KR100789681B1 - Lcd device having an improved viewing angle characteristic - Google Patents

Abstract

The LCD device includes a pair of polarizing films 101 and 105 sandwiching an LC cell therebetween. The light incident side polarizing film 101 includes a polarizing layer 120 and a first retardation film 119, and the light exiting side polarizing film 105 includes a polarizing layer 120 and second and third retardation films 118. , 117). Certain combinations of the first and third retardation films 119 and 117 provide optical compensation for achieving lower leakage light and lower chromaticity variation in the display of the dark state in the LCD device 100.

LCD device, viewing angle

Description

LCD DEVICE HAVING AN IMPROVED VIEWING ANGLE CHARACTERISTIC

1 is a cross-sectional view of a pixel of an LCD device according to a first embodiment of the present invention.

2A and 2B are detailed cross-sectional views of a color-filter (CF) substrate and a thin film transistor (TFT) substrate, respectively, in combination with corresponding optical films.

3 is a perspective view showing the definition of the delay of a retardation film;

4 is a graph showing the relationship between the thickness direction retardation of a retardation film and a normalized transmittance.

5 is a graph showing the relationship between the thickness direction retardation of a retardation film and a normalized transmittance.

6 is a graph showing a delay range that achieves a reduction in leakage light when displaying a dark state.

7 is a graph showing the relationship between the thickness retardation of a retardation film and a normalized chromaticity variation.

8 is a graph showing a delay range that achieves normalized transmittance of 0.5 or less and normalized chromaticity variation of 1 or less.

9A and 9B are specific cross-sectional views of a CF substrate and a TFT substrate, respectively, combined with the corresponding optical film, used in the second embodiment of the present invention.

10A and 10B are specific cross-sectional views of a CF substrate and a TFT substrate, respectively, combined with the corresponding optical film, used in the third embodiment of the present invention.

11A and 11B are specific cross-sectional views of a first modification of the CF substrate and the TFT substrate of FIGS. 2A and 2B, respectively.

12A and 12B are specific cross-sectional views of a second modification of the CF substrate and the TFT substrate of FIGS. 2A and 2B, respectively.

13A and 13B are specific cross-sectional views of a third modification of the CF substrate and the TFT substrate of FIGS. 2A and 2B, respectively.

14A and 14B are specific cross-sectional views of a fourth modification of the CF substrate and the TFT substrate of FIGS. 2A and 2B, respectively.

Explanation of symbols on the main parts of the drawings

100: LCD device 101, 105: polarizing film

102 TFT substrate 103 LC layer

104: color filter substrate 106, 116: glass substrate body

107: insulating film 108: TFT

109: pixel electrode 110: common electrode

111, 113: alignment layer 112: LC molecule

114: color filter 115: light shielding film

117, 118, 119: retardation film 120: polarizing layer

121, 124: protective layer 123, 125: retardation film

FIELD OF THE INVENTION The present invention relates to liquid crystal display (LCD) devices, and more particularly to LCD devices that include a homogeneously aligned liquid crystal (LC) layer and have improved viewing angle characteristics. The invention also relates to polarizing film pairs for use in such LCD devices.

Side field mode LCD devices are known, such as in-plane-switching-mode (IPS-mode) LCD devices, where the pixel electrode and the common electrode generate a side electric field of the LC therebetween. . IPS-mode LCD devices have the advantage of wider viewing angle characteristics compared to conventional TN-mode LCD devices. In general, an IPS-mode LCD device includes an LC cell comprising a first and a second substrate and an LC layer sandwiched therebetween, and a first and second attached to the outer side of the first and second substrates of the LC cell, respectively. And a second polarizing film.

The first and second substrates have the function of visualizing a change in the orientation of the LC molecules of the LC layer defined by the lateral electric field. A polarizing film is comprised by laminating | stacking a transparent protective film like a triacetyl cellulose (TAC) film to a polarizing layer. The polarizing layer separates incident light into two polarized light components orthogonal to each other, passes a component having a vibrating plane parallel to the transmission axis of the polarizing layer among the polarized light components, and passes through the absorption axis of the polarizing layer among the polarized light components. Other components with parallel vibrating surfaces absorb or scatter.

In LCD devices, in general, the initial orientation of the polarizing film pair and the LC layer indicates that the LCD device is in a dark state when both electrodes do not produce an electric field therebetween and the LCD when both electrodes generate a specific electric field therebetween. The device is designed to indicate bright state. In the bright state, the LC molecules of the LC layer are oriented at an angle of λ / 2 from the initial orientation of the LC molecules.

In general, LCD devices having a homogeneously aligned LC layer, such as a transmissive IPS-mode LCD device, include polarizing film pairs sandwiching the LC cells therebetween when viewed in the thickness direction. All of the pair of polarizing films are arranged such that the transmission axes of all the polarizing films are orthogonal to each other. Such polarizing films are referred to in the art as orthogonal polarizers. The orthogonal polarizer has an undesirable viewing angle dependency, so that light incident in an oblique direction on the orthogonal polarizer changes the direction of the transmission axis of the polarizing film.

Therefore, the orthogonal polarizer disposed so that all of the transmission axes of the polarizing layers cross at right angles, the light incident on the LC cell in an oblique direction and passing through the first polarizing film is changed by the deviation from the right angle of the crossing angle. It is possible to have undesirable light components parallel to the transmission axis. Undesirable light components cause leakage light passing through the second polarizing film in the display of the dark state of the LCD device.

As mentioned above, the viewing angle dependency of the orthogonal polarizer causes a reduction in the viewing angle, i.e., the viewing range where the brightness, contrast ratio and coloring of the image is well perceived on the screen of the LCD device. In view of this, in order to obtain a wider viewing angle in the LCD device, it is essential to develop a light compensation polarizing film that can reduce the viewing angle dependency of the orthogonal polarizer to prevent leakage light and increase the viewing angle range. For example, Japanese Patent Application Laid-Open No. 2001-242462A discloses a technique used in a homogeneously oriented IPS-mode LCD device, wherein a two-axis retardation film serving as an optical compensation film compensates for orthogonal polarizers to obliquely enter light. The light component parallel to the transmission axis of the second polarizing film is changed perpendicular to the transmission axis, and the obliquely-incident light enters the LC cell in the oblique viewing direction and passes through the first polarizing film.

In the LCD device disclosed in the above publication, the simple addition of a light compensating film having a wavelength dependency similar to that of the LC layer, cannot optically compensate the orthogonal polarizer in the entire wavelength range, and is effective only in a specific wavelength range. This causes leaking light in other wavelength ranges, thus causing coloring of the image depending on the azimuth angle in the viewing direction. In addition, since the transparent protective layer of the polarizing film has a delay depending on the thickness of the transparent protective film, the obliquely incident light once converted into linearly polarized light by the light incident side polarizing layer is elliptically polarized by the transparent protective layer. It is converted back to light and additionally the polarization is converted by the LC layer, which increases undesirable leakage light and coloring of the emitted light.

In view of the above-mentioned problems of the prior art, it is an object of the present invention to provide a polarizing film pair and an LCD device capable of reducing leakage light in an oblique viewing direction without substantially changing chromaticity when displaying in a dark state.

The present invention provides a polarizing film pair including a first polarizing film and a second polarizing film each including a first polarizing layer, and the first polarizing film is disposed between the first polarizing layer and the second polarizing film. Coupled with a first retardation film, the first retardation film has birefringence characteristics, an in-plane retardation of 0 to 10 nm, and a thickness retardation of 0 to 35 nm, and the second polarizing film includes the second polarizing layer and the first retardation film. A second retardation film, the second retardation film having a birefringence characteristic, an in-plane delay of 35 to 245 nm, a first refractive index n1 <a second refractive index n2 A first refractive index n1 of the in-plane optical axis and a second refractive index n2 of the second in-plane optical axis, wherein the second optical axis is parallel or orthogonal to the absorption axis of the second polarizing layer, and the third retardation film has a birefringence characteristic. , In-plane delay of 0 to 15 nm, thickness direction delay of 50 to 123 nm, amount It has a single-axis optical characteristics, and an optical axis perpendicular to the second polarizing layer.

In addition, the present invention provides a homogeneous liquid crystal (LC) layer; First and second substrates sandwiching an LC layer to form an LC cell; And first and second polarizing films sandwiching an LC cell therebetween and including first and second polarizing layers, respectively, the first polarizing film being close to the second polarizing film on the surface of the first polarizing layer. A first retardation film, wherein the first polarization film is coupled to a first retardation film disposed between the first and second polarization layers, the first retardation film having a birefringence characteristic, an in-plane retardation of 0 to 10 nm, and zero And a thickness direction retardation of about 35 nm, wherein the second polarization film is combined with second and third retardation films disposed between the second polarization layer and the first polarization film, and the second retardation film has a birefringence characteristic, 35 A second refractive index n1 of the first in-plane optical axis and a second refractive index n2 of the second in-plane optical axis having an in-plane retardation of 1 to 245 nm, a first refractive index n1 <a second refractive index n2, and the second refractive index n2 of the second in-plane optical axis. The optical axis is parallel or perpendicular to the absorption axis of the second polarizing layer, The third retardation film has birefringence characteristics, in-plane retardation of 0 to 15 nm, thickness retardation of 50 to 123 nm, positive single axis optical properties, and an optical axis orthogonal to the second polarizing layer.

According to the polarizing film pair and the LCD device of the present invention, the specific combination of the first to the third retardation films provides a reduction in leakage light in an oblique viewing direction without substantially causing chromaticity variation in the display of the dark state.

More specifically, in a preferred embodiment of the present invention, the first retardation film changes the polarization state of light passing through the first polarization layer, and the second and third retardation films change the polarization state of light passing through the first retardation film and the LC layer. Change. This provides lower scattering of light passing through the second and third retardation films at the location of the first polarization layer, substantially reducing leakage light in an oblique viewing direction without causing chromaticity variation.

Each of the first and second polarizing films may be disposed on the light incidence side or the light exit side of the LCD cell as long as the polarization films may be arranged in opposite directions to each other.

The above and other objects, features and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings.

Prior to the description of the preferred embodiments for a better understanding of the invention, the principles of the invention are first described. Here, the first polarizing film is disposed on the light incidence side of the LCD cell, the second polarizing film is disposed on the light outgoing side of the LCD cell, and the second polarizing film is disposed on the light exit side from the light incidence side, Assume that the second retardation film is in this order. In the case of the polarizing film pair or LCD device of the present invention, the first retardation film, which may function as a protective layer of the first polarizing layer, is disposed close to the LCD cell on the surface of the first polarizing layer.

In order to prevent the light incident in the oblique direction into the LC layer of the LCD cell from changing into elliptical polarized light, the first retardation film preferably has a lower thickness retardation of less than 17 nm. This suppresses the phase change of the light caused by the LC layer depending on the wavelength, allowing incident light to pass through the LC layer in a state of substantially linearly polarized light.

A third retardation film disposed on the light exit side and having a positive single axis optical characteristic and an optical axis orthogonal to the first or polarizing layer, converts the once substantially linearly polarized light into elliptical polarized light. The second retardation film having an in-plane retardation such as n1 < n2 re-changes the elliptically polarized light into linearly polarized light. The polarized axis of linearly polarized light passing through the LCD cell and the polarized axis of linearly polarized light passing through the second retardation film have different directions. By designing the thickness retardation of the second and third retardation films in a range between 35 nm and 245 nm and a range between 50 nm and 123 nm, respectively, the viewing angle dependency of the polarizing film pair can be compensated.

If a single two-axis retardation film is used for optical compensation toward a single direction, the wavelength dependence of the retardation of the single retardation film will itself appear as a chromatic variation. On the other hand, as used in the present invention, the combination of two positive single-axis retardation films affects optical compensation in two directions, and the wavelength dependence can be canceled on the light exit side to reduce chromaticity variation.

Therefore, the combination of the three retardation films compensates for the wavelength dependence of the delay of the LC layer and the polarizing layer, and reduces leakage light in an oblique viewing direction without substantially causing chromaticity shift in the display of the dark state. Similar results can be obtained when the first polarizing film and the second polarizing film are disposed on the light exit side and the light incident side, respectively.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings, in which like components are designated by like reference numerals.

1 shows pixels of an IPS-mode LCD device according to a first embodiment of the present invention. The LCD device, generally indicated by the reference numeral 100, is a light incidence side polarizing film 101, a TFT (thin film transistor) substrate 102, and LC, which are continuously disposed from the light incidence side to the light exit side of the LCD device. A layer 103, a CF (color-filter) substrate 104, and a light exiting side polarizing film 105. The first alignment film 111 is formed close to the LC layer 103 on the surface of the TFT substrate 103, and the second alignment film 113 is formed close to the LC layer 103 on the surface of the CF substrate 104. do. The TFT substrate 102 includes a glass substrate body 106, on which an insulating film 107, a TFT 108, a pixel electrode 107, and a common electrode 110 are formed.

The TFT 108 controls the voltage provided to the pixel electrode 109. In the LCD device 100, the pixel electrode 109 and the common electrode 110 are formed on the TFT substrate 102 to provide a side electric field to the LC molecules 112 of the LC layer 103. The insulating film 107 may contain silicon nitride. The CF substrate 104 includes an organic substrate body 116 on which a color-filter 114 and a light shielding film 115 are formed. Color-filters 114 provide one of three primary colors, each including red, green, and blue. The light shielding film 115 shields the TFT 108, data lines (not shown), and the like from light. The color-filter 114 may be omitted when the LCD device is a monochrome LCD device.

2A and 2B show details of the outer side of the glass substrate body of the CF substrate 104 and the TFT substrate 102, respectively. The glass substrate body 116 of the CF substrate 104 has a polarizing film 105 including a retardation film nc 117, a retardation film na 118, and a polarizing layer 120 and a protective layer 124 thereon. ) Are mounted continuously. The glass substrate body 106 of the TFT substrate 102 continuously mounts a polarizing film 101 including a retardation film ni 119 and a polarizing layer 120 and a protective layer 121 thereon. The polarizing layer 120 is composed of polyvinyl alcohol (PVA), and the protective layers 121 and 124 are composed of TAC.

The retardation film (first retardation film: ni; 119), the retardation film (second retardation film: na; 118), and the retardation film (third retardation film: nc; 117) each have specific optical characteristics. These retardation films 119, 118, 117 may be composed of a film material which is attached in this order when viewed from the light incidence side, or may be composed of a coating material for coating the glass substrate body.

Generally, conventional polarizing films are used sandwiched between a pair of protective (TAC) films. However, in this embodiment, the retardation film ni 119 is disposed close to the glass substrate body 106 on the surface of the polarizing film 101, and the polarizing layer 120 is formed of the protective layer 121 and the retardation film ( ni; sandwiched between 119, the retardation film 119 has the function of a protective layer for the polarizing layer 120 of the first polarizing film 101. Similarly, the retardation film nc 117 and the retardation film na 118 are disposed close to the glass substrate body 116 on the surface of the polarizing film 105, and the retardation films 117 and 118 are the second polarized light. It has the function of a protective layer for the polarizing layer 120 of the film 105.

The protective layers 121 and 124 each have a function of a negative single axis retardation film having an optical axis orthogonal to the surfaces of the polarizing films 101 and 105, respectively. The protective layers 121 and 124 each have a delay depending on their thickness, but do not affect the image due to the equipment on the outer surface of the polarizing layer 120. The retardation film 119 has a thickness direction delay of 0 nm, that is, a delay of 0 nm in the thickness direction, and the retardation film 119 does not change the phase of polarized light. Therefore, the configuration in which the first polarizing film 101 is directly attached to the glass substrate body 106 corresponds to the configuration in which the retardation film 119 shown in FIG. 2B has a thickness direction delay of 0 nm.

The optically-compensated polarizing film pairs used in the LCD device 100 shown in Figs. 2A and 2B are characterized in that the retardation films 117, 118, and 119 allow the observer of the LCD device to display leaked light when the LCD device displays in the dark state. It is simulated to obtain a state that satisfies achieving the desired result of reduced leakage light to a level that is almost unrecognizable. Prior to this simulation, by varying the brightness of the backlight source from maximum brightness to reduced brightness, the level of backlight brightness that has little effect on the display quality of the IPS-mode LCD device in the oblique viewing direction is experimentally studied. This study found that half of the typical maximum luminance level of a backlight source during dark display allows the oblique viewing direction leakage light to have little effect on the display quality of the LCD device, and typically 1/4 of the maximum luminance is leakage. It has been found that light may not substantially affect display quality.

In view of the above findings, the level at which the observer hardly recognizes the leakage light is determined at half of the reference leakage light, which is the same as the leakage light observed in the oblique viewing direction from the orthogonal polarizer. In addition, the level of chromaticity variation observed between the front and oblique viewing directions, which does not cause deterioration of chromaticity when using optical compensation, is used as the reference chromaticity variation. Reference leakage light and reference chromaticity variation are used to determine the required delay range of the retardation film. The oblique viewing direction used in this simulation is 45 degrees azimuth from the optical axis of the polarizing film pair and 45 degrees from the plane of the substrate surface.

3 shows the definition of the direction of the refractive index components of the retardation films 117, 118, and 119, where n1 and n2 are in-plane refractive index components, and nz is a thickness direction refractive index component of the retardation film. For example, the in-plane delay of the retardation film is:

(n1-n2) × d

Is defined as the absolute value of, where "d" is the thickness in nanometers of the retardation film.

Thickness direction delay is:

[{(n1 + n2) / 2} -nz] × d

It is defined as the absolute value of.

In the simulation, the retardation film 117 has single axis optical properties of n1 <n2 and n2 <nz and (n1-n2) ≒ 0, and the retardation film 119 is here n1≥nz and n2≥nz and (n1 It was assumed that the single-axis optical characteristics of -n2) \ 0 and the retardation film 118 had optical characteristics of n1 <n2. The optical axis of the retardation film 118 is orthogonal to the optical axis (slow axis: n2) of the polarizing film 120, and the optical axes of the retardation films 117 and 119 are orthogonal to the polarization layer 120, and the LC layer 103 The axis is arranged such that the initial orientation is aligned with the optical axis of the retardation film 118. Whether the initial orientation of the LC layer is parallel or orthogonal to the optical axis of the polarizing film pair does not significantly affect the optical compensation effect since both directions suppress the phase change of the LC layer.

4 shows simulation results obtained between the thickness direction retardation of the retardation film 119 and the normalized transmittance during the display of the dark state, where the transmittance obtained for each retardation of the retardation film 119 is obtained by optical compensation. Normalized by optical transmittance when not adopted. If no optical compensation is adopted, the retardation films 117 and 119 are each replaced with a 80 μm thick TAC layer, and no retardation film is provided there.

In Fig. 4, the transmittance is calculated in the simulation of the thickness direction delay of the retardation film 119 varying from 0 to 50 nm, where the graph (i) dotted by a square point shows a retardation film having a thickness direction delay of 50 nm. The graph (ii) shown in FIG. 1 and dotted with a rhombus point shows a case in which it is combined with a retardation film having a thickness direction delay of 80 nm. As mentioned above, the transmittance is calculated for the case of the oblique viewing direction with respect to the orthogonal polarizer.

As can be understood in FIG. 4, the calculated normal transmittance is less than 0.5 in the full range of the thickness retardation adopted of the retardation film 119 and exhibits improved and wider viewing angle characteristics. The details of FIG. 4 show that the retardation film 117 should have a thickness retardation of 50 nm or more, and the retardation film 119 should be 50 in order to obtain a higher optical compensation effect and achieve a lower transmittance in the display of the dark state. It should have a thickness direction delay of less than nm.

Similar to FIG. 4 shown with respect to the retardation film 119, FIG. 5 shows the relationship between the thickness retardation of the retardation film 117 and the normalized transmittance in the display of the dark state obtained in the simulation. In this simulation, the delay film 118 had an in-plane delay of 130 nm, and the delay film 119 had a thickness direction delay of 0 nm. As can be appreciated in FIG. 5, for the case of the retardation film 118 having a thickness direction delay of 50 nm to 123 nm, the normalized transmittance is less than one.

6 shows the relationship between the in-plane direction delay of the retardation film 118 and the normalized transmittance obtained in the simulation. In this simulation, the thickness direction delays of the retardation film 117 and the retardation film 119 are fixed at 80 nm and 0 nm, respectively. As can be understood from FIG. 6, for the range between 35 nm and 245 nm of the thickness retardation of the retardation film 118, the normalized transmittance is 0.5 or less. Therefore, the leakage light in the oblique viewing direction of 45 ° azimuth angle and 45 ° declination angle in the dark state is reduced to a level at which the observer cannot substantially recognize the leakage light.

7 shows the relationship between the thickness direction delay of the retardation film 119 and the normalized chromaticity variation, obtained in the simulation. In this simulation, when the delay film 117 has a thickness direction delay of 50 nm (graph (i)) and 80 nm (graph (ii)), the thickness direction delay of the delay film 119 is 0 nm to 50 nm. And the in-plane retardation of the retardation film 118 is fixed at 130 nm, and the resulting chromaticity is measured in the front view and the oblique view to obtain chromaticity variation.

As can be understood from FIG. 7, in the case of the retardation film 117 having a thickness retardation of 50 nm, the chromaticity variation normalized over the range between 0 nm and 50 nm of the thickness retardation of the retardation film 119 is obtained. Less than 1, indicating no degradation in chromaticity variation between the front and oblique views. On the other hand, in the case of the retardation film 117 having a thickness retardation of 80 nm, if the thickness retardation of the retardation film 119 is less than 35 nm, the normalized chromaticity shift can be maintained below 1, and the retardation film ( If the thickness retardation of 119) is less than 17 nm, it can be kept below 0.5.

8 shows the relationship between the combination of thickness retardation of the retardation films 117 and 117 and the normalized chromaticity variation. As described above, since the chromaticity variation depends on the thickness delay of the delay film 117, another simulation is performed for the thickness delay in the range of 50 nm to 123 nm of the delay film 117, which is effective in reducing the luminance. Was performed. In this simulation, a combination of thickness retardation of the retardation films 117 and 119 was obtained, which achieves a normalized chromaticity variation of one.

8 shows the results of the simulation. In the same figure, a delay in the range of achieving a normalized transmittance of 0.5 and a chromaticity variation of less than 1 was selected and shown surrounded by a thick square shape. This range is defined as a thickness direction delay between 0 nm and 35 nm of the retardation film 119 and a thickness direction delay between 50 nm and 123 nm of the retardation film 117. In addition, other ranges of delays to achieve transmittance below 0.5 and chromaticity variations below 0.5 were selected in FIG. 8 as more preferred ranges. The other range is defined by the following relationship using the thickness direction delay nc1 of the delay film 117 and the thickness direction delay ni1 of the delay film 119:

57.0-0.23 × ni1 + 0.11 × ni1 ² ≤nc1≤120.0-0.42 × ni1-0.08 × ni1 ²

Here, ni1 is in the range of 0 to 17 nm.

In the present embodiment, the combination of the thickness retardation of the retardation films 117 and 119 is selected within the range defined by the thick square shape, and the retardation of the retardation film 118 is a normalized transmittance of 0.5 in FIG. It is selected within the range to achieve. This provides a reduction in leakage light to a level at which the observer perceives little leakage light without substantially degrading the chromaticity variation between the frontal view and the oblique view in the display of the dark state. This result indicates that the combination within the above range for the delay of the retardation films 117, 118, and 119 results in light scattering in which the retardation films 117 and 118 are caused by the LC layer 103 and the CF substrate 104. It is considered that the lower scattering condition is obtained at the position of the polarizing layer 120 constituting the second polarizing film 105 arranged on the light exit side of the LCD device.

In this embodiment, the retardation film ni 119 is disposed close to the LC layer 103 on the surface of the light incident side first polarizing film 101 to be used as a protective layer for the polarizing layer 120, and LC In order to suppress the light incident in the oblique direction to the layer 103 from being converted into the light elliptically polarized by the protective layer, the retardation film 119 preferably has a smaller thickness retardation of 17 nm or less. This suppresses the phase change of the light depending on the wavelength, which is encountered in the LC layer 103 of the conventional LCD device, and transmits the light as almost linearly polarized light. On the other hand, on the light exit side of the LCD device, the retardation film nc 117 having a positive single axis optical characteristic and an optical axis orthogonal to the surface of the polarizing layer 120 is linearly polarized through the LC layer 103. The retardation film 118, which has optical characteristics in which the light is changed once into elliptical polarized light and the in-plane refractive indices n1 and n2 of the optical axis have a relationship of n1 < n2, is ellipsoid from the retardation film (nc) 117. The polarized light is changed back to linearly polarized light.

The direction of the polarized axis of polarized light passing through the LC layer 103 is different from the direction of the polarized axis of polarized light passing through the retardation film 118. The in-plane retardation of the retardation film (na) 118 designed in the range of 35 to 245 nm and the thickness retardation of the retardation film 117 designed in the range of 50 to 123 nm offset the viewing angle dependency of the orthogonal polarizer, where For oblique incident light the crossing angle deviates from the right angle. That is, the retardation films 117 and 118 so designed change the polarized axis of oblique incident light toward the absorption axis of the light exiting side second polarizing film 105.

When one two-axis retardation film is used for unidirectional optical compensation, that is, linear compensation, the wavelength dependence of the birefringence of the single retardation film itself appears as a chromatic variation. On the other hand, in this embodiment, the combination of two positive single-axis retardation films optically compensates the incident light toward the two directions. This allows shorter wavelength light components with higher wavelength dependence to bypass larger amounts of optical paths, canceling wavelength dependence at the light exit side and reducing chromatic dispersion.

Therefore, the wavelength dependence of the birefringence of the LC layer 103 including the retardation films 117 and 118 and the optical compensation film can be suppressed, thereby suppressing the leakage light in the oblique viewing direction in the display of the dark state and causing chromaticity variation. It can provide optical compensation of a wider wavelength range without. This embodiment improves the viewing angle characteristic, thereby improving the display quality of the LCD device.

In some LCD devices, haze treatment is performed on the surface of the polarizing film to improve the visibility of the image. In such LCD devices, when more leakage light is caused in an oblique direction in the display of a dark state, the light emitted in the oblique direction may be emitted toward the front field of view due to the haze treatment of the polarizing film, thereby reducing the contrast ratio in the front field of view. It may deteriorate. In this embodiment, the optical compensation using the retardation films 117, 118, and 119 reduces leakage light in oblique directions during display in the dark state, thereby suppressing front leakage light caused by surface treatment. Therefore, the present embodiment reduces the front brightness in the display of the dark state, thereby improving the contrast ratio of the front view and providing a higher resolution image.

9A and 9B show details of the outside of the glass substrate body of the CF substrate and the TFT substrate of the LCD device, respectively, according to the second embodiment of the present invention, similar to FIG. The LCD device of this embodiment is similar to the LCD device of the first embodiment shown in FIG. 1 except for the arrangement of the delay film. More specifically, in this embodiment, the retardation films 118 and 117 are continuously formed on the glass substrate body 116. The retardation film 117 has a function of protecting the polarization layer 120 of the light exiting side second polarization film 105.

Simulations were performed to study the conditions of the optical properties of the retardation films 117, 118, 119 to achieve a reduction in leakage light to a level at which the observer hardly perceives leakage light in the display of the dark state. The conditions of the simulation are similar to those of the simulation performed in the first embodiment. In the simulation of this embodiment, the retardation film 118 had an optical axis orthogonal to the optical axis of the polarizing layer 120.

Simulation results are similar to the results shown in FIGS. 4 to 8. Therefore, the arrangement order of the retardation films 117 and 118 influences the result that the retardation film 117 has single-axis optical properties of n1 <nz and n2 <nz and the retardation film 118 has optical properties of n1 <n2. Does not have The combination of the delays of the retardation films 117, 118, and 119 having the range described above with respect to the first embodiment is also effective in this embodiment.

10A and 10B show details of the outer side of the glass substrate body of the CF substrate and the TFT substrate, respectively, in the LCD device according to the third embodiment of the present invention, similarly to FIG. The LCD device of this embodiment is similar to the LCD device of the second embodiment except that the two delay films 123 and 125 of the present embodiment constitute the delay film 117 of the second embodiment.

The retardation films 123 and 125 are each composed of a single-axis retardation film having an optical axis orthogonal to the polarization plane of the polarization film 105. One of the retardation films 123 and 125 is generally composed of a TAC used to construct a protective layer, and the other of the retardation films 123 and 125 is a material that compensates for the excess or lack of the delay provided by the TAC. The combination of the retardation films 123 and 125 has optical properties such as thickness retardation similar to that of the retardation film 117.

In the above embodiment, the first polarizing film 101 and the retardation film 119 are disposed on the light incidence side of the LCD device 100, and the second polarizing film 105 and the retardation films 117 and 118 are light exiting. Is placed on the side. However, the first polarizing film 101 and the retardation film 119 may be disposed on the light exit side, and the second polarizing film 105 and the retardation films 117 and 118 may be disposed on the light incident side. Further, the direction of incident light may be opposite to that of FIG. 1 or may be incident on the second polarizing film 105 to achieve the advantages of the present invention. The retardation films 117, 118, and 119 need not be attached to the polarizing layer, and another film or glass substrate body is disposed between the retardation film and the polarizing layer as long as the other film or glass substrate does not change the polarization state of the polarized light. May be

11A and 11B are cross-sectional views of the CF substrate and the TFT substrate according to the first modification of the drawings shown in FIGS. 2A and 2B, respectively. In the first modification, the TFT substrate 101 is similar to the TFT substrate 102 of the first embodiment, and the CF substrate 104 is a protective layer between the glass substrate body 116 and the second polarizing film 105. Only the fourth retardation film n1 119 having a function is included. The second and third retardation films na, nc 118 and 117 are disposed between the glass substrate body 116 of the CF substrate 104 and the first polarizing film 101.

12A and 12B are cross-sectional views of the CF substrate and the TFT substrate according to the second modification of the drawings shown in FIGS. 2A and 2B, respectively. In the second modification, the TFT substrate 102 is similar to the TFT substrate 102 of the first embodiment, and the second polarizing film 105 is provided between the polarizing layer 120 and the glass substrate body 116. Retardation film (na) 118. The third retardation film nc 117 is disposed between the glass substrate body 116 of the CF substrate 104 and the first polarizing film 101.

13A and 13B are cross-sectional views of a CF substrate and a TFT substrate according to a third modification of those shown in FIGS. 2A and 2B, respectively. In the third modification, the TFT substrate 102 is similar to the TFT substrate 102 of the first embodiment, and the CF substrate 104 is the second retardation film between the polarizing film 120 and the glass substrate body 116. (na; 118) only. The third retardation film nc 117 is disposed between the glass substrate body 116 of the CF substrate 104 and the first polarizing film 101.

14A and 14B are cross-sectional views of a CF substrate and a TFT substrate according to a third modification of those shown in FIGS. 2A and 2B, respectively. In the fourth embodiment, the TFT substrate is similar to the TFT substrate 102 of the first embodiment, and the CF substrate 104 is the polarizing film 120 and the glass substrate body 116 to protect the polarizing film 120. A portion of the third retardation film nc 117 is included in between. The remaining portions of the second retardation film na 118 and the third retardation film nc 117 are disposed between the glass substrate body 116 of the CF substrate 104 and the first polarizing film 101.

Since the above-described embodiments are merely exemplary, the present invention is not limited to the above-described embodiments, and various changes or modifications can be easily made by those skilled in the art without departing from the scope of the present invention.

As described above, the present invention provides a polarizing film pair and an LCD device capable of reducing leakage light in an oblique viewing direction without substantially changing chromaticity when displaying in a dark state.

Claims (9)

As a polarizing film pair provided with the 1st and 2nd polarizing films 101 and 105 containing the 1st and 2nd polarizing layers 120 and 120, respectively, The first polarizing film 101 is combined with the first retardation film 119 disposed between the first polarizing layer 120 and the second polarizing film 105, and the first retardation film 119 is With birefringence properties, in-plane retardation of 0 to 10 nm and thickness retardation of 0 to 35 nm, The second polarizing film 105 is combined with second and third retardation films 118 and 117 disposed between the second polarizing layer 120 and the first polarizing film 101, The second retardation film 118 has a birefringence characteristic, an in-plane retardation of 35 to 245 nm, a first refractive index n1 of the first in-plane optical axis, and a first refractive index n1 <second refractive index n2. Has a second refractive index n2 of the in-plane optical axis, and the second optical axis is parallel or orthogonal to the absorption axis of the second polarizing layer 120, The third retardation film 117 has a birefringence characteristic, an in-plane retardation of 0 to 15 nm, a thickness retardation of 50 to 123 nm, a positive monoaxial optical characteristic, and orthogonal to the second polarizing layer 120. A polarizing film pair having an optical axis. The method of claim 1, The first retardation film 119 has an in-plane retardation of 0 to 7 nm and a thickness retardation ni1 of 0 to 17 nm, The third retardation film 117 has an in-plane retardation and a thickness retardation nc1 of 0 to 10 nm. 57.0-0.23 × ni1 + 0.11 × ni1 ² ≤ nc1 ≤ 120.0-0.42 × ni1-0.08 × nil ² To maintain, a pair of polarizing film. The method of claim 1, The first polarizing film 101 has a first protective layer 121, The first retardation film 119 and the first protective layer 121 sandwich the first polarization layer 120 therebetween, The second polarizing film 105 has a second protective layer 124, And the second and third retardation films (118, 117) and the second protective layer (124) sandwich the second polarization layer (120) therebetween. The method of claim 1, The second retardation film (118) is disposed closer to the first polarization film (101) than the third retardation film (117), polarizing film pair. The method of claim 1, And the second retardation film (118) is disposed farther from the first polarization film (101) than the third retardation film (117). Homogeneously oriented liquid crystal (LC) layer 103; First and second substrates (102, 104) sandwiching the LC layer (103) therebetween to form an LC cell; And First and second polarizing films 101 and 105 sandwiching the LC cell therebetween and including first and second polarizing layers 120 and 120, respectively, The first polarizing film 101 is combined with the first retardation film 119 disposed between the first polarizing layer 120 and the second polarizing film 105, and the first retardation film 119 is Having birefringence characteristics, in-plane retardation of 0 to 10 nm, and thickness retardation of 0 to 35 nm, The second polarizing film 105 is combined with second and third retardation films 118 and 117 disposed between the second polarizing layer 120 and the first polarizing film 101, The second retardation film 118 has a birefringence characteristic, an in-plane retardation of 35 to 245 nm, a first refractive index n1 and a second refractive index of the first in-plane optical axis, wherein the first refractive index n1 <second refractive index n2. Has a second refractive index n2 of the in-plane optical axis, and the second optical axis is parallel or orthogonal to the absorption axis of the second polarizing layer 120, The third retardation film 117 has a birefringence characteristic, an in-plane retardation of 0 to 15 nm, a thickness retardation of 50 to 123 nm, a positive monoaxial optical characteristic, and orthogonal to the second polarizing layer 120. A liquid crystal display (LCD) device having an optical axis. The method of claim 6, The first in-plane optical axis of the second retardation film (118) is parallel or orthogonal to the optical axis of the homogeneously oriented LC layer (103). The method of claim 6, The second retardation film 118 is disposed closer to the first polarization film 101 than the third retardation film 117, and the first in-plane optical axis of the second retardation film 118 is homogeneous. LCD device orthogonal to the optical axis of the oriented LC layer (103). The method of claim 6, The second retardation film 118 is disposed farther from the first polarization film 101 than the third retardation film 117, and the first in-plane optical axis of the second retardation film 118 is homogeneous. LCD device parallel to the optical axis of the oriented LC layer (103).

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