JP3815194B2 - Liquid crystal device manufacturing apparatus, liquid crystal device manufacturing method, and liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To align a substrate having high accuracy to obtain an accurate rubbing angle and to suppress fluctuations in the contrast. SOLUTION: A substrate 90, preliminarily aligned on a prealignment stage, is mounted on a bed 105 of an alignment unit 101. Alignment mark is formed at a specified position of the substrate 90, and the gravity center of the alignment marks is detected by the image recognition process by CCDs 106, 107. The result of the detection of the gravity center by the CCDs is sent to a driving control part, which drives the bed 105 so as to position the gravity center at a specified position. The substrate 90 thus accurately aligned is rubbed by a roller 108.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for manufacturing a liquid crystal device, a method for manufacturing the same, and a liquid crystal device that reduce variations in rubbing angles with respect to a substrate.
[0002]
[Prior art]
A liquid crystal device such as a liquid crystal light valve is configured by sealing liquid crystal between two substrates such as a glass substrate and a quartz substrate. In a liquid crystal light valve, switching 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 and sealed between the two substrates. By changing the optical characteristics of the stopped liquid crystal layer according to the image signal, it is possible to display an image.
[0003]
A liquid crystal panel used for a projector uses a TN (twisted nematic) liquid crystal having a high transmittance and a high contrast ratio. As a driving device, a high-temperature polysilicon TFT having a high light leakage characteristic and capable of high-definition display is mainly used.
[0004]
The characteristics of such a liquid crystal panel are greatly influenced by Δn (refractive index anisotropy), and the threshold voltage of the liquid crystal is substantially determined by the cell gap, Δε (dielectric anisotropy), and the elastic constant of the liquid crystal. . Generally, the contrast of normally white TN liquid crystal becomes better as the voltage application amount is higher.
[0005]
However, the effective voltage applied to the liquid crystal is about 4.0 V due to the breakdown voltage of the element or the limitation of the signal voltage of the supply circuit. The contrast of normally white TFT liquid crystal becomes better as the applied voltage is higher, but the voltage is limited to about 4 V in actual use, resulting in insufficient contrast.
[0006]
Further, in the projector, the light distribution is set so as to intensify a component in which light travels at a right angle (normal direction) to the liquid crystal panel. Matching the contrast peak with the peak of such a light distribution is extremely effective for improving the contrast. However, when the voltage application amount is around 4.0 V, the contrast peak deviates from the normal direction. For this reason, when a liquid crystal panel is used for a light valve of a projector, a contrast reduction occurs due to a deviation between the peak of the light distribution and the contrast peak.
[0007]
As a technique for improving the contrast shortage, the present applicant discloses in Japanese Patent Application No. 2000-248525 filed earlier that it is effective to control the twist angle with high accuracy.
[0008]
[Problems to be solved by the invention]
However, it is necessary to control the rubbing angle for determining the twist angle with high accuracy, and when the rubbing angle varies between the substrates, the contrast quality also varies.
By the way, in order to control the rubbing angle with respect to the substrate with high accuracy, it is necessary to accurately arrange the substrate at the reference position of the rubbing stage. However, conventionally, since the reference position of the substrate is determined based on the outer shape of the substrate, there has been a problem that the substrate is not arranged at the reference position with respect to the rubbing stage due to variations in the outer shape of the substrate. Therefore, the substrate cannot be rubbed at a predetermined rubbing angle, and when a pair of substrates are bonded together, a desired rubbing angle varies between the substrates. Further, the rubbing angle also varies due to variations in conveyance of the rubbing apparatus.
[0009]
In particular, when a round substrate is used as the substrate, the placement accuracy at the reference position is lowered and the angular deviation is significant. Normally, alignment of a round substrate is performed by using a position mark (notch) as an outer shape reference and performing parallel adjustment by an optical method. However, the accuracy of the notch is relatively low, and scattered light is generated due to the chamfering of the substrate, which reduces the accuracy of optical position adjustment.
[0010]
Thus, conventionally, since the alignment accuracy of the substrate is low, there is a problem in that the rubbing angle varies and the contrast characteristics also vary.
[0011]
The present invention has been made in view of such problems, and a liquid crystal that can improve the alignment accuracy of a substrate by forming an alignment mark on the substrate and adjusting the position by using the alignment mark. An object of the present invention is to provide a device manufacturing apparatus, a manufacturing method thereof, and a liquid crystal device.
[0012]
In addition, the present invention improves the alignment accuracy of the substrate by adjusting the position using alignment marks formed on the substrate, thereby reducing the variation in the rubbing angle and the variation in the contrast characteristics. An object of the present invention is to provide a liquid crystal device manufacturing apparatus, a manufacturing method thereof, and a liquid crystal device.
[0013]
[Means for Solving the Problems]
An apparatus for manufacturing a liquid crystal device according to the present invention includes an alignment table on which a liquid crystal substrate is placed so that the liquid crystal substrate can be freely moved and rotated in a horizontal plane, and a liquid crystal placed on the alignment table. Center of gravity detecting means for detecting the center of gravity of the rubbing alignment mark formed on the substrate, and driving the table based on the detection result of the center of gravity detecting means for moving the position of the center of gravity of the rubbing alignment mark to a predetermined position. And an alignment unit comprising an alignment drive control means for performing alignment, and the center of gravity of the rubbing alignment mark is positioned within a predetermined position range so that the liquid crystal substrate is positioned for the alignment. A pre-alignment unit that performs a pre-alignment process on the liquid crystal substrate to be placed on a table. The alignment unit is formed on a pre-alignment base on which a liquid crystal substrate is placed so as to be freely movable and rotatable in a horizontal plane, and a liquid crystal substrate placed on the pre-alignment base. Transmittance detection means for detecting transmittance using an alignment mark, and prealignment drive control for driving the prealignment base and performing prealignment based on the transmittance detection result by the transmittance detection means And means.
[0014]
According to such a configuration, the alignment platform can freely move and rotate in any direction within the horizontal plane. A liquid crystal substrate is placed on the alignment table. A rubbing alignment mark is formed on the liquid crystal substrate, and the center of gravity detecting means detects the center of gravity of the rubbing alignment mark. The drive control means for alignment performs alignment by driving the alignment base based on the detection result of the gravity center detection means in order to move the gravity center position of the rubbing alignment mark to a predetermined position. As a result, the liquid crystal substrate can be aligned with extremely high accuracy.
Further, the liquid crystal substrate can be placed on the table so that the center of gravity of the rubbing alignment mark is located within a predetermined position range by the pre-alignment process. Further, since the liquid crystal substrate is positioned within a predetermined range, the image recognition area can be increased in magnification, and as a result, the resolution of the image processing is improved and the alignment accuracy is improved.
Furthermore, pre-alignment processing can be easily performed, for example, by emitting a laser beam or the like at a predetermined position and detecting the transmittance based on the received light amount received through the alignment mark.
[0015]
As the center of gravity detection means, one that detects the center of gravity of the rubbing alignment mark by image recognition processing can be employed.
[0016]
According to such a configuration, it is possible to perform alignment with higher accuracy than the alignment accuracy based on the outer shape reference by image recognition processing.
[0023]
The apparatus for manufacturing a liquid crystal device according to the present invention further includes a rubbing roller provided on a conveyance path on which a table on which the liquid crystal substrate is placed is conveyed after alignment by the drive control unit, and is placed on the table. And a rubbing unit for rubbing the liquid crystal substrate conveyed.
According to such a configuration, the accurately aligned liquid crystal substrate is conveyed to the rubbing roller side, so that the rubbing angle by the rubbing roller is accurately controlled.
Further, the angle between the liquid crystal device and the rubbing roller is adjusted by the alignment. With this configuration, the rubbing angle of the liquid crystal device can be controlled with high accuracy.
[0024]
According to the present invention, the drive control means rotates the stage on which the liquid crystal substrate is placed according to a specified rubbing angle before the stage is transported to the rubbing unit after the alignment process is completed. It is characterized by that.
[0025]
According to such a configuration, an arbitrary rubbing angle can be obtained with high accuracy.
[0026]
The liquid crystal substrate according to the present invention has a rubbing alignment mark for enabling alignment by detecting the center of gravity on the liquid crystal substrate.
[0027]
According to such a configuration, accurate alignment is possible by detecting the center of gravity using the alignment mark.
[0028]
The alignment mark may be the same as the reflective material formed on the element substrate and formed in the same process.
[0029]
According to such a configuration, the process for forming the alignment mark can be shared with other processes, and an increase in the number of processes can be suppressed.
[0030]
The alignment mark may have a surface covered with a permeable oxide film.
[0031]
According to such a configuration, the alignment mark can be protected by the permeable oxide film.
[0032]
The alignment mark is the same as the reflective material constituting the light shielding film and can be formed in the same process.
[0033]
According to such a configuration, the process for forming the alignment mark can be combined with the process for forming the light shielding film, and an increase in the number of processes can be suppressed.
[0034]
The alignment mark may be one whose surface is covered with a common electrode.
[0035]
According to such a configuration, the alignment mark can be protected by the common electrode.
[0036]
The method for manufacturing a liquid crystal device according to the present invention includes a procedure for placing a liquid crystal substrate on a pre-alignment table that can freely move and rotate in a horizontal plane, A transmittance detection procedure for performing transmittance detection using an alignment mark formed on the placed liquid crystal substrate, and driving the pre-alignment base based on the transmittance detection result in the transmittance detection procedure; A pre-alignment procedure for pre-aligning the liquid crystal substrate so that the center of gravity of the alignment mark for rubbing formed on the liquid crystal substrate is located within a predetermined position range; The procedure of placing on an alignment table that can freely move and rotate in any direction, and the liquid crystal substrate placed on the alignment table A center-of-gravity detection procedure for detecting the center of gravity of the alignment mark for bing; An alignment procedure for aligning the liquid crystal substrate.
[0037]
According to such a configuration, the liquid crystal substrate is placed on a table that can freely move and rotate in an arbitrary direction within a horizontal plane. A rubbing alignment mark is formed on the liquid crystal substrate placed on the table, and the arrangement position of the liquid crystal substrate is detected by detecting the center of gravity of the rubbing alignment mark. Then, in order to move the gravity center position of the rubbing alignment mark to a predetermined position, alignment is performed by driving the table based on the detection result of the gravity center detection.
[0038]
According to such a configuration, the center of gravity is detected by using the rubbing alignment mark formed on the liquid crystal substrate, and the alignment is performed based on the center of gravity detection result, so that high-precision alignment is possible. It is.
Further, the liquid crystal substrate can be placed on the table so that the center of gravity of the rubbing alignment mark is located within a predetermined position range by the pre-alignment process.
[0041]
The manufacturing method of the liquid crystal device is mounted on the alignment table by a rubbing roller provided on a transfer path on which an alignment table on which the liquid crystal substrate is mounted is transferred after the alignment. The liquid crystal substrate may further include a rubbing procedure for performing a rubbing process.
[0042]
According to such a configuration, the accurately aligned liquid crystal substrate is conveyed to the rubbing roller side, so that the rubbing angle by the rubbing roller is accurately controlled.
[0043]
The alignment procedure includes a procedure of rotating a table on which the liquid crystal substrate is placed according to a specified rubbing angle before the rubbing procedure.
[0044]
According to such a configuration, an arbitrary rubbing angle can be obtained with high accuracy.
[0045]
One aspect of the method for manufacturing a liquid crystal device according to the present invention is characterized in that in the alignment procedure, the stage is rotated so that the rubbing angle of the liquid crystal device is 89 ° to 85 °.
According to such a configuration, a liquid crystal device having a twist angle of 91 ° to 95 ° can be manufactured, and the contrast is improved.
The liquid crystal device of the present invention is manufactured by the above manufacturing method. With this configuration, the rubbing angle can be arbitrarily set with high accuracy.
[0046]
As one aspect of the liquid crystal device of the present invention, the liquid crystal device has a twist angle in a range of 91 ° to 95 °.
[0047]
According to such a configuration, contrast can be improved.
[0048]
Further, according to one aspect of the liquid crystal device of the present invention, the liquid crystal substrate has a rubbing angle with respect to the rubbing angle of the element substrate with the rubbing direction of the element substrate orthogonal to the scanning line direction and the rubbing direction of the counter substrate with respect to the rubbing angle of the element substrate. Is in the range of 85 ° to 89 °.
[0049]
According to such a configuration, the influence of the lateral electric field is small and the contrast is good.
[0050]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an apparatus for manufacturing a liquid crystal device according to a first embodiment of the present invention. 2 and 3 are explanatory views showing a round substrate on which a rubbing process is performed by the liquid crystal device manufacturing apparatus of FIG. FIG. 4 is an equivalent circuit diagram of various elements and wirings in a plurality of pixels constituting the pixel region of the liquid crystal device. FIG. 5 is a plan view of an element substrate such as a TFT substrate as viewed from the side of the counter substrate together with each component formed thereon, and FIG. 6 is an assembly process in which the element substrate and the counter substrate are bonded together to enclose liquid crystal. It is sectional drawing which cut | disconnects and shows the liquid crystal device after completion | finish at the position of the HH 'line of FIG. FIG. 7 is a cross-sectional view showing the liquid crystal device in detail. FIG. 8 is a flowchart showing the panel assembly process.
[0051]
First, the structure of the liquid crystal panel will be described with reference to FIGS.
[0052]
As shown in FIGS. 5 and 6, the liquid crystal panel is configured by sealing a liquid crystal 50 between an element substrate 10 such as a TFT substrate and a counter substrate 20. On the element substrate 10, pixel electrodes and the like constituting pixels are arranged in a matrix. FIG. 4 shows an equivalent circuit of elements on the element substrate 10 constituting the pixel.
[0053]
As shown in FIG. 4, in the pixel region, a plurality of scanning lines 3a and a plurality of data lines 6a are wired so as to intersect with each other, and a pixel electrode is formed in a region partitioned by the scanning lines 3a and the data lines 6a. 9a are arranged in a matrix. A TFT 30 is provided corresponding to each intersection of the scanning line 3 a and the data line 6 a, and the pixel electrode 9 a is connected to the TFT 30.
[0054]
The TFT 30 is turned on by the ON signal of the scanning line 3a, whereby the image signal supplied to the data line 6a is supplied to the pixel electrode 9a. A voltage between the pixel electrode 9 a and the counter electrode 21 provided on the counter substrate 20 is applied to the liquid crystal 50. Further, a storage capacitor 70 is provided in parallel with the pixel electrode 9a, and the storage capacitor 70 holds the voltage of the pixel electrode 9a for a time that is, for example, three orders of magnitude longer than the time when the source voltage is applied. The storage capacitor 70 improves retention characteristics and enables image display with a high contrast ratio.
[0055]
FIG. 7 is a schematic cross-sectional view of a liquid crystal panel focusing on one pixel.
[0056]
An element substrate 10 such as glass or quartz is provided with a TFT 30 having an LDD structure. The TFT 30 includes a scanning line 3a that forms a gate electrode through an insulating film 2 on a semiconductor layer in which a channel region 1a, a source region 1d, and a drain region 1e are formed. A data line 6 a is stacked on the TFT 30 via the first interlayer insulating film 4, and the data line 6 a is electrically connected to the source region 1 d via the contact hole 5. A pixel electrode 9 a is stacked on the data line 6 a via a second interlayer insulating film 7, and the pixel electrode 9 a is electrically connected to the drain region 1 e via a contact hole 8.
[0057]
When the ON signal is supplied to the scanning line 3a (gate electrode), the channel region 1a becomes conductive, the source region 1d and the drain region 1e are connected, and the image signal supplied to the data line 6a becomes the pixel electrode. 9a.
[0058]
A storage capacitor electrode 1f extending from the drain region 1e is formed in the semiconductor layer. The storage capacitor electrode 1f is disposed so that the capacitor line 3b faces the insulating film 2 as a dielectric film, thereby forming a storage capacitor 70. An alignment film 16 made of a polyimide polymer resin is laminated on the pixel electrode 9a, and is rubbed in a predetermined direction by the apparatus shown in FIG.
[0059]
On the other hand, the counter substrate 20 is provided with a first light-shielding film 23 in a region facing the data line 6a, scanning line 3a, and TFT 30 formation region of the TFT array substrate, that is, in a non-display region of each pixel. The first light shielding film 23 prevents incident light from the counter substrate 20 side from entering the channel region 1 a, the source region 1 d, and the drain region 1 e of the TFT 30. A counter electrode (common electrode) 21 is formed over the entire surface of the substrate 20 on the first light shielding film 23. An alignment film 22 made of a polyimide-based polymer resin is laminated on the counter electrode 21, and is rubbed in a predetermined direction by an apparatus similar to that shown in FIG.
[0060]
A liquid crystal 50 is sealed between the element substrate 10 and the counter substrate 20. Thereby, the TFT 30 writes the image signal supplied from the data line 6a to the layer electrode 9a at a predetermined timing. The orientation of the molecular assembly of the liquid crystal 50 changes according to the potential difference between the written pixel electrode 9a and the counter electrode 21 to modulate light and enable gradation display.
[0061]
In the present embodiment, rubbing alignment is performed by using a process of forming a reflective material on the element substrate 10 and the counter substrate 20, for example, a process of forming tungsten silicide, aluminum, or the like serving as a data line or a light shielding film. A mark is formed.
[0062]
2 and 3 show alignment marks on a mother substrate on which a plurality of element substrates (not shown) are formed.
[0063]
FIG. 2 shows that three alignment marks 91 are formed in the vicinity of the alignment notch 92 and in the periphery of the substrate. The alignment marks 91 may be provided at two positions on the substrate.
[0064]
FIG. 3 shows alignment marks 96 and 97 for enabling high-precision alignment. The alignment marks 96 and 97 are formed at the positions of the coordinates (x1, y1) or (x2, y2) of the substrate, respectively. The diameter of the alignment marks 96 and 97 is, for example, about 200 microns. The alignment marks 91, 96, and 97 need only be known in shape, and can be formed in any shape as long as other elements on the substrate are not affected.
[0065]
The alignment marks 91, 96, and 97 formed on the substrate are covered with a permeable oxide film. When the alignment marks 91, 96, 97 are formed on the counter substrate side, the alignment marks 91, 96, 97 are covered with a common electrode.
[0066]
As shown in FIGS. 5 and 6, the counter substrate 20 is provided with a second light shielding film 42 as a frame for partitioning the display area. The second light shielding film 42 is formed of, for example, the same or different light shielding material as the first light shielding film 23.
[0067]
A sealing material 41 that encloses liquid crystal in a region outside the second light shielding film 42 is formed between the element substrate 10 and the counter substrate 20. The sealing material 41 is disposed so as to substantially match the contour shape of the counter substrate 20, and fixes the element substrate 10 and the counter substrate 20 to each other. The sealing material 41 is missing at a part of the center of one side of the element substrate 10 and forms a liquid crystal injection port 78 for injecting the liquid crystal 50 into the gap between the bonded element substrate 10 and the counter substrate 20. . After the liquid crystal is injected from the liquid crystal injection port 78, it is sealed with a sealing material 79.
[0068]
A data line driving circuit 61 and a mounting terminal 62 are provided along one side of the element substrate 10 in a region outside the sealing material 41 of the element substrate 10, and scanning lines are provided along two sides adjacent to the one side. A drive circuit 63 is provided. On the remaining side of the element substrate 10, a plurality of wirings 64 are provided for connecting between the scanning line driving circuits 63 provided on both sides of the screen display area. In addition, a conductive material 65 for electrically connecting the element substrate 10 and the counter substrate 20 is provided in at least one corner of the counter substrate 20.
[0069]
Next, the panel assembly process will be described with reference to FIG. The element substrate 10 (TFT substrate) and the counter substrate 20 are manufactured separately. In the next steps S2 and S7, polyimide to be the alignment films 16 and 22 is applied to the TFT substrate and the counter substrate 20 prepared in steps S1 and S6, respectively. Next, in steps S3 and S8, the alignment film 16 on the surface of the element substrate 10 and the alignment film 22 on the surface of the counter substrate 20 are rubbed.
[0070]
Next, a cleaning process is performed in steps S4 and S9. This cleaning process is for removing dust generated by the rubbing process.
[0071]
When the cleaning process is completed, in step S5, the sealing material 41 and the vertical conductive agent 65 (see FIG. 4) are formed. Next, in step S10, the element substrate 10 and the counter substrate 20 are bonded together, and in step S11, pressure bonding is performed while alignment is performed, and the sealing material 41 is cured. Finally, in step S12, liquid crystal is sealed from a notch provided in a part of the sealing material 41, and the notch is closed to seal the liquid crystal.
[0072]
The apparatus of FIG. 1 is composed of three units. The pre-alignment unit 100 is used in a pre-alignment stage that performs alignment with relatively coarse accuracy. The alignment unit 101 is used in an alignment stage that performs alignment with high accuracy. The rubbing unit 102 is used for a rubbing stage that performs rubbing.
[0073]
The pre-alignment unit 100 has a pre-alignment base 103 on which the substrate 90 shown in FIGS. 2 and 3 is placed. The table 103 can move in the horizontal direction (x direction) and the vertical direction (y direction) in the horizontal plane, and can rotate in the rotation direction (θ direction) in the horizontal plane. The substrate 90 can be sucked and mounted on the table 103.
[0074]
The table 103 is sufficiently smaller than the substrate 90 in the horizontal plane, and the alignment mark 91 formed on the substrate 90 is not positioned on the surface of the table 103 when the substrate 90 is attached to the table 103. A plurality of laser light emitting portions (not shown) are fixed below the base 103, and the plurality of laser light emitting portions have the same positional relationship as the relative positional relationship between the alignment marks 91, and each laser. The light emitting part can emit laser light vertically upward.
[0075]
A plurality of CCDs 104 are fixed to positions on the table 103 facing the laser beam emitting portion. Each CCD 104 can detect the transmittance of the substrate 90 at each position by detecting the light amount of the laser light from the laser light emitting portions facing each other.
[0076]
The detection result of the transmittance by each CCD 104 is supplied to a drive control unit (not shown), and the drive control unit moves and rotates the table 103 in the horizontal plane so that the transmittance of the transmittance detection result of each CCD 104 is minimized. It is like that. Note that the alignment by the drive control unit may be an accuracy that enables alignment in the next alignment stage.
[0077]
The alignment unit 101 has an alignment table 105 on which the substrate 90 is placed. The substrate 90 for which pre-alignment has been completed in the pre-alignment stage is mounted on the stage 105 of the alignment unit 101 by a transport device (not shown). The conveyance accuracy of the conveyance device is relatively high, and the conveyance device can attach the substrate 90 to the table 105 in a state where the alignment accuracy of the pre-alignment is substantially maintained.
[0078]
The base 105 can be attached by adsorbing the substrate 90, and is movable in the horizontal direction (x direction) and the vertical direction (y direction) in the horizontal plane, and the rotational direction (θ direction) in the horizontal plane. ).
[0079]
CCDs 106 and 107 are fixed on the stage 105, and the CCDs 106 and 107 have the same positional relationship as the relative positional relationship between the alignment marks 96 and 97. By the pre-alignment process in the pre-alignment stage, the alignment marks 96 and 97 are positioned in the imaging visual field range of the CCDs 106 and 107, respectively. The CCDs 106 and 107 detect the position of the center of gravity by recognizing the alignment marks 96 and 97 within the imaging field of view, and information indicating the position difference between the center of gravity and a predetermined position, for example, the center within the field of view (hereinafter referred to as the center of gravity). The center of gravity detection signal is output to a drive control unit (not shown).
[0080]
The drive controller is configured to move and rotate the table 105 in a horizontal plane so that the center of gravity detection signals of the CCDs 106 and 107 have a value indicating a minimum positional difference.
[0081]
The platform 105 is sufficiently larger than the substrate 90 in the horizontal plane, and the color of the surface does not adversely affect the image recognition of the CCDs 106 and 107. The CCDs 106 and 107 can change the imaging visual field range by zooming up and zooming down. By zooming up, it is possible to detect the center of gravity with higher accuracy, and by zooming down, the initial positions of the alignment marks 96 and 97 can be reliably captured.
[0082]
When the alignment is completed, the drive control unit rotates the table 105 according to the rubbing angle. A transfer device (not shown) transfers the table 105 to the rubbing unit 102 in order to shift to the rubbing stage.
[0083]
The rubbing unit 102 has a roller 108. When the alignment is completed, the stage 105 of the alignment unit 101 moves below the roller 108 of the rubbing unit 102 with the substrate 90 placed thereon. The roller 108 has a rubbing cloth (not shown) wound around its peripheral surface, and rubbing the alignment films 16 and 22 (see FIG. 7) by rubbing the surface of the substrate 90 on the table 105 that has been conveyed with the rubbing cloth. It has come to give.
[0084]
Next, the operation of the embodiment configured as described above will be described with reference to the flowchart of FIG. FIG. 9 specifically shows the rubbing process in steps S3 and S8 of FIG.
[0085]
A rubbing process for the round substrate 90 on which the plurality of element substrates 10 are formed will be described. In the present embodiment, in the step of forming the reflective material (metal layer) on the element substrate 10, the alignment marks 91, 96, and 97 shown in FIGS. 2 and 3 are formed by the same film formation and the same photo treatment, for example. To do. In step S2 of FIG. 8, polyimide that will serve as the alignment film 16 is applied. Next, the rubbing process of step S3 is performed.
[0086]
Step S ₃ Then, as shown in FIG. 9, first, a pre-alignment stage is performed (step S). ₂₁ ). That is, the substrate 90 on which the alignment film 16 is formed is adsorbed on the table 103. The laser emitting unit of the pre-alignment unit 100 emits laser light from the bottom of the table 103 in the vertical upward direction. This laser light passes through the substrate 90 or the vicinity thereof and is received by the CCD 104 arranged oppositely.
[0087]
The CCD 104 measures the transmittance according to the amount of received light. At the alignment mark 91 position, the laser beam from the laser emitting portion is reflected and does not reach the CCD 104. Therefore, by measuring the transmittance of the CCD 104, it is possible to determine whether or not the position of the laser light passing through the substrate 90 and the position of the alignment mark 91 coincide.
[0088]
In step S22, the CCD 104 detects the transmittance and outputs the detection result to the drive control unit. If the transmittance is not minimized, the drive control unit moves and rotates the table 103 in the horizontal direction to perform position control (step S24). The CCD 104 sequentially detects the transmittance changed by the position control of the drive control unit and outputs it to the drive control unit. The drive control unit drives and controls the table 103 so that the transmittance is minimized. Thus, the substrate 90 is aligned with a relatively coarse accuracy.
[0089]
When the alignment process in the pre-alignment stage is completed, a transport device (not shown) transports the substrate 90 and attaches it to the stage 105 of the alignment unit 101 (step S25). At this point, since the pre-alignment process has already been performed and the conveyance accuracy of the conveyance device is relatively high, the alignment marks 96 and 97 on the substrate 90 are within the imaging visual field range of the CCDs 106 and 107.
[0090]
The CCDs 106 and 107 detect the center of gravity of the alignment marks 96 and 97 by image recognition, and detect the position difference between the center of gravity and a predetermined position within the imaging field-of-view range (step S26). In this way, the CCDs 106 and 107 obtain the center-of-gravity detection signal indicating the difference between the current position of the alignment marks 96 and 97 and the target position, and output it to the drive control unit.
[0091]
The drive control unit moves or rotates the table 105 in the horizontal direction so that the alignment marks 96 and 97 are imaged at target positions based on the gravity center detection signals from the CCDs 106 and 107 (step S28). The CCDs 106 and 107 update the center of gravity detection result according to the position control of the drive control unit, and output it to the drive control unit. When the drive control unit detects that the alignment marks 96 and 97 are imaged at the target position within the imaging visual field range based on the center of gravity detection signal (step S27), the drive control unit determines that the alignment is completed and proceeds to step S29. To do.
[0092]
In step S29, the table 105 is rotated according to the rubbing angle. Next, in step S30, the stage 105 on which the substrate 90 is placed is conveyed to a rubbing stage, and the roller 108 is rotated to perform rubbing processing (step S31).
[0093]
As shown in FIG. 3, the positions of the alignment marks 96 and 97 on the substrate 90 are known, and the angle θ in the rotation direction of the scanning line and the data line of each element substrate 10 is accurately set after the alignment by the alignment stage is completed. It is possible to grasp. The direction of the peripheral surface of the roller 108 in the rubbing unit 102 and the conveying direction of the table 105 are also known, and the rubbing angle can be accurately set to an arbitrary angle by the drive control unit rotating the table 105. .
[0094]
As described above, in the present embodiment, the alignment process in the alignment stage is performed with high accuracy since the center of gravity detection is used, and the rotation accuracy of the stage 105 by the drive control unit is extremely high. It can be controlled with extremely high accuracy.
[0095]
Therefore, by using the apparatus of FIG. 1, a liquid crystal substrate with extremely small rubbing angle variation can be obtained. In the above-described embodiment, the example in which the table 105 is transported to the roller 108 side during the rubbing process after alignment has been described. However, it is obvious that both the roller 108 and the table 105 may be moved. It is.
[0096]
Example 1
The relationship between the rubbing angle (twist angle) and the contrast was determined for the liquid crystal panel in which the rubbing angle was accurately defined using the apparatus shown in FIG. FIG. 10 shows voltage-transmittance characteristics. The greater the difference in transmittance, the higher the contrast ratio. Characteristic A to characteristic F in FIG. 10 are examples of twist angles of 86 °, 88 °, 90 °, 92 °, 94 °, or 96 °, respectively.
[0097]
As shown in FIG. 10, when the transmittance is between 0.1 and 100%, the effective voltage for obtaining the same transmittance decreases as the twist angle increases. That is, when the effective voltage is low, it is advantageous from the viewpoint of transmittance to increase the twist angle.
[0098]
For example, when the effective voltage applied to the liquid crystal is 4 V, the transmittance decreases as the twist angle increases and the contrast ratio is high when the twist angle is in the range of 86 ° to 94 °. In the series having a twist angle of 96 °, the transmittance is increased (deteriorated). However, for example, when the effective voltage is 3.5 V, the contrast ratio is the smallest in the series where the twist angle is 96 ° and the contrast ratio is high.
[0099]
That is, in FIG. 10, the twist angle is increased to about 91 ° to 96 ° with respect to the currently employed twist angle of 90 °. For example, when the effective voltage is 4V, the twist angle is set to 92 ° to 94 °. It can be seen that the contrast ratio can be increased by reducing the transmittance at all black.
[0100]
For this reason, it is understood that it is better to adjust the rubbing angle so that the twist angle is larger than 90 °, for example, within the range of 91 ° to 96 °. In this case, if the rubbing angle is adjusted on the element substrate 10 side, it is affected by the lateral electric field, so the rubbing angle is adjusted on the counter substrate 20 side.
[0101]
By the way, in the dot inversion driving, a horizontal electric field is generated at the four corners of the pixel, so that it is affected by the horizontal electric field in the vertical and horizontal directions. For this reason, it is better to employ line inversion driving. In the case of line inversion driving, a lateral electric field is generated between the upper and lower lines. In a liquid crystal panel or the like used for a notebook personal computer or the like, the rubbing direction is set to an angle of 45 degrees with respect to the polarity reversal direction in order to match the clear viewing direction of the viewing angle characteristics with the usage environment. In this case, when a lateral electric field is generated, the liquid crystal molecules are affected by the lateral electric field with respect to rotation in the tilt direction and rotation in the rubbing direction.
[0102]
For this reason, the rubbing direction is made to coincide with the direction substantially orthogonal to the polarity inversion line, so that the influence of the lateral electric field is limited only to rotation in the tilt direction (reverse tilt). Thereby, the response of the liquid crystal molecules to the lateral electric field generated near the TFT substrate surface can be reduced as much as possible.
[0103]
That is, the rubbing direction on the element substrate 10 side is set to a direction substantially orthogonal to the same polarity inversion line, and the rubbing direction on the counter substrate 20 side is set so that the twist angle is within a range of 91 ° to 96 °, for example. . That is, the rubbing process is performed so that the rubbing direction of the alignment film 22 on the counter substrate 20 side is within a range where the rubbing angle is smaller than 90 °, for example, 84 ° to 89 °.
[0104]
In this way, in the rubbing process performed on the alignment film 16 on the element substrate 10 side, the rubbing direction is made to coincide with the direction substantially orthogonal to the polarity inversion line, so that the influence of the lateral electric field can be suppressed. Then, the rubbing angle on the counter substrate side is set to a range of, for example, 84 °, 85 ° to 89 ° smaller than 90 °, and the twist angle is larger than 90 ° with respect to the rubbing direction on the element substrate 10 side. For example, the angle is set to 91 ° to 96 °. For example, if the effective voltage is about 4 V, the twist angle is set to 91 ° to 95 °, so that a contrast ratio higher than that of the prior art can be obtained.
[0105]
If the twist angle is set to about 96 ° or more, a reverse twist domain may occur and the response of the liquid crystal becomes slow. Therefore, the optimum twist angle range is about 91 ° to 96 °. Is considered to be within.
[0106]
(Example 2)
FIG. 11 is a graph showing the relationship between the effective voltage and the twist angle for obtaining the optimum contrast ratio, with the horizontal axis representing the elevation angle from the normal direction in a specific plane and the vertical axis representing the contrast ratio. FIG. 11 shows an example of the transmittance ratio when the effective voltage is 1V and 4V, that is, the angle dependency of the contrast. The rubbing direction (upward direction on the paper surface) of the element substrate of the liquid crystal panel is 90 °. In each figure, the solid line graph shows the viewing angle characteristics in the AA ′ plane (135-315 °), and the dotted line graph is It shows viewing angle characteristics in the BB ′ plane (45 ° -225 °), so-called clear vision direction.
[0107]
In Example 2, the effective voltage applied to the liquid crystal is also considered. As described above, the optimum voltage application amount in design is substantially determined by the cell gap and Δε. When the effective voltage applied to the liquid crystal when the normally white TN liquid crystal is all black is about 4 V, the contrast peak shifts the viewing angle characteristic from the center in the conventional technique. In the projector, the contrast ratio can be improved by setting a contrast peak in the vicinity of the light distribution direction distribution, that is, in the normal direction of the liquid crystal panel. For this reason, when the effective voltage is about 4 V, the contrast is lowered.
[0108]
As described above, even if the effective voltage is 4 V, the contrast ratio can be improved by making the twist angle larger than 90 °. However, the projector not only has a high absolute value of the contrast ratio, but also improves the contrast by setting the peak of the viewing angle characteristic at the center, that is, by setting the contrast peak in the normal direction of the liquid crystal panel. Can be made. In a projector, it is not necessary to consider the wide viewing angle.
[0109]
This viewing angle characteristic is affected not only by the twist angle but also by the effective voltage. For this reason, the twist angle, effective voltage, and viewing angle characteristics are related and adjusted.
[0110]
FIG. 11 shows the results of measuring viewing angle characteristics (contrast ratio) when the twist angle and effective voltage are changed.
[0111]
As shown in FIG. 11, when the effective voltage for driving the liquid crystal is 4 V, a good contrast having a contrast peak at the center and a relatively high contrast value can be obtained with a twist angle of 94 °. I understand. That is, in this case, the rubbing angle may be set to 86 °.
[0112]
Thus, the optimum contrast can be obtained by appropriately setting the voltage application amount and the twist angle (rubbing angle) to the liquid crystal.
[0113]
Example 3
FIG. 12 shows the results of measuring the contrast ratio of the diagonal 1.8 cm SVGA liquid crystal panel manufactured according to the first embodiment. FIG. 12 is a graph showing the relationship between the twist angle and contrast, with the twist angle on the horizontal axis and the contrast ratio on the vertical axis. The contrast ratio is improved by setting the twist angle to an angle larger than 90 ° employed in the conventional twisted nematic liquid crystal, that is, up to 96 ° in the example of FIG.
[0114]
【The invention's effect】
As described above, according to the present invention, the alignment mark is formed on the substrate, and the position is adjusted using the alignment mark, whereby the alignment accuracy of the substrate can be improved, and the rubbing angle can be improved. There is an effect that the variation in contrast characteristics can be reduced by reducing the variation.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an apparatus for manufacturing a liquid crystal device according to a first embodiment of the invention.
FIG. 2 is an explanatory diagram showing a round substrate on which a rubbing process is performed in the liquid crystal device manufacturing apparatus of FIG. 1;
3 is an explanatory view showing a round substrate on which a rubbing process is performed in the liquid crystal device manufacturing apparatus of FIG. 1;
FIG. 4 is an equivalent circuit diagram of various elements and wirings in a plurality of pixels constituting a pixel region of the liquid crystal device.
FIG. 5 is a plan view of an element substrate such as a TFT substrate as viewed from the counter substrate side together with each component formed thereon.
6 is a cross-sectional view showing the liquid crystal device after the assembly process for sealing the liquid crystal by bonding the element substrate and the counter substrate, cut along the line HH ′ in FIG. 5;
FIG. 7 is a cross-sectional view illustrating a liquid crystal device in detail.
FIG. 8 is a flowchart showing a panel assembly process.
FIG. 9 is a flowchart for explaining the operation of the embodiment;
10 is a graph for explaining Example 1. FIG.
FIG. 11 is a graph for explaining Example 2;
12 is a graph for explaining Example 3. FIG.
[Explanation of symbols]
90 ... Board
100: Pre-alignment unit
101 ... Alignment unit
102 ... Rubbing unit
103 ... Pre-alignment stand
105 ... Alignment stand
104,106,107 ... CCD
108 ... Laura

Claims (12)

An alignment base on which a liquid crystal substrate is placed so that it can freely move and rotate in any direction within a horizontal plane;
Centroid detecting means for detecting the centroid of the rubbing alignment mark formed on the liquid crystal substrate placed on the alignment table;
An alignment unit comprising: an alignment drive control unit configured to perform alignment by driving the table based on a detection result of the gravity center detection unit in order to move the gravity center position of the rubbing alignment mark to a predetermined position. When,
A pre-alignment unit for performing pre-alignment processing of the liquid crystal substrate in order to place the liquid crystal substrate on the alignment table so that the center of gravity of the rubbing alignment mark is located within a predetermined position range; Have
The pre-alignment unit is formed on a pre-alignment base on which a liquid crystal substrate is placed and can be moved and rotated in an arbitrary direction within a horizontal plane, and a liquid crystal substrate placed on the pre-alignment base A transmittance detecting means for detecting the transmittance using the aligned alignment mark, and a pre-alignment for performing pre-alignment by driving the pre-alignment base based on the transmittance detection result by the transmittance detecting means. An apparatus for manufacturing a liquid crystal device.   The apparatus for manufacturing a liquid crystal device according to claim 1, wherein the center of gravity detection unit detects the center of gravity of the rubbing alignment mark by image recognition processing.   After alignment by the alignment drive control means, there is a rubbing roller provided on a transfer path on which the alignment table on which the liquid crystal substrate is mounted is transferred, and is mounted on the alignment table and transferred. The apparatus for manufacturing a liquid crystal device according to claim 1, further comprising a rubbing unit for rubbing the liquid crystal substrate.   The liquid crystal device manufacturing apparatus according to claim 1, wherein an angle between the liquid crystal device and a rubbing roller is adjusted by the alignment.   The alignment drive control means includes: an alignment table on which the liquid crystal substrate is placed according to a specified rubbing angle before the alignment table is transferred to the rubbing unit after the alignment process is completed. The liquid crystal device manufacturing apparatus according to claim 4, wherein the liquid crystal device is rotated. A procedure for placing the liquid crystal substrate on a pre-alignment table that can be freely moved and rotated in a horizontal plane; and
A transmittance detection procedure for performing transmittance detection using an alignment mark formed on a liquid crystal substrate placed on the pre-alignment stage;
Based on the transmittance detection result in the transmittance detection procedure, the pre-alignment stage is driven, and the center of gravity position of the rubbing alignment mark formed on the liquid crystal substrate is located within a predetermined position range. A pre-alignment procedure for pre-aligning the liquid crystal substrate;
A procedure for placing the pre-aligned liquid crystal substrate on an alignment table that can freely move and rotate in an arbitrary direction within a horizontal plane;
A centroid detection procedure for detecting the centroid of the rubbing alignment mark on the liquid crystal substrate placed on the alignment table;
An alignment procedure for aligning the liquid crystal substrate by driving the alignment base based on the detection result of the centroid detection procedure in order to move the centroid position of the rubbing alignment mark to a predetermined position. A method of manufacturing a liquid crystal device.   After the alignment, a rubbing process is performed on the liquid crystal substrate placed and transported on the alignment table by a rubbing roller provided on a transport path on which the alignment platform on which the liquid crystal substrate is placed is transported. The method for manufacturing a liquid crystal device according to claim 6, further comprising a rubbing procedure.   8. The liquid crystal according to claim 7, wherein the alignment procedure includes a procedure of rotating an alignment table on which the liquid crystal substrate is placed according to a specified rubbing angle before the rubbing procedure. Device manufacturing method.   8. The method of manufacturing a liquid crystal device according to claim 7, wherein in the alignment procedure, the alignment table is rotated so that a rubbing angle of the liquid crystal device is 89 ° to 85 °.   A liquid crystal device manufactured by the manufacturing method according to claim 6.   The liquid crystal device according to claim 10, wherein the liquid crystal device has a twist angle in a range of 91 ° to 95 °.   In the liquid crystal device, the rubbing direction of the element substrate is orthogonal to the scanning line direction, and the rubbing direction of the counter substrate is in the range of 85 ° to 89 ° with respect to the rubbing angle of the element substrate. The liquid crystal device according to claim 10.

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