JPS62183430A - Production of liquid crystal display panel - Google Patents

Abstract

PURPOSE:To control generating of triboelectrification charge and to lessen an electrostatic breaking of TFT by selecting a material having a near value of the electrostatic ability for a constituting material of the orientation film based on the electrification rank as a rubbing material used in rubbing. CONSTITUTION:In the display panel of an active matrix type, when carrying out an orientation treatment by rubbing a horizontal orientation film formed on a display electrode, as the rubbing material used in rubbing, the material having a near value of the electrostatic ability for the constituting material of the orientation film is selected based on the electrification rank. The rubbing is carried out by using a fiber composed of the prescribed material. The charging voltage can be depressed by selecting a roll material from the material having the near value of the electrostatic ability of the orientation film in rubbing the orientation film. Thus, the electrostatic breaking of TFT is lessened.

Description

[Detailed Description of the Invention] [1 Already Required] The amount of static electricity generated can be reduced by using a material used for rubbing the alignment film that has a charging ability close to that of the alignment material from the charging series. Processing method to prevent electrostatic damage to transistors.

[Industrial application field]

The present invention relates to a treatment method for preventing electrostatic damage that occurs during rubbing treatment.

There are two types of liquid crystal display devices: active matrix type and simple matrix type.

Comparing the characteristics of the two, the active matrix type can drive a large number of pixels independently, so even if the number of lines increases as the display capacity increases, the driving duty ratio is lower than that of the simple matrix type. However, problems such as a decrease in contrast and a decrease in viewing angle do not occur.

However, since a switching element is provided for each pixel, the cost tends to be high, and since all switching elements must be of good quality, there is a problem with manufacturing yield, and the size of the panel is limited due to this. There is a problem.

The present invention relates to an improvement in the rubbing treatment method which constitutes one of the causes of the reduction in manufacturing yield of such active matrix type display panels.

[Conventional technology]

Liquid crystals used as display materials in liquid crystal displays include those with horizontal alignment and those with vertical alignment.

For example, cyano Schiff base, cyano ester, azoxy, etc. are materials that exhibit horizontal orientation, and cyanobiphenyl,
A Schiff base is a material that exhibits vertical alignment.

However, since the orientation of liquid crystal molecules depends on the type of substrate material and its surface condition, it is necessary to provide an insulating alignment film on the electrode substrate to help align the liquid crystal. ing.

The present invention relates to a method for horizontally aligning liquid crystal in a direction parallel to a substrate.
After forming an alignment film by obliquely depositing a material such as n) or forming an alignment film of polyvinyl alcohol (abbreviated as Pv^) or polyimide, a rubbing process is performed to align the liquid crystals in the alignment direction.

For example, twisted nematic effect (Twisted Nematic effect)
To explain the role of an alignment film in a TN display using a ticEffect method, first, two glass substrates with an electrode pattern made of a transparent conductive film are provided with a horizontal alignment film and then rubbed. The glass substrates are arranged facing each other with their rubbing directions perpendicular to each other, and a liquid crystal exhibiting horizontal alignment is sealed between them.

In this state, the liquid crystal molecules are arranged in a continuous 90° direction between the upper and lower electrode patterns.

Next, if a polarizing plate is set so that the vibration directions of the light transmitted to both the upper and lower sides of the glass substrate are perpendicular to each other, the light polarized by the upper polarizing plate will be twisted when no voltage is applied between the upper and lower electrode patterns. The light transmits along the liquid crystal molecules arranged in the same direction, and passes through the lower polarizing plate. However, when a voltage is applied and the liquid crystal aligns in the direction of the electric field, the light loses optical rotation, so the light passes through the lower polarizing plate. This phenomenon is used to display TN.

As described above, it is necessary that the liquid crystals are correctly aligned in a prescribed direction along the alignment film, and those using a horizontal alignment film such as PVA or polyimide are subjected to a rubbing treatment.

However, in the past, not much attention was paid to the rubbing roll material used for this purpose, and as a result, static electricity was generated during the rubbing process, which could destroy thin film transistors (hereinafter referred to as TPT), which was a major problem. It became.

FIG. 2 is a partial cross-sectional view of an active matrix type liquid crystal display panel, showing the relationship between the TFTl and the alignment film 2. As shown in FIG.

That is, a conductive film (hereinafter abbreviated as ITO film) 4 made of a solid solution of indium oxide (InzO:l) and tin oxide (SnO) is used to display pixels on a glass substrate 3 having a thickness of about one cage. An electrode is patterned, and one end of this display electrode is formed on the glass substrate 3. T
The circuit is connected to the source electrode 5 of No. 1.

Here, the TFT 1 is made of silicon nitride (Si) on the gate electrode 6.
There is a drain electrode 7 and a source electrode 5 separated by an amorphous silicon (a-3i) layer and an amorphous silicon (a-3i) layer, and a light shielding film 8 is formed thereon with an insulating film such as polyimide interposed therebetween.

The gate electrode 6 is connected to the gate pass line, and the drain electrode 7 is connected to the drain pass line.

The TFTs 1 having such a structure are arranged for each pixel, and an alignment film 2 is provided on the ITO film 4.
Rubbing treatment has been applied.

The counter electrode shown in FIG. 2 consists of only the ITO film 4, on which the alignment film 2 is formed and rubbed, and then the two substrates are made to face each other and the liquid crystal 9 is sealed between them. Take.

In such a display panel, high-voltage static electricity is generated during the rubbing process of the alignment film 2, and discharge occurs between the drain electrode 7 and the gate electrode 6, causing electrostatic damage to the TFT 1, which is a problem, and a solution to this problem is desired. was.

[Problem that the invention seeks to solve]

When forming an active matrix type display panel, high-voltage static electricity is generated due to frictional electrification when the alignment film is rubbed for alignment treatment, which causes destruction of the TPT, which is a problem.

[Means for solving problems]

The purpose of the above is to align the horizontal alignment film formed on the display electrode in an active matrix display panel by rubbing, and the rubbing material used for the rubbing should be selected from the charging series so that the charging ability is close to that of the alignment film constituent materials. This problem can be solved by a method for manufacturing a liquid crystal display panel, which involves selecting a material that has been prepared and using fibers made of the material.

[Effect]

The static electricity generated when rubbing the alignment film is caused by frictional charging between the alignment film forming material and the rubbing material, and the voltage is determined by the materials used.
The inventors have found that this potential difference corresponds to a so-called charge series.

FIG. 1 shows one of the charge series known in electrostatic engineering.

(G, S, Rose + S, G, W
ard: Brlt, J, 8pp1. Phys)
In other words, when rubbing glass and Teflon, the glass is just 1 and the Teflon is 1! This shows that it is charged to t and generates a higher voltage than other combinations.

The inventors measured the surface potential of the PVA film after rubbing using PvA as an alignment film and using various rubbing roll materials (hereinafter referred to as roll materials for short), and also when using nylon and polyethylene as roll materials. The electrostatic breakdown rate of T II 'r was also measured.

The table shows the results of this measurement.

Here, the surface potential was measured without contact using a vibrating capacitance electrometer (manufactured by Tageda Riken).

The rotation speed of the rubbing roll during the rubbing process was 500 rpm.

Table 1 From this table, it can be seen that the combination of PvA and nylon has the highest surface potential, and the combination of PVA and polyethylene has the lowest surface potential, but this also affects the electrostatic breakdown rate of TPT. Correctly handled.

Further, the order of the surface potentials in the table is the same as the charging sequence shown in FIG.

Therefore, the present invention makes it possible to lower the charging voltage by selecting a roll material close to the charging ability of the alignment film when rubbing the alignment film, thereby eliminating electrostatic damage to the TPT.

〔Example〕

As mentioned earlier, organic compounds such as PvA and polyimide are often used as horizontal alignment films for liquid crystal display panels, but organic compounds such as silicon dioxide (SiOz), tungsten oxide (WO2), and cerium oxide (CaO2) are often used. Inorganic compounds have also been used.

The case where a SiO2 film is used as the alignment film will be described below.

A display electrode made of a transparent conductive film made of an ITO film was patterned and a SiO□ forming solution (concentration 5) was placed on a glass substrate.
．． 9%, trade name OCD, manufactured by Tokyo Ohka Kogyo) at 30 rotations.
After spin coding under 0Orpm conditions, 1
By heating over a period of time, an alignment film made of Sing was formed.

Next, the alignment film was rubbed using glass, nylon, polyethylene, and Teflon fibers as rubbing materials, and its surface potential was measured.

Note that the rubbing conditions are that the roll rotation speed is 500 rpm and the number of times of rubbing treatment is 10 times.

Table 2 shows the results.

Table 2 From the results, it was found that glass fiber or nylon fiber was used as the roll material (in fact, no electrostatic damage occurred in TPT).

It can be seen that this order of surface potentials matches the charge series shown in FIG.

Next, similar results were obtained when the method was applied to an alignment film made of WO3 or CeO□.

〔Effect of the invention〕

As explained above, the present invention uses fibers made of materials that are close to the orientation material in the charging series when performing the rubbing process, and by implementing the present invention, the amount of triboelectric charges generated can be suppressed, and this This makes it possible to eliminate electrostatic damage to the TI'T.

[Brief explanation of drawings]

FIG. 1 is a charged array, and FIG. 2 is a partial cross-sectional view of an active matrix liquid crystal display panel. In the figure, 1 is TPT, 2 is an alignment film, 5 is a source electrode, 6 is a gate electrode, 7 is a drain electrode,
9 is a liquid crystal.

Claims (1)

[Claims] When aligning the horizontal alignment film formed on the display electrode in an active matrix display panel by rubbing, the rubbing material used for the rubbing is selected from a charging series with a material that has a charging ability close to that of the alignment film constituent material. A method for manufacturing a liquid crystal display panel, characterized in that it is carried out using fibers made of the material.