JP2008262175A - Liquid crystal display - Google Patents

Abstract

Disclosed is a liquid crystal display device having excellent manufacturing suitability and excellent viewing angle characteristics (particularly, small color shift and light leakage during black display).
A liquid crystal display device having at least a liquid crystal cell 12 and a transparent film 10 divided into a plurality of domains, wherein the transparent film has an in-plane retardation (Re) with respect to a wavelength λ nm in a visible light region, and / or A liquid crystal display comprising two or more domains a and b having different retardations (Rth) in the thickness direction, and the domain of the transparent film and the domain of the liquid crystal cell are not correlated with respect to their arrangement and / or size. Device.
[Selection] Figure 3

Description

  The present invention relates to a liquid crystal display device and a transparent film used as an optical compensation film for a liquid crystal display device or the like.

Liquid crystal display devices have the advantage of being thin and light, and are used in various applications. On the other hand, the liquid crystal display device has a problem that the viewing angle is narrow because the birefringence of the liquid crystal cell differs depending on the viewing direction.
As one of the methods with improved viewing angle characteristics, a multi-domain method is proposed in which multiple domains are formed in each pixel of the liquid crystal cell with different orientation directions of liquid crystal molecules and rising directions of liquid crystal molecules when a voltage is applied. Has been. By making each pixel of the liquid crystal cell multi-domain, the difference when the screen is observed from various directions is reduced, and the viewing angle can be expanded.

However, when observed from an oblique direction, not only a difference occurs in the birefringence of the liquid crystal cell, but also the transmission axes of the pair of polarizing plates deviate from the orthogonal direction. As a result, when observed from an oblique direction, there are problems such as light leakage during black display and color shift.
As a liquid crystal display device in which light leakage during black display is reduced, Patent Document 1 includes both substrates facing each other and a liquid crystal layer formed between the substrates, and includes a plurality of pixels. A liquid crystal display device, wherein each pixel includes a liquid crystal panel defined by at least two domains having different alignment characteristics, and a compensation film for compensating optical characteristics in a direction corresponding to the liquid crystal alignment direction of each domain. Proposed.

  In the liquid crystal display device described in Patent Document 1, a compensation film that compensates optical characteristics in a direction corresponding to the liquid crystal alignment direction of each domain of the liquid crystal cell is used. In order to produce such a liquid crystal display device, for example, a compensation film having a different phase difference in the in-plane region corresponding to each domain of the liquid crystal cell is produced, and the compensation film and each domain of the liquid crystal cell are combined. , It is necessary to paste them together in micron alignment. Such alignment is difficult and is not suitable for mass production.

Even in a liquid crystal display device that does not employ a multi-domain method, a plurality of domains in units of one pixel are formed in the liquid crystal cell, and one pixel is also divided into each color RGB domain of the color filter. ing. Conventionally, in order to reduce the color shift when observed from an oblique direction, it has also been proposed to adjust the optical characteristics of the compensation film in accordance with the RGB wavelengths of the color filter. However, if this method is adopted, it is not preferable from the viewpoint of productivity, for example, as described above, alignment in the micron unit is necessary in the manufacturing process, or patterning technology for a fine region is necessary.
JP 2006-18285 A

  An object of the present invention is to provide a liquid crystal display device that is excellent in manufacturing suitability and excellent in viewing angle characteristics (particularly, color shift and light leakage during black display are small).

Means for solving the above problems are as follows.
[1] A liquid crystal display device having at least a liquid crystal cell divided into a plurality of domains and a transparent film, wherein the transparent film has an in-plane retardation (Re) and / or thickness with respect to a wavelength λ nm in a visible light region. It is composed of two or more domains having different retardations (Rth) in the vertical direction, and the domain of the transparent film and the domain of the liquid crystal cell are not correlated with respect to the arrangement and / or the size thereof. A characteristic liquid crystal display device.
[2] The liquid crystal display device according to [1], wherein the domains of the transparent film are arranged in a lattice pattern or a zigzag pattern.
[3] The liquid crystal display device according to [1] or [2], wherein the minimum diameter of each domain of the transparent film is 1 μm to 300 μm.
[4] The Re and Rth of each domain at a wavelength λnm in the visible light region of the transparent film are within ± 20% of the average value of Re and Rth at the same wavelength of the transparent film. The liquid crystal display device according to any one of 1] to [3].
[5] The transparent film has a plurality of domains having Re of 40 to 50 nm at a wavelength λ nm in a visible light region and a plurality of domains having Re of 50 to 60 nm at the same wavelength [1] ]-[4] liquid crystal display device.
[6] The transparent film has a plurality of domains having an Rth of 180 to 200 nm at a wavelength λnm in a visible light region and a plurality of domains having an Rth of 200 to 220 nm at the same wavelength [1] ]-[5] liquid crystal display device.
[7] The in-plane retardation (Re) and / or retardation in the thickness direction (Rth) with respect to the wavelength λ nm in the visible light region is composed of two or more domains different from each other, and the minimum diameter of each domain is 1 to 300 μm. A transparent film characterized by being.

  According to the present invention, it is possible to provide a liquid crystal display device that is excellent in manufacturability and excellent in viewing angle characteristics (particularly, color shift and light leakage during black display are small).

Hereinafter, the present invention will be described in detail. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.
First, details of Re (λ) and Rth (λ) in this specification will be described below.
(Measurement of Re and Rth)
In this specification, Re (λ) and Rth (λ) represent in-plane retardation and out-of-plane retardation at a wavelength λ, respectively. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments).
When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.
Rth (λ) is Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotation axis) (if there is no slow axis, any in-plane film The light of wavelength λ nm is incident from each of the inclined directions in steps of 10 degrees from the normal direction to 50 degrees on one side with respect to the film normal direction (with the direction of the rotation axis as the rotation axis). KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed value of the average refractive index, and the input film thickness value.
In the above case, when the film has a direction in which the retardation value is zero at a certain tilt angle with the slow axis in the plane from the normal direction as the rotation axis, the retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing its sign to negative.
In addition, the retardation value is measured from the two inclined directions, with the slow axis as the tilt axis (rotation axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotation axis), Based on the value, the assumed value of the average refractive index, and the input film thickness value, Rth can also be calculated from the following equations (1) and (2).

注記：
上記式中、Ｒｅ（θ）は法線方向から角度θ傾斜した方向におけるレターデーション値を表す。ｎｘは面内における遅相軸方向の屈折率を表し、ｎｙは面内においてｎｘに直交する方向の屈折率を表し、ｎｚはｎｘ及びｎｙに直交する方向の屈折率を表し、ｄは膜厚を表す。

Note:
In the above formula, Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction. nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction perpendicular to nx in the plane, nz represents the refractive index in the direction perpendicular to nx and ny, and d represents the film thickness. Represents.

In the case where the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film having no so-called optical axis, Rth (λ) is calculated by the following method.
Rth (λ) is the above-mentioned Re (λ), and the in-plane slow axis (determined by KOBRA 21ADH or WR) is the tilt axis (rotation axis) from −50 degrees to +50 degrees with respect to the film normal direction. The light of wavelength λ nm is incident from each inclined direction in 10 degree steps and measured at 11 points, and KOBRA 21ADH or WR is calculated.
In the above measurement, as the assumed value of the average refractive index, the values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. Examples of the average refractive index values of main optical films are given below:
Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).
The KOBRA 21ADH or WR calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

  In this specification, the wavelength λ nm in the visible light region is 550 nm unless otherwise specified.

The present invention relates to a liquid crystal display device having a liquid crystal cell divided into a plurality of domains and a transparent film, wherein the transparent film has an in-plane retardation (Re) and / or thickness with respect to a wavelength λ nm in a visible light region. The direction retardation (Rth) is composed of two or more domains different from each other, and the domain of the transparent film and the domain of the liquid crystal cell are not correlated at least with respect to the arrangement and / or the size thereof. The present invention relates to a characteristic liquid crystal display device.
In the present invention, a transparent film comprising two or more domains having different in-plane retardation (Re) and / or thickness direction retardation (Rth) with respect to a wavelength λ nm in the visible light region is used, and each of the transparent films Viewing angle characteristics are improved by making the domain independent of each domain of the liquid crystal cell in arrangement and / or size. According to the present invention, when incorporating the film into a liquid crystal display device, it is not necessary to align each domain of the liquid crystal cell and each domain of the film, and the viewing angle characteristics are excellent without going through complicated steps. A liquid crystal display device can be provided.

  Examples of the transparent film used in the present invention include a domain a and a domain b having different Re and / or Rth, and a plurality of domains a and a plurality of domains b arranged randomly and a predetermined rule. Are included. Since the domains of the liquid crystal cell are usually arranged according to a certain rule, if the former mode in which the domains are arranged randomly is used, the arrangement pattern of the domain of the liquid crystal cell and the size thereof are arbitrary. This is preferable because it is independent of the domain of the liquid crystal cell. On the other hand, the latter mode in which the domains a and b are arranged according to a predetermined rule can be manufactured using a conventional method using existing equipment, and the adjustment of the optical characteristics of the entire film is possible. It is preferable because it is easy. The latter embodiment is used in combination with a liquid crystal cell in which the size and / or arrangement pattern of each domain is different.

  There is no restriction | limiting in particular about the shape of the domain of the said transparent film, and its arrangement pattern. FIG. 1 shows top views of some examples of transparent films that can be used in the liquid crystal display device of the present invention. The transparent film of FIG. 1 (a) is a mode in which square domains a and domains b are arranged in a staggered manner, and FIG. 1 (b) shows square domains a and domains b arranged in a lattice pattern. It is an aspect. As shown in FIG. 1C, the shape of the domain a and the domain b may be rectangular. Further, as shown in FIG. 1D, the domain a and the domain b may be bent.

The domain a and the domain b have different in-plane retardation (Re) and / or retardation in the thickness direction (Rth) with respect to the wavelength λ nm in the visible light region. When the transparent film of this embodiment is used as an optical compensation film for a liquid crystal display device of a predetermined mode, the entire transparent film is required to show Re and Rth necessary for optical compensation of the liquid crystal display device of that mode. The In such an embodiment, it is preferable that Re and Rth of domain a and domain b at a wavelength λ nm in the visible light region of the transparent film are within ± 20% of the average value of Re and Rth of the transparent film at the same wavelength. The average value is preferably within ± 10%, and more preferably within ± 5%. On the other hand, if the difference between Re1 and / or Rth1 of domain a and Re2 and / or Rth2 of domain b is too small, the viewing angle improvement effect due to the presence of domain a and domain b may not be sufficiently obtained. . | Re1-Re2 | is preferably 5% or more of the average value of Re, more preferably 5 to 20%, and still more preferably 5 to 10%. Similarly, | Rth1-Rth2 | is preferably 5% or more of the average value of Rth, more preferably 5 to 20%, and even more preferably 5 to 10%. When the average value of Re and Rth of the transparent film, and Re and Rth of each domain satisfy the above relationship, the effect of improving the viewing angle characteristics due to the presence of domain a and domain b having different Re and / or Rth, and Both of the optical compensation effect by the transparent film can be obtained.
In addition, the average value of Re and Rth of a transparent film means the value of Re and Rth of the whole film measured by the said method. Moreover, Re and Rth of each domain of the transparent film can be measured using a microscopic retardation measuring machine, and examples of measuring machines used include LCA-LU4 of Meisho Technica.

  In the aspect of the VA mode liquid crystal display device, the Re of the domain a at the wavelength λ nm in the visible light region of the transparent film is preferably 40 to 50 nm, and the Re of the domain b of the same wavelength is preferably 50 to 60 nm. . Further, in the aspect of the VA mode liquid crystal display device, the Rth of the domain a at a wavelength λ nm in the visible light region of the transparent film is 180 to 200 nm, and the Rth of the domain b of the same wavelength is 200 to 220 nm. Is preferred. A combination of both is more preferable. That is, in the VA mode liquid crystal display device, the Re of the domain a at the wavelength λ nm in the visible light region is preferably 40 to 50 nm, and Rth is preferably 180 to 200 nm. More preferably, the Re of the domain b is 50 to 60 nm and the Rth is 200 to 220 nm.

  In the present invention, a liquid crystal cell divided into a plurality of domains is used. In the present invention, it is not required to be a multi-domain liquid crystal cell, but any general liquid crystal cell divided into pixels or sub-pixels is included. For example, as shown in FIG. 2, even in a liquid crystal cell that does not employ the multi-domain method, a plurality of domains D1 each having one pixel (pixel) as a unit are formed in the liquid crystal cell. Are also divided into domains D2 of RGB colors (subpixels) of the color filter. Further, in the multi-domain method, a plurality of domains D3 are formed in the subpixel. The “plural domains of the liquid crystal cell” referred to in the present invention may be any of D1, D2 and D3. That is, in the embodiment having the liquid crystal cell of FIG. 1, each domain of the transparent film has a domain arrangement pattern dissimilar to each of the domains D1, D2, and D3 of the liquid crystal cell, Even if the arrangement pattern is the same or similar, the size of each domain is different and is not suitable as a whole.

  FIG. 3 schematically shows an example of a combination of a transparent film and a liquid crystal cell. The transparent film 10 includes a plurality of domains a and b having different Re and / or Rth. The liquid crystal cell 12 in FIG. 3 partially shows one pixel (pixel), and is composed of RGB sub-pixels. The domains a and b of the transparent film 10 are regularly arranged in a grid pattern, but the regularity period, that is, the sizes of the domains a and b are different from those of the pixels and subpixels RGB. Does not correspond to a pixel or subpixel of a liquid crystal cell.

  FIG. 4 shows a mode in which each subpixel RGB is further combined with a transparent film 10 and a liquid crystal cell 12 ′ in which liquid crystal molecules (indicated by an elliptical shape in the drawing) are divided into a plurality of domains. Also in the embodiment shown in FIG. 4, the regular period of the domains a and b of the transparent film 10, that is, the size of the domains a and b is different from the minimum domain of the liquid crystal cell 12 ′. Does not correspond to the smallest domain.

In the present invention, there is no particular limitation on the size of each domain of the transparent film, and considering the size of the domain of the liquid crystal cell to be combined, it does not match the size (provided that the arrangement pattern is different) The sizes may be equal). The minimum diameter of each domain of the transparent film is preferably shorter than the minimum diameter of one pixel of the liquid crystal cell. Specifically, it is preferably 1 to 300 μm, more preferably 1 to 100 μm. Here, the minimum diameter means a short side when the shape of the domain is a rectangular shape and a shape similar thereto, and when the shape is indefinite, the shape is regarded as a circle and the circle of the area S is used. The length corresponding to the diameter of.
In other words, in the transparent film used in the present invention, Re and / or Rth changes to at least two different values at a pitch of 1 to 300 nm in at least one direction in the plane. It is the transparent film characterized. The change pitch is preferably 1 to 100 μm.

  In the above example, for ease of explanation, only the embodiment in which the transparent film has two domains has been described. However, the liquid crystal display device of the present invention is not limited to this embodiment, and Re and / or Alternatively, it is of course possible to use a transparent film in which three or more types of domains having different Rth are arranged randomly or regularly. It is considered that as the number of types of domains increases, the effect of improving the viewing angle characteristics becomes higher. When the transparent film is composed of three or more types of domains, Re and Rth of each domain are preferably within ± 20% of the average value of Re and Rth of the transparent film.

Next, the transparent film used for this invention and its preparation method are demonstrated in detail.
The transparent film used in the present invention is a film having transparency to visible light. Specifically, the transmittance for light in the visible light region is preferably 80% or more. Here, the transmittance refers to the ratio of light transmitted to the front of the film with respect to light incident on the film from the rear.
There is no restriction | limiting in particular about the material of the said transparent film. Examples of materials used for the production include cellulose acylate, polyolefin, polycarbonate, and the like, which are general polymer film materials. Moreover, you may produce using the curable liquid crystal composition conventionally utilized for preparation of the optical compensation film. Moreover, when the film | membrane which consists of a curable liquid crystal composition does not have a self-supporting property, you may use a polymer film as a support body and form the layer which consists of a curable liquid crystal composition on the surface. That is, the transparent film may have a single layer structure or a laminated structure.

As an example of a method for adjusting the in-plane retardation Re of the film, a curable cholesteric liquid crystal material containing a predetermined dichroic polymerization initiator or a discotic liquid crystal material having a photosensitive functional group is used, and polarized irradiation is performed. A method for controlling the irradiation amount and the like is mentioned. For example, when a cholesteric phase containing a predetermined dichroic polymerization initiator is irradiated with polarized ultraviolet light, the helical structure of the cholesteric phase is distorted and the curing proceeds, and the formed cured film is caused by distortion of the cholesteric phase. In-plane retardation Re is developed. Since the Re value to be expressed depends on the ultraviolet intensity, irradiation amount, extinction ratio, and the like when irradiated with polarized ultraviolet light, a desired Re value can be expressed by adjusting one or more of these conditions. Further, for example, Re can be adjusted by irradiating polarized ultraviolet light to a discotic liquid crystal phase containing a discotic molecule having a photosensitive functional group and adjusting the irradiation amount. When irradiated with polarized ultraviolet light, the photosensitive functional group oriented in the polarization direction selectively reacts with light. The photoreactive discotic liquid crystal phase has a lower refractive index in the polarization direction than before the reaction. Thus, desired Re can be obtained by irradiating polarized ultraviolet rays using a discotic liquid crystal compound. According to these methods, domains having Re in a desired range can be formed in a predetermined pattern by irradiating polarized light under a predetermined condition through a photomask having a predetermined pattern. The domain size can be adjusted to a desired size depending on the shape of the photomask.
A method for adjusting Re of a cholesteric film by polarized light irradiation is described in SID06 DIGEST 1539-1542 and the like, and liquid crystal materials usable in this method are described in Proc. IDRC, Vol. 24, pp. 773. -775 (2004), etc., and can be used to produce the transparent film.

As an example of a method for adjusting the retardation Rth in the thickness direction of the film, there is a method of embossing the formed film. Embossing refers to a process that creates a continuous pattern of fine irregularities on the surface of a film. Since Rth of the film is proportional to its thickness d, for example, when a film having a uniform thickness is produced and then embossing is performed to continuously form fine recesses, the Rth of the recesses is greater than the protrusions. Becomes smaller. By forming the concave portion and the convex portion by embossing, a domain a and a domain b having different Rth can be formed. Embossing is usually performed by pressing an embossed ring with a pattern on a film on a back roll such as metal or rubber. The value of Rth can be adjusted by the depth of the pattern carved on the embossing ring, the pressure at the time of pressing, the temperature at the time of processing, and the like. Further, the size of the domain can be adjusted to a desired size by the shape of the pattern carved on the embossing ring or the like used for embossing.
In addition, about an embossing, there exists detailed description in [0160]-[0166] of Unexamined-Japanese-Patent No. 2005-22766, and it can utilize for manufacture of the said transparent film.

  Moreover, when producing an optical film using the said discotic liquid crystal material, Rth can be adjusted by adjusting the temperature at the time of hardening reaction, such as superposition | polymerization. For example, when the temperature during the curing reaction is high, the curing reaction proceeds in a state where the birefringence of the liquid crystal phase is small, so that the Rth of the cured film becomes small.

Further, a method for producing an optical film using the discotic liquid crystal material will be described in detail. As a method for producing a film having a plurality of domains in which both Re and Rth are different from each other using the material, a composition containing a discotic liquid crystal having a photosensitive functional group is irradiated with non-polarized ultraviolet rays and polarized ultraviolet rays through a photomask. Then, there is a method of forming an optically anisotropic layer by advancing the curing reaction. By this method, it is also possible to obtain desired Re and Rth domains in which the main refractive index values nx, ny and ny in the three directions are adjusted.
When a discotic liquid crystal molecule having a photosensitive functional group (for example, a monovalent group including a benzene ring and a double bond conjugated to the benzene ring) is irradiated with polarized light, the photosensitive functional group aligned in the polarization direction is obtained. Selectively reacts with light. When the discotic liquid crystal phase undergoes a photoreaction, the refractive index becomes lower in the polarization direction than before the reaction. Accordingly, when an optically anisotropic layer is formed using a discotic liquid crystalline compound having a photosensitive functional group (this layer is an optically uniaxial layer) and irradiated with polarized ultraviolet rays from a certain direction, the optically anisotropic layer is formed. An axial optically anisotropic layer can be produced. Thereby, an optically anisotropic layer having desired Re and Rth, in which the principal refractive index values nx, ny and ny in three directions are adjusted, can be formed by a simple method.

  By combining the above methods, a film having a plurality of domains in which both Re and Rth are different from each other can also be produced.

  The liquid crystal display device of the present invention is not limited in display mode, and may be any liquid crystal display device using any of twist alignment mode such as TN mode, vertical alignment mode such as VA mode, and horizontal alignment mode such as IPS mode. The effect of improving viewing angle characteristics can be obtained.

  The present invention will be described more specifically with reference to the following examples. The materials, reagents, amounts and ratios of substances, operations, and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples.

[Preparation of transparent film]
The transparent film was produced by the following method with reference to the method described in JP-A-2002-6138.
Polyvinyl alcohol (PVA-203, manufactured by Kuraray Co., Ltd.) was dissolved in a methanol / water mixed solvent (volume ratio: 20/80) to prepare a 5 mass% solution. This solution was applied to the surface of a Fujifilm Z-tack film using this solution as a support film using a bar coater. The coating layer was dried with warm air at 80 ° C. for 10 minutes.
To 1.0 g of the discotic liquid crystal compound (I-2) having the following structure, 10 mg of the following additive and 30 mg of the following photopolymerization initiator were added, and the resulting mixture was dissolved in methyl ethyl ketone to prepare a solution. .

The prepared solution was applied to the surface of the polyvinyl alcohol coating layer using a bar coater. A metal roller whose surface was heated to a predetermined temperature was brought into contact with the back surface of the support (the surface on the side where the coating layer was not formed) for 2 minutes. The heating temperature is shown in the table below.
Next, this coating layer (thickness 2 μm) is irradiated with non-polarized ultraviolet rays for 10 seconds by a 160 W ultraviolet irradiation device (UVL-58, manufactured by ULTRA-VIOLET PRODUCTS), and the orientation state of the discotic liquid crystalline molecules Fixed.
Next, the cured layer was irradiated with polarized ultraviolet rays having a wavelength of 290 to 310 nm at a temperature of 20 ° C. using a polarized ultraviolet irradiation device (manufactured by Nikon Technology Kobo Co., Ltd.) having a transmission filter and an interference filter. The irradiation time is shown in the following table.
As shown in the following table, it was confirmed that films having different Re and Rth can be produced under different conditions, specifically, different film heating temperatures and / or polarized ultraviolet irradiation times. Re and Rth were measured by combining a polarizing microscope (LV100POL) of Nikon with an optional senalmon compensator and tilting the sample to the front and ± 20 degrees to measure the phase difference. As for the wavelength, 550 nm which is a wavelength in the visible light region was used.
The results are shown in the table below.

According to the above results, transparent films composed of domain 1 and domain 2 having different Re and / or Rth were produced as follows.
First, when producing the domain 1, after applying the liquid of the mixture, the film is heated to one of the temperatures shown in the above table, and light is applied only to the part corresponding to the domain 1 (a in FIG. 1A). Using a photomask through which light is transmitted, non-polarized ultraviolet rays are irradiated and cured, and subsequently, polarized ultraviolet irradiation is performed for any one of the times shown in the above table, thereby producing a domain 1 exhibiting predetermined Re and Rth.
Thereafter, in the same manner, except that at least one of the heating temperature and the polarized UV irradiation time is different from the above, and another portion that transmits light only in the portion corresponding to the domain 2 (b in FIG. 1A). Domain 2 was produced using a photomask.
By this method, various transparent films were produced from domain 1 and domain 2 showing different Re and Rth.
In any film, the minimum diameter of domain 1 and domain 2 was 20 μm.

[Measurement of optical characteristics of liquid crystal display]
In the following table, oblique directions when transparent films composed of domain 1 and domain 2 having different Re and / or Rth are used as optical compensation films of a VA mode liquid crystal display device (LG-37GE2 manufactured by Sharp Corporation). The color shift value and light leakage amount during black display at (polar angle 60 °) are shown.
In addition, the arrangement of domain 1 and domain 2 of the transparent film did not correspond to the arrangement of the pixels and subpixels of the liquid crystal cell.
For comparison, the table shows the color shift value and the amount of light leakage during black display in an oblique direction (polar angle 60 °) when a uniform film that is not divided into domains is similarly used.

  From the results shown in the above table, it can be understood that Examples 1 to 4 of the present invention have good viewing angle characteristics, and in particular, the color shift amount in the oblique direction is reduced as compared with the comparative example. .

Similar experiments were performed with the minimum diameter of each domain being 1 μm, 100 μm, and 300 μm. As a result, the same results as in Table 2 were obtained at any minimum diameter. From this, the minimum diameter of each domain was 1 micrometer-300 micrometers, and it has confirmed that the effect of this invention was acquired.
The experiment was conducted even when the minimum diameter of each domain was 0.5 μm, but two domains could not be formed because the diameter was too small. In addition, although the experiment was performed even when the minimum diameter of each domain was 400 μm, a screen roughness thought to be caused by interference occurred.

Further, as a similar experiment, the optical film shown in FIGS. 1B to 1D and the VA mode liquid crystal display device having the optical film shown in FIG. It was prepared by the above method in the same manner as the optical film shown. Domain 1 corresponds to a part of each figure in each figure, and domain 2 corresponds to a part b of each figure in each figure. The minimum diameters of domain 1 and domain 2 in each figure were set to 1 μm, 20 μm, 100 μm, and 300 μm, respectively. Moreover, the ratio of the sum total of the area of the domain 1 and the sum total of the area of the domain 2 in all the produced films including the film produced in the said Examples 1-4 was equal.
The VA mode liquid crystal display device having the produced film was evaluated by the same method as described above. For all the domains shown in FIG. 1B to FIG. 1D, the same results as in Table 2 were obtained regardless of the size of the minimum diameter of the domains.

The top view of some examples of the transparent film which can be utilized for the liquid crystal display device of this invention is shown. It is a top view of the example of a domain which makes one pixel (pixel) in a liquid crystal cell a unit. It is a figure which shows typically an example of the combination of the transparent film and liquid crystal cell in the liquid crystal display device of this invention. It is a figure which shows typically the other example of the combination of a transparent film and a liquid crystal cell in the liquid crystal display device of this invention.

Explanation of symbols

10 Transparent film 12 Liquid crystal cell a, b Transparent film domain D1, D2, D3 Liquid crystal cell domain

Claims (6)

A liquid crystal display device having at least a liquid crystal cell divided into a plurality of domains and a transparent film, wherein the transparent film has in-plane retardation (Re) and / or thickness direction with respect to a wavelength λ nm in a visible light region. The retardation (Rth) is composed of two or more domains different from each other, and the domain of the transparent film and the domain of the liquid crystal cell are not correlated with respect to the arrangement and / or the size thereof. Liquid crystal display device. The liquid crystal display device according to claim 1, wherein the domains of the transparent film are arranged in a lattice shape or a zigzag shape. 3. The liquid crystal display device according to claim 1, wherein a minimum diameter of each domain of the transparent film is 1 μm to 300 μm. The Re and Rth of each domain at a wavelength λnm in the visible light region of the transparent film is within ± 20% of the average value of Re and Rth at the same wavelength of the transparent film. 4. The liquid crystal display device according to any one of items 3. The transparent film has a plurality of domains having Re of 40 to 50 nm at a wavelength λ nm in a visible light region, and a plurality of domains having Re of 50 to 60 nm at the same wavelength. The liquid crystal display device according to any one of the above. The transparent film has a plurality of domains having Rth of 180 to 200 nm at a wavelength λ nm in a visible light region and a plurality of domains having Rth of 200 to 220 nm at the same wavelength. The liquid crystal display device according to any one of the above.

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