U.S. patent application number 14/458473 was filed with the patent office on 2014-11-27 for optical unit and organic light emitting diode display having the same.
The applicant listed for this patent is SAMSUNG DISPLAY CO., LTD.. Invention is credited to Woo-Suk JUNG, Soon-Ryong PARK.
Application Number | 20140346494 14/458473 |
Document ID | / |
Family ID | 45972440 |
Filed Date | 2014-11-27 |
United States Patent
Application |
20140346494 |
Kind Code |
A1 |
JUNG; Woo-Suk ; et
al. |
November 27, 2014 |
OPTICAL UNIT AND ORGANIC LIGHT EMITTING DIODE DISPLAY HAVING THE
SAME
Abstract
An optical unit on a light emitting unit includes a first
polarizing plate on the light emitting unit, a second polarizing
plate on the first polarizing plate, the second polarizing plate
having a higher polarization degree than the first polarizing
plate, and a plurality of phase shift plates between the first
polarizing plate and the second polarizing plate.
Inventors: |
JUNG; Woo-Suk; (Yongin-City,
KR) ; PARK; Soon-Ryong; (Yongin-City, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAMSUNG DISPLAY CO., LTD. |
Yongin-City |
|
KR |
|
|
Family ID: |
45972440 |
Appl. No.: |
14/458473 |
Filed: |
August 13, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13137978 |
Sep 22, 2011 |
8810114 |
|
|
14458473 |
|
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Current U.S.
Class: |
257/40 |
Current CPC
Class: |
H01L 2251/5307 20130101;
H01L 2251/5315 20130101; G02F 2201/16 20130101; G02F 2001/133638
20130101; H01L 51/5293 20130101; G02F 1/133528 20130101; H01L
27/3244 20130101; G02F 1/133502 20130101; H01L 51/5281
20130101 |
Class at
Publication: |
257/40 |
International
Class: |
H01L 51/52 20060101
H01L051/52 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 25, 2010 |
KR |
10-2010-0104039 |
Claims
1. An optical unit on a light emitting unit, comprising: a first
polarizing plate on the light emitting unit; a second polarizing
plate on the first polarizing plate, the second polarizing plate
having a higher polarization degree than the first polarizing
plate; and a plurality of phase shift plates between the first
polarizing plate and the second polarizing plate, wherein an
intersection angle between a polarization axis of the first
polarizing plate and a polarization axis of the second polarizing
plate is about 45 degrees, the plurality of phase shift plates
comprising: a fourth phase shift plate between the first polarizing
plate and the second polarizing plate, wherein the fourth phase
shift plate is a 1/2 wavelength plate; and a fifth phase shift
plate between the first polarizing plate and the fourth phase shift
plate, wherein the fifth phase shift plate is a 1/4 wavelength
plate.
2-11. (canceled)
12. The optical unit as claimed in claim 1, wherein: an
intersection angle between a polarization axis of the second
polarizing plate and an optical axis of the fourth phase shift
plate is in a range of about 10 degrees to about 20 degrees, and an
intersection angle between a polarization axis of the first
polarizing plate and an optical axis of the fourth phase shift
plate is in a range of about 25 degrees to about 35 degrees.
13. The optical unit as claimed in claim 12, wherein: an
intersection angle between a polarization axis of the second
polarizing plate and an optical axis of the fifth phase shift plate
is in a range of about 70 degrees to about 80 degrees, and an
intersection angle between a polarization axis of the first
polarizing plate and an optical axis of the fifth phase shift plate
is in a range of about 25 degrees to about 35 degrees.
14-16. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This is a divisional application based on pending
application Ser. No. 13/137,978, filed Sep. 22, 2011, the entire
contents of which is hereby incorporated by reference.
BACKGROUND
[0002] 1. Field
[0003] Embodiments relate to an optical unit. More particularly,
embodiments relate to an optical unit for improving light
characteristics, and an organic light emitting diode (OLED) display
having the same.
[0004] 2. Description of the Related Art
[0005] A display device displays an image. An organic light
emitting diode (OLED) display has a self light emitting
characteristic. Unlike a liquid crystal display (LCD), an OLED
display does not require a light source. Accordingly, the thickness
and weight can be reduced. The organic light emitting diode (OLED)
display has high fidelity characteristics, such as low power
consumption, high luminance, and fast reaction speed.
[0006] The disclosed information in the Background is only for
enhancing an understanding of the background of the described
technology. Therefore, it may contain information that does not
form the prior art already known to a person of ordinary skill in
the art in this country.
SUMMARY
[0007] Present embodiments may be directed to an optical unit and
an organic light emitting diode (OLED) display.
[0008] An exemplary embodiment provides an optical unit on a light
emitting unit, including a first polarizing plate on the light
emitting unit, a second polarizing plate on the first polarizing
plate, the second polarizing plate having a higher polarization
degree than the first polarizing plate, and a plurality of phase
shift plates between the first polarizing plate and the second
polarizing plate.
[0009] The first polarizing plate may have a higher transmittance
than that of the second polarizing plate.
[0010] The first polarizing plate may include a matrix, an iodine,
and a dye.
[0011] A weight ratio of the iodine and the dye may be in a range
of about 1:1 to about 1:2.
[0012] An intersection angle between a polarization axis of the
first polarizing plate and a polarization axis of the second
polarizing plate may be about 45 degrees.
[0013] The plurality of phase shift plates may include: a first
phase shift plate between the first polarizing plate and the second
polarizing plate, wherein the first phase shift plate is a 1/2
wavelength plate; a second phase shift plate between the first
polarizing plate and the first phase shift plate, wherein the
second phase shift plate is a 1/4 wavelength plate; and a third
phase shift plate between the first polarizing plate and the second
phase shift plate, wherein the third phase shift plate is a 1/4
wavelength plate.
[0014] An intersection angle between a polarization axis of the
second polarizing plate and an optical axis of the first phase
shift plate may be in a range of about 17.5 degrees to about 27.5
degrees, and an intersection angle between a polarization axis of
the first polarizing plate and an optical axis of the first phase
shift plate may be in a range of about 17.5 degrees and to about
27.5 degrees.
[0015] An intersection angle between a polarization axis of the
second polarizing plate and an optical axis of the second phase
shift plate may be in a range of about 40 degrees to about 50
degrees, and an intersection angle between a polarization axis of
the first polarizing plate and an optical axis of the second phase
shift plate may be in a range of about 0 degrees to about 5
degrees.
[0016] An intersection angle between a polarization axis of the
second polarizing plate and an optical axis of the third phase
shift plate may be in a range of about 85 degrees to about 90
degrees, and an intersection angle between a polarization axis of
the first polarizing plate and an optical axis of the third phase
shift plate may be in a range of about 40 degrees to about 50
degrees.
[0017] An intersection angle between an optical axis of the second
phase shift plate and an optical axis of the third phase shift
plate may be about 45 degrees.
[0018] The plurality of phase shift plates may include: a fourth
phase shift plate between the first polarizing plate and the second
polarizing plate, wherein the fourth phase shift plate is a 1/2
wavelength plate; and a fifth phase shift plate between the first
polarizing plate and the fifth phase shift plate, wherein the fifth
phase shift plate is a 1/4 wavelength plate.
[0019] An intersection angle between a polarization axis of the
second polarizing plate and an optical axis of the fourth phase
shift plate may be in a range of about 10 degrees to about 20
degrees, and an intersection angle between a polarization axis of
the first polarizing plate and an optical axis of the fourth phase
shift plate may be in a range of about 25 degrees to about 35
degrees.
[0020] An intersection angle between a polarization axis of the
second polarizing plate and an optical axis of the fifth phase
shift plate may be in a range of about 70 degrees to about 80
degrees, and an intersection angle between a polarization axis of
the first polarizing plate and an optical axis of the fifth phase
shift plate may be in a range of about 25 degrees to about 35
degrees.
[0021] The optical unit may further include a sixth phase shift
plate between the light emitting unit and the first polarizing
plate.
[0022] An intersection angle between an optical axis of the sixth
phase shift plate and a polarization axis of the first polarizing
plate may be in a range of about 40 degrees to about 50
degrees.
[0023] Another exemplary embodiment provides an organic light
emitting diode (OLED) display including an organic light emitting
element for emitting light, wherein the organic light emitting
element includes a first electrode, a second electrode on the first
electrode, and an organic emission layer between the first
electrode and the second electrode, and the above described light
emitting unit on the light emitting element.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a cross-sectional view illustrating an organic
light emitting diode (OLED) display according to a first exemplary
embodiment.
[0025] FIG. 2 is a layout view illustrating a driving circuit and
an organic light emitting element of an organic light emitting
diode display according to the first exemplary embodiment.
[0026] FIG. 3 is a cross-sectional view illustrating a path of
light inflowing from the outside to an organic light emitting diode
(OLED) display according to the first exemplary embodiment.
[0027] FIG. 4 is a schematic diagram illustrating a path of light
inflowing from the outside to an organic light emitting diode
(OLED) display according to the first exemplary embodiment.
[0028] FIG. 5 is a diagram illustrating the loss of light inflowing
from the outside to the organic light emitting diode (OLED) display
according to the first exemplary embodiment.
[0029] FIG. 6 is a cross-sectional view illustrating a path of
light emitted from an organic light emitting element of the organic
light emitting diode (OLED) display to the outside according to the
first exemplary embodiment.
[0030] FIG. 7 is a schematic diagram illustrating a path of light
emitted from an organic light emitting element of the organic light
emitting diode (OLED) display to the outside according to the first
exemplary embodiment.
[0031] FIG. 8 is a diagram illustrating the loss of light emitted
from an organic light emitting element of the organic light
emitting diode (OLED) display to the outside according to the first
exemplary embodiment.
[0032] FIG. 9 is a cross-sectional view illustrating an organic
light emitting diode (OLED) display according to the second
exemplary embodiment.
[0033] FIG. 10 is a cross-sectional view illustrating a path of
light inflowing from the outside to the inside of the organic light
emitting diode (OLED) display according to the second exemplary
embodiment.
[0034] FIG. 11 is a schematic diagram illustrating a path of light
inflowing from the outside to the inside of the organic light
emitting diode (OLED) display according to the second exemplary
embodiment.
[0035] FIG. 12 is a cross-sectional view illustrating a path of
light emitted from the organic light emitting element of the
organic light emitting diode (OLED) according to the second
exemplary embodiment.
[0036] FIG. 13 is a schematic diagram illustrating a path of light
emitted from the organic light emitting element of the organic
light emitting diode (OLED) according to the second exemplary
embodiment.
DETAILED DESCRIPTION
[0037] Korean Patent Application No. 10-2010-0104039, filed on Oct.
25, 2010, in the Korean Intellectual Property Office, and entitled:
"Optical Unit and Organic Light Emitting Diode Display having the
Same," is incorporated by reference herein in its entirety.
[0038] The inventive concept will now be described more fully
hereinafter with reference to the accompanying drawings, in which
exemplary embodiments of the inventive concept are illustrated. The
inventive concept may, however, be embodied in different forms and
should not be construed as limited to the embodiments set forth
herein. Rather, these embodiments are provided so that this
disclosure will be thorough and complete, and will fully convey the
scope of the inventive concept to those skilled in the art.
[0039] Accordingly, the drawings and description are to be regarded
as illustrative in nature and not restrictive. Throughout the
specification, like reference numerals denote like elements. The
first exemplary embodiment will be representatively described using
like reference numerals for like constituent elements having the
same structure in various exemplary embodiments. Other exemplary
embodiments will be described based on differences from the first
exemplary embodiment.
[0040] In drawings, the size and thickness of each element are
approximately shown for better understanding and easy of
description. Therefore, the inventive concept is not limited to the
drawings. In the drawings, the thickness of layers, films, panels,
regions, etc., are exaggerated for clarity. In the drawings, the
thicknesses of layers or regions are exaggerated for better
understanding and ease of description. It will be understood that
when an element such as a layer, film, region, or substrate is
referred to as being "on" another element, it can be directly on
the other element or intervening elements may also be present.
[0041] In addition, unless explicitly described to the contrary,
the word "comprise" and variations such as "comprises" or
"comprising" will be understood to imply the inclusion of stated
elements but not the exclusion of any other elements. In the
specification, it will be understood that when an element is
referred to as being on another element, it can be above another
element or below another element. It does not mean that the element
must be above another element in a gravity direction.
[0042] Hereinafter, an organic light emitting diode (OLED) display
according to a first exemplary embodiment will be described with
reference to FIG. 1 to FIG. 8.
[0043] FIG. 1 is a cross-sectional view illustrating an organic
light emitting diode (OLED) display according to a first exemplary
embodiment.
[0044] As shown in FIG. 1, the OLED display 100, according to the
first exemplary embodiment, includes a first substrate 51, a second
substrate 52 adhered to the first substrate 51, and an optical unit
58.
[0045] The first substrate 51 includes a substrate member 511, a
driving circuit (DC) formed on the substrate member 511, and an
organic light emitting element L1. The organic light emitting
element L1 is formed on the driving circuit (DC) as a light
emitting unit.
[0046] FIG. 2 is a layout view illustrating a driving circuit and
an organic light emitting element of an organic light emitting
diode display according to the first exemplary embodiment.
[0047] As shown in FIG. 2, the driving circuit (DC) generally has a
structure of FIG. 2. As shown in FIG. 2, the driving circuit (DC)
includes at least two thin film transistors T1 and T2 and at least
one capacitor C1. The thin film transistor includes a switching
transistor T1 and a driving transistor T2.
[0048] The OLED display, according to the first exemplary
embodiment, has a 2Tr-1Cap structure. However, an OLED display
according to another exemplary embodiment, may have various
structures, including at least three film transistors, at least two
capacitors, and additional wires. Additional thin film transistors
and capacitors may be elements of a compensating circuit.
[0049] A switching transistor T1 is connected to a scan line SL1
and a data line DL1. The scan line SL1 transmits a data voltage
input from the data line DL1 to the driving transistor T2 according
to a switching voltage input to the scan line SL1. A capacitor C1
is connected to the switching transistor T1 and a power supply line
VDD. The capacitor C1 stores a voltage difference between a voltage
transmitted from the switching transistor T1 and a voltage supplied
from the power supply line VDD.
[0050] The driving transistor T2 is connected to the power supply
line VDD and the capacitor C1. The driving transistor T2 supplies
an output current (I.sub.OLED) to the organic light emitting
element L1 in proportion to a square of a voltage difference of a
voltage stored in the capacitor C1 and a threshold voltage. The
organic light emitting element L1 emits light by the output current
(I.sub.OLED).
[0051] Referring to FIG. 1, the driving transistor T2 includes a
source electrode 533, a drain electrode 532, and a gate electrode
531.
[0052] The organic light emitting element L1 displays an image by
emitting light. The organic light emitting element L1 includes a
first electrode 544, an organic emission layer 545 formed on the
first electrode 544, and a second electrode 546 formed on the
organic emission layer 545. The second electrode 546 is disposed on
the first electrode 544. The organic emission layer 545 is disposed
between the first electrode 544 and the second electrode 546. The
first electrode 544 is an anode and the second electrode 546 is a
cathode. However, the first exemplary embodiment is not limited
thereto. According to a driving method, the first electrode 544 may
be a cathode, and the second electrode 546 may be an anode. The
first electrode 544 of the organic light emitting element L1 is
connected to a drain electrode 532 of the driving transistor T2. At
least one of the first electrode 544 and the second electrode 546
is formed to be translucent or reflective to reflect light.
[0053] The organic light emitting diode (OLED) display 100,
according to the first exemplary embodiment, displays images by
emitting light at the organic light emitting element L1 in a
direction from the organic emission layer 545 to the second
electrode 546. The organic light emitting diode (OLED) display 100
is a top emission type.
[0054] The optical unit 58 improves visibility of the organic light
emitting diode (OLED) display 100 by suppressing the reflection of
external light caused by the organic light emitting element L1. The
optical unit 58 minimizes the loss of light emitted from the
organic light emitting element L1. The optical unit 58 includes a
first polarizing plate 585, a second polarizing plate 581, and a
plurality of phase shift plates 582, 583, and 584.
[0055] The first polarizing plate 585 is disposed on the organic
emitting element L1. The organic emitting element L1 is a light
emitting unit for emitting light. The second polarizing plate 581
is disposed on the first polarizing plate 585. The plurality of
phase shift plates 582, 583, and 584 are disposed between the first
polarizing plate 585 and the second polarizing plate 581. The
plurality of phase shift plates include a first phase shift plate
582 disposed between the first polarizing plate 585 and the second
polarizing plate 581, a second phase shift plate 583 disposed
between the first polarizing plate 585 and the first phase shift
plate 582, and a third phase shift plate 584 disposed between the
first polarizing plate 585 and the second phase shift plate 583.
The third phase shift plate 584, the second phase shift plate 583,
and the first phase shift plate 582 are sequentially stacked on the
first polarizing plate 585.
[0056] The optical unit 58 further includes a phase shift plate 586
disposed between the first polarizing plate 585 and the organic
light emitting element L1. Hereinafter, such additional phase shift
plate is referred to as an additional phase shift plate 586.
However, the first exemplary embodiment is not limited thereto.
Accordingly, the additional phase shift plate 586 may be
omitted.
[0057] The first polarizing plate 585 and the second polarizing
plate 581 have different polarization axes, and linearly polarize
light in a direction to the corresponding polarization axes. The
first polarizing plate 585 and the second polarizing plate 581 pass
light coinciding with a corresponding polarization axis and absorb
light not coinciding with the corresponding polarization axis.
After the light passes through the first polarizing plate 585 and
the second polarizing plate 581, the light is linearly polarized to
each polarization axis direction.
[0058] The second polarizing plate 581 has a higher polarization
degree than that of the first polarizing plate 585, and has lower
transmittance than that of the first polarization plate 585. The
first polarizing plate 585 has higher transmittance than that of
the second polarizing plate 581. The first polarizing plate 585 has
a lower polarization degree than that of the second polarizing
plate 581. Accordingly, when light passes through the first
polarizing plate 585, the loss of light is less and the
polarization degree is lower that light passed through the second
polarizing plate 581.
[0059] The first polarizing plate 585 has a matrix structure. The
first polarizing plate 585 has a matrix, and includes iodine and a
dye. The matrix may have a structure of polyvinyl alcohol
(PVA).
[0060] The first polarizing plate 585 includes iodine, a dye, and
polyvinyl alcohol. The transmittance of the first polarizing plate
585 may be improved. The polarization degree of the first
polarization plate 585 may be reduced at the same time by reducing
the concentration of at least one of the iodine, dye, and polyvinyl
alcohol.
[0061] When a polarizing plate is formed by including only iodine
with polyvinyl alcohol, an iodine ion chain is oriented by being
stretched and oriented with polyvinyl alcohol chain. Therefore, the
polarizing plate has a polarization property. When the polyvinyl
alcohol includes only iodine, the polarization efficiency and
transmittance of the polarizing plate are improved. However, due to
the sublimation property of the iodine, durability against
temperature, humidity, and light is deteriorated. In other words,
the uniformity of the polarizing plate may be deteriorated. When
the polarizing plate is formed by including only the dye with the
polyvinyl alcohol, similar to a polarizing plate formed with only
iodine and polyvinyl alcohol, the dye is stretched and oriented
with the polyvinyl alcohol chain, thereby polarizing at the
polarizing plate. Since the dye does not have a sublimation
property, the polarizing plate formed of dye and polyvinyl alcohol
may have superior durability. However, the diachronic property may
be deteriorated.
[0062] The first polarizing plate 585 formed of iodine, having
superior uniformity, and dye, having superior durability with
polyvinyl alcohol has improved uniformity. Uniformity is improved
because the dye compensates insufficient uniformity of the
iodine.
[0063] The first polarizing plate 585 has an absorption axis and a
polarization axis. The absorption axis is a stretched and oriented
axis of an iodine ion chain and a dye ion chain. The absorption
axis absorbs one of two vertical components of light vibrated in a
random direction, while electrons of the first polarizing plate 585
interact with one of the two vertical components, so that the
electrical energy of light is changed to electronic energy. The
polarization axis is an axis perpendicular to the absorption axis.
The polarization axis passes the vibrating light in a direction to
the polarization axis.
[0064] The first polarizing plate 585 may be formed by a method of
stretching a polyvinyl alcohol film and cohering iodine and dye
therewith, a method of absorbing iodine and dye in a polyvinyl
alcohol film and stretching the polyvinyl alcohol film, and a
method of dying iodine and dye at a polyvinyl alcohol film and
stretching the polyvinyl alcohol film at the same time.
[0065] The weight ratio of iodine and dye of the first polarizing
plate 585 may be about 1:1 to about 1:2. When the weight ratio of
iodine and dye satisfies the above range, the uniformity and the
polarization degree of the first polarizing plate 585 become
superior, without deterioration. As a general range, the thickness
of the first polarizing plate 585 may be about 15 .mu.m to about 30
.mu.m.
[0066] An intersection angle of the polarization axis of the first
polarizing plate 585 and the polarization axis of the second
polarizing plate 581 is about 45 degrees.
[0067] The first phase shift plate 582 is a 1/2 wavelength plate.
The first phase shift plate 582 has an optical axis tilted at a
predetermined angle in a range of about 17.5 degrees to about 27.5
degrees, compared to the polarization axis of the second polarizing
plate 581. In other words, an intersection angle of the optical
axis of the first phase shift plate 582 and the polarization axis
of the second polarizing plate 581 is in a range of about 17.5
degrees to about 27.5 degrees. An intersection angle of an optical
axis of the first phase shift plate 582 and a polarization axis of
the first polarizing plate 585 is in a range of about 17.5 degrees
to about 27.5 degrees.
[0068] The second phase shift plate 583 is a 1/4 wavelength plate.
The second phase shift plate 583 has an optical axis tilted at a
predetermined angle in a range of about 40 degrees to about 50
degrees from the polarization axis of the second polarizing plate
581.
[0069] An intersection angle of an optical axis of the second phase
shift plate 583 and the polarization axis of the second polarizing
plate 581 is in a range of about 40 degrees to about 50 degrees. An
intersection angle of an optical axis of the second phase shift
plate 583 and the polarization axis of the first polarizing plate
585 is in a range of about 0 degrees to about 5 degrees.
[0070] The third phase shift plate 584 is a 1/4 wavelength plate.
The third phase shift plate 584 has an optical axis tilted at a
predetermined angle in a range of about 85 degrees to about 95
degrees from the polarization axis of the second polarizing plate
581. The intersection angle of an optical axis of the third phase
shift plate 584 and the polarization axis of the second polarizing
plate 581 is in a range of about 85 degrees to about 95 degrees.
The intersection angle of an optical axis of the third phase shift
plate 584 and the polarization axis of the first polarizing plate
585 is in a range of about 40 degrees to about 50 degrees.
[0071] The additional phase shift plate 586 is a 1/4 wavelength
plate. The additional phase shift plate 586 has an optical axis
tilted at a predetermined angle in a range about 40 degrees to
about 50 degrees from the polarization axis of the first polarizing
plate 585.
[0072] Where the organic light emitting element L1 and the driving
circuit (DC) are formed, the second substrate 52 covers the first
substrate 51. The second substrate 52 is arranged opposite to the
first substrate 51 and covers the first substrate 51 to seal the
thin film transistors T1 and T2, the capacitor C1, and the organic
light emitting element L1 from the outside. Although not shown, the
second substrate 52 is cohered to the first substrate 51 through a
sealer formed along an edge. Thus, a space is sealed between the
first and second substrates 51 and 52.
[0073] Although the optical unit 58 formed on the organic light
emitting element L1 is attached on the second substrate 52, the
present embodiments are not limited thereto. Accordingly, the
optical unit 58 is disposed between the second substrate 52 and the
organic light emitting element L1. The optical unit 58 may be
covered by the second substrate 52. The optical unit 58 may be
disposed inside a sealed space, between the first substrate 51 and
the second substrate 52. The optical unit 58 may be disposed at any
location along a light emitting path of the organic light emitting
element L1. The organic light emitting element L1 is a light
emitting unit.
[0074] The organic light emitting diode (OLED) display 100
minimizes the loss of light emitted from the organic emission layer
545 to the outside while effectively suppressing external
reflection and improving visibility. The display characteristic of
the organic light emitting diode (OLED) display 100 is
improved.
[0075] The organic light emitting diode (OLED) display 100 has low
power consumption and improved life-span because light generated
from the organic emission layer 545 is efficiently emitted to the
outside.
[0076] A fundamental concept of the optical unit 58 of the organic
light emitting diode (OLED) display, according to the first
exemplary embodiment, is that the optical unit 58 effectively
suppresses external reflection and minimizes the loss of light
emitted from the organic emission layer 545 to the outside. The
fundamental concept of the optical unit 58 will be described with
reference to FIG. 3 to FIG. 9.
[0077] Light passing through the optical unit 58 will be described
based on visible light. Visible light has a color classified by a
wavelength band. Blue light has a wavelength within a predetermined
range of about 420 nm to about 480 nm. Green light has a wavelength
of about 550 nm. Red light has a wavelength of about 650 nm.
[0078] Visible light passing through the optical unit 58 each have
different wavelengths. Thus, there is a slight variation of each
visible light color. Accordingly, in the optical unit 58, the
plurality of phase shift plates 582, 583, and 584 are adjusted to
have a proper angle within the described wavelength range. The
proper angle is adjusted in relation to a color light, suppressing
external light reflection, and the state of light emitted from the
organic light emitting element L1.
[0079] An operation of the optical unit 58 will be described based
on an optical unit 58 arranged to minimize the loss of blue light
and externally emit the blue light from the organic light emitting
element L1. Such an arrangement of the optical unit 58 is proper
when luminance of blue light is lower than other light emitted from
the organic light emitting element L1.
[0080] However, other visible light is not that different from blue
light when other visible light passes through the optical unit 58.
In other words, other visible light has similar behavior to blue
light when other visible light passes through the optical unit 58.
Other visible light has a slightly different behavior, because
other visible light has different wavelengths than blue light.
Other visible light has slightly lower transmittance than blue
light when other visible light passes through the optical unit 58.
All visible light, including blue light, has similar behavior in
present embodiments.
[0081] A path of light flowing into the optical unit 58 from the
outside will be described with reference to FIG. 3 to FIG. 5.
[0082] FIG. 3 and FIG. 4 are a cross-sectional view and a schematic
diagram illustrating a path of light flowing from the outside into
an organic light emitting diode (OLED) display according to the
first exemplary embodiment. FIG. 5 is a diagram illustrating the
loss of light flowing from the outside into the organic light
emitting diode (OLED) display according to the first exemplary
embodiment.
[0083] While external light passes through the second polarization
plate 581, as shown in FIG. 3 to FIG. 5, external light, having
various phases, is linearly polarized in a direction to a
polarization axis of the second polarizing plate 581. While the
linearly polarized light passes through the first phase shift plate
582, which is a 1/2 wavelength plate, the linearly polarized light
rotates 45 degrees with the linear polarization state sustained.
The optical axis of the first phase shift plate 582 is tilted at
about 22.5 degrees from the polarization axis of the second
polarizing plate 581. The intersection angle of the optical axis of
the first phase shift plate 582 and the polarization axis of the
second polarizing plate 581 is about 22.5 degrees.
[0084] The 45 degree rotated and linearly-polarized light passes
through the second phase shift plate 583, without any substantial
variation. The second phase shift plate 583 is a 1/4 wavelength
plate. The optical axis of the second phase shift plate 583 is
tilted at about 45 degrees from the polarization axis of the second
polarizing plate 581. The intersection angle of the optical axis of
the second phase shift plate 583 and the polarization axis of the
second polarizing plate 581 is about 45 degrees.
[0085] Since the axis direction of the 45 degree rotated and
linearly polarized light from the first phase shift plate 582 is
substantially equivalent to an optical axis direction of the second
phase shift plate 583, light passes the second phase shift plate
583 without any substantial variation. Since the visible light has
various wavelengths distributed by each color, the term
"substantially identical" means that axis directions of all light
passing through the first phase shift plate 582 are not perfectly
identical.
[0086] The 45 degree rotated and linearly-polarized light, passing
through the second phase shift plate 583, is changed to circular
polarized light after passing through the third phase shift plate
584. The third shift plate 584 is a 1/4 wavelength plate. An
optical axis of the third phase shift plate 584 is tilted at about
90 degrees from the polarization axis of the second polarizing
plate 581. An intersection angle between an optical axis of the
third phase shift plate 584 and a polarization axis of the second
polarizing plate 581 is about 90 degrees.
[0087] Since the intersection angle between the axis direction of
the 45 degree rotated linearly polarized light and an optical axis
direction of the third phase shift plate 584 is about 45 degrees,
the linearly-polarized light is changed to circular polarized light
while passing through the third phase shift plate 584.
[0088] While passing through the first polarizing plate 585, the
circular polarized light from the third phase shift plate 584 is
linearly polarized in a polarization axis direction of the first
polarizing plate 585. Light not linearly polarized is absorbed.
Among the circular polarized light, some light having components
matching the polarization axis of the first polarizing plate 585
passes through the first polarizing plate 585. The remaining light
is absorbed at the first polarization plate 585 and eliminated. The
remaining light is eliminated because the light is not matched with
the polarization axis. A smaller amount of the external light is
absorbed at the first polarization plate 585 and eliminated than
the external light passing through the second polarizing plate 581.
This occurs because the first polarizing plate 585 has a higher
transmittance and a lower polarization degree that that of the
second polarizing plate 581. In other words, the loss of light
becomes smaller when the light passes through the first polarizing
plate 585.
[0089] Since a predetermined part of the circular polarized light
is eliminated when the circular polarized light passes through the
first polarizing plate 585, the organic light emitting diode (OLED)
display 100 can suppress external light reflection.
[0090] While passing through the additional phase shift plate 586,
the linearly polarized light from the first polarizing plate 585 is
circularly polarized. The circular polarized light is reflected at
electrodes 544 and 546 of the organic light emitting element L1.
The axis direction of the circular polarized light is changed by
about 180 degrees. The light may be reflected not only by the
electrodes 544 and 546 of the organic light emitting element L1,
but also reflected by other metal wires.
[0091] While passing through the additional phase shift plate 586,
absorbed at the first polarizing plate 585, and eliminated, the
circular polarized light with the axis direction changed at 180
degrees is again linearly polarized.
[0092] The light remaining after passing through the first
polarizing plate 585 passes through the additional phase shift
plate 586 and is reflected by the organic light emitting element
L1. The reflected light passes through the additional phase shift
plate 586 again and is eliminated by the first polarization plate
585. Therefore, the organic light emitting diode (OLED) display 100
suppresses the external light reflection.
[0093] The light flowing from the outside into the inside, through
the optical unit 58, is almost eliminated at the first polarizing
plate 585. Accordingly, the organic light emitting diode (OLED)
display 100 effectively suppresses the external light reflection
and improves the visibility.
[0094] A path of light emitted to the outside from an organic
emission layer (545 in FIG. 1) will be described with reference to
FIG. 6 to FIG. 8.
[0095] FIG. 6 and FIG. 7 are a cross-sectional view and a schematic
diagram illustrating a path of light emitted from an organic light
emitting element of the organic light emitting diode (OLED) display
to the outside according to the first exemplary embodiment. FIG. 8
is a diagram illustrating the loss of light emitted from an organic
light emitting element of the organic light emitting diode (OLED)
display to the outside according to the first exemplary
embodiment.
[0096] The light emitted from the organic emission layer 545
sequentially passes through the second electrode 546 and the
additional phase shift plate 586. The light has various phases.
[0097] After passing through the additional phase shift plate 586,
the light propagates to the first polarizing plate 585. While
passing through the first polarizing plate 585, light matching a
polarization axis of the first polarizing plate 585, among the
light passing through the additional phase shift plate 586, is
linearly polarized. A smaller amount of the internal light is
absorbed at the first polarizing plate 585 and eliminated than the
internal light passing through the second polarizing plate 585. A
smaller amount of the internal light is absorbed because the first
polarizing plate 585 has a higher transmittance and a lower
polarization degree than the second polarizing plate 581. The loss
of light becomes smaller when the light passes through the first
polarizing plate 585.
[0098] While passing through the third phase shift plate 584 which
is a 1/4 wavelength plate, the linearly-polarized light, after
passing through the first polarizing plate 585, is circular
polarized. The optical axis of the third phase shift plate 584 is
tilted at about 45 degrees from a polarization axis of the first
polarizing plate 585. The intersection angle between the optical
axis of the third phase shift plate 584 and the polarization axis
of the first polarizing plate 585 is about 45 degrees.
[0099] Since the intersection angle between the axis direction of
the linearly polarized light, passed through the first polarizing
plate 585, and an optical axis direction of the third phase shift
plate 584 is about 40 degrees, the linearly polarized light becomes
circular polarized while passing through the third phase shift
plate 584.
[0100] While passing through the second phase shift plate 583,
which is a 1/4 wavelength plate, the circular polarized light,
after passing through the third delay plate 584, is linearly
polarized. An optical axis of the second phase shift plate 583 is
identical to a polarization axis of the first polarizing plate 585.
The circular polarized light, after passing through the third phase
shift plate 584, is linearly polarized while passing through the
second phase shift plate 583. The linearly polarized light, after
passing through the second phase shift plate 584, becomes identical
to the linearly polarized light, before passing through the third
phase shift plate 584. The light that is linearly polarized by
passing through the first polarizing plate 585 is similar to the
light that is linearly polarized by passing through the second
phase shift plate 583.
[0101] The linearly polarized light, after passing through the
second phase shift plate 583, rotates about 45 degrees with the
linear polarization state. The linear polarization state is
sustained while passing through the first phase shift plate 582,
which is a 1/2 wavelength plate. The optical axis of the first
phase plate 582 is tilted at about 22.5 degrees from the
polarization axis of the first polarizing plate 585. An
intersection angle between the optical axis of the first phase
shift plate 582 and the polarization axis of the first polarizing
plate 585 is about 22.5 degrees.
[0102] The axis direction of the 45 degree rotated and linearly
polarized light after passing through the first phase shift plate
582, is substantially equivalent to the polarization axis direction
of the second polarizing plate 581. Accordingly, the 45 degree
rotated and linearly polarized light is emitted to the outside
after passing through the second polarizing plate 581 without
substantial loss.
[0103] Such a structure discharges the light emitted from the
organic light emitting element L1 to the outside without
substantial loss. A related structure, having one polarizing plate
and one phase shift plate arranged, discharges about 40% of light
emitted from an organic light emitting element L1. It is confirmed,
through experiments, that the organic light emitting diode (OLED)
display 100 according to the first exemplary embodiment
effectively, discharges about 60% to 80% of light emitted from the
organic light emitting element L1 through the optical unit 58.
Therefore, the optical unit 58 minimizes the loss of light emitted
from the organic emission layer 545 and discharged to the
outside.
[0104] Since the organic light emitting diode (OLED) display 100
efficiently discharges the light emitted from the organic emission
layer 545 to the outside, power for driving the organic emission
layer 545 is reduced. Thus, the lifespan of the organic light
emitting diode (OLED) display 100 is improved.
[0105] Although the optical unit 58 is disposed on the organic
light emitting unit L1 in the organic light emitting diode (OLED)
display 100 according to the first exemplary embodiment, the
optical unit 58 may be disposed on a light emitting unit, e.g., a
liquid crystal display (LCD) or a plasma display panel (PDP), or
disposed on a light emitting unit in another exemplary
embodiment.
[0106] An organic light emitting diode (OLED) display 200,
according to the second exemplary embodiment, will be described
with reference to FIG. 9.
[0107] FIG. 9 is a cross-sectional view illustrating an organic
light emitting diode (OLED) display according to the second
exemplary embodiment.
[0108] As shown in FIG. 9, the organic light emitting diode (OLED)
display 200, according to the second exemplary embodiment, includes
a first substrate 51, a second substrate 52 cohered with the first
substrate 51, and an optical unit 59.
[0109] The optical unit 59 includes a first polarizing plate 595, a
second polarizing plate 591, and a plurality of phase shift plates
592 and 593.
[0110] The first polarizing plate 595 is disposed on an organic
light emitting element L1. The second polarizing plate 591 is
disposed on the first polarizing plate 595. The plurality of phase
shift plates 592 to 593 are disposed between the first polarizing
plate 595 and the second polarizing plate 591. The plurality of
phase shift plates includes a fourth phase shift plate 592,
disposed between the first polarizing plate 595 and the second
polarizing plate 591, and a fifth phase shift plate 593, disposed
between the first polarizing plate 595 and the fourth phase shift
plate 592. The fifth phase shift plate 593 and the fourth phase
shift plate 592 are sequentially stacked on the first polarizing
plate 595.
[0111] The optical unit 59 further includes an additional phase
shift plate 596 disposed between the first polarizing plate 595 and
the organic light emitting element L1. The additional phase shift
plate is referred to as the sixth phase shift plate 596. However,
the second exemplary embodiment is not limited thereto. Therefore,
the sixth phase shift plate 596 may be omitted.
[0112] An intersection angle between the polarization axis of the
first polarizing plate 595 and the polarization axis of the second
polarizing plate 591 is about 45 degrees.
[0113] The fourth phase shift plate 592 is a 1/2 wavelength plate.
The fourth phase shift plate 592 has an optical axis tilted at a
predetermined angle in a range from about 10 degrees to about 20
degrees from the polarization axis of the second polarizing plate
591. The intersection angle between the optical axis of the fourth
phase shift plate 592 and the polarization axis of the second
polarizing plate 591 is in a range of about 10 degrees to about 20
degrees. The intersection angle between the optical axis of the
fourth phase shift plate 592 and the polarization axis of the first
polarizing plate 595 is in a range of about 25 degrees to about 35
degrees.
[0114] The fifth phase shift plate 593 is a 1/4 wavelength plate.
The fifth phase shift plate 593 has an optical axis tilted at a
predetermined angle in a range of about 70 degrees to about 80
degrees from the polarization axis of the second polarizing plate
591. The intersection angle between the optical axis of the fifth
phase shift plate 593 and the polarization axis of the second
polarizing plate 591 is in a range of about 70 degrees to about 80
degrees. The intersection angle between the optical axis of the
fifth phase shift plate 593 and the polarization axis of the first
polarizing plate 595 is in a range of about 25 degrees to about 35
degrees.
[0115] The sixth phase shift plate 596 is a 1/4 wavelength. The
sixth phase shift plate 596 has an optical axis tilted at a
predetermined angle in a range of about 40 degrees to about 50
degrees from the polarization axis of the reflective first
polarizing plates 595.
[0116] The organic light emitting diode (OLED) display 200
effectively suppresses external light reflection. Therefore, the
image visibility displayed by the organic light emitting element L1
is improved and, at the same time, the loss of light discharged to
the outside from the organic emission layer 545 is minimized. The
display characteristics of the organic light emitting diode (OLED)
display 200 are improved.
[0117] The organic light emitting diode (OLED) display 200
efficiently discharges light emitted from the organic emission
layer 545 to the outside. Accordingly, the power consumption is
reduced, and the lifespan is improved.
[0118] A fundamental concept of an optical unit 59 of the organic
light emitting diode (OLED) display, according to the second
exemplary embodiment, that suppresses external light reflection and
minimizes the loss of light discharged to the outside from the
organic emission layer 545, will be described with reference to
FIG. 10 to FIG. 13.
[0119] The operation of the optical unit will be described based on
the optical unit 59. The optical unit 59 is arranged to minimize
the loss of blue light and discharge the blue light emitted from
the organic light emitting element L1 to the outside. This
embodiment is similar to the first exemplary embodiment.
[0120] When other visible light passes through the optical unit 59,
other visible light does not have much different behavior than blue
light. While passing through the optical unit 59, other visible
light has similar behavior to that of blue light. Other visible
light does have slightly different behavior from blue light because
other visible light has different wavelengths than blue light. As
described in the first exemplary embodiment, when other visible
light passes through the optical unit 59, unlike blue light, other
visible light has decreasing transmittance.
[0121] A path of light flowing from the outside into the inside
through an optical unit will be described with reference to FIG. 10
to FIG. 11.
[0122] FIG. 10 and FIG. 11 are a cross-sectional view and a
schematic diagram illustrating a path of light flowing from the
outside into the inside of the organic light emitting diode (OLED)
display according to the second exemplary embodiment.
[0123] While passing through the second polarizing plate 591, as
shown in FIG. 10 and FIG. 11, light having various phases is
linearly polarized to a polarization axis direction of the second
polarizing plate 591. While passing through the fourth phase shift
plate 592, which is a 1/2 wavelength plate, the linearly polarized
light rotates about 30 degrees. The optical axis of the fourth
phase shift plate 592 is tilted at about 15 degrees from the
polarization axis of the second polarizing plate 591. The
intersection angle between the optical axis of the fourth phase
shift plate 592 and the polarization axis of the second polarizing
plate 591 is about 15 degrees.
[0124] The 30 degree rotated and linearly polarized light is
circularly polarized while passing through the fifth phase shift
plate 593, which is a 1/4 wavelength plate. An optical axis of the
fifth phase shift plate 593 is tilted at about 75 degrees from the
polarization axis of the second polarizing plate 591. The
intersection angle between the optical axis of the fifth phase
shift plate 593 and the polarization axis of the second polarizing
plate 591 is about 75 degrees.
[0125] Since an intersection angle between the axis direction of
the 30 degree rotated and linearly polarized light and the optical
axis direction of the fifth phase shift plate 593 is about 45
degrees, the light is circularly polarized, while passing through
the fifth phase shift plate 593.
[0126] While passing through the first polarizing plate 595, the
circularly polarized light, after passing through the fifth phase
shift plate 593, is linearly polarized to the polarization
direction of the first polarizing plate 595. Non-polarized light is
absorbed at the first polarizing plate 595. Among the circularly
polarized light, some light having components matching the
polarization axis of the first polarizing plate 595 passes through
the first polarizing plate 595. The remaining light is absorbed and
eliminated at the first polarizing plate 595 because the remaining
light does not match the polarization. A smaller amount of external
light is absorbed and eliminated at the first polarizing plate 595,
compared to the external light passing through the second
polarizing plate 591, because the first polarizing plate 595 has
higher transmittance and a lower polarization degree than the
second polarizing plate 591. The loss of light becomes smaller when
the light passes through the first polarizing plate 595.
[0127] Since the circularly polarized light is eliminated, while
passing through the first polarizing plate 595, the organic light
emitting diode (OLED) display 200 can suppress the external light
reflection.
[0128] While passing through the sixth phase shift plate 596, the
linearly polarized light, after passing through the first
polarizing plate 595, is circularly polarized again and reflected
at electrodes 544 and 546 of the organic light emitting element L1.
The axis direction of the circularly polarized light is changed by
about 180 degrees. The light may be reflected, not only by the
electrodes 544 and 546 of the organic light emitting element L1,
but also by various metal wires.
[0129] While passing through the sixth phase shift plate 596, the
circularly polarized light, with the axis direction changed by 180
degrees is linearly polarized again. The linearly polarized light
is absorbed and eliminated at the first polarizing plate 595.
[0130] The remaining light, passing through the first polarizing
plate 595, passes through the sixth phase shift plate 596, is
reflected by the organic light emitting element L1, passes through
the sixth phase shift plate 596 again, and is eliminated at the
first polarizing plate 595. Accordingly, the organic light emitting
diode (OLED) display 200 suppresses external light reflection and
improves the visibility thereof.
[0131] A path of light emitted from an organic emission layer (545,
FIG. 9) to the outside will be described with reference to FIG. 12
and FIG. 13.
[0132] FIG. 12 and FIG. 13 are a cross-sectional view and a
schematic diagram illustrating a path of light emitted from the
organic light emitting element of the organic light emitting diode
(OLED) according to the second exemplary embodiment.
[0133] As shown in FIG. 12 and FIG. 13, the light emitted from the
organic emission layer 545 sequentially passes through the second
electrode 546 and the sixth phase shift plate 596. The light has
various phases.
[0134] The light, having passed through the sixth phase shift plate
596, propagates to the first polarizing plate 595. While passing
through the reflective first polarizing plate 595, among light
having passed through the sixth phase shift plate 596, light
matched with the polarization axis of the first polarizing plate
595 is linearly polarized. A smaller amount of the internal light
is eliminated at the first polarizing plate 595, compared to the
internal light passing through the second polarizing plate 591,
because the first polarizing plate 595 has higher transmittance and
a lower polarization degree that the second polarizing plate 591.
The loss of light becomes smaller when the light passes through the
first polarizing plate 595.
[0135] While passing through the fifth phase shift plate 593 which
is a 1/4 wavelength plate, the linearly polarized light, after
passing through the first polarizing plate 595, is circularly
polarized. An optical axis of the fifth phase shift plate 593 is
tilted at about 30 degrees from the polarization axis of the first
polarizing plate 595. The intersection angle of the optical axis,
of the fifth phase shift plate 593, and the polarization axis of
the first polarizing plate 595 is about 30 degrees.
[0136] While passing through the fifth phase shift plate 593, since
the intersection angle between the axis direction of the linearly
polarized light, having passed through the first polarizing plate
595, and the optical axis direction of the fifth phase shift plate
593 is about 30 degrees, the light is circularly polarized. The
light becomes circularly polarized when the intersection angle
between the axis direction of the linearly polarized light and the
optical axis of the fifth phase shift plate is about 45 degrees.
However, the light becomes elliptically polarized light when the
intersection angle is about 30 degrees.
[0137] While passing through the fourth phase shift plate 592,
which is a 1/2 wavelength plate, the circular polarized light,
after passing through the fifth phase shift plate 593, rotates
about 15 degrees with the circularly polarized state sustained. The
optical axis of the fourth phase shift plate 592 is tilted around
30 degrees from the polarization axis of the first polarizing plate
595. An intersection angle between the optical axis of the fourth
phase shift plate 592 and the polarization axis of the first
polarizing plate 595 is about 30 degrees.
[0138] The longitudinal axis direction of the 15 degree rotated and
elliptically polarized light, after passing through the fourth
phase shift plate 592, is similar to the polarization axis
direction of the second polarizing plate 591. Even though the
rotated and elliptically polarized light is not linearly polarized
light, the significant amount of the 15 degree rotated and
elliptically polarized light passes through the second polarizing
plate 591 to the outside.
[0139] The light emitted from the organic light emitting element L1
is effectively discharged to the outside through the optical unit
59. Accordingly, the loss of the light discharged from the organic
emission layer 545 to the outside can be minimized.
[0140] The organic light emitting diode (OLED) display 200 can
efficiently discharge light emitted from the organic emission layer
545 to the outside. Accordingly, the driving power of the organic
emission layer 545 is reduced. The lifespan of the organic light
emitting diode (OLED) display 200 is improved.
[0141] The optical unit 59 of the organic light emitting diode
(OLED) display 200 according to the second exemplary embodiment,
has fewer phase shift plates 592 and 593 compared to the organic
light emitting diode (OLED) display 100 according to the first
exemplary embodiment. Accordingly, an organic light emitting diode
(OLED) display 200 requires less manufacturing cost and a shorter
manufacturing time.
[0142] A conventional organic light emitting diode (OLED) display
includes organic light emitting diodes. Organic light emitting
diodes display images by emitting light. However, electrodes
forming an organic light emitting diode reflect external light. The
display quality of an organic light emitting diode display may be
deteriorated due to reflected external light.
[0143] A polarizing plate and a phase shift plate of the
conventional art have been disposed on an organic light emitting
diode to suppress external light reflection. When light emitted
from the organic emission layer is emitted through a polarizing
plate and a phase shift plate, a method for suppressing external
light reflection has a significant loss of light emitting from an
organic emission layer.
[0144] Present embodiments may be made in an effort to provide an
optical unit and an organic light emitting diode (OLED) display,
having the advantages of suppressing reflection of external light
and, at the same time, minimizing the loss of light emitted from an
organic light emitting element.
[0145] Exemplary embodiments of the inventive concept have been
disclosed herein, and although specific terms are employed, they
are used and are to be interpreted in a generic and descriptive
sense only and not for purpose of limitation. Accordingly, it will
be understood by those of ordinary skill in the art that various
changes in form and details may be made without departing from the
spirit and scope of the inventive concept as set forth in the
following claims.
* * * * *