a single crystal silicon substrate as a switching element used for a pixel or a peripheral circuit. In addition, a reflective pixel electrode is used for the pixel, and each element of the pixel is formed below the pixel electrode.

5 is a flowchart showing a method for manufacturing a liquid crystal device according to an embodiment of the present invention. The flowchart which shows the procedure of step S1 in FIG. 1 concretely. The top view which shows the whole structure of the liquid crystal device manufactured by the manufacturing method shown in FIG. Sectional drawing cut | disconnected and shown along the H-H 'line | wire in FIG. The flowchart which shows the specific procedure of step S4 of FIG. Explanatory drawing which shows the test apparatus for calculating | requiring optimal sputtering conditions. The flowchart which shows the 2nd Embodiment of this invention.

Explanation of symbols

    S1... Step for obtaining the relationship between the film formation conditions and the variation of the common voltage, S2... Steps for obtaining the variation of the common cell common voltage, S3. Film process, S11, S21 ... Stack structure forming process, S12 ... ITO film forming process under first sputtering conditions, S13, S23 ... Alignment film forming process, S22 ... ITO film forming process under second sputtering conditions.

Claims (7)

A first liquid crystal is interposed between a first substrate and a second substrate facing the first substrate, and formed on the first substrate and the second substrate formed on the first substrate. A method of manufacturing a liquid crystal device for performing display by applying a voltage for driving the first liquid crystal between the second electrode,
For the test cell in which the second liquid crystal is interposed between the third substrate and the fourth substrate opposite to the third substrate and having the same structure as the third substrate, the third and fourth substrates Each of the film-forming conditions of the third or fourth electrode having the same shape and the voltage for driving the second liquid crystal is applied between the third and fourth electrodes. A process for obtaining a relationship between fluctuations in common voltage,
Obtaining fluctuations in the common voltage of the liquid crystal device when the first and second electrodes are formed under the same conditions as each other;
Based on the relationship between the film formation conditions of the third and fourth electrodes and the variation of the common voltage of the test cell, and the variation of the common voltage of the liquid crystal device, the film formation of the first and second electrodes is performed. Determining the conditions;
Forming the first and second electrodes on the first and second substrates based on the determined deposition conditions of the first and second electrodes, and manufacturing the liquid crystal device; A method for manufacturing a liquid crystal device, comprising: The first electrode has film formation conditions determined so as to obtain a first film quality,
2. The method of manufacturing a liquid crystal device according to claim 1, wherein film formation conditions for the second electrode are determined so that a second film quality different from the first film quality is obtained.   3. The method of manufacturing a liquid crystal device according to claim 2, wherein the first and second electrodes are formed such that at least one film quality of composition, roughness, film thickness, and surface state is different from each other. . The first electrode is formed by a first sputtering condition,
The method of manufacturing a liquid crystal device according to claim 1, wherein the second electrode is formed under a second sputtering condition different from the first sputtering condition.   5. The method of manufacturing a liquid crystal device according to claim 4, wherein the first and second electrodes are formed under different sputtering conditions of one of temperature and oxygen partial pressure. The first electrode is subjected to a surface treatment according to a first treatment condition after film formation,
2. The method of manufacturing a liquid crystal device according to claim 1, wherein the second electrode is subjected to a surface treatment after film formation under a second processing condition different from the first processing condition.   7. The liquid crystal device according to claim 6, wherein the first and second electrodes are formed by differentiating surface treatment of any one of heat treatment and plasma treatment after film formation. Production method.

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