WO2018139875A1 - Optical filter for anti-reflection and organic light-emitting device - Google Patents

Abstract

The present application relates to an optical filter and an organic light-emitting device. The optical filter for anti-reflection sequentially comprises: a first phase difference film having an in-plane optical axis and having 1/4 wavelength phase delay properties; a second phase difference film having an optical axis fixedly inclined along the thickness direction; and a polarizer having an absorption axis formed in one direction. Therefore, the optical filer of the present application can improve visibility by being applied in the organic light-emitting device.

Description

Anti-reflective optical filter and organic light emitting device

The present application relates to an antireflection optical filter and an organic light emitting device.

This application claims the benefit of priority based on Korean Patent Application No. 10-2017-0011940 dated January 25, 2017 and Korean Patent Application No. 10-2018-0009386 dated January 25, 2018. All content disclosed in the literature is included as part of this specification.

Recently, there is a demand for weight reduction and thickness reduction of a monitor or a television, and according to such a demand, an organic light emitting device (OLED) has attracted attention. The organic light emitting device is a self-luminous display device that emits light by itself and thus does not require a separate backlight, thereby reducing thickness and advantageously implementing a flexible display device.

On the other hand, the organic light emitting device may reflect external light by the metal electrode and the metal wiring formed on the organic light emitting display panel, and the visibility and the contrast ratio may be deteriorated by the reflected external light, resulting in poor display quality. As in Patent Document 1 (Korean Patent Publication No. 2009-0122138), a circularly polarizing plate may be attached to one surface of an organic light emitting display panel to reduce the leakage of the reflected external light to the outside.

However, the currently developed circular polarizer has a strong viewing angle dependency, and thus has a problem in that visibility is reduced due to a decrease in antireflection performance toward the side.

SUMMARY OF THE INVENTION The problem to be solved by the present application is to provide an optical filter having excellent omnidirectional antireflection performance in front as well as side and an organic light emitting device having improved visibility by applying the optical filter.

The present application relates to an antireflection optical filter. 1 exemplarily shows the optical filter. As shown in FIG. 1, the optical filter may sequentially include a first retardation film 10, a second retardation film 20, and a polarizer 30. The first retardation film may have an in-plane optical axis and may have a quarter-wave retardation characteristic. The second retardation film may have an optical axis that is inclined constantly along the thickness direction. The second retardation film having such a property may be referred to as a constant tilt film. The polarizer may have an absorption axis formed in one direction.

In the present specification, the polarizer means an element that exhibits selective transmission and absorption characteristics with respect to incident light. The polarizer may transmit, for example, light oscillating in one direction from incident light oscillating in various directions, and absorb light oscillating in the other direction.

The polarizer included in the optical filter may be a linear polarizer. In the present specification, the linearly polarized light refers to a case where linearly polarized light that selectively transmits light vibrates in one direction and linearly vibrates in a direction orthogonal to the vibration direction of the linearly polarized light.

Examples of the linear polarizer include a polarizer in which iodine is dyed in a polymer stretched film such as a PVA stretched film, or a liquid crystal polymerized in an oriented state as a host, and an anisotropic dye arranged according to the alignment of the liquid crystal as a guest. Guest-hosted polarizers may be used, but are not limited thereto.

According to the exemplary embodiment of the present application, a PVA stretched film may be used as the polarizer. The transmittance to polarization degree of the polarizer may be appropriately adjusted in consideration of the purpose of the present application. For example, the transmittance of the polarizer may be 42.5% to 55%, and the degree of polarization may be 65% to 99.9997%.

When defining angles in this specification, when using terms such as vertical, horizontal, orthogonal or parallel, this means substantially vertical, horizontal, orthogonal or parallel in the range that does not impair the desired effect, for example , Error including manufacturing error or variation. For example, each of the above cases may include an error within about ± 15 degrees, an error within about ± 10 degrees or an error within about ± 5 degrees.

In the present specification, the retardation film may mean an element capable of converting incident polarization by controlling birefringence as an optical “anisotropic” film. In the present specification, unless noted otherwise, the x-axis refers to a direction parallel to the in-plane slow axis of the retardation film, and the y-axis refers to a direction parallel to the in-plane fast axis of the retardation film. The z axis means the thickness direction of the retardation film. The x and y axes may be perpendicular to each other in plane. In the present specification, when the retardation film includes a rod-shaped liquid crystal molecule, the slow axis may mean a long axis direction of the rod shape, and when the retardation film includes a disc-shaped liquid crystal molecule, the slow axis may mean a normal direction of the disc shape. . While describing the optical axis of the retardation film herein, unless otherwise specified, the slow axis means. In the present specification, the refractive index of the retardation film is described, and unless otherwise specified, the refractive index with respect to light having a wavelength of about 550 nm.

In the present specification, the surface retardation (Rin) of the retardation film is calculated by the following Equation 1.

[Equation 1]

Rin = d × (nx-ny)

In Equation 1, Rin is the retardation of the plane, d is the thickness of the retardation film, nx and ny are the refractive index in the x-axis and y-axis directions defined above, respectively. In the present specification, the plane retardation of the retardation film is described, and unless otherwise specified, the planar retardation with respect to light having a wavelength of about 550 nm.

In the present specification, the reverse wavelength dispersion characteristic may mean a characteristic satisfying Equation 2 below, and a normal wavelength dispersion characteristic may mean a characteristic satisfying Equation 3 below, and the flat wavelength dispersion characteristic is flat wavelength dispersion) may mean a property satisfying the following Equation 4.

[Formula 2]

R (450) / R (550) <R (650) / R (550)

[Equation 3]

R (450) / R (550)> R (650) / R (550

[Equation 4]

R (450) / R (550) = R (650) / R (550)

In Equations 2 to 4, R (λ) is a plane retardation of the retardation film with respect to λnm light.

In the present specification, a retardation film satisfying the following formula 5 may be referred to as a so-called + A plate, and a retardation film satisfying the following formula 6 may be referred to as a + C plate.

[Equation 5]

nx> ny = nz

[Equation 6]

nx = ny <nz

In Equations 5 to 6, nx, ny, and nz are refractive indexes in the x-axis, y-axis, and nz directions, respectively, defined above.

The optical filter may sequentially include a first retardation film, a second retardation film, and a polarizer. If this arrangement order is satisfied, it may be advantageous to improve the omnidirectional antireflection performance on the side as well as the front side.

The first retardation film may have an in-plane optical axis. That is, the first retardation film may have an optical axis parallel to the plane direction. The optical axis of the first retardation film may be about 40 degrees to 50 degrees, about 43 degrees to 47 degrees, and specifically about 45 degrees with the absorption axis of the polarizer. When the optical axis of the first retardation film and the absorption axis of the polarizer form the above angular range, it may be advantageous to improve the omnidirectional antireflection performance on the side as well as the front side.

The first retardation film may have a quarter wavelength retardation characteristic. In the present specification, the "n wavelength phase delay characteristic" may mean a characteristic capable of retarding incident light by n times the wavelength of the incident light within at least part of a wavelength range. Therefore, the quarter wavelength phase delay characteristic may mean a characteristic that may phase-retard incident light by a quarter of a wavelength of the incident light within at least a portion of a wavelength range. The on-plane retardation of light of 550 nm wavelength of the first retardation film may be 120 nm to 160 nm. The planar phase difference may be specifically 120 nm or more, 130 nm or more, 135 nm or more, and may be 160 nm or less, 150 nm or less, or 140 nm or less.

The first retardation film may have reverse wavelength dispersion. For example, the first retardation film may have a property that the in-plane retardation increases as the wavelength of the incident light increases. The incident light may be, for example, 300 nm to 800 nm.

In one example, the R (450) / R (550) value of the first retardation film may be 0.99 or less. In one example, the R (450) / R (550) value may be in the range of 0.6 to 0.99. The R (450) / R (550) value may be, for example, 0.6 or more, 0.65 or more, 0.7 or more, or 0.75 or more, 0.99 or less, 0.95 or less, 0.9 or less, 0.85 or less, or 0.8 or less. The value of R (650) / R (550) of the first retardation film may be 1.01 to 1.19, 1.05 to 1.15, or 1.09 to 1.11 while having a value greater than that of R (450) / R 550.

The first retardation film may be a uniaxial retardation film. For example, the first retardation film may be a + A plate satisfying Equation 5.

The first retardation film may be a polymer film. Examples of the polymer film include polyolefins such as PC (polycarbonate), norbornene resin (norbonene resin), PVA (poly (vinyl alcohol)), PS (polystyrene), PMMA (poly (methyl methacrylate)), PP (polypropylene), A film including Par (poly (arylate)), PA (polyamide), PET (poly (ethylene terephthalate)) or PS (polysulfone) may be used. The polymer film may be stretched or shrunk under appropriate conditions to impart birefringence to be used as the first retardation film.

The first retardation film may be a liquid crystal film. The liquid crystal film may include a state in which the liquid crystal molecules are aligned and polymerized. The liquid crystal molecules may be polymerizable liquid crystal molecules. In the present specification, the polymerizable liquid crystal molecule may mean a molecule including a site capable of exhibiting liquid crystal, for example, a mesogen skeleton, and one or more polymerizable functional groups. In addition, including the polymerizable liquid crystal molecules in a polymerized form may mean a state in which the liquid crystal molecules are polymerized to form a skeleton such as a main chain or side chain of the liquid crystal polymer in the liquid crystal film. The liquid crystal film may include, for example, the liquid crystal molecules in a horizontally routed state. In this specification, a "horizontal orientation" can mean the state in which the slow axis of the liquid crystal film containing liquid crystal molecules is oriented horizontally with respect to the plane of a liquid crystal film.

The second retardation film may have an optical axis that is inclined constantly along the thickness direction. As used herein, the inclination of the optical axis may mean that the optical axis is inclined at a predetermined angle with respect to the plane of the retardation film. In the present specification, the inclination angle may mean a minimum angle formed by the plane of the optical axis and the retardation film. In one example, when the second retardation film includes a rod-shaped liquid crystal molecule, the inclination angle may mean an angle formed by the long axis direction of the rod shape and the plane of the retardation film. In another example, when the second retardation film includes liquid crystal molecules having a disc shape, the inclination angle may mean an angle between the disc surface and the plane of the retardation film. The inclination angle may be, for example, greater than 0 degrees and less than 90 degrees, and as described below, the inclination angle range may be appropriately adjusted in consideration of antireflection performance.

The inclination direction of the optical axis of the second retardation film may be parallel to the absorption axis of the polarizer. As used herein, the inclination direction of the optical axis may refer to the projection of the optical axis to the plane of the second retardation film. When the inclination direction of the optical axis of the second retardation film and the absorption axis of the polarizer are parallel to each other, it may be advantageous to improve the omnidirectional antireflection performance on the side as well as the front side. The inclination direction of the optical axis of the second retardation film and the absorption axis of the polarizer may form an angle of 0 degrees or more, for example, less than 4 degrees, 3.5 degrees or less, 3 degrees or less, 2.5 degrees or less, 2 degrees or less, 1.5 degrees or less. It can achieve an angle of less than or equal to 1 degree or less than 0.5 degrees, preferably 0 degrees.

The thickness of the second retardation film may be, for example, 0.3 μm to 3 μm. Within the above thickness range, it is possible to provide an optical filter having excellent antireflection characteristics in all directions. The thickness of the second retardation film can be further improved in the above-mentioned range by being adjusted within the above range according to the structure of the optical filter described below.

The second retardation film may have a reverse wavelength dispersion characteristic. Specific details on the reverse wavelength dispersion characteristics may be equally applied to the contents of the first retardation film. In one example, the value of R (450) / R (550) of the second retardation film may be 0.77 to 0.99, preferably 0.82 to 0.95. When the second retardation film has a reverse wavelength dispersion characteristic, it is possible to obtain an effect of further improving the reflectance characteristic.

The second retardation film may include a liquid crystal layer. The liquid crystal layer may include liquid crystal molecules. The liquid crystal layer may include liquid crystal molecules having an absolute value of refractive index anisotropy of 0.01 to 0.25. In this specification, the refractive index anisotropy (Δn) may mean a value of an extraordinary refractive index (ne) minus an ordinary refractive index (no). In the present specification, the abnormal refractive index may mean a refractive index in the slow axis direction of the liquid crystal layer, and the normal refractive index may mean a refractive index in the fast axis direction of the liquid crystal layer. The refractive anisotropy may be, for example, 0.01 or more, 0.03 or more, 0.04 or more, or 0.05 or more, and 0.25 or less, 0.2 or less, 0.18 or less, 0.16 or less, 0.14 or less, or 0.12 or less. In one example, the refractive index anisotropy value may be positive when the liquid crystal layer includes rod-shaped liquid crystal molecules, and the refractive index anisotropy value may be negative when the liquid crystal layer includes disk-shaped liquid crystal molecules.

The liquid crystal layer may include rod-shaped liquid crystal molecules or disk-shaped liquid crystal molecules.

The rod-shaped liquid crystal molecules may include a compound in which a linear alkyl group, an alkoxy group, a substituted benzoyloxy group, or the like is substituted in the molecular structure, and has a rod-like structure and exhibits liquid crystallinity. As the rod-shaped liquid crystal molecules, a liquid crystal compound known to form a so-called nematic phase may be used. As used herein, the term "nematic phase" may refer to a liquid crystal phase arranged in order in the major axis direction, although there is no regularity with respect to the position of the liquid crystal molecules. In one example, the rod-like liquid crystal compound may have a crosslinkable or polymerizable functional group. The crosslinkable or polymerizable functional group is not particularly limited, but examples thereof include alkenyl groups, epoxy groups, cyano groups, carboxyl groups, acryloyl groups, methacryloyl groups, acryloyloxy groups, methacryloyloxy groups, and the like. Can be.

The disk-shaped liquid crystal molecule includes a compound having a molecular center as a parent nucleus, and a linear alkyl group, an alkoxy group, a substituted benzoyloxy group, etc. are radially substituted as the linear chain, and have a discotic structure, and include a compound showing liquid crystallinity. can do. As the disk-shaped liquid crystal molecules, a liquid crystal compound known to form a so-called discotic phase may be used. In general, the disc-shaped liquid crystal compound has negative refractive anisotropy (uniaxiality), and examples thereof include benzene derivatives described in C. Destrade et al., Mol. Crates. 71, page 111 (1981); Cyclohexane derivatives described in Angew. Chem. 96, page 70 (1984) by B. Kohne et al .; And azacrown or phenyl as described in J. Chem. Commun., JMLehn et al., Page 1794 (1985), J. Am. Chem. Soc. 116, page 2655 (1994). And acetylene macrocycles. In one example, the discotic liquid crystal compound may have a crosslinkable or polymerizable functional group. The crosslinkable or polymerizable functional group is not particularly limited, but examples thereof include alkenyl groups, epoxy groups, cyano groups, carboxyl groups, acryloyl groups, methacryloyl groups, acryloyloxy groups, methacryloyloxy groups, and the like. Can be.

The liquid crystal layer may include the liquid crystal molecules in a tilted alignment state. In this specification, the inclination orientation may mean an alignment state in which the liquid crystal molecules are inclined at an angle with respect to the plane of the liquid crystal layer, and may specifically refer to a state in which the liquid crystal molecules are not vertically or horizontally aligned. Specifically, the inclination orientation may mean an alignment state in which the inclination angles of all liquid crystal molecules in the liquid crystal layer are ± 5 degrees or less, ± 3 degrees or less, or ± 1 degrees or less, and preferably the inclination angles of all liquid crystal molecules are the same. . Specifically, the inclination orientation may refer to an alignment state in which the graph shown in which the thickness of the liquid crystal layer is the x axis and the local tilt angle corresponding to the thickness is the y axis is a graph in which the slope is adjacent to zero. Can be.

The inclination angle of the optical axis of the second retardation film may be, for example, 10 degrees to 65 degrees. Within the inclination angle range, it is possible to provide an optical filter excellent in antireflection characteristics in all directions. The inclination angle of the optical axis of the second retardation film can be further improved within the above range according to the structure of the optical filter described below, thereby further improving the anti-directional reflection characteristic.

2 exemplarily shows an optical filter including the second retardation film 20 including the rod-shaped liquid crystal molecules R. As shown in FIG. FIG. 3 exemplarily shows an optical filter including the second retardation film 30 including the disc-shaped liquid crystal molecules (D).

The tilt alignment of the liquid crystal molecules may be performed by a tilt alignment method of liquid crystals known in the art. For example, gradient alignment may be induced by coating liquid crystal molecules on a photo alignment layer formed by obliquely irradiating ultraviolet rays or by applying a magnetic field to the liquid crystal layer.

The optical filter of the present application may effectively improve the anti-reflection performance from the front as well as the side by adjusting the optical properties of the second retardation film.

In one example, the second retardation film may include rod-shaped liquid crystal molecules. In this case, the inclination angle of the optical axis of the second retardation film may be 25 degrees to 65 degrees. The inclination angle may be, for example, 25 degrees or more, 30 degrees or more, or 35 degrees or more, and 65 degrees or less, 60 degrees or less, 55 degrees or less, or 50 degrees or less. In this case, the thickness of the second retardation film may be 0.35㎛ to 2.2㎛. The thickness may be specifically 0.35 μm or more or 0.4 μm or more, and may be 2.2 μm or less, 2.0 μm or less, or 1.8 μm or less. When the second retardation film is applied, the optical filter may exhibit excellent antireflection performance with a reflectance of about 1% or less at the front.

When the second retardation film includes rod-shaped liquid crystal molecules, the inclination angle of the optical axis of the second retardation film may be 35 degrees to 50 degrees. In this case, the thickness of the second retardation film may be 0.4 μm to 2.2 μm. When the second retardation film is applied, the optical filter may exhibit excellent anti-reflection performance with a reflectance of less than about 1%, 0.8% or less, 0.6% or less, 0.5% or less, or 0.4% or less in terms of 60 degrees.

When the second retardation film includes rod-shaped liquid crystal molecules, the thickness of the second retardation film may be adjusted to effectively improve the anti-reflection performance in terms of 60 degrees according to the refractive index anisotropy of the liquid crystal molecules. In one example, when the refractive index anisotropy of the liquid crystal molecules is 0.04 to 0.06, the inclination angle of the optical axis of the second retardation film is 35 degrees to 50 degrees, if the thickness of the second retardation film is 1.8㎛ to 2.2㎛, 60 degrees In terms of performance, it can exhibit better anti-reflection performance. In another example, when the refractive index anisotropy of the liquid crystal molecules is 0.07 to 0.09, the inclination angle of the optical axis of the second retardation film is 35 degrees to 50 degrees, and when the thickness of the second retardation film is 1.15 μm to 1.3 μm, the 60 degree side The better anti-reflection performance can be seen at. In another example, when the refractive index anisotropy of the liquid crystal molecules is 0.1 to 0.14, the inclination angle of the optical axis of the second retardation film is 35 degrees to 50 degrees, and the thickness of the second retardation film is 0.8 μm to 0.9 μm, The better anti-reflection performance can be seen at. In another example, when the refractive index anisotropy of the liquid crystal molecules is 0.2 to 0.3, specifically, 0.24 to 0.26, the inclination angle of the optical axis of the second retardation film is 35 degrees to 50 degrees, and the thickness of the second retardation film is 0.35 μm to If the thickness is 0.45 μm, specifically 0.4 μm, a better anti-reflection performance may be exhibited in terms of 60 degrees. In one example, the second retardation film may include disc-shaped liquid crystal molecules. In this case, the inclination angle of the optical axis of the second retardation film may be 10 degrees to 35 degrees. The inclination angle may be, for example, 10 degrees or more, 15 degrees or more, or 20 degrees or more, and 35 degrees or less or 30 degrees or less. In this case, the thickness of the second retardation film may be 1 μm to 3 μm. The thickness may be, for example, 1 μm or more, 1.25 μm or more, or 1.5 μm or more, and 3 μm or less. When the second retardation film is applied, the optical filter may exhibit excellent antireflection performance with a reflectance of about 1% or less at the front.

When the second retardation film includes disc-shaped liquid crystal molecules, the inclination angle of the optical axis of the second retardation film may be, for example, 20 degrees to 30 degrees. In this case, the thickness of the second retardation film may be 1.05㎛ to 2.95㎛. When the second retardation film is applied, the optical filter may exhibit better anti-reflection performance with a reflectance of less than about 1%, 0.8% or less, or 0.6% or less at a 60 degree side.

When the second retardation film includes disk-shaped liquid crystal molecules, the thickness of the second retardation film may be adjusted to effectively improve the antireflection performance in terms of 60 degrees according to the refractive index anisotropy of the liquid crystal molecules. In one example, when the refractive index anisotropy of the liquid crystal molecules is 0.07 to 0.09, the inclination angle of the optical axis of the second retardation film is 20 degrees to 30 degrees, if the thickness of the second retardation film is 2.2 ㎛ to 2.6 ㎛, 60 degrees In terms of performance, it can exhibit better anti-reflection performance. In another example, when the refractive index anisotropy of the liquid crystal molecules is 0.1 to 0.14, the inclination angle of the optical axis of the second retardation film is 20 degrees to 30 degrees, and when the thickness of the second retardation film is 1.5 μm to 1.85 μm, the side at 60 degrees The better anti-reflection performance can be seen at.

When the second retardation film includes rod-shaped liquid crystal molecules, the planar retardation of the second retardation film with respect to light having a wavelength of 550 nm may be 90 nm to 105 nm. When the second retardation film includes disc-shaped liquid crystal molecules, the planar retardation of the second retardation film with respect to light having a wavelength of 550 nm may be 160 nm to 250 nm.

As described above, the second retardation film may include a rod-shaped or disk-shaped liquid crystal molecule, and may improve antireflection performance not only from the front side but also from the side by appropriately adjusting the inclination angle, thickness, and the like. In one example, when the second retardation film includes rod-shaped liquid crystal molecules, the second retardation film may be more advantageous in terms of improving the omni-directional antireflection performance in comparison with the case of including the disc-shaped liquid crystal molecules.

The optical filter may further include a C plate. As shown in FIG. 4, the C plate 40 may be disposed outside the first retardation film 10, that is, on an opposite side on which the second retardation film is disposed.

The C plate may include a polymer material or a UV curable liquid crystal film. The usable film may include a homeotropic aligned liquid crystal film, a biaxial stretched polycarbonate, and the like.

The optical filter may further include a surface treatment layer. Examples of the surface treatment layer may include an antireflection layer and the like. The surface treatment layer may be disposed on the outer side of the polarizer, that is, on the opposite side on which the second retardation film is disposed. The antireflection layer may be a laminate of two or more layers having different refractive indices, but is not limited thereto.

The first retardation film, the second retardation film, and the polarizer of the optical filter may be attached to each other through an adhesive or an adhesive or may be laminated to each other by direct coating. An optically transparent adhesive or an adhesive can be used as the said adhesive or an adhesive agent.

The optical filter may have excellent omnidirectional antireflection performance at the side as well as at the front. For example, the optical filter may have a reflectance of about 1% or less, measured from the front. For example, the optical filter may have a reflectance of less than 1%, 0.8% or less, 0.6% or less, 0.5% or less, or 0.4% or less, measured from a 60 degree side with respect to the front surface. The reflectance may be a reflectance of light of any wavelength in the visible region, for example, a reflectance of light of any wavelength in the range of 380 nm to 780 nm, or a reflectance of light belonging to the entire visible region. The reflectance may be, for example, a reflectance measured at the polarizer side of the optical filter. The reflectance in the 60 degree side means the minimum reflectance among the reflectances measured in the full orientation of 0 degree to 360 degrees in the 60 degree side, or means all the reflectances measured in the full orientation of 0 degrees to 360 degrees, or 0 degrees to 360 degrees. The average reflectance of the reflectance measured in all directions can be referred to. The optical filter of the present application can prevent reflection of external light, thereby improving visibility of the organic light emitting device. Incident unpolarized light (hereinafter referred to as “external light”) incident from the outside passes through the polarizer and transmits only one of the two polarization orthogonal components, that is, the first polarization orthogonal component, and is polarized. The light may be converted into circularly polarized light while passing through the first retardation film. The circularly polarized light is reflected from the display panel of the organic light emitting diode display including the substrate, the electrode, and the like, and the rotation direction of the circularly polarized light is changed, and the circularly polarized light passes through the first retardation film again, and thus, among the two polarized orthogonal components. Is converted into another polarization orthogonal component, that is, a second polarization orthogonal component. Since the second polarized orthogonal component does not pass through the polarizer and no light is emitted to the outside, the second polarized orthogonal component may have an external light reflection preventing effect.

Since the optical filter of the present application can effectively prevent reflection of external light incident from the side, the side visibility of the organic light emitting device can be improved. For example, it is possible to effectively prevent reflection of external light incident from the side through the viewing angle polarization compensation principle.

The optical filter of the present application can be applied to organic bales and devices. 5 is a cross-sectional view illustrating the organic light emitting device by way of example. Referring to FIG. 5, the organic light emitting device includes an organic light emitting display panel 200 and an optical filter 100 disposed on one surface of the organic light emitting display panel 200. The first retardation film 30 of the optical filter may be disposed adjacent to the organic light emitting display panel 200 as compared to the polarizer 10.

The organic light emitting display panel may include a base substrate, a lower electrode, an organic emission layer, an upper electrode, and an encapsulation substrate. One of the lower electrode and the upper electrode may be an anode and the other may be a cathode. The anode may be made of a conductive material having a high work function as an electrode into which holes are injected, and the cathode may be made of a conductive material having a low work function as an electrode into which electrons are injected. At least one of the lower electrode and the upper electrode may be made of a transparent conductive material through which emitted light can come out, and may be, for example, ITO or IZO. The organic light emitting layer may include an organic material that emits light when a voltage is applied to the lower electrode and the upper electrode.

An auxiliary layer may be further included between the lower electrode and the organic light emitting layer and between the upper electrode and the organic light emitting layer. The auxiliary layer may include a hole transporting layer, a hole injecting layer, an electron injecting layer, and an electron transporting layer to balance electrons and holes. However, it is not limited thereto. The encapsulation substrate may be made of glass, metal, and / or polymer, and may encapsulate the lower electrode, the organic emission layer, and the upper electrode to prevent the inflow of moisture and / or oxygen from the outside.

The optical filter 100 may be disposed on a side from which light is emitted from the organic light emitting display panel. For example, in the case of a bottom emission structure in which light is emitted toward the base substrate, the bottom emission structure may be disposed outside the base substrate. In the case of a top emission structure in which light is emitted to the encapsulation substrate side, the bottom emission structure may be disposed outside of the encapsulation substrate. Can be. The optical filter 100 may improve display characteristics of the organic light emitting device by preventing external light from being reflected outside the organic light emitting device by being reflected by a reflective layer made of metal such as electrodes and wirings of the organic light emitting display panel 200. . In addition, since the optical filter 100 may exhibit an anti-reflection effect not only in the front but also in the side as described above, the side visibility may be improved.

The optical filter of the present application is excellent in the omnidirectional antireflection performance from the front as well as the side, the optical filter can be applied to the organic light emitting device to improve the visibility.

1 is an exemplary cross-sectional view of an optical filter according to an embodiment of the present application.

2 is an exemplary cross-sectional view of an optical filter to which a rod-shaped liquid crystal molecule is applied.

3 is an exemplary cross-sectional view of an optical filter to which disk-shaped liquid crystal molecules are applied.

4 is an exemplary cross-sectional view of an optical filter applying a C-plate.

5 is a cross-sectional view of the organic foot and the device according to an embodiment of the present application.

6 is a simulation evaluation result of the optical filter of Comparative Example 1. FIG.

7 is a simulation evaluation result of the optical filter of Example 1. FIG.

8 is a simulation evaluation result of the optical filter of Example 2. FIG.

9 is a result of simulation evaluation 7.

Hereinafter, the above contents will be described in more detail with reference to Examples and Comparative Examples, but the scope of the present application is not limited by the contents given below.

Simulation Evaluation 1

For the simulation evaluation (Dimos software, AUTRONIC-MELCHERS Co., Ltd.), a structure in which reflectors, a first retardation film, a second retardation film, and polarizers having a reflectance of 50% in all the electric fields of visible light were sequentially arranged was set. The polarizer had an absorption axis in one direction, had a single transmittance (Ts) of 42.5%, and had a laminated structure of a triacyl cellulose (TAC) film having no phase difference. The second retardation film contained a rod-shaped liquid crystal molecule having a refractive index anisotropy (Δn) of 0.08 and was set to have an optical axis inclined constantly along the thickness direction (Constant Tilt Film). The projection to the plane of the optical axis of the second retardation film was set to be in parallel with the absorption axis of the polarizer (0 degrees). The first retardation film had an in-plane optical axis, and was set such that the Rin value was 137 nm and the R (450) / R (550) was 0.77 for light having a wavelength of 550 nm. The optical axis of the first retardation film was set to form 45 degrees with the absorption axis of the polarizer. Table 1 below shows the results of simulation evaluation of the thickness of the second retardation film having a front reflectance of 1% or less according to the inclination angle of the optical axis of the second retardation film. In addition, Table 1 below shows the results of simulation evaluation of the minimum reflectance and the thickness of the second retardation film in that case among the reflectances measured in all directions of 0 to 360 degrees from the 60 degree side with respect to the front side. The reflectance is the value measured at the polarizer side for the 550 nm wavelength.

Tilt angle of the optical axis of the second retardation film (°)	Thickness (μm) of the second retardation film having a front reflectance of 1% or less	60 degree side
		Minimum reflectance (%)	Thickness (㎛)
25	-	0.98	1.25
30	0.82 to 1.7	0.65	1.25
35	0.7 to 1.8	0.38	1.3
40	0.62 to 1.84	0.25	1.3
45	0.6 to 1.84	0.25	1.2
50	0.6 to 1.75	0.32	1.15
55	0.6 to 1.55	0.58	1.1
60	0.5 to 1.3	0.9	0.9
65	-	1.2	0.7

Simulation Evaluation 2

Simulation evaluation was performed in the same manner as in Simulation 1 except that the second retardation film was set to include rod-shaped liquid crystal molecules having refractive index anisotropy (Δn) of 0.12, and the results are shown in Table 2 below.

Tilt angle of the optical axis of the second retardation film (°)	Thickness (μm) of the second retardation film having a front reflectance of 1% or less	60 degree side
		Minimum reflectance (%)	Thickness (㎛)
25	-	One	0.8
30	0.58 to 1.1	0.67	0.85
35	0.52 to 1.2	0.38	0.85
40	0.42 to 1.23	0.25	0.9
45	0.4 to 1.23	0.25	0.87
50	0.4 to 1.2	0.33	0.8
55	0.4 to 1.04	0.6	0.8
60	0.45 to 0.75	0.91	0.6
65	-	1.2	0.5

Simulation Evaluation 3

Simulation evaluation was prepared in the same manner as in Simulation 1 except that the second retardation film was set to include rod-shaped liquid crystal molecules having refractive index anisotropy (Δn) of 0.05, 0.08, 0.12 and 0.25, respectively. Table 3 below shows the results of simulation evaluation of the minimum reflectance measured in the lateral direction of 60 degrees from the front and the thickness of the second retardation film in that case according to the inclination angle and the refractive index anisotropy of the optical axis of the second retardation film.

Tilt angle of the optical axis of the second retardation film (°)	Minimum reflectivity in terms of 60 degrees,% (thickness, μm)
	Δn = 0.05	Δn = 0.08	Δn = 0.12	Δn = 0.25
35	0.33 (2.1)	0.38 (1.3)	0.38 (0.85)	0.4 (0.4)
40	0.25 (2.2)	0.25 (1.3)	0.25 (0.9)	0.28 (0.4)
45	0.25 (1.95)	0.25 (1.2)	0.25 (0.87)	0.25 (0.4)
50	0.32 (1.8)	0.32 (1.15)	0.33 (0.8)	0.35 (0.4)

Simulation Evaluation 4

The simulation evaluation was performed in the same manner as in the simulation evaluation 1 except that the second retardation film was set to include disc-shaped liquid crystal molecules having refractive index anisotropy (Δn) of −0.08, and the results are shown in Table 4 below. .

Tilt angle of the optical axis of the second retardation film (°)	Thickness (μm) of the second retardation film having a front reflectance of 1% or less	60 degree side
		Minimum reflectance (%)	Thickness (㎛)
10	-	1.2	2.9
15	1.9 to 3.0	0.78	2.7
20	1.58 to 2.95	0.5	2.6
25	1.5 to 2.8	0.45	2.5
30	1.5 to 2.6	0.55	2.2
35	-	1.1	2.0

Simulation Evaluation 5

The simulation evaluation was performed in the same manner as in the simulation evaluation 1 except that the second retardation film was set to include disk-shaped liquid crystal molecules having refractive index anisotropy (Δn) of -0.12, and the results are shown in Table 5 below. .

Tilt angle of the optical axis of the second retardation film (°)	Thickness (μm) of the second retardation film having a reflectance of 1% or less from the front side	60 degree side
		Minimum reflectance (%)	Thickness (㎛)
10	-	1.15	2.15
15	1.37 to 2.12	0.8	2.95
20	1.12 to 2.05	0.55	1.85
25	1.05 to 1.93	0.5	1.7
30	1.22 to 1.72	0.55	1.5
35	-	1.1	1.3

Simulation Evaluation 6

For the simulation evaluation, the structure in which the polarizer, the first retardation film, and the reflecting plate were sequentially arranged was set as Comparative Example 1.

For simulation evaluation, a polarizer, a second retardation film (containing a rod-shaped liquid crystal molecule having a refractive index anisotropy of 0.12, a constant tilt film having a thickness of 0.9 μm and a tilt angle of 45 °), a first retardation film, and a reflecting plate are disposed in this order. The structure was set to Example 1. The polarizer of Example 1 has a structure in which a TAC film having no phase difference is laminated. For simulation evaluation, a polarizer, a second retardation film (containing a disc-shaped liquid crystal molecule having a refractive index anisotropy of -0.12 and a constant tilt film having a thickness of 1.2 μm and a tilt angle of 25 °), a first retardation film, and a reflecting plate are disposed in this order. The structure was set to Example 2. The polarizer of Example 2 has a structure in which a TAC film having a thickness direction retardation Rth of −30 nm is laminated.

Except as specifically mentioned above, it was set in the manner of simulation evaluation 1. For Comparative Examples 1, 1, and 2, the reflectance was measured at a 60-degree side with respect to the front face at 0 to 360 degrees of azimuth, and the results are shown in FIGS. 6 (Comparative Example 1) and FIG. 7 (Example 1). ) And FIG. 8 (Example 2). It can be seen from FIGS. 6 to 8 that Examples 1 and 2 have a lower total azimuth reflectance at a 60 degree side compared to Comparative Example 1. FIG.

Simulation Evaluation 7

For simulation evaluation, a polarizer, a second retardation film (a constant tilt film having a disc-shaped liquid crystal molecule having a refractive index anisotropy of −0.01, having a thickness of 2.1 μm, and having an inclination angle of 30 °), a first retardation film, and a reflecting plate in that order Set up the deployed structure. As the reflecting plate, a reflecting plate having a reflectance of 100% in all the electric fields of visible light was used. Five samples were set so that the angle which the projection to the optical axis plane of a 2nd phase difference film makes with the absorption axis of a polarizer is 0 degree, 4 degree, 8 degree, 12 degree, and 16 degree, respectively.

Except as specifically mentioned above, it was set in the manner of simulation evaluation 1. For the five samples, the average reflectance was measured at a side of 60 degrees relative to the front side according to the azimuth 0 to 360 degrees, and the results are shown in Table 6 and FIG. 9. 60 degrees later than Samples 2 whose projection of the second retardation film onto the optical axis plane has an angle of 0 degrees formed by the absorption axis of the polarizer, compared with Samples 2 to 5 where the angles are 4 degrees, 8 degrees, 12 degrees and 16 degrees, respectively. It can be seen that the total azimuth reflectance is low.

Sample	Angle with absorption axis of polarizer (°)	Average reflectance (%)
One	0	0.5
2	4	4
3	8	9
4	12	15
5	16	22

[Description of the code]

10: first retardation film 20: second retardation film 30: polarizer

R: rod-shaped liquid crystal molecule D: disk-shaped liquid crystal molecule T: tilt angle

40: C plate 100: optical filter 200: organic light emitting display panel

Claims (16)

1. A first retardation film having an in-plane optical axis and having a quarter-wave retardation characteristic,

   A second retardation film having an optical axis inclined constantly along the thickness direction;

   An anti-reflection optical filter comprising a polarizer sequentially having an absorption axis formed in one direction.
2. The optical filter of claim 1, wherein an optical axis of the first retardation film forms an angle of 40 degrees to 50 degrees with an absorption axis of the polarizer.
3. The optical filter according to claim 1, wherein the projection of the second retardation film onto the plane of the optical axis is parallel to the absorption axis of the polarizer.
4. The optical filter of claim 1, wherein a plane retardation of light of a wavelength of 550 nm of the first retardation film is 120 nm to 160 nm.
5. The optical filter of claim 1, wherein the first retardation film satisfies Equation 2.

   [Formula 2]

   R (450) / R (550) <R (650) / R (550)

   In Equation 2, R (λ) is the plane retardation of the retardation film with respect to λnm light.
6. The optical filter of claim 1, wherein the second retardation film comprises a liquid crystal layer.
7. The optical filter of claim 6, wherein the liquid crystal layer comprises liquid crystal molecules having an absolute value of refractive index anisotropy of 0.01 to 0.25.
8. The optical filter of claim 6, wherein the liquid crystal layer comprises rod-shaped liquid crystal molecules.
9. The optical filter of claim 8, wherein the inclination angle of the optical axis of the second retardation film is 25 degrees to 65 degrees, and the thickness of the second retardation film is 0.35 μm to 2.2 μm.
10. The optical filter of claim 9, wherein an inclination angle of the optical axis of the second retardation film is 35 degrees to 50 degrees, and a thickness of the second retardation film is 0.4 μm to 2.2 μm.
11. The optical filter of claim 6, wherein the liquid crystal layer comprises disc-shaped liquid crystal molecules.
12. The optical filter of claim 11, wherein the inclination angle of the optical axis of the second retardation film is 10 degrees to 35 degrees, and the thickness of the second retardation film is 1 μm to 3 μm.
13. The optical filter of claim 1, further comprising a C plate on an outer side of the first retardation film.
14. The optical filter of claim 1, further comprising an antireflective layer on the outside of the polarizer.
15. An organic light emitting device comprising the optical filter of claim 1 and an organic light emitting display panel.
16. The organic light emitting device of claim 15, wherein the first retardation film of the optical filter is disposed adjacent to the organic light emitting display panel compared to the polarizer.

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