POLARIZING PLATE, METHOD FOR PREPARING THE SAME, AND OPTICAL DISPLAY APPARATUS INCLUDING THE SAME

• US 20140168769A1
• Filed: 12/13/2013
• Published: 06/19/2014
• Est. Priority Date: 12/17/2012
• Status: Active Grant

• Current Assignee: Cheil Industries Incorporated (Samsung Group)
• Original Assignee: Cheil Industries Incorporated (Samsung Group)
• Inventors: Seo, Eun Kyeong, Ko, Mun Bo, Kim, Min Jung, Kim, Yong Woon, Park, Ki Ho, Lee, Jung Kyu
• Granted Patent: US 9,261,636 B2
• Time in Patent Office: Days
• US Class Current: 359/489.07
• CPC Class Codes: G02B 5/3083 Birefringent or phase retarding elements G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001
• CPC Class Codes: Y10T 156/10 Methods of surface bonding and/or assembly therefor

Abstract

A polarizing plate includes a polarizer having absorption and transmission axes, a protective film on an upper surface of the polarizer, a half-wavelength (λ/2) retardation film on a lower surface of the polarizer, an adhesive layer on a lower surface of the half-wavelength (λ/2) retardation film, and a quarter-wavelength (λ/4) retardation film on a lower surface of the adhesive layer. An absolute orthogonal b-coordinate value based on a CIELAB color coordinate system of the polarizing plate may be approximately 3 or less when the polarizing plate is stacked with a reference polarizing plate having a degree of polarization of at least 99.9% such that an angle between the absorption axis of the polarizer and an absorption axis of a polarizer of the reference polarizing plate or an angle between the transmission axis of the polarizer and a transmission axis of the polarizer of the reference polarizing plate is 90°.

Claims

1. A polarizing plate, comprising:

a polarizer,

wherein an absolute orthogonal b-coordinate value based on a CIELAB color coordinate system is approximately 3 or less when the polarizing plate is stacked with a reference polarizing plate having a degree of polarization of at least 99.9% such that an angle between the absorption axis of the polarizer and an absorption axis of a polarizer of the reference polarizing plate is 90°

.

2. The polarizing plate according to claim 1, wherein the polarizing plate comprises the polarizer, a protective film formed on an upper side of the polarizer, a λ

/2 retardation film formed on a lower side of the polarizer, and a λ

/4 retardation film formed on a lower side of the λ

/2 retardation film.

3. The polarizing plate according to claim 1, wherein the absolute orthogonal b-coordinate value ranges from approximately 1.9 to approximately 2.6.

4. The polarizing plate according to claim 1, wherein the polarizing plate has a moisture content ranging from approximately 2.0 wt % to approximately 3 wt %, and the polarizer has a boric acid content ranging from approximately 20.5 wt % to approximately 22.5 wt %.

5. The polarizing plate according to claim 4, wherein the polarizer has a thickness ranging from approximately 5 micrometers to approximately 25 micrometers.

6. The polarizing plate according to claim 1, wherein the protective film comprises a resin comprising cellulose, polyester, cyclic polyolefin, polycarbonate, polyether sulfone, polysulfone, polyamide, polyimide, polyolefin, polyarylate, polyvinyl alcohol, polyvinyl chloride, and/or polyvinylidene chloride.

7. The polarizing plate according to claim 1, wherein at a wavelength of 550 nanometers, the half-wavelength (λ

/2) retardation film has an in-plane retardation value ranging from approximately 200 nanometers to approximately 300 nanometers, and the quarter-wavelength (λ

/4) retardation film has an in-plane retardation value ranging from approximately 100 nanometers to approximately 200 nanometers.

8. The polarizing plate according to claim 1, wherein at a wavelength of 550 nanometers, the half-wavelength (λ

/2) retardation film has an out-of-plane retardation value ranging from approximately 220 nanometers to approximately 240 nanometers, and the quarter-wavelength (λ

/4) retardation film has an out-of-plane retardation value ranging from approximately −

100 nanometers to approximately −

130 nanometers, and

wherein the out-of-plane retardation value (Rth) is calculated using the formula Rth=((nx+ny)/2−

nz)×

d, wherein nx, ny, and nz are refractive indexes in x-, y-, and z-axis directions of each retardation film, and d is a thickness of the retardation film.

9. The polarizing plate according to claim 1, wherein the half-wavelength (λ

/2) retardation film comprises a cycloolefin film, and the quarter-wavelength (λ

/4) retardation film comprises an acrylic film.

10. The polarizing plate according to claim 1, wherein the half-wavelength (λ

/2) retardation film and the quarter-wavelength (λ

/4) retardation film comprise birefringences of opposite signs.

11. The polarizing plate according to claim 1, further comprising a protective film between the polarizer and the half-wavelength (λ

/2) retardation film, or between the half-wavelength (λ

/2) retardation film and the quarter-wavelength (λ

/4) retardation film.

12. A method for preparing a polarizing plate, comprising:

preparing a polarizer comprising approximately 25 wt % to approximately 26 wt % moisture and approximately 20.5 wt % to approximately 22.5 wt % boric acid; and

forming a protective film and/or a retardation film on at least one surface of the polarizer.

13. The method according to claim 12, wherein preparing the polarizer comprises:

stretching a polyvinyl alcohol film in an aqueous boric acid solution comprising approximately 3.0 wt % to approximately 3.5 wt % boric acid, and

drying the stretched polyvinyl alcohol film at a drying temperature of approximately 50°

C. to approximately 70°

C., and at an air volume having an air supply rate of approximately 1400 RPM to approximately 1500 RPM, and an air exhaust rate of approximately 2000 RPM to approximately 3000 RPM.

14. The method according to claim 12, wherein forming the protective film and/or the retardation film comprises:

placing a protective film on an upper surface of the polarizer, and

placing a half-wavelength (λ

/2) retardation film on a lower surface of the polarizer, and a quarter-wavelength (λ

/4) retardation film on a lower surface of the half-wavelength (λ

/2) retardation film.

15. An optical display apparatus comprising:

a panel; and

a polarizing plate stacked on an upper surface of the panel;

wherein the polarizing plate comprises a polarizer having an absorption axis, a half-wavelength (λ

/2) retardation film on a lower surface of the polarizer, and a quarter-wavelength (λ

/4) retardation film on a lower surface of the half-wavelength (λ

/2) retardation film, and

wherein an absolute orthogonal b-coordinate value based on a CIELAB color coordinate system is approximately 3 or less when the polarizing plate is stacked with a reference polarizing plate having a degree of polarization of at least 99.9% such that an angle between the absorption axis of the polarizer and an absorption axis of a polarizer of the reference polarizing plate is 90°

.

16. The optical display apparatus according to claim 15, wherein the polarizer further comprises a transmission axis, and the absolute orthogonal b-coordinate value based on the CIELAB color coordinate system is approximately 3 or less when the polarizing plate is stacked with the reference polarizing plate having a degree of polarization of at least 99.9% such that an angle between the transmission axis of the polarizer and a transmission axis of the polarizer of the reference polarizing plate is 90°

.

17. The optical display apparatus according to claim 15, wherein the apparatus is an organic light emitting diode (OLED) display apparatus.

18. The optical display apparatus according to claim 15, wherein the polarizing plate further comprises:

a protective film on an upper surface of the polarizer; and

an adhesive layer on a lower surface of the half-wavelength (λ

/2) retardation film.

19. The optical display apparatus according to claim 18, wherein the polarizing plate further comprises a second adhesive layer on a lower surface of the a quarter-wavelength (λ

/4) retardation film.

20. The optical display apparatus according to claim 15, wherein:

the polarizing plate has a moisture content ranging from approximately 2.0 wt % to approximately 2.8 wt %;

the polarizer has a boric acid content ranging from approximately 20.5 wt % to approximately 22.5 wt %;

the half-wavelength (λ

/2) retardation film has an in-plane retardation value ranging from approximately 200 nanometers to approximately 300 nanometers, and the quarter-wavelength (λ

/4) retardation film has an in-plane retardation value ranging from approximately 100 nanometers to approximately 200 nanometers at a wavelength of 550 nanometers; and

the half-wavelength (λ

/2) retardation film has an out-of-plane retardation value ranging from approximately 220 nanometers to approximately 240 nanometers, and the quarter-wavelength (λ

/4) retardation film has an out-of-plane retardation value ranging from approximately −

100 nanometers to approximately −

130 nanometers at a wavelength of 550 nanometers, wherein the out-of-plane retardation value (Rth) is calculated using the formula Rth=((nx+ny)/2−

nz)×

d, wherein nx, ny, and nz are refractive indexes in x-, y-, and z-axis directions of each retardation film, and d is a thickness of the retardation film.