JPH10153781A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device, which prevents a display defect such as screen sticking without making impurity ions enter a display area from a seal material, in a liquid crystal display device, which has a couple of substrates arranged opposite to each other, liquid crystal charged and sealed off between the substrates, the seal material sealing the peripheral edge of the substrates, and orientation films provided on the substrates. SOLUTION: In the liquid crystal display device having the couple of substrates 10 and 20 which are arranged opposite to each other, the liquid crystal 40, which is charged between the substrates, the seal material 30, which seals off the peripheral edge of the substrates, and the orientation films 16 and 24, which are provided to the substrates, the orientation films 16 and 24 in an area 62 nearby the peripheral edge of the substrates 10 and 20 have vertical components to the peripheral edge and are oriented from the peripheral edge to the inside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pair of substrates arranged opposite to each other, a liquid crystal sealed between the substrates, a sealing material for sealing the periphery of the substrates, and an alignment film provided on the substrates. And a liquid crystal display device having the same.

[0002]

2. Description of the Related Art A liquid crystal display device has a substrate provided with a pixel electrode and a substrate provided with a counter electrode. These two substrates are arranged to face each other. Liquid crystal is sealed between the opposing substrates, and the periphery of the substrate is sealed with a sealing material so that the liquid crystal does not leak. Further, each substrate has an alignment film for arranging liquid crystals.

In the liquid crystal display device having such a configuration, impurity ions dissolve into the liquid crystal from the sealing material at the periphery of the substrate, causing display defects such as image sticking. In particular, in the case of a single-lamp type liquid crystal display device using a backlight, the backlight becomes high temperature in order to increase the size of the display device and improve brightness,
The impurity ions are easily dissolved in the liquid crystal. Therefore, it is necessary to prevent impurity ions from entering the display region.

In order to prevent impurity ions from entering the display area, the following technique has been proposed (Japanese Patent Application No. Hei.
2-249202). This technique will be described with reference to FIG. FIG. 6 is a sectional view showing the proposed liquid crystal display device. On one substrate 110, pixel electrodes 112 are arranged in a matrix. Each pixel electrode 112 is provided with a TFT element (not shown).
The FT elements are commonly connected by a bus line 114. The liquid crystal 140 is provided on the pixel electrode 112 and the TFT element.
The alignment film 116 for arranging is formed.

[0005] On the other substrate 120, one substrate 11
A counter electrode 122 is formed so as to face the plurality of pixel electrodes 112 arranged at zero. On the counter electrode 122, an alignment film 124 for arranging the liquid crystal 140 is formed. Liquid crystal 140 is sealed between the substrate 110 and the substrate 120. To prevent the liquid crystal 140 from leaking,
The peripheral portions of 0 and 120 are sealed with a sealing material 130.

The substrates 110 and 120 near the seal material 130
On top, auxiliary electrodes 180 and 182 are provided, respectively. The auxiliary electrodes 180 and 182 are provided near four sides of the liquid crystal display device. Auxiliary electrode 180 and auxiliary electrode 182
A DC voltage is applied between them. For example, a DC voltage is applied so that the auxiliary electrode 180 is negative and the auxiliary electrode 182 is positive.

When the temperature becomes high due to the heat generated by the backlight or the like, the positively charged impurity ions 150 and the negatively charged impurity ions 152 melt out of the sealing material 130. The positively charged impurity ions 150 are attracted to and captured by the auxiliary electrode 180 which is a negative electrode. -The charged impurity ions 152 are attracted to and captured by the auxiliary electrode 182 which is a positive electrode.

As described above, in the proposed liquid crystal display device, the impurity ions 150 and 152 are formed in the display region 160.
Since it is prevented from invading the screen, display defects such as screen burn-in can be prevented. .

[0009]

However, also in the above-mentioned liquid crystal display device, if the impurity ions 150, 152 cannot be captured on the auxiliary electrodes 180, 182, the missed impurity ions 150, 152 are displayed in the display region 1.
60. An object of the present invention is to provide a liquid crystal display device capable of preventing display defects such as screen burn-in without causing impurity ions from a sealant to enter a display region.

[0010]

The object of the present invention is to provide a pair of substrates arranged opposite to each other, a liquid crystal sealed between the pair of substrates, a sealing material for sealing a peripheral edge of the pair of substrates,
In a liquid crystal display device having an alignment film provided on the pair of substrates, the alignment film near the periphery of the pair of substrates has a component perpendicular to the periphery and goes inward from the periphery. This is achieved by a liquid crystal display device characterized in that a directional alignment treatment is performed. This prevents the impurity ions from penetrating into the display region, thereby preventing display defects such as screen burn-in.

In the above liquid crystal display device, it is preferable that a pretilt angle near the periphery is larger than a pretilt angle in a display area. Further, in the above liquid crystal display device, provided near the periphery of the pair of substrates,
It is desirable to further have an auxiliary electrode for attracting impurity ions in the liquid crystal. The impurity ions are attracted to the auxiliary electrode, and the movement toward the sealing material is promoted.
Therefore, display defects such as screen burn-in can be effectively prevented.

In the above liquid crystal display device, it is further preferable that an AC waveform for vibrating the impurity ions is applied to the auxiliary electrode. Even if the impurity ions are likely to adhere to the liquid crystal molecules and the alignment film, the impurity ions vibrate by the rectangular wave, and therefore can move smoothly without being attached. In the above liquid crystal display device, the auxiliary electrode may be provided near the periphery where a backlight is provided.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] The liquid crystal display according to a first embodiment of the present invention will be explained with reference to FIGS. FIG. 1 is a plan view and a sectional view of the liquid crystal display device according to the present embodiment. FIG. 2 is a cross-sectional view of the liquid crystal display device according to the present embodiment, showing the state of movement of impurity ions.

The liquid crystal display device according to the present embodiment is a TFT liquid crystal display device having 640 × 480 pixels, 10.4 type (26.4 cm diagonal), and provided with a backlight. Pixel electrodes 12 are arranged in a matrix on one substrate 10. Each pixel electrode 12 is provided with a TFT element (not shown), and these TFT elements are commonly connected by a bus line 14. Pixel electrode 12 and T
An alignment film 16 made of polyimide is formed on the FT element in order to arrange the liquid crystal 40.

On the other substrate 20, opposing electrodes 22 opposing a plurality of pixel electrodes 12 arranged on one substrate 10.
Are formed. An alignment film 24 for arranging the liquid crystal 40 is formed on the counter electrode 22 in the same manner as one electrode. Liquid crystal 40 is sealed between the substrate 10 and the substrate 20. As a material of the liquid crystal 40, manufactured by MERCK,
A fluorine-based liquid crystal of model ZLI4792 is used.
As shown in FIG. 1, the periphery of the substrates 10 and 20 is
0 is sealed with a sealing material 30 so as not to leak. As a material of the sealing material 30, XN-21-manufactured by Mitsui Toatsu.
F is used.

In the display area 60, the alignment films 16, 24
Is subjected to an alignment treatment in the same manner as in a normal liquid crystal display device. As the alignment method, a rubbing process generally used is used. In the display region 60 of one alignment film 16, a rubbing process is performed obliquely to the periphery of the substrate 10, as in the rubbing direction 74. In the display region 60 of the other alignment film 24, the rubbing direction 76
The rubbing process is performed so as to intersect with the rubbing direction 74 of one alignment film 16 as viewed from above.

The present embodiment is characterized in the orientation direction of the peripheral region 62. Peripheral edge region 62 of one alignment film 16
In the above, the rubbing process is performed in the vertical direction from the peripheral edge of the substrate 10 toward the inside as in the rubbing direction 70. Similarly, a rubbing process is performed in a vertical direction inward from the periphery of the substrate 20, as in the rubbing direction 72, in the region 62 near the periphery of the other alignment film 24.

As shown in FIG. 2, in the peripheral region 62, the liquid crystal molecules 42 near the alignment film 16 rise along the rubbing direction 70 toward the inside of the liquid crystal display device with respect to the surface of the alignment film 16. It is arranged in. In the peripheral region 62, the liquid crystal molecules 44 near the alignment film 24 are formed.
Are arranged along the rubbing direction 72 so as to rise toward the inside of the liquid crystal display device with respect to the surface of the alignment film 24. Also in the display area 60, liquid crystal molecules (not shown)
Are arranged along the rubbing direction.

The angle at which the liquid crystal molecules rise with respect to the surface of the alignment film is called a pretilt angle. If the pretilt angle is large, the impurity ions can be effectively moved, so that the pretilt angle θ1 of the liquid crystal molecules 42 and the pretilt angle θ2 of the liquid crystal molecules 44 are determined by the pretilt angle of the liquid crystal molecules (not shown) in the display area 60. Desirably larger than the corner.

When the temperature rises due to the heat generated by the backlight or the like, the positively charged impurity ions 5
The impurity ions 52 having 0 or − charge are eluted. The dissolved impurity ions 50 and 52 that are close to the alignment film 16 move along the arrangement of the liquid crystal molecules 42 and return to the sealing material 30. Of the impurity ions 50 and 52, those closer to the alignment film 24 move along the arrangement of the liquid crystal molecules 44 and return to the sealing material 30.

As described above, according to the present embodiment, the impurity ions 50 and 52 that have melted out of the sealing material 30 do not enter the display region 60 and return to the sealing material 30. Therefore, display defects such as screen burn-in can be prevented. In order to confirm the effect of the present embodiment, 50 ° C.
The test pattern shown in FIG.
When a test for displaying time was performed, no display failure occurred. [Second Embodiment] The liquid crystal display according to a second embodiment of the present invention will be explained with reference to FIG. The same components as those of the liquid crystal display device according to the first embodiment shown in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted or simplified.

FIG. 3 is a sectional view showing the structure of the liquid crystal display device according to the present embodiment and the state of movement of impurity ions. The present embodiment is characterized in that an auxiliary electrode 80 and an auxiliary electrode 82 are added near the seal member 30 in addition to the configuration of the first embodiment. The auxiliary electrodes 80 and 82 are provided in the peripheral region 62 near the four sides of the liquid crystal display device. A DC voltage is applied so that the auxiliary electrode 80 is negative and the auxiliary electrode 82 is positive.

When the temperature rises due to the heat generated by the backlight or the like, the positively charged impurity ions 5
The 0 and -charged impurity ions 52 are eluted.
Since the DC voltage is applied to the auxiliary electrodes 80 and 82, the melted impurity ions 50 and 52 are attracted and moved by the auxiliary electrodes 80 and 82, respectively.

The positively charged impurity ions 50 are attracted to the auxiliary electrode 80 which is a negative electrode, and the liquid crystal molecules 42
And returns to the sealing material 30. -The charged impurity ions 52 are attracted to the auxiliary electrode 82, which is a positive electrode, move along the arrangement of the liquid crystal molecules 44, and return to the sealing material 30. A more effective example in the present embodiment will be described with reference to FIG. FIG. 4 is a time chart illustrating a voltage waveform between the auxiliary electrode 80 and the auxiliary electrode 82. The time chart of FIG. 4 shows the voltage applied to the auxiliary electrode 82 when the auxiliary electrode 80 is set to the reference voltage of 0 V. is there.

When the temperature rises due to the heat generated by the backlight or the like, the positively charged impurity ions 5
The 0 and -charged impurity ions 52 are eluted.
The + -charged impurity ions 50 are attracted to the negatively charged auxiliary electrode 80, move along the arrangement of the liquid crystal molecules 42, and return to the sealing material 30. In the process, even if the impurity ions 50 are likely to adhere to the liquid crystal molecules 42 and the alignment film 16, the impurity ions 50 vibrate due to the rectangular wave, and thus move smoothly without being attached.

The charged impurity ions 52 are attracted to the auxiliary electrode 82 which is a positive electrode, and the liquid crystal molecules 44
And returns to the sealing material 30. In the process, even if the impurity ions 52 are likely to adhere to the liquid crystal molecules 44 and the alignment film 24, the impurity ions 50 vibrate due to the rectangular wave, and therefore move smoothly without being attached.

As described above, when the auxiliary electrodes 80 and 82 are provided and a voltage is applied, the movement of the impurity ions 50 and 52 toward the sealing material 30 can be promoted. As described above, it is preferable that the rectangular wave is superimposed on the voltage as compared with the case of only the DC voltage. As described above, according to the present embodiment, the impurity ions 50 and 52 return to the sealant 30 more effectively, and display defects such as screen burn-in can be more effectively prevented.

In order to confirm the effect of this embodiment, the temperature was set to 50 ° C.
The test pattern shown in FIG.
When a test for displaying for 0 hours was performed, no display failure occurred. [Modifications] The present invention can be variously modified irrespective of the above embodiment.

For example, in the first and second embodiments, the rubbing directions 70, 72 are perpendicular to the peripheral edges of the substrates 10, 20, but need not necessarily be perpendicular.
Any direction having a vertical component, such as an oblique direction, may be used.
In the first and second embodiments, the rubbing treatment is performed, but another alignment treatment method such as UV rubbing may be used.

In the second embodiment, a rectangular wave having an amplitude of 5 V is superimposed on a DC voltage of 0.5 V, but another voltage value may be used. As for the waveform, another AC waveform such as a sine wave may be used as long as the impurity ions 50 and 52 can be vibrated. In addition, the position where the auxiliary electrodes 80 and 82 are provided may be only one side near the backlight where the temperature is particularly high, in the peripheral edge region 62. In order to confirm that the provision of the auxiliary electrodes 80 and 82 on one side was sufficient, a test was performed in which the test pattern shown in FIG. Did not occur.

[0031]

As described above, according to the present invention, the alignment film in the vicinity of the periphery of the pair of substrates is subjected to the orientation treatment having a component perpendicular to the periphery and inward from the periphery. Therefore, it is possible to prevent impurity ions from penetrating into the display region and prevent display defects such as screen burn-in.

[Brief description of the drawings]

FIG. 1 is a view showing a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a movement state of impurity ions in the liquid crystal display according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a liquid crystal display according to a second embodiment of the present invention.

FIG. 4 is a time chart showing an applied voltage waveform of a liquid crystal display according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a test pattern displayed on a liquid crystal display device.

FIG. 6 is a sectional view showing a proposed liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Substrate 12 ... Pixel electrode 14 ... Bus line 16 ... Alignment film 20 ... Substrate 22 ... Counter electrode 24 ... Alignment film 30 ... Sealing material 40 ... Liquid crystal 42, 44 ... Liquid crystal molecule 50, 52 ... Impurity ion 60 ... Display area 62 ... Region vicinity area 70, 72, 74, 76 ... Rubbing direction 80, 82 ... Auxiliary electrode θ1, θ2 ... Pretilt angle 110 ... Substrate 112 ... Pixel electrode 114 ... Bus line 116 ... Alignment film 120 ... Substrate 122 ... Counter electrode 124 ... Alignment film 130 Sealing material 140 Liquid crystal 150, 152 Impurity ions 160 Display area 162 Peripheral area 180, 182 Auxiliary electrode

Continued on the front page (72) Takashi Sasabayashi 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Takemune Mayama 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture No. 1 Inside Fujitsu Limited

Claims (5)

[Claims] 1. A pair of substrates disposed to face each other, a liquid crystal sealed between the pair of substrates, a sealant sealing a periphery of the pair of substrates, and a pair of substrates provided on the pair of substrates. In the liquid crystal display device having an alignment film, the alignment film in the vicinity of the periphery of the pair of substrates has a component perpendicular to the periphery, and is subjected to an alignment process in a direction inward from the periphery. A liquid crystal display device. 2. The liquid crystal display device according to claim 1, wherein a pretilt angle near the periphery is larger than a pretilt angle in a display area. 3. The liquid crystal display device according to claim 1, further comprising: an auxiliary electrode provided near the periphery of the pair of substrates and for attracting impurity ions in the liquid crystal. Display device. 4. The liquid crystal display device according to claim 3, wherein an AC waveform for oscillating the impurity ions is applied to the auxiliary electrode. 5. The liquid crystal display device according to claim 3, wherein the auxiliary electrode is provided near a periphery where a backlight is provided.