JPS6330829A - Manufacture of liquid crystal display device - Google Patents

Abstract

PURPOSE:To obviate a fall of a memory property and a contrast, which is caused by an ionic impurity, by applying at least once or more a DC electric field which is >=300V, and also, whose applying time is <=0.1sec, to a ferroelectric liquid crystal which has been injected to a liquid crystal display device, through an electrode. CONSTITUTION:To a ferroelectric liquid crystal which has been injected to a liquid crystal display device, a DC electric field which is >=300V, and also, whose applying time if <=0.1sec is applied once or more through an electrode of the liquid crystal display device. For instance, the liquid crystal display device in heated, a liquid crystal is set to Iso phase, and thereafter, the lower side electrode is grounded, a square wave of 1,000V voltage and 1ms pulse width is applied to the upper side electrode, and it is executed repeatedly four times in total at an interval of about 10sec. Thereafter, when slow cooling is executed and the liquid crystal is oriented and driven at a room temperature, a fall of a contrast and a memory property, which is caused by an ionic impurity is not recognized, and even after a DC has been applied continuously, the same driving as before the application can be executed, and an inversion of a direction of a spontaneous polarization is not recognized.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a liquid crystal display device.

[Conventional technology]

The conventional manufacturing method for liquid crystal display devices involves injecting ferroelectric liquid crystal into a cell and then slowly cooling it from the isotropic phase (hereinafter referred to as the θ0 phase) to the smectic ○ phase (hereinafter referred to as the SmO* phase). It is common to orient the ferroelectric liquid crystal molecules by applying electricity, and it is very rare to carry out energization treatment, and even when energization treatment is carried out, alternating current or direct current voltage is continuously applied for a long time. It was common.

[Problem that the invention seeks to solve]

However, in the above-mentioned conventional technology, if ionic impurities are contained in the ferroelectric liquid crystal, as shown in FIG.
Before driving, positively charged ionic impurities (hereinafter referred to as ■ ions) and negatively charged ionic impurities (hereinafter referred to as e ions) are uniformly dispersed throughout the cell. However, when this liquid crystal display device is driven and a DC component continues to be applied from the upper substrate to the lower substrate as shown in FIG. Ions are unevenly distributed near the lower substrate surface, resulting in a decrease in memory performance and contrast, resulting in significant differences in memory performance and contrast between adjacent pixels, and in the worst case, ions unevenly distributed on the upper and lower substrate surfaces. There is a problem in that the direction of spontaneous polarization is reversed due to the Coulomb force exerted by sexual impurities, making it impossible to use it as a liquid crystal display device.

Therefore, the present invention aims to solve these problems.
The purpose is to provide a liquid crystal display device that does not suffer from problems with memory and contrast between adjacent pixels due to ionic impurities, and also does not have spontaneous polarization reversal even if a DC component is continuously applied for a long time. It is in.

[Means for solving problems]

In the method for manufacturing a liquid crystal display device of the present invention, at least 50
The method is characterized in that a DC electric field is applied at least once for an application time of V or more and an application time of L1 seconds or less.

[Effect]

According to the above structure of the present invention, when a DC electric field of at least 5 oov or more and an application rJ time Q of 1 second or less is applied to the liquid crystal display device after the ferroelectric liquid crystal has been injected through the electrodes, the The ionic impurities are momentarily pulled by the electric field and are implanted into the alignment film. Therefore, the amount of ionic impurities in the liquid crystal layer is drastically reduced to the point where it can be ignored.

Furthermore, since the ionic impurities once implanted into the alignment film hardly ever return to the liquid crystal layer, a state in which almost no ionic impurities exist in the liquid crystal layer is maintained semipermanently. As a result, deterioration in memory performance and contrast caused by ionic impurities is eliminated.

Also, due to the Coulomb force exerted by the ionic impurities implanted into the alignment film, while the upward and downward states of spontaneous polarization are originally bistable, either the upward or downward state of spontaneous polarization is It is possible that the film is stable and the other state is meta-stable, resulting in a decrease in memory performance in this state (hereinafter referred to as one-sided memory), but this does not occur uniformly in all pixels in the liquid crystal display device. Unlike the case where ionic impurities are present in the liquid crystal layer, the memory performance does not differ depending on the pixel, and uniform memory performance can be obtained for all pixels.

[Example 1] FIG. 1 is a sectional view of a liquid crystal display device used in an example of the present invention. 2 is a transparent electrode, and in order to reduce the resistance, a thick indium oxide film with a film thickness of 1500λ was used. 10 is S10. The film thickness was 3000λ to prevent upper and lower sheets from collapsing. An alignment film having the property of aligning liquid crystal molecules parallel to the substrates is formed on both the upper and lower substrate surfaces, and the alignment film 3-1 on the upper substrate surface is rubbed with cotton. 9 is a ferroelectric liquid crystal layer.

After heating this liquid crystal display device and making the liquid crystal 180 phases, the lower electrode is grounded, and a voltage of 1000 V is applied to the lower electrode.
A rectangular wave with a pulse width of 1 m13 was applied, and this was repeated a total of 4 times at intervals of about 10 seconds. After this, when we slowly cooled the liquid crystal to align the liquid crystal and drove it at room temperature, no deterioration in contrast or memory due to ionic impurities was observed, and even after continuing to apply direct current, the same driving as before application was possible. , no reversal of the direction of spontaneous polarization was observed.

[Example 2] Figure 2 is a cross-sectional view of a liquid crystal display device used in an example of the present invention, and Figure 5 is a plan view of a substrate used in this liquid crystal display device. The same pattern was used for both the upper and lower substrates. In order to apply an electric field uniformly to all pixels, the terminals are grouped together at the edge of the substrate, and N1 plating 11 is applied to lower the resistance of the component. An alignment film having the property of aligning liquid crystal molecules parallel to the substrate is applied to the upper and lower substrate surfaces, and an alignment film 3 on the upper substrate surface is applied.
-1 was rubbed with cotton. Using these two substrates, a simple IJ sock liquid crystal display device was made and ferroelectric liquid crystal was injected into it.

After heating this liquid crystal display device and setting the liquid crystal to the so-so phase, the lower electrode is grounded, and a voltage of 15 DOV and a rectangular pulse width of 08 days is applied to the upper electrode at intervals of about 10 seconds. This was repeated a total of 4 times. After this, slow cooling is performed to orient the liquid crystal, and the common part of the terminals is cut 1til! When we drove the device at room temperature after applying it, no deterioration in contrast or memory due to ionic impurities was observed, and even after continuing to apply direct current, the same driving as before application was possible, and no reversal of the direction of spontaneous polarization was observed. He was unable to move and made even movements.

[Example 3] In Example 1, the electric field applied to the liquid crystal display device was a voltage of 10
00V and an application time of 1 to 8, but it was more effective to apply a higher voltage and a shorter application time.

The number of times of application depends on the applied voltage and application time, but if the applied voltage is 100 (17) and the application time is 1 m day, applying it 4 times will have a sufficient effect, and even if it is applied more than that, no significant effect will be obtained. There wasn't.

Example 1. In Example 2, the liquid crystal display device was heated to make the ferroelectric liquid crystal into the 8O phase and then an electric field was applied.
) or SmO* phase, there was an effect. However, the SmA phase.

If applied in the SmO* phase, the orientation may be somewhat distorted,
Since reorientation is necessary, it is thought to be more efficient to slowly cool and orient the impression port in the 80-phase process.Example 1. In Example 2, it was only necessary to wait for a while after application, but if the terminals were grounded during that time to remove the charge accumulated in the liquid crystal display device, the applied electric field would be more effective the next time it was applied. Effective for.

In addition, the direction of the applied electric field is as in Example 1. Together with Example 2,
They were originally facing the same direction, but each time the electric field is applied, the direction of the electric field is reversed, and the bias in the amount of ■ ions and e-ions injected into the upper and lower alignment films becomes smaller, so one side's memory due to the bias of the ions becomes smaller. This did not occur and more stable memory performance was obtained.

〔Effect of the invention〕

As described above, according to the present invention, the ionic impurities contained in the liquid crystal are injected into the alignment film by an electric field, so that most of the ionic impurities in the liquid crystal are removed, resulting in a decrease in memory performance and contrast. Therefore, a liquid crystal display device with uniform memory properties and excellent display quality can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a liquid crystal display device used in an embodiment of the present invention. FIG. 2 is a sectional view of a liquid crystal display device used in an embodiment of the present invention. FIG. 3 is a plan view of a substrate used in the liquid crystal display device of FIG. 2. FIG. 4 is a diagram showing the distribution of ionic impurities within the liquid crystal display device before driving. FIG. 5 is a diagram showing the distribution of ionic impurities within the liquid crystal display device after applying and driving a DC electric field. 1...Glass substrate 2...Transparent EiA'#L pole 5-1.3-2
°°°...Alignment film 4...Positively charged ionic impurity 5...Negatively charged ionic impurity 6... ...Liquid crystal molecules 7 after the electric field is turned off.
...... Direction of electric field 8゛° ... Sealing material 9 ... ... Liquid crystal layer 10 ......Sin, film 11 ...・・N1 plating or above Applicant Seiko Epson Co., Ltd. Agent Representative Patent Attorney (1 other person) 1,,,' ~

Claims (1)

[Claims] In a method for manufacturing a liquid crystal display device comprising a ferroelectric liquid crystal sandwiched between a pair of substrates, the ferroelectric liquid crystal injected into the liquid crystal display device is supplied with a voltage of at least 300 V or more via an electrode of the liquid crystal display device. A method for manufacturing a liquid crystal display device, comprising applying a DC electric field for an application time of 0.1 seconds or less at least once.