JP5939614B2 - Alignment film and liquid crystal display device using the same - Google Patents

Description

  The present invention relates to an alignment film for aligning a liquid crystal layer sandwiched between two substrates, an alignment film forming composition for forming the alignment film, and a liquid crystal display device having the alignment film.

  Liquid crystal display devices are used in a wide range of applications due to their high display quality, thinness, light weight, low power consumption, and other features such as mobile phone monitors, digital still camera monitors, desktop PC monitors, and printing. It is used in various applications such as monitors for monitors, medical monitors, and LCD TVs. As these applications are expanded, liquid crystal display devices are strongly required to have high luminance, low power consumption, and low cost by increasing transmittance.

  Usually, the display of a liquid crystal display device is performed by changing the alignment direction of the liquid crystal molecules by applying an electric field to the liquid crystal molecules of the liquid crystal layer sandwiched between a pair of substrates, and thereby changing the optical characteristics of the liquid crystal layer. Is called. The alignment direction of the liquid crystal molecules when no electric field is applied is defined by an alignment film obtained by rubbing the surface of the polyimide thin film. Conventionally, an active drive type liquid crystal display device provided with a switching element such as a thin film transistor (TFT) for each pixel is provided with electrodes on each of a pair of substrates sandwiching the liquid crystal layer, and the direction of the electric field applied to the liquid crystal layer is determined by the substrate surface Is set to be a so-called vertical electric field that is substantially perpendicular to the liquid crystal display, and display is performed using the optical rotation of liquid crystal molecules constituting the liquid crystal layer. As a typical vertical electric field type liquid crystal display device, a twisted nematic (TN: Twisted Nematic) method is known.

  In a TN liquid crystal display device, a narrow viewing angle is one of the major problems. Therefore, an IPS (In-Plane Switching) method and a VA (Vertical Alignment) method are known as display methods for achieving a wide viewing angle.

  In some types of liquid crystal display devices, it is known that if the volume resistivity of the alignment film is high, residual charges are accumulated in the liquid crystal display device, resulting in an afterimage in which the display image is burned. Patent Document 1 proposes a volume resistivity reduction of an alignment film in the VA method. Patent Document 2 proposes an alignment film structure.

JP 2007-241249 A JP 2002-162630 A

  However, the alignment film used in a conventional liquid crystal display device has a problem that the suppression of image sticking is insufficient.

  An object of the present invention is to provide a liquid crystal display device provided with an alignment film in which display images are less burned. The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

The liquid crystal display device according to the present invention includes a first substrate and a second substrate, at least one of which is transparent, a liquid crystal layer disposed between the first substrate and the second substrate, An electrode group formed on at least one of the first substrate and the second substrate and configured to apply an electric field to the liquid crystal layer; a plurality of active elements connected to the electrode group; And an alignment film disposed on at least one of the second substrate, the alignment film is imparted with a liquid crystal alignment ability by irradiating polarized ultraviolet rays, and polyamide It contains a polyimide having a first compound that is an acid ester and a second compound that is a polyamic acid as a precursor, and the chemical structure of the second compound is represented by the following formula (1): .

However, n is an integer of 10 to 10000, each X ₁ is a divalent organic group, and each Y ₁ is a tetravalent organic group that does not contain a cyclobutane structure in the structure. 90% 30% or more of the ₁ below, containing at least one unsaturated ring structure in the structure, a tetravalent organic group.

  In addition, the alignment film includes a total of polyimides having the first compound and the first compound as precursors, and a total of polyimides having the second compound and the second compounds as precursors. It may be included in a molar ratio of 20:80 to 80:20.

Moreover, the tetravalent organic group containing the unsaturated cyclic structure may be a tetravalent organic group of any compound selected from the compounds shown in the following compound group A.

However, each A ₁ is independently an alkylene group having 1 to 3 carbon atoms, —CR ₂ —, —CO—, —COO—, —NR—, —NH—CO—, —O—, —S—, — SO—, —SO ₂ —, —Si—, and —SiR ₂ —, wherein each R contained in A ₁ is independently hydrogen, an alkyl group having 1 to 8 carbon atoms, And a structure selected from a fluoroalkyl group having 1 to 8 carbon atoms.

  In addition, at least one of the hydrogen atoms bonded to the tetravalent organic group containing the unsaturated cyclic structure contained in the compound represented by the compound group A is an alkyl group having 1 to 3 carbon atoms, It may be substituted with a 3 alkoxy group, a C 1-3 fluoroalkyl group, a C 1-3 fluoroalkoxy group, a fluorine atom, a chlorine atom, or a bromine atom.

Further, 50% or more of each X ₁ may be a divalent organic group containing at least one unsaturated cyclic structure in the structure.

  The first compound may be formed using a cyclobutanetetracarboxylic dianhydride derivative and an aromatic diamine.

The alignment film according to the present invention is an alignment film containing polyimide and the polyimide precursor, and the polyimide precursor includes a first compound that is a polyamic acid ester and a second compound that is a polyamic acid. In addition, the chemical structure of the second compound is represented by the following formula (1).

However, n is an integer of 10 to 10000, each X ₁ is a divalent organic group, and each Y ₁ is a tetravalent organic group that does not contain a cyclobutane structure in the structure. 90% 30% or more of the ₁ below is a tetravalent organic group containing at least one unsaturated ring structure in the structure.

An alignment film forming composition according to the present invention is an alignment film forming composition for forming an alignment film containing polyimide and the polyimide precursor, wherein the polyimide precursor is a polyamic acid ester. One chemical compound and the second compound which is a polyamic acid are included, and the chemical structure of the second compound is represented by the following formula (1).

However, n is an integer of 10 to 10000, each X ₁ is a divalent organic group, and each Y ₁ is a tetravalent organic group that does not contain a cyclobutane structure in the structure. 90% 30% or more of the ₁ below is a tetravalent organic group containing at least one unsaturated ring structure in the structure.

  According to the present invention, it is possible to provide a liquid crystal display device including an alignment film with less display image burn-in.

4 is a schematic cross-sectional view of the vicinity of one pixel of the liquid crystal display device according to Embodiment 1. FIG. 3 is a schematic plan view of an active matrix substrate showing a configuration near one pixel of the liquid crystal display device according to Embodiment 1. FIG. FIG. 2B is a cross-sectional view taken along line 2B shown in FIG. 2A. 2C is a cross-sectional view taken along line 2C shown in FIG. 2A. 6 is a schematic cross-sectional view of the vicinity of one pixel of a liquid crystal display device according to Example 2. FIG. 6 is a schematic plan view of an active matrix substrate showing a configuration near one pixel of a liquid crystal display device according to Example 2. FIG. FIG. 4B is a cross-sectional view taken along line 4B shown in FIG. 4A. FIG. 4B is a cross-sectional view taken along line 4C shown in FIG. 4A. 6 is a schematic cross-sectional view of the vicinity of one pixel of a liquid crystal display device according to Example 3. FIG. 6 is a schematic cross-sectional view of the vicinity of one pixel of a liquid crystal display device according to Example 4. FIG. 6 is a schematic cross-sectional view of the vicinity of one pixel of a liquid crystal display device according to Example 5. FIG. FIG. 10 is a schematic plan view of an active matrix substrate showing a configuration near one pixel of a liquid crystal display device according to Example 5.

  As an alignment treatment method for an alignment film (also referred to as an alignment control film) in an IPS liquid crystal display device, liquid crystal alignment ability can be achieved by irradiating light on the alignment film surface instead of rubbing alignment technology in which the alignment film surface is rubbed with a cloth. Attention has been focused on the optical alignment technology to be applied. In the photo-alignment technique, image sticking (also referred to as an afterimage) has become a major issue, and the inventors have paid attention to the fact that the alignment film requires the following two characteristics in order to solve the image sticking. The first is stable liquid crystal alignment ability (high anchoring characteristics) over a long period of time, and the other is reduction of the volume resistivity of the alignment film. In order to obtain stable liquid crystal alignment ability, it is effective to use a polyamic acid ester containing a cyclobutane derivative in the chemical structure as a photo-alignment film material. However, the inventors paid attention to the problem that the polyamic acid ester has a high volume resistivity, and DC charges accumulate at the interface of the alignment film when the liquid crystal is driven, resulting in burn-in.

As a result of intensive studies by the inventors, in order to reduce the volume resistivity of the photo-alignment film material containing the first compound that is a polyamic acid ester, a polyamide having a chemical structure represented by the following chemical formula (1) It turned out that it is effective to mix the 2nd compound which is an acid with the said photo-alignment film material.

However, n is an integer of 10 to 10000, each X ₁ is a divalent organic group, and 30% or more and 90% or less of each Y ₁ is at least one unsaturated cyclic group in the structure. It is a tetravalent organic group containing a structure. In addition, n in the above chemical formula (1) increases the strength of the alignment film as the molecular weight increases, so that the alignment film is more resistant to abrasion, or to obtain an alignment film with less display image burn-in. It is preferably 20 to 10000, and more preferably 30 to 10000.

Each Y ₁ is a tetravalent organic group, and 40% or more and 85% or less of each Y ₁ is preferably a tetravalent organic group containing at least one unsaturated cyclic structure in the structure. Furthermore, it is particularly preferred that 50% or more and 80% or less of each Y _{1 is} a tetravalent aromatic group containing at least one unsaturated cyclic structure in the structure.

Further, 30% or more and 90% or less of each Y ₁ may be a tetravalent organic group containing one unsaturated cyclic structure in the structure. Each Y ₁ is a tetravalent organic group, and 40% or more and 85% or less of each Y ₁ may be a tetravalent organic group containing one unsaturated cyclic structure in the structure. Further, 50% or more and 80% or less of each Y ₁ may be a tetravalent aromatic group containing one unsaturated cyclic structure in the structure. It is preferable that Y ₁ contains only one unsaturated cyclic structure from the viewpoint of dissolution stability of the photo-alignment film material containing the first compound that is a polyamic acid ester in a solvent.

  The unsaturated cyclic structure described above may be a cyclic structure selected from a benzene ring structure, a naphthalene ring structure, and an anthracene ring structure. The unsaturated cyclic structure described above is preferably a cyclic structure selected from a benzene ring structure and a naphthalene ring structure. This is because when the unsaturated cyclic structure is an anthracene ring structure, the formed alignment film may be colored. The unsaturated cyclic structure is particularly preferably a benzene ring structure. This is because when the unsaturated cyclic structure is a naphthalene ring structure, the alignment film to be formed may be colored, although it is not as remarkable as the anthracene ring structure.

Further, each Y ₁ is a tetravalent organic group, and 30% or more and 90% or less of each Y ₁ may be a tetravalent organic group containing two or less benzene ring structures in the structure. Good. Further, 40% or more and 85% or less of each Y ₁ may be a tetravalent organic group containing two or less benzene ring structures in the structure. Furthermore, 50% or more and 80% or less of each Y ₁ may be a tetravalent organic group containing two or less benzene ring structures in the structure.

  The unsaturated cyclic structure described above may be not only a carbocyclic structure composed of hydrocarbons but also a heterocyclic structure containing elements other than carbon in the cyclic structure. However, when the unsaturated cyclic structure is a heterocyclic structure, the cost of the alignment film to be formed is high, and the alignment film to be formed may be colored. A carbocyclic structure consisting of is more preferred. Further, when the unsaturated cyclic structure is a heterocyclic structure, if the heterocyclic structure contains a nitrogen atom, the formed alignment film may be more intensely colored. Therefore, it is more preferable that the heterocyclic structure does not contain a nitrogen atom.

  By adopting such a configuration, photoconductivity can be imparted to the polyamic acid, and the resistance can be reduced by absorbing light from the backlight (BL) of the liquid crystal display device, which is effective in eliminating afterimages. Works. If the conjugated system in the molecular structure is expanded by introducing an unsaturated cyclic structure, the absorption wavelength becomes longer and the absorption efficiency of the visible light of the backlight increases, and the conjugated electron system expands to facilitate the movement of π electrons. Therefore, improvement in photoconductivity can be expected.

In addition, the volume resistivity decreases as the number of Y ₁ which is a tetravalent organic group including an unsaturated cyclic structure in the structure of the polyamic acid decreases. However, if the number is too large, the transmittance of the alignment film formed is reduced. There is a problem that the dissolution stability of the amount of the alignment film material in the solvent decreases.

Each Y ₁ is preferably a tetravalent organic group that does not contain a cyclobutane structure in the structure. That is, it is preferable that the polyamic acid used for this invention does not contain a cyclobutane derivative as the raw material. If Y ₁ contains a cyclobutane structure in the structure, the polymer chain of the polyamic acid is cleaved at the cyclobutane structure portion during light irradiation, and the molecular weight of the polyamic acid is lowered. It is not preferable that Y ₁ contains a cyclobutane structure in the structure because the alignment film becomes brittle due to the decrease in molecular weight, which decreases the stability of the liquid crystal alignment ability and deteriorates the afterimage characteristics.

  The alignment film in the liquid crystal display device of the present invention includes a total of a first compound that is a polyamic acid ester and a polyimide that uses the first compound as a precursor, a second compound that is a polyamic acid, and the second compound. Is preferably included in a molar ratio of 20:80 to 80:20, more preferably in a molar ratio of 30:70 to 70:30, and still more preferably 40:60. In a molar ratio of ˜60: 40. In the alignment film, if the ratio of the polyamic acid ester and the polyimide having a polyamic acid ester as a precursor is too high, the resistance of the alignment film becomes high, and the ratio of the polyimide having the polyamic acid and the polyamic acid as a precursor is too high. And the stability of the liquid crystal alignment ability of the alignment film is deteriorated, which is not preferable because the afterimage characteristics deteriorate.

In addition, among Y ₁ contained in the chemical structure of the second compound, each of the tetravalent organic groups containing an unsaturated cyclic structure is independently selected from the compounds shown in the following compound group A It may be a tetravalent organic group of the compound.

In addition, among Y ₁ contained in the chemical structure of the second compound, the tetravalent organic group containing an unsaturated cyclic structure is any one compound selected from the compounds shown in the following compound group A Or a tetravalent organic group.

However, each A ₁ is independently an alkylene group having 1 to 3 carbon atoms, —CR ₂ —, —CO—, —COO—, —NR—, —NH—CO—, —O—, —S—, — SO—, —SO ₂ —, —Si—, and —SiR ₂ —, wherein each R contained in A ₁ is independently hydrogen, an alkyl group having 1 to 8 carbon atoms, And a structure selected from a fluoroalkyl group having 1 to 8 carbon atoms.

  In addition, each hydrogen atom bonded to the unsaturated cyclic structure contained in the structure of the compound represented by the compound group A is independently an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a carbon number. It is substituted or unsubstituted with a 1 to 3 fluoroalkyl group, a C1 to C3 fluoroalkoxy group, a fluorine atom, a chlorine atom, or a bromine atom. That is, the hydrogen atom bonded to the unsaturated cyclic structure contained in the structure of the compound represented by the compound group A is independently an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a carbon number. It may be substituted with a 1 to 3 fluoroalkyl group, a C1 to C3 fluoroalkoxy group, a fluorine atom, a chlorine atom, or a bromine atom.

Hereinafter, a specific structure of tetravalent organic group containing an unsaturated cyclic structure Y ₁ in the following chemical formula (Y-1) ~ (Y -32). However, it is not limited to these.

Typical examples of the aliphatic group corresponding to Y ₁ (a tetravalent organic group not containing an unsaturated cyclic structure) with respect to the tetravalent organic group containing the unsaturated cyclic structure exemplified above are as follows. . However, it is not limited to these.

Further, 50% or more of X ₁ in the chemical formula (1) is preferably a divalent organic group containing an unsaturated cyclic structure in the structure. More preferably, 60% or more of X ₁ in the chemical formula (1) is a divalent organic group containing an unsaturated cyclic structure in the structure. Moreover, it is particularly preferable that 70% or more of X ₁ in the chemical formula (1) is a divalent organic group containing an unsaturated cyclic structure in the structure. By adopting this configuration, the resistance of the second compound, which is a polyamic acid, can be lowered, which effectively acts to improve the afterimage characteristics.

In addition, among X ₁ contained in the chemical structure of the second compound, each of the divalent organic groups containing an unsaturated cyclic structure is independently selected from the compounds shown in the following compound group B It may be a divalent organic group of the compound.

In addition, among X ₁ contained in the chemical structure of the second compound, the divalent organic group containing an unsaturated cyclic structure is any one compound selected from the compounds shown in the following compound group B It is good also as being a divalent organic group.

However, A ₂ is each independently an alkylene group having 1 to 3 carbon atoms, —CR ₂ —, —CO—, —COO—, —NR—, —NH—CO—, —O—, —S—, — SO—, —SO ₂ —, —Si—, and —SiR ₂ —, wherein each R contained in A ₂ is independently hydrogen, an alkyl group having 1 to 8 carbon atoms, And a structure selected from a fluoroalkyl group having 1 to 8 carbon atoms. A ₃ is a single bond or an alkylene group having 1 to 8 carbon atoms.

  In addition, each hydrogen atom bonded to the unsaturated cyclic structure included in the structure of the compound represented by the compound group B is independently an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a carbon number. Substituted with 1 to 3 fluoroalkyl group, 1 to 3 fluoroalkoxy group, fluorine atom, chlorine atom, bromine atom, hydroxyl group, carboxylic acid group, sulfonic acid group, phosphoric acid group, or phosphonic acid group Or unsubstituted. That is, each hydrogen atom bonded to the unsaturated cyclic structure contained in the structure of the compound represented by the compound group B is independently an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a carbon number. Substituted with 1 to 3 fluoroalkyl group, 1 to 3 fluoroalkoxy group, fluorine atom, chlorine atom, bromine atom, hydroxyl group, carboxylic acid group, sulfonic acid group, phosphoric acid group, or phosphonic acid group It is good to be.

  In addition, the unsaturated cyclic structure in the divalent organic group including the unsaturated cyclic structure described above may be a cyclic structure selected from a benzene ring structure, a naphthalene ring structure, and an anthracene ring structure. Moreover, it is preferable that the unsaturated cyclic structure in the divalent organic group containing the unsaturated cyclic structure described above is a cyclic structure selected from a benzene ring structure and a naphthalene ring structure. This is because when the unsaturated cyclic structure is an anthracene ring structure, the formed alignment film may be colored. In addition, the unsaturated cyclic structure in the divalent organic group containing the above unsaturated cyclic structure is particularly preferably a benzene ring structure. This is because when the unsaturated cyclic structure is a naphthalene ring structure, the alignment film to be formed may be colored, although it is not as remarkable as the anthracene ring structure.

  In addition, the unsaturated cyclic structure in the divalent organic group containing the unsaturated cyclic structure described above may be not only a carbocyclic structure composed of hydrocarbons but also a heterocyclic structure containing elements other than carbon in the cyclic structure. Good. However, when the unsaturated cyclic structure is a heterocyclic structure, the cost of the alignment film to be formed is high, and the alignment film to be formed may be colored. A carbocyclic structure consisting of is more preferred. Further, when the unsaturated cyclic structure is a heterocyclic structure, if the heterocyclic structure contains a nitrogen atom, the formed alignment film may be more intensely colored. Therefore, it is more preferable that the heterocyclic structure does not contain a nitrogen atom.

Hereinafter, a specific structure of a divalent organic group containing an unsaturated cyclic structures of X ₁ in the following formula (X-1) ~ (X -39). However, it is not limited to these.

  However, in the said chemical formula (X-31), (X-32), (X-33), m is an integer of 1-6.

Typical examples of the aliphatic group corresponding to X ₁ (divalent organic group not containing an unsaturated cyclic structure) with respect to the divalent organic group containing the unsaturated cyclic structure exemplified above are as follows. . However, it is not limited to these.

Moreover, it is preferable that 50 mol% of the 1st compound which is a polyamic acid ester contained in the alignment film with which the liquid crystal display device of this invention is equipped is a compound shown by following Chemical formula (2). Moreover, it is preferable that 70 mol% of the 1st compound which is a polyamic acid ester contained in the alignment film with which the liquid crystal display device of this invention is equipped is a compound shown by following Chemical formula (2). It is particularly preferable that 90 mol% of the first compound which is a polyamic acid ester contained in the alignment film provided in the liquid crystal display device of the present invention is a compound represented by the following chemical formula (2).

However, n is an integer of 10 to 10,000, and in the compound represented by the chemical formula (2), X ₂ is a divalent organic group containing at least one unsaturated cyclic structure in the structure, and Y ₂ is It is independently an alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms, and Z ₂ is independently an alkyl group having 1 to 8 carbon atoms. By adopting this configuration, it is possible to obtain a stable liquid crystal alignment ability and effectively act to improve the afterimage characteristics. In addition, n in the above chemical formula (2) increases the strength of the alignment film as the molecular weight increases, so that the alignment film is more resistant to abrasion or to obtain an alignment film with less display image burn-in. It is preferably 20 to 10000, and more preferably 30 to 10000.

In addition, a representative example of a divalent organic group containing at least one unsaturated cyclic structure in the structure corresponding to X ₂ in the compound represented by the chemical formula (2) is the compound represented by the chemical formula (1). The divalent compound of any one compound selected from the compounds shown in the compound group B, exemplified by a divalent organic group containing at least one unsaturated cyclic structure in the structure, corresponding to X ₁ Organic groups are likewise mentioned.

  An object of the present invention is to provide an alignment film for a liquid crystal display device in which display images are less burned and a liquid crystal display device including the alignment film.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. An example of the alignment control film according to the present invention used in these examples is shown, and similar effects have been confirmed for other structures. Hereinafter, a substrate on which an active element such as a thin film transistor is formed is referred to as an active matrix substrate. In addition, when the counter substrate has a color filter, this is also referred to as a color filter substrate. In the present invention, the desired contrast as a target is 500: 1 or more, and the target afterimage disappearance time is preferably within 5 minutes. The afterimage disappearance time is determined by the method defined in the following examples.

  FIG. 1 is a schematic cross-sectional view of the vicinity of one pixel of the liquid crystal display device according to the first embodiment. FIG. 2 is a schematic plan view of an active matrix substrate showing a configuration in the vicinity of one pixel of the liquid crystal display device according to the first embodiment. 2A is a schematic plan view of an active matrix substrate showing a configuration in the vicinity of one pixel of the liquid crystal display device according to Example 1. FIG. FIG. 2B is a cross-sectional view taken along line 2B shown in FIG. 2A. 2C is a cross-sectional view taken along line 2C shown in FIG. 2A. FIG. 1 corresponds to a part of a cross section taken along line 2B shown in FIG. 2A.

  2B and FIG. 2C schematically show the configuration of the main part, and do not correspond one-to-one to the cut portions of the 2B line and the 2C line in FIG. 2A. For example, in FIG. 2B, the semiconductor film 116 is not shown, and in FIG. 2C, only one through hole 118 that connects the common electrode 103 and the common wiring 120 is shown.

  In this embodiment, a scanning wiring (gate electrode) 104 and a common electrode wiring (common wiring) 120 made of Cr (chromium) are disposed on a glass substrate 101 as an active matrix substrate (first substrate). A gate insulating film 107 made of silicon nitride is formed so as to cover the gate electrode 104 and the common wiring 120.

  A semiconductor film 116 made of amorphous silicon or polysilicon is disposed on the gate electrode 104 through a gate insulating film 107 so as to function as an active layer of a thin film transistor (TFT) 115 as an active element. In addition, a signal wiring (drain electrode) 106 and a pixel electrode (source electrode) 105 made of Cr / Mo (chromium / molybdenum) are arranged so as to overlap a part of the pattern of the semiconductor film 116 and cover all of them. A protective insulating film 108 made of silicon nitride is formed.

  In addition, as shown in FIG. 2C, the common electrode 103 connected to the common wiring 120 through the through hole 118 formed through the gate insulating film 107 and the protective insulating film 108 is an overcoat layer (organic protective film) 112. Is placed on top. As shown in FIG. 2A, the common electrode 103 led out from the common wiring 120 through the through hole 118 is formed so as to face the pixel electrode 105 in the area of one pixel in plan view. Yes.

  In this embodiment, the pixel electrode 105 is arranged in a lower layer of the protective insulating film 108 below the organic protective film 112, and the common electrode 103 is arranged on the organic protective film 112. One pixel is configured in a region sandwiched between the plurality of pixel electrodes 105 and the common electrode 103. An alignment control film 109 is formed on the surface of the active matrix substrate in which the unit pixels configured as described above are arranged in a matrix, that is, on the organic protective film 112 on which the common electrode 103 is formed.

  On the other hand, as shown in FIG. 1, a color filter layer 111 is arranged on a glass substrate 102 constituting a counter substrate so as to be divided for each pixel by a light shielding film (black matrix) 113. The film 113 is covered with an organic protective film 112 made of a transparent insulating material. Further, an alignment control film 109 is also formed on the organic protective film 112 to constitute a color filter substrate (second substrate).

  The active matrix substrate (first substrate) and the color filter substrate (second substrate) constitute a pair of substrates. Therefore, in this specification, the active matrix substrate (first substrate) and the color filter substrate (second substrate) may be collectively referred to as a pair of substrates.

  These alignment control films 109 are given a liquid crystal alignment ability by irradiation with linearly polarized ultraviolet rays extracted using a rubbing alignment method or a high pressure mercury lamp as a light source and using a pile polarizer laminated with a quartz plate.

  A glass substrate 101 constituting an active matrix substrate and a glass substrate 102 constituting a color filter substrate are arranged to face each other on the surface of the alignment control film 109, and a liquid crystal layer (liquid crystal composition) composed of liquid crystal molecules 110a therebetween. Layer) 110b is disposed. A polarizing plate 114 is formed on each of the outer surfaces of the glass substrate 101 constituting the active matrix substrate and the glass substrate 102 constituting the color filter substrate.

  As described above, an active matrix liquid crystal display device (TFT liquid crystal display device) using a thin film transistor (TFT) is configured. In this TFT liquid crystal display device, the liquid crystal molecules 110a constituting the liquid crystal composition layer 110b are aligned substantially parallel to the opposing glass substrates 101 and 102 when no electric field is applied, and are defined by the alignment treatment. Homogeneous alignment is performed in the initial alignment direction.

  Here, when a voltage is applied to the gate electrode 104 to turn on the TFT 115, an electric field 117 is applied to the liquid crystal composition layer 110b due to a potential difference between the pixel electrode 105 and the common electrode 103, and the dielectric property of the liquid crystal composition layer 110b. The liquid crystal molecules 110a constituting the liquid crystal composition layer 110b change its direction to the electric field direction by the interaction between the anisotropy and the electric field. At this time, display can be performed by changing the light transmittance of the liquid crystal display device by the refractive anisotropy of the liquid crystal composition layer 110 b and the action of the polarizing plate 114.

  The organic protective film 112 may be made of a thermosetting resin such as an acrylic resin, an epoxy acrylic resin, or a polyimide resin that is excellent in insulation and transparency. In addition, a photocurable transparent resin may be used as the organic protective film 112, or an inorganic material such as a polysiloxane resin may be used. Furthermore, the organic protective film 112 may also serve as the alignment control film 109.

  In general, in the IPS system, unlike the vertical electric field system represented by the conventional TN system, the interface tilt with the substrate surface is not necessary in principle, and it is known that the viewing angle characteristics are better as the interface tilt angle is smaller. In particular, when the angle is set to 1 degree or less, the color change and the brightness change due to the viewing angle of the liquid crystal display device can be greatly suppressed, so that the alignment by the photo-alignment method in which the tilt angle hardly occurs is effective.

Next, as a method for manufacturing the liquid crystal display device of the present embodiment, formation of an alignment control film using a rubbing-less alignment method for the alignment control film will be described. The flow of the alignment control film forming process according to this embodiment is as follows (1) to (4).
(1) Coating / formation of orientation control film (forms a uniform coating over the entire display area)
(2) Imidization firing of orientation control film (promotes removal of varnish solvent and high heat resistance polyimide)
(3) Liquid crystal alignment ability imparted by polarized irradiation (uniform orientation ability is imparted to the display area)
(4) Promotion / stabilization of alignment ability by (heating, infrared irradiation, far infrared irradiation, electron beam irradiation, radiation irradiation)

The alignment control film is formed through the above four-stage process, but is not limited to the order of the above processes (1) to (4). In the following cases (a) and (b) Further effects are expected.
(A) By processing the above (3) and (4) so as to overlap in time, the alignment control film can be formed more effectively by accelerating the provision of liquid crystal alignment ability and inducing a crosslinking reaction. It becomes.
(B) When heating (4) above, infrared irradiation, far-infrared irradiation, etc. are used, the above process (4) can be achieved by temporally overlapping (2), (3) and (4). It is also possible to serve as the imidization process (2), and an alignment control film can be formed in a short time.

  Next, a specific manufacturing method of this embodiment will be described. As the glass substrate 101 constituting the active matrix substrate and the glass substrate 102 constituting the color filter substrate, a glass substrate having a thickness of 0.7 mm and a polished surface is used. A thin film transistor 115 formed on the glass substrate 101 includes a pixel electrode (source electrode) 105, a signal wiring (drain electrode) 106, a scanning wiring (gate electrode) 104, and a semiconductor film 116 made of amorphous silicon.

  The scanning wiring 104, the common electrode wiring 120, the signal wiring 106, and the pixel electrode 105 were all formed by patterning a chromium film, and the distance between the pixel electrode 105 and the common electrode 103 was 7 μm. For the common electrode 103 and the pixel electrode 105, a chromium film having a low resistance and easy patterning is used. However, a transparent electrode can be formed by using an ITO film to achieve higher luminance characteristics. It is.

  The gate insulating film 107 and the protective insulating film 108 were made of silicon nitride, and the film thicknesses were each 0.3 μm. An acrylic resin was applied thereon, and a transparent and insulating organic protective film 112 was formed by heat treatment at 220 ° C. for 1 hour.

  Next, as shown in FIG. 2C, through holes 118 were formed up to the common electrode wiring 120 by photolithography and etching, and the common electrode 103 connected to the common electrode wiring 120 was formed by patterning.

  As a result, in the unit pixel (one pixel), as shown in FIG. 2A, the pixel electrode 105 is arranged between the three common electrodes 103, and the number of pixels is 1024 × 3 (R, G, (Corresponding to B) An active matrix substrate having 1024 × 3 × 768 pieces composed of signal wirings 106 and 768 scanning wirings 104 was formed.

In this example, as the orientation control film 109, the polyamic acid in which the structures of X ₁ and Y _{1 in} the chemical formula (1) are structures shown in Table 1A below, and X ₂ in the chemical formula (2) are the chemical formulas shown above. (X-1), two of four Y _{2 in} the chemical formula (2) are hydrogen atoms, two are methyl groups, and two in the chemical formula (2) A liquid crystal display device was manufactured using an alignment film material in which Z ₂ is a polyamic acid ester having a methyl group and mixed at a ratio (molar ratio) of 50:50. The resin content concentration (alignment film material) is 5% by weight, DMAC 60% by weight, γ-butyrolactone 20% by weight, butyl cellosolve 15% by weight varnish, printed on an active matrix substrate, imidized by heat treatment, A dense alignment control film 109 having a thickness of 130 nm was formed. In the present invention, the imidization rate may be appropriately selected within a range of 25 to 100%. In this example, the imidation ratio of each of the first compound and the second compound is about 90%. Moreover, the average degree of polymerization in the second compound is n = 30, that is, n in the chemical formula (1) includes n = 30.

Similarly, the same polyamic acid amide varnish was printed on the surface of the other glass substrate 102 on which ITO was formed to form an orientation control film 109 made of dense polyimide and polyamic acid having a thickness of about 100 nm. In order to impart liquid crystal alignment ability to the surface, the alignment control film 109 was irradiated with polarized UV (ultraviolet) light. 1. A high pressure mercury lamp is used as a light source, UV light in the range of 240 nm to 320 nm is extracted through an interference filter, and is converted into linearly polarized light having a polarization ratio of about 10: 1 using a pile polarizer with a quartz substrate laminated. Irradiation was performed with an irradiation energy of 0 J / cm ² . As a result, it was found that the alignment direction of the liquid crystal molecules on the surface of the alignment control film was orthogonal to the polarization direction of the irradiated polarized UV light.

  Next, these two glass substrates 101 and 102 are opposed to each other with the surface having the alignment control film 109 having the liquid crystal alignment ability, and spacers made of dispersed spherical polymer beads are interposed therebetween, and the peripheral portion. A sealant was applied to the liquid crystal display panel, and a liquid crystal display panel (hereinafter also referred to as “cell”) to be a liquid crystal display device was assembled. The liquid crystal alignment directions of the two glass substrates 101 and 102 were substantially parallel to each other. This cell has a positive dielectric anisotropy Δε, a value of 10.2 (1 kHz, 20 ° C.), a refractive index anisotropy Δn of 0.075 (wavelength 590 nm, 20 ° C.), and a torsional elastic constant K2. Was 7.0 pN and nematic liquid crystal composition A having a nematic-isotropic phase transition temperature T (N-I) of about 76 ° C. was injected in a vacuum and sealed with a sealing material made of an ultraviolet curable resin. A liquid crystal panel having a liquid crystal layer thickness (gap) of 4.2 μm was produced.

  The retardation (Δn · d) of this liquid crystal display panel is about 0.31 μm. Δn · d is preferably in a range of 0.2 μm ≦ Δn · d ≦ 0.5 μm. If this range is exceeded, there is a problem that white display is colored. Further, a homogeneous alignment liquid crystal display panel was prepared using the same alignment control film and liquid crystal composition used in this panel, and the pretilt angle of the liquid crystal was measured using a crystal rotation method. Showed the degree. This liquid crystal display panel was sandwiched between two polarizing plates 114, and the polarizing transmission axis of one polarizing plate was set substantially parallel to the liquid crystal alignment direction, and the other was arranged so as to be orthogonal thereto. Thereafter, a drive circuit, a backlight, and the like were connected to form a module, and an active matrix liquid crystal display device was obtained. In this embodiment, the normally closed characteristic is such that dark display is performed at a low voltage and bright display is performed at a high voltage.

  Next, when the display quality of the liquid crystal display device according to this example was evaluated, a high-quality display with a contrast ratio of 500 to 1 was confirmed, and a wide viewing angle during halftone display was confirmed.

  In addition, in order to quantitatively measure image sticking and afterimage of the liquid crystal display device according to this example, evaluation was performed using an oscilloscope combined with a photodiode. First, the window pattern is displayed on the screen at the maximum brightness for 100 hours, and then the halftone display in which the afterimage is most noticeable. Here, the entire surface is switched so that the brightness is 10% of the maximum brightness, and the edge of the window pattern is displayed. The time until the pattern disappeared was evaluated as the afterimage disappearance time. However, the allowable afterimage disappearance time is 5 minutes or less.

  The afterimage disappearance time was evaluated for the liquid crystal display device manufactured in this example. The results are shown in Table 1B.

  FIG. 3 is a schematic cross-sectional view of the vicinity of one pixel of the liquid crystal display device according to the second embodiment. FIG. 4A is a schematic plan view of an active matrix substrate showing a configuration in the vicinity of one pixel of the liquid crystal display device according to the second embodiment. FIG. 4B is a cross-sectional view taken along line 4B shown in FIG. 4A. FIG. 4C is a cross-sectional view taken along line 4C shown in FIG. 4A.

  4A and 4B are schematic views of an active matrix substrate for explaining the configuration of the vicinity of one pixel of the liquid crystal display device according to the present embodiment. FIG. 4A is a plan view, and FIG. 4B is a cross section taken along line 4B shown in FIG. 4C shows a cross-sectional view along line 4C in FIG. 4A. 3 corresponds to a part of a cross section taken along line 4B shown in FIG. 4A.

  4B and FIG. 4C schematically show the main part configuration with emphasis, and do not correspond one-to-one with the cut portions of the 4B line and the 4C line in FIG. 4A. For example, the semiconductor film 116 is not shown in FIG. 4B.

  In the present embodiment, a gate electrode 104 made of Cr and a common electrode wiring 120 are arranged on a glass substrate 101 constituting an active matrix substrate, and a gate made of silicon nitride so as to cover the gate electrode 104 and the common electrode wiring 120. An insulating film 107 is formed. A semiconductor film 116 made of amorphous silicon or polysilicon is disposed over the gate electrode 104 with a gate insulating film 107 interposed therebetween, and functions as an active layer of the thin film transistor 115 which is an active element.

Further, a drain electrode 106 made of chromium / molybdenum and a pixel electrode (source electrode) 105 are arranged so as to overlap a part of the pattern of the semiconductor film 116, and a protective insulating film 108 made of silicon nitride is formed so as to cover all of them. Is formed. An organic protective film 112 is disposed on the protective insulating film 108. The organic protective film 112 is made of a transparent material such as an acrylic resin, for example. The pixel electrode 105 is composed of a transparent electrode such as ITO (In ₂ O ₃ : Sn). The common electrode 103 is connected to the common electrode wiring 120 through a through hole 118 that penetrates the gate insulating film 107, the protective insulating film 108, and the organic protective film 112.

  When an electric field for driving the liquid crystal is applied, the common electrode 103 that forms a pair with the pixel electrode 105 is formed so as to surround a region of one pixel in plan view. The common electrode 103 is disposed on the organic protective film 112. The common electrode 103 is disposed so as to hide the drain electrode 106, the scanning wiring 104, and the thin film transistor 115 which is an active element when viewed from above, and includes a light shielding layer that shields the semiconductor film 116 from light. Also serves as.

  On the surface of the glass substrate 101 constituting the active matrix substrate in which the unit pixels (one pixel) configured as described above are arranged in a matrix, that is, on the organic protective film 112 and the common electrode 103 formed thereon. The alignment control film 109 is formed. On the other hand, the alignment control film 109 is also formed on the organic protective film 112 formed on the color filter layer 111 on the glass substrate 102 constituting the counter substrate.

  Here, in the same manner as in Example 1, the alignment control film 109 is provided with liquid crystal alignment ability by irradiation with ultraviolet linearly polarized light extracted using a pile polarizer having a quartz plate laminated using a high-pressure mercury lamp as a light source. ing.

  And the glass substrate 101 and the opposing glass substrate 102 are opposingly arranged by the formation surface of the alignment control film 109, and the liquid crystal composition layer 110b comprised by the liquid crystal molecule 110a is arrange | positioned among these. A polarizing plate 114 is formed on each of the outer surfaces of the glass substrate 101 and the counter glass substrate 102.

  As described above, also in this embodiment, the pixel electrode 105 is disposed under the organic protective film 112 and the protective insulating film 108 as in the first embodiment described above. The common electrode 103 is arranged on the top. Further, when the electric resistance of the common electrode 103 is sufficiently low, the common electrode 103 can also serve as the common electrode wiring 120 formed in the lowermost layer. In that case, the formation of the common electrode wiring 120 arranged in the lowermost layer and the processing of the through hole 118 associated therewith can be omitted.

  In this embodiment, as shown in FIG. 4A, one pixel is formed by a region surrounded by a common electrode 103 formed in a lattice shape, and one pixel is divided into four regions together with the pixel electrode 105. Has been placed. In addition, the pixel electrode 105 and the common electrode 103 facing the pixel electrode 105 have a zigzag bent structure in which the pixel electrode 105 and the common electrode 103 are arranged in parallel with each other, and one pixel forms two or more subpixels. As a result, the color tone change in the plane is offset.

  Next, a method for manufacturing the liquid crystal display device according to this embodiment will be described. As the glass substrates 101 and 102, glass substrates having a thickness of 0.7 mm and polished surfaces are used. The thin film transistor 115 includes a pixel electrode (source electrode) 105, a signal wiring (drain electrode) 106, a scanning wiring (gate electrode) 104, and a semiconductor film 116 made of amorphous silicon. The scanning wiring 104 is patterned with an aluminum film, the common electrode wiring 120 and the signal wiring 106 are patterned with a chrome film, and the pixel electrode 105 is patterned with an ITO film. As shown in FIG. The electrode wiring pattern was bent in a zigzag pattern. At that time, the angle of bending was set to 10 degrees. The gate insulating film 107 and the protective insulating film 108 were made of silicon nitride, and the film thicknesses were each 0.3 μm.

  Next, as shown in FIG. 4C, through holes 118 are formed in a cylindrical shape having a diameter of about 10 μm up to the common electrode wiring 120 by photolithography and etching, and an acrylic resin is applied on the through holes 118 at 220 ° C. The organic protective film 112 having a dielectric constant of about 4 having a dielectric constant of about 4 was formed to a thickness of about 1 μm by heat treatment for 1 hour. The organic protective film 112 flattened the unevenness due to the step of the pixel electrode 105 in the display region, and flattened the unevenness of the step at the boundary portion of the color filter layer 111 between adjacent pixels.

  Thereafter, the through-hole 118 was etched again to a diameter of about 7 μm, and the common electrode 103 connected to the common electrode wiring 120 was formed by patterning the ITO film thereon. At that time, the distance between the pixel electrode 105 and the common electrode 103 was set to 7 μm. Further, the common electrode 103 is formed in a lattice shape so as to cover the upper part of the signal wiring 106, the scanning wiring 104, and the thin film transistor 115 so as to surround the pixel, and also serves as a light shielding layer.

  As a result, in the unit pixel, as shown in FIG. 4A, the pixel electrode 105 is arranged between the three common electrodes 103, and the number of pixels is 1024 × 3 (corresponding to R, G, B). As a result, an active matrix substrate having 1024 × 3 × 768 pieces of the signal wirings 106 and 768 scanning wirings 104 was obtained.

In this example, as the orientation control film 109, the polyamic acid in which the structures of X ₁ and Y _{1 in} the chemical formula (1) are structures shown in the following Table 2A, and X ₂ in the chemical formula (2) are the chemical formulas described above. (X-1) 80 mol%, (X-26) is a structure of 20 mol%, in two places hydrogen atom of _{Y 2} at four positions in the above formula (2), two places is a methyl group In addition, a liquid crystal display device was produced using an alignment film material obtained by mixing the polyamic acid ester in which Z ₂ in the chemical formula (2) is a methyl group at a ratio (molar ratio) of 60:40. The resin content concentration (alignment film material) is 5% by weight, DMAC 60% by weight, γ-butyrolactone 20% by weight, butyl cellosolve 15% by weight varnish, printed on an active matrix substrate, imidized by heat treatment, A dense alignment control film 109 having a thickness of 130 nm was formed. In this example, the imidation ratio of each of the first compound and the second compound is about 90%. Moreover, the average degree of polymerization in the second compound is n = 30, that is, n in the chemical formula (1) includes n = 30.

In the alignment treatment method, the same polarized UV as in Example 1 was irradiated with an irradiation energy of 2.5 J / cm ² .

  Next, a sealant is applied to the peripheral portion of these two glass substrates 101 and 102 with the surfaces having the respective orientation control films facing each other and interposing spacers made of dispersed spherical polymer beads. The liquid crystal display panel was assembled. The liquid crystal alignment directions of the two glass substrates 101 and 102 were substantially parallel to each other.

  This liquid crystal display panel has a positive dielectric anisotropy Δε and a value of 10.2 (1 kHz, 20 ° C.), a refractive index anisotropy Δn of 0.075 (wavelength 590 nm, 20 ° C.), and a torsional elastic constant K2. Was 7.0 pN and nematic liquid crystal composition A having a nematic-isotropic phase transition temperature T (N-I) of about 76 ° C. was injected in a vacuum and sealed with a sealing material made of an ultraviolet curable resin. A liquid crystal panel having a liquid crystal layer thickness (gap) of 4.2 μm was produced. The retardation (Δnd) of this panel is about 0.31 μm.

  Further, a homogeneous alignment liquid crystal display panel was prepared using the same alignment control film and liquid crystal composition used in this liquid crystal display panel, and the pretilt angle of the liquid crystal was measured using the crystal rotation method. . Showed 2 degrees. This panel was sandwiched between two polarizing plates 114, and the polarizing transmission axis of one polarizing plate was set substantially parallel to the liquid crystal alignment direction, and the other was arranged so as to be orthogonal thereto. Thereafter, a drive circuit, a backlight, and the like were connected to form a module, and an active matrix liquid crystal display device was obtained. In this embodiment, the normally closed characteristic is such that dark display is performed at a low voltage and bright display is performed at a high voltage.

  For the liquid crystal display device produced in this example, the afterimage disappearance time was evaluated in the same manner as in Example 1. The results are shown in Table 2B.

  FIG. 5 is a schematic cross-sectional view of the vicinity of one pixel of the liquid crystal display device according to the third embodiment. In the drawing, the same reference numerals as those in the drawings of the respective embodiments described above correspond to the same functional parts. As shown in FIG. 5, in this embodiment, the pixel electrode 105 disposed under the protective insulating film 108 is pulled up on the organic protective film 112 through the through hole 118 and disposed in the same layer as the common electrode 103. In this configuration, the voltage for driving the liquid crystal can be further reduced.

In the TFT liquid crystal display device configured as described above, when no electric field is applied, the liquid crystal molecules 110a constituting the liquid crystal composition layer 110b are in a state substantially parallel to the surfaces of the glass substrates 101 and 102 that are arranged to face each other. Homogenous alignment is performed in a state in which the initial alignment direction defined by the alignment treatment is directed. Here, when a voltage is applied to the gate electrode 104 to turn on the thin film transistor 115, an electric field 117 is applied to the liquid crystal composition layer 110 b due to a potential difference between the pixel electrode 105 and the common electrode 103, and the dielectric property of the liquid crystal composition. Due to the interaction between the anisotropy and the electric field, the liquid crystal molecule 110a changes its direction in the electric field direction. At this time, display can be performed by changing the light transmittance of the liquid crystal display device by the refractive anisotropy of the liquid crystal composition layer 110 b and the action of the polarizing plate 114.

  Hereinafter, a method for manufacturing the liquid crystal display device according to this embodiment will be described. As the glass substrates 101 and 102, glass substrates having a thickness of 0.7 mm and polished surfaces are used. The thin film transistor 115 includes a pixel electrode (source electrode) 105, a signal wiring (drain electrode) 106, a scanning wiring (gate electrode) 104, and a semiconductor film 116 made of amorphous silicon. The scanning wiring 104 was formed by patterning an aluminum film, and the common electrode wiring 120, the signal wiring 106, and the pixel electrode 105 were formed by patterning a chromium film. The gate insulating film 107 and the protective insulating film 108 were made of silicon nitride, and the film thicknesses were each 0.3 μm. An acrylic resin was applied thereon, and a transparent and insulating organic protective film 112 having a dielectric constant of about 4 was formed to a thickness of about 1.0 μm by heat treatment at 220 ° C. for 1 hour. The organic protective film 112 flattened the unevenness due to the step of the pixel electrode 105 in the display area, and flattened the unevenness between the adjacent pixels.

  Next, as shown in FIG. 5, through holes 118 are formed in a cylindrical shape with a diameter of about 10 μm up to the source electrode 105 by photolithography and etching, and the pixel electrode 105 connected to the source electrode 105 is formed thereon. An ITO film was formed by patterning. The common electrode wiring 120 was also formed with a through hole 118 in a cylindrical shape having a diameter of about 10 μm, and the ITO film was patterned thereon to form the common electrode 103. At that time, the interval between the pixel electrode 105 and the common electrode 103 was set to 7 μm, and the electrode wiring pattern other than the scanning wiring 104 was formed in a zigzag bent electrode wiring pattern. At that time, the angle of bending was set to 10 degrees. Further, the common electrode 103 is formed in a lattice shape so as to cover the upper portion of the signal wiring 106, the scanning wiring 104, and the thin film transistor 115 so as to surround the pixel, and also serves as a light shielding layer.

  As a result, except that two types of through holes 118 are formed in the unit pixel, the pixel electrode 105 is disposed between the three common electrodes 103 in substantially the same manner as in the second embodiment. An active matrix substrate having 1024 × 3 × 768 lines composed of 1024 × 3 (corresponding to R, G, and B) signal wirings 106 and 768 scanning wirings 104 was formed.

  As described above, a liquid crystal display device was manufactured as shown in FIG. 5 in the same manner as in Example 2 except for the pixel structure and the alignment control film to be used.

In this example, as the orientation control film 109, the polyamic acid in which the structures of X ₁ and Y _{1 in} the chemical formula (1) are structures shown in the following Table 3A, and X ₂ in the chemical formula (2) are The chemical formula (X-16) has a structure of 30 mol% and (X-25) 70 mol%, 3 of 4 Y _{2 in} the chemical formula (2) are hydrogen atoms, and 1 site is A liquid crystal display device was prepared using an alignment film material in which a methyl group and a polyamic acid ester in which _two Z ₂ in the chemical formula (2) are t-butyl groups were mixed at a ratio of 20:80. The resin content concentration (alignment film material) is 5% by weight, DMAC 60% by weight, γ-butyrolactone 20% by weight, butyl cellosolve 15% by weight varnish, printed on an active matrix substrate, imidized by heat treatment, A dense alignment control film 109 having a thickness of 130 nm was formed. In this example, the imidation ratio of each of the first compound and the second compound is about 90%. Moreover, the average degree of polymerization in the second compound is n = 30, that is, n in the chemical formula (1) includes n = 30.

In the alignment treatment method, the same polarized UV as in Example 1 was irradiated with an irradiation energy of 2.5 J / cm ² .

  For the liquid crystal display device produced in this example, the afterimage disappearance time was evaluated in the same manner as in Example 1. The results are shown in Table 3B.

  FIG. 6 is a schematic cross-sectional view of the vicinity of one pixel of the liquid crystal display device according to the fourth embodiment. In the drawing, the same reference numerals as those in the drawings of the respective embodiments described above correspond to the same functional parts. In this embodiment, a structure having a large step due to an electrode or the like is employed. In FIG. 6, the gate electrode 104 and the common electrode 103 of the thin film transistor 115 are formed in the same layer, and the liquid crystal molecules 110 a change the direction of the electric field due to the electric field 117 generated by the common electrode 103 and the pixel electrode 105.

  Further, in each of the above-described embodiments, a plurality of display areas each including the common electrode 103 and the pixel electrode 105 in one pixel can be provided. In this manner, by providing a plurality of sets, even when one pixel is large, the distance between the pixel electrode 105 and the common electrode 103 can be shortened, so that the voltage applied to drive the liquid crystal can be reduced.

  In each of the embodiments described above, the material of the transparent conductive film constituting at least one of the pixel electrode and the common electrode is not particularly limited, but considering the ease of processing, high reliability, and the like. It is desirable to use a transparent conductive film ion-doped with titanium oxide such as indium tin oxide (ITO) or ion-doped zinc oxide.

  In the method for manufacturing a liquid crystal display device according to this embodiment, glass substrates 101 and 102 are glass substrates having a thickness of 0.7 mm and polished surfaces. The thin film transistor 115 includes a pixel electrode (source electrode) 105, a signal wiring (drain electrode) 106, a scanning wiring (gate electrode) 104, and a semiconductor film 116 made of amorphous silicon. The scanning wiring 104, the common electrode wiring 120, the signal wiring 106, the pixel electrode 105, and the common electrode 103 were all formed by patterning a chromium film, and the distance between the pixel electrode 105 and the common electrode 103 was 7 μm. The gate insulating film 107 and the protective insulating film 108 were made of silicon nitride, and the film thicknesses were each 0.3 μm.

In this example, as the orientation control film 109, polyamic acid in which the structures of X ₁ and Y _{1 in} the chemical formula (1) are structures shown in Table 4A below, and X ₂ in the chemical formula (2) are the chemical formulas described above. (X-1) 90 mol%, (X-33) (provided that m = 3) 10 mol%, and two of the four Y _{2 in} the chemical formula (2) are hydrogen atoms. Yes, a liquid crystal display device is manufactured using an alignment film material in which polyamic acid esters in which two places are methyl groups and Z ₂ in the chemical formula (2) is a methyl group are mixed in a ratio of 80:20 did. The resin content concentration (alignment film material) is 5% by weight, DMAC 60% by weight, γ-butyrolactone 20% by weight, butyl cellosolve 15% by weight varnish, printed on an active matrix substrate, imidized by heat treatment, A dense alignment control film 109 having a thickness of 130 nm was formed. In this example, the imidation ratio of each of the first compound and the second compound is about 90%. Moreover, the average degree of polymerization in the second compound is n = 30, that is, n in the chemical formula (1) includes n = 30.

In the alignment treatment method, the same polarized UV as in Example 1 was irradiated with an irradiation energy of 2.5 J / cm ² . As a result, an active matrix substrate having 1024 × 3 × 768 pixels composed of 1024 × 3 (corresponding to R, G, and B) signal wirings 106 and 768 scanning wirings 104 was formed. .

  As described above, the liquid crystal display device of this example shown in FIG. 6 was manufactured in the same manner as Example 1 except for the pixel structure.

  For the liquid crystal display device produced in this example, the afterimage disappearance time was evaluated in the same manner as in Example 1. The results are shown in Table 4B.

  FIG. 7 is a schematic cross-sectional view of the vicinity of one pixel of the liquid crystal display device according to the fifth embodiment. In the drawing, the same reference numerals as those in the drawings of the respective embodiments described above correspond to the same functional parts. In this embodiment, the pixel electrode 105 and the common electrode 103 are made of ITO, and the common electrode 103 is a solid electrode that covers almost the entire pixel. With this configuration, the electrode can be used as a transmission portion, and the aperture ratio can be improved. In addition, the distance between the electrodes can be shortened, and an electric field can be efficiently applied to the liquid crystal.

  FIG. 8 is a schematic plan view of an active matrix substrate showing a configuration in the vicinity of one pixel of the liquid crystal display device according to the fifth embodiment, and shows the structure of the thin film transistor 115, the common electrode 103, the pixel electrode 105, and the signal wiring 106.

  In the method for manufacturing a liquid crystal display device according to this example, a glass substrate having a thickness of 0.7 mm and a polished surface is used as the glass substrate 101. On the glass substrate 101, a gate insulating film 107 for preventing a short circuit between the common electrode 103, the pixel electrode 105, the signal wiring 106, and the scanning wiring 104, and protective insulation for protecting the thin film transistor 115, the pixel electrode 105, and the signal wiring 106. A film 108 is formed to form a TFT substrate.

  The thin film transistor 115 includes a pixel electrode (source electrode) 105, a signal wiring (drain electrode) 106, a scanning wiring (gate electrode) 104, and a semiconductor film 116 made of amorphous silicon. The scanning wiring (gate electrode) 104 is formed by patterning an aluminum film, the signal wiring (drain electrode) 106 is formed by patterning a chromium film, and the common electrode 103 and the pixel electrode 105 are formed by patterning ITO.

  The gate insulating film 107 and the protective insulating film 108 were made of silicon nitride, and the film thicknesses were 0.2 μm and 0.3 μm, respectively. The capacitor is formed to have a structure in which the gate insulating film 107 and the protective insulating film 108 are sandwiched between the pixel electrode 105 and the common electrode 103.

  The pixel electrode 105 is arranged so as to overlap the upper layer of the solid-shaped common electrode 103. The number of pixels is 1024 × 3 × 768 including 1024 × 3 (corresponding to R, G, and B) signal wirings 106 and 768 scanning wirings 104.

  On the glass substrate 102, the color filter layer 111 with the black matrix 113 was formed similarly to Example 1, and it was set as the counter color filter substrate.

In this example, as the orientation control film 109, the polyamic acid in which the structures of X ₁ and Y _{1 in} the chemical formula (1) are structures shown in the following Table 5A, and X ₂ in the chemical formula (2) are the chemical formulas described above. (X-1) 75 mol%, (X-31) (provided that m = 2) 25 mol%, and two of the four Y _{2 in} the chemical formula (2) are hydrogen atoms, A liquid crystal display device was produced using an alignment film material in which the polyamic acid ester in which two places were methyl groups and Z ₂ in the chemical formula (2) was a methyl group was mixed at a ratio of 50:50. The resin content concentration (alignment film material) is 5% by weight, DMAC 60% by weight, γ-butyrolactone 20% by weight, butyl cellosolve 15% by weight varnish, printed on an active matrix substrate, imidized by heat treatment, A dense alignment control film 109 having a thickness of 130 nm was formed. In this example, the imidation ratio of each of the first compound and the second compound is about 90%. Moreover, the average degree of polymerization in the second compound is n = 30, that is, n in the chemical formula (1) includes n = 30.

  Similarly, a similar orientation control film 109 was formed on the surface of the other glass substrate 102 on which ITO was formed.

In the alignment treatment method, the same polarized UV as in Example 1 was irradiated with an irradiation energy of 2.5 J / cm ² .

  The alignment directions of the alignment control film 109 on the TFT substrate and the color filter substrate are substantially parallel to each other. Polymer beads having an average particle diameter of 4 μm were dispersed as spacers between these substrates, and liquid crystal molecules 110a were sandwiched between the TFT substrate and the color filter substrate. The same liquid crystal composition A as in Example 1 was used as the liquid crystal molecules 110a.

  The two polarizing plates 114 sandwiching the TFT substrate and the color filter substrate were arranged in crossed Nicols. A normally closed characteristic is adopted in which a dark state is obtained at a low voltage and a bright state is obtained at a high voltage.

  For the liquid crystal display device produced in this example, the afterimage disappearance time was evaluated in the same manner as in Example 1. The results are shown in Table 5B.

  101, 102 glass substrate, 103 common electrode (common electrode), 104 scanning wiring (gate electrode), 105 pixel electrode (source electrode), 106 signal wiring (drain electrode), 107 gate insulating film, 108 protective insulating film, 109 orientation Control film, 110a liquid crystal molecule, 110b liquid crystal layer (liquid crystal composition layer), 111 color filter layer, 112 overcoat layer (organic protective film), 113 light shielding film (black matrix), 114 polarizing plate, 115 thin film transistor (TFT), 116 Semiconductor film (amorphous silicon or polysilicon), 117 electric field (electric field direction), 118 through hole, 120 common electrode wiring (common wiring).

Claims (6)

A first substrate and a second substrate, at least one of which is transparent; a liquid crystal layer disposed between the first substrate and the second substrate; the first substrate and the second substrate; An electrode group for applying an electric field to the liquid crystal layer, a plurality of active elements connected to the electrode group, the first substrate, and the second substrate. In a liquid crystal display device comprising an alignment film disposed on at least one substrate,
The alignment layer comprises a polyimide and a second compound which is the first compound and the polyamic acid is a Polyamide ester precursor,
The chemical structure of the second compound is represented by the following formula (1).

(However, n is an integer of 10 to 10000, each X ₁ is a divalent organic group, and each Y ₁ is a tetravalent organic group that does not contain a cyclobutane structure in the structure. 30% or more and 90% or less of Y _{1 is} a tetravalent organic group containing at least one aromatic group in the structure.
In addition, among Y ₁ contained in the chemical structure of the second compound, the tetravalent organic group containing the aromatic group is independently selected from the compounds shown in the following compound group A This is a tetravalent organic group of the compound.

(However, A ₁ is each independently an alkylene group having 2 or 3 carbon atoms, —CR ₂ —, —COO—, —NR—, —NH—CO—, —S—, —SO—, —Si—, and, -SiR ₂ -, a structure selected from,
Each R contained in A ₁ is independently selected from hydrogen (except for the case of R in —CR ₂ —), an alkyl group having 1 to 8 carbon atoms, and a fluoroalkyl group having 1 to 8 carbon atoms. The hydrogen atom bonded to the aromatic group is independently an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluoroalkyl group having 1 to 3 carbon atoms, or a carbon number. It is substituted with 1 to 3 fluoroalkoxy groups, a fluorine atom, a chlorine atom, or a bromine atom, or unsubstituted. ))   The alignment film includes: a total of polyimides using the first compound and the first compound as a precursor; and a total of polyimides using the second compound and the second compound as a precursor. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is contained in a molar ratio of 80 to 80:20. 3. The liquid crystal display device according to claim 1, wherein 50% or more of each X ₁ is a divalent organic group containing at least one aromatic group in the structure.   4. The liquid crystal display device according to claim 1, wherein the first compound is formed using a cyclobutanetetracarboxylic dianhydride derivative and an aromatic diamine. 5. A liquid crystal alignment film comprising a polyimide and a precursor of the polyimide,
The polyimide precursor includes a first compound that is a polyamic acid ester and a second compound that is a polyamic acid,
The chemical structure of said 2nd compound is shown by following formula (1), The liquid crystal aligning film characterized by the above-mentioned.

(However, n is an integer of 10 to 10000, each X ₁ is a divalent organic group, and each Y ₁ is a tetravalent organic group that does not contain a cyclobutane structure in the structure. 30% or more and 90% or less of Y _{1 is} a tetravalent organic group containing at least one aromatic group in the structure.
In addition, among Y ₁ contained in the chemical structure of the second compound, the tetravalent organic group containing the aromatic group is independently selected from the compounds shown in the following compound group A This is a tetravalent organic group of the compound.

(However, A ₁ is each independently an alkylene group having 2 or 3 carbon atoms, —CR ₂ —, —COO—, —NR—, —NH—CO—, —S—, —SO—, —Si—, and, -SiR ₂ -, a structure selected from,
Each R contained in A ₁ is independently selected from hydrogen (except for the case of R in —CR ₂ —), an alkyl group having 1 to 8 carbon atoms, and a fluoroalkyl group having 1 to 8 carbon atoms. The hydrogen atom bonded to the aromatic group is independently an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluoroalkyl group having 1 to 3 carbon atoms, or a carbon number. It is substituted with 1 to 3 fluoroalkoxy groups, a fluorine atom, a chlorine atom, or a bromine atom, or unsubstituted. )) A composition for forming a liquid crystal alignment film, which forms an alignment film containing polyimide and a precursor of the polyimide,
The polyimide precursor includes a first compound that is a polyamic acid ester and a second compound that is a polyamic acid,
The chemical structure of said 2nd compound is shown by following formula (1), The composition for liquid crystal aligning film formation characterized by the above-mentioned.

(However, n is an integer of 10 to 10000, each X ₁ is a divalent organic group, and each Y ₁ is a tetravalent organic group that does not contain a cyclobutane structure in the structure. 30% or more and 90% or less of Y _{1 is} a tetravalent organic group containing at least one aromatic group in the structure.
In addition, among Y ₁ contained in the chemical structure of the second compound, the tetravalent organic group containing the aromatic group is independently selected from the compounds shown in the following compound group A This is a tetravalent organic group of the compound.

(However, A ₁ is each independently an alkylene group having 2 or 3 carbon atoms, —CR ₂ —, —COO—, —NR—, —NH—CO—, —S—, —SO—, —Si—, and, -SiR ₂ -, a structure selected from,
Each R contained in A ₁ is independently selected from hydrogen (except for the case of R in —CR ₂ —), an alkyl group having 1 to 8 carbon atoms, and a fluoroalkyl group having 1 to 8 carbon atoms. The hydrogen atom bonded to the aromatic group is independently an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluoroalkyl group having 1 to 3 carbon atoms, or a carbon number. It is substituted with 1 to 3 fluoroalkoxy groups, a fluorine atom, a chlorine atom, or a bromine atom, or unsubstituted. ))

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