KR102450191B1 - organic light emitting display device - Google Patents

Abstract

The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device capable of preventing a decrease in contrast by minimizing reflection of external light.
A feature of the present invention is that the polarizing plate of the OLED has a flat characteristic and includes a retardation plate containing a light absorber having a main absorption wavelength band of 420 to 450 nm.
Through this, the retardation plate has reverse wavelength dispersion characteristics, so that it is possible to improve the black color of the OLED, thereby improving the contrast, and in particular, it is possible to implement deep black, thereby further improving the contrast.
In addition, since there is no need to use a retardation plate having an expensive reverse dispersion characteristic, the process cost can be reduced, and in order to implement the reverse dispersion characteristic, there is no need to laminate and use two or more retardation films having different retardation values. , the simplification of the process and the cost of the process can also be reduced, and also the problem that the optical properties are deteriorated due to the use of two retardation films can be prevented.

Description

Organic light emitting diodes display

The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device capable of preventing a decrease in contrast by minimizing reflection of external light.

Recently, as society enters the information age in earnest, interest in information displays that process and display a large amount of information is heightened, and as the demand to use portable information media increases, the display field has developed rapidly. In response to this, various light and thin flat panel display devices have been developed and are in the spotlight.

Specific examples of such flat panel display devices include a liquid crystal display device (LCD), a plasma display panel device (PDP), a field emission display device (FED), and an electroluminescence display device. (Electroluminescence Display device: ELD), organic light emitting diodes (OLED), etc. are mentioned. These flat panel display devices show excellent performance of thinness, light weight, and low power consumption. CRT) is rapidly being replaced.

Among the above flat panel display devices, an organic light emitting display device (hereinafter referred to as OLED) is a self-luminous device, and since it does not require a backlight used in a liquid crystal display device, which is a non-light emitting device, it is possible to have a light weight and thin shape.

In addition, the viewing angle and contrast ratio are superior to those of the liquid crystal display device, and it is advantageous in terms of power consumption, direct current low voltage driving is possible, the response speed is fast, and since the internal components are solid, it is strong against external shocks and has a wide operating temperature range. It has advantages.

In particular, since the manufacturing process is simple, there is an advantage that the production cost can be greatly reduced compared to the conventional liquid crystal display device.

OLEDs having these characteristics are largely divided into a passive matrix type and an active matrix type. In the passive matrix type, a device is formed in a matrix form while crossing signal lines, whereas in the active matrix type, the pixels are A thin film transistor, which is a switching element for turning on/off regions, is positioned for each pixel region.

Recently, the passive matrix type has many limiting factors such as resolution, power consumption, lifespan, etc., so research on active matrix type OLED capable of realizing high resolution or a large screen is being actively conducted.

1 is a diagram schematically showing a cross-section of a typical active matrix type OLED.

As shown, in the OLED 10 , the substrate 1 on which the driving thin film transistor DTr and the light emitting diode 14 are formed is encapsulated by the protective film 12 .

Looking at this in more detail, a driving thin film transistor DTr is formed on the upper portion of the substrate 1 for each pixel region SP, and a first electrode 11 and a first electrode connected to each driving thin film transistor DTr are formed. An organic light emitting layer 13 emitting light of a specific color is formed on the electrode 11 , and a second electrode 15 is formed on the organic light emitting layer 13 .

The first and second electrodes 11 and 15 and the organic light emitting layer 13 formed therebetween constitute the light emitting diode 14 . In this case, the OLED 10 having such a structure includes the first electrode 11 as an anode and the second electrode 15 as a cathode.

At this time, a separate color filter emitting red (R), green (G), blue (B), and white (W) colors is provided for each pixel area SP, and the white light implemented in the organic light emitting layer 13 is Through the color filter, each pixel area SP emits red (R), green (G), blue (B), and white (W) colors.

A protective film 12 in the form of a thin film is formed on the driving thin film transistor DTr and the light emitting diode 14 , and the OLED 10 is encapsulated through the protective film 12 .

On the other hand, the OLED 10 has a disadvantage in that the contrast is greatly reduced according to the intensity of external light. Accordingly, in order to prevent a decrease in contrast due to external light, a polarizing plate 20 for blocking external light reflection is attached to the upper portion of the substrate 1 from which light is emitted.

That is, the OLED 10 improves the contrast by locating the polarizing plate 20 for blocking external light incident from the outside in the transmission direction of the light emitted through the organic light emitting layer 13 .

The polarizing plate 20 is a circularly polarizing plate for blocking external light, and includes a retardation plate (not shown) and a linear polarizing plate (not shown) attached to the outer surface of the substrate 1 .

Here, the retardation plate (not shown) can be divided into those having a normal wavelength dispersion characteristic, a flat wavelength dispersion characteristic, and a reverse wavelength dispersion characteristic according to the wavelength dispersion characteristic, The retardation plate (not shown) having a constant wavelength dispersion characteristic decreases the refractive index anisotropy as the wavelength increases, and the retardation plate (not shown) having a flat wavelength dispersion characteristic has a constant refractive index anisotropy as the wavelength increases. do.

Therefore, the retardation plate (not shown) having such a constant wavelength dispersion characteristic or a flat wavelength dispersion characteristic decreases the phase delay as the wavelength increases.

That is, since the retardation plate (not shown) having a normal wavelength dispersion characteristic or a flat wavelength dispersion characteristic has a large difference between the wavelength and the phase difference value of the incident light measured at a short wavelength and a long wavelength, the transmittance becomes non-uniform, and as a result, the visibility becomes poor. The color changes depending on the viewing direction.

Accordingly, the contrast of the OLED 10 is lowered.

On the other hand, in the case of a retardation plate (not shown) having reverse wavelength dispersion characteristics, in which the refractive index anisotropy increases as the wavelength increases, the retardation value generated as the wavelength of the incident light increases as well, so that the transmittance becomes uniform regardless of the wavelength, Since there is almost no change in color and luminance, the reflected color appears black in a state in which no voltage is applied.

Therefore, in the case of a retardation plate (not shown) having reverse wavelength dispersion characteristics, deep black can be implemented, and thus contrast is further improved.

However, a retardation plate (not shown) having reverse wavelength dispersion characteristics has a problem of high price.

Therefore, two or more retardation films (not shown) having the same wavelength dispersion characteristics and different retardation values are laminated using an adhesive or adhesive at a specific optical axis angle, so that the two retardation films (not shown) have reverse wavelength dispersion characteristics. Although it is intended to function as a retardation plate (not shown) having If the optical axis of the retardation film is not accurately arranged, the reverse wavelength dispersion characteristic does not appear, which causes a very difficult problem in manufacturing.

The present invention is to solve the above problems, and a first object of the present invention is to improve the contrast by improving the reflected color of the OLED in a state in which no voltage is applied.

In addition, a second object is to reduce process costs and simplify the process by providing a retardation plate having reverse wavelength dispersion characteristics without using an adhesive or adhesive.

In order to achieve the object as described above, the present invention provides a display panel including a first electrode, an organic light emitting layer, and a second electrode, a linear polarizing plate positioned above the display panel and transmitting only linearly polarized light in a predetermined direction, and the display; Provided is an organic light emitting diode display including a retardation plate positioned between a panel and the linear polarizer, having flat dispersion characteristics, and including a light absorber having a main absorption wavelength band of 420 to 450 nm.

At this time, the retardation plate is composed of a first retardation layer having a flat dispersion characteristic, and a second retardation layer including a light absorber having a main absorption wavelength band of 420 to 450 nm, and the second retardation layer is a transparent resin. absorbents are included.

And, the retardation plate is made by stretching a cyclo-olefin polymer or cyclic olefinpolymer (COP) film, and the light absorber is hydroxy benzotriazole (HB), tris-resorcinol-tri It consists of at least one selected from tris-Resorcinol-Triazine chromophore (TRTC) and hydroxyphenyl-benzotriazole chromophore (HBC) series.

And, the transparent resin is made of at least one selected from the group consisting of polyester-based, acrylic-based, polyurethane-based, melamine-based, polyvinyl alcohol-based and oxazoline-based binder resins, and the linear polarizing plate includes a polarizing layer and the polarizing layer. It includes first and second TAC films positioned on both sides, and a surface treatment layer is provided on the outside of the linear polarizing plate.

An adhesive is interposed between the linearly polarizing plate and the retardation plate and between the retardation plate and the display panel.

As described above, according to the present invention, the polarizing plate of the OLED has flat characteristics and includes a retardation plate containing a light absorber having a main absorption wavelength band of 420 to 450 nm, so that the retardation plate has reverse wavelength dispersion characteristics, It is possible to improve the black color of the OLED, so there is an effect of improving the contrast.

In addition, since there is no need to use a retardation plate having an expensive reverse dispersion characteristic, there is an effect of reducing the process cost. Since there is no need to do this, there is an effect of simplifying the process and reducing the cost of the process.

In addition, there is an effect that can also prevent the problem that the optical properties are lowered by using the two retardation films.

1 is a diagram schematically showing a cross section of a typical active matrix type OLED.
2 is a cross-sectional view schematically illustrating an OLED according to a first embodiment of the present invention.
Figure 3 is an enlarged cross-sectional view of a part of Figure 2;
4A is a spectrum obtained by measuring the reflected luminance in a black state of an OLED including a retardation plate having flat dispersion characteristics.
FIG. 4B is a graph of measurement of reflected luminance in a black state of an OLED including a retardation plate having flat dispersion characteristics; FIG.
5A is a spectrum obtained by measuring the reflected luminance in a black state of an OLED including a retardation plate having inverse dispersion characteristics.
FIG. 5b is a graph of measurement of reflected luminance in a black state of an OLED including a retardation plate having inverse dispersion characteristics; FIG.
6A is a spectrum obtained by measuring the reflected luminance in a black state of an OLED including the retarder according to the first embodiment of the present invention.
6B is a graph of measuring the reflected luminance in a black state of an OLED including the retardation plate according to the first embodiment of the present invention.
7A is a spectrum obtained by measuring reflected luminance in a black state of an OLED including a retardation plate having positive dispersion characteristics.
FIG. 7b is a spectrum obtained by measuring the reflected luminance in a black state of an OLED having a positive dispersion characteristic and including a retarder containing a light absorber having a main absorption wavelength band of 420 to 450 nm therein.
8 is a spectrum obtained by measuring the reflected luminance in a black state of an OLED including a retardation plate having a flat dispersion characteristic and containing a light absorber having a main absorption wavelength band of 580 to 600 nm therein.
Fig. 9 is a schematic diagram schematically showing an OLED according to a second embodiment of the present invention;

Hereinafter, an embodiment according to the present invention will be described in detail with reference to the drawings.

2 is a cross-sectional view schematically illustrating an OLED according to a first embodiment of the present invention, and FIG. 3 is an enlarged cross-sectional view of a part of FIG. 2 .

On the other hand, the OLED 100 according to the first embodiment of the present invention is divided into a top emission type and a bottom emission type according to the transmission direction of the emitted light. Hereinafter, in the present invention, the bottom emission type Let me explain the method as an example.

In addition, for convenience of description, an area in which the driving thin film transistor DTr is formed is defined as a non-emission area DA, and an area in which the light emitting diode 114 is formed is defined as an emission area EA.

As shown, the OLED 100 according to the first embodiment of the present invention can be largely divided into an OLED display panel 110 and a polarizing plate 200. The OLED display panel 110 includes a driving thin film transistor ( DTr) and the substrate 101 on which the light emitting diode 114 is formed is encapsulated by the protective film 120 .

Here, looking at the OLED display panel 110 in more detail, the semiconductor layer 103 is located in the non-emission area DA of each pixel area SP on the substrate 101, and the semiconductor layer 103 is made of silicon. The central portion is composed of an active region 103a constituting a channel, and source and drain regions 103b and 103c doped with a high concentration of impurities on both sides of the active region 103a.

A gate insulating layer 104 is positioned on the semiconductor layer 103 .

On the upper portion of the gate insulating layer 104 , a gate electrode 105 corresponding to the active region 103a of the semiconductor layer 103 and a gate wiring (not shown) extending in one direction (not shown) are provided.

In addition, the first interlayer insulating film 109a is positioned on the upper portion including the gate electrode 105 and the gate wiring (not shown), and in this case, the first interlayer insulating film 109a and the lower gate insulating film 104 are active. First and second semiconductor layer contact holes 116 exposing the source and drain regions 103b and 103c located on both side surfaces of the region 103a, respectively, are provided.

Next, on the upper portion of the first interlayer insulating film 109a including the first and second semiconductor layer contact holes 116 , the source and drain regions ( Source and drain electrodes 106a and 106b in contact with 103b and 103c, respectively, are provided.

A second interlayer insulating layer 109b is positioned on the first interlayer insulating layer 109a exposed between the source and drain electrodes 106a and 106b and the two electrodes 106a and 106b.

At this time, the semiconductor layer 103 including the source and drain electrodes 106a and 106b and the source and drain regions 103b and 103c in contact with the electrodes 106a and 106b, and the gate positioned on the semiconductor layer 103 . The insulating film 104 and the gate electrode 105 form a driving thin film transistor DTr.

On the other hand, although not shown in the drawing, a data line (not shown) that intersects the gate line (not shown) and defines the pixel area SP is located, and the switching thin film transistor (not shown) is the same as the driving thin film transistor DTr. As a structure, it is connected to the driving thin film transistor (DTr).

In addition, as for the switching thin film transistor (not shown) and the driving thin film transistor (DTr), the top gate type in which the semiconductor layer 103 is made of a polysilicon semiconductor layer or an oxide semiconductor layer is shown as an example, and variations thereof For example, it may be provided as a bottom gate type made of pure and impurity amorphous silicon.

In addition, the driving thin film transistor DTr may have a characteristic in which the threshold voltage is shifted by light. In order to prevent this, a light blocking layer (not shown) may be further provided under the semiconductor layer 103 .

A light blocking layer (not shown) is provided between the substrate 101 and the semiconductor layer 103 to block light incident to the semiconductor layer 103 through the substrate 101, thereby preventing the driving thin film transistor DTr by external light. Minimize or prevent threshold voltage change.

In addition, the substrate 101 is mainly made of a glass material, but may be made of a transparent plastic material that can be bent or bent, for example, a polyimide material. When a plastic material is used as the substrate 101, polyimide having excellent heat resistance that can withstand high temperatures may be used in consideration of the high-temperature deposition process being performed on the substrate 101. A buffer layer (not shown) may be further provided on the front surface of the substrate 101 .

The buffer layer (not shown) blocks the material contained in the substrate 101 from diffusing into the driving and switching thin film transistor (DTr, not shown) during a high-temperature process during the manufacturing process of the driving and switching thin film transistor (DTr, not shown). play a role

In addition, the buffer layer (not shown) may also serve to prevent external moisture or moisture from penetrating into the light emitting diode 114 . As such, the buffer layer (not shown) may be made of silicon oxide or silicon nitride.

In addition, the wavelength conversion layer 107 is positioned above the second interlayer insulating film 109b corresponding to the emission area EA of each pixel area SP, and the wavelength conversion layer 107 is formed from the light emitting diode 114 . A color filter that transmits only a wavelength of a color set in the pixel region SP among white light emitted toward the substrate 101 is included.

That is, the wavelength conversion layer 107 may transmit only red, green, or blue wavelengths. For example, one unit pixel may be composed of adjacent first to third pixel regions SP, and in this case, the wavelength conversion layer 107 provided in the first pixel region is provided in the red color filter and in the second pixel region. The provided wavelength conversion layer 107 may include a green color filter, and the wavelength conversion layer 107 provided in the third pixel region may include a blue color filter.

In addition, one unit pixel may further include a white pixel in which the wavelength conversion layer 107 is not formed.

The wavelength conversion layer 107 according to another example includes quantum dots having a size that emits light of a color set in each pixel area SP by re-emitting according to white light emitted from the light emitting diode 114 toward the substrate 101 . can do. Here, the quantum dots may be selected from CdS, CdSe, CdTe, ZnS, ZnSe, GaAs, GaP, GaAs-P, Ga-Sb, InAs, InP, InSb, AlAs, AlP, or AlSb.

For example, the wavelength conversion layer 107 of the first pixel region is a quantum dot of CdSe or InP, the wavelength conversion layer 107 of the second pixel region is a quantum dot of CdZnSeS, and the wavelength conversion layer 107 of the third pixel region. Silver may include quantum dots of ZnSe, respectively. As such, the OLED 100 in which the wavelength conversion layer 107 includes quantum dots may have a high color gamut.

The wavelength conversion layer 107 according to another example may be formed of a color filter containing quantum dots.

Accordingly, the OLED 100 of the present invention emits R, G, B, and W colors for each pixel area SP, thereby realizing a full color with high luminance.

An overcoating layer 108 having a drain contact hole 117 exposing the drain electrode 106b together with the second interlayer insulating film 109b is positioned on the wavelength shifting layer 107, and the overcoating layer 108 is upper part. The furnace is connected to the drain electrode 106b of the driving thin film transistor DTr and, for example, a first electrode 111 made of a material having a relatively high work function value and forming the anode of the light emitting diode 114 is located.

The first electrode 111 is a metal oxide such as indium-tin-oxide (ITO) or indium-zinc-oxide (IZO), and a metal and oxide such as ZnO:Al or SnO ₂ :Sb. of poly(3-methylthiophene), poly[3,4-(ethylene-1,2-dioxy)thiophene](PEDT), polypyrrole and conductive polymers such as polyaniline. In addition, it may be made of carbon nanotubes (CNTs), graphene, silver nanowires, and the like.

The first electrode 111 is positioned for each pixel region SP, and a bank 119 is positioned between the first electrodes 111 positioned for each pixel region SP. That is, the first electrode 111 has a structure separated for each pixel area SP by using the bank 119 as a boundary for each pixel area SP.

And the organic light emitting layer 113 is located on the upper portion of the first electrode 111, the organic light emitting layer 113 may be composed of a single layer made of a light emitting material, in order to increase the luminous efficiency, a hole injection layer (hole injection layer) , a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer.

In addition, the second electrode 115 forming a cathode is positioned on the entire surface of the organic light emitting layer 113 .

The second electrode 115 may be made of a material having a relatively small work function value. At this time, the second electrode 115 has a double-layer structure, a single layer of an alloy composed of a first metal made of Ag, etc., which is a metal material having a low work function, and a second metal made of Mg, etc. in a certain ratio, or a plurality of layers thereof. can be configured.

When a predetermined voltage is applied to the first electrode 111 and the second electrode 115 according to the selected signal, the OLED display panel 110 includes holes injected from the first electrode 111 and the second electrode 115 . Electrons provided from the electrons are transported to the organic light emitting layer 113 to form excitons, and when these excitons are transitioned from an excited state to a ground state, light is generated and emitted in the form of visible light.

At this time, since the emitted light passes through the transparent first electrode 111 and goes out, the OLED display panel 110 realizes an arbitrary image.

In addition, a protective film 120 in the form of a thin film is formed on the driving thin film transistor DTr and the light emitting diode 114 , and the OLED display panel 110 is encapsulated through the protective film 120 . )do.

Here, the protective film 120 is used by laminating at least two inorganic protective films in order to prevent external oxygen and moisture from penetrating into the OLED display panel 110 . It is preferable that an organic protective film to supplement the impact resistance of the protective film is interposed.

In a structure in which such an organic protective film and an inorganic protective film are alternately and repeatedly laminated, it is preferable that the inorganic protective film completely encloses the organic protective film because it is necessary to prevent moisture and oxygen from penetrating through the side of the organic protective film. do.

Accordingly, the OLED display panel 110 may prevent moisture and oxygen from penetrating into the OLED display panel 110 from the outside.

Through this, it is possible to prevent oxidation and corrosion of the electrode layer from occurring due to oxygen or moisture introduced into the interior, and thus the light emitting characteristic of the organic light emitting layer 113 is lowered, and the lifespan of the organic light emitting layer 113 is shortened. problems can be avoided.

In addition, current leakage and short circuit are prevented, and pixel defects can be prevented from occurring. In this way, the problem of non-uniformity in luminance or image characteristics is prevented.

In addition, the OLED 100 according to the first embodiment of the present invention has a polarizing plate 200 on the outer surface of the substrate 101 of the OLED display panel 110 through which light is transmitted to prevent a decrease in contrast due to external light. will be located

That is, the OLED 100 has a polarizing plate 200 that blocks external light incident from the outside in the transmission direction of the light emitted through the organic light emitting layer 113 when the OLED display panel 110 is in a driving mode for implementing an image. By doing so, the contrast is improved.

In this case, a transparent first adhesive layer 230a having adhesive properties may be interposed between the polarizing plate 200 and the substrate 101 .

The polarizing plate 200 is a circularly polarizing plate for blocking external light, and includes a retardation plate 210 and a linear polarizing plate 220 attached to the outer surface of the substrate 101 .

Here, the structure of the polarizing plate 200 according to the first embodiment of the present invention will be described in more detail.

That is, the polarizing plate 200 is largely composed of a linear polarizing plate 220 and a retardation plate 210 , and a first adhesive layer 230a for attaching the polarizing plate 200 to the substrate 101 of the OLED display panel 110 . and a second adhesive layer 230b for attaching the retardation plate 220 and the linear polarizing plate 210 to each other.

In this case, in the order of stacking the linear polarizing plate 220 and the retardation plate 210 , the linear polarizing plate 220 is arranged to be close to the incident direction of external light, and the retardation plate 210 is arranged inside the structure is preferable.

The linear polarizer 220 includes a polarization layer 221 for changing the polarization characteristics of light, first and second TAC films 223a formed on both sides of the polarization layer 221 to protect and support the polarization layer 221 ; 223b).

The linear polarizer 220 absorbs linearly polarized light parallel to the absorption axis of the polarization layer 221 and transmits linearly polarized light perpendicular to the absorption axis, that is, linearly polarized light parallel to the transmission axis.

The polarizing layer 221 may be formed of polyvinyl alcohol (PVA) that is stretched by dyeing iodine ions or dichroic dyes. Alternatively, the polarization layer 221 may be formed of a reactive mesogen (RM) and a dichroic dye. may include

In addition, the retardation plate 210 according to the first embodiment of the present invention includes a light absorber 211 having a main absorption wavelength band of 420 to 450 nm, and flat wavelength dispersion (hereinafter referred to as flat dispersion) characteristics. It is characterized by having.

The retardation plate 210 may be a half wave plate (HWP) that has a phase delay of λ/2 to change the polarization direction of incident light. Accordingly, the linearly polarized light passing through the retardation plate 210 is changed to the linearly polarized light rotated by 90 degrees.

For example, the retardation plate 210 having flat dispersion characteristics may be formed by stretching a cyclo-olefin polymer or cyclic olefin polymer (COP) film.

And the light absorber 210 has a main absorption wavelength band of 420 to 450 nm, hydroxy benzotriazole (HB), tris-resorcinol-triazine chromophore (Tris-Resorcinol-Triazine chromophore, TRTC) , hydroxyphenyl-benzotriazole chromophore (Hydroxylphenyl-benzotriazole chromophore, HBC) may be composed of one or a combination of two or more selected from the series.

Through this, in the OLED 100 according to the first embodiment of the present invention, the retardation plate 210 of the polarizing plate 200 has reverse wavelength dispersion characteristics. We will look at this in more detail later.

A surface treatment layer 240 may be further included on the outside of the polarizing plate 200 , that is, on the outside of the linear polarizing plate 220 . The surface treatment layer 240 is glare including silica beads (not shown). It may be an anti-glare layer or a hard coating layer for preventing damage to the surface of the polarizing plate 200 .

Through this, the OLED 100 according to the first embodiment of the present invention can minimize the reflection of external light through the polarizing plate 200 to prevent a decrease in contrast.

In particular, since the retardation plate 210 of the polarizing plate 200 includes a light absorber 211 having a main absorption wavelength band of 420 to 450 nm, and has flat dispersion characteristics, it exhibits reverse dispersion characteristics, so that the Contrast can be further improved, and process costs can be reduced, and process simplification is also brought about.

Here, the principle of implementing the inverse dispersion characteristic of the retarder 210 according to the first embodiment of the present invention will be described in more detail.

The “in-plane retardation Re” of the retardation plate 210 means a value measured by the following (Equation 1).

(Equation 1)

Re = ( nx - ny )×D

(Here, nx is the refractive index in the axis (slow axis) direction representing the maximum refractive index in the plane of the retardation plate 210, ny is the refractive index in the direction orthogonal to the slow axis, and D is the thickness of the retardation plate 210 (nm) ) means).

In addition, the in-plane retardation (Re) of the retardation plate 210 is dispersed depending on the wavelength of the transmitted light, and the "wavelength dispersion ratio" of the retardation plate 210 is the in-plane retardation (Re) at the center wavelength of 550 nm by the following (Equation 2) Re) means the fraction of the in-plane retardation (Re) at each spectral wavelength with respect to the value.

(Equation 2)

Wavelength dispersion ratio = Re / Re (550)

(Here, Re is the retardation plate 210 in-plane retardation (nm) at each spectral wavelength, and Re (550) means the retardation plate 210 in-plane retardation (nm) at a wavelength of 550 nm.)

Here, the optical characteristics of the retardation plate 210 may be expressed as wavelength dispersion characteristics of reverse dispersion characteristics, flat dispersion characteristics, and normal dispersion characteristics according to the degree of increase or decrease of the wavelength dispersion ratio.

That is, as the wavelength becomes longer in the visible ray (400-800 nm) region, the in-plane retardation (Re) rapidly decreases and at the same time the maximum or minimum value of the wavelength dispersion ratio is out of the range of 1±0.1, the reverse dispersion ( Reverse wavelength dispersion) characteristics, while the in-plane retardation (Re) is gently monotonically decreased, the maximum or minimum value of the wavelength dispersion ratio is within the range of 1±0.1, or the in-plane retardation (Re) is gently monotonically increased and the maximum wavelength dispersion ratio is at the same time If the value or the minimum value is within the range of 1±0.1, flat wavelength dispersion characteristics and the in-plane retardation (Re) increase rapidly, and at the same time, if the maximum or minimum value of the wavelength dispersion ratio is outside the range of 1±0.1, normal dispersion It can be said that it has a (normal wavelength dispersion) characteristic.

In the reverse dispersion characteristic, the refractive index anisotropy increases as the wavelength increases, in the positive dispersion characteristic, the refractive index anisotropy decreases as the wavelength increases, and in the flat dispersion characteristic, the refractive index anisotropy is constant as the wavelength increases.

Therefore, since the difference between the wavelength and the phase difference value of the incident light measured at a short wavelength and a long wavelength is large for a retardation plate having a normal dispersion characteristic or a flat dispersion characteristic, the transmittance becomes non-uniform, and as a result, the visibility becomes worse, depending on the viewing direction. color will be wrong.

Accordingly, the contrast of the OLED is lowered.

On the other hand, in the case of a retardation plate having reverse dispersion characteristics, in which the refractive index anisotropy increases as the wavelength increases, the retardation value generated as the wavelength of incident light increases as the wavelength increases, so that the transmittance becomes uniform regardless of the wavelength, so the color and luminance change is almost absent, so that the reflection color appears black in a state in which no voltage is applied.

Accordingly, in the case of a retardation plate having an inverse dispersion characteristic, it is possible to implement deep black, so that the contrast is further improved.

4A to 4B are spectra and graphs measuring the reflected luminance in black state of an OLED including a retardation plate having flat dispersion characteristics, and FIGS. 5A to 5B are black OLED including a retardation plate having reverse dispersion characteristics. It is a spectrum and graph measuring the reflected luminance of the state.

First, comparing FIGS. 4A and 5A , an OLED including a retardation plate having flat dispersion characteristics has non-uniform reflected luminance from both the front and side surfaces. can be seen to stand out.

On the other hand, it can be seen that the OLED including the retardation plate having the reverse dispersion characteristic has uniform reflective luminance from both the front and side surfaces, thereby showing a uniform black appearance.

If the reflected luminance is not uniform, the visual perception is deteriorated, the color is different depending on the viewing direction, and the contrast is lowered.

Here, looking at the graphs of FIGS. 4B and 5B, it can be seen that the OLED including the retardation plate having flat dispersion characteristics has higher reflective luminance in the wavelength band of 420 to 440 nm compared to the OLED including the retardation plate having inverse dispersion characteristics. have.

Therefore, the retardation plate 210 according to the first embodiment of the present invention is to include a light absorber 211 having a main absorption wavelength band of 420 to 450 nm therein while having a flat characteristic.

Through this, the retarder 210 according to the first embodiment of the present invention has an inverse dispersion characteristic.

6A to 6B are spectra and graphs obtained by measuring the reflected luminance in the black state of the OLED 100 including the retardation plate 210 according to the first embodiment of the present invention. Referring to FIG. 6A , the first embodiment of the present invention It can be seen that the OLED 100 including the retardation plate 210 according to the embodiment has uniform reflective luminance from both the front and side surfaces, thereby exhibiting a uniform black appearance.

In particular, it can be confirmed that the same black luminance characteristic is implemented when compared with the OLED including the retardation plate having the reverse dispersion characteristic of FIG. 5B , which can also be confirmed through FIGS. 6B and 5B .

That is, the retardation plate 210 according to the first embodiment of the present invention has a flat dispersion characteristic, but by including the light absorber 211 having a main absorption wavelength band of 420 to 450 nm therein, the reverse dispersion characteristic is realized. .

Accordingly, while the contrast of the OLED 100 is further improved, it is not necessary to use a retardation plate having an expensive reverse dispersion characteristic, thereby reducing the process cost.

In addition, since it is not necessary to laminate and use two or more retardation films having different retardation values in order to realize the reverse dispersion characteristics, it is possible to simplify the process and reduce the cost of the process. In particular, two retardation films are used. As a result, the problem that the optical properties are deteriorated can also be prevented.

Meanwhile, the light absorber 211 having a main absorption wavelength band of 420 to 450 nm included in the retarder 210 according to the first embodiment of the present invention absorbs light in a wavelength range of 420 to 450 nm.

At this time, when the retardation plate 210 according to the first embodiment of the present invention has a normal dispersion characteristic rather than a flat dispersion characteristic, the light absorber 211 having a main absorption wavelength band of 420 to 450 nm is included in the retardation plate. , like the retardation plate 210 of the first embodiment of the present invention, the reverse dispersion characteristic is not implemented.

That is, the attached FIG. 7a is a spectrum measuring the reflected luminance in a black state of an OLED including a retardation plate having a normal dispersion characteristic, and FIG. 7b is a normal dispersion characteristic, and the main absorption wavelength band therein is 420 to 450 nm. This is a spectrum obtained by measuring the reflected luminance of the black state of the OLED including the retardation plate containing the light absorber.

Here, referring to FIG. 7B , even if a light absorber having a main absorption wavelength band of 420 to 450 nm is included, the retardation plate having a positive dispersion characteristic has non-uniform reflected luminance at both the front and side surfaces, especially when black luminance is implemented. It can be seen that the color is blue instead of black.

In particular, compared with the spectrum measured in the black state of the reflection luminance of the OLED including the retarder having the reverse dispersion characteristic of FIG. 5B, the light absorber having the positive dispersion characteristic of FIG. 7B and the main absorption wavelength band of 420 to 450 nm It can be seen that the included retardation plate does not implement uniform black.

On the other hand, a light absorber having a main absorption wavelength band of 580 to 600 nm absorbs light in a wavelength band of 580 to 600 nm.

Even if the light absorber having the main absorption wavelength band of 580 to 600 nm is included in the retardation plate having flat dispersion characteristics, reverse dispersion characteristics are not implemented as in the retardation plate of the first embodiment of the present invention.

That is, the accompanying FIG. 8 is a spectrum obtained by measuring the reflected luminance in black state of an OLED having a flat dispersion characteristic and including a retarder containing a light absorber having a main absorption wavelength band of 580 to 600 nm therein, and the main absorption wavelength band Although the retardation plate containing the light absorber of 580 ~ 600 nm has flat dispersion characteristics, the reflected luminance is not uniform both from the front and the side. can

This is compared with the spectrum measured in the black state of the OLED including the retarder having the reverse dispersion characteristic of FIG. 5B, the light absorber having the flat dispersion characteristic of FIG. 8 and the main absorption wavelength band of 580 to 600 nm It can be seen that the included retardation plate does not implement uniform black.

Accordingly, the retardation plate 210 according to the first embodiment of the present invention has flat dispersion characteristics, and by including the light absorber 211 having a main absorption wavelength band of 420 to 450 nm, reverse dispersion characteristics can be realized.

Through this, it is possible to improve the black color of the OLED 100 , thereby improving the contrast, and in particular, it is possible to implement deep black, thereby further improving the contrast.

In addition, since there is no need to use a retardation plate having an expensive reverse dispersion characteristic, the process cost can be reduced, and in order to implement the reverse dispersion characteristic, there is no need to laminate and use two or more retardation films having different retardation values. , process simplification and process cost can also be reduced.

In particular, it is also possible to prevent the problem that the optical properties are lowered by using the two retardation films.

9 is a schematic diagram schematically illustrating an OLED according to a second embodiment of the present invention.

As shown, the OLED 100 according to the second embodiment of the present invention includes an OLED display panel 110 and a polarizing plate 200 positioned above the OLED display panel 110 .

Here, the OLED display panel 110 may have the structure shown in FIG. 3 .

A polarizing plate 200 is positioned on the outer surface of the first substrate 101 of the OLED display panel 110 to prevent a decrease in contrast caused by external light.

Here, the polarizing plate 200 according to the second embodiment of the present invention includes a retardation plate 210 and a linear polarizing plate 220 positioned on the retardation plate 210 .

That is, the polarizing plate 200 is largely divided into a linear polarizing plate 220 and a retardation plate 210 consisting of first and second retardation layers 213 and 215 . The polarizing plate 200 is a substrate of the OLED display panel 110 . A first adhesive layer 230a for attaching to ( 101 of FIG. 3 ) and a second adhesive layer 230b for attaching the retardation plate 210 and the linear polarizing plate 220 are included.

In this case, in the order of stacking the linear polarizing plate 220 and the retardation plate 210 , the linear polarizing plate 220 is arranged to be close to the incident direction of external light, and the retardation plate 210 is arranged inside the structure is preferable.

The linear polarizer 220 includes a polarization layer 221 for changing the polarization characteristics of light, first and second TAC films 223a formed on both sides of the polarization layer 221 to protect and support the polarization layer 221 ; 223b).

The linear polarizer 220 absorbs linearly polarized light parallel to the absorption axis of the polarization layer 221 and transmits linearly polarized light perpendicular to the absorption axis, that is, linearly polarized light parallel to the transmission axis.

The polarizing layer 221 may be formed of polyvinyl alcohol (PVA) that is stretched by dyeing iodine ions or dichroic dyes. Alternatively, the polarization layer 221 may be formed of a reactive mesogen (RM) and a dichroic dye. may include

In addition, the second retardation layer 215 and the first retardation layer 213 positioned above the linear polarizer 220 are sequentially positioned, the retardation plate 210 is positioned, and the second retardation layer 215 is A light absorber 211 having a main absorption wavelength band of 420 to 450 nm is included in a transparent resin, and the first retardation layer 213 has a flat wavelength dispersion characteristic.

Here, the first retardation layer 213 having flat dispersion characteristics may be a half wave plate (HWP) that has a phase delay of λ/2 to change the polarization direction of incident light. Accordingly, the linearly polarized light passing through the retardation plate 210 is changed to the linearly polarized light rotated by 90 degrees.

For example, the first retardation layer 213 having flat dispersion characteristics may be formed by stretching a cyclo-olefin polymer or cyclic olefin polymer (COP) film.

And, the transparent resin of the second retardation layer 215 is a binder resin, for example, at least one resin selected from the group consisting of polyester-based, acrylic-based, polyurethane-based, melamine-based, polyvinyl alcohol-based and oxazoline-based binder resins. It may be made of, preferably, it may be made of an acrylic binder resin.

And, the light absorber 211 included in the second retardation layer 215 has a main absorption wavelength band of 420 to 450 nm, hydroxy benzotriazole (HB), tris-resorcinol-triazine chromo Pore (Tris-Resorcinol-Triazine chromophore, TRTC), hydroxyphenyl-benzotriazole chromophore (Hydroxylphenyl-benzotriazole chromophore, HBC) series may be made of one or a combination of two or more.

Here, the second retardation layer 215 may be formed by coating or coating on the first retardation layer 213 as the light absorber 211 is included in the transparent resin, so that the first retardation layer 213 is formed. A separate adhesive or adhesive is not required between the second retardation layer 215 and the second retardation layer 215 .

In addition, the positions of the first retardation layer 213 and the second retardation layer 215 can be freely designed between the linear polarizer 220 and the OLED display panel 110 .

The polarizing plate 200 according to the second embodiment of the present invention includes a first retardation layer 213 in which the retardation plate 210 has flat dispersion characteristics and a light absorber 211 having a main absorption wavelength band of 420 to 450 nm. As the second phase difference layer 215 is formed, it has reverse wavelength dispersion characteristics.

Through this, it is possible to improve the black color of the OLED 100 , thereby improving the contrast, and in particular, it is possible to implement deep black, thereby further improving the contrast.

In addition, since there is no need to use a retardation plate having an expensive reverse dispersion characteristic, the process cost can be reduced, and in order to implement the reverse dispersion characteristic, there is no need to laminate and use two or more retardation films having different retardation values. , process simplification and process cost can also be reduced.

In particular, it is also possible to prevent the problem that the optical properties are lowered by using the two retardation films.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

100: OLED, 101: substrate, 102: protective film
103: semiconductor layer (103a: active region, 103b, 103c: source and drain regions)
104: gate insulating film, 105: gate electrode
106a, 106b: source and drain electrodes
107: wavelength conversion layer, 108: overcoat layer, 109a, 109b: first and second interlayer insulating films
110: OLED display panel
111: first electrode, 113: organic light emitting layer, 115: second electrode
119: bank, 120: protective film
200: polarizing plate (210: retardation plate (211: light absorber), 220: linear polarizing plate (221: polarizing layer, 223a, 223b: first and second TAC films))
230a, 230b: first and second adhesive layers
240: surface treatment layer
DTr: driving thin film transistor, E: light emitting diode

Claims (10)

a display panel including a first electrode, an organic light emitting layer, and a second electrode;
a linear polarizing plate positioned above the display panel and transmitting only linearly polarized light in a predetermined direction;
The retardation plate is positioned between the display panel and the linear polarizer, has flat dispersion characteristics, and includes a light absorber having a main absorption wavelength band of 420 to 450 nm.
An organic light emitting display device comprising a.
The method of claim 1,
The retardation plate includes a first retardation layer having flat dispersion characteristics and a second retardation layer including a light absorber having a main absorption wavelength band of 420 to 450 nm.
3. The method of claim 2,
The second retardation layer is an organic light emitting display device including the light absorber in a transparent resin.
The method of claim 1,
The retardation plate is an organic light emitting display device formed by stretching a cyclo-olefin polymer or cyclic olefin polymer (COP) film.
The method of claim 1,
The light absorbing agent is hydroxy benzotriazole (HB), tris-resorcinol-triazine chromophore (Tris-Resorcinol-Triazine chromophore, TRTC), hydroxyphenyl-benzotriazole chromophore (Hydroxylphenyl) An organic light emitting display device comprising at least one selected from -benzotriazole chromophore, HBC) series.
4. The method of claim 3,
The transparent resin comprises at least one selected from the group consisting of polyester-based, acrylic-based, polyurethane-based, melamine-based, polyvinyl alcohol-based and oxazoline-based binder resins.
The method of claim 1,
The linear polarizing plate includes a polarizing layer and first and second TAC films positioned on both sides of the polarizing layer, and a surface treatment layer is provided outside the linear polarizing plate.
The method of claim 1,
An organic light emitting display device in which an adhesive is interposed between the linear polarizing plate and the retardation plate and between the retardation plate and the display panel. The method of claim 1,
The retardation plate consists of one retardation film, one side of the retardation film is attached to the light emitting surface of the display panel through a first adhesive layer, and the other surface of the retardation film is attached to the linear polarizer through a second adhesive layer.
organic light emitting display device.
3. The method of claim 2,
The second retardation layer is formed in a form coated on one surface of the first retardation layer without an adhesive or an adhesive
organic light emitting display device.

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