JP3097351B2 - Liquid crystal display panel manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an active element type liquid crystal display panel, and more particularly to a method of manufacturing an active element type liquid crystal display panel which performs multi-tone display.

A liquid crystal display device in which a liquid crystal is filled in a gap between a pair of glass substrates on which a transparent electrode or the like is formed is already used in many fields. In particular, a TFT type liquid crystal display panel in which the voltage of each pixel is controlled by an active element (TFY) has a CR
Since display characteristics comparable to those of a T (cathode tube) can be obtained, they are used in the field of portable televisions and various OA equipments, but developments aiming at higher image quality and higher performance are being actively conducted.

[0003] Such a liquid crystal display panel has been changed from an easy-to-manufacture and inexpensive simple matrix system to an MIM (Metal-Insul- ble).
ator-Metal) Two-terminal device, TFT (Thin-Film-Transisto)
r) There is a tendency to replace the active matrix method (active element type) using active elements such as elements and TFD (Thin-Film-Diode) elements.

[0004]

2. Description of the Related Art FIG. 2 is a plan view showing a pattern of a TFT substrate in a conventional active element type liquid crystal display panel using TFTs, and FIG. 3 is a schematic view showing a cross section of the liquid crystal display panel.

In FIGS. 2 and 3, 1 is a TFT forming substrate (glass substrate), 2 is a TFT, 3 is a scanning electrode, 4 is a data electrode, 5 is a pixel electrode, 6 is a liquid crystal display panel, and 7 is a substrate 1. An opposing substrate (glass substrate), 8 an opposing electrode opposing the pixel electrode 5, 9 a liquid crystal, 10 and 11 alignment films,
12, 13 are polarizing films.

In such a display panel 6, a TFT
A point to be noted in the preparation of the second class is a measure against static electricity generated during the preparation process. Specifically, TFT
When a high voltage exceeding the withstand voltage of the TFT 2 is applied between the second scanning electrode 3 and the data electrode 4, the TFT 2 is broken.

Therefore, conventionally, a method has been used in which the scan electrode group and the data electrode group are electrically short-circuited outside the display area of the display panel, and finally the short-circuit is released.

[0008]

In the conventional short-circuit prevention method, the potential between the scan electrode 3 and the data electrode 4 is kept constant, so that the electrostatic breakdown of the TFT 2 can be prevented. However, since the TFT 2 is kept off and the potential of the pixel electrode 5 cannot be controlled, a potential difference occurs between the pixel electrode 5 and the counter electrode 8 due to static electricity.

In general, the potential difference between the pixel electrode 5 and the counter electrode 8 is naturally reduced to about 100 mV or less by natural discharge, so that a normal on-off display and a certain gradation display are performed. It is not a practical problem.

[0010] However, since the voltage cannot be completely reduced to 0 V, when performing multi-tone display of 16 tones or more, tone unevenness occurs in the panel. The reason why the voltage cannot be completely reduced to 0 V is that when a potential difference is generated between the pixel electrode 5 and the counter electrode 8 due to static electricity, impurity ions in the liquid crystal move to the vicinity of the electrode due to the potential difference, and the surface of the alignment film 10 Negative ion 15 (or positive ion) of impurities contained in 9
This is because the positive ions 14 (or the negative ions 15) of the impurities contained in the liquid crystal 9 are deposited on the surface of the alignment film 11.

Therefore, after the display panel 6 is completed, even if the potentials of the pixel electrode 5 and the counter electrode 8 are controlled, the impurity ions 14 and 15 adsorbed on the alignment films 10 and 11 are present in the region where the impurity ions 14 and 15 are present. , 15 occur, and a potential difference remains between the pixel electrode 5 and the counter electrode 8.

Since the arrangement of the impurity ions 14 and 15 is difficult to completely dissociate once deposited, the potential difference between the pixel electrode 5 and the counter electrode 8 does not return to 0 V, and the display quality deteriorates. Will do.

[0013]

SUMMARY OF THE INVENTION In a liquid crystal display panel in which the potential of a pixel is controlled by using an active element, the method of the present invention which focuses on impurity ions in the liquid crystal for the purpose of improving display quality is provided by the first glass. A plurality of active elements for controlling pixel potential, pixel electrodes connected to the active elements, scan electrodes connected to the active elements, and data electrodes connected to the active elements are formed on the substrate, and are formed on the second glass substrate. Forms a counter electrode facing the pixel electrode, fills a gap between the electrode forming surface of the first glass substrate and the electrode forming surface of the second glass substrate with liquid crystal, and In a liquid crystal display panel in which a polarizing film is adhered to the outer surface of a glass substrate, the display panel is heated to a temperature that does not adversely affect the constituent members, and a potential is applied to the pixel electrode and the counter electrode. Orientation formed on a glass substrate And it is to dissociate the impurity ions in the liquid crystal from the alignment film be deposited on an alignment film formed on the glass substrate of the second.

[0014]

In order to solve the phenomenon that the potential difference between the pixel electrode 5 and the counter electrode 8 does not return to 0 V, the inventors of the present application focused on the impurity ions 14 and 15 in the liquid crystal and focused on the alignment films 10 and 1.
The dissociation method of returning the impurity ions 14 and 15 deposited on 1 into the liquid crystal 9 was studied.

First, it was confirmed that if the potential difference between the pixel electrode 5 and the counter electrode 8 was set to 10 mV or less, there would be no problem in practical display quality. Thus, it was first confirmed that when DC 10 V was intentionally applied between the pixel electrode 5 and the counter electrode 8 for 1 hour, a residual bias voltage of about 200 mV was generated between the pixel electrode 5 and the counter electrode 8 thereafter. Thereafter, the temperature dependence of the time required for the bias voltage to attenuate with both electrodes 5 and 8 short-circuited and the residual potential difference to become 10 mV or less was examined.

FIG. 1 is a diagram showing the temperature dependence of the time required to reduce the residual potential difference to 10 mV or less. In FIG. 1 in which the horizontal axis is the display panel temperature (° C.) and the vertical axis is the time (h), according to the temperature dependence characteristic A of the residual bias obtained by connecting the plotted measured values with a straight line, at a temperature of 40 ° C., about 20 It was found that the residual bias attenuated to less than 10 mV in about 40 minutes at 60 ° C. This is the orientation film
It is considered that the ions 14, 15 adsorbed on the surfaces of 10, 10 are easily dissociated.

Therefore, a predetermined potential is applied between the pixel electrode 5 and the counter electrode 8 for about 20 hours or heated to 80 ° C. in an atmosphere in which the liquid crystal display panel 6 is heated to 40 ° C. by the above means. When a predetermined potential is applied between the pixel electrode 5 and the counter electrode 8 for about 6 minutes in an atmosphere, ions 1
4, 15 are dissociated from the alignment films 10, 11, and the residual bias potential difference is attenuated to 10 mV or less, and the display quality is improved.

Such an effect generally occurs when an applied voltage at which a voltage between both electrodes at a high temperature is temporally averaged and there is no potential difference, for example, a symmetrical square wave, is used. Although the processing time becomes shorter, the present invention recommends 40 ° C. to 80 ° C. at the present time in consideration of practicality from the processing time and physical properties of panel components such as liquid crystal.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method according to the present invention is applied to a case where the number of pixels is 640.times.480.
The embodiment applied to the FT liquid crystal display panel is shown in FIGS.
This will be described with reference to 2 and 3.

On the surface of the glass substrate 1, a large number of TFTs 2, scanning electrodes 3, data electrodes 4, pixel electrodes 5, and alignment films 10 are provided.
To form However, when forming the TFT 2, the scanning electrode 3, the data electrode 4, and the alignment film 10, each scanning electrode 3 and the data electrode 4 are short-circuited at a position where the glass substrate 7 is exposed.

Next, the substrate 1 on which the TFT 2 and the like are formed,
The opposing electrode 8 and the substrate 7 on which the alignment film 11 is formed are opposed to each other, and the periphery of the substrates 1 and 7 having an appropriate gap is joined with a sealing material having a liquid crystal injection port.

Next, the gap between the substrates 1 and 7 is filled with the liquid crystal 9, and then the liquid crystal injection port is sealed.
Then, the short-circuit portion between the scanning electrode 3 and the data electrode 4 is released, and the assembly of the display panel 6 is completed.

When the potential between the pixel electrode 5 and the counter electrode 8 was measured by selecting 20 arbitrary points on the display panel 6 at the time of the completion of the assembly, a potential of ± 10 to ± 250 mV was generated. .

Therefore, a large number of scanning electrodes 3 are connected via a first conductive rubber (not shown), and a large number of data electrodes 4 are connected via a second conductive rubber (not shown). 8
In accordance with the temperature dependency characteristic A of the residual bias shown in FIG. 1, a DC voltage of 15 V is applied to the scanning electrode 3 in an oven heated to 80 ° C. for 15 minutes and left.

Next, the display panel 6 was cooled in a furnace until it reached room temperature and then taken out, and the potential between the pixel electrode 5 and the counter electrode 8 was measured. Was done.

Such an effect is obtained by applying an applied voltage such that the potential applied to the pixel electrode 5 and the counter electrode 8 at high temperature has no difference on average over time, for example, the applied potential of the pixel electrode 5 is ± 3.
A symmetrical square wave of V, which generally occurs when the potential applied to the counter electrode 8 is set to 0 V, or when a DC ON voltage for driving the pixel is applied to the scanning electrode 3 and the same potential is applied to the data electrode 4 as the counter electrode 8. However, it is most simple to electrically short the pixel electrode 5 and the counter electrode 8.

In order to perform such a process during the manufacturing process of the liquid crystal display panel, it is desirable that the process be performed after the polarizing film is attached. This is to attenuate the bias caused by large static electricity when attaching the polarizing film.

Although the processing time is shortened as the temperature is increased, the upper limit of the heating temperature is set to 80 ° C. at the present time in consideration of the physical properties of the panel constituting members such as the liquid crystal. 40 ° C is recommended from the practicality of time.

Further, in order to electrically short-circuit the pixel electrode 5 and the counter electrode 8, it is necessary to make the active element 2 conductive. The same scanning voltage as that at the time may be applied, but more simply, the scanning electrodes 3 may be connected by means of a conductive paste or the like, and the ON voltage for driving the pixels may be applied by DC.

[0030]

As described above, according to the present invention, uniform display can be realized over the entire panel, and display quality can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a temperature dependence characteristic of a residual bias in a liquid crystal display panel.

FIG. 2 is a plan view showing a pattern of a TFT substrate of an active element type liquid crystal display panel.

FIG. 3 is an explanatory view of impurity ions in a liquid crystal display panel.

[Explanation of symbols]

 1, 7 is a glass substrate 2 is a pixel potential controlling active element 3 is a scanning electrode 4 is a data electrode 5 is a pixel electrode 6 is a liquid crystal display panel 8 is a counter electrode 9 is a liquid crystal 10, 11 is an alignment film 12, 13 is a polarizing film 14,15 are impurity ions in liquid crystal

Continuation of the front page (56) References JP-A-51-30760 (JP, A) JP-A-63-30829 (JP, A) JP-A-1-167728 (JP, A) JP-A-1-281420 (JP) JP-A-5-27241 (JP, A) JP-A-5-34698 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1337 G02F 1/13 101

Claims (4)

(57) [Claims] 1. A first glass substrate (1) has a plurality of pixel potential controlling active elements (2), and pixel electrodes connected to the active elements.
(5), forming a scanning electrode (3) connected to the active element, a data electrode (4) connected to the active element, and a first alignment film (10), and forming the same on a second glass substrate (7). Is a counter electrode facing the pixel electrode
(8) A second alignment film (11) is formed, and a liquid crystal (9) is filled in an opposing gap between the electrode forming surface of the first glass substrate and the electrode forming surface of the second glass substrate. In a liquid crystal display panel (6) in which polarizing films (12, 13) are adhered to the outer surfaces of the first and second glass substrates, the display panel (6) is heated to a temperature that does not adversely affect the components. A potential is applied to the pixel electrode (5) and the counter electrode (8) to apply the first and second alignment films (10, 1).
1. A method for manufacturing a liquid crystal display panel, comprising: dissociating impurity ions (14, 15) in the liquid crystal (9) adhered to (1) from the alignment films (10, 11). 2. A plurality of active elements (2) for controlling a pixel potential on a first glass substrate (1), and pixel electrodes connected to the active elements.
(5), a scan electrode (3) connected to the active element, a data electrode connected to the active element and detachably short-circuited to the scan electrode
(4) forming a first alignment film (10) and forming a second glass substrate
In (7), a counter electrode (8) facing the pixel electrode and a second alignment film (11) are formed, and the electrode forming surface of the first glass substrate and the electrode forming surface of the second glass substrate are formed. Liquid crystal (9)
After the polarizing films (12, 13) are adhered to the outer surfaces of the first and second glass substrates, the short circuit between the scanning electrode and the data electrode is released, and then the temperature is set at 40 ° C. to 80 ° C. Applying an electric potential to the pixel electrode and the counter electrode in an atmosphere heated to
2. The method according to claim 1, wherein an average value of the potential applied to the pixel electrode is substantially equal to an average value of the potential applied to the counter electrode. 3. A first glass substrate (1) has a plurality of active elements (2) for controlling pixel potential, and pixel electrodes connected to the active elements.
(5) The scanning electrode (3) connected to the active element. The data electrode connected to the active element and detachably short-circuited to the scanning electrode.
(4) forming a first alignment film (10) and forming a second glass substrate
In (7), a counter electrode (8) facing the pixel electrode and a second alignment film (11) are formed, and the electrode forming surface of the first glass substrate and the electrode forming surface of the second glass substrate are formed. Liquid crystal (9)
After the polarizing films (12, 13) are adhered to the outer surfaces of the first and second glass substrates, the short circuit between the scanning electrode and the data electrode is released, and then the temperature is set at 40 ° C. to 80 ° C. In a heated atmosphere, a drive-on voltage of the pixel is applied to the scan electrode in a DC state, and a substantially same potential as the counter voltage is applied to the data electrode, and the potential of the potential applied to the pixel electrode is reduced. 2. The method according to claim 1, wherein the average value and the average value of the potential applied to the counter electrode are substantially equal. 4. The liquid crystal display panel according to claim 1, wherein said pixel electrode (5) and said counter electrode (8) are electrically short-circuited, and said short-circuit is released after applying said potential. Manufacturing method.