KR20050024210A - Optical compensation film, liquid crystal display and polarizing plate - Google Patents

Abstract

PURPOSE: An optical compensation film, an LCD(Liquid Crystal Display), and a polarizing plate are provided to remarkably improve viewing angle characteristic and display quality of the LCD, and easily fabricate the polarizing plate. CONSTITUTION: An LCD cell has a pair of substrates(5,8) and a liquid crystal layer. The substrates are opposed to each other. The liquid crystal layer is disposed between the substrates. The first and the second polarizing films(1,14) are disposed at the outsides of the substrates. An optical compensation film is disposed between the second polarizing film and the LCD cell. The optical compensation film has a protection layer(12) and optical compensation layer(10). An alignment control direction(11) of the optical compensation layer and a delayed phase axis of the protection layer are nearly parallel to an absorbing axis of the polarizing film. The optical compensation film is specially applied to VA(Vertically Aligned) type LCD or IPS(In-Plane Switching) type LCD.

Description

Optical Compensation Film, Liquid Crystal Display and Polarizing Plate {OPTICAL COMPENSATION FILM, LIQUID CRYSTAL DISPLAY AND POLARIZING PLATE}

The present invention relates to a polarizing plate having a polarizing film, a pair of protective films sandwiching the polarizing film, and a liquid crystal display device using the same. In addition, the present invention also relates to an optical compensation film that contributes to improvement of viewing angle characteristics of a liquid crystal display device.

A liquid crystal display device usually has a liquid crystal cell and a polarizing plate. A polarizing plate consists of a protective film and a polarizing film, is obtained by dyeing and extending | stretching the polarizing film which consists of a polyvinyl alcohol film with iodine, and laminating | stacking both surfaces by a protective film. In a transmissive liquid crystal display device, this polarizing plate is attached to both sides of a liquid crystal cell, and also one or more optical compensation films may be arrange | positioned. In the reflective liquid crystal display device, the reflecting plate, the liquid crystal cell, one or more optical compensation films, and the polarizing plate are arranged in this order. The liquid crystal cell is composed of liquid crystal molecules, two substrates for encapsulating them, and an electrode layer for applying a voltage to the liquid crystal molecules. The liquid crystal cell displays ON / OFF due to the difference in the alignment state of the liquid crystalline molecules, and can be applied to any of the transmissive and reflective types, TN (Twisted Nematic), IPS (In-Plane Switching), and OCB (Optically Compensatory). Display modes such as Bend), VA (Vertically Aligned) and ECB (Electrically Controlled Birefringence) have been proposed.

Optical compensation films are used in various liquid crystal display devices in order to eliminate image coloring and to enlarge a viewing angle. As the optical compensation film, a stretched birefringent polymer film is conventionally used. It is also proposed to use an optical compensation film having an optically anisotropic layer formed of low molecular or polymer liquid crystalline molecules on a transparent support instead of the optical compensation film made of a stretched birefringent film. Since the liquid crystal molecules have various alignment forms, by using the liquid crystal molecules, optical properties that cannot be obtained with a conventional stretched birefringent polymer film can be realized. Moreover, the structure which doubles a protective film and an optical compensation film is also proposed by adding birefringence to the protective film of a polarizing plate.

The optical properties of the optical compensation film are determined according to the optical properties of the liquid crystal cell, specifically, the difference in display mode as described above. By using the liquid crystal molecules, an optical compensation film having various optical properties corresponding to various display modes of the liquid crystal cell can be manufactured. In the optical compensation film using liquid crystalline molecules, one corresponding to various display modes has already been proposed. For example, in a TN mode liquid crystal cell, optical compensation is performed by an optical compensation film formed by fixing an inclined alignment state on a substrate surface while eliminating the torsion structure of liquid crystal molecules by applying voltage, thereby preventing light leakage in an oblique direction during black display. To improve the visual characteristics of contrast (see JP-A-6-214116). Moreover, about the optical compensation film for parallel orientation liquid crystal cells, it is described about what combines the optical compensation of the liquid crystalline molecule parallel-aligned to the board | substrate surface, and the viewing angle characteristic improvement of the orthogonal transmittance of a polarizing plate at the time of black display of voltage unattended state ( See Japanese Patent Application Laid-Open No. 9-292522). In the IPS mode liquid crystal cell, at the time of black display in an unattended voltage state, optical compensation is performed by an optical compensation film made of liquid crystal molecules oriented parallel to the substrate surface, and the sheet serves to improve the viewing angle characteristic of the orthogonal transmittance of the polarizing plate. (See Japanese Laid-Open Patent Publication No. Hei 10-54982). In the liquid crystal cell of the OCB mode, the liquid crystal molecules at the center of the liquid crystal layer are vertically aligned by voltage application, and the optically compensated tilted liquid crystal layer is optically compensated by the optical compensation film near the substrate interface to improve the viewing angle characteristic of the black display. (See US Patent 5805253). In the VA mode liquid crystal cell, the viewing angle characteristic of the black display in which the liquid crystal molecules are vertically aligned with respect to the substrate surface in a voltage-free state is improved by the optical compensation film (see Patent No. 2866372).

The conventional optical compensation film for TN mode liquid crystal cells makes it possible to optically compensate the liquid crystal cell more accurately than conventionally by using a film made of liquid crystalline molecules instead of the stretched birefringent polymer film. However, even when liquid crystal molecules are used, it is very difficult to completely optically compensate the liquid crystal cell without problems. For example, the optical compensation film proposed conventionally shows that the light leakage from the inclination direction of the polarizing plate at the time of black display is seen, and the viewing angle is not fully expanded (to the extent which can theoretically be expected). Similarly, optical leakage is also seen in conventional IPS, OCB, and VA compensation optical compensation films. In addition, in the optical compensation films for IPS and VA mode liquid crystal cells, since the optical compensation is performed only on the stretched birefringent polymer film, it is necessary to use a plurality of films, and as a result, the thickness of the optical compensation film is increased, which is disadvantageous for thinning the display device. . In addition, since an adhesive layer is used for laminating a stretched film, the adhesive layer shrinks due to a change in temperature and humidity, so that defects such as peeling and warping between the films may occur.

This invention is made | formed in view of the said subject, Comprising: It aims at providing the liquid crystal display device which is simple in structure, and not only the display quality but also the viewing angle is remarkably improved, especially VA type liquid crystal display device and IPS type liquid crystal display device. In addition, an object of the present invention is to provide a polarizing plate which not only has a polarizing function but can also contribute to enlargement of the viewing angle of a liquid crystal display device and can be easily manufactured. Another object of the present invention is to provide an optical compensation film which contributes to the improvement of viewing angle characteristics of a liquid crystal display device, particularly an IPS type or VA type liquid crystal display device.

The subject of this invention was achieved by the optical compensation film of following (1) and (2), the liquid crystal display device of following (3)-(6), and the polarizing plate of following (7)-(9).

(1) a pair of opposingly arranged substrates having electrodes on at least one side, a liquid crystal layer sandwiched between the substrates, and at least one polarizing film disposed outside the liquid crystal layer, wherein the thickness d (μm) of the liquid crystal layer and An optical compensation film used for a liquid crystal display device having a product Δn · d of refractive index anisotropy (Δn) of 0.1 to 1.0 μm,

An optical compensation layer comprising a protective film in contact with the polarizing film and a compound having a discotic structural unit,

The protective film at any wavelength λ in the visible light region,

−30 (nm) ≦ {(nx−ny) × d ₂ } ≦ 50 (nm), and

-50 (nm) ≤ [{(nx + ny) / 2-nz} × d ₂ ] ≤300 (nm)

(Wherein d ₂ (nm) is the thickness of the protective film, nx and ny (where ny <nx) is the in-plane major mean refractive index, nx is the major mean refractive index in the thickness direction, and nx, ny and nz are respectively) Orthogonal to each other),

And an orientation control direction of the optical compensation layer and a slow axis of the protective film are disposed substantially parallel to the absorption axis of the polarizing film.

(2) a liquid crystal layer comprising a pair of opposing substrates having at least one electrode on one side and a nematic liquid crystal material sandwiched between the substrates and oriented almost parallel to the surface of the pair of substrates when no voltage is applied; An optical compensation film for use in a liquid crystal display device having a liquid crystal cell and a first polarizing film and a second polarizing film respectively disposed outside the liquid crystal cell,

The optical compensation film is disposed between the second polarizing film and the liquid crystal cell, and at least has a protective film and an optical compensation layer in contact with the second polarizing film,

The protective film at any wavelength λ in the visible light region,

−30 (nm) ≦ {(nx−ny) × d ₂ } ≦ 50 (nm), and

-50 (nm) ≤ [{(nx + ny) / 2-nz} × d ₂ ] ≤300 (nm)

(Wherein d ₂ (nm) is the thickness of the protective film, nx and ny (where ny <nx) is the in-plane major mean refractive index, nx is the major mean refractive index in the thickness direction, and nx, ny and nz are respectively) Orthogonal to each other),

The optical compensation layer is composed of molecules of a compound having a discotic structural unit, and the discotic surface is substantially perpendicular to the film surface, and

And an alignment control direction of the optical compensation layer, a slow axis of the protective film, and an absorption axis of the second polarizing film, respectively, substantially parallel to each other.

(3) A liquid crystal display device having a pair of substrates disposed opposite each other having electrodes on at least one side, a liquid crystal layer sandwiched between the substrates, and a first polarizing plate disposed outside the liquid crystal layer,

The product (DELTA) n * d of the thickness d (micrometer) of the said liquid crystal layer and refractive index anisotropy (DELTA) n is 0.1-1.0 micrometer,

The first polarizing plate has a polarizing film and a pair of protective films sandwiching the polarizing film,

At least one of the pair of protective films has a slow axis substantially coincident with the direction in which the average refractive index of the film surface is maximized, and the slow axis of the protective film closer to the liquid crystal layer and the absorption axis of the polarizing film cross each other. ,

Of the pair of protective films, the protective film disposed on the side close to the liquid crystal layer has a thickness d ₁ (nm) and has three average refractive indices nx, ny, and nz in the x, y, and z axis directions orthogonal to each other, In the case where the main average refractive index in the plane parallel to the surface of the liquid crystal layer is nx and ny (where ny <nx) and the main average refractive index in the thickness direction of the liquid crystal layer is nz, at an arbitrary wavelength? Of the visible light region,

−30 (nm) ≦ {(nx−ny) × d ₁ } ≦ 50 (nm), and

-50 (nm) ≤ [{(nx + ny) / 2-nz} × d ₁ ] ≤300 (nm)

Liquid crystal display that satisfies the relationship.

In the liquid crystal display device of (3), the polarizing plate in which at least one in-plane slow axis of a pair of protective films intersects the absorption axis of a polarizing film is used as a polarizing plate. This polarizing plate not only contributes to the polarization function but also enlarges the viewing angle of the display device. Therefore, the liquid crystal display device, in particular, VA (Vertical Alignment) type and IPS (In-Plane Switching), in which not only the display quality but also the viewing angle is remarkably improved by a simple configuration ) Liquid crystal display device can be provided. The polarizing plate can be easily manufactured by laminating a pair of protective films and a total of three polymer films of the polarizing film in roll-to-roll by using a polarizing film produced by using an oblique stretching method, thereby improving productivity of the liquid crystal display device. Contribute to. In addition, since the protective film of the said polarizing plate can also function as an optical compensation layer, in such an aspect, it becomes a liquid crystal display device excellent in display quality with a simpler structure.

Further, in the liquid crystal display device of (3), since the absorption axis of the polarizing film of the polarizing plate disposed by sandwiching the liquid crystal layer is orthogonal, the polarizing plate transmittance is low and high contrast can be obtained in the aspect of the normally black type liquid crystal display device. have.

(4) The liquid crystal display device according to (2), wherein the liquid crystal layer contains a nematic liquid crystal material, and at the time of black display, liquid crystal molecules of the nematic liquid crystal material are oriented almost perpendicular to the surface of the pair of substrates.

The liquid crystal display device (4) is an aspect in which the liquid crystal material is almost vertically aligned at the time of black display, but can reduce light leakage when viewed in the inclined direction which is a problem in such an aspect. The present embodiment may be a VA type in which the liquid crystal molecules in the liquid crystal cell are generally vertically aligned in a voltage-free state, or an OCB type, ECB type, or TN type in which the liquid crystal molecules are vertically aligned in a high voltage applied state. The liquid crystal display device of (4) is a VA type sun in which the liquid crystal molecules are inclined with respect to the substrate normal by application of voltage, and since the liquid crystal molecules are inclined in one direction, variations in luminance and color tone occur depending on the viewing angle. This can be reduced by constructing and averaging one pixel into two or more (preferably 4 or 8 or more) liquid crystal regions having different initial alignment states.

(5) The liquid crystal display device according to (3), wherein the liquid crystal layer contains a nematic liquid crystal material, and at the time of black display, liquid crystal molecules of the nematic liquid crystal material are oriented almost parallel to the surface of the pair of substrates.

Since the retardation Rth in the thickness direction of the protective film of the polarizing plate is in the above range, the liquid crystal display device of (5) greatly contributes to the improvement of the viewing angle characteristic at the time of black display of the liquid crystal display device and also functions as an optical compensation layer. can do. Moreover, since in-plane retardation Re of the said polarizing plate protective film is the said range, it contributes greatly to the leakage light prevention when it sees from the inclination direction at the time of orthogonal to a polarizing plate absorption axis. Further, at least one of {(nx-ny) × d ₁ } and [{(nx + ny) / 2-nz} × d ₁ ] may be outside the above range, but in such a case, a protective film and a liquid crystal cell (liquid crystal layer and substrate) It is preferable that at least one optical compensation film is disposed on at least one side. For example, what is necessary is just to arrange | position one protective film, one optical support, and one coating type optical compensation layer.

(6) a liquid crystal layer comprising a pair of opposingly arranged substrates having at least one electrode on one side, which is sandwiched by the substrate and oriented almost parallel to the surface of the pair of substrates when no voltage is applied; A liquid crystal display device comprising at least a liquid crystal cell comprising a liquid crystal cell and a first polarizing plate and a second polarizing plate respectively disposed outside the liquid crystal cell.

The first polarizing plate comprises at least a polarizing film and a protective film formed on a surface close to the liquid crystal cell of the polarizing film,

The second polarizing plate comprises at least a polarizing film and a protective film formed on a surface close to the liquid crystal cell of the polarizing film and an optical compensation layer (however, the protective film may also serve as this optical compensation layer),

The protective film formed in the surface close to the liquid crystal cell of the polarizing film of the second polarizing plate at any wavelength λ in the visible light region,

−30 (nm) ≦ {(nx−ny) × d ₂ } ≦ 50 (nm), and

-50 (nm) ≤ [{(nx + ny) / 2-nz} × d ₂ ] ≤300 (nm)

(Wherein d ₂ (nm) is the thickness of the protective film, nx and ny (where ny <nx) is the in-plane major mean refractive index, nx is the major mean refractive index in the thickness direction, and nx, ny and nz are respectively) Orthogonal to each other),

The optical compensation layer is composed of a compound having a discotic structural unit, and the discotic surface of the compound is substantially perpendicular to the substrate surface,

And a slow axis of the protective film formed on a surface close to the liquid crystal cell of the second polarizing plate and an absorption axis of the second polarizing plate are substantially parallel to each other.

In the liquid crystal display device of (6), by making the retardation value of the protective film of an up-and-down polarizing plate asymmetric, it greatly contributes to the prevention of the leakage light in the case of seeing from the diagonal direction. When the retardation value of the protective film arrange | positioned between the liquid crystal cell of a up-and-down polarizing plate and a polarizing film is made especially asymmetric, it is effective for the reduction of the oblique direction leakage light in the aspect which the absorption axis of an up-and-down polarizing plate orthogonally crosses.

The liquid crystal display device of (6) is an aspect in which the liquid crystal material is oriented almost in parallel during black display, and is, for example, an IPS type in which liquid crystal molecules are aligned in parallel with the substrate surface in black in the absence of voltage. Even in these aspects, the polarizer contributes to enlarged viewing angle. In this aspect, it is preferable to set the retardation value of the optically anisotropic layer arrange | positioned between the said protective film, a protective film, and a liquid crystal cell to 2 times or less of the value of (DELTA) n * d of a liquid crystal layer.

The liquid crystal display device of (6) further comprises at least one polymer film or at least one layer of liquid crystal compound between the first and / or second polarizing plates and a liquid crystal cell composed of the pair of substrates and the liquid crystal layer. It may have an optically anisotropic layer consisting of (however, this protective film may have a configuration also serving as this optical compensation layer).

In the liquid crystal display device of this aspect, since the polymer film or optically anisotropic layer having optical compensation ability is provided, it is excellent in the above-described effects, in addition to enlargement of the viewing angle and improvement of display characteristics.

(7) It has a polarizing film and a pair of protective film which has refractive index arrange | positioned by sandwiching this polarizing film, The said protective film is thickness d <_1> (nm) and three averages in the x, y, and z-axis directions orthogonal to each other, respectively. In the case where the refractive indexes nx, ny and nz are included, and the in-plane main average refractive index is nx and ny (where ny <nx) and the main average refractive index in the thickness direction is nz, at an arbitrary wavelength? Of the visible light region,

−30 (nm) ≦ {(nx−ny) × d ₁ } ≦ 50 (nm), and

-50 (nm) ≤ [{(nx + ny) / 2-nz} × 2] ≤300 (nm)

Polarizer to satisfy.

In the polarizing plate of (7), at least one of the pair of protective films has a retardation (Re) in a predetermined plane or a retardation (Rth) in the thickness direction, and absorbs the slow axis of any one of the protective films and the polarizing film. The axes are substantially parallel or orthogonal. This polarizer not only contributes to the polarization function but also enlarges the viewing angle of the liquid crystal display device, particularly VA (Vertical Alignment) type and IPS (In-Plane Switching) type liquid crystal display. In addition, since the polarizing plate can be easily manufactured by laminating a pair of protective films and a total of three polymer films of the polarizing film in roll-to-roll by using a polarizing film produced by using an oblique stretching method, it also contributes to the improvement of productivity. do. In addition, since the protective film of the said polarizing plate can also function as an optical compensation layer, such an aspect not only contributes to the expansion of the viewing angle of a liquid crystal display device, but also optical compensation.

(8) The polarizing plate according to (7), wherein the slow axis of any one of the protective films of the polarizing plate and the absorption axis of the polarizing film intersect.

In the polarizing plate of (8), since the absorption axis of the polarizing film of the polarizing plate and the slow axis of the protective film (the protective film far from the liquid crystal layer) are orthogonal to each other, in addition to the above-described effect, mechanical measures such as dimensional change of the polarizing plate and prevention of curl Reliability is improved. In addition, when the protective film slow axis close to the liquid crystal layer and the absorption axis of the polarizing film are orthogonal, leakage light from the inclination direction in black display can be reduced. In addition, when an optical anisotropy is arrange | positioned so that a slow axis may cross | intersect a polarizing film absorption axis between a liquid crystal layer and a protective film, it is not necessary to necessarily cross | intersect a protective film slow axis and a polarizing film absorption axis. At this time, it is preferable that an optically anisotropic layer has the same effect with a coating film or a stretched film, and is larger than the retardation value of a protective film.

Both protective films have birefringence, and the slow axes of the protective film on the side closer to the liquid crystal layer are substantially perpendicular to each other. In an aspect in which the slow axes are perpendicular to each other, the birefringence of each of the protective films cancels each other, thereby reducing the deterioration of the optical characteristics at the time of vertical incidence of the liquid crystal display device. On the other hand, in an aspect where the slow axes are parallel to each other, when there is a residual phase difference in the liquid crystal layer, the phase difference can be compensated for by the birefringence of the protective film.

In addition, that "the slow axis of a protective film and the absorption axis of the said polarizing film cross | intersect" here means that the absorption axis of a polarizing film is not parallel to the slow axis of a protective film. The angle between the absorption axis direction of the polarizing film and the slow axis of the protective film (regardless of before or after cutting of the polarizing film) is preferably 10 ° to 90 °, more preferably 20 ° to 70 ° and 80 ° to 90 °. °, more preferably 40 ° -50 ° and 85 ° -90 °, particularly preferably 43-47 ° and 87 ° -90 °.

In addition, you may use two protective films, and either slow axis may cross | intersect a polarizing film absorption axis. At this time, two protective films can be adhere | attached with an adhesion layer or an adhesive layer.

(9) An optical compensation layer disposed on either surface of the pair of protective films, wherein the optical compensation layer is made of a compound having a discotic structural unit, and the discotic surface of the compound is formed on the polarizing film. The polarizing plate of (7) or (8) which is substantially vertically aligned, and the orientation control direction of the said optical compensation layer, the slow axis of the protective film which contact | connects this optical compensation layer, and the absorption axis of the said polarizing film are substantially parallel, respectively.

In the polarizing plate of (9), since the direction of the said slow axis of a pair of protective film which a polarizing plate has is coincident, the effect of the improvement of the mechanical stability of a polarizing plate and the uniformity of optical performance is acquired in addition to the said effect.

In addition, in this specification, "45 degree", "parallel", or "orthogonal" means that it exists in the range of less than an exact angle ± 5 degrees. It is preferable that it is less than 4 degrees, and, as for the error with an exact angle, it is more preferable that it is less than 3 degrees. In addition, with respect to angle, "+" means clockwise rotation direction, and "-" shall mean counterclockwise rotation direction. In addition, a "ground axis" means the direction in which a refractive index becomes largest. In addition, a "visible light region" means that it is 380 nm-780 nm. In addition, the measurement wavelength of refractive index is a value in (lambda) = 550 nm of visible range unless there is particular notice.

In the present specification, unless otherwise specified, a "polarizing plate" refers to both a polarizing plate and a polarizing plate cut to a size to be mounted on a long polarizing plate and a liquid crystal device (in this specification, "foundation" also includes "punching" and "cutting", etc.). Used to include. In addition, in this specification, although a "polarizing film" and a "polarizing plate" are distinguished and used, a "polarizing plate" shall mean the laminated body which has a transparent protective film which protects this polarizing film on at least one surface of a "polarizing film."

Embodiment of the invention

Hereinafter, the structural member of one Embodiment of the liquid crystal display device of this invention is demonstrated sequentially. 1 and 2 are schematic diagrams of one embodiment of a liquid crystal display device of the present invention.

[LCD]

First, the liquid crystal display device shown in FIG. 1 has the upper polarizing film 1 and the lower polarizing film 14 arrange | positioned by sandwiching liquid crystal cells 5-8 and a liquid crystal cell. The polarizing films 1 and 14 are sandwiched by a pair of transparent protective films 3 and 3a and 12 and 12a, respectively. The liquid crystal cells 5 to 8 consist of a liquid crystal cell upper substrate 5, a liquid crystal cell lower substrate 8, and liquid crystal molecules 7 sandwiched therebetween, and the liquid crystal molecules 7 are the substrates 5 and 8. The orientation direction is controlled by the direction of the rubbing process and the orientation film material which were performed on the opposing surface of.

The upper polarizing plate consists of a pair of transparent protective films 3a and 3 and the polarizing film 1 sandwiched by them (the transparent protective film 3 is arranged on the side close to the liquid crystal cell (5 to 8 in FIG. 1). box). The absorption axis 2 of the polarizing film 1 intersects with the slow axis 4 of the transparent protective film 3. Specifically, the angle α of the absorption axis 2 of the polarizing film 1 and the slow axis 4 of the transparent protective film 3 is preferably 10 ° to 90 °, more preferably 20 ° to 70 °, furthermore. Preferably it is 40-50 degree, Especially preferably, it is 43-47 degree. Although it does not restrict | limit especially about the angle which the slow axis of the other transparent protective film 3a (it is arrange | positioned at the side remote from the liquid crystal cells 5-8), and the absorption axis 2 of the polarizing film 1 form said alpha, It is equal to the preferred range of. Moreover, it is preferable that the relationship of the absorption axis 15 of the lower polarizing film 14 and the slow axis 13 of the protective film film 12 arrange | positioned near the liquid crystal cell is also the same.

It is preferable that the slow axes of each of the pair of transparent protective films 3a and 3 are substantially parallel to each other. When the slow axis of a pair of transparent protective film is parallel, since the improvement of the mechanical stability of a polarizing plate and the uniformity effect of optical performance are acquired, it is preferable. Moreover, when the slow axis of the transparent protective film arrange | positioned far from a liquid crystal cell and the absorption axis of a polarizing film are substantially parallel, mechanical reliability, such as a dimensional change of a polarizing plate and prevention of curl, will improve. The same effect is obtained even if the slow axis of the transparent protective film which is disposed away from the liquid crystal cell and the absorption axis of the polarizing film are orthogonal, and if the thickness and the rigidity of the transparent protective film are sufficient, the absorption axis of the polarizing film and a pair of The same effect is obtained even if the slow axes of the protective film cross each other at different angles. In addition, you may make two protective films arrange | positioned near a liquid crystal layer and intersect the slow axis of one protective film with a polarizing plate absorption axis.

In Fig. 1, the slow axes 4 and 13 of the protective films 3 and 12 on the side close to the liquid crystal cell of the polarizing film 1 and the polarizing film 14 of the upper and lower polarizing plates are substantially parallel or perpendicular to each other. It is desirable to. When the slow axes 4 and 13 of the transparent protective films 3 and 12 are orthogonal to each other, the birefringence of each of the protective films cancels each other, so that the optical characteristics of the light vertically incident on the liquid crystal display can be reduced. In the aspect in which the slow axes 4 and 13 are parallel to each other, when there is a residual phase difference in the liquid crystal layer, the birefringence of the protective film can compensate for this phase difference.

The protective film 3 disposed on the liquid crystal cell side of the upper polarizing film 1 or the protective film 12 disposed on the liquid crystal cell side of the lower polarizing film 14 has the following optical characteristics at an arbitrary wavelength? Of the visible light region. Satisfies.

−30 (nm) ≦ {(nx−ny) × d ₂ } ≦ 50 (nm), and

-50 (nm) ≤ [{(nx + ny) / 2-nz} × d ₂ ] ≤300 (nm)

Where d ₂ (nm) is the thickness of the protective film, nx and ny (where ny <nx) is the in-plane major mean refractive index, nx is the major mean refractive index in the thickness direction, and nx, ny and nz are Each is orthogonal to each other. In the present invention, by arranging a protective film having such an optical characteristic by intersecting the slow axis with the polarization axis of the polarizing film as described above, the protective film has an optical compensation function of the liquid crystal cell. The manufacturing method, material, etc. of a protective film are mentioned later.

The liquid crystal cell is composed of an upper substrate 5 and a lower substrate 8 and a liquid crystal layer formed of liquid crystal molecules 7 sandwiched therebetween. An alignment film (not shown) is formed on a surface (hereinafter sometimes referred to as an "inner surface") in contact with the liquid crystal molecules 7 of the substrates 5 and 8, and a rubbing treatment or alignment film material formed on the alignment film or the like is provided. By this, the orientation of the liquid crystal molecules 7 in the voltage unapplied state or low applied state is controlled. Moreover, the transparent electrodes (not shown) which can apply a voltage to the liquid crystal layer which consists of liquid crystal molecules 7 are formed in the inner surface of the board | substrates 5 and 8.

It does not specifically limit about the display mode of a liquid crystal layer, The liquid crystal layer of any display mode, such as VA mode, IPS mode, ECB mode, TN mode, and OCB mode, may be sufficient. In this invention, the product (DELTA) n * d of the thickness d (micrometer) of a liquid crystal layer and refractive index anisotropy (DELTA) n shall be 0.1-1.0 micrometer. The optimum value of Δn · d differs depending on the display mode. In the transmission mode, in the VA, IPS, and ECB types that do not have a torsion structure, the range is 0.2 to 0.4 µm, and the TN type is 0.2 to 0.5 µm, which varies depending on the size of the torsion angle. The 1.0 μm range is the optimal value. In these ranges, since the white display luminance is high and the black display latitude is small, a bright and high contrast display device is obtained. In addition, although the aspect of the display apparatus of the transmissive mode provided with the upper polarizing plate and the lower polarizing plate was shown in FIG. 1, this invention may be the sun of the reflection mode provided with only one polarizing plate, and in such a case, the optical path in a liquid crystal cell In terms of being doubled, the optimum value of Δn · d is about 1/2 of the above value.

About the absorption axes 2 and 15 of the polarizing films 1 and 14, the slow axis directions 4 and 13 of the protective films 3 and 12, and the orientation direction of the liquid crystal molecules 7, the material used for each member Can be adjusted to an optimum range depending on the display mode, the laminated structure of the members, and the like. For example, in the aspect of the normally black type of VA type or IPS type, in order to obtain high contrast, the absorption axes 2 and 15 of the polarizing films 1 and 14 are arrange | positioned so that they may mutually orthogonally cross. However, the liquid crystal display device of the present invention is not limited to this configuration.

Next, the driving principle of the embodiment of the liquid crystal display device in VA mode will be described with reference to FIG.

In the present embodiment, an example is described in which an active drive is performed using a nematic liquid crystal having negative dielectric anisotropy as the field effect type liquid crystal. In the non-driven state in which the liquid crystal display device shown in FIG. 1 does not apply a driving voltage to each of the transparent electrodes (not shown) of the liquid crystal cell substrates 5 and 8, the liquid crystal molecules 7 in the liquid crystal layer are formed of the substrates 5 and. Oriented approximately perpendicular to the plane of 8), and as a result, the polarization state of the passing light hardly changes. Since the absorption axes 2 and 15 are orthogonal, the light incident from the lower side (for example, the back electrode) is polarized by the polarizing film 14 and passes through the liquid crystal cells 5 to 8 while maintaining the polarization state. It is blocked by the polarizing film 1. That is, in the liquid crystal display of FIG. 1, ideal black display is realized in a non-driven state. On the other hand, in the driving state in which the driving voltage is applied to the transparent electrode (not shown), the liquid crystal molecules 7 are inclined in a direction parallel to the surfaces of the substrates 5 and 8, and the light passing therethrough is such inclined liquid crystal molecules. The polarization state is changed by (7). Therefore, the light incident from the lower side (for example, the back electrode) is polarized by the polarizing film 14, and the polarization state is changed by passing through the liquid crystal cells 5 to 8 again, and passes through the polarizing film 1. That is, in the liquid crystal display device shown in FIG. 1, white display is obtained in a driving state.

In this case, since an electric field is applied between the upper and lower substrates 5 and 8, a liquid crystal material having negative dielectric anisotropy such that the liquid crystal molecules 7 respond perpendicularly to the electric field direction is used. Moreover, when an electrode is formed only in either one of the board | substrates 5 and 8, and an electric field is applied in the horizontal direction parallel to a board | substrate surface, the liquid crystal material can use what has a positive dielectric anisotropy.

The VA mode features high speed response and high contrast. However, the liquid crystal display of the conventional VA mode has a problem that the contrast is high in the front but deteriorates in the inclined direction. Since the liquid crystal molecules 7 are oriented perpendicular to the surfaces of the substrates 5 and 8 at the time of black display, the birefringence of the liquid crystal molecules 7 is hardly observed when viewed from the front, so that the transmittance is low and high contrast is obtained. However, when observed in the oblique direction, birefringence occurs in the liquid crystal molecules 7. In addition, although the crossing angles of the absorption axes 2 and 15 of the up-and-down polarizing film 1 and 14 are orthogonal at 90 degrees from the front, they are larger than 90 degrees when viewed from the inclined direction. Because of these two factors, leakage light occurs in the inclined direction, and the contrast decreases. In the liquid crystal display device of FIG. 1, the transparent protective film 3 showing the predetermined optical characteristics is arranged on the side close to the liquid crystal cell of the polarizing film 1, and the slow axis 4 thereof is the absorption axis of the polarizing film 1 ( By arranging to intersect with 2) or on the side close to the liquid crystal cell of the polarizing film 14, the slow axis 13 is made into the transparent protective film 12 which shows predetermined optical characteristic, and the absorption axis of the polarizing film 14 By intersecting with (15), the viewing angle characteristic of the transmittance | permeability in black display is improved and wide viewing angle is achieved.

In addition, since the liquid crystal molecules 7 are inclined at the time of white display, the magnitude of the birefringence of the liquid crystal molecules 7 when observed in the inclined direction is different in the inclined direction and the reverse direction, and a difference occurs in luminance and color tone. A structure called a multi-domain that divides one pixel of the apparatus into a plurality of regions is preferable because the viewing angle characteristic of luminance and color tone is improved. Specifically, by constructing and averaging each pixel in two or more regions (preferably 4 or 8) where the initial alignment states of liquid crystal molecules differ from each other, variations in luminance and color tone depending on the viewing angle can be reduced. The same effect can be obtained even when each pixel is constituted by two or more regions different from each other in which the alignment directions of the liquid crystal molecules are continuously changed in the voltage application state.

In order to form a plurality of regions in which the alignment directions of the liquid crystal molecules 7 differ in one pixel, for example, slits or protrusions are formed on the electrodes to change the electric field direction or to make the electric field density vary. It is available. In order to obtain a uniform viewing angle in the entire direction, the number of divisions may be increased, but by setting it as 4 divisions or 8 divisions or more, a substantially uniform viewing angle is obtained. In particular, at eight divisions, the polarizing plate absorption axis can be set at any angle, which is preferable.

In the domain boundary of each domain, the liquid crystal molecules 7 tend to be difficult to respond. In the normally black mode such as the VA mode, black display is maintained, so that a decrease in luminance becomes a problem. Therefore, the chiral agent can be added to the liquid crystal material to reduce the boundary region between the domains. On the other hand, since the white display state is maintained in the normally white mode, the front contrast decreases. Therefore, what is necessary is just to form light shielding layers, such as a black matrix which covers the area | region.

There are two types of driving methods in the liquid crystal display device, an active matrix and a passive matrix. A liquid crystal display device used in a notebook computer or a flat-panel television or the like generally uses a thin film transistor of an active matrix. When the absorption axes 2 and 15 of the polarizing films 1 and 14 intersect at substantially 45 ° with respect to the wiring for sending an electric signal to the thin film transistor of the active matrix, the viewing angle characteristic is preferable because of the left-right symmetry structure. The same is true in the TN and OCB modes as well as the VA mode. If the absorption axis of the polarizing plate is parallel or perpendicular to the long side of the liquid crystal cell substrate, it is necessary to wire in consideration of the crossing angle between the signal line and the absorption axis. However, as shown in FIG. 1, the absorption axis of the polarizing plate is originally 45 to the long side of the liquid crystal cell substrate. By intersecting with °, if the signal line is simply designed to be parallel or perpendicular to the long side of the liquid crystal cell substrate, right and left symmetrical viewing angles are obtained. From this viewpoint, the absorption axes 2 and 15 of the polarizing films 1 and 14 in Fig. 1 are ideally intersected by + 45 ° or -45 ° with respect to the long sides of the liquid crystal cell substrates 5 and 8. However, in consideration of the case where the signal line is not a straight line, it is preferable to cross at 45 ° ± 10 ° or −45 ° ± 10 °.

In the VA mode liquid crystal cell, for example, the dielectric anisotropy is negative between the upper and lower substrates 5 and 8, and the alignment of the liquid crystal molecules is performed by rubbing alignment of nematic liquid crystal materials of Δn = 0.0813 and Δε = -4.6 or the like. The director showing the direction, so-called tilt angle, can be produced at about 89 °. Although it does not restrict | limit especially about the thickness d of a liquid crystal layer, When using the liquid crystal of the characteristic of the said range, it can set to about 3.5 micrometers. Since the brightness at the time of white display is changed by the magnitude of the product Δn · d of the thickness d and the refractive index anisotropy Δn, it is preferable to set Δn · d so as to be in the range of 0.2 to 0.5 μm. In addition, in the VA mode liquid crystal display device, the addition of the chiral material generally used in the TN mode liquid crystal display device is rarely used because it deteriorates the dynamic response characteristics, but may be added to reduce the orientation defect. . In addition, in the case of the multi-domain structure as described above, it is advantageous to adjust the orientation of the liquid crystal molecules in the boundary region between the respective domains.

In the above-described various liquid crystal display modes, the VA mode among the so-called normally black modes in which the black display is displayed when no voltage is applied or when low voltage is applied and the white display when high voltage is applied has been described. It is not limited to this, The sun using the IPS mode which is another normally black mode may be sufficient. The solar cell may be a solar cell using a normally white mode in which white display is performed when no voltage is applied or low voltage is applied, and black display is applied when high voltage is applied, or a liquid crystal cell of OCB mode, ECB mode, or TN mode may be used. In addition, a liquid crystal cell in which the liquid crystal molecules of the nematic liquid crystal material are aligned substantially parallel to the surface of the substrate during black display may be used. Specifically, the liquid crystal molecules may be aligned in parallel with the substrate surface in a state where no voltage is applied, and thus black display may be performed. It is also possible to use a liquid crystal cell of IPS mode or ECB mode. Further, in this aspect in order to obtain the effect of improving viewing angle, (nx-ny) × d ₁ The value of the protective film of the polarizing plate is preferably set around the value of Δn and d of the liquid crystal layer.

The liquid crystal display device of the present invention is not limited to the configuration shown in FIG. 1 and may include other members. For example, you may arrange | position a color filter between a liquid crystal cell and a polarizing film. In addition, as described below, an optical compensation film may be separately disposed between the liquid crystal cell and the polarizing plate. Moreover, when using as a transmission type, the backlight which uses a cold cathode or a hot cathode fluorescent tube, or a light emitting diode, a field emission element, and an electroluminescent element as a light source can be arrange | positioned at the back surface. In addition, the liquid crystal display device of the present invention may be a reflection type, and in such a case, it is sufficient to arrange one polarizing plate on the observation side, and a reflection film is provided on the rear surface of the liquid crystal cell or on the inner surface of the lower substrate of the liquid crystal cell. Of course, the front light using the light source may be formed on the liquid crystal cell observation side.

The liquid crystal display device of the present invention includes an image direct view type, an image projection type, and a light modulation type. The present invention is particularly effective when applied to an active matrix liquid crystal display device using a three-terminal or two-terminal semiconductor element such as a TFT or a MIM. Of course, the aspect applied to the passive matrix liquid crystal display device represented by STN type called time division drive is also effective.

The present invention aims to improve the viewing angle of the liquid crystal display device by setting the slow axis of the transparent protective film of the polarizing plate and the absorption axis of the polarizing film to a predetermined relationship. However, when the optical compensation film is disposed between the polarizing plate and the liquid crystal cell, the viewing angle is further increased. It is preferable because it is improved. The optical compensation film is not particularly limited and may be of any configuration as long as it has optical compensation performance. Examples thereof include a birefringent polymer film and a laminate of an optically anisotropic layer composed of a transparent support and liquid crystal molecules formed on the transparent support. In the latter aspect, the transparent protective films 3 and 12 on the side close to the liquid crystal layer of the polarizing plate may serve as the support of the optically anisotropic layer.

In order to improve the viewing angle in VA mode, a method of using a retardation plate having positive refractive anisotropy and a retardation plate having negative refractive anisotropy is described in Japanese Patent Laid-Open No. 10-153802. Can be applied. The retarder has three average refractive indices nx, ny, and nz in the x, y, and z-axis directions orthogonal to each other, respectively, and when nx and ny and in-plane average refractive indices are nz, nx, ny = There are a retardation plate (hereinafter referred to as "optical anisotropic layer A") which becomes nz and nx> ny, and a retardation plate (hereinafter referred to as "optical anisotropic layer B") which becomes nx = ny, nz and nx> nz. When the laminated body of the said optically anisotropic layer A and the said optically anisotropic layer B is used as an optical compensation film, the leakage light at the time of seeing from the diagonal direction of the black display of VA mode can be prevented. In addition, as described above, when the absorption axes 2 and 15 of the upper polarizing film 1 and the lower polarizing film 14 are arranged orthogonally, when viewed in the oblique direction, the crossing angle is shifted at right angles, and the leakage light is increased. there is a problem. It is known that this leakage light can be reduced by using the laminated body which laminated | stacked the said optically anisotropic layer A and the said optically anisotropic layer B (refer Unexamined-Japanese-Patent No. 2001-350022). The optically anisotropic layer B is effective for viewing angle optical compensation of liquid crystal molecules vertically aligned in VA mode, but the optically anisotropic layer A is also required for the improvement of the viewing angle of the polarizing plate described above. Therefore, when the laminated body of the said optically anisotropic layer A and the said optically anisotropic layer B is used as an optical compensation film, it is advantageous for the optical compensation of the viewing angle of the liquid crystal molecule perpendicularly aligned in VA dode, and the improvement of the polarizing plate viewing angle.

In addition, the liquid crystal display of the present invention may have an optical compensation film combining the above-described optically anisotropic layer A and the optically anisotropic layer B. Various aspects exist by the magnitude | size of (DELTA) nd of a liquid crystal layer, the laminated arrangement place, and the optical performance of the protective film of a polarizing plate.

For example, when the Re value ((nx-ny) × d ₁ ; d ₁ is the thickness (nm) of the protective film) of the protective film (3 or 12 in FIG. 1) of the polarizing plate is about 0 nm, the optically anisotropic layer A and It is preferable to arrange | position the optically anisotropic layer B as an optical compensation film, between a liquid crystal cell and a polarizing plate (in FIG. 1, between the board | substrate 8 and the protective film 12, or between the protective film 3 and the board | substrate 5). . At this time, it is preferable to arrange the optically anisotropic layer A closest to the light source because there is little leakage light.

And the Re value of the protective film (3 or 12 in FIG. 1) of the polarizing plate 0㎚, Rth value ({nx + ny) / 2 -nz} × d when the level ₁₎ are 50~200㎚, the protective film is optically anisotropic Since the optical compensation performance is the same as that of the layer B, only the optically anisotropic layer A is used as the optical compensation layer, and between the liquid crystal cell and the polarizing plate (in FIG. 1, between the substrate 8 and the protective film 12, or the protective film 3 and the substrate). (5) between). At this time, it is effective to arrange | position the optically anisotropic layer A below the liquid crystal cell from the light source, ie, the light source side. Moreover, in order to compensate for the lack of Rth of a protective film, you may arrange | position an optically anisotropic layer B separately.

When both the Re value and the Rth value of the protective film (3 or 12 in FIG. 1) of the polarizing plate are not 0 nm, the protective film exhibits optical compensating ability, so that the optical compensating effect can be obtained without separately forming the optical compensating layer. In order to give a function as an optical compensation layer to a transparent protective film, it is preferable that the Re value of at least one protective film is 5-50 nm, and Rth value is 50-300 nm. Moreover, even when a transparent protective film has optical compensating ability, you may arrange | position an optically anisotropic layer A and the optically anisotropic layer B separately in order to compensate for the shortfall of Re value and Rth value of a protective film.

In the aspect which mounted the optical compensation film which has an optically anisotropic layer separately, the transparent protective film arrange | positioned near the liquid crystal cell of a polarizing plate can serve as the support body of an optically anisotropic layer. Therefore, you may mount in a liquid crystal display device as an integrated polarizing plate laminated | stacked in the order of a transparent protective film, a polarizing film, a transparent protective film (using a transparent support body), and an optically anisotropic layer. Moreover, you may manufacture a liquid crystal display device, laminating sequentially. In a liquid crystal display device, it is preferable to laminate | stack from the outer side of the apparatus (side far from a liquid crystal cell) in order of a transparent protective film, a polarizing film, a transparent protective film (it also serves as the transparent support body of an optically anisotropic layer), and an optically anisotropic layer.

Next, a schematic schematic diagram of another embodiment of the liquid crystal display device of the present invention is shown in FIG. The liquid crystal display device of this embodiment is a structure in which the optical compensation layer 10 is additionally attached to the liquid crystal display device shown in FIG. In FIG. 2, the same number is attached | subjected about the same member as FIG. 1, and description is abbreviate | omitted. In addition, in FIG. 2, the protective film arrange | positioned at the outer side among the pair of protective films of the upper polarizing film 1 and the lower polarizing film 14 was abbreviate | omitted.

In the liquid crystal display device shown in FIG. 2, the optical characteristic of the protective film 12 satisfies the following relationship at an arbitrary wavelength? Of the visible light region.

−30 (nm) ≦ {(nx−ny) × d ₂ } ≦ 50 (nm), and

-50 (nm) ≤ [{(nx + ny) / 2-nz} × d ₂ ] ≤300 (nm)

The definition in formula is as above-mentioned. In addition, the liquid crystal display of FIG. 2 has an optical compensation layer 10 disposed adjacent to the protective film 12 in addition to the constituent members of the liquid crystal display of FIG. The optical compensation layer 10 is a film made of a compound having a discotic structural unit, and the discotic surface is almost perpendicularly oriented to the substrate surface. In addition, the orientation control direction of the optical compensation layer (for example, the rubbing axis when the orientation is controlled by the rubbed alignment film) and the slow axis 13 of the protective film 12 are disposed substantially parallel to the absorption axis of the polarizing film. do. In this embodiment, the retardation value of the layer (including the protective film of the polarizing film) through which the light passes from the polarizing film to the liquid crystal cell is made asymmetric, thereby improving the prevention of leakage light when viewed in the oblique direction. In particular, the present embodiment is effective for reducing oblique direction leakage light in an embodiment in which the absorption axes of the upper polarizing plate 1A and the lower polarizing plate 14A are perpendicular to each other.

The lower polarizing plate 14A is made of the polarizing film 14, the protective film 12, and the optical compensation layer 10 integrally formed. By setting it as such a structure, the protective film 12 can also serve as the support body of the optical compensation layer 10, and contributes to weight reduction and thinning of a liquid crystal display device. In addition, in this embodiment, the orientation control direction 11 of the optical compensation layer 10 and the slow axis 13 of the protective film 12 are substantially parallel to the absorption axis 15 of the polarizing film 14. Since it is arrange | positioned, it is advantageous at the point which an axis can be easily aligned when manufacturing an integrated polarizing plate.

Although there is no restriction | limiting in particular also about the drive mode of the liquid crystal cells 5-8 of this embodiment, It is preferable that it is a liquid crystal cell of an IPS mode.

The schematic side cross section of an IPS mode liquid crystal cell is shown in FIG. In the liquid crystal cell of the IPS mode, a plurality of pixels are usually provided by electrodes in a matrix, and a part of the one pixel is shown. A linear electrode 16 is formed inside the pair of transparent substrates 5 and 8, and an alignment control film (not shown) is formed thereon. The rod-like liquid crystalline molecules 7 sandwiched between the substrates 5 and 8 are oriented so as to have a slight angle with respect to the longitudinal direction of the linear electrode 16 when no electric field is applied. In addition, the dielectric anisotropy of the liquid crystal in this case assumes a quantity. When an electric field is applied, the liquid crystal component 7 changes its direction in the electric field direction.

The light transmittance can be changed by sandwiching the liquid crystal cell of the IPS mode and arranging the polarizing plates 1A and 14A at a predetermined angle. Moreover, the angle which the electric field direction with respect to the surface of the board | substrate 8 makes becomes like this. Preferably it is 20 degrees or less, More preferably, it is 10 degrees or less, ie, it is preferable that it is substantially parallel. Hereinafter, in this invention, the thing of 20 degrees or less is generically represented by a parallel electric field. In addition, even if the electrode 16 is divided into upper and lower substrates, and formed only in one board | substrate, the effect is the same.

As the liquid crystal material LC, a nematic liquid crystal having a positive dielectric anisotropy Δε is used. The thickness (gap) of the liquid crystal layer was made more than 2.8 micrometers and less than 4.5 micrometers. Thus, when the retardation value (DELTA) n * d is made into more than 0.25 micrometer and less than 0.32 micrometer, the transmittance | permeability characteristic which has little wavelength dependence within the range of visible light is obtained more easily. By the combination of the alignment film and the polarizing plate described later, the maximum transmittance can be obtained when the liquid crystal molecules are rotated 45 degrees from the rubbing direction to the electric field direction. In addition, the thickness (gap) of the liquid crystal layer is controlled by polymer beads. Of course, the same gap can also be obtained with glass beads, fibers, and columnar spacers made of resin. In addition, if liquid crystal material LC is a nematic liquid crystal, it will not specifically limit. The larger the dielectric anisotropy Δε can reduce the driving voltage, the smaller the refractive anisotropy Δn can increase the thickness (gap) of the liquid crystal layer, thereby shortening the sealing time of the liquid crystal and reducing the gap variation. can do.

The nematic liquid crystal material contained in the said liquid crystal layer may consist of two or more domain areas from which an orientation state differs.

As mentioned above, although the display mode of the liquid crystal display device of this embodiment is not specifically limited, ECB mode and IPS mode are used suitably. In this embodiment, it is preferable that the product (DELTA) n * d of the thickness d (micrometer) of a liquid crystal layer and refractive index anisotropy (DELTA) n shall be 0.2-1.2 micrometer. The optimum value of Δn · d is 0.2 to 0.5 μm. In these ranges, since the white display brightness is high and the black display brightness is small, a bright and high contrast display device is obtained. In addition, these optimum values are the values of the transmission mode, and since the optical path in the liquid crystal cell doubles in the reflection mode, the optimum? Nd value is about 1/2 of the above value. The liquid crystal display device used in the present embodiment is effective not only in the display mode but also in the VA mode, the OCB mode, the TN mode, the HAN mode, and the STN mode.

Hereinafter, the material used for the various members which can be used for the liquid crystal display device of this invention, its manufacturing method, etc. are demonstrated in detail.

[Polarizing Plate]

Generally, a polarizing plate consists of a polarizing film and a pair of protective film which clamps this polarizing film. As for the polarizing plate which concerns on this invention, the protective film formed in the surface arrange | positioned at least closer to a liquid crystal cell among a pair of protective films of a polarizing film shows the specific optical characteristic mentioned later. One embodiment of the polarizing plate of the present invention is a polarizing plate having optical compensation ability, to which an optical compensation layer (also referred to as an "optical anisotropic layer") formed of a liquid crystal compound is bonded. Moreover, the polarizing plate which has the optical compensation layer formed from the polymer film or liquid crystalline compound which has a predetermined optical characteristic as a protective film may also have optical compensation function, and the polarizing plate of such a structure can also be used. The optical compensation layer is preferably formed of liquid crystal molecules directly on the surface of the polarizing film or the protective film of the polarizing film or formed of liquid crystal molecules through the alignment film. Specifically, the optically anisotropic layer can be formed by applying the coating liquid for optically anisotropic layer to the surface of a polarizing film or the surface of the protective film of this polarizing film. In the former aspect, a thin polarizing plate with small stress (strain x cross-sectional area x elastic modulus) accompanying the dimensional change of the polarizing film can be produced without using a polymer film between the protective film of the polarizing film and the optically anisotropic layer. When the polarizing plate accompanying this invention is attached to a large sized liquid crystal display device, an image with high display quality is displayed, without causing problems, such as light leakage.

The polarizing film is Optiva Inc. The polarizing film which consists of a coating type polarizing film or a binder represented by this, and an iodine or a dichroic dye is preferable. The iodine and the dichroic dye in the polarizing film exhibit deviation performance by being oriented in a binder. The iodine and the dichroic dye are preferably oriented along the binder molecule or the dichroic dye is oriented in one direction by self-organization such as liquid crystal.

Currently, commercially available polarizers are generally produced by immersing a stretched polymer in a solution of iodine or dichroic dye in a bath and infiltrating iodine or dichroic dye in a binder in a binder.

A commercially available polarizing film has an iodine or a dichroic dye distributed at about 4 μm (both on both sides about 8 μm) from the polymer surface, and a thickness of at least 10 μm is required to obtain sufficient polarization performance. The penetration can be controlled by the solution concentration of iodine or dichroic dye, the temperature of the copper bath, and the immersion time.

As mentioned above, it is preferable that the minimum of binder thickness is 10 micrometers. The upper limit of the thickness is so thin that it is thin from the light leakage point of view of the liquid crystal display device. It is preferable that it is currently commercially available polarizing plate (about 30 micrometers) or less, 25 micrometers or less are preferable, and 20 micrometers or less are more preferable. If it is 20 micrometers or less, a light leakage phenomenon will not be observed by a 17-inch liquid crystal display device.

The binder of the polarizing film may be crosslinked.

The crosslinked binder can use a polymer which can be crosslinked per se. The binder obtained by introducing a functional group into the polymer or polymer having a functional group can be reacted between the binders by light, heat or pH change to form a polarizing film. Moreover, you may introduce a crosslinked structure into a polymer with a crosslinking agent. Crosslinking is generally performed by apply | coating the coating liquid containing a polymer or a mixture of a polymer and a crosslinking agent on a transparent support body, and then heating. Since durability can be ensured at the final product stage, the crosslinking treatment may be performed at any stage until the final polarizing plate is obtained.

As the binder of the polarizing film, any of polymers crosslinkable by themselves or polymers crosslinked by a crosslinking agent can be used. As an example of a polymer, the thing similar to the polymer which can be used for preparation of the orientation film mentioned later is mentioned. Most preferred are polyvinyl alcohol and modified polyvinyl alcohol. The modified polyvinyl alcohol is described in Japanese Patent Laid-Open Nos. 8-338913, 9-152509, and 9-316127. Polyvinyl alcohol and modified polyvinyl alcohol may use 2 or more types together.

As for the addition amount of a binder crosslinking agent, 0.1-20 mass% is preferable with respect to a binder. The orientation of a polarizing element and the moisture heat resistance of a polarizing film become favorable.

The polarizing film contains a crosslinking agent which has not reacted to some extent even after the crosslinking reaction is completed. However, it is preferable that it is 1.0 mass% or less in an alignment film, and, as for the quantity of the remaining crosslinking agent, it is more preferable that it is 0.5 mass% or less. By doing in this way, even if it attaches a polarizing film to a liquid crystal display device, and it leaves for a long term in the atmosphere of long-term use or high temperature, high humidity, it does not cause a fall of polarization degree.

Crosslinking agents are described in the specification of US Pat. No. 23297. Boron compounds (eg, boric acid, borax) can also be used as the crosslinking agent.

As the dichroic dye, an azo dye, a stilbene dye, a pyrazolone dye, a triphenylmethane dye, a quinoline dye, an oxadine dye, a thiazine dye or an anthraquinone dye is used. It is preferable that a dichroic dye is water-soluble. The dichroic dye preferably has a hydrophilic substituent (eg, sulfo, amino, hydroxyl). Examples of dichroic dyes include the compounds described in, for example, JP-A 2001-1745, page 58 (published March 15, 2001).

In order to raise the contrast ratio of a liquid crystal display device, it is preferable that the transmittance | permeability of a polarizing plate is high, and it is preferable that a polarization degree is also high. The transmittance of the polarizing plate is preferably in the range of 30 to 50% for light having a wavelength of 550 nm, more preferably in the range of 35 to 50%, and most preferably in the range of 40 to 50%. The degree of polarization is preferably in the range of 90 to 100%, more preferably in the range of 95 to 100%, and most preferably in the range of 99 to 100% for light having a wavelength of 550 nm.

The alignment film used for forming a polarizing film, an optical compensation layer, the protective film of an polarizing film, an optically anisotropic layer, or a polarizing film and an optically anisotropic layer may be adhere | attached through an adhesive agent. As the adhesive, polyvinyl alcohol-based resin (containing acetacetyl group, sulfonic acid group, carboxyl group, modified polyvinyl alcohol by oxyalkylene group) or boron compound aqueous solution can be used. Polyvinyl alcohol-type resin is preferable. It is preferable that the thickness of an adhesive bond layer exists in the range of 0.01-10 micrometers after drying, and it is especially preferable to exist in the range which is 0.05-5 micrometers.

[Production of Polarizing Plate]

The polarizing film is preferably dyed with iodine or a dichroic dye after stretching the binder at an angle of 10 to 80 degrees with respect to the longitudinal direction (MD direction) of the polarizing film in an inclined manner (stretching method) or rubbing (rubbing method). . The inclination angle is preferably stretched so as to match an angle formed by the transmission axis of the two polarizing plates bonded to both sides of the liquid crystal cell constituting the LCD and the vertical or horizontal direction of the liquid crystal cell. Typical inclination angle is 45 degrees. Recently, however, devices that are not necessarily 45 ° have been developed in transmissive, reflective and semi-transmissive LCDs, and it is desirable that the stretching direction can be arbitrarily adjusted according to the LCD design.

In the stretching method, the stretching ratio is preferably 2.5 to 30.0 times, more preferably 3.0 to 10.0 times. Stretching can be performed by dry stretching in air. In addition, you may perform wet drawing in the state immersed in water. The stretching ratio of dry stretching is preferably 2.5 to 5.0 times, and the stretching ratio of wet stretching is preferably 3.0 to 10.0 times. The stretching step may be divided into several times including diagonal stretching. By dividing into multiple times, it can extend | stretch more uniformly even by high magnification extending | stretching. Before the diagonal stretching, some stretching may be performed on the width or length (to prevent shrinkage in the width direction). Stretching can be performed by carrying out tenter stretching in biaxial stretching by a step of different left and right. The biaxial stretching is the same as the stretching method performed in normal film forming. In biaxial stretching, since the right and left are stretched at different speeds, it is necessary to make the thickness of the binder film before stretching different from right and left. In flexible film forming, a taper is formed in a die, and the difference of right and left can be made to flow volume of a binder solution.

As mentioned above, the binder film 10-80 degree diagonally stretched with respect to MD direction of a polarizing film is manufactured.

In the rubbing method, a rubbing treatment method widely adopted as a liquid crystal alignment treatment process of LCDs can be applied. That is, orientation is obtained by rubbing the surface of the film in a predetermined direction using paper, gauze, felt, rubber, nylon, or polyester fiber. Generally, it is performed by rubbing about several times using the cloth which averaged the fiber of uniform length and thickness.

It is preferable to implement using the rubbing roll whose roundness, cylinder degree, and shake (eccentricity) of a roll itself are all 30 micrometers or less. As for the wrap angle of the film with respect to a rubbing roll, 0.1-90 degrees is preferable. However, as described in JP-A-8-160430, it is also possible to obtain stable rubbing treatment by winding up to 360 ° or more.

When rubbing a long film, it is preferable to convey a film at a speed | rate of 1-100 m / min in the state of constant tension with a conveying apparatus. It is preferable that the rubbing roll is free to rotate in the horizontal direction with respect to the film traveling direction for setting an arbitrary rubbing angle. It is preferable to select an appropriate rubbing angle in the range of 0 to 60 degrees. When using for a liquid crystal display device, 40-50 degrees are preferable. 45 ° is particularly preferred.

On the surface opposite to the optically anisotropic layer of the polarizing film, it is preferable to arrange a polymer film for protecting the polarizing film (with an arrangement of the optically anisotropic layer / polarizing film / polymer film). The polymer film may have an antireflection film whose outer surface has antifouling property and scratch resistance.

[Shield]

The polarizing plate which concerns on this invention laminate | stacks a pair of protective film on both surfaces of a polarizing film. The kind of protective film is not specifically limited, Cellulose esters, such as a cellulose acetate, a cellulose acetate butyrate, and cellulose propionate, a polycarbonate, a polyolefin, polystyrene, polyester, etc. can be used.

It is preferable that a protective film is normally supplied in roll shape, and is continuously adhere | attached so that a longitudinal direction may correspond to a long polarizing film. Here, the orientation axis (ground axis) of the protective film may be in any direction, and in view of operational simplicity, the orientation axis of the protective film is preferably parallel to the longitudinal direction.

In the present invention, at least one of the pair of protective films sandwiching the polarizing film has a slow axis substantially coincident with the direction in which the average refractive index of the film surface is maximized. That is, at least one protective film has three average refractive indices nx, ny, and nz in the x, y, and z-axis directions orthogonal to each other, respectively, and when the in-plane average refractive index is nx and ny, and the thickness direction average refractive index is nz. , nx, ny = nz, nx> ny The film which a relationship is established; nx = ny, nz, nx> nz, and the like. The film which has optical characteristics as said optically anisotropic layer A, optically anisotropic layer B, etc. is mentioned. As described above, in order to impart optical compensation capability to the protective film, -5 nm≤ {(nx-ny) xd ₁ } ≤50 (nm) and 50 nm≤ [{ It is preferable to satisfy (nx + ny) / 2-nz} × 2] ≦ 300 nm.

On the other hand, in the aspect which does not function as an optical compensation layer in a protective film, it is preferable that the retardation of a transparent protective film is low, and especially in the aspect which the absorption axis of a polarizing film and the orientation axis of a transparent protective film are not parallel, especially the retardation value of a transparent protective film is constant. If it is more than a value, since the polarization axis and the orientation axis (ground axis) of a transparent protective ink are shift | deviated obliquely, linearly polarized light changes to elliptical polarization, and it is unpreferable. Therefore, as for the retardation of a transparent protective film, 10 nm or less is preferable at 632.8 nm, for example, and 5 nm or less is more preferable. As the low retardation polymer film, polyolefins such as cellulose triacetate, zeonex, and zeona (all manufactured by Nippon Zeon Co., Ltd., ARTON (manufactured by JSR Co., Ltd.) are preferably used. The non-birefringent optical resin material as described in Unexamined-Japanese-Patent No. 8-110402 or Unexamined-Japanese-Patent No. 11-293116 is mentioned.

When adhering the protective film and the polarizing film, the slow axis (orientation axis) of at least one protective film (protective film disposed on the side close to the liquid crystal cell when mounted on the liquid crystal display device) and the absorption axis (extension axis) of the polarizing film intersect. A protective film and a polarizing film are laminated. Specifically, the angle between the absorption axis of the polarizing film and the slow axis of the protective film is preferably 10 ° to 90 °, more preferably 20 ° to 70 °, still more preferably 40 ° to 50 °, particularly preferably 43 to 47 °. The angle between the slow axis of the other protective film and the absorption axis of the polarizing film is not particularly limited and can be appropriately set according to the purpose of the polarizing plate, but it is preferable that the above-mentioned range is preferred, and that the slow axis of the pair of protective films coincides. . Moreover, when the slow axis of a protective film and the absorption axis of a polarizing film are mutually parallel, the mechanical stability of a polarizing plate, such as a dimensional change of a polarizing plate and prevention of a curl, can be improved. The same effect can be obtained when at least two axes of a total of three films which are a polarizing film and a pair of protective films, the slow axis of one protective film, the polarizing film absorption axis, or the slow axis of two protective films are substantially parallel.

In addition, when the retardation value of the protective film of the up-and-down polarizing plate is made asymmetric, it contributes greatly to the prevention of the leakage light in the case seen from the diagonal direction. When the retardation value of the protective film arrange | positioned between the liquid crystal cell of a vertically polarizing plate and a polarizing film is made especially asymmetric, it is effective for the reduction of the inclination light leakage in the aspect which the absorption axis of a vertically polarizing plate orthogonally crosses. In order to make a retardation asymmetric, {(nx-ny) × d ₁ } or {(nx + ny) / 2-nz} is applied to at least one of one pair of protective films of an upper polarizing plate and at least one of a pair of protective films of a lower polarizing plate. Each having a different value of xd ₁ is used. On the other hand, when the retardation of the pair of protective films of the same structure that the polarizing plates of the same structure are arrange | positioned to the upper and lower polarizing plates of a liquid crystal cell is the same, optical compensation of a liquid crystal cell by these protective films or by the optical compensation film attached separately is carried out. can do.

<Adhesive>

Although the adhesive agent of a polarizing film and a protective film is not specifically limited, PVA system resin (containing modified PVA, such as an acetacetyl group, a sulfonic acid group, a carboxyl group, and an oxyalkylene group), the boron compound aqueous solution, etc. are mentioned, Among these, PVA system is mentioned. Resin is preferable. 0.01-10 micrometers is preferable and, as for an adhesive bond layer thickness, 0.05-5 micrometers is especially preferable.

<Integrated manufacturing process of polarizing film and transparent protective film>

Although the polarizing plate which concerns on this invention has a drying process which shrink | contracts and reduces a volatile fraction after extending | stretching the film for polarizing films, It is preferable to have a post-heating process after adhering a transparent protective film to at least one side after drying or during drying. Do. In an aspect in which the transparent protective film also serves as a support for an optically anisotropic layer functioning as an optical compensation layer, it is preferable to apply post-heating after attaching a transparent protective film having a transparent protective film on one side and an optically anisotropic layer on the opposite side. As a specific bonding method, during the drying process of the film, a transparent protective film is adhered to the polarizing film using an adhesive in a state where both ends are supported, and then the edges of both ends are cut or dried, and then the film for polarizing film is released from the supporting parts of both ends. After cutting the edges of both ends of the film, there is a method such as bonding a transparent protective film. As a method of cutting the edges, general techniques such as cutting with a cutter such as a blade and a method using a laser can be used. After adhesion, it is preferable to heat the adhesive in order to dry it and to improve the polarization performance. Although it changes with an adhesive agent as heating conditions, 30 degreeC or more is preferable in a water system, More preferably, they are 40 degreeC or more and 100 degrees C or less, More preferably, they are 50 degreeC or more and 90 degrees C or less. It is most desirable for these processes to be manufactured in a consistent line for performance and production efficiency.

<Performance of Polarizing Plate>

The optical properties and durability (short-term, long-term storage property) of the polarizing plate which consists of a transparent protective film, a polarizer, and a transparent support body which concern on this invention are equivalent to or more commercially available super high contrast products (for example, HLC2-5618 by Sanritsu Co., Ltd.). It is desirable to have performance. Specifically, visible light transmittance is 42.5% or more, and polarization degree {(Tp-Tc) / (Tp + Tc)} ^1/2 ≥0.9995 (where Tp is parallel transmittance and Tc is orthogonal transmittance), and 60 ° C and humidity. The change rate of light transmittance before and after 500 hours in 90% RH atmosphere and 500 hours in a dry atmosphere for 500 hours in 90% RH atmosphere is 3% or less based on absolute value, Furthermore, 1% or less, and the change rate of polarization degree is absolute value It is preferable that it is 1% or less and further 0.1% or less based on.

The polarizing plate used for this invention may have an optical compensation layer as mentioned above. The optical compensation layer is made of a compound having a discotic structural unit, and it is preferable that the discotic surface is an optical compensation layer oriented almost perpendicular to the reference plane. The detail and the preferable range of the material and the manufacturing method of the said optical compensation layer are the same as the optically anisotropic layer which is one component layer of the optical compensation film demonstrated below.

[Optical Compensation Film]

The optical compensation film is used in the liquid crystal display device to reduce image coloring and to enlarge a viewing angle. In the present invention, as described above, the optical compensation film is not an essential member. For example, the optical compensation film may not be necessary in an aspect in which birefringence is added to one or both of the pair of protective films of the polarizing plate to function as the optical compensation film.

It is preferable that in-plane retardation Re of the whole optical compensation film is 20-200 nm. It is preferable that the retardation (Rth) of the thickness direction of the whole optical compensation film is 50-500 nm. In-plane retardation Re and retardation Rth of thickness direction of an optical compensation film represent in-plane retardation and retardation of thickness direction, respectively. Re is measured by injecting light having a wavelength of λ nm in the direction of the film normal in KOBRA 21ADH (manufactured by Oshi Measuring Instruments Co., Ltd.). Rth is a retardation value measured by injecting light having a wavelength of λ nm from a direction inclined at + 40 ° to the film normal direction using the Re, the in-plane slow axis (determined by KOBRA 21ADH) as the inclination axis (rotation axis). , And the in-plane slow axis as the inclination axis (rotation axis) based on retardation values measured in a total of three directions of retardation values measured by incident light having a wavelength of λ nm from a direction inclined at -40 ° to the film normal direction. KOBRA 21ADH is calculated. Here, the assumption of the average refractive index may be used as a polymer handbook (JOHN WILEY & SONS, INC) and catalog values of various optical films. If the value of the average refractive index is not already known, it can be measured with an Abbe refractometer. The average refractive index value of a main optical film is illustrated below; Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethylmethacrylate (1.49), polystyrene (1.59). KOBRA 21ADH calculates nx, ny, and nz by inputting the assumption value and film thickness of these average refractive indices.

[Optical Anisotropic Layer Made of Liquid Crystalline Compound]

Since there exist various orientation forms in a liquid crystalline compound, the optically anisotropic layer which consists of a liquid crystalline compound expresses desired optical property by a single layer or a laminated body of multiple layers. That is, the optical compensation film may be a sun made of a support and at least one optically anisotropic layer formed on the support. The retardation of the whole optical compensation film of such an aspect can be adjusted with the optical anisotropy of an optically anisotropic layer. A liquid crystal compound can be classified into a rod-like liquid crystal compound and a disk compound from the shape thereof. In addition, there are low molecular and polymer types, respectively, and both can be used. It is preferable to use a rod-like liquid crystalline compound or a disk-shaped compound as a liquid crystalline compound, and, as for the optically anisotropic layer which consists of liquid crystalline compounds used for this invention, it is more preferable to use the rod-shaped liquid crystalline compound which has a polymeric group, or the disk shaped compound which has a polymeric group. desirable.

(Bar-shaped liquid crystalline compound)

Examples of rod-like liquid crystalline molecules include azomethines, azoxy compounds, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, and cyano-substituted phenylpyrimidines. , Alkoxy substituted phenylpyrimidines, phenyldioxanes, transs and alkenylcyclohexylbenzonitriles are preferably used.

In addition, the rod-like liquid crystalline molecule also includes a metal complex. Moreover, the liquid crystal polymer which contains a rod liquid crystal molecule in a repeating unit can also be used as a rod liquid crystal molecule. That is, the rod-like liquid crystalline molecules may be combined with the (liquid crystal) polymer.

Regarding rod-shaped liquid crystalline molecules, Chapter 4, Chapter 7 and Chapter 11 of the Japanese Chemical Society (1994) Japanese Chemical Society, and the Liquid Crystal Devices Handbook Japanese Society for the Advancement of Chapter 142 Committee Chapter 3 It is described.

The birefringence of the rod-like liquid crystalline molecules is preferably in the range of 0.001 to 0.7. It is preferable that rod-shaped liquid crystalline molecules have a polymeric group in order to fix the orientation state. The polymerizable group is preferably a radical polymerizable unsaturated group or a cation polymerizable group, and specifically, for example, the polymerizable group and polymerizable liquid crystal compound described in paragraphs [0064] to [0086] of JP-A-2002-62427. Can be mentioned.

(Discrete compound)

It is preferable to use a disk type compound as a liquid crystalline compound which forms the said optically anisotropic layer. The discoid compound is preferably oriented substantially perpendicular (average tilt angle in the range of 50 to 90 degrees) with respect to the polymer film plane. Discoid compounds are described in various publications (C. Destrade et al., Mol. Crysr, Liq. Cryst., Vol. 71, page 111 (1981); Japanese Chemical Sculpture, Quarterly Chemistry Collection, No. 22, Chemistry of Liquid Crystals, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794 (1985); J. Zhang et al., J. Am. Chem. Soc., Vol. 116, page 2655 (1994). The polymerization of the discotic compound is described in JP-A-8-27284.

It is preferable that a disk shaped compound has a polymeric group so that fixation may be carried out by superposition | polymerization. For example, a structure in which a polymerizable group is bonded as a substituent to a disc shaped core of a disc shaped compound can be considered. However, if the polymerizable group is directly connected to the disc shaped core, it becomes difficult to maintain an orientation state in the polymerization reaction. Therefore, a structure having a linking group between the discotic core and the polymerizable group is preferable. That is, it is preferable that the disk shaped compound which has a polymeric group is a compound represented by following formula (III).

Formula (III) D (-LP) _n

In formula, D is a disc shaped core, L is a bivalent coupling group, P is a polymeric group, n is an integer of 4-12.

Preferable specific examples of the disk-shaped core (D), the divalent linking group (L) and the polymerizable group (P) in the formula (III) include (D1) to (D15), ( L1) to (L25), (P1) to (P18), and the contents described in the publication can be preferably used.

(Orientation of the Liquid Crystalline Compound)

It is preferable that these liquid crystalline compounds are aligned substantially uniformly in an optically anisotropic layer, It is more preferable to fix in the state which is substantially uniformly aligned, The liquid crystalline compound is fixed by a polymerization reaction. Most preferred. In the case of the rod-shaped liquid crystalline compound having a polymerizable group, it is preferable to fix in a substantially horizontal (homogenous) orientation. Substantially horizontal means that the average density (average inclination angle) of the major axis direction of an rod-shaped liquid crystalline compound and the surface of an optically anisotropic layer is in the range of 0 to 40 degrees. The rod-like liquid crystal compound may be aligned, or the tilt angle may be gradually changed (hybrid alignment). Also in the case of inclination orientation or hybrid orientation, it is preferable that average inclination angle is 0 degrees-40 degrees. The optically anisotropic layer formed of the rod-like liquid crystal compound fixed to such an orientation may be attached to the liquid crystal display device of VA mode and IPS mode, and can contribute as an optically anisotropic layer which contributes to the improvement of the viewing angle characteristic of a liquid crystal display device.

In the case of a disk-shaped compound having a polymerizable group, it is preferable to make it orientate substantially vertically. Substantially perpendicular means that the average angle (average inclination angle) between the disk surface of a disk-shaped compound and the surface of an optically anisotropic layer is in the range of 50 ° to 90 °. The disk-shaped compound may be inclined or may be inclined so as to gradually change (hybrid orientation). Also in the case of inclination orientation or hybrid orientation, it is preferable that an average inclination angle is 50 degrees-90 degrees. The optically anisotropic layer formed of the disk-shaped compound fixed to such an orientation may be attached to the liquid crystal display device of VA mode and IPS mode, and may serve as an optically anisotropic layer which contributes to the improvement of the viewing angle characteristic of a liquid crystal display device.

It is preferable to form an optically anisotropic layer by apply | coating the coating liquid containing a liquid crystalline compound, the following polymerization initiator, and another additive on an alignment film. As a solvent used for preparation of a coating liquid, an organic solvent is used preferably. Examples of organic solvents include amides (eg N, N-dimethylformamide), sulfoxides (eg dimethyl sulfoxide), heterocyclic compounds (eg pyridine), hydrocarbons (eg benzene, hexane), alkyl halides (eg , Chloroform, dichloromethane), esters (eg ethyl acetate, butyl acetate), ketones (eg acetone, methyl ethyl ketone), ethers (eg tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. You may use together 2 or more types of organic solvents. Application | coating of a coating liquid can be performed by a well-known method (for example, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).

(Fixation of Orientation State of Liquid Crystalline Compound)

It is preferable to maintain the orientation state and to fix the oriented liquid crystalline compound. It is preferable to perform fixation by the polymerization reaction of the polymeric group introduce | transduced into a liquid crystalline compound. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator, but a photopolymerization reaction is more preferable. Examples of photopolymerization initiators include α-carbonyl compounds (US Pat. No. 2367661, US Pat. No. 2367670), acyloinether (US Pat. No. 2448828), α-hydrocarbon substituted aromatic acyloin compounds (US Pat. No. 2722512) ), Polynuclear quinone compounds (see US Pat. No. 3046127, US Pat. No. 2951758), combinations of triarylimidazole dimers with p-aminophenylketone (described in US Pat. No. 3549367), acridine and Phenazine compounds (JP-A-60-105667, described in US Pat. No. 4239850) and oxadiazole compounds (described in US Pat. No. 4212970).

It is preferable that it is 0.01-20 mass% of coating liquid solid content, and, as for the usage amount of a photoinitiator, it is more preferable that it is 0.5-5 mass%. It is preferable to use ultraviolet-ray for the light irradiation for superposition | polymerization of a liquid crystalline compound. It is preferable that it is 20mJ / cm <2> -50mJ / cm <2>, and it is more preferable that it is 100-800mJ / cm <2>. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. It is preferable that it is 0.1-10 micrometers, and, as for the thickness of an optically anisotropic layer, it is more preferable that it is 0.5-5 micrometers.

(Alignment film)

In order to orientate a liquid crystalline compound at the time of formation of an optically anisotropic layer, it is preferable to use an oriented film. The alignment film is an organic compound (e.g., ω-tricoic acid, di, by rubbing treatment of an organic compound (preferably a polymer), evaporation of an inorganic compound, formation of a layer having micro groups, or by a Langmuir brozet method (LB film)). Octadecyldimethylammonium chloride, methyl stearate, or the like). Moreover, the orientation film which an orientation function produces by provision of an electric field, provision of a magnetic field, or light irradiation is also known. The alignment film formed by the rubbing process of a polymer is especially preferable. The rubbing treatment is performed by rubbing the surface of the polymer layer with paper or cloth a plurality of times in a predetermined direction. The kind of polymer used for an oriented film can be determined according to the orientation (especially average inclination angle) of a liquid crystalline compound. For example, in order to orientate a liquid crystalline compound horizontally, the polymer (normally a polymer for orientation) which does not reduce the surface energy of an oriented film is used. Specific types of polymers are described in various literatures on liquid crystal cells or optical compensation films. It is preferable to have a polymeric group also in any orientation film in order to improve the adhesiveness of a liquid crystalline compound and a transparent support body. A polymerizable group can introduce the repeating unit which has a polymeric group in a side chain, or can introduce it as a substituent of a cyclic group. It is more preferable to use the alignment film which forms a chemical bond with a liquid crystalline compound at an interface, and it is described in Unexamined-Japanese-Patent No. 9-152509 as such an alignment film. It is preferable that it is 0.01-5 micrometers, and, as for the thickness of an oriented film, it is more preferable that it is 0.05-1 micrometer.

Moreover, after orienting a liquid crystalline compound using an oriented film, you may fix an optically anisotropic layer by fixing a liquid crystalline compound as it is, and only an optically anisotropic layer may be transferred on a polymer film (or a transparent support body).

[Vertical Alignment Film]

In order to orientate the liquid crystal compound vertically on the alignment film side, it is important to lower the surface energy of the alignment film. Specifically, the surface energy of the alignment film is lowered by the functional group of the polymer, whereby the liquid crystal compound is made upright. As a functional group which reduces the surface energy of an oriented film, a fluorine atom and a hydrocarbon group with 10 or more carbon atoms are effective. In order to make a fluorine atom or a hydrocarbon group exist in the surface of an oriented film, it is preferable to introduce a fluorine atom or a hydrocarbon group into a side chain rather than a main chain of a polymer. The fluorine-containing polymer preferably contains fluorine atoms in a proportion of 0.05 to 80% by weight, more preferably in a proportion of 0.1 to 70% by weight, and even more preferably in a proportion of 0.5 to 65% by weight. It is most preferable to contain it in the ratio of 1 to 60 weight%. The hydrocarbon group is an aliphatic group, an aromatic group or a combination thereof. The aliphatic group may be any of cyclic, branched or straight chain. The aliphatic group is preferably an alkyl group (which may be a cycloalkyl group) or an alkenyl group (which may be a cycloalkenyl group). The hydrocarbon group may have a substituent which does not exhibit strong hydrophilicity such as a halogen atom. The number of carbon atoms in the hydrocarbon group is preferably 10 to 100, more preferably 10 to 60, and most preferably 10 to 40. The main chain of the polymer preferably has a polyimide structure or a polyvinyl alcohol structure.

Polyimides are generally synthesized by the condensation reaction of tetracarboxylic acid and diamine. You may synthesize | combine the polyimide corresponded to a copolymer using two or more types of tetracarboxylic acid or two or more types of diamine. The fluorine atom or the hydrocarbon group may be present in a repeating unit of tetracarboxylic acid origin, in a repeating unit of diamine origin, or in both repeating units. When introducing a hydrocarbon group into a polyimide, it is particularly preferable to form a steroid structure in the main chain or the side chain of the polyimide. The steroid structure present in the side chain corresponds to a hydrocarbon group having 10 or more carbon atoms, and has a function of vertically aligning the liquid crystalline compound. In the present specification, the steroid structure means a ring structure in which a cyclopentanohydrophenanthrene ring structure or a part of a bond of the ring is a double bond in the range of an aliphatic ring (a range not forming an aromatic ring).

Moreover, as a means of orienting a liquid crystalline compound vertically, the method of mixing an organic acid with the polymer of polyvinyl alcohol or a polyimide can be used preferably. As the acid to be mixed, carboxylic acid, sulfonic acid and amino acid are suitably used. You may use what shows acidity among the air interface aligning agents mentioned later. It is preferable that the mixing amount is 0.1 to 20 weight% with respect to a polymer, and it is more preferable that it is 0.5 to 10 weight%.

For the uniform alignment of the discotic liquid crystal compound, the vertical alignment film is rubbed to control the alignment direction. The rubbing treatment is performed by rubbing the surface of the polymer layer with paper or cloth a plurality of times in a predetermined direction. On the other hand, it is preferable not to perform a rubbing process in the orientation of a rod-shaped liquid crystalline compound. It is preferable to have a polymeric group in an orientation film in order to improve the adhesiveness of a liquid crystal compound and a transparent support body in any orientation film. A polymerizable group can introduce the repeating unit which has a polymeric group in a side chain, or can introduce as a substituent of a cyclic group. It is more preferable to use the alignment film which forms a chemical bond with a liquid crystalline compound at an interface, and it is described in Unexamined-Japanese-Patent No. 9-152509 as such an alignment film. It is preferable that it is 0.01-5 micrometers, and, as for the alignment film thickness, it is more preferable that it is 0.05-1 micrometer. Moreover, after orienting a liquid crystalline compound using an oriented film, you may fix a liquid crystalline compound as it is in the orientation state, and form a phase difference layer, and only a phase difference layer may be transferred on a polymer film (or a transparent support body).

[Air Interface Alignment Agent]

Since an ordinary liquid crystalline compound has the property of being inclinedly oriented on the air interface side, it is necessary to vertically control the liquid crystalline compound on the air interface side in order to obtain a uniformly vertically aligned state. For this purpose, a compound which is ubiquitous on the air interface side and acts to vertically orient the liquid crystal compound by the exclusion volume effect or the electrostatic effect is blended into the liquid crystal coating liquid. In the discotic liquid crystalline compound, the action of vertically aligning the liquid crystalline compound corresponds to the action of reducing the inclination angle of the director, that is, the angle between the director and the coated liquid crystal air side surface. As a compound which reduces the inclination angle of the director of a discotic liquid crystalline molecule, what couple | bonded two or more F atoms in order to unevenly distribute to the air interface side shown next, or couple | bonded with a sulfonyl group and a carboxyl group, it is perpendicular to a liquid crystalline molecule further Compounds that combine rigid structural units that impart an excluding exclusion volume effect are preferably used.

In addition to the exemplified compounds, the compounds described in Japanese Unexamined Patent Publication Nos. 2002-20363 and 2002-129162 can be used as the air interfacial alignment agent. Further, Paragraph Nos. 0072 to 0075 of Japanese Patent Application No. 2002-212100, Paragraph Nos. 0038 to 0040 and 0048 to 0049, and Paragraph Nos. 0037 to 0039 and 2002-2002 of the specification of 2002-243600. The matters described in paragraphs 0071 to 0078 of the specification 91752 can also be appropriately applied to the present invention.

It is preferable that the usage-amount of the air interface aligning agent with respect to a liquid crystal coating liquid is 0.05 weight%-5 weight%. Moreover, when using a fluorine-saturated air interface aligning agent, it is preferable that it is 1 weight% or less.

The support for supporting the optically anisotropic layer is not particularly limited, and various polymer films and the like can be used. Triacetyl cellulose, norbornene resin etc. are mentioned, for example. In addition, as above-mentioned, the protective film of a polarizing plate may serve as the support body of an optically anisotropic layer. The specific example of the support material in this aspect is the same as that of the specific example of the protective film material of a polarizing plate, and is as above-mentioned.

Example

An Example is given to the following and this invention is demonstrated to it further more concretely. Materials, reagents, amounts of substances, proportions thereof, operations and the like shown in the following examples can be appropriately changed as long as they do not depart from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following embodiments.

[Example 1]

The liquid crystal display device of the structure shown in FIG. 1 was produced. That is, from the viewing direction (upper) to the upper polarizing plate (protective film 3a, polarizing film 1, protective film 3), liquid crystal cell (upper substrate 5, liquid crystal layer 7, lower substrate 8), The lower polarizing plate (protective film 12, polarizing film 14, protective film 12a) was laminated, and the backlight light source (not shown) was further arrange | positioned.

The manufacturing method of each member used below is demonstrated.

<Production of liquid crystal cell>

The liquid crystal cell was prepared by dropping and filling a liquid crystal material having a negative dielectric anisotropy ("MLC6680", manufactured by Merck Co., Ltd.) between the substrates with a cell gap of 3 µm between substrates, and forming a liquid crystal layer between the substrates. . The retardation of the liquid crystal layer (that is, the product Δn · d of the thickness d (µm) of the liquid crystal layer and the refractive index anisotropy Δn) was 300 nm. In addition, the liquid crystal material was oriented so as to be vertically aligned.

<Production of up and down polarizing plate>

(Production of Polarizing Film)

After washing the PVA film with an average degree of polymerization of 2400 and a film thickness of 100 μm for 60 seconds with 15 to 17 ° C. of ion-exchanged water and removing surface moisture with a blade made of stainless steel, the concentration of the PVA film was adjusted so that the concentration was constant. It was immersed at 40 ° C. for 55 seconds in an aqueous solution of 0.77 g / l iodine and 60.0 g / l potassium iodide. Concentration correction was carried out so that the concentration was constant again, soaked in an aqueous solution of 42.5 g / L boric acid and 30 g / L potassium iodide at 40 ° C. for 90 seconds, after which excess water on both sides of the film was removed with a stainless steel blade and contained in the film. It introduce | transduced into the tenter drawing machine in the state which made distribution of moisture content 2% or less.

After conveying at a rate of 4 m / min, 100 m, and stretching up to 5 times in a 60 ° C. 95% atmosphere, the tenter was bent in the stretching direction, and then the width was kept constant and dried in a 70 ° C. atmosphere while shrinking. After leaving the tenter. The water content of the PVA film before the start of stretching was 32%, and the water content after drying was 1.5%. The conveyance speed difference of the left and right tenter clips was less than 0.05%, and the angle which the centerline of the film introduce | transduced and the centerline of the film sent to the difference process made was 46 degrees. L1-L2 was 0.7m, W was 0.7m, and L1-L2 was in a relationship of W. The actual stretching direction Ax-Cx at the tenter exit was inclined 45 ° with respect to the centerline 22 of the film sent to the next step. No wrinkles or film deformation at the tenter exit were observed. In addition, the film thickness after extending | stretching and drying was 18 micrometers.

(Adhesion of transparent protective film)

About the polarizing film produced by the said diagonal drawing method, about 3 cm from the width direction was cut off the edge using a cutter, and both sides were PVA (PVA-117H by Kuraray Co., Ltd.) 3% aqueous solution with an adhesive agent. The cellulose triacetate film (Re value = 30 nm, Rth = 130 nm) for the transparent protective film which saponified the surface was bonded, and it heats again at 70 degreeC for 10 minutes, and the cellulose triacetate protective film on both surfaces of effective width 650 mm. The elongate polarizing plate provided with this was obtained. In addition, this film had a slow axis substantially coinciding with the direction in which the average refractive index of the membrane surface was maximized. At the time of adhesion of the upper polarizing plate, the axial angles of the slow axis of the upper protective film, the absorption axis of the polarizing film, and the slow axis of the lower protective film are set to (0 °, 45 °, 0 °) with reference to the display device horizontal direction. The axial angle of the lower polarizing plate was set to (0 °, -45 °, 0 °). Since the absorption axis direction of the polarizing film produced above was inclined at 45 ° to the longitudinal direction, it was cut to a size of 310 × 233 mm to obtain a polarizing plate having an area efficiency of 91.5% and an absorption axis of 45 ° with respect to the side. there was. Also, no visible discoloration was seen with the naked eye.

The polarizing plate performance of the obtained polarizing plate has a visible light transmittance of 43.5, and the degree of polarization

{(Tp-Tc) / (Tp + Tc)} ^1/2 ≥0.9997

(Where Tp is parallel transmittance and Tc is orthogonal transmittance), and the change in light transmittance before and after 500 hours in a temperature of 60 ° C. and a humidity of 90% RH and 500 ° C. for 500 hours in a dry atmosphere is an absolute value. Based on 1% or less, the rate of change in polarization degree was 0.05% or less based on the absolute value.

<Measurement of leakage light of manufactured liquid crystal display device>

The leakage light of the liquid crystal display device produced in this way was measured. The leakage light when observed from the left side at 60 ° was 0.7%. In the field of view characteristic of a liquid crystal display device, it is preferable that the viewing angle of a contrast ratio of 5: 1 or more is 80 degrees or more in right, left, up and down. In the fabricated liquid crystal display device, since the white display has a transmittance of about 30%, when the leakage light of the black display satisfies less than 1% at the viewing angle of 60 °, the contrast ratio of 5 to 1 or more viewing angles is determined from above and below. It can be estimated that 80 degrees or more are obtained.

[Example 2]

<Production of Liquid Crystal Display Device>

In the liquid crystal display device produced in Example 1, the liquid crystal display in the same manner as in Example 1 except for using a norbornene-based film showing various Re values and Rth values as shown in Table 1 at the time of preparation of the vertical polarizing plate. Devices No. 1 to 24 were produced. In addition, all of these used norbornene-type films had the slow axis substantially coinciding with the direction in which the average refractive index of a film surface becomes the maximum.

<Measurement of leakage light of liquid crystal display device>

The value of the leakage light at the time of observation at 60 degrees of inclination of produced liquid crystal display devices No.1-24 was measured, respectively. The results are shown in Table 1.

Table 1: Black display transmittance at viewing angle of 60 ° left and right

Example 3

Next, the Example using the polarizing plate which has an optical compensation layer which has optical compensation capability is demonstrated.

<Production of Optical Compensation Film>

(Preparation of transparent protective film for polarizing film and transparent support for optical compensation layer)

The following composition was put into a mixing tank, stirred while heating, and each component was dissolved to prepare a cellulose acetate solution.

Cellulose Acetate Solution Composition

100 parts by mass of cellulose acetate having acetonitrile degree of 60.7 to 61.1%

Triphenyl phosphate (plasticizer) 7.8 parts by mass

Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by mass

Methylene chloride (first solvent) 336 parts by mass

29 parts by mass of methanol (second solvent)

16 mass parts of retardation increasing agents, 92 mass parts of methylene chloride, and 8 mass parts of methanol were put into the other mixing tank, and it stirred while heating, and prepared the retardation increasing agent solution. 25 mass parts of retardation synergist solutions were mixed with 474 mass parts of cellulose acetate solutions, and it fully stirred, and dope was prepared. The addition amount of the retardation increasing agent was 3.5 mass parts with respect to 100 mass parts of cellulose acetate.

Retardation synergist

The obtained dope was cast using a band drawing machine. After the film surface temperature on a band became 40 degreeC, it dried for 1 minute by 70 degreeC warm air from the band, and dried the film by 140 degreeC dry air for 20 minutes from a band, and the cellulose acetate film whose residual amount of solvent is 0.3 mass% (thickness: 146 micrometers) was produced. About the produced cellulose acetate film (transparent support body, transparent protective film), Re-retardation value and Rth retardation value in wavelength 550nm are measured using an ellipsometer (M-150, Nippon Spectroscopy). It was. Re was 2 nm (deviation ± 1 nm) and Rth was 190 nm (deviation ± 3 nm). In addition, Re of each wavelength of 400 nm-700 nm was 2 +/- 1 nm, and Rth of each wavelength of 400 nm-700 nm was 190 +/- 2 nm range.

The produced cellulose acetate film was immersed in 2.0 N potassium hydroxide solution (25 ° C) for 2 minutes, neutralized with sulfuric acid, washed with pure water, and dried. It was 63 mN / m when the surface energy of this cellulose acetate film was calculated | required by the contact method. In this way, the cellulose acetate film for a transparent support body and a transparent protective film was produced. The obtained film had a slow axis substantially coinciding with the direction in which the average refractive index of the membrane surface was maximized.

(Production of the alignment film layer)

On this cellulose acetate film, the coating liquid of the following composition was apply | coated 28 ml / m <2> with the wire bar coater of # 16. It dried for 60 second at 25 degreeC, 60 second by 60 degreeC warm air, and 150 second by 90 degreeC warm air again. The alignment film thickness after drying was 1.1 micrometers. The surface roughness of the alignment film was measured by an atomic force microscope (AFM: Atomic Force Microscope, SPI3800N, manufactured by Seiko Instruments Co., Ltd.), and the result was 1.147 nm. Next, the formed film was subjected to a rubbing treatment in the -45 ° direction with respect to the slow axis (measured at a wavelength of 632.8 nm) of the cellulose acetate film.

Alignment film coating liquid composition

20 parts by mass of the following modified polyvinyl alcohol

361 parts by mass of water

119 parts by mass of methanol

Glutalaldehyde (crosslinking agent) 0.5 parts by mass

Modified polyvinyl alcohol

(Production of optically anisotropic layer)

On the alignment film, the coating liquid of the following composition was continuously applied, dried, and heated (oriented aging) using a bar coater, and irradiated with ultraviolet rays again to form a horizontally oriented optically anisotropic layer (A) having a thickness of 1.1 μm, An optical compensation film was produced. The optically anisotropic layer had a slow axis in the -45 ° direction with respect to the longitudinal direction of the transparent support. Re value at 550 nm was 130 nm.

Coating liquid composition for optically anisotropic layer (A)

38.1 mass% of the following rod-like liquid crystalline compounds I-2

The following sensitizer A 0.38 mass%

1.14 mass% of following photoinitiators B

Orientation control agent C 0.19 mass%

Glutalaldehyde 0.04 mass%

Methyl ethyl ketone 60.1 mass%

The optical compensation film which consists of the produced optically anisotropic layer and the transparent support body is made into the transparent support body which consists of a cellulose acetate film between the lower polarizing film 14 and the lower substrate 8 for liquid crystal cells (Re = 2nm, Rth =) in FIG. 190 nm) was attached in contact with the polarizing film 14. That is, the transparent protective film 12 produced the liquid crystal display device of the aspect which also serves as the transparent support body of the optically anisotropic layer which has optical compensation ability. The rest of the configuration was the same as in Example 1. That is, the axial angles of the slow axis of the upper protective film, the absorption axis of the polarizing film, and the slow axis of the lower protective film of the upper polarizing plate are set to (0 °, 45 °, 0 °) with reference to the display device horizontal direction, and the lower polarizing plate is similarly The axial angle of was set to (0 °, -45 °, 0 °), and the slow axis (rubbing direction) of the optically anisotropic layer was again -45 °.

In the production of the optical compensation film, the Re value and the Rth value of the transparent support made of the cellulose acetate film were adjusted as shown in Table 2, except that the optical compensation film was produced, in the same manner as above, except that the liquid crystal display device No. .25-40 was produced. In addition, the used cellulose acetate films all had a slow axis substantially coinciding with the direction in which the average refractive index of the membrane surface becomes the maximum.

<Measurement of leakage light of manufactured liquid crystal display device>

The leakage light by observation from the inclination of 60 degrees of liquid crystal display devices Nos. 25 to 40 thus produced was measured. The results are shown in Table 2.

Table 2: Black display transmittance at viewing angle of 60 ° left and right

Example 4

<Production of Optical Compensation Film>

By the method similar to the manufacturing method of the transparent support body which consists of the cellulose acetate film produced in Example 3, the transparent support body adjusted to Re value = 10 nm and Rth = 76 nm was produced. This film had a slow axis substantially coincident with the direction in which the average refractive index of the membrane surface was maximized. Furthermore, this support body was saponified, and the alignment film used in Example 3 was apply | coated on it. In addition, a rubbing treatment was carried out in the direction of 45 ° with respect to the longitudinal direction, and the coating liquid composition for the optically anisotropic layer (A) used in Example 3 was continuously applied, dried, and heated using a bar coater (orientation ripening). Then, ultraviolet irradiation was again performed to form an optically anisotropic layer having a thickness of 0.43 mu m. The optically anisotropic layer had a slow axis in the direction of 45 degrees with respect to the longitudinal direction of the transparent support. The retardation value in 550 nm was 53 nm.

The optical compensation film which consists of the produced optically anisotropic layer and the transparent support body is made into the transparent support body which consists of a cellulose acetate film between the upper polarizing film 1 and the upper substrate 5 for liquid crystal cells in FIG. 1 (Re = 10 nm, Rth = 176 nm) was attached in contact with the polarizing film 1. That is, the liquid crystal display device of the aspect which the transparent protective film 3 also served as the transparent support body of the optically anisotropic layer which has optical compensation ability was produced. The rest of the configuration was the same as in Example 1. That is, the axial angle of the slow axis of the upper protective film, the absorption axis of the polarizing film, and the slow axis of the lower protective film of the upper polarizing plate is set to (0 °, 45 °, 0 °) with reference to the display device horizontal direction, and is optically anisotropic. The slow axis (rubbing direction) of the layer was 45 degrees, and the axial angle of the lower polarizing plate was (0 degrees, -45 degrees, 0 degrees).

In the production of the optical compensation film, liquid crystal display devices Nos. 41 to 46 were produced in the same manner as above except that the Re value of the optically anisotropic layer was adjusted as shown in Table 3 to produce an optical compensation film.

<Measurement of leakage light of manufactured liquid crystal display device>

Thus, the leakage light by observation from 60 degrees of inclination of the produced liquid crystal display devices No.41-46 was measured. The results are shown in Table 3.

Table 3: Black display transmittance (%) at left and right 60 ° viewing angle

Example 5

The liquid crystal display device was produced like Example 1 except having used the cellulose triacetate film of Re value 0 nm and RtH value 133 nm as a protective film of a vertical polarizing plate. That is, the axial angles of the slow axis of the upper passivation film of the upper polarizing plate, the absorption axis of the polarization film, and the slow axis of the lower passivation film are (0 °, 45 °, 0 °) with reference to the horizontal direction of the display device. The axial angle of the polarizing plate was set to (0 °, -45 °, 0 °). In addition, the used cellulose acetate film had the slow axis substantially coinciding with the direction in which the average refractive index of a membrane surface becomes the maximum.

Liquid crystal display devices No. 47 to 70 were produced in the same manner as above except that a cellulose triacetate film showing various Re values and Rth values was used as a protective film for the vertical polarizing plate as shown in Table 4 below. In addition, all the used cellulose acetate films had the slow axis substantially coinciding with the direction in which the average refractive index of a membrane surface becomes the maximum.

<Measurement of leaked light of manufactured liquid crystal display device>

The leakage light observed from the inclination of 60 degrees of liquid crystal display devices Nos. 47 to 70 thus produced was measured. The results are shown in Table 4.

Table 4: Black display transmittance (%) at left and right 60 ° viewing angle

Example 6

In Example 1, the stretching direction of the polarizing film was 90 degrees with respect to the film longitudinal direction. Using a so-called conventional axial uniaxially stretched tenter stretching machine, a PVA-based film having a disc thickness of 100 µm is dyed in a dichroic material dye bath, a crosslinking agent solution is applied by an application means, and interlocked with a tenter stretching machine. After being uniaxially stretched in the width direction under an atmosphere of 30 ° to 80 ° and 70 to 99% RH, the width was kept substantially constant and dried. The axial angles of the slow axis of the upper protective film, the absorption axis of the polarizing film, and the slow axis of the lower protective film are set to (0 °, 90 °, 0 °) with reference to the display device horizontal direction, and the axial angle of the lower polarizing plate is the same. It was set as (90 degrees, 0 degrees, 90 degrees). The other structure was the same as that of Example 1. The leakage light of the liquid crystal display device produced in this way was measured. The leakage light observed at the leftward 60 ° was 0.6%.

Example 7

<Production of liquid crystal cell>

A pair of transparent substrates 5, on which linear electrodes were formed and the alignment control film formed thereon, were prepared. The rod-shaped liquid crystal molecules 7 sandwiched between the substrates are oriented so as to have a slight angle with respect to the longitudinal direction of the linear electrode when no electric field is applied. In addition, the dielectric anisotropy of the liquid crystal in this case assumes a quantity. When an electric field is applied, the liquid crystal molecules 7 change their directions in the electric field direction. By arranging the polarizing plate 1 at a predetermined angle, the light transmittance can be changed. In addition, the angle which the electric field direction with respect to the surface of the board | substrate 5 makes is actually 20 degrees or less, and it is preferable that it is substantially parallel. Hereinafter, in this invention, what is 20 degrees or less is generically represented by a parallel electric field. Moreover, even if an electrode is divided into upper and lower board | substrates, or an electrode is formed only in one board | substrate, the effect is the same.

As the liquid crystal material, a nematic liquid crystal having a dielectric constant anisotropy Δε, a value of 13.2, and a refractive index anisotropy Δn of 0.081 (589 nm, 20 ° C) was used. The thickness (gap) of the liquid crystal layer was made more than 2.8 micrometers and less than 4.5 micrometers. This means that when the retardation Δn · d is more than 0.25 µm and less than 0.32 µm, the transmittance characteristic with little wavelength dependence within the range of visible light is obtained. By the combination of the alignment film and the polarizing plate described later, the maximum transmittance can be obtained when the liquid crystal molecules are rotated by 45 degrees from the rubbing direction to the electric field direction. In addition, the thickness (gap) of the liquid crystal layer is controlled by polymer beads. Of course, the same gap can also be formed by glass beads, fibers and resin columnar spacers.

The upper and lower polarizing plate protective film consists of a cellulose acetate film, and a saponification-treated commercially available cellulose acetate film (Fujitaek TD80UF, manufactured by latter photographic film) is used for the upper and lower polarizing plate protective film far from the liquid crystal layer. The value was 3 nm and the Rth value was set to 50 nm. In addition, what was produced and saponified by the following method was used for the transparent protective film of the side close to the liquid crystal cell of an up-and-down polarizing plate. Re value is 10 nm and Rth value is 80 nm in the transparent protective film of the side near the liquid crystal layer of an upper polarizing plate, Re value is 3 nm and Rth value is 50 in the transparent protective film of the side near the liquid crystal layer of a lower polarizing plate. What was nm was used. Next, an optically anisotropic layer was formed on the transparent protective film of the side close to the liquid crystal layer of an upper polarizing film, and it was arrange | positioned between a liquid crystal cell and a transparent protective film. The axial angles of the slow axis of the upper protective film, the absorption axis of the polarizing film, and the slow axis of the lower protective film are set to (0 °, 90 °, 0 °) with reference to the display device horizontal direction, and the axial angle of the lower polarizing plate is the same. It was set as (90 degrees, 0 degrees, 90 degrees). Moreover, all the cellulose acetate films used for the transparent protective film had the slow axis substantially coinciding with the direction in which the average refractive index of a film surface becomes the maximum.

The optically anisotropic layer disposed between the transparent protective film of the upper polarizing plate and the liquid crystal cell was formed by using the transparent protective film as a support and orienting the disk-shaped compound vertically. The retardation value was 150 nm, the crossing angle of the orientation control direction and the polarizing film absorption axis was 90 degrees. The leakage light of the liquid crystal display device produced in this way was measured. The leakage light observed at 60 ° in the left direction was 0.1%.

Moreover, even if the protective film arrangement | positioning of the polarizing plate made into the upper polarizing plate near the liquid crystal layer is reversed here, an equivalent effect is acquired.

Example 8

In Example 7, the other constitutions were the same except that the axial angles of the absorption axis and the slow axis of the upper and lower polarizers were set to (0 °, 0 °, 0 °) and the same (90 °, 90 °, 90 °). In this case, the leakage light observed at 60 ° in the left direction was 0.2%.

Example 9

In Example 8, the optically anisotropic layer disposed between the transparent protective film of the upper polarizing plate and the liquid crystal cell was changed to a polyolefin-based stretched film (for example, atone) (thickness 80 µm, retardation 70 nm) in a layer formed of a disk compound. The other configuration was the same. The leakage light observed in the left direction 60 ° was 0.3%.

[Example 10]

In Example 8, the optically anisotropic layer was not disposed. The leakage light observed at the leftward 60 ° was 0.5%.

Example 11

The liquid crystal display device of the structure shown in FIG. 2 was produced. That is, the upper polarizing plate 1A which consists of a protective film (not shown), the upper polarizing film 1, and the protective film 3 from an observation direction (upper), a liquid crystal cell (upper substrate 5, liquid crystal layer 7, The lower substrate 8, the optical compensation layer 10, the protective film 12, the lower polarizing film 14, and the lower polarizing plate 14A including the protective film (not shown) are laminated, and the lower polarizing plate 14A is laminated. Further below, the backlight (not shown) using the cold cathode fluorescent lamp was arrange | positioned.

Below, the manufacturing method of each used member is demonstrated.

(Production of IPS Mode Liquid Crystal Cell)

3 is a cross-sectional view of the liquid crystal display device. On one side of the pair of transparent substrates, a linear electrode made of ITO (which may be a metal such as chromium or aluminum) is formed inside the substrate, and an alignment control film (not shown) is formed thereon. The rod-shaped liquid crystal component 7 sandwiched between the substrates is oriented so as to have a slight angle with respect to the longitudinal direction of the linear electrode when no electric field is applied. In addition, the dielectric constant anisotropy of the liquid crystal in this case assumes a quantity. When an electric field is applied, the liquid crystal molecules 7 change their directions in the electric field direction. And the upper polarizing plate 1A and the lower polarizing plate 14A of the said structure were arrange | positioned at predetermined angle. In addition, the angle which the electric field direction with respect to the surface of the board | substrate 8 makes was a parallel electric field. Here, parallel electric current means that the angle which the electric field direction with respect to the surface of a board | substrate makes is 20 degrees or less, More preferably, it is 10 degrees or less, More preferably, it is parallel. Moreover, even if an electrode is divided into upper and lower board | substrates, or an electrode is formed only in one board | substrate, the effect is the same.

The liquid crystal material has a dielectric constant anisotropy Δε of positive 13.2. The refractive index anisotropy (DELTA) n used the nematic liquid crystal of 0.085 (589 nm, 20 degree | times) (MLC9100-100 by Merck Co., Ltd.). The thickness (gap) of the liquid crystal layer was 3.5 μm.

(Production of polarizing plate)

The following composition was put into the mixing tank, it stirred while heating, each component was melt | dissolved, and the cellulose acetate solution which has the following composition was prepared.

Composition of Cellulose Acetate Solution

100 parts by mass of cellulose acetate having a degree of oxidation of 60.9%

Triphenyl phosphate (plasticizer) 7.8 parts by mass

Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by mass

300 parts by mass of methylene chloride (first solvent)

54 parts by mass of methanol (second solvent)

11 parts by mass of 1-butanol (third solvent)

To the other mixing tank, 16 parts by mass of the following retardation increasing agent, 80 parts by mass of methylene chloride and 20 parts by mass of methanol were added and stirred while heating to prepare a retardation increasing agent solution. Then, 7 parts by mass of the obtained retardation synergist solution was mixed with 487 parts by mass of a cellulose acetate solution, and sufficiently stirred to prepare a dope.

Retardation synergist

The obtained dope was cast using a band softener. After the film surface temperature on a band became 40 degreeC, it dried for 1 minute by 60 degreeC warm air, and removed the film from the band. Next, the film was dried for 10 minutes with a drying air of 140 ° C. to prepare a cellulose acetate film having a thickness of 100 μm.

The optical characteristic of this cellulose acetate film was measured using the automatic birefringence meter (KOBRA-21ADH, the product made from OHK Watch Co., Ltd.). As a result, it was Re = 10 (nm) and Rth = 102 (nm).

(Production of optical compensation layer)

The surface of the said cellulose acetate film was saponified, and the oriented-film coating liquid of the following composition was apply | coated so that it might become 20 ml / m <2> by the wire bar coater. Then, it dried for 60 second by the warm air of 60 degreeC, and 120 second by the warm air of 100 degreeC again. The film thus formed was subjected to a rubbing treatment in a direction parallel to the slow axis direction of the film.

Composition of alignment film coating liquid

15 parts by mass of the following modified polyvinyl alcohol

334 parts by mass of water

100 parts by mass of methanol

Glutalaldehyde 1 part by mass

0.3 parts by mass of paratoluenesulfonic acid

Modified polyvinyl alcohol

0.9 g of the following discotic liquid crystalline compounds, ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), 0.2 g, a photopolymerization initiator (Irugacure 907, manufactured by Chiba Chemical Co., Ltd.) 0.06 g 0.02 g of a sensitizer (Kayacure DTEX, Nippon Kayaku Co., Ltd.) and 0.01 g of the following air interface side vertical aligning agents were dissolved in 3.9 g of methyl ethyl ketone. This solution was applied onto the alignment film with a wire bar of # 3.4. Moreover, it adhered to the metal mold | die and heated for 3 minutes in 125 degreeC thermostat, and orientated the discotic liquid crystalline compound. Next, UV irradiation was carried out for 30 seconds using a 120 W / cm high pressure mercury lamp at 100 ° C. to crosslink the discotic liquid crystal compound. Thereafter, it was allowed to cool to room temperature. In this way, an optical compensation layer was produced.

Disco disc by measuring the light incident angle dependence of Re of the optical compensation layer using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oshi Measuring Instruments Co., Ltd.), and subtracting the contribution of the cellulose acetate film measured in advance. As a result of calculating the optical characteristics of only the tick liquid crystal layer, it was confirmed that Re was 50 nm, Rth was -25 nm, and the average inclination angle of the liquid crystal was 89.9 degrees, and the discotic liquid crystal was oriented perpendicular to the film plane. In addition, the direction of the slow axis was parallel to the rubbing direction (orientation control direction) of the alignment film.

Iodine was adsorbed on the stretched polyvinyl alcohol film to prepare a polarizing film. Using the polyvinyl alcohol adhesive, the produced optical compensation layer was adhered to one side of the polarizing film so that the cellulose acetate film would be the polarizing film side. The transmission axis of the polarizing film and the slow axis of the optical compensation layer were arranged to be parallel to each other. The saponification process was carried out to the commercially available cellulose acetate film (Fujitaek TD80UF, the Fuji photograph film company make), and it adhere | attached on the opposite side to the polarizing film using the polyvinyl alcohol-type adhesive agent. Thus, the lower polarizing plate 14A was produced. This was bonded to one of the IPS mode liquid crystal cells produced above so that the slow axis of the optical compensation layer was parallel to the rubbing direction of the liquid crystal cell, and the discotic liquid crystal coated surface side was the liquid crystal cell side. Subsequently, a polarizing plate (HLC2-5618, manufactured by Sanlitz Co., Ltd.) commercially available on the other side of the IPS mode liquid crystal cell was used as the upper polarizing plate 1A and bonded in a cross nicol arrangement to produce a liquid crystal display device. Re of a pair of protective film of this polarizing plate was 3 nm, and Rth was 38 nm.

Also, the axial angles of the upper polarizing plate and the polarizing film absorption axis are 0 degrees with respect to the horizontal direction of the display device, the slow axis of the upper protective film is 0 degrees, the orientation control direction (rubbing direction) of the upper substrate of the liquid crystal cell is 90 degrees, Similarly, the axial angle of the lower polarizer is 90 degrees, the orientation control direction of the lower optical compensation layer is 90 degrees, the orientation control direction (rubbing direction) of the lower substrate of the liquid crystal cell is 270 degrees, the slow axis of the lower protective film is 90 degrees, and the lower polarization is The membrane absorption axis was set to 90 degrees.

(Measurement of leakage light of manufactured liquid crystal display device)

The leakage light of the liquid crystal display device produced in this way was measured. The measuring instrument used (luminance meter BM-5, product made by Topcon Corporation) as the transmittance | permeability as ratio of light source brightness | luminance and leaked light brightness. The leakage light observed at 70 degrees in the left oblique direction was 0.28%. Moreover, it was the same leak light transmittance even if observed from the lower side. That is, the same effect was acquired even if this structure was changed around upper and lower sides centering on a liquid crystal cell.

Example 12

In the liquid crystal display device produced in Example 1, the slow axis of the lower protective film was 0 degrees as a reference in the horizontal direction of the display device. The other structure was the same as that of Example 1. The leakage light observed at 70 degrees in the left tilt direction was 0.35%.

Example 13

A commercially available polarizing plate (HLC2-5618, manufactured by Sanlitz Co., Ltd.) was bonded to both sides of the produced IPS mode liquid crystal cell 1 in a cross nicol batch to produce a liquid crystal display device. An optical compensation layer was not used. In the above liquid crystal display device, a polarizing plate was bonded in the same manner as in Example 1 so that the transmission axis of the upper polarizing plate was parallel to the rubbing direction of the liquid crystal cell. The leakage light of the liquid crystal display device produced in this way was measured. The leakage light observed at 70 degrees in the left oblique direction was 0.72%.

Example 14

In the configuration of Example 13, furthermore, using the TD80 (Re is 3nm, Rth is 38nm) in the protective film support used in Example 11 for the upper polarizing plate, and the optical compensation layer parallel to the support slow axis in the same manner as in Example 11 It was formed by rubbing treatment in the direction. The prepared protective film with the optical compensation layer was attached to the liquid crystal cell side protective film of the upper polarizing plate with an adhesive such that the slow axes of each other were approximately perpendicular to each other. The leakage light observed at 70 degrees in the left tilt direction was 0.35%.

[Example 15]

In the liquid crystal display device produced in Example 11, the orientation control direction of the discotic liquid crystal compound was set to 90 degrees in the same manner as in Example 11, and the other configuration was the same as in Example 1. The leakage light observed at 70 degrees in the left tilt direction was 0.75%.

[Example 16]

In the liquid crystal display device produced in Example 11, the protective film of the liquid crystal cell side of an upper polarizing plate used the protective film of the lower polarizing plate, and the Re value is 10 nm, and the Rth value is the same as 102 nm. In addition, the optical compensation layer was not arrange | positioned. The leakage light when observed at 70 degrees in the left tilt direction was 0.6%.

The present inventors have succeeded in producing an elliptically polarizing plate having a function of optically compensating a liquid crystal cell with the same configuration as a conventional liquid crystal display device by adjusting the polarizing film, the protective film and the material and manufacturing method of the liquid crystal cell. It was. Moreover, as a result of attaching this polarizing plate to VA type and IPS type liquid crystal cells and using it for a liquid crystal display device, not only the display quality but also the viewing angle were remarkably improved. Moreover, the process of laminating | stacking without adjusting the angle of the conventional one or several retardation film and a polarizing plate is not required, and manufacture by roll-to-roll was attained. That is, according to the present invention, it is possible to provide a liquid crystal display device, in particular a VA type and an IPS type liquid crystal display device, in which not only the display quality but also the viewing angle is remarkably improved with a simple configuration. In addition, according to the present invention, it is possible to provide a polarizing plate which not only has a polarizing function but also contributes to the enlargement of the viewing angle of the liquid crystal display device, and which can be easily manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic diagram which shows one Embodiment of the liquid crystal display device of this invention.

Fig. 2 is a schematic diagram showing another embodiment of the liquid crystal display device of the present invention.

3 is a schematic diagram showing the configuration of a liquid crystal display device in an IPS mode.

Description of the main symbols in the drawings

1: upper polarizing film

1A: upper polarizer

2: absorption axis of upper polarizing film

3, 3a: upper protective film

4: slow axis of upper protective film

5: liquid crystal cell upper substrate

6: rubbing direction for upper substrate liquid crystal alignment

7: liquid crystalline molecule

8: liquid crystal cell lower substrate

9: rubbing direction for lower substrate liquid crystal alignment

10: optical compensation layer

11: orientation control direction of the optical compensation layer

12, 12a: lower protective film

13: slow axis of the lower protective film

14: lower polarizing film

14A: lower polarizer

15: absorption axis of lower polarizing film

16: linear phase electrode

Claims (9)

It has a pair of board | substrates opposingly arranged at least one side with an electrode, the liquid crystal layer clamped between the said board | substrates, and at least 1 polarizing film arrange | positioned outside the said liquid crystal layer, thickness d (micrometer) and refractive index anisotropy of the said liquid crystal layer An optical compensation film used for a liquid crystal display device having a product Δn · d of (Δn) of 0.1 to 1.0 μm, It consists of an optical compensation layer made of a compound having a protective film and a discotic structural unit in contact with the polarizing film, The protective film at any wavelength λ in the visible light region, −30 (nm) ≦ {(nx−ny) × d ₂ } ≦ 50 (nm), and -50 (nm) ≤ [{(nx + ny) / 2-nz} × d ₂ ] ≤300 (nm) (Wherein d ₂ (nm) is the thickness of the protective film, nx and ny (where ny <nx) is the in-plane major mean refractive index, nx is the major mean refractive index in the thickness direction, and nx, ny and nz are respectively) Orthogonal to each other), And an orientation control direction of the optical compensation layer and a slow axis of the protective film are disposed substantially parallel to the absorption axis of the polarizing film. A liquid crystal cell comprising at least one pair of substrates arranged opposite to each other with electrodes on one side, a liquid crystal layer comprising a nematic liquid crystal material sandwiched between the substrates and oriented almost parallel to the surface of the pair of substrates when no voltage is applied; And an optical compensation film used in a liquid crystal display device having a first polarizing film and a second polarizing film respectively disposed outside the liquid crystal cell. The optical compensation film is disposed between the second polarizing film and the liquid crystal cell, and at least has a protective film and an optical compensation layer in contact with the second polarizing film, The protective film at any wavelength λ in the visible light region, −30 (nm) ≦ {(nx−ny) × d ₂ } ≦ 50 (nm), and -50 (nm) ≤ [{(nx + ny) / 2-nz} × d ₂ ] ≤300 (nm) (Wherein d ₂ (nm) is the thickness of the protective film, nx and ny (where ny <nx) is the in-plane major mean refractive index, nx is the major mean refractive index in the thickness direction, and nx, ny and nz are respectively) Orthogonal to each other), The optical compensation layer is made of molecules of a compound having a discotic structural unit, the discotic surface is substantially perpendicular to the film surface, and And an alignment control direction of the optical compensation layer, a slow axis of the protective film, and an absorption axis of the second polarizing film, respectively, substantially parallel to each other. A liquid crystal display having at least one pair of substrates disposed opposite to each other with an electrode, a liquid crystal layer sandwiched between the substrates, and a first polarizing plate disposed outside the liquid crystal layer, The product (DELTA) n * d of the thickness d (micrometer) of the said liquid crystal layer and refractive index anisotropy (DELTA) n is 0.1-1.0 micrometer, The first polarizing plate has a pair of protective films sandwiching the polarizing film and the polarizing film, At least one of the pair of protective films has a slow axis substantially coincident with the direction in which the average refractive index of the film surface is maximized, and the slow axis of the protective film closer to the liquid crystal layer and the absorption axis of the polarizing film cross each other. , Of the pair of protective films, the protective film disposed on the side close to the liquid crystal layer has a thickness d ₁ (nm) and has three average refractive indices nx, ny, and nz in the x, y, and z axis directions orthogonal to each other, In the case where the main average refractive index in the plane parallel to the surface of the liquid crystal layer is nx and ny (where ny <nx) and the main average refractive index in the thickness direction of the liquid crystal layer is nz, at an arbitrary wavelength? Of the visible light region, −30 (nm) ≦ {(nx−ny) × d ₁ } ≦ 50 (nm), and -50 (nm) ≤ [{(nx + ny) / 2-nz} × d ₁ ] ≤300 (nm) Liquid crystal display that satisfies the relationship. 4. The liquid crystal display device according to claim 3, wherein the liquid crystal layer comprises a nematic liquid crystal material, and wherein the liquid crystal molecules of the nematic liquid crystal material are oriented almost perpendicular to the surface of the pair of substrates during black display. 4. The liquid crystal display device according to claim 3, wherein the liquid crystal layer comprises a nematic liquid crystal material, and wherein the liquid crystal molecules of the nematic liquid crystal material are oriented almost parallel to the surface of the pair of substrates during black display. A liquid crystal cell comprising a pair of substrates arranged to face each other with at least one electrode, a liquid crystal layer comprising a nematic liquid crystal material sandwiched by the substrate and oriented almost parallel to the surface of the pair of substrates when no voltage is applied, And at least a first polarizing plate and a second polarizing plate respectively disposed outside the liquid crystal cell. The first polarizing plate is formed of at least a polarizing film and a protective film formed on a surface close to the liquid crystal cell of the polarizing film, The second polarizing plate is formed of at least a polarizing film and a protective film and an optical compensation layer formed on a surface close to the liquid crystal cell of the polarizing film, The protective film formed in the surface close to the liquid crystal cell of the polarizing film of the second polarizing plate at any wavelength λ in the visible light region, −30 (nm) ≦ {(nx−ny) × d ₂ } ≦ 50 (nm), and -50 (nm) ≤ [{(nx + ny) / 2-nz} × d ₂ ] ≤300 (nm) (Wherein d ₂ (nm) is the thickness of the protective film, nx and ny (where ny <nx) is the in-plane major mean refractive index, nx is the major mean refractive index in the thickness direction, and nx, ny and nz are respectively) Orthogonal to each other), The optical compensation layer is made of a compound having a discotic structural unit, and the discotic surface of the compound is substantially perpendicular to the substrate surface, The liquid crystal display device wherein the orientation control direction of the optical compensation layer, the slow axis of the protective film formed on the surface close to the liquid crystal cell of the second polarizing film, and the absorption axis of the second polarizing plate are substantially parallel to each other. A polarizing film and a pair of protective films having refractive indexes interposed between the polarizing films, the protective films having a thickness d ₁ (nm) and having three average refractive indices nx in the x, y, and z axis directions orthogonal to each other; ny and nz, and when the in-plane main average refractive index is nx and ny (where ny <nx) and the main average refractive index in the thickness direction is nz, at an arbitrary wavelength? in the visible light region, −30 (nm) ≦ {(nx−ny) × d ₁ } ≦ 50 (nm), and -50 (nm) ≤ [{(nx + ny) / 2-nz} × 2] ≤300 (nm) Polarizer to satisfy. The polarizing plate of Claim 7 in which the slow axis of any one of the protective films of the said polarizing plate crosses the absorption axis of the said polarizing film. 9. The discotic surface of the compound according to claim 7 or 8, wherein the optical compensation layer has an optical compensation layer disposed on one surface of the pair of protective films, and the optical compensation layer has a discotic structural unit. A polarizing plate which is substantially perpendicular to the polarizing film, wherein the orientation control direction of the optical compensation layer, the slow axis of the protective film in contact with the optical compensation layer, and the absorption axis of the polarizing film are substantially parallel to each other.