JPS6293974A - Thin film transistor array - Google Patents

Abstract

PURPOSE:To realize a large area display efficiently by composing a substrate of a polyimide film whose main component is polyimide with a repeated unit expressed by predetermined general formulae. CONSTITUTION:A gate electrode 3, a gate insulating film 4, a semiconductor layer 5, a source electrode 6 and a drain electrode 7 are formed on a substrate 2 in a thin film transistor array 1. A colorless transparent light transmitting polyimide film is employed as the substrate 2. The main component of the film is polyimide which has a repeated unit expressed by a general formula I and/or a general formula II, wherein X1 in the formula I denotes O, SO2, CH2 or CO and X2 in the formula II denotes SO2, C(CH3)2 or C(CF3)2. With this thin transistor array, a liquid crystal display panel with a concave display plane and with reduced reflected light can be obtained.

Description

Detailed description of the invention (a) Industrial application field The present invention uses a colorless and transparent polyimide film as a substrate,
The present invention relates to a thin film transnostar array that is used as a switching element in a liquid crystal display panel that can be curved and have a large area, and can be light-layered, thin, and continuously produced.

(b) Conventional technology In recent years, a large number of gate lines (scanning lines) and drain lines (signal lines) are formed on a transparent substrate, which is one of the substrates of a liquid crystal display panel, and are insulated from each other. A thin film transnostar (hereinafter abbreviated as TPT) is provided as a switching element at the intersection of each line, and this is driven to open and close to give a symbol to the display electrode arranged at each intersection.
A so-called active matrix type liquid crystal display panel, which displays images on a television or the like by driving the liquid crystal in this part, is being developed.

For example, a TFT array for driving a liquid crystal display that uses a quartz glass plate as a transparent substrate and a polycrystalline silicon TPT formed thereon, and a TPT7 array that uses a glass plate as a substrate and forms an amorphous silicon TPT have been put into practical use. .

Liquid crystal display panels using these TPT arrays are l
! Compared to diode i-tubes, it has many advantages in terms of drive voltage, power consumption, weight, and miniaturization, and is expected to be widely popular.

(c) Problems to be Solved by the Invention Incidentally, TFT arrays using these quartz glass plates or glass plates as substrates have various drawbacks.

In other words, quartz glass is advantageous in that it has excellent heat resistance and is less likely to cause contamination problems, but on the other hand, it is difficult to manufacture large-area displays or attach multiple surfaces to a single substrate. Increasing the area of the board, which is essential for cost reduction through rationalization of processing, etc., requires extremely high cost I! There is a topic J.

In addition, glass substrates do not have any cost problems when increasing in area, but they have a common drawback with quartz glass: their surfaces are generally flat, so the display surface of liquid crystal display panels that use these TFT arrays is The problem is that it is difficult to curve the surface.

The shape of the display surface has been studied from the viewpoint of improving visibility by reducing glare caused by reflection of external light.

As the display surface changes from a convex shape (such as the display surface of a cathode ray tube) to a flat shape (such as the display surface of a glass substrate display panel) and then to a concave shape, the angle at which outside light is taken in decreases, and the amount of reflected light that enters clothing decreases. do.

Of course, it is technically possible to curve a glass plate, but it is more expensive than a flat one, and the photolithography process requires highly sophisticated technology. .

As display devices have become widely used in general applications, further improvements in fatigue prevention are desired, and thin film transistor arrays, which are their constituent parts, are also required to be improved.

On the other hand, general-purpose products that require simplicity, such as LCD pocket color televisions, make the most of the characteristics of liquid crystal display panels, and are particularly required to be lightweight and thin, as well as to reduce costs through continuous production.

By the way, in the production of the TFT 7, almost all manufacturing steps such as the gate electrode, insulating film, amorphous silicon film, source electrode, and one drain electrode are processed in a vacuum atmosphere.

However, if the substrate is a short substrate such as a glass plate, continuous processing in the above steps is extremely difficult.

(d) Means for solving the problem The inventors of the present invention have conducted intensive studies to solve the problems of TFT arrays using glass as a substrate. Gamo developed a colorless and transparent polyimide film and used it as a substrate for TF.
They succeeded in manufacturing a T-array and completed the present invention.

That is, the present invention provides a TFT array (or thin film diode array) for a liquid crystal display panel on which liquid crystal is driven for display on a substrate, and the substrate is a polyimide film mainly composed of polyimide having repeating lli positions represented by the general formula. It is characterized by being formed of.

The present invention will be explained in detail below.

In the present invention, as a thin film transistor array? positive game −
卜 1 cup l）
There is no particular limitation as long as the display device is provided with a drain electrode.

A feature of the present invention is that a colorless and transparent light-transmitting polyimide film is used as the substrate.

Colorless and transparent means that the visible light (500n ring) transmittance for a polyimide film with a thickness of 50±5 μm is 70% or more, and the yellowness index is 40 or less. .

Although polyimide film is heat resistant, there has never been a colorless and transparent polyimide film, and this film was completed as a result of research by the present inventors.

The colorless and transparent polyimide film used in the present invention is formed of a polyimide film containing as a main component a polyimide having repeated li positions represented by the general formula.

The colorless and transparent polyimide used in the present invention has the general formula (
Ill) Biphenyltetracarboxylic dianhydride represented by general formulas (IV) and (V) In formulas (■) and (V), Xl and X2 are represented by formula (1)
, as shown in (II).

can be obtained by reaction with an aromatic noamino compound represented by

As the biphenyltetracarboxylic dianhydride, the following 3.3',4.4'-biphenyltetracarboxylic dianhydride and 2.3.3',4'-biphenyltetracarboxylic dianhydride are used. Can be mentioned.

Further, among the 10,000Ff ecchinoamino compounds having an amine 7 group at the meta position, the following are representative examples of the aromatic S group dinuclear diamine represented by the general formula (IV).

3.3'-Noaminonophenyl ether 3.3'-Noaminodiphenylsulfone 393'-Noaminonophenylthioether 3.3'-Diaminonophenylmethane 3.3'-Diaminobenzophenone Also, aromatic tetranuclear substance Representative examples of noamines include the following.

4.4'-No(3-amino/7eth/xy)nophenylsulfone CH.

4.4'-di(3-7mino7e/xy)diphenylpropane CF.

4.4'-no(3-aminophenoxy)diphenylhexafluoropropane (r3,3'-BA
(abbreviated as PFJ) The above-mentioned aromatic dinuclear noamine and aromatic tetranuclear noamine may be used alone or in appropriate combinations.

A biphenyltetracarboxylic dianhydride as described above and an aromatic dinuclear diamine having 7 amide groups at the meta position and/or
Alternatively, by combining it with an aromatic tetranuclear noamine, a colorless and transparent polyimide whose main component is a repeating unit represented by the above general formula (1) and/or (n) can be obtained.

Here, the term "main component" is meant to include cases where the entire composition consists only of the above general formula (r) and/or (II).

In this case, the content of the polyimide represented by the repeating unit represented by the above general formula (1) and/or the repeating unit represented by the above general formula (II) is high in the polyimide thus obtained. The colorless transparency of the polyimide film obtained increases as the temperature increases. However, the above general formula (
If the polyimide of the repeating unit represented by 1) and/or the repeating unit represented by the general formula (ff) is contained in an amount of 70 mol% or more, at least the colorless transparency required by this invention is ensured, so it is within that range. In this method, an aromatic tetracarboxylic dianhydride other than the above-mentioned biphenyltetracarboxylic dianhydride and a non-amateur compound other than the aromatic dinuclear/tetranuclear diamine having a 7-mino group at the meta position are used. be able to.

That is, the preferred range of the polyimide represented by the repeating unit represented by the general formula (1) and/or the repeating unit 'r represented by the general formula (II) is 70 mol% or more, and the most preferred range is 95% by mole or more. It is mol% or more.

Examples of the above-mentioned other aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride, 3,3 +4+4-benzophenonetetracarboxylic dianhydride, 4゜4'-oxyno7talic dianhydride, 4 .4-bis(3,4-nocarboxy7-/xy)diphenylsulfone dianhydride, 2.2-
Bis(3,4-dicarboxyphenyl)hexafluoropropanide anhydride, 2,3,6.7-7talentetracarboxylic dianhydride, 1.2.5.6-7talentetracarboxylic acid Examples include dianhydride, 1.4.5.8-su7talentetracarboxylic dianhydride, and these can be used alone or in combination.

In addition, other Noamitsu compounds include 4゜4゛-Noaminodiphenyl ether, 3.4'-diaminodiphenyl ether, 4,4゛-Noaminophenyl sulfone, 4.4'-Noaminodiphenyl IF, 4.
4'-Diaminobenzo7ene, 4.4'-E/ami7diphenylpropane, paraphenylene77mine, metaphenylenediamine, benzinone, 3.3'-dimethylbenzinone, 4.4'-diaminodiphenyl thioether, 3.3'-dimethoxy-4,4'-noami/nophenylmethane, 3.3'-tumethyl-, i,4'-
Noami/No7-Dylmethane, 2,2-bis(4-amino/phenyl)propane, 2,2-bis(4-(4-aminophenoxy)phenyl]-hexafluoropropane, 1,3-bis(amino) (phenoxy)benzene, which can be used alone or in combination.

The colorless and transparent polyimide film used in the present invention can be produced by polymerizing the above-mentioned aromatic tetracarboxylic dianhydride and diamide/compound in an organic polar solvent at a temperature of 80' (: A body solution is prepared, and a molded body of a desired shape is formed using a method such as casting or roll coating using this polyimide precursor melt,
This excipient is placed in air or in an inert gas at a temperature of:
It is obtained by evaporating and removing the organic polar solvent under normal pressure or reduced pressure and simultaneously dehydrating and ring-closing the polyimide precursor.

Alternatively, instead of the above method, the polyimide precursor may be desolventized and imidized using a benzene solution of pyridine and acetic anhydride, etc., and converted into polyimide. can.

-''2 organic polar solvents include dimethylformamide, dimethylacetamide, noblime, cresol,
Halogenated phenols and the like are preferred, and trimethylacetamide is particularly preferred since it is a good solvent and has an extremely low boiling point. These organic polar solvents may be used alone, or two or more of them may be polymerized and used without any problem.

As an organic polar solvent, each of the above-mentioned soluges L has a low boiling point, so when dehydrating and ring-closing by heating, the decomposition product remains in the polyimide and the polyimide becomes colored. It does not occur.

However, using a high-boiling, solid polymerization solvent such as N-methyl-2-pyrrolidone, after synthesizing the polyimide 11if precursor, it is possible to dissolve the produced polyimide precursor in the preferred i3 vL as exemplified above by solvent displacement. This will eliminate the above disadvantages. In this case, the suitable solvent exemplified above is a diluting solvent. In producing the above polyimide film, the polymerization solvent and the diluting solvent may be of different types as described above, and the polyimide I precursor produced may be dissolved in the diluting solvent by dissolution VL substitution.

In addition, when using the suitable organic polar solvents exemplified above, solvents such as ethanol, toluene, benzene, quinolene, dioxane, tetrahydrofuran, and nitrobenzene may be added to this solvent to impair the colorless transparency of the polyimide film. Two or more types may be appropriately mixed and used within the range of 1.I'Il.

Logarithmic viscosity of the polyimide surface precursor solution (measured at 30°C at a concentration of 0.58/100+nN in N-methyl-2-pyrrolidone solvent) when producing a colorless R-light polyimide film as described in ``2. It is preferable to adjust it so that it is in the range of 0.3 to 5.0.

More preferred is 0.4 to 2.0. If the logarithmic viscosity is too low, the resulting polyimide film will have a low contract strength, which is not preferable. On the other hand, if the logarithmic viscosity is too high, it becomes difficult to flow the polyimide precursor liquid when shaping it into an appropriate shape, which is not preferable. In addition, the concentration of the poly(mide precursor solution)
From the viewpoint of workability, etc., 5 to 30% by weight, preferably 15
It is desirable to set the weight to -25 weight f6.

In addition, -F written number viscosity is calculated by the following formula,
The viscosity in the formula is measured using a capillary viscometer.

To obtain a polyimide 1/film with excellent colorless transparency using a polyimide precursor solution, the polyimide precursor solution is cast onto a mirror surface such as a plastic plate or a stainless steel plate to a certain thickness. This is carried out by gradually heating to a temperature of 0.degree. C. to cause dehydration and ring closure, and then imidizing the polyimide precursor. Polyimide precursor; For polyimide film formation from 8 liquids (i b'l
The heating for removing the polar solvent and imidizing the polyimide precursor may be carried out continuously, or these steps may be carried out under reduced pressure or in an inert bath atmosphere. If so, the properties of the resulting polyimide film can be improved by finally heating it to around 400°C.

In addition, Ike's method for forming a polyimide film involves casting the above polyimide precursor solution onto a plastic plate, etc.
A film is formed by heating and drying at 150°C for 30 to 120 minutes, and this film is immersed in a benzene solution of pyridine and acetic anhydride to remove the solvent and undergo an imidization reaction, thereby converting the film into a polyimide film. A colorless and transparent polyimide film can also be obtained by this method.

The thickness of the polyimide film thus obtained is preferably set to about 7 to 550 μm. If the thickness exceeds 550 μm, the light transmittance will deteriorate and the flexibility will be lacking, making it difficult to continuously wind the film into a roll, which will cause problems in productivity. If it is less than 7 μu+, sufficient mechanical strength will not be obtained and the temperature (25
It is not preferable because it cannot withstand temperatures (0° C. to 350° C.) and the substrate may be deformed by this thermal stress.

This polyimide film is colorless and transparent and is not colored yellow or yellowish brown as in conventional films, so it has extremely good colorless transparency even if it is a relatively thick film.

In the case where the polyimide precursor solution is imidized to form polyimide as described above, the generated polyimide is
From the point of view of properties, logarithmic viscosity (0.5.7 d in 97 wt 1% sulfuric acid)
(measured at a temperature of 30° C. at a concentration of 1 ml) is preferably set within the range of 0.3 to 5.0. Most preferred is 0.4
~4.0.

The polyimide film obtained in this manner is completely different from conventional films, and is colorless and transparent, and has extremely high transparency.

In particular, aromatic dinuclear noamines and aromatic tetranuclear diamines represented by general formulas (IV) and (V) have excellent colorless transparency and are most suitable for the substrate used in the present invention.
In this example, x+ and X2 are S02. The polyimide film obtained using this material is
Not only is it extremely colorless and transparent, but it also has excellent heat resistance and a low heat shrinkage rate.

TF was placed on the polyimide film substrate thus obtained.
Form a T array.

Formation of a TFT array on a substrate is performed, for example, as follows.

Figure 1 shows a staggered TFT array (1).
T array (1) is configured as follows.

In FIG. 1, a transparent conductive material such as ITO or chromium, -[:1
A gate electrode (3) is formed of a conductive material such as 77' metal, aluminum, nickel, or chromium.

Next, SiO□, 8120. Alternatively, the insulating film (4) is formed of an insulating material such as SixNy.

To form this insulating film (.t), a method such as a vapor deposition method, a sputtering method, a plasma CVD method, or the like is appropriately selected.

Thereafter, a semiconductor layer (5) made of amorphous silicon is formed by plasma CVD and photolithography.

Furthermore, in order to form a source electrode and a drain electrode, 11'OJr! I, aluminum layer, etc. are stacked 11 times, and a source electrode (6) and a drain electrode ff1 (7) are provided from this layer.

Thereafter, an ITO layer is deposited on 11 by vapor deposition or sputtering to form a display electrode, and the display electrode is fabricated by 7-otolithography to complete the TFT array.

In forming the TFT array according to the present invention, when selecting the method for forming the above-mentioned thin films for forming electrodes, the amorphous silicon RG film, and the insulating film, the heat resistant temperature (300°C) of the transparent polyimide substrate is considered. Thinking! Determined by

Further, the deposition of each thin film and pattern processing by 7 otolithography or the like can be performed continuously by winding the substrate into a roll.

The above-mentioned TFT array can be fabricated using a staggered structure whose cross section (portion) is shown in FIG. 1, a staggered structure shown in FIG. 2, and a staggered structure shown in FIGS. This includes those with a coplanar structure.

In manufacturing the one-film transistor array of the present invention,
In the process of forming each thin film layer, 7-otolithography, etc., it is possible to flatten the surface and perform various treatments in the same manner as when handling a glass substrate. Additionally, since it is possible to create a moderately curved display surface (Kamabot type) by reducing the curvature when assembling the liquid crystal display panel, it is possible to reduce the above-mentioned reflected light to the worker. It is.

(e) A TFT is installed on a flat, short substrate such as an action-plus machine.
For FT arrays, when used for manufacturing liquid crystal display panels,
The display surface becomes flat, and there is a limit to how much reflected light can be reduced by reducing the external light intake angle.

Further, in manufacturing the amorphous silicon layer and the thin films for forming each electrode, processing is performed in a vacuum atmosphere, but because of the short length, continuous production, which is advantageous for cost reduction, is difficult.

In the case of a TFT array using a colorless polyimide film as a substrate according to the present invention, the liquid crystal display surface is moderately curved by combining the transparent conductive film on the back side of the liquid crystal J[・1 and (11). It is possible to manufacture display panels and has the effect of significantly reducing the risk of reflection.

In addition, in most production processes, there is Melia F, in which the substrate is turned into a roll and processed continuously, but particularly high productivity is required for amorphous silicon thin films, thin films for each electrode type, and one member for each electrode type. In the step of depositing an insulating film in a vacuum atmosphere, the substrate is held in a roll in the same chamber, and thin films can be continuously formed.

In addition, similar to the conventional TF'T array that uses a glass plate as a substrate, by combining it with an appropriate color filter,
It has a full color display that can be used for one purpose.

(f) Example ■ Production of a colorless and transparent polyimide film Using trimethylacetamide as a solvent,
3.3',,i for Yonisluaon1 alo12
, 4'-biphenyltetracarboxylic dianhydride I
Qof! The reaction was carried out to obtain a solution of polyimide J precursor.

This solution was cast on a glass plate to form a film, this film was dried with hot air, and finally heated at 300°C for 5 hours to complete the imidization reaction, and a 50μm polyimide film was formed. Obtained.

Light FA transmittance of this film (wave v<500 nm1l
The surface roughness is 30 on both sides, and the temperature is 35.
The heat shrinkage rate at 0°C was 2% or less.

(2) Production Example of T'T array As the substrate (2), the colorless and transparent polyimide film obtained in (2) above and having a thickness of 5 () μm was used.

After depositing 2,000 chrome films on one side of this film by vapor deposition at a substrate temperature of 250'C,
A gate electrode (3) was formed by patterning using photolithography.

An absolute AM consisting of silicon nitride S i3N with a thickness of 2,000 people over the entire surface! II;!
(4) was provided by plasma CVD method.

Conditions Ii for CVD using a bra: Substrate temperature 2 SO”C
1. Silane diluted to 10 mol% with hydrogen was used as the raw material gas, and the flow rate was 2008 CCM and 100% nitrogen XX10.
05CC, pressure I Torr, high frequency power density I W
att/c+a2.

After that, supply of raw material gas, discharge, and heating of the substrate are stopped, and l Q O! >6 Hydrogen flows [2 plasma] After completely replacing the gas in the CVD equipment, the same plasma C
In the VD device, thickness 2 + 500 people /
Semiconductor layer (5) made of undoped amorphous silicon
was deposited.

The conditions are as follows: the substrate temperature is 250'C, Fy, silane diluted by 10 mol% is used as the source gas, and the flow ht is 250'C.
0 +'l S CCM, pressure 0.2 Torr, high frequency power density 0, I W act/cn-.

Next, an amorphous silicon pattern was formed in the trannostar-shaped hollow region using a 71 trinography.

Thereafter, 11 aluminum films having a thickness of 3,000 wafers were selectively stacked using the sub-lid method to form a source electrode (6) and a drain electrode (7).

Furthermore, ITOlli was selectively deposited to a thickness of 300 by sputtering to form a 7r1 electrode for display.

111i of aluminum film and ITO film by sputtering
In the case of the product as well, the substrate temperature was set not to exceed 250°C.

The thus obtained thin film transistor array was comparable in weight to one using a quartz lath plate as a substrate, and was lighter in weight.

(8) Effects of the Invention The TFT array of the present invention makes it possible to manufacture a flexible TFT array by using a colorless and transparent polyimide film on its substrate, and the liquid crystal and the transparent conductive film on the back side By combining them, the user can produce a liquid crystal display panel with a concave display surface and reduced reflected light.

In addition, since the substrate is rolled into a roll and subjected to the manufacturing process continuously, continuous production is possible.
Production costs can be significantly reduced.

Furthermore, since it is lightweight and thin, it has the advantage that it is possible to easily manufacture a TFT array for liquid crystal display, which is suitable for application to portable devices.

Furthermore, a film made by pasting together scraps such as a substrate, a transparent conductive film, and a liquid crystal can be used by overlaying a suitably curved shaped panel made of acrylic resin, etc., which is extremely useful. .

[Brief explanation of drawings]

1 to 4 are enlarged sectional views of essential parts of a thin film trannostar array to which the present invention can be applied. (1)... Thin film transnostar array, (2)... Substrate, (3)... Data? ■【Koku, (4)...
-Insulating film, (5)...semiconductor layer, (6)...source electrode, (7)...drain electrode. No. 1 (branch) 4-JL Honto 5, -411 Figure 2 Figure 3 Procedure amendment (voluntary) November 10, 1985

Claims (1)

[Claims] In a thin film transistor array in which a gate electrode, a gate insulating film, a semiconductor layer, and a source/drain electrode are provided on a substrate, the substrate has a general formula▲a mathematical formula, a chemical formula, a table, etc.▼-(I) and/or ▲There are mathematical formulas, chemical formulas, tables, etc.▼-(II) [However, in formula (I), X_1 is O, SO_2,
CH_2 or CO, and in formula (II), X_2 is SO_2, C(CH_3)_2 or C(CF_3)_2
It is. ] A thin film transistor array characterized in that it is formed of a polyimide film mainly composed of polyimide having repeating units represented by the following.