KR20180057586A - Polarizing plate and image display device including the same - Google Patents

Abstract

The present invention relates to a polarizing plate and an image display device including the same. The polarizing plate of the embodiments of the present invention comprises: a polarizer; and a reciprocal dispersibility quarter-wave retardation layer stacked on a surface of a viewer side of the polarizer and having a rate (R0(450nm)/R0(550nm)) of an in-plane retardation value (R0(550nm)) at a wavelength of 450nm to an in-plane retardation value (R0(550nm)) at a wavelength of 550 nm is 0.9 or less. Through the reciprocal dispersibility quarter-wave retardation layer, image deterioration due to an external polarizing member and external light can be prevented.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing plate and an image display device including the polarizing plate.

The present invention relates to a polarizing plate and an image display apparatus including the same. More particularly, the present invention relates to a polarizing plate including a polarizer and a retardation layer, and an image display device including the same.

As the information society has developed in recent years, demands for the display field have been presented in various forms. For example, various flat panel display devices, such as a liquid crystal display device, a plasma display panel device, and a liquid crystal display device, which have features of thinning, light weight, and low power consumption, An electro luminescent display device, an organic light-emitting diode display device, and the like have been studied.

Since the external light is reflected or scattered on the image display surface of the display device when external light is present in the display device, the original image displayed on the display device is not easily seen. Therefore, an optical film including a retardation film and a polarizer can be incorporated into the display device for improving image or image quality.

In addition, for example, when a sunglass is worn and an image displayed on the image display device is observed, the sunglass acts as a polarizing plate, and the color and brightness of the image are changed according to the rotation of the screen, .

Therefore, there is a need for an optical design that can prevent image deterioration caused by external light and an external polarization member such as a sunglass. For example, Korean Patent Laid-Open Publication No. 2013-0110204 discloses a polarizing plate for realizing an image with high contrast. The optical design considering the external light-deflecting member as described above is not considered.

Korean Patent Publication No. 10-2013-0110204

An object of the present invention is to provide a polarizing plate improved in optical reliability and image reproducibility.

An object of the present invention is to provide an image display device including the above polarizing plate and having improved optical reliability and image reproducibility.

1. polarizer; And a ratio R ₀ (450 nm) of an in-plane retardation value (R ₀ (450 nm)) at a wavelength of 450 nm to the in-plane retardation value (R ₀ (550 nm) ) / R ₀ (550 nm)) of 0.9 or less.

2. The polarizer according to item 1 above, wherein R _o (450 nm) / R _o (550 nm) of the reversibly dispersing quadruple phase retardation layer is less than 0.9.

3. The polarizer of claim 1, further comprising a quarter wave retardation layer and a positive C plate laminated sequentially from the panel side of the polarizer.

4. The polarizing plate according to 3 above, wherein said quadrature wavelength retardation layer has a reversible dispersibility.

5. The polarizer of claim 1, further comprising a half-wave retardation layer and a quarter-wave retardation layer which are sequentially laminated from the panel side of the polarizer.

6. The polarizer of claim 1, further comprising a protective film bonded to at least one of the upper surface or the lower surface of the polarizer.

7. A window laminate comprising a polarizing plate as claimed in any one of claims 1 to 6.

8. An image display device comprising the polarizing plate of any one of items 1 to 6 above.

9. The image display apparatus of claim 8, comprising an organic light emitting diode element disposed under the polarizing plate.

According to embodiments of the present invention, a reverse dispersive quadruple phase retardation layer having a predetermined range of in-plane retardation value ratio on the polarizer can be formed. Accordingly, when an image display apparatus is viewed through an external polarization member such as a sunglass, an image having uniform color and brightness can be realized even when the screen is rotated or the screen is moved.

1 is a schematic cross-sectional view showing a polarizing plate according to exemplary embodiments.
Figures 2 and 3 are schematic cross-sectional views illustrating a polarizer according to exemplary embodiments.
4 is a schematic cross-sectional view showing a window laminate and an image display device according to exemplary embodiments;
5 to 8 are schematic views showing alignment axes of absorption axes of a polarizer and a slow axis of a quadruple wavelength retardation layer in accordance with rotation of a sunglass in an experimental example.

According to embodiments of the present invention, there is provided a polarizing plate including a polarizer and a reverse dispersed quadruple wavelength retardation layer disposed on the viewer side of the polarizer, and excellent in image reproducibility for external light and external polarizing members. Further, an image display device including the above polarizing plate is provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. Should not be construed as limiting

1 is a schematic cross-sectional view showing a polarizing plate according to exemplary embodiments.

1, the polarizer 100 may include a polarizer 110 and a depolarized quadrature wavelength (λ / 4) retardation layer 120 laminated on the polarizer 110.

The polarizer 110 may be, for example, a film in which a dichroic dye is adsorbed and oriented on a stretched polyvinyl alcohol-based resin film. The polyvinyl alcohol-based resin can be obtained by saponifying a polyvinyl acetate-based resin.

Examples of polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, or copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with the vinyl acetate include an acrylamide monomer having a small unsaturated carboxylic acid type, an unsaturated sulfonic acid type, an olefin type, a vinyl ether type, and an ammonium group.

The polyvinyl alcohol resin may be modified. For example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The degree of saponification of the polyvinyl alcohol-based resin may be 85 to 100 mol%, preferably 98 mol% or more. The polymerization degree of the polyvinyl alcohol-based resin may be about 1,000 to 10,000, and preferably 1,500 to 5,000.

The above-mentioned polyvinyl alcohol-based resin film can be used as the original film of the polarizer 110. The thickness of the original film may be, for example, 10 to 150 mu m.

In some embodiments, the polarizer 110 may be formed by a process comprising continuously uniaxially stretching a polyvinyl alcohol-based film in an aqueous solution, dyeing and adsorbing with a dichroic dye, treating with an aqueous solution of boric acid, ≪ / RTI >

A protective film may be formed on at least one side of the polarizer 110. In some embodiments, the first protective film 112 and the second protective film 114 may be formed on the bottom and top surfaces of the polarizer 110, respectively.

The protective films 112 and 114 may include a resin film excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropic properties. For example, the protective films 112 and 114 may be acrylic resin films such as polymethyl (meth) acrylate and polyethyl (meth) acrylate; Polyester based resin films such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate and polybutylene terephthalate; Cellulose-based resin films such as diacetylcellulose and triacetylcellulose; A polyolefin-based resin having a polyethylene, polypropylene, cyclo- or norbornene structure, and a polyolefin-based resin film such as an ethylene-propylene copolymer.

In some embodiments, the protective films 112 and 114 may be attached to the polarizer 110 via a point-adhesive layer. For example, the pressure-sensitive adhesive layer may be formed by coating a photocurable pressure-sensitive adhesive composition on the adherend surface of the polarizer 110 or the protective films 112 and 114 and attaching the pressure-sensitive adhesive composition to each other, .

The photocurable adhesive composition may include a photopolymerizable compound, a photopolymerization initiator, and a solvent.

The photopolymerizable compound may include a photo-radical polymerizable compound or a photo-cationic polymerizable compound. Preferably, the photo-radical polymerizable compound or photo-cationic polymerizable compound may be used together.

Examples of the photopolymerization initiator include photo radical polymerization initiators such as acetophenone, benzophenone, thioxanthone, benzoin and benzoin alkyl ether; And / or a photocationic polymerization initiator such as an aromatic diazonium salt, an aromatic sulfonium salt, an aromatic iodo aluminum salt, a benzoin sulfonic acid ester compound and the like.

The primer treatment, the plasma treatment, the corona treatment, and the saponification (alkali) surface treatment may be performed on the adhered surface of the polarizer 110 and / or the protective films 112 and 114 have.

According to exemplary embodiments, a backscattered quadrature phase retarder layer 120 may be disposed on the viewer side of the polarizer 100.

In the present specification, the "viewing side" refers to a side adjacent to a direction in which the user views the polarizing plate 100 when the polarizing plate 100 is used in an image display apparatus. For example, the opposite side of the viewer side can face the display panel of the image display apparatus. Hereinafter, the opposite side of the viewer side will be referred to as "panel side ".

For example, the upper surface of the polarizer 110 or the second protective film 114 may face the viewing side, and the bottom surface of the polarizer 110 or the first protective film 112 may face the panel side.

The inversely dispersed quadrature phase retardation layer 120 outputs the phase lag by 1/4 with respect to the component that vibrates the incident light [Lambda] in the slow axis direction. Accordingly, it is possible to suppress reflection of light incident from the outside of the image display apparatus. Further, the light emitted from the image display device can be converted into circularly polarized light.

The term "slow axis" as used in this application may refer to an optical axis where a phase retardation or phase difference occurs when light passes through the film.

In the exemplary embodiment, reverse dispersion quadrant wavelength retardation layer retardation value side at a wavelength of 550nm of _{(120) (R 0 (550nm} )) retardation value plane in contrast 450nm wavelength (R ₀ (450nm)) The ratio (R _o (450 nm) / R _o (550 nm)) may be about 0.9 or less. Preferably, R _o (450 nm) / R _o (550 nm) of the inversely dispersed quadrature wavelength retardation layer 120 may be less than 0.9. In one embodiment, for example, R _o (450 nm) / R _o (550 nm) of the inverse dispersive quadrature phase retarder layer 120 may range from about 0.7 to 0.9.

In the in-plane retardation value ratio range, brightness and color change due to screen rotation can be effectively prevented even if an external polarization member such as a sunglass is worn and an image is observed.

For example, the in-plane retardation value (R ₀ ) of the retardation layer can be calculated by the following equation (1).

[Equation 1]

_{R 0 = (n x -n y} ) × d

N _x, n _y in the Formula 1 is to say x the vibration direction of the two-dimensional refractive index is maximized is a two-dimensional refractive index of the film, that the refractive index of the light oscillating in the direction of n _x and, n _x and n _y are each Nx ≥ ny, and d represents the thickness of the film.

The inversely dispersed quadrature phase retardation layer 120 may be formed of, for example, a film type or a liquid crystal coating layer. The film type retardation layer can be obtained, for example, by orienting the polymer film in the uniaxial direction, the biaxial direction, or other suitable method of the present invention. For example, the polymer film may be formed of any one selected from the group consisting of a cyclic polymeric olefin (COP), a polycarbonate, a polyester, a polysulfone, a polyether sulfone, a polystyrene, a polyolefin, a polyvinyl alcohol, a cellulose acetate, Methacrylate-based, polyvinyl chloride-based, polyacrylate-based, and polyamide-based polymers.

The liquid crystal coating layer type retardation layer can be produced through the use of a reactive liquid crystal composition comprising a nematic or a smectic liquid crystal material. For example, the reactive liquid crystal composition can be prepared by coating on a substrate, orienting it in a plane orientation, and exposing it to heat or ultraviolet light to induce polymerization

In some embodiments, the inversely dispersed quadrature phase retarder layer 120 may be attached to the polarizer 110 or the second protective film 114 via a point-adhesive layer.

Figures 2 and 3 are schematic cross-sectional views illustrating a polarizer according to exemplary embodiments. A detailed description of the substantially same or similar construction or material as that described with reference to Fig. 1 is omitted.

Referring to FIG. 2, the polarizing plate 102 may include a quarter-wave retardation layer 130 and a positive C-plate 140 (hereinafter abbreviated as + C plate) arranged on the panel side.

According to exemplary embodiments, the quarter wave retardation layer 130 and the + C plate 140 can be sequentially arranged from the bottom surface of the polarizer 110 or sequentially from the first protective film 112.

The quarter wavelength retardation layer 130 may have reverse wavelength dispersion, flat wavelength dispersion, or regular wavelength dispersion.

For example, the value of Ro (450 nm) / Ro (550 nm) may range from about 0.7 or more to less than 0.99 when the quadrature wavelength retardation layer 130 has reverse wavelength dispersion. For example, the value of Ro (450 nm) / Ro (550 nm) may range from about 0.99 to less than 1.01 when the quaternary wavelength retardation layer 130 has flat wavelength dispersibility. For example, the value of Ro (450 nm) / Ro (550 nm) may range from about 1.01 to 2 when the quadruple wavelength retardation layer 130 has a regular wavelength dispersion. Preferably, the quarter wave retardation layer 130 may have reverse wavelength dispersion properties.

The quadrature wavelength retardation layer 130 may be formed of a film type or a liquid crystal coating layer, and may include substantially the same or similar material, for example, the above-mentioned undoped quarter wavelength retardation layer 120.

In one embodiment, the quarter wave retardation layer 130 may be bonded to the polarizer 110 or the first protective film 112 via an adhesive layer.

The polarizing plate 102 further includes a + C plate 140 below the quartic wave retardation layer 130. For example, it is possible to improve the color quality of reflection in the oblique direction with respect to the viewing side direction, thereby further improving the image quality.

The + C plate 140 refers to a retardation plate in which the optical axis exists in the vertical direction of the surface, and includes, for example, a case where the refractive index ratio Nz includes a film having negative infinity and substantially equal to or less than -6 . Nz can represent refractive indices perpendicular to the plane defined by n _x and n _y (thickness direction of the film).

The + C plate 140 may be prepared by orienting the polymer film in an appropriate manner, or may be prepared by coating the polymerizable cholesteric liquid crystal compound on one side of the substrate, orienting the film in a certain direction, and then curing.

When a polymerizable cholesteric liquid crystal compound is used, a zero retardation film can be used as a substrate. The zero-retardation film can refer to a film in which no substantial retardation does not occur even when light is transmitted.

In one embodiment, the + C plate 140 may be bonded to the quarter wave retardation layer 130 via a point-adhesive layer.

3, the polarizing plate 104 may include a half wavelength (λ / 2) retardation layer 150 and a quarter wavelength retardation layer 160 disposed on the panel side.

For example, the half-wave retardation layer 150 and the quarter-wave retardation layer 160 can be sequentially arranged from the bottom surface of the polarizer 110 or the first protective film 112.

The half-wave retardation layer 150 and the quarter-wave retardation layer 160 may have reverse wavelength dispersion, flat wavelength dispersion, or regular wavelength dispersion.

The half-wave retardation layer 150 and the quarter-wave retardation layer 160 may be formed of a film type or a liquid crystal coating layer. For example, the above-described undistributed quarter-wave retardation layer 120 may include substantially the same or similar material .

The half-wave retardation layer 150 and the quarter-wave retardation layer 160 respectively output a phase delay of 1/2 and 1/4 with respect to the component that vibrates the incident light λ in the slow axis direction. Thus, reflection of light incident from the outside of the display device can be suppressed more effectively.

By way of non-limiting example, the slow axis of the half-wave retardation layer 150 is substantially about 15 ^° with respect to the transmission axis of the polarizer 110, and the slow axis of the quarter-wave retardation layer 160 is about the transmissive axis of the polarizer 110 It may be substantially arranged to achieve a 75 ^o slope. Substantially 15 ^° and 75 ° can mean up to about ± 5 ° around each angle.

As the polarizing plate 104 includes the laminated structure of the half-wave retardation layer 150 and the quarter-wave retardation layer 160, a phase retardation effect is substantially realized over the entire visible light region and an image A display device can be implemented.

For example, the half-wave retardation layer 150 may be bonded to the polarizer 110 or the first protective film 112 through a point-adhesive layer. An adhesive layer may also be interposed between the half-wave retardation layer 150 and the quarter-wave retardation layer 160.

4 is a schematic cross-sectional view showing a window laminate and an image display device according to exemplary embodiments;

The window laminate 250 may include a window substrate 230, a polarizer 210, and a touch sensor 200.

The window substrate 230 includes, for example, a hard coating film, and in one embodiment, a light shielding pattern 235 may be formed on the peripheral portion of one side of the window substrate 230. The light-shielding pattern 235 may include, for example, a color printing pattern, and may have a single layer or a multi-layer structure. The bezel portion or the non-display region of the image display apparatus can be defined by the shielding pattern 235. [

The polarizer 210 may include a reverse dispersion quadrature phase retarder layer disposed on the side of the window substrate 230 on the polarizer, according to the above-described exemplary embodiments. As described above, the inverse dispersive quadruple phase retarder layer may have a value of R ₀ (450 nm) / R ₀ (550 nm) of 0.9 or less. Accordingly, even when a sunglass is worn and the screen is observed, for example, color and brightness variations due to the rotation of the screen can be suppressed.

The polarizer 210 may be directly bonded to the one side of the window substrate 230 or may be attached through the first adhesive layer 220. In one embodiment, the polarizing plate 210 is manufactured in a roll-to-roll fashion, cut to a predetermined size, and included in the window laminate 250 or the image display device.

The touch sensor 200 may be included in the window laminate 230 in the form of a film or a panel. In one embodiment, the touch sensor 200 may be coupled to the polarizer 210 via a second point-of-use adhesive layer 225.

4, the window substrate 230, the polarizing plate 210, and the touch sensor 200 may be disposed in this order from the viewer's side. In this case, since the sensing electrodes of the touch sensor 200 are disposed below the polarizer 210, the phenomenon of pattern visibility can be more effectively prevented. In one embodiment, the window substrate 230, the polarizing plate 200, and the optical film 210 may be arranged in order from the user's viewing side.

The image display device may include the above-described window stack 250 coupled to the display panel 360 and the display panel 360. According to exemplary embodiments, the image display device may be an organic light emitting diode (OLED) display device.

The display panel 360 includes a pixel electrode 310, a pixel defining layer 320, a display layer 330, an opposite electrode 340, and an encapsulation layer 350 disposed on the panel substrate 300 .

The panel substrate 300 may comprise a soluble resin material such as glass or polyimide. On the panel substrate 300, a pixel circuit including a thin film transistor (TFT) is formed, and an insulating film covering the pixel circuit can be formed. The pixel electrode 310 may be electrically connected to the drain electrode of the TFT, for example, on the insulating film.

The pixel defining layer 320 may be formed on the insulating layer to define the pixel region by exposing the pixel electrode 310. A display layer 330 is formed on the pixel electrode 310, and the display layer 330 may include, for example, an organic light emitting layer.

The counter electrode 340 may be disposed on the pixel defining layer 320 and the display layer 330. The counter electrode 340 may be provided, for example, as a common electrode or a cathode of an image display apparatus. An encapsulation layer 350 for protecting the display panel 360 may be laminated on the counter electrode 340.

In some embodiments, the display panel 360 and the window laminate 250 may be bonded via the lacquer layer 260.

Hereinafter, exemplary embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the present invention is not limited to the accompanying claims, It will be apparent to those skilled in the art that various changes and modifications can be made in the embodiments within the scope of the claims, and such variations and modifications are within the scope of the appended claims.

Experimental Example

Production of Polarizer

(PE60, KURARAY) having a degree of saponification of 99.9% or more was immersed in water (deionized water) at 30 DEG C for 2 minutes and swelled. Then, 1.25 mM / L of iodine and 1.25 wt% of potassium iodide, And dipped in a dyeing solution at 30 占 폚 containing 0.0005% by weight for 4 minutes. Specifically, in the swelling and dyeing steps, the stretching was performed at a stretching ratio of 1.3 times and 1.4 times, respectively, and the stretching ratio to the dyeing bath was 1.82 times.

Subsequently, it was immersed (crosslinked first) for 30 seconds in an aqueous solution for crosslinking at 50 DEG C containing 10% by weight of potassium iodide and 3.7% by weight of boric acid, and stretched at a draw ratio of 2, while being crosslinked. Thereafter, the resultant was immersed in a crosslinking aqueous solution at 50 DEG C containing 10 wt% of potassium iodide and 3.7 wt% of boric acid for 20 seconds (second crosslinking), and was stretched at a draw ratio of 1.5 times while being crosslinked (the accumulation of the first crosslinking and the second crosslinking The stretching ratio is 3 times). The total cumulative stretching ratio of the swelling, dyeing and crosslinking steps was adjusted to be 5.46 times. The crosslinked polyvinyl alcohol film was dried in an oven at 70 DEG C for 4 minutes to prepare a polarizer. A TAC protective film was attached to the upper and lower surfaces of the polarizer to prepare a polarizing plate.

Examples and Comparative Examples

Material (film or liquid crystal) quadrant wavelength retardation layer on a polarizing plate prepared as above, the wavelength dispersion, and R ₀ (450nm) / R ₀ four minutes wavelength retardation layer (550nm) is different to the 45 ^o about the polarizer absorption axis And the polarizing plates of Examples and Comparative Examples were formed as shown in Table 1 so as to be aligned at an oblique slow axis. On the other hand, in Comparative Example 1, the formation of the quarter wavelength retardation layer was omitted.

Experimental Example

The quarter wavelength retardation layer side of the polarizing plate of Examples and Comparative Examples was observed by wearing polarized sunglasses. In the case of Comparative Example 1, the TAC protective film side formed on the upper surface of the polarizing plate was observed.

More specifically, (see Fig. 5) polarized sunglasses the 0 ^o, 45 ^o (see Fig. 6), 90 ^o (see Fig. 7) and 135 ^o (see Fig. 8), four times the color coordinates (CIE color system) during each rotation, while rotating Xy and a luminance deviation DELTA Lv (measuring instrument: CA-310, Konica Minolta) were measured. The evaluation results are shown together in Table 1 below.

material Dispersion R ₀ (450 nm)
/ R ₀ (550 nm) Xy
Xy
ratio
(Compared to Comparative Example 1) △ Lv △ Lv
ratio
(Compared to Comparative Example 1) Example 1 film Reverse dispersion 0.83 0.01 0.36 23.40 0.03 Example 2 Liquid crystal Reverse dispersion 0.88 0.02 0.83 44.60 0.05 Example 3 Liquid crystal Reverse dispersion 0.86 0.02 0.69 53.10 0.06 Example 4 Liquid crystal Reverse dispersion 0.83 0.01 0.44 61.50 0.07 Comparative Example 1 (Ref) - - - 0.03 1.00 863.58 1.00 Comparative Example 2 film Positive dispersion 1.01 0.06 2.36 389.00 0.45 Comparative Example 3 film flat 0.91 0.03 1.20 81.70 0.09 Comparative Example 4 Liquid crystal Reverse dispersion 0.92 0.04 1.50 41.50 0.05

Referring to Table 1, a reduced color and brightness difference was obtained despite the screen rotation by laminating the inverse dispersive quadrature phase retarder layer on the polarizer and adjusting the R ₀ (450 nm) / R ₀ (550 nm) value to less than 0.9 .

110: polarizer 112: first protective film
114: second protective film 120: reverse dispersive quartic wave retardation layer
130, 160: quarter wavelength phase difference layer
140: + C plate 150: Half wavelength retardation layer

Claims (9)

A polarizer; And
Is laminated on the viewer side surface of the polarizer, a retardation value side at a wavelength of 550nm (R ₀ (550nm)) the ratio of the retardation values surface in contrast 450nm wavelength _{(R 0 (450nm)) (} R 0 (450nm) / R ₀ (550 nm)) is 0.9 or less.
The polarizing plate according to claim 1, wherein R _o (450 nm) / R _o (550 nm) of the inverse-dispersive quadruple phase retardation layer is less than 0.9.
The polarizer of claim 1, further comprising a quarter wave retardation layer and a positive C plate sequentially laminated from the panel side of the polarizer.
4. The polarizer of claim 3, wherein the quadrature wavelength retardation layer has a reversibly dispersing property.
The polarizer of claim 1, further comprising a half-wave retardation layer and a quarter-wave retardation layer laminated sequentially from the panel side of the polarizer.
The polarizer of claim 1, further comprising a protective film bonded to at least one of an upper surface or a lower surface of the polarizer.
A window laminate comprising the polarizer of any one of claims 1 to 6.
An image display device comprising the polarizing plate of any one of claims 1 to 6.
The image display apparatus according to claim 8, comprising an organic light emitting diode element disposed under the polarizing plate.

Images