JPH0470818A - Highly dielectric film, formation thereof and liquid crystal display panel using the same - Google Patents

Abstract

PURPOSE:To obtain a highly dielectric film having a high dielectric constant and liq. crystal orienting function by mixing a polyimide type polymer with ceramics having a higher dielectric constant than the polymer. CONSTITUTION:A polyimide type polymer, e.g., polyimide is mixed with about 20-50vol.% ceramics having a higher dielectric constant than the polymer, e.g., Al2O3, PZT [zirconium lead titanate, Pb(Zr-Ti)O3] or PLZT [lanthanum zirconium lead titanate, Pb(La-Zr-Ti)O3] and the mixture is used to obtain a highly dielectric film having 5.0-7.0 dielectric constant epsilon and liq. crystal molecule orienting function. This film is formed as follows: the constituents of polyimide and about 20-50vol.% ceramics are stuck on a substrate by vacuum deposition, sputtering or other method in a mixed state or a soln. of a precursor of polyimide (polyamic acid) is mixed with about 20-50vol.% ceramic powder, a substrate is coated with the resulting paste by spin coating, printing or other method and the paste is fired by heating.

Description

[Detailed Description of the Invention] [Summary] Regarding a high dielectric film, a method for forming the same, and a liquid crystal display panel using the high dielectric film, the present invention relates to a high dielectric film having a high dielectric constant and a liquid crystal alignment function. The purpose of the present invention is to reduce the influence of the film thickness distribution of the alignment film on the threshold voltage and to reduce display unevenness by using the film, its formation method, and its highly dielectric film as the alignment film of a liquid crystal display panel. , a high dielectric film is formed by mixing a polyimide polymer material with ceramics having a higher dielectric constant than the polymer material.

Alternatively, a polyimide polymer material and a ceramic having a higher dielectric constant than the polymer material are mixed and formed into a film by a thin film forming method such as vacuum evaporation or sputtering, and the The structure is such that a highly dielectric film containing ceramics is formed.

Further, a ceramic powder having a higher dielectric constant than the polyimide polymer material is mixed with the polyimide polymer material, and the mixed composite material is formed into a film by a thick film forming method to form a highly dielectric film. .

Furthermore, in a liquid crystal display panel having a structure in which a pair of substrates each having a transparent electrode for display covered with an alignment film for controlling the alignment of liquid crystal on the inner surface are arranged facing each other with the liquid crystal in between, the alignment film is made of polyimide. It has a two-layer film structure consisting of a highly dielectric film in which the ceramics are mixed into a polymer film, or a thin film with high dielectric properties, and a thin polyimide polymer film laminated thereon.

[Industrial application field]

The present invention relates to a highly dielectric film, a method for forming the same, and a liquid crystal display panel using the highly dielectric film as an alignment film that regulates the alignment of liquid crystals.

Liquid crystal display panels used in various display devices or input/output devices with display sections, especially STN (Sup
In liquid crystal display panels of the er Tivisted Nen+atic) type, it is a major challenge to make the display quality uniform by using an alignment film that has a high ability to regulate the alignment of liquid crystals.

[Conventional technology]

As shown in FIG. 7, a conventional liquid crystal display panel has transparent display electrodes 3.4 on the inner surfaces of a pair of glass substrates 1.2, respectively.
The transparent electrodes 3 and 4 are coated with an alignment film 5.6 made of a polyimide polymer material that regulates the alignment of the liquid crystal, and the surfaces of the alignment films 5 and 6 are subjected to a rubbing treatment. is applied. The pair of glass substrates 1 and 2 having the above-described structure are arranged to face each other with a liquid crystal 8 interposed therebetween, with a spacer 7 regulating the distance between the substrates interposed therebetween.

The above-mentioned alignment film 5 (6) is formed by applying a polyimide precursor solution, that is, polyamic acid, onto the glass substrate 1 (2) on which the transparent electrode 3 (4) is disposed, by a spin code method, a printing method, or the like. An alignment film made of polyimide is formed by uniformly applying a solution to a predetermined film thickness and uniformly heating and baking the applied film at 180 to 250°C using a clean oven or a hot plate.

When an alignment film made of polyimide is formed on, for example, a 10-inch glass substrate by the above-described formation method, the variation in film thickness is suppressed to about 10%.

[Problems to be Solved by the Invention] Incidentally, the voltage-transmittance characteristic of a high-definition liquid crystal panel is required to have a steep change in transmittance with respect to a change in voltage.

However, in conventional high-definition LCD panels, the transmittance changes greatly in response to such small changes in voltage, so the transmittance changes sharply due to variations in the effective voltage applied to the liquid crystal. The threshold value also varies, and there is a problem in that display unevenness occurs due to the variation in the threshold value.

The dielectric constant ε of the conventional polyimide alignment film 5 (6) is 3.0~
Since it is as small as about 3.5, a voltage drop occurs in the alignment film 5 (6), and the film thickness distribution of the alignment film 5 (6) causes variations in the threshold value.

Possible measures to reduce the variation in the threshold value include reducing voltage drop by reducing variation in the thickness of the alignment film and increasing the dielectric constant, but the spin code method or printing method that has been used for some time There is a limit to the uniformity of the film thickness in the alignment film forming methods such as the above.

Therefore, in order to reduce the influence of the film thickness distribution by using an alignment film with a high dielectric constant, polyvinylidene fluoride or a copolymer of vinylidene fluoride and trifluoroethylene, which is an organic polymer material and has a high dielectric constant of 10 or more, is used. It is conceivable to use ferroelectric polymers such as ferroelectric polymers as alignment films, but these ferroelectric polymers are insufficient in their ability to align liquid crystal molecules, which is the original role of alignment films, and cannot be put to practical use as is. The problem was that it couldn't be done.

In order to solve the above-mentioned conventional problems, the present invention provides a high dielectric film having a high dielectric constant and a liquid crystal alignment function, a method for forming the same, and the use of the high dielectric film as an alignment film for a liquid crystal display panel. It is an object of the present invention to provide a liquid crystal display panel in which display unevenness is reduced by reducing the influence of the film thickness distribution of the alignment film on the threshold voltage.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention constitutes a highly dielectric film in which ceramics having a higher dielectric constant than the cough polymer material is mixed into a polyimide polymer material.

In addition, a polyimide polymer material and a ceramic having a higher dielectric constant than the cough polymer material are mixed and formed into a film by a thin film forming method such as vacuum evaporation or sputtering, and the The structure is such that a highly dielectric film containing ceramics is formed.

Further, a ceramic powder having a higher dielectric constant than the polyimide polymer material is mixed with the polyimide polymer material, and the mixed composite material is formed into a film by a thick film forming method to form a highly dielectric film. .

Furthermore, in a liquid crystal display panel having a structure in which a pair of substrates each having a transparent electrode for display covered with an alignment film for controlling the alignment of liquid crystal on the inner surface are arranged facing each other with the liquid crystal in between, the alignment film is made of polyimide. It is composed of a high dielectric film in which the ceramics are mixed into a polymer film, or a two-layer structure of the high dielectric thin film and a polyimide polymer thin film laminated on -F.

[For production]

In the present invention, A2□0.
[ε:9.8], PZT (zircon/lead titanate, Pb(Zr-Ti)03.ε:400 or more), or PLZT (lanthanum/zircon/lead titanate, P
By composing a film containing about 20 to 50 volume % of ceramics such as b (LaZr-Ti) (h, e: 450 or more), the dielectric constant ε is 5.0 to 7.0, and the liquid crystal molecules A highly dielectric film with an orientation function can be obtained.

In addition, such a highly dielectric film can be obtained by depositing the polyimide constituents and the above-mentioned ceramic on a substrate by vacuum evaporation or sputtering, so that the ceramic is 20 to 50% by volume.
A formation method in which the polyimide precursor solution (polyamic acid solution) and the above ceramic powder are mixed at about 20 to 50% by volume and the mixed composite paste is formed by spin cording. Alternatively, it can be easily obtained by a forming method in which the coating film is coated on a substrate by a printing method or the like and the coated film is heated and baked.

Furthermore, by applying the high dielectric film obtained by the above-described formation method to the alignment film of the liquid crystal display panel, fluctuations in the threshold voltage affected by variations in the thickness of the alignment film can be suppressed to 172 or less. Furthermore, since the voltage drop is reduced, it is possible to obtain a liquid crystal display panel in which display unevenness is significantly reduced and driving voltage is lowered.

[Examples] Examples of the present invention will be described in detail below with reference to the drawings.

No. 111Z is a configuration diagram of a vapor deposition apparatus for explaining a first embodiment of a high dielectric film and a method for forming the same according to the present invention.

This example describes a method of vapor depositing an organic polymer material and ceramics on a substrate surface by a vapor deposition polymerization method, which is a type of vapor deposition method using a plurality of vapor deposition sources. A polyimide-based polymer material, i.e., a first vapor deposition #12a made of powdered dianhydride pyromellitic acid, which is the main component of polyimide, and a second vapor deposition source 12b made of 4.4' to diaminosifnyl, and a mN rate ε higher than that of the polyimide.
A third evaporation source 12c made of a ceramic having a high temperature, for example, powdered Afz03 (dielectric constant ε: 9.8) is installed,
Further, a glass substrate 14 is placed on the substrate support 13 facing these three vapor deposition sources 12a, 12b, and 12c.

For example, 8 x 10-6 To
After evacuation to a degree of vacuum of about rr, the first vapor deposition source 12a made of pyromellitic dianhydride and the
The second evaporation source 512b made of diaminosifnyl is heated to 150±2°C to evaporate, and is deposited and polymerized on the surface of the glass substrate 14. At the same time, the third evaporation source 12c made of A2□03 is irradiated with an electron beam. By evaporating it by irradiation and heating, it is sequentially deposited and mixed on the deposited and polymerized surface.

At this time, by controlling the nuclear power generation rate of the third vapor deposition source 12c made of Alzo3, 5 is added to the polyimide polymer film.
0 volume % A f 20. It is possible to form a highly dielectric thin film made of a ceramic-organic polymer composite in which fine particles are dispersed and mixed and have a dielectric constant ε of 5.0 and have a function of aligning liquid crystal molecules.

In addition to the method of simultaneously evaporating the two adhesion sources 12a, 12b, and 12c, two adhesion sources 1 consisting of biromellitic dianhydride and 4.4''-diaminosifnyl may be used.
2a, 12b and A 1. Vapor deposition source 12c made of zo3
Alternatively, the ceramic organic polymer composite may be deposited and polymerized on the opposing glass substrate 14 surface by alternating with the oxidation process, and a highly dielectric thin film made of the ceramic organic polymer composite can be formed in the same manner as in the above method.

Further, FIG. 2 is a configuration diagram of a sputtering apparatus for explaining a second embodiment of the method for forming a highly dielectric film according to the present invention.

In this embodiment, two polymer sources 2, which are the main components of polyimide, for example, dianhydride pyromellitic acid and 4,4゛-diaminosifnyl, are placed in a part of the reaction chamber 21 of the sputtering apparatus.
Accommodates 2.

The target electrode 23 is made of, for example, PLZT (lanthanum).
Zircon lead titanate [Pb(La-Zr-Ti)Oi
A ferroelectric ceramic target 24 having a dielectric constant ε: 450 or more] and a glass substrate 26 are placed on a substrate support 25 facing the ceramic target 24, and the inside of the reaction chamber 21 is once evacuated to a high vacuum. After that, argon (Ar) gas is introduced to a gas pressure of lOn+Torr.

Then, the polymer 622 is heated and evaporated, or the polymer is made into a gas and is supplied to the glass substrate 26 side to be deposited and polymerized on the glass substrate 26 surface. /cm”
The ceramic is supplied with high frequency power.

By sputtering the black target 24 and depositing a film in which ceramic fine particles made of 50% by volume of PLZT are dispersed and mixed in a polyimide polymer film, a film with a dielectric constant ε of about 6.0 and an alignment function for liquid crystal molecules is formed. It is possible to form a highly dielectric thin film made of a ceramic-organic polymer composite having the following properties.

Furthermore, FIG. 3 is a block diagram of a sputtering apparatus for explaining a third embodiment of the method for forming a highly dielectric film according to the present invention.

This embodiment differs from the embodiment shown in FIG.
As shown in the figure, polymerized polyimide target material 34
and, for example, PLZ, which has a higher dielectric constant ε than the polyimide.
A plurality of glass substrates 37, 38 are arranged on the substrate support 36 facing both the targets 34, 35, and The glass substrates 37 and 38 of the rotary motor 3 together with the substrate support 36
9, high-frequency power is simultaneously supplied to the polyimide target 34 and the ceramic target 35 made of PLZT to perform sputtering, thereby depositing a film in which ceramic fine particles made of PLZT are dispersed and mixed in polyimide. It's a method.

By the method of this example, when a film in which ceramic fine particles made of 20% by volume of PLZT are dispersed and mixed in polyimide is deposited on the glass substrate 37 and 38 surfaces by controlling the amount of sputtering of the ceramic, the dielectric constant ε is 6.0, and it is possible to form a highly dielectric thin film made of a ceramic organic polymer composite having a function of aligning liquid crystal molecules.

Furthermore, FIG. 4 is a configuration diagram of a sputtering apparatus for explaining a fourth embodiment of the method for forming a highly dielectric film according to the present invention.

This embodiment differs from the embodiment shown in FIG. 2 in that the single target electrode 42 in the reaction chamber 41 of the sputtering apparatus is made of polyimide and a ceramic material having a higher dielectric constant than the polyimide, such as A1. In addition to ZO3, PZTPLZT,
A mixed target 43 in which appropriate amounts of ceramics such as barium titanate and lead titanate are mixed and integrated is installed, and a glass substrate 45 is placed on a substrate support 44 facing the mixed target 43. In this method, sputtering is performed by supplying a predetermined high-frequency power to the polyimide, thereby depositing a film in which the ceramic fine particles are dispersed and mixed in polyimide.

Similar to the embodiments shown in FIGS. 2 and 3, the method of this embodiment also produces a polymer made of a ceramic-organic polymer composite having a dielectric constant ε of about 6.0 and having a function of aligning liquid crystal molecules. Dielectric thin films can be formed.

Furthermore, as a fifth example of the method for forming a highly dielectric film according to the present invention, titanic acid having an average particle size of 0.05 μI is added to a polyimide precursor solution, for example, a polyamic acid solution (Sun Eher 610, manufactured by Nissan Kagaku). Barium (BazTiOa)
20-t% of fine ceramic powder is mixed, and this mixed paste is coated on a glass substrate to a predetermined film thickness by adjusting and controlling the viscosity, spin speed, etc. of the mixed paste using a spin code method. After that, by baking at about 250°C, the dielectric constant ε is about 2.5 of that of polyimide.
It is possible to form a highly dielectric film made of a ceramic-organic polymer composite having a function of aligning liquid crystal molecules with approximately 7 times as much dielectric strength.

In addition to barium titanate (BazTi04), lead titanate (PbTiO+
).

Ferroelectric ceramics such as strontium titanate (SrTiO:+), lead niobate (PbNb03), PZT, and PLZT can be used.

FIG. 5 is a structural diagram for explaining one embodiment of a liquid crystal display panel using a highly dielectric film made of a ceramic polymer composite according to the present invention as an alignment film.

In the figure, 51 & 52 are transparent electrodes 53 for display on the inner surface.
and 54 are formed, and on the transparent electrodes 53 and 54 provided on each glass substrate 5152, for example, dianhydride pyromellitic acid and 4.4°-diaminosifnyl dianhydride, which are the main components of polyimide, are formed. two polymers and P
LZT [lanthanum zircon lead titanate (Pb(La
-Zr-Ti)03. A highly dielectric ceramic having a dielectric constant ε: 450 or more] is simultaneously sputtered to form a ceramic organic polymer composite film in which 50% by volume of ceramic particles made of PLZT are dispersed and mixed in a polyimide polymer film. Alignment films 55 and 56 having a thickness of 100 mm and made of a highly dielectric thin film are provided by the formation method of the third embodiment described above with reference to FIG.

Alternatively, 20-t% of ceramic fine powder made of barium titanate (BazTiOa) is mixed into a polyamic acid solution, which is a polyimide precursor solution, and this mixed paste is applied by a spin cord method, and then fired at approximately 250°C. Then, by the method of forming a ceramic organic polymer composite film in which 20% of ceramic particles made of Ba and TiO4 are dispersed and mixed in polyimide, a 600-layer film made of a highly dielectric film was formed by the formation method of the fifth embodiment. An alignment film 55,56 having a thickness of .

After rubbing each of the alignment films 55 and 56,
The glass substrates 5152 are bonded together with a spacer 57 interposed therebetween, and a panel structure is formed in which a gap regulated by the spacer 57 is filled with liquid crystal 58.

In a liquid crystal display panel having such a configuration, the alignment film 5
5.56, polyimide, which has traditionally been used for alignment films, is used as a base material, and ceramics with a high dielectric constant are mixed with it, so it has the function of aligning liquid crystal molecules, and the dielectric constant ε is higher than that of polyimide. Approximately 2.0 to 2.5 times 6 to 7
Therefore, fluctuations in the threshold voltage due to variations in the film thickness of the alignment films 55, 56 can be suppressed to 172 or less, and since the voltage drop is reduced, display unevenness is significantly reduced.

Note that the surface of the alignment film, which is made of a highly dielectric film of a ceramic-ink organic polymer composite formed by firing a coating film in which ceramic-ink fine powder is dispersed and mixed in polyimide, has relatively small irregularities. Since it is easy to do so, it may be smoothed by polishing using diamond paste or the like after firing.

Furthermore, FIG. 6 is a configuration diagram for explaining another embodiment of a liquid crystal display panel using a highly dielectric film made of a ceramic-ink polymer composite according to the present invention as an alignment film, and FIG. The same parts are given the same symbols.

The difference between the embodiment shown in this figure and the example shown in FIG. 5 is that transparent display electrodes 53 and 54 provided on each glass substrate 51,
As the alignment film 61 provided above, for example, 2
A highly dielectric thin film 62 with a thickness of 600 mm is made of a ceramic organic polymer composite in which ceramic particles made of BazTi04 etc. of 014 t% are dispersed, and a polyimide-based polymer having a liquid crystal molecule alignment function is placed on top of it. molecular thin film,
For example, it has a two-layer structure in which polyimide thin films 63 having a thickness of 100 layers are laminated.

This embodiment also provides the same effects as the embodiment shown in FIG. 5, and also improves the surface smoothness of the alignment film 61 and strengthens the alignment force of liquid crystal molecules.

〔Effect of the invention〕

As is clear from the above description, according to the high dielectric film and the method for forming the same according to the present invention, a composite film in which a polyimide polymer film is dispersed and mixed with a ceramic having a higher dielectric constant than the polyimide polymer film. By forming a thin film, a highly dielectric film having a function of aligning liquid crystal molecules and having a high dielectric constant can be easily obtained.

In addition, by using such a high dielectric film as an alignment film of a liquid crystal display panel, the influence of the film thickness distribution of the alignment film on the threshold voltage can be significantly reduced, resulting in a low drive voltage liquid crystal display with extremely low display unevenness. It has an excellent advantage of making it possible to realize a display panel.

Therefore, it is extremely advantageous to apply it to a TN type or STN type liquid crystal display panel that provides high-definition display.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a vapor deposition apparatus for explaining a first embodiment of a highly dielectric thin film and a method for forming the same according to the present invention, and FIG. 2 illustrates a second embodiment of a method for forming the same according to the present invention. FIG. 3 is a block diagram of a sputtering apparatus for explaining a third embodiment of the forming method according to the present invention, and FIG. 4 is a fourth embodiment of the forming method according to the present invention. 5 is a block diagram showing an embodiment of a liquid crystal display panel using the high dielectric film according to the present invention as an alignment film. FIG. A configuration diagram showing another embodiment of a liquid crystal display panel using a dielectric thin film as an alignment film.The seventh issue is a configuration diagram for explaining a conventional liquid crystal display panel. 1 to 6, 11 is a vapor deposition device, 12a is a first vapor deposition source, 12b is a second vapor deposition source, 12c is a third vapor deposition source, 13,2536.44 is a substrate support, 14,26,37 , 38, 45.5152 is a glass substrate, 2L31.41 is a reaction chamber, 22 is a polymer evaporation source, 23.32, 33.42 is a Kugett electrode, 2
4.35 is a ceramic target, 34 is a polyimide target, 39 is a rotating motor, 43 is a mixed target, 53 and 54 are transparent electrodes, 55.56 is an alignment film, 57
58 is a spacer, 58 is a liquid crystal, 61v is an alignment film having a two-layer structure, 62 is a highly dielectric thin film, and 63 is a polyimide thin film. →Water water diagram No. 5 Shita Wa water diagram No. 7

Claims (6)

[Claims] (1) A high dielectric film characterized by being formed by mixing a polyimide polymer material with a ceramic having a higher dielectric constant than the polymer material. (2) A film with a mixture of a polyimide polymer material and a ceramic having a higher dielectric constant than the polymer material is formed using a thin film formation method, and the ceramic is mixed into the polyimide polymer film. 1. A method for forming a highly dielectric film, characterized in that a high dielectric film is formed. (3) The method for forming a highly dielectric film according to claim 2, wherein the thin film forming method is a vacuum evaporation method or a sputtering method. (4) A ceramic powder having a higher dielectric constant than the polyimide polymer material is mixed with the polyimide polymer material, and the mixed composite material is formed into a high dielectric film by a thick film forming method. Characteristic method for forming highly dielectric films. (5) Transparent electrodes for display (53) each covered with an alignment film (55, 56) that regulates the alignment of the liquid crystal (58)
, 54) are arranged facing each other with a liquid crystal interposed therebetween, wherein the alignment film (55, 56) is a high dielectric film obtained by the formation method according to claim 2 or 3. A liquid crystal display panel characterized by being made of a transparent film. (6) the alignment film (61) is a highly dielectric thin film (62) obtained by the formation method according to claim 2 or 3;
6. The liquid crystal display panel according to claim 5, characterized in that it has a two-layer structure with a polyimide polymer thin film (63) laminated thereon.