WO2011142587A2

WO2011142587A2 - Patterned retarder laminated composite polarizing plate and display apparatus using the same

Info

Publication number: WO2011142587A2
Application number: PCT/KR2011/003473
Authority: WO
Inventors: Bong Jin Choi; Byoung In Kim; Oh Hyoung Cho; Soon Bum Kwon; Kyoung Su Ha; Yong Hwan Kim
Original assignee: Dongwoo Fine-Chem Co., Ltd.
Priority date: 2010-05-11
Filing date: 2011-05-11
Publication date: 2011-11-17
Also published as: WO2011142587A3

Abstract

The present invention relates to a composite polarizing plate including a patterned retarder which is laminated on a polarizing plate by an adhesive layer, wherein a refractive index (N) of the adhesive layer satisfies the equation (1): min(n_o, n_e) ≤ N ≤ max (n_o, n_e) (1) wherein n_o represents an ordinary refractive index of the patterned retarder, n_e represents an extraordinary refractive index of the patterned retarder, min(n_o, n_e) represents the smaller between n_o and n_e, and max(n_o, n_e) represents the greater between n_o and n_e, respectively. A three-dimensional display apparatus comprising the composite polarizing plate can show a uniform three-dimensional image because the moire due to difference in refractive indices between a patterned retarder and an adhesive layer can be improved. It is possible for the composite polarizing plate to provide a thinner display device since the patterned retarder can be directly laminated on the polarizing plate and a separate base film is not needed. It is also possible for the composite polarizing plate to considerably lower the possibility that foreign substances are included between layers when preparing display device including a patterned retarder and a polarizing plate.

Description

PATTERNED RETARDER LAMINATED COMPOSITE POLARIZING PLATE AND DISPLAY APPARATUS USING THE SAME

The present invention relates to a patterned retarder laminated composite polarizing plate and a display apparatus using the composite polarizing plate.

A viewer physiologically and empirically perceives three-dimensional depth when watching a display. In general, three-dimensional images are implemented based on binocular parallax, which is a basic principle to explain why the viewer feels three-dimensional depth at close distance.

Using the binocular parallax, two different images are separately captured using at least two cameras for the left and right eye, and the captured images are displayed separately to the left and right eye. The images are then combined in the brain to give the perception of three-dimensional depth.

Three-dimensional image technologies can be divided in two categories: methods using polarized glasses and methods not using polarized glasses. Examples of the technologies using glasses include (1) anaglyph method which uses glasses where the two lenses are different colors, (2) polarization method which uses glasses where the two lenses have different polarized directions, and (3) time-sharing method which uses shutter glasses in synchronization with the refresh rate of the screen.

The technologies using polarized glasses require a display device for displaying three-dimensional images and polarized glasses for observing the displayed three-dimensional images.

Meanwhile, many of the three-dimensional displays which are using polarized glasses include a patterned retarder (retarder patterns on a base film). The patterned retarder is laminated on one side of a polarizing plate by a permanent or pressure sensitive adhesive.

However, the patterned retarder can cause deterioration of display quality because directions of the optical axes (directions of extraordinary axes) of each of the patterned areas of the patterned retarder are different from each other.

In the patterned retarder including repeatedly arranged retarder patterns, light and shadow patterns can be detected due to differences in refraction indices and penetration ratios of the patterned retarder, and moire patterns also can be detected when the light and shadow patterns interfere with diffusion patterns of a backlight or light and shadow patterns of prism sheet, etc.

The present invention is to provide a composite polarizing plate including a patterned retarder so that polarization of a light, phase difference compensation of the polarized light, and image separation for three-dimensional images can be accomplished at the same time.

The present invention is also to provide a composite polarizing plate to improve moire effect due to brightness difference between patterned areas in a patterned retarder and difference in refractive indices between the patterned retarder and an adhesive layer.

The present invention is also to provide a display apparatus including the composite polarizing plate.

The present invention provides a composite polarizing plate including a patterned retarder which is laminated on a polarizing plate by an adhesive layer, wherein a refractive index (N) of the adhesive layer satisfies the following equation (1):

min(n_o, n_e) ≤ N ≤ max (n_o, n_e) (1)

wherein n_o represents an ordinary refractive index of the patterned retarder, n_e represents an extraordinary refractive index of the patterned retarder, min(n_o, n_e) represents the smaller between n_o and n_e, and max(n_o, n_e) represents the greater between n_o and n_e, respectively.

The present invention provides a composite polarizing plate including a patterned retarder which is laminated on a polarizing plate by an adhesive layer, wherein the refractive index (N) satisfies the following equation (2):

min(n_o, n_e) + | n_o - n_e| / 3 ≤ N ≤ max(n_o, n_e) - | n_o - n_e| / 3 (2)

The present invention provides a composite polarizing plate including a patterned retarder which is laminated on a polarizing plate by an adhesive layer, wherein the refractive index (N) satisfies the following equation (3):

0.99Ne ≤ N ≤ 1.01Ne (3)

wherein Ne = (n_o + n_e) / 2, n_o represents an ordinary refractive index of the patterned retarder, and n_e represents an extraordinary refractive index of the patterned retarder, respectively.

The present invention provides a composite polarizing plate including a patterned retarder which is laminated on a polarizing plate by an adhesive layer, wherein the refractive index (N) satisfies the following equation (4):

0.994Ne ≤ N ≤ 1.006Ne (4)

According to a composite polarizing plate of the present invention, it is possible to provide a uniform three-dimensional image because the moire effect due to difference in refractive indices between a patterned retarder and an adhesive layer can be improved.

According to a composite polarizing plate of the present invention, it is possible to provide a thin display device because the patterned retarder can be directly laminated on a polarizing plate and a separate base film is not needed.

According to a composite polarizing plate of the present invention, it is possible to reduce eye fatigue and dizziness due to brightness difference in images which are perceived by left and right eye, because the bright difference between patterned areas is very little.

When a composite polarizing plate of the present invention is applied to a display manufacturing process, it is possible to lower possibility that foreign substances are included between layers when laminating a patterned retarder on a polarizing plate.

A composite polarizing plate according to the present invention can be widely applied to many types of display apparatuses such as reflective or trans-reflective liquid crystal display (LCD), plasma display panel (PDP) and organic EL display (OLED), etc.

In the drawings:

FIGS. 1 and 2 show examples of composite polarizing plates according to the present invention;

FIGS. 3 and 4 show examples of reflective liquid crystal displays including composite polarizing plates according to the present invention;

FIGS. 5 and 6 show examples of trans-reflective liquid crystal displays including composite polarizing plates according to the present invention;

FIGS. 7 and 8 show examples of a plasma display panel or an organic EL display displays including composite polarizing plates according to the present invention;

FIG. 9 shows a glasses type three-dimensional image display system including a composite polarizing plate according to the present invention; and

FIG. 10 is a diagram to briefly explain the principle of the three-dimensional image display system in FIG. 9.

* REFERENCE SYMBOLS IN THE DRAWINGS

10, 11: polarizing plates of a liquid crystal display

12, 13: transmission axes of polarizing plates of a liquid crystal display

20, 21: patterned retarders of a liquid crystal display

22, 23: slow axes of patterned retarders of a liquid crystal display

30, 31: patterned retarders of a pair of eyeglasses

32, 33: slow axes of patterned retarders of a pair of eyeglasses

40, 41: polarizing plates of a pair of eyeglasses

42, 43: transmission axes of polarizing plates of a pair of eyeglasses

60: polarizing plate of a liquid crystal display

61: first image display area

62: second image display area

63: patterned retarder

64: first patterned area

65: second patterned area

70: pair of polarization eyeglasses

71: first polarization area

72: second polarization area

74: left lens of eyeglasses

75: right lens of eyeglasses

100: composite polarizing plate

110: polarizing plate

120: patterned retarder

130: adhesive layer

140: transparent base layer

200: liquid crystal panel

210: second base layer

220: first base layer

230: liquid crystal layer

240: reflection layer

310: lower polarizing plate

320: retardation layer

410: backlight unit

510: plasma display or organic EL display

The present invention relates to a composite polarizing plate including a patterned retarder which is laminated on a polarizing plate by an adhesive layer, wherein a refractive index (N) of the adhesive layer satisfies one of the above equations (1)-(4). A three-dimensional display apparatus comprising the composite polarizing plate can show a uniform three-dimensional image because the moire due to difference in refractive indices between a patterned retarder and a adhesive layer can be improved. It is possible for the composite polarizing plate to provide a thinner display device since the patterned retarder can be directly laminated on the polarizing plate, and a separate base film is not needed. It is also possible for the composite polarizing plate to considerably lower the possibility that foreign substances are included between layers when preparing display device including a patterned retarder and a polarizing plate.

Hereinafter, the present invention is described in detail.

As shown in FIG. 1, a composite polarizing plate can include a polarizing plate 110, an adhesive layer 130 which is laminated on the polarizing plate 110, and a patterned retarder 120 which is laminated on the adhesive layer 130. The patterned retarder 120 can be directly coated on the polarizing plate. For example, the patterned retarder 120 can be coated on a polarizer protection film or a retardation film which is placed on a surface of the polarizing plate.

Furthermore, when physical property such as strength of the patterned retarder 120 is enough, or it is advantageous in process to prepare the patterned retarder 120 first and to laminate it to the polarizing plate later, the patterned retarder 120 can be formed on a transparent base layer 140, and then the base layer 140 on which the patterned retarder 120 is formed can be laminated on the polarizing plate.

Any polarizing plates which are commonly used in displays can be used as a polarizing plate in the present invention. For example, a laminated structure including a polarizer, and at least one of the functional films selected from the group consisting of a polarizer protection film and a retardation film laminated on one or both sides of the polarizer can be used as the polarizing plate of the present invention. Also, a thin polarizing plate which is manufactured by forming a micro-patterned conducting grid on a transparent base layer and coating an insulating layer on valleys and ridges of the conducting grid can be used.

Type of a polarizer is not limited in the present invention, and any type of polarizer which can be commonly used in displays can be used. For example, a polarizer which is manufactured by dying a polyvinyl alcohol film with iodine or dichroic dye and extending it can be used.

An adhesive layer of the present invention is to attach a patterned retarder on a side of a polarizing plate.

In the present invention, the adhesive layer can be consisted of a permanent adhesive or a pressure sensitive adhesive.

In the present invention, in a uniaxial retardation layer, extraordinary refractive index (n_e) represents a refractive index of a direction which has a different refractive index value among refractive indices of x, y and z axes, and ordinary refractive index (n_o) represents refractive indices of the other two directions (refractive indices of the other directions which are perpendicular to the direction of the extraordinary refractive index).

In biaxial retardation layer, extraordinary refractive index (n_e) represents either a maximum refractive index or a minimum refractive index among refractive indices of x, y and z axes, one of which has a bigger difference from a refractive index that is neither a maximum refractive index nor a minimum refractive index than the other, and ordinary refractive index (n_o) represents refractive indices of the other two directions.

A refractive index (N) of an adhesive layer of the present invention is desirably between an ordinary refractive index (n_o) and extraordinary refractive index (n_e) of a patterned retarder as shown in the following equation (1). It is to reduce brightness differences between retarder patterns and to eliminate moire effect.

min(n_o, n_e) ≤ N ≤ max (n_o, n_e) (1)

(In the above equation, n_o represents an ordinary refractive index of the patterned retarder, n_e represents an extraordinary refractive index of the patterned retarder, min(n_o, n_e) represents the smaller between n_o and n_e, and max (n_o, n_e) represents the greater between n_o and n_e, respectively.)

Furthermore, in the present invention, it is more desirable for the refractive index (N) of an adhesive layer to be within a range described in the following equation (2), in order to reduce brightness differences between retarder patterns and to eliminate moire patterns. The equation (2) shows that when the gap between an ordinary refractive index and extraordinary refractive index is divided with three equal parts, it is more effective to reduce brightness differences between retarder patterns and eliminate moire patterns if the refractive index (N) is within a part which contains an arithmetic mean of the ordinary refractive index and the extraordinary refractive index.

min(n_o, n_e) + | n_o - n_e| / 3 ≤ N ≤ max(n_o, n_e) - | n_o - n_e| / 3 (2)

(In the above equation, n_o represents an ordinary refractive index of the patterned retarder, n_e represents an extraordinary refractive index of the patterned retarder, min(n_o, n_e) represents the smaller between n_o and n_e, and max(n_o, n_e) represents the greater between n_o and n_e, respectively.)

Furthermore, in the present invention, it is more desirable for the refractive index (N) of an adhesive layer to be within a range described in the following equation (3), in order to reduce brightness differences between retarder patterns and to eliminate moire patterns. The equation (3) shows that it is more effective to reduce brightness differences between retarder patterns and eliminate moire patterns when a difference between the refractive index (N) of the adhesive layer and an arithmetic mean of the ordinary refractive index and the extraordinary refractive index is less than 1%.

0.99Ne ≤ N ≤ 1.01Ne (3)

(In the above equation, Ne = (n_o + n_e) / 2, n_o represents an ordinary refractive index of the patterned retarder, and n_e represents an extraordinary refractive index of the patterned retarder, respectively.)

Furthermore, in the present invention, it is more desirable for the refractive index (N) of an adhesive layer to be within a range described in the following equation (4), in order to reduce brightness differences between retarder patterns and to eliminate moire patterns. The equation (4) shows that it is more effective to reduce brightness differences between retarder patterns and eliminate moire patterns when a difference between the refractive index (N) of the adhesive layer and an arithmetic mean of the ordinary refractive index and the extraordinary refractive index is less than 0.6%.

0.994Ne ≤ N ≤ 1.006Ne (4)

Assume two layers with different refractive indices (a first medium and a second medium). When a light passes through a border of the two layers, a refractive index of a light which is made incident from the first medium to the second medium perpendicularly is R=((n₂-n₁)/(n₂+n₁))² (In the equation. n₁ is a refractive index of the first medium, and n₂ is a refractive index of the second medium.)

Assuming that an adhesive layer is the first medium and a patterned retarder is the second medium, n₂ = n_e and R_e=((n_e-n₁)/(n_e+n₁))² when a polarization direction of an incident light is in the direction of the extraordinary refractive index, and n₂ = n_o and R_o=((n_o-n₁)/(n_o+n₁))² when a polarization direction of an incident light is in the direction of the ordinary refractive index.

Meanwhile, extraordinary axes of two patterned areas (a first patterned area and a second patterned area) of a patterned retarder are configured to be perpendicular to each other, so when an incident light is parallel to an extraordinary axis of the first patterned area, the incident light is perpendicular to an extraordinary axis of the second patterned area. Therefore, reflectance values of the first patterned area and the second patterned area are R_e=((n_e-n₁)/(n_e+n₁))² and R_o=((n_o-n₁)/(n_o+n₁))², respectively.

If n₁ is not between n_e and n_o, the difference between R_e and R_o gets bigger and a severe decline of brightness is occurred due to the decline of a penetration ratio of the patterned retarder. However, if n1 is between n_e and n_o, the difference between R_e and R_o gets smaller and overall penetration ratio is not changed rapidly, so the brightness decline due to the decline of penetration ratio of the patterned retarder is not severe.

As described above, when a refractive index of an adhesive layer of the present invention satisfies the equation (1), brightness differences between retarder patterns can be reduced and moire effect can be eliminated. Moreover, the refractive index of the present invention satisfies the equation (2), (3), and (4) and gets closer to the value of Ne, which is the arithmetic mean of the ordinary refractive index and the extraordinary refractive index, the above-mentioned effects gets more effective.

It is more preferable to keep a polarization direction of an incident light to the patterned retarder being between extraordinary axes of two patterned areas (the first patterned area and the second patterned area) of the patterned retarder, as well as the refractive index of the adhesive layer being in the above-mentioned range. Moreover, it is more preferable that the polarization direction is closer to the middle of the two extraordinary axes (the direction which bisects the angle between the two extraordinary axes).

For example, when an optical axis (extraordinary axis) of the first patterned area is x (0°) and an optical axis (extraordinary axis) of the second patterned area is y (90°), a polarization direction of a light which is made incident from the adhesive layer to the patterned retarder vertically is desirably between 0° and 90°, and more desirably closer to 45°, for example, between 22.5° and 67.5°.

The polarization direction which is configured as mentioned above enables to suppress reflection between patterned areas in the patterned retarder and reflection between the patterned retarder and the adhesive layer. The reason is as follows.

When a light which has an arbitrary polarization direction enters the patterned retarder, a reflection ratio of the light which has made incident to the first patterned area is calculated by dividing the light into two electric field components, E_e1 and E_o1, and summing two reflection ratios each of which are respectively calculated from E_e1 and E_o1. A reflection ratio of the light which has made incident to the second patterned area is calculated by dividing the light into two electric field components, E_e2 and E_o2, and summing two reflection ratios each of which are respectively calculated from E_e2 and E_o2.

For example, when n_e and n_o of the first patterned area is about the same as n_e and n_o of the second patterned area (n_e1 = n_e2, n_o1 = n_o2) and only extraordinary axes are different from each other, n_e-n₁ is not same as n_o-n₁ unless n₁ = (n_e+n_o)/2. Intensity of the reflected light can be expressed as E_i ²×R_i = E_ei ²×R_e + E_oi ²×R_o (Here, E_ei and E_oi represent intensities of electric field of directions of an extraordinary axis and an ordinary axis in the first and second patterned area). In this case, when a light enters the first or second patterned area, the electric field component of the light which has an optical axis that is closer to a vector direction of the electric field has more intensity.

In this case, a difference is occurred between overall reflective ratios of each patterned areas because R_es between the first and second patterned areas gets different. Therefore, brightness is different for each patterned areas. Moreover, an error in the polarization of light can be occurred due to the difference of reflective ratios between each of the patterned areas. Therefore, in the present invention, the polarization direction which has made incident to the patterned retarder is configured not to be in the direction of extraordinary axes of each patterned areas but to be between extraordinary axes of two patterned areas of the patterned retarder, and more desirably in the direction closer to the middle of the two extraordinary axes, for reducing reflection in each of the patterned areas.

As described above, it is most effective to reduce brightness differences between retarder patterns and eliminate moire effect if the refractive index satisfies any one of the equations (1) through (4), and the polarization direction which has made incident to the patterned retarder is between extraordinary axes of two patterned areas of the patterned retarder.

The patterned retarder of the present invention includes a uniaxial patterned retarder and a biaxial patterned retarder. The above-mentioned relations between the extraordinary refractive index and the ordinary refractive index in the uniaxial patterned retarder can be equally applied to relations between maximum refractive index and minimum refractive index in the biaxial patterned retarder.

In the present invention, a front retardation (Re) is desirably between 0 and 10nm. When the front retardation is more than 10nm, the light leakage or the picture quality deterioration can be occurred in displays because the phase difference between lights which has passed through the first and the second patterned area is unnecessarily bigger than a desired level.

For example, in the case of three-dimensional display, the phases of linearly polarized lights which pass through the patterned retarder are respectively shifted into ±λ/4 to be converted into either right-circular polarization or left-circular polarization by the first or second patterned area. However, when a front retardation of more than 10nm is added to the each of the converted lights, the light leakage or the picture quality deterioration is occurred because the polarization is converted into elliptical polarization, not circular polarization.

In the present invention, it is desirable to use an adhesive layer with no front retardation while maintaining the above-mentioned refractive index range. However, considering commonly used permanent or non-permanent adhesives and manufacturing process, it is desirable to use permanent or non-permanent adhesives which can cause minimum effects on the front retardation and refractive index of the patterned retarder and the polarizer.

In the present invention, an UV hardening permanent adhesive or an UV hardening non-permanent adhesive can be used as an adhesive layer. The UV hardening permanent adhesive or an UV hardening non-permanent adhesive (for example, pressure sensitive adhesive) are commonly used in the field of the present invention and not limited to any specific type.

For example, the adhesive layer can include one selected from the group consisting of acrylic copolymer, natural rubber, styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer, styrene-ethylenebuthylene-styrene block copolymer, styrene-butadiene rubber, polybutadiene, polyisoprene, polyisobutylene, butyl rubber, chloroprene rubber, and silicone rubber.

Methods for forming a patterned retarder is not limited in the present invention, and any commonly used methods can be used. An example of the method is aligning liquid crystals on a polymer film and forming patterns using photo resist.

The method is usually carried out as follows: forming alignment layer by coating alignment solution on a transparent base layer, rubbing, photo resist process, rubbing photo resist strip, liquid crystal coating, and hardening.

A non-birefringent material or low birefringent material can be used as the transparent base layer. For example, glass, acryl, or non-extendable polycarbonate, etc. can be used.

The alignment layer is for aligning liquid crystals, and a commonly used rubbing polymer can be used for the alignment layer.

Coating methods are not limited to any specific ones, and any commonly used methods which can form a uniform coating layer may be used. Specifically, spin coating, wire bar coating, micro gravure coating, dip coating, or spray coating methods can be used.

The thickness of the alignment layer after drying is desirably between 800 and 200 Å. It is unable to have enough alignment regulation force when the thickness is less than 800 Å, and it is hard to have coating uniformity when the alignment when the thickness is more than 2000 Å.

Next, alignment directions are formed on the alignment layer by rubbing.

Next, put a master film on a photo resist and expose and develop the photo resist with the black part of the master film as a mask. Then, a part of the photo resist which is corresponding to the black part remains. Here, the width and distance between the remaining photo resists is different according to pixel pitches of panels such as LCDs and PDPs to which the patterned layer is applied.

Next, perform rubbing using the remaining photo resist as a mask. A part of the alignment layer which is protected by the photo resist remains the original alignment direction, while the direction of the other part which is not protected by the photo resist is changed to another alignment direction. After the second rubbing is completed, the photo resist which is used as a mask is removed by soaking in etching solution.

Next, complete the patterned retarder by coating and hardening liquid crystals.

The patterned retarder laminated on the transparent base layer includes a first hardened liquid crystal layer with a first alignment direction and a second hardened liquid crystal layer with a second alignment direction. The first and second alignment directions are directions of extraordinary axes, so lights which pass through the first and second patterned area have phase differences.

The composite polarizing plate according to the present invention can include a transparent base layer laminated on the patterned retarder. The transparent base layer protects the surface of the patterned retarder.

As described above, when the transparent base layer is used when manufacturing the patterned retarder, the transparent base layer can be a base film or plate for forming the patterned retarder, and can also be a protection film for protecting the patterned retarder at the top of the patterned retarder. Moreover, the transparent base layer can be removed considering necessary conditions, such as the intensity of the patterned retarder, etc.

The composite polarizing plate may additionally include one or more functional layers laminated on the patterned retarder, the functional layer is selected from the group consisting of permanent adhesive layer or non-permanent adhesive layer, protection layer, retardation layer, anti-dazzling layer, anti-reflection layer, antistatic layer, and hard-coating layer.

The permanent or non-permanent adhesive layer is for gluing other functional layers. The protection layer is a layer for preventing crack or damage of the polarizing plate or the patterned retarder. The retardation layer is for additionally controlling retardation. The anti-dazzling layer is a layer having micro ruggedness which is formed by sandblasting, embossing process, or spraying solution containing particles. The anti-reflection layer is for preventing decline of visibility due to reflection of external lights, and includes metallic oxides which are formed by deposition or sputtering. The antistatic layer is for preventing dust due to static electricity, and is formed by UV hardening polymers including antistatic materials. The hard-coating layer for preventing crack or damage of the surface of the polarizing plate, and formed by acrylic or siliconic UV hardening polymers.

The composite polarizing plate according to the present invention which includes a polarizing plate and a patterned retarder can be included in a display apparatus.

Any display apparatuses which is capable of displaying three-dimensional images can be the above-mentioned display apparatus. For example, the display apparatus may include reflective or transreflective liquid crystal display (LCD), plasma display panel (PDP), organic EL display (OLED), etc.

The composite polarizing plate according to the present invention can be used as a substitute for a polarizing plate and a patterned retarder of the prior art.

For example, a reflective liquid crystal display as shown in FIG. 3 can include a backlight unit 410; a lower polarizing plate 310 that converts light which are emitted from the backlight unit into polarized light; a liquid crystal panel 200 that the polarized light is entered; an upper polarizing plate 110 that detects information of the light which has passed through the liquid crystal panel; a patterned retarder 120 that converts light which has passed through the upper polarizing plate 110 into two different polarized lights according to patterns.

FIG. 4 illustrates an example of a display apparatus shown in FIG. 3 further including a transparent base layer 140 at the outermost layer.

Furthermore, for example, a reflective liquid crystal display as shown in FIG. 5 can include a backlight unit 410; a lower polarizing plate 310 that converts light which are emitted from the backlight unit into polarized light; a retardation layer 320 that shift the phase of the polarized light; a liquid display panel 200 receives signals provides information to the phase shifted polarized light according to the received signals; a reflection layer 240 that reflects light which has passed through the liquid display panel; an upper polarizing plate 110 that detects information of the light which has passed through the liquid crystal panel; a patterned retarder 120 that converts light which has passed through the upper polarizing plate 110 into two different polarized lights according to patterns. In this case, the reflected polarized light passes through the liquid display panel while maintaining same phase difference.

FIG. 6 illustrates an example of a display apparatus shown in FIG. 5 further including a transparent base layer 140 at the outermost layer.

Furthermore, the composite polarizing plate according to the present invention can be applied to a plasma display panel (PDP), or an organic EL display (OLED) shown in FIG. 7, and the composite polarizing plate can additionally include a transparent base layer 140 at the outermost layer.

A principle for implementing three-dimensional images in a display device including the composite polarizing plate according to the present invention is same as the prior art which uses conventional polarizing plate and patterned retarder.

The composite polarizing plate according to the present invention can be applied to a three-dimensional image display system. As shown in FIG. 9, the system can include a liquid crystal display and a pair of polarization eyeglasses 70. The liquid crystal display includes a polarizing plate 60 having a first image display area 61 and a second image display area 62, and a patterned retarder 63 having a first patterned area 64 that converts polarization of light which has passed through the first image display area 61 and a second patterned area 65 that convert polarization of light which has passed through the second image display area 62. The pair of polarization eyeglasses includes a first polarization area 71 and a second polarization area 72 that convert polarization of light which has passed through the patterned retarder into linear polarization, and left and

right lenses

74 and 75.

FIG. 10 illustrates a principle of implementing three-dimensional images using the system shown in FIG. 9. A white light which is emitted from a light source is converted into linearly polarized light when passing through

polarizing plates

10 and 11, and the linearly polarized light is converted into circularly polarized light when passing through patterned retardation layers 20 and 21 of the liquid crystal display. The circularly polarized light is either allowed to pass or blocked by

retardation layers

30 and 31 and

polarizing plates

40 and 41 of the pair of polarization eyeglasses.

The present invention can be understood according to examples below, the examples are only exemplary and not limiting the scope of the present invention which is defined by the appended claims.

EXAMPLES AND COMPARATIVE EXAMPLES

As shown in FIG. 1, a composite polarizing plate including a polarizing plate 110, an adhesive layer 130 having acrylic copolymer, and a patterned retarder 120 (Zeon, COP) stacked in this order is manufactured. The size of the composite polarizing plate is 10cm*10cm, and an extraordinary refractive index (n_e) and an ordinary refractive index (n_o) of the patterned retarder are shown in Tables 1 through 3.

Tables 1 through 3 are reflection ratios with respect to refractive indices of the adhesive layer considering the extraordinary refractive index (n_e) and the ordinary refractive index (n_o) of the patterned retarder. For your information, in Table 1, difference between reflection ratios |R_o-R_e| can be seen as difference between penetration (brightness) ratios |T_o-T_e|, because R_e=1-T_e, and R_o=1-T_o.

Table 1

Table 2

Table 3

Tables 4 through 6 are test results of visibility of liquid crystal displays including composite polarizing plates which have properties shown in Tables 1 through 3. The tests were performed by experts in testing visibility of LCDs. The visibilities of examples or comparative examples are compared with other examples or comparative examples in a same Table.

◎: Very Good ○: Good △: Improved Ⅹ: Bad

Table 4

Table 5

Table 6

As shown in Tables 4 through 6, it is confirmed that when refractive index (N) of an adhesive layer of the present invention is between an ordinary refractive index (n_o) and extraordinary refractive index (n_e) of a patterned retarder, moire patterns are eliminated and visibility test results are excellent.

Furthermore, the results show that when the refractive index of the adhesive layer gets closer to the value of Ne, the arithmetic mean of the ordinary refractive index and the extraordinary refractive index, the visibility test result gets better. Especially, the best results can be obtained when a difference between the refractive index of the adhesive layer and an arithmetic mean of the ordinary refractive index and the extraordinary refractive index (Ne) is less than 1%.

Claims

A composite polarizing plate comprising a patterned retarder which is laminated on a polarizing plate by an adhesive layer, wherein a refractive index (N) of the adhesive layer satisfies the following equation (1):

min(n_o, n_e) ≤ N ≤ max (n_o, n_e) (1)

wherein n_o represents an ordinary refractive index of the patterned retarder, n_e represents an extraordinary refractive index of the patterned retarder, min(n_o, n_e) represents the smaller between n_o and n_e, and max(n_o, n_e) represents the greater between n_o and n_e, respectively.
The composite polarizing plate of claim 1, wherein the refractive index (N) satisfies the following equation (2):

min(n_o, n_e) + | n_o - n_e| / 3 ≤ N ≤ max(n_o, n_e) - | n_o - n_e| / 3 (2)

wherein n_o represents an ordinary refractive index of the patterned retarder, n_e represents an extraordinary refractive index of the patterned retarder, min(n_o, n_e) represents the smaller between n_o and n_e, and max(n_o, n_e) represents the greater between n_o and n_e, respectively.
The composite polarizing plate of claim 1, wherein the refractive index (N) satisfies the following equation (3):

0.99Ne ≤ N ≤ 1.01Ne (3)

wherein Ne = (n_o + n_e) / 2, n_o represents an ordinary refractive index of the patterned retarder, and n_e represents an extraordinary refractive index of the patterned retarder, respectively.
The composite polarizing plate of claim 1, wherein the refractive index (N) satisfies the following equation (4):

0.994Ne ≤ N ≤ 1.006Ne (4)

wherein Ne = (n_o + n_e) / 2, n_o represents an ordinary refractive index of the patterned retarder, and n_e represents an extraordinary refractive index of the patterned retarder, respectively.
The composite polarizing plate of any one of claims 1-4, further comprising a transparent base layer which is laminated on the patterned retarder.
The composite polarizing plate of any one of claims 1-4, wherein the adhesive layer is either a permanent adhesive layer or a pressure sensitive adhesive layer.
The composite polarizing plate of any one of claims 1-4, wherein a front retardation (Re) of the adhesive layer is between 0 and 10nm.
The composite polarizing plate of any one of claims 1-4, wherein the adhesive layer comprises an UV hardening permanent adhesive or an UV hardening pressure sensitive adhesive.
The composite polarizing plate of any one of claims 1-4, wherein the adhesive layer comprises at least one selected from the group consisting of acrylic copolymer, natural rubber, styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer, styrene-ethylenebuthylene-styrene block copolymer, styrene-butadiene rubber, polybutadiene, polyisoprene, polyisobutylene, butyl rubber, chloroprene rubber, and silicone rubber.
The composite polarizing plate of any one of claims 1-4, wherein a direction of an extraordinary axis of one patterned area of the patterned retarder is different from that of the other patterned area of the patterned retarder.
The composite polarizing plate of any one of claims 1-4, wherein a polarization direction of a light which has entered the patterned retarder is between directions of extraordinary axes of two patterned areas of the patterned retarder.
The composite polarizing plate of any one of claims 1-4, wherein one or more functional layers are laminated on the patterned retarder, the functional layer is selected from the group consisting of permanent adhesive layer or pressure sensitive adhesive layer, protection layer, retardation layer, anti-dazzling layer, anti-reflection layer, antistatic layer, and hard-coating layer.
The composite polarizing plate of any one of claims 1-4, wherein the polarizing plate is a laminated structure including a polarizer, and at least one of the functional films selected from the group consisting of a polarizer protection film and a retardation film laminated on one side or both sides of the polarizer.
A three-dimensional display apparatus comprising the composite polarizing plate of any one of claims 1-4.
The three-dimensional display apparatus of claim 14, wherein the three-dimensional display apparatus is a liquid crystal display, a plasma display, or an organic EL display.