HK1063218B - Liquid crystal display element, and use of phase difference film used the same for - Google Patents

Description

Liquid crystal display element and use of phase difference film used therein

Technical Field

The present invention relates to a vertical alignment type liquid crystal display element in which the long axes of liquid crystal molecules are aligned in a nearly vertical direction with respect to the substrate surface of a liquid crystal cell (セル) in the absence of an applied voltage.

Background

In general, a liquid crystal display device is mainly composed of a liquid crystal cell having a liquid crystal layer between a pair of substrates, a pair of polarizing films sandwiching the cell and disposed orthogonally, and a retardation film. Such liquid crystal display elements are widely used for small-sized objects such as watches and watches, computers, and large-sized objects such as monitors and televisions. In the liquid crystal display device, a tn (twisted nematic) type, in which liquid crystal molecules having positive dielectric anisotropy are used as liquid crystals, has been mainly used. In this TN mode, the orientation direction of the liquid crystal molecules adjacent to one substrate constituting the liquid crystal cell is twisted by about 90 ° with respect to the orientation direction of the liquid crystal molecules adjacent to the other substrate in the absence of an applied voltage.

TN liquid crystal display devices have been variously developed to achieve high quality black display and high contrast. In the TN mode, the long axes of the liquid crystal molecules must be aligned in a state of being substantially perpendicular to the substrate surface when a voltage is applied, and black is displayed. However, in the state where a voltage is applied, the liquid crystal molecules adjacent to the substrate maintain horizontal alignment, and the polarization state of light changes due to birefringence of the liquid crystal molecules. As a result, a completely black color cannot be displayed even when viewed from a direction perpendicular to the substrate. Thus, it is difficult to achieve high contrast.

In contrast, a vertically aligned liquid crystal display element, so-called va (vertical aligned) liquid crystal display element, is aligned in a direction approximately perpendicular to the long axes of liquid crystal molecules on a pair of substrates constituting a liquid crystal cell when no voltage is applied between the substrates. Since the liquid crystal molecules adjacent to the substrate are also aligned in a direction approximately perpendicular to the substrate surface, the polarization state of light passing through the liquid crystal layer does not change much. That is, the normal VA type is more excellent in display than the TN type, and is almost completely black in display when viewed in a direction perpendicular to the substrate, and high contrast can be realized.

For example, japanese patent laid-open publication No. h 11-95208 discloses a vertically aligned nematic liquid crystal display device including a liquid crystal cell, a pair of polarizing films disposed above and below the liquid crystal cell, and a viewing angle compensating retardation film disposed between the liquid crystal cell and at least one of the polarizing films, wherein absorption axes of the polarizing films are orthogonal to each other, and the viewing angle compensating retardation film is composed of one or two retardation films. Specifically, it discloses a retardation film obtained by using one retardation film or two laminated films between the liquid crystal cell and one polarizing film (refer to claim 1 and examples 1 to 4 (paragraphs 0030 to 0034)).

Jp 2000 a-131693 a discloses a VA-type liquid crystal display device in which a specific biaxial retardation film is disposed between a substrate and a polarizing plate, and the slow axis in the plane of the retardation film is disposed approximately parallel to or perpendicular to the absorption axis of the polarizing plate, and the polarizing plate is disposed on the same side as the retardation film with respect to a liquid crystal layer. Specifically, a specific two-piece retardation plate laminate (see paragraph 0064, fig. 54) and an object in which two specific two retardation plates are respectively disposed one at each position where a liquid crystal cell is sandwiched (see paragraph 0070, fig. 60) are disclosed.

However, any of the VA-type liquid crystal display devices described in these publications can improve only the viewing angle at a specific wavelength. That is, a liquid crystal display element displaying black reduces the transmittance of a wavelength when viewed from an oblique direction to enlarge a viewing angle. However, there is a problem that the black color is colored and visible due to the light having a wavelength other than the specific wavelength being lost.

The main object of the present invention is to provide a novel VA mode liquid crystal display device.

Another object of the present invention is to provide a VA mode liquid crystal display device which displays black with less light leakage in a visible light range and achromatic color when displaying black.

It is another object of the present invention to provide a novel method for displaying black with less light leakage in the entire visible light range and without color by using a retardation film in a VA-type liquid crystal display device for displaying black.

The purpose and advantages of the present invention will be explained below.

Disclosure of Invention

The present inventors have examined the relationship between the problem of black coloration due to light leakage and the wavelength dispersion of transmitted light. That is, since viewing angle characteristics are improved only by a certain specific wavelength of the retardation film used, the above-described problem is caused, thereby generating light leakage. Therefore, the present inventors focused attention on the retardation wavelength dispersion characteristics of the retardation film. As a result, it was found that it is important to control the wavelength dispersion characteristics, and it was found that it is effective to use a plurality of specific phase difference films in combination, thereby completing the present invention.

In accordance with the present invention, it is an object and advantage of the present invention,

the present invention is a liquid crystal display element having a liquid crystal cell in which a liquid crystal is sandwiched between a pair of substrates, wherein the long axes of the liquid crystal molecules are oriented in a substantially vertical direction with respect to the substrate surfaces in the absence of an applied voltage, a 1 st and a 2 nd polarizing films sandwiching the liquid crystal cell and having polarizing axes orthogonal to each other, and at least 2 retardation films (A, C) in total present between the liquid crystal cell and the 1 st and the 2 nd polarizing films,

characterized in that the retardation film A satisfies the relationship of the following formula (1) and/or (2):

R(λ₁)/R(λ₂)＜1 (1)

K(λ₁)/K(λ₂)＜1 (2)

in the above formulas (1) and (2), R (lambda)₁) And R (lambda)₂) Respectively wavelength lambda₁And λ₂In-plane retardation of time retardation film, K (. lamda.)₁) And K (lambda)₁) Respectively wavelength lambda₁And λ₂Thickness direction phase difference of the phase difference film, wavelength lambda₁And λ₂Satisfies the condition that the lambda is more than 400nm₁＜λ₂The relationship of < 700nm in the wavelength range,

and the retardation film C satisfies the relationships of the following formulae (3) and (4) at the same time:

n_x≥n_y＞n_z (3)

1＜K(λ₁)/K(λ₂) (4)

here, n is_xIs the maximum refractive index in the retardation film plane, n_yN is a refractive index of an azimuth orthogonal to a direction representing a maximum refractive index in the retardation film plane_zRefractive index in linear direction of retardation film, K, lambda₁And λ₂The definitions of (a) are the same as above.

Brief description of the drawings

Fig. 1 shows an example of the structure of a liquid crystal display device of the present invention.

Fig. 2 shows an example of the structure of the liquid crystal display device of the present invention.

Fig. 3 shows an example of the structure of the liquid crystal display device of the present invention.

Fig. 4 shows an example of the structure of the liquid crystal display device of the present invention.

Fig. 5 shows an example of the structure of the liquid crystal display device of the present invention.

Fig. 6 shows an example of the structure of the liquid crystal display device of the present invention.

Description of the symbols

1P: no. 1 polarizing film

A: retardation film A

L: VA liquid crystal cell

C: retardation film C

2P: polarizing film of item 2

B: rear lighting

Detailed description of the invention

The vertical alignment liquid crystal cell (VA-type liquid crystal cell) of the present invention is a structure in which at least one transparent substrate having electrodes is arranged facing each other at a predetermined distance, and the long axes of liquid crystal molecules sandwiched therebetween are aligned substantially vertically to the substrates in the absence of an applied voltage. The substantially vertical orientation means that the average value of the angles formed by the substrates and the long axes of the liquid crystal molecules located in the display pixel portion is substantially vertical, and is generally 80 ° or more, more preferably 85 ° or more, and still more preferably 87 ° or more. Further, as described in Japanese patent laid-open No. 2001-235750, the liquid crystal may be aligned in parallel with the substrate except for the display pixel portion when no voltage is applied.

In the VA liquid crystal cell, since liquid crystals are vertically aligned between parallel substrates, the liquid crystals tilt in various azimuthal directions when a voltage is applied, so-called disorder degrees (ディスクリネ - ショソ) occur randomly in which alignment is discontinuous, and uniform display cannot be obtained. Many studies have been made on the degree of disorder, such as SID98DIGEST, (1998) p.1081 "A Wide Viewing Angle Polymer Stabilized Homeotropic alignment LCD" and Display99 Latewspaper (1999) p.31 "A Wide Viewing Angle Back Side Expo MVA TFT LCD with Novel Structure and Process" in which a protrusion is formed on a substrate, or in which a window is provided on a pixel electrode as described in JP-A-7-199190 to control the tilt direction of liquid crystal molecules when a voltage is applied. Further, as described in the section ジャ - プ, p.11, 2001, 8.2001, "development of ASV-LCD using Continuous Picture Alignment (CPA) type", a palm type agent is added to liquid crystal, and the liquid crystal is twisted and collapsed when a voltage is applied. The alignment state of liquid crystal when a voltage is applied to a vertical alignment type liquid crystal cell has various forms, but the present invention is not limited to the alignment state of liquid crystal when a voltage is applied.

In the case of a transmissive liquid crystal display device, for example, the liquid crystal cell used in the present invention has a retardation (hereinafter referred to as "K (550)") in the thickness direction of the liquid crystal cell at a wavelength of 550nm set to a value of about-400 to-200 nm. Here, the thickness direction phase difference is expressed by the product of the distance between the substrates sandwiching the liquid crystal and the refractive index anisotropy of the liquid crystal in the direction perpendicular to the substrates.

In the case of a transmissive liquid crystal display device, for example, the liquid crystal display device of the present invention is normally provided with a backlight on the side opposite to the observation side, and the 1 st and 2 nd polarizing films are arranged above and below the liquid crystal cell at angles such that their transmission axes are substantially orthogonal to each other.

As for the positional relationship of the phase difference film and the polarizing film, at least one of the phase difference films a and C is disposed between at least one of the liquid crystal cell and the 1 st polarizing film or between the liquid crystal cell and the 2 nd polarizing film. Specific configurations are shown in fig. 1 to 6, for example.

The retardation film a is preferably adjacent to the 1 st or 2 nd polarizing film in order to effectively compensate for the apparent axis displacement (axle ずれ) of the polarizing plate. In order to effectively compensate for the thickness direction retardation of the liquid crystal cell, the retardation film C is preferably adjacent to the liquid crystal cell. The term "adjacent" in the present invention means that they are bonded directly to each other by, for example, an adhesive.

In order not to impart a phase difference to the polarized light incident on the front surface, the retardation film a and/or C is preferably arranged such that the slow axis thereof is substantially parallel to or orthogonal to the polarizing axis of the 1 st and/or 2 nd polarizing film. A pair of other retardation films (for example, λ/4 plates) having almost the same characteristics may be disposed between the liquid crystal cell and the 1 st polarizing film and between the liquid crystal cell and the 2 nd polarizing film, and the slow axes of the other retardation films may be substantially parallel or orthogonal to each other.

The retardation films A and C preferably have an in-plane retardation (hereinafter referred to as "R (550)") at a wavelength of 550nm of 300nm or less and a K (550) of 400nm or less, but the optimum value may vary depending on the average refractive index (hereinafter referred to as "n") of the retardation films A and C, the combination and arrangement of the retardation films A and C.

Here, the in-plane retardation R (λ) and the thickness direction retardation K (λ) of the retardation film in the present invention are represented by the following formulas (12) and (13), respectively.

R＝(n_x-n_y)×d (12)

K＝{(n_x+n_y)/2-n_z}×d (13)

In the above formula, n_x、n_y、n_zThe three-dimensional refractive index of the retardation film is a refractive index in the x-axis direction, the y-axis direction, and the z-axis direction perpendicular to the retardation film in the plane of the retardation film. Further, d is the thickness (nm) of the retardation film. Lambda is a wavelength of 400 to 700 nm.

That is, n_x、n_y、n_zIs an index showing the optical anisotropy of the retardation film. Particularly with the phase difference film of the present invention,

n_xis the maximum refractive index in the film plane

n_yA refractive index of an orientation orthogonal to a direction indicating a maximum refractive index in a film surface

n_zThe refractive index in the film linear direction.

Here, the optical anisotropy is positive when the refractive index in the orientation direction of the polymer main chain is the maximum in the chemical structure, and is negative when the refractive index in the orientation direction is the minimum, in the stretching direction in which the orientation degree is further increased in the uniaxial stretching or biaxial stretching of the polymer film. In the present invention, the three-dimensional refractive index is obtained by a method of obtaining the optical anisotropy of the retardation film as a refractive index ellipsoid by a known refractive index ellipsoid equation. The three-dimensional refractive index is preferably defined by the wavelength of the light source used because it depends on the wavelength of the light source used.

The refractive index anisotropies of the retardation films a and C of the present invention are classified as follows.

Phase difference film A: n is_x＞n_yn_z

Phase difference film B: n is_x≥n_y＞n_z

The present invention uses at least 2 retardation films in total, namely, a retardation film a and a retardation film C. The retardation film a has a substantial property that the smaller the measurement wavelength in the visible light region, the smaller the substantial phase difference, and the retardation film C has a property that the smaller the measurement wavelength, the larger the substantial phase difference.

The above-mentioned problems can be solved by combining these two specific retardation films, and the reason for this is considered as follows. The retardation film A mainly compensates for the apparent axis deviation of the polarizing plate, and the retardation film C mainly compensates for the thickness direction retardation between the pair of polarizing films. Here, in order to compensate for the apparent axis deviation of the polarizing plate in a wide wavelength region, it is preferable to provide a retardation (deg) of the polarized light at an equal angle independent of the wavelength. This means that when the phase difference is expressed by nm, the shorter the wavelength, the smaller the phase difference. On the other hand, in order to compensate for a phase difference in the thickness direction existing between a pair of polarizing films in a wide wavelength region, a TAC film or the like as a protective layer for the polarizing films is used between the pair of polarizing films in addition to the VA liquid crystal cell. They have optical anisotropy in which it is desirable to have wavelength dispersion of retardation similar to that of a VA liquid crystal cell having a large thickness direction retardation, that is, to have a characteristic that the retardation is larger as the wavelength is shorter.

That is, the wavelength dispersion characteristic of the retardation film a preferably satisfies the relationship of the following formula (1) and/or (2) for a single layer. In other words, the retardation film has a characteristic that the in-plane and/or thickness direction retardation (R, K) is smaller as the wavelength is smaller. The retardation film a is required to improve the viewing angle characteristics, and is advantageous from the viewpoint of cost and productivity, because it does not include a plurality of retardation films other than the retardation film a laminated to satisfy the above characteristics, but basically includes a single layer, that is, 1 film. As described later, the retardation film a may contain a small amount of liquid crystal in order to control the above characteristics.

R(λ1)/R(λ2)＜1 (1)

K(λ1)/K(λ2)＜1 (2)

Here, λ 1 and λ 2 are arbitrary wavelengths satisfying the following expression (14).

400nm＜λ1＜λ2＜700nm (14)

The retardation film A preferably satisfies the following formulae (1-1) and/or (1-2). Further, having a wavelength dispersion characteristic satisfying the following expression (5) and/or (6) can compensate in a wide wavelength region. R and K are as defined above.

R(450)/R(550)＜1 (1-1)

K(450)/K(550)＜1 (1-2)

1＜R(650)/R(550) (5)

1＜K(650)/K(550) (6)

More preferably, the polarizing plate has a wavelength dispersion characteristic satisfying the relationship of the following expressions (10) and (11), and as the ratio of the phase difference is closer to the ratio of the measurement wavelengths, the apparent axis deviation of the polarizing plate can be compensated more favorably.

0.6＜R(450)/R(550)＜0.97 (10)

1.01＜R(650)/R(550)＜1.4 (11)

The retardation film a preferably satisfies the following formula (7).

10＜R(550)＜300 (7)

The retardation film C used in the present invention satisfies the relationships of the following formulae (3) and (4) (preferably (4-1) and/or (4-2)). That is, the retardation film C is usually a biaxially stretched film having a refractive index n in the thickness direction_zAnd minimum. Further, the smaller the wavelength, the larger the phase difference K in the thickness direction is.

n_x≥n_y＞n_z (3)

1＜K(λ₁)/K(λ₂) (4)

K(650)/K(550)＜1 (4-1)

1＜K(450)/K(550) (4-2)

The retardation film C preferably satisfies the relationship of the following formula (8), whereby the thickness direction retardation of the liquid crystal cell can be effectively compensated.

50＜K(550)＜400 (8)

The retardation film C preferably satisfies the relationship of the following formula (9) so as not to hinder the effect of the a film for compensating the apparent axis shift of the polarizing plate.

R(550)＜30 (9)

In particular, in the present invention, when the retardation a satisfies the above formula (7) and the retardation film C satisfies the above formula (8), the apparent axial shift of the polarizing plate and the retardation in the thickness direction of the liquid crystal cell can be compensated for, respectively, favorably.

In the liquid crystal display device of the present invention, when both the 1 st and 2 nd polarizing films are composed of a polarizing element having protective layers on both sides described later, it is preferable to use the retardation films A and C so that the sum of the phase differences in the thickness direction at a wavelength of 550nm between the retardation films A and C and the liquid crystal cell is-200 to 200 nm. When other retardation films are used in addition to the retardation films A and C, it is preferable to use the retardation films A and C so that the total of the retardation in the thickness direction including the retardation films is-200 to 200 nm.

As the retardation film A used in the present invention, for example, those described in WO00/26705 (corresponding to EP 1045261) can be used.

Specifically, a polymer alignment film satisfying the following conditions (a) or (b) can be used as the retardation film a.

(a) (1) a film comprising a polymer containing a polymer monomer unit having positive refractive index anisotropy (hereinafter referred to as a 1 st monomer unit) and a polymer monomer unit having negative refractive index anisotropy (hereinafter referred to as a 2 nd monomer unit),

(2) the ratio of R (450)/R (550) of the polymer based on the 1 st monomer unit is smaller than that of R (450)/R (550) of the polymer based on the 2 nd monomer unit, and

(3) a polymer alignment film having positive refractive index anisotropy.

(b) (1) a film comprising a polymer containing a monomer unit forming a polymer having positive refractive index anisotropy (hereinafter referred to as a 1 st monomer unit) and a monomer unit forming a polymer having negative refractive index anisotropy (hereinafter referred to as a 2 nd monomer unit),

(2) the ratio of R (450)/R (550) of the polymer based on the 1 st monomer unit is larger than that of R (450)/R (550) of the polymer based on the 2 nd monomer unit, and

(3) a polymer alignment film having negative refractive index anisotropy.

Examples of the form satisfying the above conditions (a) and (b) include those satisfying the following conditions (c) and (d).

(c) (1) a film comprising a polymer mixture comprising a polymer having positive refractive index anisotropy and a polymer having negative refractive index anisotropy and/or a copolymer comprising a polymer monomer unit having positive refractive index anisotropy and a polymer monomer unit having negative refractive index anisotropy,

(2) r (450)/R (550) of the polymer having positive refractive index anisotropy is smaller than R (450)/R (550) of the polymer having negative refractive index anisotropy, and

(3) a polymer alignment film having positive refractive index anisotropy.

(d) (1) a film comprising a polymer mixture comprising a polymer having positive refractive index anisotropy and a polymer having negative refractive index anisotropy and/or a copolymer comprising a polymer monomer unit having positive refractive index anisotropy and a polymer monomer unit having negative refractive index anisotropy,

(2) the ratio of R (450)/R (550) of the polymer based on the 1 st monomer unit is larger than that of R (450)/R (550) of the polymer based on the 2 nd monomer unit, and

(3) a polymer alignment film having negative refractive index anisotropy.

The polymer having positive or negative refractive index anisotropy here means a polymer which can provide a polymer alignment film having positive or negative refractive index anisotropy.

The following is a description of specific materials for the polymer alignment film.

The polymer material is often heated during molding and processing, and is used for different purposes, but is preferably excellent in heat resistance, and has a glass transition temperature of preferably 120 ℃ or higher, more preferably 140 ℃ or higher. If the temperature is less than 120 ℃, problems such as orientation relaxation may occur depending on the use conditions of the display element.

The polymer material preferably has a water absorption of 1 wt% or less. When the water absorption of the polymer material exceeds 1% by weight, there may be problems such as change in optical properties and dimensional change when used as a retardation film. The water absorption of the polymer material is preferably 0.5 wt% or less.

The polymer material is not particularly limited, but is preferably a material which has excellent heat resistance and good optical properties and can be formed into a film from a solution. Examples thereof include thermoplastic polymers such as polyarylate, polyester, polycarbonate, polyolefin, polyether, polysulfone and polyethersulfone.

When these thermoplastic polymers are used, as described above, a copolymer composed of a polymer mixture (a mixture of 2 or more polymers) composed of a polymer having positive refractive index anisotropy and a polymer having negative refractive index anisotropy, and a monomer unit of a polymer having positive refractive index anisotropy and a monomer unit of a polymer having negative refractive index anisotropy is more preferable. Among them, 2 or more kinds of polymers may be used in combination, and 1 or more kinds of polymers and 1 or more kinds of copolymers may be used in combination.

In the case of a polymer mixture, it is preferable that the refractive indices of the mixture and the various polymers are substantially equal to each other in view of the optical transparency. Specific combinations of the mixture polymers include, for example, a combination of a polymer having negative optical anisotropy, which is poly (methyl methacrylate), and a polymer having positive optical anisotropy, which is at least one polymer selected from the group consisting of poly (vinylidene fluoride), poly (ethylene oxide), and poly (vinylidene fluoride-co-trifluoroethylene); a combination of polyphenylene ether as a polymer having positive optical anisotropy and at least one polymer selected from the group consisting of polystyrene, poly (styrene-co-lauroyl maleimide), poly (styrene-co-cyclohexyl maleimide) and poly (styrene-co-phenylmaleimide) as a polymer having negative optical anisotropy; a combination formed from poly (styrene-co-maleic anhydride) having negative optical anisotropy and polycarbonate having positive optical anisotropy; a combination formed of poly (acrylonitrile-co-butadiene) having positive optical anisotropy and poly (acrylonitrile-co-styrene) having negative optical anisotropy; a combination formed of a polycarbonate having positive optical anisotropy and a polycarbonate having negative optical anisotropy; however, it is not limited thereto. Particularly, from the viewpoint of transparency, a mixture of a polycarbonate having positive optical anisotropy and a polycarbonate having negative optical anisotropy is preferable.

Examples of the copolymer include poly (butadiene-co-polystyrene), poly (ethylene-co-polystyrene), poly (acrylonitrile-co-butadiene-co-styrene), polycarbonate copolymer, polyester carbonate copolymer, and polyarylate copolymer. In particular, since a portion having a fluorene skeleton can obtain negative optical anisotropy, a polycarbonate copolymer, a polyester carbonate copolymer, a polyarylate copolymer, or the like having a fluorene skeleton is more preferable.

Among them, a polycarbonate copolymer or a mixed polymer of a polycarbonate and a polycarbonate is particularly preferably used because it is excellent in transparency, heat resistance and productivity. The polycarbonate preferably contains an aromatic polycarbonate having a fluorene skeleton structure. For example, a substance containing a repeating unit represented by the following formula (A) is mentioned.

In the above formula (A), R₁～R₈Each independently represents at least one group selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 6 carbon atoms. Examples of the hydrocarbon group include alkyl groups such as methyl, ethyl, isopropyl, and cyclohexyl, and aryl groups such as phenyl. Among them, hydrogen atom and methyl group are preferable.

X is a fluorenyl group represented by the following formula.

The repeating unit represented by the above formula (a) is preferably 1 to 99 mol%, more preferably 30 mol% or more of the total repeating units.

The aromatic polycarbonate is more preferably a copolymer and/or a mixed polymer of an aromatic polycarbonate, wherein the repeating unit a represented by the above formula (A) accounts for 30 to 90 mol% and the repeating unit B represented by the following formula (B) accounts for 70 to 10 mol% of the total.

In the above formula (B), R₉～R₁₆Independently selected from hydrogen atom, halogen atom and C1-22 alkyl. Examples of the hydrocarbon group having 1 to 22 carbon atoms include alkyl groups having 1 to 9 carbon atoms such as methyl, ethyl, isopropyl, and cyclohexyl, and aryl groups such as phenyl, biphenyl, and terphenyl. Among them, hydrogen atom and methyl group are preferable.

In the above formula (B), Y is represented by the following formula. In the formula R₁₇～R₁₉、R₂₁And R₂₂Each independently represents at least one group selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms. As the hydrocarbon group, the same groups as those described above can be mentioned. R₂₀And R₂₃Each independently selected from a hydrocarbon group having 1 to 20 carbon atoms, and the same groups as described above are exemplified for the hydrocarbon group. Ar (Ar)₁～Ar₃Each independently an aryl group having 6 to 10 carbon atoms such as a phenyl group and a naphthyl group.

The content of the above formula (a) is more preferably 35 to 85 mol%, still more preferably 45 to 80 mol% of the total repeating units.

In particular, in the above formula (A), R₁～R₈Is a hydrogen atom or a part thereof is a methyl group, and R in the above formula (B)₉～R₁₆When Y is an isopropyl group, the content of the above formula (A) is determined by the wavelength dispersion of the desired retardation. The lower limit of the content is 45 mol%, preferably 50 mol%, and more preferably 55 mol%. The upper limit is 80 mol%, preferably 75 mol%, more preferably 70 mol%. A particularly preferable range is 55 to 70 mol%.

The aromatic polycarbonate may be a copolymer in which 2 or more kinds of the repeating units represented by the above formulae (A) and (B) are combined, or a mixed polymer in which 2 or more kinds of the repeating units are combined.

The above molar ratio can be determined by, for example, a Nuclear Magnetic Resonance (NMR) apparatus using all of the polycarbonates constituting the polymer alignment film, regardless of whether the copolymer or the mixture is used.

The above aromatic polycarbonate copolymer and the mixture can be produced by a known method. As a method for producing the same, a method of polycondensing a dihydroxy compound and phosgene, a melt polycondensation method, and the like can be used. In the method for producing a mixed polymer, it is preferable to mix 2 or more types of mutually soluble polycarbonates by melt mixing or the like, and even if the components are completely immiscible, the refractive indices of the components are matched to suppress light scattering between the components, thereby improving transparency.

The intrinsic viscosity of the aromatic polycarbonate is preferably 0.3 to 2.0 dl/g. If the amount is less than 0.3, the resulting steel sheet becomes brittle and the mechanical strength is difficult to ensure; if the amount exceeds 3.0, the solution viscosity becomes too high, and there are problems such as streaks occurring during solution film formation and difficulty in purification at the completion of polymerization.

As with the retardation film a, the retardation film C of the present invention is also preferably excellent in heat resistance and preferably made of a polymer material having a glass transition temperature of 120 ℃ or higher, preferably 140 ℃ or higher. When the temperature is less than 120 ℃, problems such as orientation relaxation may occur depending on the use conditions of the display device.

The water absorption is also preferably 1 wt% or less.

The polymer material is not particularly limited, and examples thereof include thermoplastic polymers such as polyarylate, polyester, polycarbonate, polyolefin, polyether, polysulfone, and polyethersulfone.

Among them, a material having excellent heat resistance, excellent transparency, and excellent optical properties and capable of being formed into a film from a solution is preferable. Examples thereof include aromatic polycarbonates and polyolefins.

The retardation film of the present invention is preferably transparent, and preferably has a haze value of 3% or less and a total light transmittance of 85% or more.

The retardation film of the present invention may further contain an ultraviolet absorber such as phenylsalicylic acid, 2-hydroxybenzophenone, triphenyl phosphate, etc., a bluing agent for changing the color tone, an antioxidant, etc.

The method for producing the retardation in the present invention may be a known melt extrusion method, a known solution casting method, or the like. From the viewpoint of uniformity of film thickness, appearance, and the like, the solution casting method is more preferably used. Specifically, when polycarbonate is used as the polymer material, the polycarbonate is dissolved in an organic solvent such as methylene chloride or dioxolane, and an unstretched film is obtained by a solution casting method. Then, it is uniaxially or biaxially stretched by a conventional method to obtain a retardation film having a desired retardation.

Examples of the stretching method in the production of the retardation film a include a roll longitudinal uniaxial stretching method using a difference in roll speed, a tenter longitudinal uniaxial stretching method using a difference in film flow direction speed of a so-called tenter which is a fixed portion by fixing the film in the film width direction with a staple or a clip, and a continuous stretching method such as a tenter transverse uniaxial stretching method in which a tenter is stretched in the width direction.

The stretching method in the production of the retardation film C includes a sequential biaxial stretching method in which the above-mentioned uniaxial stretching method is used to stretch the retardation film C in the longitudinal and transverse directions, a simultaneous biaxial stretching method in which a tenter having a speed difference in the film flow direction is stretched in the width direction, and a multi-step stretching method in which such stretching is repeated a plurality of times.

Although there are a few examples of the continuous stretching method for obtaining the retardation film, the stretching method of the retardation film of the present invention is not limited to these, and continuous stretching is preferable from the viewpoint of productivity, but continuous stretching is not necessarily particularly used.

In the case of stretching by the methods represented by the above stretching methods, the retardation film may further contain, as a known plasticizer, a phthalate ester such as dimethyl phthalate, diethyl phthalate or dibutyl phthalate, a phosphate ester such as tributyl phosphate, an aliphatic dibasic acid ester, a glycerin derivative, an ethylene glycol derivative or the like, in order to improve the stretchability. In the stretching, the organic solvent used in the film formation may be left in the film to be stretched. The amount of the organic solvent is preferably 1 to 20% by weight based on the solid content of the polymer.

In addition to the above plasticizer, an additive such as a liquid crystal may change the dispersion of retardation wavelengths in the retardation film of the present invention. The amount of the polymer to be added is preferably 10% by weight or less, more preferably 3% by weight or less, based on the solid content of the polymer, that is, based on the weight of the polymer material constituting the retardation film.

The film thickness of the retardation film of the present invention is preferably from 1 μm to 300. mu.m. In addition, although the retardation film is described in the present invention, it may have the meaning of "film (フィルム)" or "sheet (シ - ト)".

The retardation film C may be a film obtained by orienting and fixing a liquid crystalline polymer to a substrate (stretched or unstretched film), in addition to a stretched film of a polymer material. The base material is more preferably the retardation film a from the viewpoint of film thickness.

As described above, the retardation of the retardation film a decreases as the wavelength decreases, and therefore the chemical structure of the polymer constituting the polymer alignment film is important, and the dispersion of the retardation wavelength is determined in part by the chemical structure.

A known polarizing film may be used as the polarizing film used in the present invention. For example, a film obtained by dispersing iodine, a dichroic dye, or the like in a polymer (also referred to as a binder polymer) such as polyvinyl alcohol, fixing at least iodine or the like by orientation such as stretching, and stretching a main chain type or side chain type polyacetylene can be given. In a polarizing film using polyvinyl alcohol as a binder polymer, a cellulose acetate film or the like is often laminated on the polarizing film as a protective film. Therefore, the polarizing film of the present invention includes such a polarizing film laminated with a protective film. The retardation film of the present invention may also serve as a protective film.

For the type using the above adhesive polymer, the polarizing film used is generally 30 to 300 μm in thickness. When a material having liquid crystallinity and dichroism is fixed on a substrate by coating, the thickness of the polarizing film is about 0.01 to 30 μm.

The liquid crystal display element of the present invention is constituted by combining a retardation film, a VA-type liquid crystal cell including a liquid crystal panel, and a polarizing film. The retardation film and the polarizing film are preferably adjacent, that is, in direct contact. The adhesive may be applied by using a known adhesive or bonding agent.

In addition, the liquid crystal display element of the present invention may be provided with a back light on the opposite side (back side) of the liquid crystal cell. In this case, various optical films such as a prism sheet and a diffusion film may be disposed between the liquid crystal display element and the backlight.

The liquid crystal display element of the present invention is mainly used as a liquid crystal display element such as a liquid crystal display and a liquid crystal projector. Particularly, it is very useful for a vertical alignment type liquid crystal display element requiring a wide viewing angle.

Fig. 1 to 6 show preferable structural examples in the case where the liquid crystal display element of the present invention is provided with a backlight. The liquid crystal display element of the present invention is not limited to these configurations.

Here, as shown in fig. 1 to 4, any polarizing film is preferably adjacent to the retardation film a.

In these structural examples, not only one retardation film a may be used, but a plurality of retardation films a may be stacked and used, and similarly, a plurality of retardation films C may be stacked and used as the retardation film C. In the case of laminating a plurality of retardation films, it is desirable that the direction having the maximum refractive index of the retardation films, that is, the direction toward the optical axis be aligned. In the above configuration, the backlight and the polarizer on the backlight side may be a reflection type or a transflective type such as a reflector or a transflective plate.

Preferred embodiments of the present invention are as follows.

A liquid crystal display element having a liquid crystal cell holding a VA liquid crystal sandwiched between a pair of substrates, in which the liquid crystal molecular long axis is oriented in a substantially vertical direction with respect to the substrate surfaces when no voltage is applied, further having 1 st and 2 nd polarizing films holding the liquid crystal cell and having polarizing axes orthogonal to each other, and at least 2 retardation films (A, C) present between the liquid crystal cell and the 1 st and 2 nd polarizing films,

wherein the retardation film A is a single layer and satisfies the relationship of the following formula (10) and/or (11), the retardation film C satisfies the relationship of the following formula (3) and (4-1) and/or (4-2), the retardation film A is adjacent to the 1 st polarizing film or the 2 nd polarizing film, the retardation film C is adjacent to the liquid crystal cell, the slow axis of the retardation film A is parallel to or orthogonal to the polarizing axis of the 1 st polarizing film, the retardation film A satisfies the following formula (7), the retardation film C satisfies the following formula (8) and satisfies the following formula (9), and the retardation film A comprises polycarbonate having a fluorene skeleton

0.6＜R(450)/R(550)＜0.97 (10)

1.01＜R(650)/R(550)＜1.4 (11)

n_x≥n_y＞n_z (3)

K(650)/K(550)＜1 (4-1)

1＜K(450)/K(550) (4-2)

10＜R(550)＜300 (7)

50＜K(550)＜400 (8)

R(550)＜30 (9)

Here, R, K, n_x、n_y、n_zThe definitions of (a) are the same as those described above.

Therefore, according to the present invention, it is possible to provide a VA-type liquid crystal display device which has reduced light leakage in the entire visible light range and which has a clear black display and almost no color by using the retardation film a and the retardation film C of the present invention in combination.

According to the present invention, there is provided a method of compensating a viewing angle in the entire visible light range of a liquid crystal display element, comprising a liquid crystal cell holding a liquid crystal between a pair of substrates, wherein the long axes of the liquid crystal molecules are oriented in a substantially vertical direction with respect to the substrate surfaces in the absence of an applied voltage, further comprising 1 st and 2 nd polarizing films holding the liquid crystal cell and having their polarizing axes orthogonal to each other, and at least 2 total retardation films (A, C) present between the liquid crystal cell and the 1 st and 2 nd polarizing films,

wherein the retardation film A satisfies the relationship of the following formula (1) and/or (2):

R(λ₁)/R(λ₂)＜1 (1)

K(λ₁)/K(λ₂)＜1 (2)

and the retardation film C satisfies the relationships of the following formulae (3) and (4) at the same time:

nx≥ny＞nz (3)

1＜K(λ₁)/K(λ₂) (4)

in the above formulas (1) and (2), R (lambda)₁) And R (lambda)₂) Respectively wavelength lambda₁And λ₂In-plane retardation of time retardation film, K (. lamda.)₁) And K (lambda)₁) Respectively wavelength lambda₁And λ₂Thickness direction phase difference of the phase difference film, wavelength lambda₁And λ₂Satisfies the condition that the lambda is more than 400nm₁＜λ₂The relationship of < 700nm in the wavelength range,

here, n is_xIs the maximum refractive index in the retardation film plane, n_yIs a refractive index of an azimuth perpendicular to a direction indicating a maximum refractive index in a retardation film plane, n_zRefractive index in linear direction of retardation film, K, lambda₁And λ₂The definitions of (a) are the same as above.

The method of the present invention, that is, a specific method of using the retardation film a and the retardation film C in the VA-mode liquid crystal display device, can be understood from the above description.

The present invention also provides a retardation film (viewing angle compensation film) for use as a VA-type liquid crystal display element, which comprises a combination of a retardation film A satisfying the relationship of the following formula (1) and/or (2) and a retardation film C satisfying the following formulae (3) and (4)

R(λ₁)/R(λ₂)＜1 (1)

K(λ₁)/K(λ₂)＜1 (2)

nx≥ny＞nz (3)

1＜K(λ₁)/K(λ₂) (4)

Here, R, K, λ₁、λ₂、n_x、n_y、n_zThe definitions of (a) are the same as those described above.

The use of the retardation film a and the retardation film C in the VA-mode liquid crystal display device can be understood from the above description.

Effects of the invention

As described above, by combining the retardation film a having a smaller retardation film with a shorter wavelength and the retardation film C having a larger retardation with a shorter wavelength, a VA-type liquid crystal display element having reduced light leakage in the entire visible light range, clear black display, and almost achromatic color can be provided. Thus, a wide viewing angle in the entire visible light range can be achieved.

Examples

The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

(evaluation method)

The material property values and the like described in the present specification can be obtained by the following evaluation methods.

(1) Measurement of in-plane retardation R value and thickness direction retardation K value

The in-plane retardation R value and the thickness direction retardation K value were measured using a spectroscopic ellipsometer "M150" (manufactured by Nippon spectral Co., Ltd.). The R value was measured in a state where the incident light beam and the surface of the retardation film were perpendicular to each other. Changing the angle between the incident light and the surface of the retardation film, measuring the phase difference value at each angle to obtain a K value, and performing curve fitting by using a known refractive index ellipsoid formula to obtain a three-dimensional refractive index n_x、n_y、n_z. At this timeAs another parameter, it is necessary to obtain an average refractive index n, and this value is measured by an Abbe refractometer ("Abbe refractometer 2-T" manufactured by Tokyo ァタゴ Co., Ltd.).

(2) Measurement of Water absorption

The film thickness after drying was measured in accordance with "test method for water absorption by Plastic and boiling Water absorption" described in JIS K7209, except that the film thickness after drying was 130. + -.50. mu.m. The test piece was 50mm square in size, the water temperature was 25 ℃, and the weight change was measured after immersing the sample in water for 24 hours. The unit is weight%.

(3) Measurement of glass transition temperature (Tg) of Polymer

The measurement was carried out by using "DSC 2920 Modulated DSC" (TA Instruments). The measurement was performed in the state of a sheet or a chip after the production of a polymer, not after the formation of a retardation film.

(4) Measurement of film thickness

Measured by an electron microscope manufactured by ァソリシ.

(5) Determination of the Polymer copolymerization ratio

The measurement was carried out by proton NMR using "JNM-alpha 600" (manufactured by Kokai electronic Co., Ltd.). In particular, in the case of a copolymer of bisphenol a and biscresol fluorene, the proton intensity ratio of each methyl group was determined using heavy benzene as a solvent.

(6) Polymerization of polycarbonate copolymers

The monomers used in the examples for the preparation of polycarbonates are shown below.

Aqueous sodium hydroxide solution and ion-exchanged water were added to a reaction tank equipped with a stirrer, a thermometer and a reflux cooler, monomers [ X ] and [ Y ] having the above-mentioned structures were dissolved in a molar ratio of 33: 67, and a small amount of bisulfite was added. Next, methylene chloride was added thereto, and phosgene was blown thereinto over about 60 minutes at 20 ℃. After emulsifying by adding p-tert-butylphenol, triethylamine was added and the mixture was stirred at 30 ℃ for about 3 hours to complete the reaction. After the reaction was completed, the organic phase was collected and methylene chloride was evaporated to obtain a polycarbonate copolymer. The composition ratio of the resulting copolymer was almost equal to the charged amount ratio of the monomers.

[ example 1]

The polycarbonate copolymer obtained above was dissolved in methylene chloride to obtain a cement solution having a solid content of 18% by weight. The dope solution was used to prepare a film flow on a support by a solution casting method. The fluid was peeled off from the support, slowly heated to Tg-20 ℃ and dried to obtain a film. This film was uniaxially stretched 1.6 times at 230 ℃ to obtain a retardation film A (copolymerized PC 1). The film was confirmed to have positive refractive index anisotropy, as the retardation was smaller as the measurement wavelength was shorter.

Further, ARTON manufactured by JSR corporation was dissolved in methylene chloride to obtain a cement solution having a solid concentration of 18 wt%. The resulting film was formed using the dope solution in the same manner as described above, and then biaxially stretched at 175 ℃ in a width-to-length ratio of 1.3 to obtain a retardation film C (ARTON 1). It was confirmed that the film had a larger retardation as the measurement wavelength was shorter.

Next, VA liquid crystal cells having the characteristics shown in table 1 below were prepared, and a commercially available "HLC 2-5618" manufactured by サソリシシ (ltd.) belonging to an iodine-based polarizing film was laminated with the retardation film using an adhesive, so that the structures shown in table 2 below were obtained. Even when viewed from all angles in the oblique direction of the panel, there is almost no light leakage, almost completely black, and there is no coloration even for the leaked light.

[ example 2]

Bisphenol A polycarbonate (C1400, manufactured by Nikkiso Kasei Co., Ltd.) was dissolved in methylene chloride to obtain a cement solution having a solid content of 18% by weight. Using this dope solution, a film was formed in the same manner as in example 1. This film was then biaxially stretched at 165 ℃ in the longitudinal and transverse directions by 1.1 times to obtain a retardation film C (PC 1). It was confirmed that the film had a larger retardation as the measurement wavelength was shorter.

As shown in table 2 below, the same panel structure as in example 1 was prepared except that PC1 was used instead of ARTON 1. Even when viewed from all angles in the oblique direction of the panel, there is almost no light leakage, almost completely black, and there is no coloration even for the leaked light.

TABLE 1

n(550)	1.504
		d(μm)	4
R(450)(nm)	0
		R(550)(nm)	0
R(650)(nm)	0
		K(450)(nm)	-325
K(550)(nm)	-310
		K(650)(nm)	-305

TABLE 2

Example 1	Example 2	Comparative example 1
			No. 1 polarizing film (transmission axis 90 degree)	No. 1 polarizing film (transmission axis 90 degree)	No. 1 polarizing film (transmission axis 90 degree)
Copolymerized PC1 (slow axis 90 degree)	Copolymerized PC2 (slow axis 90 degree)	ARTON2 (slow axis 90 degree)
			Liquid crystal cell	Liquid crystal cell	Liquid crystal cell
ARTON1	PC1	ARTON3
			2 nd polarizing film (transmission axis 0 degree)	2 nd polarizing film (transmission axis 0 degree)	2 nd polarizing film (transmission axis 0 degree)
Rear lighting	Rear lighting	Rear lighting

Comparative example 2

ARTON manufactured by JSR corporation was dissolved in methylene chloride to obtain a cement solution having a solid concentration of 18 wt%. A cast film was prepared using this dope solution, and then this film was uniaxially stretched 1.4 times at 175 ℃ to obtain a retardation film A (ARTON 2). Further, biaxial stretching of 1.3 times in the longitudinal and transverse directions was carried out at 175 ℃ to obtain a film (ARTON 3).

These films were used to produce the panel constructions shown in table 2. When the panel was observed from an oblique direction, light leakage was found particularly at 45 ° azimuth, and the light leakage was found to be black.

Optical characteristics of the retardation films used in examples and comparative examples are shown in table 3 below.

TABLE 3

	Copolymerized PC1	ARTON1	PC1	ARTON2	ARTON3
						n(550)	1.6240	1.5175	1.5875	1.5175	1.5175
R(450)(nm)	123	0	0	141	0
						R(550)(nm)	150	0	0	140	0
R(650)(nm)	159	0	0	140	0
						K(450)(nm)	62	222	270	71	212
K(550)(nm)	75	220	250	70	210
						K(650)(nm)	80	219	245	70	209
nx(550)	1.6250	1.5182	1.5883	1.5184	1.5182
						ny(550)	1.6235	1.5182	1.5883	1.5170	1.5182
nz(550)	1.6235	1.5160	1.5858	1.5170	1.5161
						Film thickness after stretching (mum)	90	150	80	80	150
Glass transition temperature (. degree. C.)	225	170	160	170	170
						Water absorption Rate (% by weight)	0.2	0.2	0.2	0.2	0.2

Industrial applicability of the invention

According to the present invention, by combining the retardation film a having a smaller retardation with a shorter wavelength and the retardation film C having a larger retardation with a shorter wavelength, at least 2 retardation films are used, whereby a VA-type liquid crystal display element having reduced light leakage in the entire wide band and a clear and almost achromatic black display can be provided. Such a liquid crystal display element can provide a high-quality liquid crystal display device having excellent image quality.

Claims (18)

1. A liquid crystal display element having a liquid crystal cell in which liquid crystal is sandwiched between a pair of substrates, wherein the liquid crystal molecular long axis is oriented in a substantially vertical direction with respect to the substrate surfaces when no voltage is applied, further having 1 st and 2 nd polarizing films sandwiching the liquid crystal cell and having polarizing axes orthogonal to each other, and at least 2 retardation films (A, C) in total present between the liquid crystal cell and the 1 st and 2 nd polarizing films,

characterized in that the retardation film A satisfies the relationship of the following formula (1) and/or (2):

R(λ₁)/R(λ₂)＜1 (1)

K(λ₁)/K(λ₂)＜1 (2)

in the above formulas (1) and (2), R (lambda)₁) And R (lambda)₂) Respectively wavelength lambda₁And λ₂In-plane retardation of time retardation film, K (. lamda.)₁) And K (lambda)₁) Respectively wavelength lambda₁And λ₂Thickness direction phase difference of the phase difference film, wavelength lambda₁And λ₂Satisfies the condition that the lambda is more than 400nm₁＜λ₂The relationship of < 700nm in the wavelength range,

and the retardation film C satisfies the relationships of the following formulae (3) and (4) at the same time:

n_x≥n_y＞n_z (3)

1＜K(λ₁)/K(λ₂) (4)

here, n is_xIs the maximum refractive index in the retardation film plane, n_yIs a refractive index of an azimuth perpendicular to a direction indicating a maximum refractive index in a retardation film plane, n_zRefractive index in linear direction of retardation film, K, lambda₁And λ₂The definitions of (a) are the same as above.

2. The liquid crystal display element according to claim 1, wherein the phase difference film a is adjacent to the 1 st or 2 nd polarizing film.

3. The liquid crystal display element according to claim 1, wherein the retardation film C is adjacent to the liquid crystal cell.

4. The liquid crystal display element according to claim 1, wherein the slow axis of the phase difference film a is parallel to or orthogonal to the polarizing axis of the polarizing film.

5. The liquid crystal display element according to claim 1, wherein in the above formulae (1) and (2), λ₁At a wavelength of 450nm, lambda₂The wavelength is 550 nm.

6. The liquid crystal display element according to claim 1, wherein the retardation film A satisfies the following formula (5) and/or (6)

1＜R(650)/R(550) (5)

1＜K(650)/K(550) (6)

Wherein R (650) and R (550) are in-plane retardation of the retardation film at wavelengths of 650nm and 550nm, respectively, and K (650) and K (550) are in-thickness retardation of the retardation film at wavelengths of 650nm and 550nm, respectively.

7. The liquid crystal display element according to claim 1, wherein the retardation film C satisfies the following formula (4-1)

K(650)/K(550)＜1 (4-1)

Wherein R and K are as defined above.

8. The liquid crystal display element according to claim 1, wherein the retardation film A satisfies the following formula (7) and the retardation film C satisfies the following formula (8)

10＜R(550)＜300 (7)

50＜K(550)＜400 (8)

Wherein R and K are as defined above.

9. The liquid crystal display element according to claim 1, wherein each of the retardation films a and C is obtained from a polymer material having a water absorption of 1 wt% or less.

10. The liquid crystal display element according to claim 1, wherein the retardation film a is a single layer.

11. The liquid crystal display element according to claim 1, wherein the retardation film a is composed of a polymer alignment film composed of a polymer monomer unit having positive refractive index anisotropy and a polymer monomer unit having negative refractive index anisotropy.

12. The liquid crystal display element according to claim 11, wherein the retardation film a is formed of a substance containing a polycarbonate having a fluorene skeleton.

13. The liquid crystal display element according to claim 1, wherein the retardation film C satisfies the following formula (9)

R(550)＜30 (9)

Wherein R is as defined above.

14. The liquid crystal display element according to claim 1, wherein when the 1 st and 2 nd polarizing films are each composed of a polarizing element having protective layers on both sides, the sum total of the phase differences in the thickness direction at a wavelength of 550nm of one of the protective layers, the phase difference films a and C, and the liquid crystal cell is-200 to 200 nm.

15. A liquid crystal display element having a liquid crystal cell in which liquid crystal is sandwiched between a pair of substrates, wherein the long axes of the liquid crystal molecules are oriented in a substantially vertical direction with respect to the substrate surfaces when no voltage is applied, further having 1 st and 2 nd polarizing films sandwiching the liquid crystal cell and having their polarizing axes orthogonal to each other, and at least 2 retardation films (A, C) present between the liquid crystal cell and the polarizing films,

wherein the retardation film A is a single layer and satisfies the relationship of the following formula (10) and/or (11), the retardation film C satisfies the relationship of the following formula (3) and { (4-1) and/or (4-2) } at the same time, the retardation film A is adjacent to the 1 st polarizing film or the 2 nd polarizing film, the retardation film C is adjacent to the liquid crystal mesogen, the slow axis of the retardation film A is parallel to or orthogonal to the polarizing axis of the 1 st polarizing film, the retardation film A satisfies the following formula (7) and the retardation film C satisfies the following formula (8) and the following formula (9), and the retardation film A is composed of a substance containing a polycarbonate having a fluorene skeleton,

0.6＜R(450)/R(550)＜0.97 (10)

1.01＜R(650)/R(550)＜1.4 (11)

n_x≥n_y＞n_z (3)

K(650)/K(550)＜1 (4-1)

1＜K(450)/K(550) (4-2)

10＜R(550)＜300 (7)

50＜K(550)＜400 (8)

R(550)＜30 (9)

in the formula, R, K, n_x、n_y、n_zAs defined above, R (450) is an in-plane retardation of the retardation film at 550nm, and R (550) is a thickness-direction retardation at 450 nm.

16. A liquid crystal display element having a liquid crystal cell in which liquid crystal is sandwiched between a pair of substrates, wherein the long axes of the liquid crystal molecules are oriented in a substantially vertical direction with respect to the substrate surfaces when no voltage is applied, further having 1 st and 2 nd polarizing films sandwiching the liquid crystal cell and having their polarizing axes orthogonal to each other, and at least 2 retardation films (A, C) present between the liquid crystal cell and the polarizing films,

wherein, in the wavelength range of 400-700 nm, the retardation in the film surface and/or thickness direction is basically larger as the wavelength is shorter for the retardation film A, and the retardation in the thickness direction is basically smaller as the wavelength is shorter for the retardation film C, and the following formula (3) is satisfied

n_x≥n_y＞n_z (3)

In the formula, n_x、n_y、n_zThe definitions of (a) are the same as those described above.

17. A method for compensating the viewing angle of the entire visible light range of a liquid crystal display element by having a liquid crystal cell holding a liquid crystal between a pair of substrates, wherein the long axes of the liquid crystal molecules are oriented in a substantially vertical direction with respect to the substrate surfaces when no voltage is applied, further having 1 st and 2 nd polarizing films holding the liquid crystal cell and having their polarizing axes orthogonal to each other, and at least 2 total sheets of retardation films (A, C) present between the liquid crystal cell and the 1 st and 2 nd polarizing films,

wherein the retardation film A satisfies the relationship of the following formula (1) and/or (2):

R(λ₁)/R(λ₂)＜1 (1)

K(λ₁)/K(λ₂)＜1 (2)

in the above formulas (1) and (2), R (lambda)₁) And R (lambda)₂) Respectively wavelength lambda₁And λ₂In-plane retardation of time retardation film, K (. lamda.)₁) And K (lambda)₁) Respectively wavelength lambda₁And λ₂Thickness direction phase difference of the phase difference film, wavelength lambda₁And λ₂Satisfies the condition that the lambda is more than 400nm₁＜λ₂The relationship of < 700nm in the wavelength range,

and the retardation film C satisfies the relationships of the following formulae (3) and (4) at the same time:

n_x≥n_y＞n_z (3)

1＜K(λ₁)/K(λ₂) (4)

in the formula, n_xIs the maximum refractive index in the retardation film plane, n_yN is a refractive index of an azimuth perpendicular to a direction indicating a maximum refractive index in the retardation film plane_zRefractive index in linear direction of retardation film, K, lambda₁And λ₂The definitions of (a) are the same as above.

18. The use of a retardation film A satisfying the following expression (1) and/or (2) in combination with a retardation film C satisfying the following expression (3) and (4) as a viewing angle compensation film for a VA-type liquid crystal display device,

R(λ₁)/R(λ₂)＜1 (1)

K(λ₁)/K(λ₂)＜1 (2)

n_x≥n_y＞n_z (3)

1＜K(λ₁)/K(λ₂) (4)

wherein, R, K, λ₁、λ₂、n_x、n_y、n_zThe definitions of (a) are the same as those described above.