KR101388366B1 - Transparent film, polarizing plate, and liquid crystal dispaly device - Google Patents

Abstract

assignment

The novel transparent film which contributes to the reduction of both wavelength dependence and viewing angle dependence is provided.

Solution

In the normal direction of a film surface, it is a transparent film which contains the area | region whose Nz value monotonically increases or monotonically decreases to 0-1, and whose in-plane retardation Re is 510-610 nm.

However, Nz = 0.5 + Rth (550) / Re (550), where Rth (550) and Re (550) are retardation and in-plane retardation of the thickness direction in wavelength 550nm, respectively.

Film side, normal direction, forging increase, forging decrease, in-plane retardation

Description

Transparent film, polarizing plate, and liquid crystal display device {TRANSPARENT FILM, POLARIZING PLATE, AND LIQUID CRYSTAL DISPALY DEVICE}

This invention relates to the novel transparent film used as an optical compensation film of a liquid crystal display device, the protective film of a polarizing plate, etc., and a polarizing plate and a liquid crystal display device using this transparent film.

A transmissive liquid crystal display device has a liquid crystal cell and a pair of polarizers on both sides. This pair of polarizers is generally arranged as a so-called orthogonal polarizer with the transmission axes of each being orthogonal to each other. However, the orthogonal polarizer can function as an orthogonal polarizer with respect to the incident light in the normal direction with respect to the surface thereof, but for the incident light from the inclined direction inclined from the normal direction, the cross angle of the transmission axis is shifted from the right angle so that it functions as the orthogonal polarizer. Can not. This causes light leakage in the oblique direction in the transmissive liquid crystal display device, and causes a decrease in viewing angle characteristics such as a decrease in contrast and color taste change depending on the viewing angle.

By the way, the polarizer which consists of a polyvinyl alcohol film etc. is not used as a single member in a liquid crystal display device, but is mounted in a liquid crystal display device as a polarizing plate with a protective film which protects a polarizer on both surfaces. Therefore, wide viewing angle is attempted by giving a predetermined optical characteristic to such a protective film. As an example, "the wide viewing angle polarizing plate which superimposes a biaxial retardation plate which has birefringence characteristics into which a polarizer becomes in-plane phase difference = 250-300 nm and Nz = 0.1-0.4", and "in-plane phase difference = 250-300 The wide viewing angle polarizing plate which overlaps the biaxial retardation plate which has birefringence characteristic set to nm, Nz = 0.6-1.1 "is proposed (patent document 1). In the Example of patent document 1, the wide viewing angle is shown with respect to the transmissive liquid crystal display device which arrange | positioned such two wide viewing angle polarizing plates in the orthogonal arrangement on both sides of a liquid crystal cell.

In the wide viewing angle technology of the polarizing plate of patent document 1, it is necessary to pass incident light through the biaxial retardation plate which has said predetermined birefringence twice. Therefore, it is preferable from a viewpoint of productivity, such as the limitation of the design of a liquid crystal display device, or the complicated process of laminating | stacking two retardation plates of predetermined optical characteristics by precisely controlling the positional relationship of each optical axis, is needed. Not.

On the other hand, there is an attempt to compensate for the viewing angle dependency of the polarizer only by passing incident light through one retardation plate. In this case, the problem of wavelength dependence arises. This is attributable to the retardation of a triacetyl acetate film or the like commonly used as a protective film for a polarizing plate showing wavelength dependency. For example, even if the optical characteristic of a protective film is adjusted so that it may convert into an extinction point by passing a protective film, the incident light of wavelength 550 nm (G) which is the center of the visible light wavelength range 400-700 nm, 450 Incident light of nm (B) and 650 nm (R) is converted into a polarization state shifted from the extinction point, and as a result, color taste change and a decrease in contrast depending on the viewing angle are generated.

[Patent Document 1] Japanese Unexamined Patent Publication No. 2001-350022

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a novel polarizing plate having a broadband and wide viewing angle capable of coping with all visible wide areas in which the above problems are solved.

Moreover, this invention makes it a subject to provide the novel transparent film which contributes to the reduction of both wavelength dependency and viewing angle dependence as a protective film of such a polarizing plate, and as an optical compensation film of a liquid crystal display device.

Moreover, this invention makes it a subject to provide the liquid crystal display device with a favorable viewing angle characteristic by which the fall of contrast and color taste change which were dependent on viewing angle were reduced.

Means for solving the above problems are as follows.

[1] A transparent film having a region in which the Nz value is monotonically increased or monotonically decreased to 0 to 1 in the normal direction of the film surface, and whose in-plane retardation Re at a wavelength of 550 nm is 510 to 610 nm.

However, Nz = 0.5 + Rth (550) / Re (550), where Rth (550) and Re (550) are retardation and in-plane retardation of the thickness direction in wavelength 550nm, respectively.

[2] The transparent film of [1], containing cellulose acylate as a main component.

[3] The transparent film of [1], containing an alicyclic structure-containing polymer resin as a main component.

[4] In-plane optical anisotropy, circular retardance (CRE1) in the normal direction of the film plane is approximately 0, polar angle is 60 degrees from the normal direction of the film plane, and the slow axis in the film plane is 0 degree angle. When the azimuth angle is 45 degrees, 135 degrees, 225 degrees, and 315 degrees, the absolute value of the circular retardance (CRE2) in the light incident in four directions is approximately equal, and is not zero.

[5] The transparent film of [4], wherein the absolute value of the CRE2 is from 32 to 38 nm.

[6] The transparent film of [1], having a multilayer structure composed of two or more layers having different Nz values from each other.

[7] The transparent film of [6], which has at least one layer of a polymer film and an optically anisotropic layer composed of the same or different liquid crystal compositions on both surfaces thereof.

[8] A polarizing plate having a polarizing film and the transparent film of any of [1] to [7].

[9] A liquid crystal display device having a liquid crystal cell and a polarizing plate of [8].

[10] A liquid crystal display device having a liquid crystal cell and at least one polarizing film, wherein the liquid crystal display device has a transparent film according to any one of [1] to [7] between the polarizing film and the liquid crystal cell.

According to the present invention, it is possible to provide a novel polarizing plate having a wide bandwidth and a wide viewing angle. Moreover, according to this invention, as a protective film of such a polarizing plate and as an optical compensation film of a liquid crystal display device, the novel transparent film which contributes to reduction of both wavelength dependence and viewing angle dependence can be provided. Moreover, according to this invention, the liquid crystal display device with a favorable viewing angle characteristic in which the fall of contrast and color taste change which were dependent on viewing angle can be reduced can be provided.

Hereinafter, the present invention will be described in detail. In addition, it is used by the meaning which includes with "-" the numerical value described before and after that as a lower limit and an upper limit in this specification. In addition, substantially orthogonal or parallel means the range of rigid angle +/- 10 degrees.

In addition, in this specification, Re ((lambda)) and Rth ((lambda)) represent the in-plane retardation in the wavelength (lambda), and the retardation of the thickness direction, respectively. Re ((lambda)) is measured by injecting light of wavelength (lambda) nm in a film normal line direction in KOBRA 21ADH or WR (Oji Measurement Instruments Co., Ltd. product).

When the film to be measured is represented by the refractive index ellipsoid of one axis or two axes, Rth (λ) is calculated by the following method.

Rth (λ) is the rotation axis of any direction in the film plane, where Re (λ) is the in-plane slow axis (determined by KOBRA 21ADH or WR) as the inclination axis (rotation axis). 6 points are measured by injecting light having a wavelength of λ nm from the inclined direction in 10 degree steps from the normal direction to 50 degrees on one side with respect to the film normal direction, and measuring all 6 points of the measured retardation value and the average refractive index. And KOBRA 21ADH or WR is calculated based on the input film thickness value.

In the above description, in the case of a film having an in-plane slow axis as the rotation axis from the normal direction and having a direction in which the value of the retardation becomes zero at any inclination angle, the retardation value at an inclination angle greater than the inclination angle is indicated by the reference. After changing to negative, KOBRA 21ADH or WR is calculated.

In addition, the slow axis is set as the inclination axis (rotation axis) (when there is no ground axis, any direction in the film plane is used as the rotation axis), and the retardation value is measured from two inclined directions, and the value and the average refractive index Rth can also be calculated from the following equations (21) and (22) based on the hypothesis value and the input film thickness value.

In said formula, said Re ((theta)) shows the retardation value in the direction which inclined angle (theta) from a normal line direction.

In formula, nx represents the refractive index of the slow-axis direction in surface inside, ny represents the refractive index of the direction orthogonal to nx in surface, nz represents the refractive index of the direction orthogonal to nx and ny, and d is The film thickness is shown.

In the case where the film to be measured cannot be expressed by one or two refractive index ellipsoids, or a so-called optical axis-free film, Rth (λ) is calculated by the following method.

Rth (λ) is the Re (λ) in the in-plane slow axis (determined by KOBRA 21ADH or WR) in the inclination axis (rotation axis) in the step of 10 degrees from -50 degrees to +50 degrees with respect to the film normal direction, respectively. 11 points of light are measured by injecting light having a wavelength of λ nm from the inclined direction, and KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumption value of the average refractive index, and the input film thickness value.

In the above measurement, the assumption value of the average refractive index can use the polymer handbook (JOHN WILEY & SONS, INC) and the value of the catalog of various optical films. The thing with which the value of an average refractive index is not known can be measured with an Abbe refractometer. The value of the average refractive index of a main optical film is illustrated below:

Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49) and polystyrene (1.59). By inputting the assumption values and film thicknesses of these average refractive indices, KOBRA 21ADH or WR calculates nx, ny, and nz. From the calculated nx, ny, and nz, Nz = (nx-nz) / (nx-ny) is further calculated.

In addition, in this specification, the numerical value or numerical range which shows an optical characteristic etc. shall be interpreted as the numerical value or numerical range containing the error generally allowable with respect to a liquid crystal display device or the member used for it.

The present invention relates to a transparent film having a region in which the Nz value is monotonically increased or monotonically decreased to 0 to 1 in the normal direction of the film surface, and that the in-plane retardation Re at a wavelength of 550 nm is 510 to 61O nm. will be. The transparent film of this invention is combined with a polarizer and arrange | positioned between a polarizer and a liquid crystal cell, and contributes to the fall of contrast in the inclination direction of a liquid crystal display device, and reduction of a color taste change. In addition, regarding "the area | region where a Nz value monotonically increases or monotonically decreases to 0-1 in the normal direction (film thickness direction) of a film surface," it mentions in a document: Y.Takahashi, H. Watanabe and T. Kato, “Depth-Dependent Determination of Molecular Orientation for WV-Film”, IDW′04 (2004) p.651. Specifically, the value of Nz determined by measuring the x, y and z components of P2 equally in five points in the thickness direction of the film, and using the calculated nx, ny and nz changes in the range of 0 to 1. This means that, for example, the Nz value is changed to approximately 0, 0.25, 0.5, 0.75, 1 for each of the five points. Moreover, about the "forging increase and decrease in forging" of Nz of the film, the increase rate and decrease rate may fluctuate and there may be a range which does not increase or decrease, but there is no range which decreases at least for forging increase, and at least for decrease in forging There is no increasing range. Preferably, the monotonous increase is constant, or the monotonic decrease is constant.

As one aspect of the transparent film of this invention, the transparent film which has a multilayered structure which consists of two or more layers from which Nz values differ from each other is mentioned. More specifically, it has a polymer film and at least 1 layer of optically anisotropic layers which consist of the same or different liquid crystal composition, respectively, on both surfaces, Nz of one optically anisotropic layer is 0, Nz of a polymer film is 0.5, and the other optically anisotropic layer. The transparent film whose Nz is 1.0 is also one aspect of this invention. When a plurality of optically anisotropic layers having different Nz are formed on one surface of the polymer film, and / or the polymer film being supported, respectively, and Nz is a multilayer structure of a polymer film having different Nz ratios, Nz is 0 to 1 It is possible to produce a transparent film having a monotone increase (or monotone decrease) at a small change rate in the range.

An example of the polarizing plate which has a transparent film of this invention is shown in FIG. The polarizing plate 10 of FIG. 1 has the polarizer 12 which consists of a polyvinyl alcohol (PVA) film etc. which were dyed by iodine etc., and the protective films 14 and 16 which consist of a cellulose acylate film etc. on the surface. The protective film 16 is a transparent film of the present invention and satisfies the predetermined optical characteristics. When attaching the polarizing plate 10 to the liquid crystal display device, the absorption axes of the polarizing plates are orthogonal to each other, with the liquid crystal cell interposed between the other polarizing plate and the protective film 16 which is the transparent film of the present invention as the liquid crystal cell side. It is arranged as.

In addition, the transparent film of this invention does not necessarily need to adhere directly to the surface of a polarizer as a protective film of a polarizer. For example, you may arrange | position the transparent film of this invention between a polarizer and a liquid crystal cell as an optical compensation film. When the protective film of a polarizer is arrange | positioned between a polarizer and the transparent film of this invention, it is preferable that this protective film is an isotropic film without retardation.

Next, with reference to drawings, the effect | action of the transparent film and polarizing plate of this invention is demonstrated. 2-5 are the figures which looked at the poincare sphere from the positive direction of the S2 axis, respectively. The Poincare sphere is a three-dimensional map describing the polarization state, and the equator phase of the sphere represents the polarization state of linearly polarized light with an ellipticity of zero. The point P in FIG. 2 has shown the polarization state in which the light incident from the diagonal direction passed through the polarizer and became linearly polarized light. When the polarization state point P is converted into the polarization state point Q which is the extinction point on the S1 axis, the viewing angle dependency of the orthogonal polarizer is resolved. Therefore, what is necessary is just to adjust the birefringence of a protective film so that a polarization state may be converted from the point P to the point Q by passing the protective film arrange | positioned at the liquid crystal cell side of a polarizer. The change in polarization state due to passing through the retardation region is indicated on the Poincare sphere by rotating a certain angle around a particular axis determined in accordance with the optical properties. As an example of the conversion from the polarization state point P to the polarization state point Q, as shown in FIG. 3, there exists a conversion by rotating by π using a 1/2 wave plate as a protective film, and making S2 axis into a rotation axis. Moreover, the rotation angle is proportional to the phase difference of the phase difference area which passed, and also to the inverse of the wavelength of the incident light.

By the way, since many of the films used as protective films, such as a cellulose acylate film, do not have the same refractive index with respect to the wavelength of incident light, and there exists a tendency to become small normally as it becomes long wavelength, As a result, incident light also changes with respect to a phase difference. Longer wavelengths have a smaller wavelength dependency. In addition to the influence of the wavelength dependence of the refractive index, as described above, since the rotation angle is proportional to the inverse of λ, the transition angle of the polarization state displayed on the Poincare sphere becomes smaller as the long wavelength of light. Therefore, it is difficult to perform conversion of the polarization state shown in FIG. 3 also about any of R light (650 nm), G light (550 nm), and B light (450 nm) with one retardation plate. For example, even if it uses the protective film which enables conversion to a quenching point with respect to G light (550 nm) of a center wavelength, as shown in FIG. 4, about R light and B light from the quenching point Misalignment occurs.

Therefore, in the present invention, the wavelength dependence is reduced by converting the polarization state using the optical optical property together with the birefringence of the film, not the conversion of the polarization state using only the birefringence of the film as shown in FIG. 3. . The transparent film of this invention includes the area | region whose Nz value monotonically increases or monotonically decreases to 0-1 in the normal line direction of a film surface. Such a region is, for example, a laminate in which an extremely small film thickness layer is laminated by an infinite number, and can be approximated as a laminate in which Nz is increased or decreased by an extremely small layer between adjacent layers. Incidence side outermost surface and the Nz = 0 of the outermost surface layer of Nz = 1, the exit side of the, represents the conversion of the polarization state of the light incident on the virtual stack body, first linearly polarized light in the first layer L _{Nz =} o is the The birefringence of the layer is affected, and the trajectory of the transformation at that time is expressed as a rotation having an axis parallel to the S2 axis at the point P as the rotation axis. In the second layer, Nz decreases slightly, so that the rotation axis becomes an axis parallel to the S2 axis at the point slightly shifted from the point P in the direction of S1 = 0 on the S1 axis. 3rd, 4th layer... As this, Nz is reduced and the rotational axis is moved in the direction of S1 = 0, and is the axis of rotation axis S2 is in the layers of _{Nz = 0.5 L Nz = 0. 5} . Finally, at the outermost surface layer L _{Nz = 1} on the emission side, the rotation axis is an axis parallel to the S2 axis at the extinction point Q.

The trajectory of the transformation of the polarization state therebetween is approximated as ΔNz → 0 with respect to the increase and decrease ΔNz of Nz between adjacent layers, as shown in FIG. 5. As for the locus of the conversion of the polarization state shown in FIG. 5, the rolling cone which shows what is called linearity shown by the broken line in FIG. 5 moves the center further in the negative direction from the point P on the S1-axis to S1 = 0. It follows the same trajectory as turning one turn to the extinction point Q. The wavelength dispersion of the refractive index also affects the rotation of the rolling cone exhibiting the opticality, but compared with the rotation using only the birefringence shown in FIG. 4, the R light, the G light, and the B when the polarization state reaches the extinction point Q Separation of light becomes small, which can reduce wavelength dispersion. In addition, Re (total of in-plane retardation) of a transparent film is a movement on a Poincare sphere, and is required in order to rotate a rolling cone 360 degree | times, and needs about 560 nm. In fact, it is effective against the conventional example in the range of 510-610 nm.

When the transparent film of this invention is expressed from another viewpoint, it does not generate linearity with respect to incident light of the normal direction of a film, but can be expressed as a film which produces linearity with respect to incident light of a diagonal direction. More specifically, from another viewpoint, the transparent film of the present invention has a circular retardance (CRE1) of 0 measured for light incident from the normal direction of the film plane, and from a plurality of inclined directions different from each other with respect to the film plane. The absolute value of CRE2 measured with respect to the incident light is approximately equal, and it can be expressed by the transparent film characterized by being non-zero. Here, the plurality of inclined directions different from each other with respect to the film plane are, for example, a polar angle of 60 degrees from the normal direction of the film plane, and an azimuth angle of 45 degrees, 135 degrees, 225 degrees when the slow axis in the film surface is 0 degrees. And 315 degrees in four directions. Here, the fact that the absolute values of CRE2 when incident from these four directions are approximately equal cannot be satisfied with a film in which the slow axis direction is simply twisted, and such a film and the transparent film of the present invention are clearly different. In the transparent film of the present invention, Nz has a different distribution in the thickness direction, and as a result, when the slow axis in the film plane is 0 degrees, the azimuth angle is 45 degrees, 135 degrees, 225 degrees, and 315 degrees in four directions. Although different, the absolute value is the same. It is preferable that the absolute value of CRE2 with respect to the light incident from the said four directions is 32-38 nm, respectively. In addition, approximately equal shall mean that it is completely the same or the difference of a value is 5 nm or less.

CRE (CRE1 and CRE2) of the film can be measured, for example, by the Mullermatrix polarimeter "AxoScan" from Axometrics. In addition, for details of the CRE, S. Y. Lu and R. A. Chipman, J. Opt Soc. Am A. 13 (1996) 1106.

There is no restriction | limiting in particular about the raw material of the transparent film of this invention. For example, an extending | stretching birefringent polymer film may be sufficient, and the optically anisotropic layer formed by fixing a liquid crystalline compound to a specific orientation state may be sufficient. In addition, the transparent film is not limited to the single layer structure, but may have a multilayer structure in which a plurality of layers are laminated. In the aspect of a multilayered structure, the material of each layer may be the same or different types. For example, the laminated body of the optically anisotropic layer which consists of a polymer film and a liquid crystal composition may be sufficient. In the aspect of a multilayered structure, when the thickness is considered, the multilayered body which consists of a coating-type layer containing the layer formed by application | coating rather than the laminated body of the polymeric stretched film is preferable.

By selecting the raw material to be used, its compounding quantity, manufacturing conditions, etc., and adjusting these values to a desired range, Nz value can be manufactured as a transparent film which satisfy | fills the said conditions. Specifically, two or more kinds of polymers having different wavelength dispersions (for example, plural kinds of polymers having different absorption wavelengths in the main chain direction) are mixed; Additives with absorption in the ultraviolet or infrared region are added to control wavelength dispersion of visible light; Additives with absorption in the ultraviolet or infrared range, which are structurally oriented in the thickness direction, the stretching direction or the non-stretching direction of the film, are added in the film: multilayers of the polymer layer by application or adhesion (for example, to each other) A multilayer body of a polymer layer having different birefringence); Orientation or uniformity of a material is controlled by giving a nonuniform temperature distribution or intensity distribution of an ultraviolet-ray in a thickness direction in a film manufacturing process; Etc., the transparent film of the present invention can be produced. There is no restriction | limiting in particular as a material used for manufacture of the transparent film of this invention, It is preferable to use a cellulose acylate and an alicyclic structure containing polymer resin (norbornene type polymer etc.) as a main component.

Moreover, this invention relates also to the polarizing plate which has the transparent film of this invention. It is preferable that the polarizing plate of this invention is one protective film of a polarizer, ie, the transparent film of this invention is affixed in contact with the surface of a polarizer. When attaching the polarizing plate of this invention to a liquid crystal display device, it is preferable to arrange | position the transparent film of this invention to a liquid crystal cell side.

The characteristics of the polarizing plate can be described as a dittenuation vector D or a polarizance vector P.

The dichroism (diagnosis) vector D indicates the polarization state in which the amount of transmitted light is the maximum on the Poincare sphere, and the polarization ability (polarization) vector P is the emission when the polarized light is incident on the Poincare sphere. The polarization state is shown. It is a vector represented by a dichroic vector D = (Dh, D45, Dr) and a polarization power vector P = (Ph, P45, Pr). It is preferable to use a dual rotator retarder type polarization meter as the measuring instrument because D and P of the laminate of the polarizing film and the birefringent polymer film can be measured. The dual rotate retarder type polarization meter includes a polarization generator in which the measurement head generates polarization and a polarization analyzer for detecting polarization, and is composed of a wave plate and a polarizer in which both heads rotate at high speed. As a commercial item, there is a Mullermatrix polarimeter by Axometrics, which can be used.

In addition, the normalized dichroic vector D '= (Dh', D45 ', Dr') and the normalized polarization power vector P '= ( Ph ', P45', Pr '). These details are described in Y. Ootani: O plus E 29p.20 (2007) and S-Y. Lu and R. A. Chipman: J. Opt. Soc. Am. A 13p. 1106 (1996).

When the characteristic is described by P ', the polarizing plate of this invention is a wide viewing angle polarizing plate in which the absolute value | P45' | of P45 'of a polarizing plate shows 0.9 or more, Preferably it is about 0.99 or more.

The transparent film or polarizing plate of this invention can be used for the liquid crystal display device of various modes. For example, it can be used for the liquid crystal display of various modes, such as an IPS mode, VA mode, TN mode, and OCB mode.

About the some examples of the transparent film of this invention, the result which confirmed the effect actually is shown in the following table | surfaces.

A comparative example is a film which Nz value is uniform at 0.5 in the thickness direction of a film, and is an example shown in order to compare with this invention. All of Examples 1-6 are films in which Nz value changes to 0-1 in a thickness direction, and it is an example of the transparent film of this invention in which in-plane retardation Re satisfies 510-610 nm. In addition, in Examples 1-6, CRE1 is 0 and CRE2 measured with respect to the light which entered in four directions is not 0, and it can understand from the value in a table | surface that it is the same.

As for Examples 1-6, it is understood that the transmittance | permeability (%) of a black state is low compared with a comparative example, and contrast is improved.

Similarly, when the polarizing film is laminated on the transparent film, that is, in the form of a polarizing plate, when the polar angle is 60 degrees from the normal direction of the film surface and the slow axis in the film surface is 0 degrees, the azimuth angle enters the normal in the direction of 45 degrees, and The transparent film was positioned on the emission side of the polarizing film, and standardized polarization performance vectors P '= (Ph', P45 ', Pr') were measured. Since P 'is a unit vector, considering that the maximum value of the magnitude | size of a vector is 1, it can be understood that the absolute value | P45' | of P45 'of the polarizing plates of Examples 1-6 is 0.99 or more from 1 from the following table.

Example

Next, the Example which manufactured the transparent film and the polarizing plate each as actually described below and used for the liquid crystal display device of an IPS mode is demonstrated about the Example which confirmed the effect. However, the present invention is not limited to the following examples.

Comparative Example 1

<Production of Film 1>

A polyester film having a dimensional change rate (MD / TD) of 1.15 at 165 degrees was bonded to both sides of a polycarbonate having a length of 100 m, a width of 180 mm, a thickness of 110 μm, and Re of 0 nm through an acrylic adhesive layer, and a roll The film was shrunk by treatment with a stretching machine under conditions of a roll speed ratio of 0.97 and at room temperature in which the temperature of the roll was 165 degrees, and then the polyester film was peeled off. This film was extended | stretched 1.1 times in the width direction in the atmosphere of the temperature of 163 degree, and the film 1 was obtained.

As a result of measuring the optical incidence angle dependence of Re using an automatic birefringence meter (K0BRA-21ADH, manufactured by Oji Instrument Co., Ltd.) and calculating their optical characteristics, Re is 275 nm and Nz is 0.5. It was confirmed that the slow axis was in a direction perpendicular to the longitudinal direction. CR1 and all azimuth angles were measured for the film 1 by using AxoScan from Axometrics, measuring CR1 at the front at a wavelength of 550 nm, polar angle of 60 degrees, and CR2 at 45, 135, 225 and 315 degrees of azimuth angle. All CR2 in was 0 nm.

<Production of Polarizing Plate 1 for Comparative Example>

A roll-shaped polyvinyl alcohol film having a thickness of 80 µm was continuously stretched five times in an aqueous solution of iodine and dried to obtain a polarizing film. Kurere PVA-117H was used for polyvinyl alcohol. Film 1 for a comparative example was attached to the single side | surface of this polarizing film, and the tack film TD80U by a Fujifilm company was laminated | stacked on the other side as a protective film, and the polarizing plate 1 for a comparative example was manufactured.

The standardized polarization performance vector P 'of the polarizing plate 1 for this comparative example was measured by Axoscan. Standardized polarized light, which was measured at a polar angle of 60 degrees from the normal direction of the film plane and an azimuth angle of 45 degrees when the slow axis in the film plane was set to 0 degrees of azimuth, and was placed by placing the film 1 for comparative example on the exit side of the polarizing film. The absolute value of the component P45 'of the twill vector P' was 0.994.

Example 1

<Production of Transparent Film 10>

The optically anisotropic layer 1 was formed on the single side | surface of the film 1 manufactured by the comparative example 1, and the optically anisotropic layer 2 was formed on the other side by the following method, and the transparent film 10 of the Example of this invention was manufactured.

<Formation of Optically Anisotropic Layer 1 Made of Rod-shaped Liquid Crystal Composition>

(Formation of alignment film)

The alignment film coating liquid of the following compositions was prepared.

4 parts by mass of the following polymer compound P

2 parts by mass of triethylamine

5% aqueous solution of Deconar EX-521

(Epoxy compound of Nagase Chemical Co., Ltd.) 8.1 parts by mass

57 parts by mass of water

29 parts by mass of methanol

This oriented film coating liquid was apply | coated to the single side | surface of the film 1, and it dried for 120 second by the warm air of 120 degreeC for 30 second at 25 degreeC. The thickness of the oriented film after drying was 1.5 micrometers. Next, the rubbing process was performed to the formed film in the same direction as the longitudinal direction of the transparent film 1.

(Formation of Optically Anisotropic Layer 1)

The coating liquid for optically anisotropic layers of the following composition was prepared.

38.1 mass% of following rod-like liquid crystalline compounds (example compound IV-2)

0.38 mass% of the following sensitizers A

1.14 mass% of following photoinitiators B

0.19 mass% of following orientation control agents C

Glutaraldehyde 0.04 mass%

Methyl ethyl ketone 60.15 mass%

On the rubbing process surface of the formed alignment film, the prepared coating liquid for optically anisotropic layer was continuously apply | coated, dried, and heated (orientation aging) using a bar coater, and further ultraviolet irradiation was carried out, and rod-shaped liquid crystalline molecules were horizontally aligned. And an optically anisotropic layer 1 (thickness: 1.1 mu m) was formed.

The formed optically anisotropic layer 1 was transferred to a glass substrate, and the birefringence characteristics were measured. As a result, the Nz value was 1 and the Re value was 143 nm. The slow axis was a direction orthogonal to the longitudinal direction (rubbing direction) of the film.

<Formation of Optically Anisotropic Layer 2 Made of a Discotic Liquid Crystal Composition>

(Formation of alignment film)

20 ml / m <2> was apply | coated to the other single side | surface of the film 1 with the orientation film application liquid of the following composition with the wire bar coater. The film | membrane was formed by drying for 60 second by the warm air of 60 degreeC, and 120 second by the warm air of 100 degreeC. Next, the formed film was rubbed in a direction parallel to the slow axis direction of the film 1 to form an alignment film.

Composition of alignment film coating liquid

10 parts by mass of the following modified polyvinyl alcohol

371 parts by mass of water

119 parts by mass of methanol

Glutaraldehyde 0.5 parts by mass

0.3 parts by mass of tetramethylammonium fluoride

(Formation of Optically Anisotropic Layer 2)

Subsequently, 1.8 g of the following discotic liquid crystalline compounds, ethylene oxide modified trimethylolpropane triacrylate (V # 360, Osaka Organic Chemical Co., Ltd. product) 0.2 g, the photoinitiator (irgacure) were carried out to the rubbing process surface of an oriented film. 0.090 g of 907, manufactured by Chiba Co., Ltd., sensitizer (Kayacure-DETX, manufactured by Nippon Gunpowder Co., Ltd.), 0.02 g, and 0.01 g of the air interface side vertical alignment agent (P-6) were dissolved in 3.9 g of methyl ethyl ketone. The solution was applied to the wire bar of # 4. This was attached to a metal frame and heated for 3 minutes in a thermostat at 125 ° C. to orient the discotic liquid crystal compound. Subsequently, UV irradiation was carried out for 30 seconds at 120 ° C. using a 100 W / cm high pressure mercury lamp to crosslink the discotic liquid crystal compound. Thereafter, the mixture was allowed to cool to room temperature. In this way, the optically anisotropic layer 2 was formed.

When the formed optically anisotropic layer 2 was transferred to the glass substrate and the birefringence characteristic was measured, the Nz value was 0 and the Re value was 142 nm. The direction of the slow axis was parallel to the rubbing direction of the alignment film.

Thus, the transparent film 10 in which the optically anisotropic layer 1 was formed on one side of the film 1 and the optically anisotropic layer 2 was formed on the other side of the film 1 was produced. It was 560 nm when the in-plane retardation Re of this transparent film 10 was measured at the wavelength of 550 nm. That is, this transparent film 10 has a monotonically increased Nz value from 0 to 1 in the thickness direction (Nz = 0 for optically anisotropic layer 2, Nz = 0.5 for film 1, Nz = 1 for optically anisotropic layer 1), and a wavelength of 550 nm. In-plane retardation Re in 560 nm is a transparent film of the Example of this invention.

CR1 = 0 was obtained when the produced transparent film 10 measured CR1 in front by wavelength using 550nm of Axometrics company. In addition, CR2 at azimuth angles of 45 degrees, 135 degrees, 225 degrees, and 315 degrees was measured at a polar angle of 60 degrees, and as a result, CR2 = 32 nm at azimuth angles of 45 degrees and 225 degrees, and CR2 = -32 nm at azimuth angles of 135 degrees and 315 degrees. It was. That is, the absolute values of CR2 in azimuth angles of 45 degrees, 135 degrees, 225 degrees and 315 degrees were approximately equal to 32 nm.

<Production of Polarizing Plate 10>

A roll-shaped polyvinyl alcohol film having a thickness of 80 µm was continuously stretched five times in an aqueous solution of iodine and dried to obtain a polarizing film. Kurere PVA-117H was used for polyvinyl alcohol. The transparent film 10 was laminated | stacked on the single side | surface of this polarizing film, and the tack film TD80U made by Fujifilm company was laminated | stacked on the other side as a protective film, and the polarizing plate 10 was manufactured. In addition, when superimposing the transparent film 10 on a polarizing film, the surface of the optically anisotropic layer 1 of the transparent film 10 and the polarizing film were contacted and superimposed.

The normalized polarization performance vector P 'of this polarizing plate 10 was measured by Axoscan. Standardized polarization capacity measured at a polar angle of 60 degrees from the normal direction of the film plane, and when the slow axis in the film plane was 0 degrees of azimuth, the azimuth angle was incident on a 45 degree direction, and the transparent film 10 was placed on the exit side of the polarizing film. The absolute value of component P45 'of vector P' was 0.995.

[Example 2]

<Production of Polarizing Plate 11>

When the transparent film 10 was overlaid on a polarizing film, the polarizing plate 11 of Example 2 was manufactured by the method similar to Example 1 except having contacted and adhere | attached the surface of the optically anisotropic layer 2 of the transparent film 10 and a polarizing film.

The normalized polarization performance vector P 'of this polarizing plate 11 was measured by Axoscan. Standardized polarization performance vector measured 60 degrees from the normal direction of a film plane, and when the slow axis in a film plane made the azimuth angle 0 degree, an azimuth angle incident a light beam in the direction of 45 degree | times, and placed the transparent film on the exit side of a polarizing film. The absolute value of component P45 'of P' was 0.995.

[Mounting and Evaluation on Liquid Crystal Display]

The liquid crystal display device was manufactured using the polarizing plates 1, 10, and 11 which were manufactured in Comparative Example 1, Example 1, and Example 2, respectively.

Specifically, each of the polarizing plates 1, 10, and 11 and a conventional polarizing plate (Z-tack manufactured by Fujifilm Co., Ltd. was used for the protective layer tack film of the polarizing plate) were fitted with an IPS-type liquid crystal cell to manufacture a liquid crystal display device. It was. Careful insertion was made so that the films 1 and the transparent films 10 and 11 of the polarizing plates 1, 10 and 11 were on the liquid crystal cell side, respectively. In addition, the in-plane absorption axes of the two polarizing plates sandwiching the liquid crystal cells were perpendicular to each other, and the in-plane absorption axes of the polarizing plates 1, 10, and 11 were fitted so as to be parallel to the in-plane slow axis of the IPS type liquid crystal cell. The IPS type liquid crystal cell was manufactured so that birefringence might be horizontally aligned in a voltage-free state at 300 nm. Merck ZLI-4792 was used for the liquid crystal.

As a result of measuring the transmittance of the voltage-free state, that is, the black state, of the liquid crystal display device thus manufactured at a polar angle of 60 degrees and an azimuth angle of 45 degrees, the liquid crystal display device using the polarizing plate 1 of Comparative Example 1 was 0.035%, In the case of the liquid crystal display device using the polarizing plate 10 of Example 1, it was 0.02% in the case of the liquid crystal display device using the polarizing plate 11 of Example 2. From this, compared with the polarizing plate 1 of the comparative example 1, it turns out that the polarizing plates 10 and 11 which are the Example of this invention have a small transmittance | permeability of a black state, and the contrast was improved more.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram of an example of the polarizing plate of this invention.

It is a schematic diagram which shows arbitrary linearly-polarized-state point P and its extinction point Q on Poincare sphere.

3 is a schematic diagram showing a trajectory of a conventional conversion example from an arbitrary linear polarization state point P on the Poincare sphere to the extinction point Q thereof.

4 is a schematic diagram showing a trajectory of a conventional conversion example from any linearly polarized light state point P on the Poincare sphere to the extinction point Q for each of the R light, the G light, and the B light.

It is a schematic diagram which showed the trace of the example of conversion from the arbitrary linearly-polarized-state point P on the Poincare sphere to the extinction point Q using the transparent film of this invention about each of R light, G light, and B light.

DESCRIPTION OF THE REFERENCE NUMERALS

10 polarizer

12 polarizer

14 protective film

16 Transparent film of the present invention

Claims (10)

As a transparent film which has at least 1 layer of a polymer film and the optically anisotropic layer which consists of a liquid crystal composition different from each other on both surfaces, It has optical anisotropy in the plane, the circular retardance (CRE1) in the normal direction of the film plane is approximately 0, the polar angle is 60 degrees from the normal direction of the film plane, and the azimuth angle is 45 degrees when the slow axis in the film plane is 0 degrees. An absolute value of Circular Retardance (CRE2) in light rays incident in four directions of 135 degrees, 225 degrees, and 315 degrees, respectively, is approximately equal, and is not zero. The method of claim 1, The transparent film whose absolute value of the said CRE2 is 32-38 nm. The method according to claim 1 or 2 A transparent film having at least one layer of an optically anisotropic layer made of rod-shaped on one side of the polymer film, and having at least one layer of an optically anisotropic layer made of a discotic liquid crystal compound on the other side. The polarizing plate which has a polarizing film and the transparent film of Claim 1 or 2. The liquid crystal display device which has a liquid crystal cell and the polarizing plate of Claim 4. A liquid crystal display device having a liquid crystal cell and at least one polarizing film, The liquid crystal display device which has the transparent film of Claim 1 or 2 between the said polarizing film and the said liquid crystal cell. delete delete delete delete

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