JP2006171206A - Liquid crystal alignment substrate and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal alignment substrate by which display of high quality is made possible and to provide a liquid crystal display provided with the same. <P>SOLUTION: The liquid crystal alignment substrate has a substrate 2, a transparent conductive layer 4 provided on the substrate 2 and a conductive resin layer 3 provided on the transparent conductive layer 4 and aligning liquid crystal molecules in a prescribed direction. The conductive resin layer 3 has ≤2.4×10<SP>8</SP>Ωcm electric resistivity in the range of 0.1 to 5 μm thickness of the conductive resin layer 3. A projecting and recessed structure aligning the liquid crystal molecules in the prescribed direction is formed on the surface of the conductive resin layer 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal alignment substrate and a liquid crystal display device that enable high-quality display.

  Liquid crystal display devices are widely used in office automation equipment such as personal computer monitors, televisions, and the like because of their low voltage, low power consumption, thinness, and light weight. Various liquid crystal display devices are known. For example, a twisted nematic (TN) liquid crystal display device in which the alignment treatment direction of liquid crystal molecules is twisted by 90 ° between two substrates, and nematic liquid crystal molecules are attached to the substrate. On the other hand, vertical alignment (VA) liquid crystal display devices that are vertically aligned, in-plane switching (IPS) liquid crystal display devices in which nematic liquid crystal molecules are horizontally aligned with respect to a substrate, and the like have been put into practical use. Furthermore, a ferroelectric liquid crystal display device in which chiral smectic liquid crystal molecules are aligned in parallel to the substrate has been proposed.

  Among these liquid crystal display devices, in TN liquid crystal display devices, IPS liquid crystal display devices, and ferroelectric liquid crystal display devices, liquid crystal molecules are aligned in a desired direction by an alignment treatment, and light rotation based on the aligned liquid crystal molecules is performed. Display is possible using the property or birefringence. As a method for aligning the liquid crystal, a polyimide resin is applied on a substrate on which a transparent conductive layer as an electrode is formed and cured to form a resin layer, and then the surface of the resin layer is rubbed with a desired direction. And a rubbing method of imparting alignment regulating force by rubbing to the substrate, and after forming a photosensitive resin layer on the substrate, the photosensitive resin layer is irradiated with polarized light or non-polarized light in the polarization direction or the light incident direction. There is known a photo-alignment method in which an alignment regulating force is given in correlation.

  However, in the rubbing method, a rubbing cloth made of nylon resin or vinyl resin fibers is wound around a rubbing roller and the surface of the resin layer is mechanically rubbed with the rubbing cloth wound around the rubbing roller. There is a problem that fine dust or the like is generated from the display, and the display quality deteriorates due to the dust or the like. In particular, in the ferroelectric liquid crystal display device, the thickness of the ferroelectric liquid crystal layer sealed between the two substrates is 1 μm to 2 μm, and the gap between the two substrates is narrower than that of the nematic liquid crystal, that is, Because of the narrow gap, there arises a problem that dust or the like generated from the rubbing cloth or a scratch on the surface of the resin layer caused by rubbing tends to adversely affect the display as compared with the case of nematic liquid crystal. On the other hand, the photo-alignment method does not generate fine dust unlike the rubbing method because UV irradiation is performed in a non-contact state, so that there is a merit that a good display quality can be obtained. The stage has not been reached.

In addition to the rubbing method and the photo-alignment method, a method of aligning liquid crystal molecules in a desired direction by forming a concavo-convex structure on the surface of the resin layer has been proposed (see, for example, Patent Documents 1 and 2). . Patent Document 1 discloses that the alignment direction of nematic liquid crystal molecules is regulated by forming a large number of grooves whose axial directions are substantially parallel to the surface of the resin layer. Patent Document 2 discloses that the liquid crystal molecules of a ferroelectric liquid crystal having a chiral smectic C phase are aligned in a desired direction by an uneven structure having a specific angle on the surface of the resin layer.
JP-A-8-262445 JP-A-5-249465

  In the methods described in Patent Documents 1 and 2 described above, it is possible to align liquid crystal molecules in a desired direction by forming an uneven structure on the surface of the resin layer, but the resin layer is thick. turn into. That is, the concavo-convex structure on the surface of the resin layer is formed by pressing a mold member having a large number of protrusions on an uncured resin layer, but when the mold member is pressed against the resin layer, the thickness of the resin layer If the thickness is not so large, the uneven structure cannot be formed by pressing the mold member, and therefore the resin layer has a thickness of 0.1 μm or more. When the resin layer is thick, a voltage is applied to control the molecular arrangement of the liquid crystal layer sandwiched between the substrates by applying a predetermined voltage to the electrodes formed on the two substrates constituting the liquid crystal display device. May be divided between the liquid crystal layer and the resin layer, causing a problem that the voltage applied to the liquid crystal layer is reduced and the contrast may be lowered.

  In particular, a ferroelectric liquid crystal display device drives a liquid crystal layer by a TFT element. If the resin layer has a certain thickness or more during driving, the liquid crystal layer is sufficiently formed within the gate writing time of the TFT element. In some cases, the contrast is lowered and the display quality is lowered without application of voltage.

  The present invention has been made to solve the above-described problems, and a first object thereof is to provide a liquid crystal alignment substrate capable of high-quality display. The second object of the present invention is to provide a liquid crystal display device comprising such a liquid crystal alignment substrate.

  As a result of studying a liquid crystal alignment substrate that can satisfactorily drive the liquid crystal layer while considering various parameters constituting the liquid crystal alignment substrate, the present inventor has found that the conductive resin layer has a predetermined electric resistance at a predetermined thickness. It has been found that the liquid crystal display device can operate at high contrast when the ratio is less than the ratio.

That is, the liquid crystal alignment substrate of the present invention that achieves the first object is a substrate, a transparent conductive layer provided on the substrate, and a liquid crystal molecule provided on the transparent conductive layer to align liquid crystal molecules in a predetermined direction. A liquid crystal alignment substrate having a conductive resin layer, wherein the conductive resin layer has an electrical resistivity ρ _AF of 2.4 × when the thickness of the conductive resin layer is in the range of 0.1 μm to 5 μm. 10 ⁸ Ωcm or less.

According to the present invention, since the conductive resin layer having an electrical resistivity ρ _AF of 2.4 × 10 ⁸ Ωcm or less is provided in the thickness range of 0.1 μm or more and 5 μm or less, a sufficient voltage is applied to the liquid crystal layer. In addition, the contrast is unlikely to decrease. As a result, the liquid crystal display device can be operated with high contrast, and high-quality display can be performed.

  It is preferable that an uneven structure for aligning liquid crystal molecules in a predetermined direction is formed on the surface of the conductive resin layer in the liquid crystal alignment substrate of the present invention.

In the liquid crystal display device of the present invention that achieves the second object, one or both of the liquid crystal alignment substrate and the liquid crystal driving substrate are a substrate, a transparent conductive layer provided on the substrate, and the transparent conductive layer. And a conductive resin layer that aligns liquid crystal molecules in a predetermined direction, and the electrical resistivity ρ _AF of the conductive resin layer satisfies the relationship of Formula 1.

In Formula 1, ε _AF is a range of 2 to 10 in terms of relative dielectric constant of the conductive resin layer, ε _LC is in a range of 2 to 10 in terms of relative permittivity of the liquid crystal layer, and d _AF is a range of conductive resin. The layer thickness is in the range of 0.1 μm to 5 μm, d _LC is the liquid crystal layer thickness in the range of 0.5 μm to 10 μm, and L is the number of scanning lines of the liquid crystal display device of 2400 or less. Range.

According to the present invention, since the electrical resistivity ρ _AF of the conductive resin layer satisfies the relationship of Formula 1, a sufficient voltage is applied to the liquid crystal layer, and the contrast is hardly lowered. As a result, the liquid crystal display device can be operated with high contrast, and high-quality display can be performed.

  Moreover, it is preferable that the concavo-convex structure for aligning liquid crystal molecules in a predetermined direction is formed on the surface of the conductive resin layer.

According to the liquid crystal alignment substrate and the liquid crystal display device of the present invention, since the electrical resistivity ρ _AF is 2.4 × 10 ⁸ Ωcm or less in the thickness range of 0.1 μm or more and 5 μm or less, A voltage is sufficiently applied to the liquid crystal layer, the liquid crystal display device can be operated with high contrast, and high-quality display can be performed.

  Hereinafter, a liquid crystal alignment substrate and a liquid crystal display device of the present invention will be described with reference to the drawings.

(Liquid crystal alignment substrate)
FIG. 1 is a schematic sectional view showing an example of the liquid crystal alignment substrate of the present invention. As shown in FIG. 1, the liquid crystal alignment substrate 1 of the present invention is provided with a substrate 2, a transparent conductive layer 4 provided on the substrate 2, a transparent conductive layer 4, and liquid crystal molecules in a predetermined direction. The conductive resin layer 3 is oriented at least, and the conductive resin layer 3 has an electrical resistivity ρ _AF of 2.4 when the thickness of the conductive resin layer 3 is 0.1 μm or more and 5 μm or less. It is characterized by being 10 ⁸ Ωcm or less. If a liquid crystal display device is configured using the liquid crystal alignment substrate 1, the liquid crystal display device can be operated with high contrast. In FIG. 1, reference numeral 7 denotes a color filter. When the liquid crystal alignment substrate of the present invention is used as a color filter substrate, as shown in FIG. 1, between the substrate 2 and the transparent conductive layer 4 A color filter 7 can be provided. On the other hand, when the liquid crystal alignment substrate of the present invention is used as a liquid crystal driving substrate, the color filter 7 as shown in FIG. 1 is not necessarily provided.

  The substrate 2 is a rigid material having no flexibility such as quartz glass, Pyrex (registered trademark) glass, or synthetic quartz plate, depending on whether the substrate is applied to a color filter or a liquid crystal driving substrate. A flexible flexible material such as a transparent resin film or an optical resin plate can be used, and a resin substrate that is light and difficult to break is particularly preferable. The resin substrate may be a sheet or film. Although it does not specifically limit as a manufacturing method of the board | substrate 2, For example, when manufacturing a plastic substrate, a roll method etc. are mentioned. The thickness of the substrate 2 varies depending on the liquid crystal display device to which the liquid crystal alignment substrate 1 is mounted. For example, in the case of a transparent rigid material having no plasticity, the thickness is about 0.5 to 1.1 mm and has plasticity. In the case of a transparent resin substrate, it is about 0.1 mm to 0.7 mm.

  The transparent conductive layer 4 is formed using, for example, indium tin oxide (ITO), zinc oxide (ZnO), tin oxide (SnO), or an alloy thereof. The thickness of the transparent conductive layer 4 is, for example, about 0.01 μm to 2 μm, preferably about 0.03 μm to 1.5 μm. The transparent conductive layer 4 can be formed by a general film forming method such as a sputtering method, a vacuum deposition method, a CVD method or the like.

  When the liquid crystal alignment substrate of the present invention is used as a color filter substrate, a color filter 7 may be provided between the substrate 2 and the transparent conductive layer 4. The color filter 7 is, for example, a red color filter formed by a red (R) color resin that transmits light corresponding to the three primary colors of RGB light, and a green color filter formed by a green (G) color resin. And a blue color filter formed of a blue (B) color resin are alternately arranged in a stripe shape. The thickness of the color filter 7 is not particularly limited, but is preferably about 0.5 μm to 5 μm, and particularly preferably about 1 μm to 3 μm. The color filter 7 can be formed by any one of a pigment dispersion method, a dyeing method, an electrodeposition method, and a printing method.

The conductive resin layer 3 aligns liquid crystal molecules in a predetermined direction, and has an electrical resistivity ρ _AF of 2.4 × 10 ⁸ Ωcm or less in a thickness range of 0.1 μm to 5 μm. . The method for producing the conductive resin layer 3 is not particularly limited, and a conductive resin layer that has been subjected to an alignment treatment by a rubbing method, a photo-alignment method, or the like may be used, and hydrophobicity or hydrophilicity may be used. A conductive resin layer that aligns liquid crystal molecules in a predetermined direction may be used, but a conductive resin layer having a concavo-convex structure formed on the surface is preferable. The shape of the concavo-convex structure is not particularly limited as long as the liquid crystal molecules can be aligned in a desired direction, and for example, a grating in which grooves or wall structures are periodically formed in a certain direction may be used.

  The concavo-convex structure is formed under conditions that allow liquid crystal molecules to be aligned in a desired direction. The conditions are not generally determined by the liquid crystal display device or the like on which the liquid crystal alignment substrate 1 is mounted. For example, the width w1 of the convex portion is about 0.1 μm to 5 μm, and the width w2 of the concave portion is 0.1 μm. It is preferable that the ratio (w1 / w2) between the width w1 of the convex portion and the width w2 of the concave portion is in the range of 0.1 to 10. Moreover, it is preferable that the depth w3 of a recessed part is about 0.1 micrometer-5 micrometers. When the width w1 of the convex portion is less than 0.1 μm, it may be difficult to form a concavo-convex structure, and when the width w1 of the convex portion exceeds 5 μm, the liquid crystal alignment regulating force does not work and the alignment of liquid crystal molecules is disturbed. Sometimes. If the width w2 of the recess is less than 0.1 μm, it may be difficult to form a concavo-convex structure, and if the width w2 of the recess exceeds 5 μm, the liquid crystal alignment regulating force does not work and the alignment of liquid crystal molecules may be disturbed. is there. When the ratio (w1 / w2) of the width w1 of the convex portion to the width w2 of the concave portion is less than 0.5, the alignment of the liquid crystal molecules may be disturbed, and when the ratio w exceeds 10, the alignment of the liquid crystal molecules May be disturbed, making uniform alignment difficult. If the depth w3 of the recess is less than 0.1 μm, the liquid crystal molecules may not be correctly aligned. If the depth w3 of the recess exceeds 5 μm, the thickness of the conductive resin layer increases. The effective voltage applied to the light is reduced, and the contrast of light and dark may be lowered.

The conductive resin layer 3 has a material constituting the main component and a conductive material having conductivity, and can further contain an additive material such as a release agent. The conductive resin layer 3 may be mainly composed of a conductive material having conductivity. Examples of the material constituting the main component having no conductivity include an ultraviolet curable resin, a thermoplastic resin, etc. Among them, an ultraviolet curable resin is preferable, and the formation of a concavo-convex structure in an uncured state is particularly preferable. A solvent-containing ultraviolet curable resin is preferable because it becomes easier. Examples of the conductive material include conductive polymers such as polyaniline, polypyrrole, and polythiophene, fine powder ITO (Indium Tin Oxide), Sb ₂ O ₅ (Antimony Oxide), PTO (Phosphorous doped Tin Oxide), and ATO (Antimony doped Tin Oxide). Among them, conductive polymers and finely powdered ITO are preferable. These materials are blended and mixed with the material constituting the main component so that the electrical resistivity ρ _AF is 2.4 × 10 ⁸ Ωcm or less, for example. The content of the conductive material may be various depending on the material constituting the main component and the conductive material. For example, the content is preferably 3% or more based on the total amount of the conductive resin layer 3. When the content of the conductive material is less than 3%, the electrical resistivity ρ _AF of the conductive resin layer 3 may become too large. The conductive material is dispersed and mixed in the ultraviolet curable resin with, for example, a stirrer.

  The conductive resin layer 3 can be formed by a known method such as a printing method or a transfer method. The uneven structure on the surface of the conductive resin layer 3 can be formed by a photolithographic process method, mold transfer, or the like. The formation of the conductive resin layer 3 and the formation of the concavo-convex structure can be performed by, for example, mold transfer.

  Next, the case where the conductive resin layer 3 and the concavo-convex structure are formed by mold transfer, that is, the case where the liquid crystal alignment substrate of the present invention is formed will be described in detail.

  FIG. 2 is a process diagram showing an example of a method for forming a liquid crystal alignment substrate of the present invention. As shown in FIG. 2, first, a mask plate (a master mold member having a fine uneven structure) 41 having a large number of recesses 42 is produced. Further, a layer of a photosensitive monomer such as an ultraviolet curable resin layer 44 is formed on the transparent film 43. The concave portion 42 of the mask plate 41 is opposed to the ultraviolet curable resin layer 44 of the transparent film 43 (FIG. 2A). The mask plate 41 can be produced by an electron beam irradiation (EB) method or an optical method. Specifically, the mask plate 41 is manufactured by the EB method by designing and manufacturing a concavo-convex pattern of the concavo-convex structure formed in advance on the conductive resin layer 3 as graphic data, and a beam diameter of 0.1 μm to 0.2 μm. It can be produced by drawing on a photosensitive resin with an electron beam drawing apparatus having

  Next, the concave portion 42 of the mask plate 41 is pressed against the surface of the ultraviolet curable resin layer 44. In the pressed state, ultraviolet rays (UV) are irradiated from the transparent film 43 side toward the ultraviolet curable resin layer 44 to cure the ultraviolet curable resin layer 44 (FIG. 2B). After curing, the mask plate 41 is peeled from the ultraviolet curable resin layer 44 (transparent film 43), thereby forming a mold member 46 having a large number of convex portions 45 formed on the surface of the ultraviolet curable resin layer 44 (see FIG. FIG. 2 (c)).

  Next, the color filter 7 and the transparent conductive layer 4 are sequentially formed on the substrate 2, and a solvent-containing ultraviolet curable resin is applied on the transparent conductive layer 4 to form the conductive resin layer 3 (FIG. 2). (D)). By heating the substrate 2 (conductive resin layer 3) to remove the solvent from the conductive resin layer 3, the conductive resin layer 3 is brought into a non-flowing uncured state. Then, the mold member 46 is pressed against the conductive resin layer 3. The pressing is performed so that the convex portion 45 of the ultraviolet curable resin layer 44 contacts the conductive resin layer 3. The conductive resin layer 3 is completely cured by irradiating ultraviolet rays (UV) toward the conductive resin layer 3 from the substrate 2 side in the pressed state. After curing, the mold member 46 is peeled from the conductive resin layer 3 to obtain the liquid crystal alignment substrate 1 of the present invention in which the concave portion 5 is formed on the surface of the conductive resin layer 3 (an uneven structure is formed). .

  The mold member 46 was manufactured using the mask plate 41. This is because the conductive resin layer 3 and the mold member 46 are more closely adhered to each other, and the mask plate is formed every time one liquid crystal alignment substrate is manufactured. This is to eliminate the need for cleaning. However, when the uncured conductive resin layer 3 has fluidity, the mask plate 41 can also be used as a direct mold member. Further, in order to enhance the mutual adhesion of the substrate 2, the transparent conductive layer 4, the conductive resin layer 3, and the color filter 7, the silane coupling agent is preliminarily applied to the substrate 2 or the transparent conductive layer before the conductive resin layer 3 is formed. It may be applied to the layer 4 or the like. The color filter 7 can be omitted in the case where a full color display can be obtained by lighting a backlight such as an LED of each RGB color sequentially.

Thus, the conductive resin layer 3 having a concavo-convex structure on the surface has an electrical resistivity ρ _AF of 2.4 × 10 ⁸ Ωcm or less in a thickness range of 0.1 μm to 5 μm. It is. In the example shown in FIG. 1, the thickness of the conductive resin layer 3 in the present invention means the length from the surface in contact with the transparent conductive layer 4 to the tip of the convex portion 6. In this case, if the thickness of the conductive resin layer 3 is 0.1 μm or less, it may be difficult to form a concavo-convex structure. If the thickness of the conductive resin layer 3 exceeds 5 μm, the conductive resin layer 3 The flatness of the liquid crystal may be lost, making it difficult to align liquid crystal molecules in a desired direction. Finally, when the electrical resistivity ρ _AF of the conductive resin layer 3 exceeds 2.4 × 10 ⁸ Ωcm, the voltage applied to the liquid crystal layer may decrease and the contrast may decrease. More specifically, it is preferable that the electrical resistivity ρ _AF of the conductive resin layer 3 satisfies the relationship of the above formula 1. In Equation 1, ε _AF is the relative dielectric constant of the conductive resin layer 3, ε _LC is the relative dielectric constant of the liquid crystal layer, d _AF is the thickness of the conductive resin layer 3, and d _LC is The thickness of the liquid crystal layer, and L is the number of scanning lines of the liquid crystal display device.

  FIG. 3 is a schematic diagram showing an equivalent circuit of a liquid crystal display device provided with the liquid crystal alignment substrate of the present invention. Formula 1 is obtained from an equivalent circuit of the liquid crystal alignment substrate 1 having the substrate 2, the transparent conductive layer 4, and the conductive resin layer 3. Since the liquid crystal layer and the conductive resin layer constituting the liquid crystal display device are dielectrics and they have a laminated structure, the liquid crystal layer and the conductive resin layer are, as shown in FIG. ) And electric resistance (R).

The voltage value V _LC applied to the liquid crystal layer by solving the circuit equation for the current flowing through the liquid crystal cell equivalent circuit of FIG. In Equations 2 to 4, V is the voltage supplied from the external drive circuit, the constant R _LC is the electrical resistance of the liquid crystal layer, R _AF is the electrical resistance of the conductive resin layer, and C _LC is is the capacitance of the liquid crystal layer, C _AF is the capacitance of the conductive resin layer, t ₀ and t ₁ is the time constant of the equivalent circuit, t ₀ and t ₁ is the electrical resistance of the transparent conductive layer is the time constant represented by the formula 3 and formula 4 when the R _ITO.

Here, the electrical resistance (R) of a dielectric such as a conductive resin layer or a liquid crystal layer is obtained by using the specific resistance ρ (Ωcm), the film thickness d, and the area S of the dielectric, R = ρ (d / S) Therefore, the relationship between the conductive resin layer 3 and the liquid crystal layer is expressed as R _AF / R _LC = (d _AF / d _LC ) · (ρ _AF / ρ _LC ). Furthermore, the capacitance (C _AF ) of the conductive resin layer 3 is expressed by C _AF = (ε ₀ ε _AF / d _AF ) S, and the capacitance of the liquid crystal layer is C _LC = (ε ₀ ε _LC / D _LC ) S. However, ε ₀ is the dielectric constant of vacuum, ε ₀ = 8.854 × 10 ⁻¹⁴ (F / cm), and S is the pixel area.

For example, the specific resistance ρ _LC of nematic liquid crystal (for example, DP5003 manufactured by Chisso Corporation) used in the liquid crystal display device is about 10 ¹³ Ωcm, and the thickness d _LC of the liquid crystal layer made of the nematic liquid crystal is about 5 μm. On the other hand, the thickness d _AF of the conductive resin layer 3 is about 1 to 3 μm. Further, the relative dielectric constant ε _LC of the liquid crystal layer is about 7 as described below, and the relative dielectric constant ε _AF of the conductive resin layer 3 is about 3-5.

FIG. 4 shows that ρ _LC = 10 ¹³ Ωcm, d _LC = 5 μm, d _AF = 3 μm, ε _LC = 7, ε _AF = 4, and ITO electric resistance R _ITO = 10Ω, and the value of ρ _AF is 10 It is a figure showing the result of having calculated the time change of the voltage ratio (V _LC / V) _concerning a liquid crystal layer in each case of ⁶ Ωcm, 10 ⁸ Ωcm, and 10 ⁹ Ωcm using Equation 2.

As can be seen from Equation 1 and FIG. 4, the applied voltage is not immediately applied to the liquid crystal layer, but is applied after a certain delay represented by the time constant t ₁ and the time constant t ₀ has occurred. In general, the time constant t ₁ depends on the electric resistance R _ITO of the transparent conductive layer 4 such as _ITO , but since the electric resistivity ρ _ITO of _ITO is as small as about 1 × 10 ⁻⁴ Ωcm, the time constant t ₁ is 10 ^−6. It becomes sec, shortened as compared with the gate selection time t _g of the TFT element in the liquid crystal display device described below. As a result, the delay due to the time constant t ₁ does not become a problem.

On the other hand, since the time constant t ₀ is determined depending on the electric resistance R _AF , the capacitance _CAF, etc. of the conductive resin layer 3, if the time constant t ₀ is longer than the gate selection time t _g , When a voltage is applied, a predetermined voltage is not applied to the liquid crystal layer, causing a problem that the liquid crystal is not driven sufficiently. In order to solve this problem, the time constant t ₀ may be made shorter than the gate selection time t _g , and for this purpose, as can be seen from Equation 3 or Equation 4, the capacitance C _{AF of the} conductive resin layer 3 can be obtained. There is a solution that increases the electrical resistance R _AF of the conductive resin layer 3. The present inventor has studied those solutions is to increase the capacitance C _AF of the conductive resin layer 3 is limited, constant t time by increasing the electrostatic capacitance C _{AF Since} it is difficult to set ₀ to the gate selection time _tg or less, it has been found that reducing the electric resistance _RAF of the conductive resin layer 3 is a practical solution. In FIG. 3, V _AF represents a voltage applied to the resin coloring layer, and V _ITO represents a voltage applied to the transparent conductive layer.

When the screen rewriting is performed on the liquid crystal display element having the number of scanning lines L at a frame frequency of 60 Hz, the gate selection time _tg is expressed by the following Equation 5.

On the other hand, as described above, since the above problem can be solved if the time constant t ₀ is shorter than the gate selection time t _g, the condition that t ₀ expressed by Equation 3 is smaller than t _g expressed by Equation 5 is satisfied. If satisfied, when a voltage is applied to the liquid crystal layer, a predetermined voltage is applied to the liquid crystal layer, and the liquid crystal is sufficiently driven.

When the electrical resistivity ρ _AF of the conductive resin layer 3 satisfies the relationship of the above formula 1, the time constant t ₀ is shorter than the gate selection time t _g , and the TFT element can sufficiently drive the liquid crystal. . From the right side of Equation 1, it can be seen that it also depends on the relative dielectric constant ε _LC of the liquid crystal layer and the thickness d _LC of the liquid crystal layer, but the relative dielectric constant of normal nematic liquid crystal is 2 to 10, and the liquid crystal display The thickness of the nematic liquid crystal layer of the device is about 3 to 10 μm. Therefore, in this liquid crystal display device, ε _LC / d _LC is in the range of 0.2 to 3.3 (μm ⁻¹ ). Therefore, the electrical resistivity ρ _AF of the conductive resin layer when nematic liquid crystal is used. The upper limit value is expressed by Equation 6 in which ε _LC / d _LC = 0.2 in Equation 1.

The number L (lines) of the scanning lines of the liquid crystal display device and the gate selection time t _g (see Equation 5) corresponding to the scanning lines are, for example, 31.8 μs (the number of scanning lines in the NTSC (National TV Standards Committee) system). : 525), 69.2 μs (number of scanning lines: 240) in the Q-VGA (Quarter-Video Graphics Array) system, and 34.8 μs (number of scanning lines: 480) in the VGA (Video Graphics Array) system. This is 21.7 μs (the number of scanning lines: 768) in the XGA (Extended Graphics Array) system, and 16.3 μs (the number of scanning lines: 1024) in the S-XGA (Super-Extended Graphics Array) system. In the HDTV (High Definition Television) system, it is 14.8 μs (the number of scanning lines: 1125).

In each of these methods, when the relative dielectric constant ε _AF of the conductive resin layer 3 is 3 and the thickness d _AF of the conductive resin layer 3 is 1.5 μm, the electrical resistivity ρ _AF in each of the above methods is The upper limit, that is, the calculated value on the right side of Equation 6 is 1.1 × 10 ⁸ Ωcm in the NTSC system, 2.4 × 10 ⁸ Ωcm in the Q-VGA method, and 1.2 × 10 ^{8 in the} VGA method. Ωcm, 7.5 × 10 ⁷ Ωcm in the XGA system, 5.6 × 10 ⁷ Ωcm in the S-XGA system, and 5.1 × 10 ⁷ Ωcm in the HDTV system.

  In a display device such as a mobile phone, a personal computer, and a TV, characters and images can be clearly seen if the resolution is higher than Q-VGA. Therefore, in the liquid crystal display device according to the present invention, Q-VGA The above resolution is preferable.

Therefore, for example, in a TFT drive type liquid crystal display device using nematic liquid crystal, in the case of Q-VGA resolution, the electrical resistivity ρ _AF of the conductive resin layer is 2.4 × 10 ⁸ Ωcm or less. For example, the liquid crystal layer can be sufficiently charged from the drive circuit within the gate selection time, and the liquid crystal can be driven. If the electrical resistivity ρ _AF of the conductive resin layer is 2.4 × 10 ⁸ Ωcm or less, the gate selection is the same as in the case of Q-VGA even if the resolution is Q-VGA or less. The liquid crystal layer can be sufficiently charged from the drive circuit within the time, and the liquid crystal can be driven.

The gate selection time is defined by the length of a period during which a voltage equal to or higher than the threshold voltage of the TFT element is applied to the gate electrode of the TFT element, and the calculated value on the right side of Equation 6 is the saturation time of the liquid crystal equivalent circuit shown in FIG. Is the upper limit value of the electrical resistivity of the conductive resin layer when the time constant t ₀ (Equation 3) becomes equal to the gate selection time t _g (Equation 5).

In Equation 6, when the electrical resistivity ρ _AF of the conductive resin layer exceeds the calculated value on the right side of Equation 1, the voltage V is divided into the conductive resin layer 3 and the liquid crystal layer when the TFT element is switched on. Therefore, the voltage applied to the liquid crystal layer is reduced, which causes a problem that the liquid crystal cannot be driven sufficiently. Further, when the electrical resistivity ρ _{AF of} the conductive resin layer 3 exceeds the calculated value on the right side of Equation 6, due to a transient phenomenon due to the switch-on of the TFT element, it takes time until the voltage applied to the liquid crystal layer is saturated. Take it. As a result, the voltage applied to the liquid crystal layer is not saturated within the gate selection time in driving the TFT element, and the liquid crystal may not be driven sufficiently. On the other hand, in the present invention, since the conductive resin layer 3 has the electrical resistivity in the range of the above-described formula 3, the problem can be solved.

The conductive resin layer 3 is the thickness range of not less 5μm above 0.1 [mu] m, the electrical resistivity [rho _AF is made the 2.4 × 10 ⁸ Ωcm or less, the electrical resistivity [rho _AF 1. More preferably, it is 5 × 10 ⁸ Ωcm or less. Specifically, the conductive resin layer 3 has an electric resistivity ρ _AF of 1.5 × 10 5 when the relative dielectric constant is in the range of 2 to 10 and the thickness is in the range of 0.1 μm to 5 μm. It is preferably ⁸ Ωcm or less. In this case, if the relative dielectric constant of the conductive resin layer 3 is less than 2, conductivity may be difficult to obtain, and if the relative dielectric constant exceeds 10, a delay occurs in the voltage applied to the liquid crystal layer, A high-resolution liquid crystal display element having about 1000 lines may not be sufficiently driven. If the thickness of the conductive resin layer 3 exceeds 5 μm, the light transmittance required for the liquid crystal display element may not be obtained. When the resistivity ρ _{AF of} the conductive resin layer 3 exceeds 2.4 × 10 ⁸ Ωcm, a sufficient bright / dark display cannot be performed without sufficient driving voltage applied to the liquid crystal layer (that is, the contrast is reduced). There is. The lower limit of the resistivity ρ _AF of the conductive resin layer 3 is not particularly limited. For example, the electrical resistivity ρ = 1 × 10 ⁻⁴ Ωcm of conventional ITO (indium tin oxide) can be given.

Therefore, the conductive resin layer has an electric resistivity ρ _AF of 2.4 × 10 ⁸ Ωcm or less in a thickness range of 0.1 μm to 5 μm, and therefore the liquid crystal alignment substrate of the present invention is applied to a liquid crystal device. In such a case, a sufficient voltage is applied to the liquid crystal layer, and the contrast is hardly lowered. As a result, the liquid crystal display device can be operated with high contrast, and high-quality display can be performed.

(Liquid crystal display device)
Next, the liquid crystal display device of the present invention will be described.

  FIG. 5 is a schematic cross-sectional view showing an example of the first liquid crystal display device of the present invention. In this liquid crystal display device 11, a liquid crystal layer 13 is sealed in a gap in which the liquid crystal alignment substrate 1 of the present invention and the liquid crystal driving substrate 12 are opposed to each other at a predetermined interval. The liquid crystal alignment substrate 1 includes a substrate 2, a color filter 7 provided on the substrate 2, a transparent conductive layer 4 provided on the color filter 7, and a liquid crystal molecule provided on the transparent conductive layer 4 with predetermined liquid crystal molecules. And a conductive resin layer 3 oriented in the direction. One liquid crystal drive substrate 12 includes a substrate 15, a TFT element 17 and a pixel electrode 18 (transparent conductive layer) provided on the substrate 15, and a conductive material provided on them for aligning liquid crystal molecules in a predetermined direction. And a functional resin layer 3. Although not shown, polarizing plates are provided outside the liquid crystal alignment substrate 1 and the liquid crystal driving substrate 12.

The liquid crystal alignment substrate 1 constituting the liquid crystal display device 11 of FIG. 5 is the above-described liquid crystal alignment substrate of the present invention. That is, the conductive resin layer 3 of the liquid crystal alignment substrate 1 has an electrical resistivity ρ _AF of 2.4 × 10 ⁸ Ωcm or less in a thickness range of 0.1 μm to 5 μm.

On the other hand, the liquid crystal driving substrate 12 constituting the liquid crystal display device 11 of the present invention shows another example of the liquid crystal alignment substrate of the present invention described above. As shown in FIG. 5, the liquid crystal driving substrate 12 includes at least a substrate 15 and a conductive resin layer 16 provided on the substrate 15. The substrate 15 is the same as the substrate 12 described above. The conductive resin layer 16 is substantially the same as the conductive resin layer 3 described above, and the electrical resistivity ρ _AF is 2.4 × 10 ⁸ Ωcm or less when the thickness is in the range of 0.1 μm to 5 μm. Is. Although the uneven structure is formed on the surface of the conductive resin layer 16, the uneven structure may not be formed on the surface of the conductive resin layer 16 on the thin film transistor 17 as shown in FIG. 5. As described above, if the surface of the conductive resin layer 16 on the thin film transistor 17 is not formed in a concavo-convex structure, the pressing force applied to the thin film transistor 17 when the concavo-convex structure is formed by, for example, mold transfer can be reduced.

  A thin film transistor 17 (TFT element) formed in a predetermined pattern is provided between the substrate 15 and the conductive resin layer 16 on the substrate 15, and a pixel formed in a predetermined pattern. An electrode 18 is provided. The liquid crystal driving substrate 12 includes a gate line group (not shown) for opening and closing the thin film transistor 17, a signal line group (not shown) for supplying a video signal, and a voltage supply to the transparent conductive layer 4 of the liquid crystal alignment substrate 1. A line (not shown) or the like is provided. These wire groups and wires are constituted by lead wires, and the lead wires are made of metal such as aluminum. The lead wires are usually provided on the substrate 15 at a time in the manufacturing process of the thin film transistor 17.

  The pixel electrode 18 is formed using indium tin oxide (ITO), zinc oxide (ZnO), tin oxide (SnO), or an alloy thereof. The thickness of the pixel electrode 18 is, for example, about 0.01 μm to 2 μm, preferably about 0.03 μm to 1.5 μm. The pixel electrode 18 can be formed by a general film forming method such as a sputtering method, a vacuum evaporation method, a CVD method or the like.

The liquid crystal layer 13 is not particularly limited as long as it is a liquid crystal layer generally used in a liquid crystal display device, but is preferably a liquid crystal layer in which the alignment state of the liquid crystal changes depending on electric field application conditions and the refractive index changes accordingly. And a nematic liquid crystal layer, a ferroelectric liquid crystal layer, and the like, and a ferroelectric liquid crystal layer is more preferable because of excellent surface stability, high-speed response, wide viewing angle, and the like. The ferroelectric liquid crystal, for example, homogeneous alignment or homeotropic alignment and chiral smectic C phase, a smectic liquid crystal and the like having such chiral smectic C _A phase. The thickness of the liquid crystal layer is preferably 0.5 μm or more and 5 μm or less. If the thickness of the liquid crystal layer is less than 0.5 μm, it may be difficult to uniformly control the panel gap. If the thickness of the liquid crystal layer exceeds 5 μm, the liquid crystal alignment regulating force at the substrate interface becomes weak, and thus liquid crystal alignment may be easily disturbed.

  Reference numeral 19 in FIG. 5 denotes a spacer for making the distance (cell gap) between the liquid crystal alignment substrate 1 and the liquid crystal driving substrate 12 constant. As shown in FIG. 5, the spacer 19 may be a bead-shaped spacer, or may be a columnar or wall-shaped spacer formed of a transparent resin or the like. Examples of the bead-shaped spacer include particles such as plastic beads, silica beads, and glass beads.

  FIG. 6 is a schematic sectional view showing an example of the second liquid crystal display device of the present invention. In the liquid crystal display device of the present invention, a liquid crystal layer 13 is sealed in a gap in which the liquid crystal alignment substrate 1 of the present invention and the liquid crystal driving substrate 22 are opposed to each other at a predetermined interval. Although not shown, polarizing plates are provided outside the liquid crystal alignment substrate 1 and the liquid crystal driving substrate 22.

The liquid crystal alignment substrate 1 constituting the liquid crystal display device 21 of the present invention shown in FIG. 6 is the liquid crystal alignment substrate of the present invention described above. That is, the conductive resin layer 3 of the liquid crystal alignment substrate 1 has an electrical resistivity ρ _AF of 2.4 × 10 ⁸ Ωcm or less in a thickness range of 0.1 μm to 5 μm.

  On the other hand, the liquid crystal drive substrate 22 constituting the liquid crystal display device 21 of the present invention is different from the liquid crystal drive substrate 12 in that a resin alignment film 23 is provided instead of the conductive resin layer 16. Since other configurations are the same as those of the liquid crystal drive substrate 12, the same reference numerals are given and description thereof is omitted. That is, the liquid crystal drive substrate 22 includes a substrate 15, a thin film transistor 17 formed in a predetermined pattern on the substrate 15, a pixel electrode 18 (transparent conductive layer) formed in a predetermined pattern, and a resin subjected to an alignment process. And an alignment film 23. The resin alignment film 23 can be formed of an organic compound such as polyimide, polyamide, polyurethane, or polyurea. The thickness of the resin alignment film 23 is about 0.01 μm to 1 μm. The resin alignment film 23 is formed, for example, by a known method such as various printing methods or coating methods, and then fired and then subjected to an alignment treatment such as rubbing or irradiation with polarized ultraviolet rays.

  Since a predetermined voltage is applied to the pixel electrodes 18 of the liquid crystal display devices 11 and 21 of the present invention, the liquid crystal layer 13 responds well to electric fields (that is, a sufficient driving voltage is applied to the liquid crystal layer 13). By providing the orthogonal polarizing plates outside the alignment substrate 1 and the liquid crystal drive substrates 12 and 22, it is possible to display sufficiently bright and dark. That is, the liquid crystal display devices 11 and 21 can be operated with high contrast, and high-quality display can be performed.

  Note that the liquid crystal alignment substrate of the present invention may be used only for the liquid crystal driving substrate constituting the liquid crystal display device. That is, as shown in FIG. 7, the same liquid crystal driving substrate 12 used in the first liquid crystal display device 11 is used as the liquid crystal driving substrate constituting the liquid crystal display device 31. On the other hand, the alignment substrate 32 facing the liquid crystal drive substrate 12 is provided with a resin alignment film 33 that is substantially the same as the resin alignment film 23 instead of the conductive resin layer 7. Thus, even if the liquid crystal display device 31 of the present invention is configured, the liquid crystal layer 13 can respond well to an electric field, and high-quality display can be performed.

  Hereinafter, the liquid crystal display device of the present invention will be specifically described with reference to examples.

Example 1
Five kinds of ultraviolet curable conductive resins having different electrical resistivity of A1 to E1 shown in Table 1 are dispersed in ultraviolet curable resin (manufactured by Dainichi Seika Kogyo Co., Ltd.) with various weight ratios dispersed in ITO. It was adjusted. Next, an ultraviolet curable conductive resin is applied to the surface of a pair of transparent conductive film (ITO) glass substrates (Corning 7059 glass) having a thickness of 0.7 mm and a size of 20 mm × 20 mm by spin coating. And dried at 90 ° C. for 5 minutes. Thereafter, a mold member having a stripe pattern having a pitch of 5 μm, a convex width w ₁ of 2 μm, a concave width w ₂ of 2 μm, and a concave depth w ₃ of 2 μm is used as the ultraviolet curable conductive resin. After pressing, the ultraviolet curable conductive resin is cured by irradiating ultraviolet rays, and then the mold member is peeled off and dried at 150 ° C. for 1 hour to obtain a thickness having a striped fine uneven structure on the surface. Formed a 3 μm conductive resin layer.

  Next, after spraying bead-like spacers on one of the pair of glass substrates and forming a sealing material in a predetermined pattern on the other substrate by a screen printing method, the stripe pattern directions are orthogonal to each other. As described above, a panel having a gap of 5 μm was produced by laminating these two substrates. Then, after the inside of the panel was vacuum degassed, the inlet was immersed in a liquid crystal material (DP-5003, manufactured by Chisso), and the liquid crystal was injected into the entire panel under atmospheric pressure to produce a liquid crystal panel.

  When the prepared liquid crystal panel was observed under a pair of polarizing plates, a bright display by light transmission was obtained when the polarizing plates were orthogonally arranged, and the transmitted light was blocked and dark display was obtained when the polarizing plates were arranged in parallel. Therefore, it was confirmed that a good twisted nematic liquid crystal alignment was realized by using these liquid crystal alignment substrates.

Next, the voltage holding ratio of the liquid crystal panel is set to a gate selecting time (69 μs) corresponding to the QVGA method using a liquid crystal voltage holding ratio measuring device (VHR-1 type manufactured by Toyo Technica). As a result of measurement, as shown in Table 1, the smaller the electrical resistivity ρ _AF of the conductive resin layer, the higher the voltage holding ratio. Note that the contrast was measured simultaneously with the voltage holding ratio measurement, but the contrast increased as the electrical resistivity ρ _AF of the conductive resin layer decreased.

Therefore, as the electrical resistivity ρ _AF of the conductive resin layer is smaller, a larger voltage is effectively applied to the liquid crystal injected into the panel, and the liquid crystal responds sufficiently. From Table 1, in the case of the resolution of the QVGA system, in the sample D1, when the electric resistivity of the conductive resin layer is 0.9 × 10 ⁸ Ωcm or less, the voltage holding ratio is about 95% or more. When the TFT is driven by a TFT element, good display characteristics can be obtained. The relative dielectric constant of the liquid crystal material was 7.

In the samples D1 and E1, the voltage holding ratio is 95% or more, but the electrical resistivity (ρ _AF = 0.9 × 10 ⁸ Ωcm) of the conductive resin layer in the samples D1 and E1 is the right side of the equation 1. Or less than the calculated value.

(Example 2)
Five kinds of ultraviolet curable conductive resins having different electrical resistivity shown in Table 2 were prepared by dispersing finely powdered ITO in various weight ratios in an ultraviolet curable resin (manufactured by Dainichi Seika Kogyo). Next, as in the case of Example 1, a pair of thicknesses of 0.7 mm and a size of 20 mm × 20 mm on a glass substrate with transparent conductive film (ITO) (7059 glass manufactured by Corning) was applied to the surface of the ultraviolet curable type. The conductive resin was formed by spin coating and dried at 90 ° C. for 5 minutes. Thereafter, a mold member having a striped pattern with a pitch of 3 μm, a convex portion width w ₁ of 1 μm, a concave portion width w ₂ of 1 μm, and a concave portion depth w ₃ of 0.7 μm is applied to the ultraviolet curable conductive material. After pressing the resin and irradiating ultraviolet rays to cure the ultraviolet curable conductive resin, the mold member is peeled off and dried at 150 ° C. for 1 hour to have a striped fine uneven structure on the surface. A conductive resin layer having a thickness of 1.5 μm was formed.

  Next, bead-shaped spacers are dispersed on one of the pair of glass substrates, and after the seal material is formed in a predetermined pattern on the other substrate by a screen printing method, the stripe pattern directions are orthogonal to each other. A panel having a gap of 5 μm was produced by laminating these pair of substrates. Then, after the inside of the panel was vacuum degassed, the inlet was immersed in a liquid crystal material (DP-5003, manufactured by Chisso), and the liquid crystal was injected into the entire panel under atmospheric pressure to produce a liquid crystal panel.

  When the prepared liquid crystal panel was observed under a pair of polarizing plates, a bright display by light transmission was obtained when the polarizing plates were orthogonally arranged, and the transmitted light was blocked and dark display was obtained when the polarizing plates were arranged in parallel. Therefore, it was confirmed that a good twisted nematic liquid crystal alignment was realized by using these liquid crystal alignment substrates.

Next, the voltage holding ratio of the liquid crystal panel is set to a gate selecting time (69 μs) corresponding to the QVGA method using a liquid crystal voltage holding ratio measuring device (VHR-1 type manufactured by Toyo Technica). When measured, as in Example 1, the voltage holding ratio increased as the electrical resistivity ρ _AF of the conductive resin layer decreased as shown in Table 2. Note that the contrast was measured simultaneously with the voltage holding ratio measurement, but the contrast increased as the electrical resistivity ρ _AF of the conductive resin layer decreased.

Therefore, as the electrical resistivity ρ _AF of the conductive resin layer is smaller, a larger voltage is effectively applied to the liquid crystal injected into the panel, and the liquid crystal responds sufficiently. From Table 2, in the case of the resolution of the QVGA method, in sample C2, when the electrical resistivity ρ _AF of the conductive resin layer is 1.3 × 10 ⁸ Ωcm or less, the voltage holding ratio is about 95% or more. When the liquid crystal pixel is driven by a TFT element, good display characteristics can be obtained. In the samples C2, D2, and E2, the voltage holding ratio is 93% or more, but the electrical resistivity (ρ _AF = 1.3 × 10 ⁸ Ωcm) of the conductive resin layer in the sample C2 is the right side of the equation 1. Therefore, it can be easily confirmed that the electrical resistivity ρ _AF of the conductive resin layer of the liquid crystal display device falls within the ranges of the formulas 1 and 6.

It is a schematic sectional drawing which shows an example of the liquid crystal aligning substrate of this invention. It is process drawing which shows an example of the formation method of the liquid crystal aligning substrate of this invention. It is the schematic which shows the equivalent circuit of the liquid crystal display device provided with the liquid crystal aligning substrate of this invention. It is an example of the time change calculation value of _VLC in a liquid crystal equivalent circuit. It is a schematic sectional drawing which shows an example of the 1st liquid crystal display device of this invention. It is a schematic sectional drawing which shows an example of the 2nd liquid crystal display device of this invention. It is a schematic sectional drawing which shows an example of the 3rd liquid crystal display device of this invention. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 32 Liquid crystal alignment substrate 2, 15 Substrate 3, 16 Conductive resin layer 4 Transparent conductive layer 5 Concave part 6 Convex part 7 Color filter 11, 21, 31 Liquid crystal display device 12, 22 Liquid crystal drive substrate 13 Liquid crystal layer 17 Thin film transistor (TFT) element)
18 Pixel electrode 23, 33 Resin alignment film

Claims (4)

A liquid crystal alignment substrate having a substrate, a transparent conductive layer provided on the substrate, and a conductive resin layer provided on the transparent conductive layer and aligning liquid crystal molecules in a predetermined direction, wherein the conductive The liquid crystal alignment substrate, wherein the resin layer has an electrical resistivity of 2.4 × 10 ⁸ Ωcm or less when the thickness of the conductive resin layer is in the range of 0.1 μm to 5 μm.   The liquid crystal alignment substrate according to claim 1, wherein an uneven structure for aligning liquid crystal molecules in a predetermined direction is formed on a surface of the conductive resin layer. A liquid crystal display device in which a liquid crystal layer is sealed between a liquid crystal alignment substrate and a liquid crystal drive substrate,
One or both of the liquid crystal alignment substrate and the liquid crystal driving substrate are a substrate, a transparent conductive layer provided on the substrate, and a conductive property provided on the transparent conductive layer to align liquid crystal molecules in a predetermined direction. A liquid crystal display device characterized in that the electrical resistivity ρ _AF of the conductive resin layer satisfies the relationship of Formula 1 (where ε _AF is the relative dielectric constant of the conductive resin layer) 2 or more and 10 or less, ε _LC is a range of 2 or more and 10 or less in terms of the dielectric constant of the liquid crystal layer, d _AF is a range of 0.1 μm or more and 5 μm or less in terms of the thickness of the conductive resin layer, d _LC is the thickness of the liquid crystal layer in the range of 0.5 μm or more and 10 μm or less, and L is the number of scanning lines of the liquid crystal display device in the range of 2400 or less.

  The liquid crystal display device according to claim 3, wherein a concavo-convex structure for aligning liquid crystal molecules in a predetermined direction is formed on a surface of the conductive resin layer.

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