Patent Description:
<CIT> relates to a liquid crystal display device.

<CIT> relates to a light-emitting device.

<CIT> relates to an organic light-emitting display apparatus.

<CIT> relates to an elliptically polarizing plate.

<CIT> relates to a polarizing plate with built-in viewing angle compensation film.

It is to be understood that this background of the technology section is intended to provide useful background for understanding the technology and as such disclosed herein, the technology background section can include ideas, concepts or recognitions that were not part of what was known or appreciated by those skilled in the pertinent art prior to a corresponding effective filing date of subject matter disclosed herein.

One inventive aspect relates to a polarizer that can effectively prevent reflection of external light and a display device including the same.

According to an aspect of the invention, there is provided a polarizer as set out in claim <NUM>. Preferred features are set out in claims <NUM> to <NUM>.

The refractive index anisotropic layer can have a thickness in a range of about <NUM> micrometer (µm) to about <NUM>.

The refractive index anisotropic layer can have a thickness of "a" µm, and when Nx - Ny = "b", <NUM> < a x b < <NUM>.

The half-wave plate can include an alignment layer, and the refractive index anisotropic layer can be disposed on the alignment layer.

The quarter-wave plate can include a cyclic olefin polymer (COP).

The quarter-wave plate can be disposed on the linear polarizer, and the half-wave plate can be disposed on the quarter-wave plate.

The half-wave plate can be disposed on the linear polarizer, and the quarter-wave plate can be disposed on the half-wave plate.

Another aspect is a display device that includes: a display panel; and a polarizer disposed on the display panel, wherein the polarizer includes: a linear polarizer; and a phase retardation layer disposed on the linear polarizer and including a quarter-wave plate and a half-wave plate, the half-wave plate includes a refractive index anisotropic layer, the refractive index anisotropic layer has a refractive index Nx in a direction of an x axis, a refractive index Ny in a direction of a y axis, and a refractive index Nz in a direction of a z axis, and Nx = Nz > Ny.

The refractive index anisotropic includes a liquid crystal layer.

The liquid crystal layer includes a discotic compound.

The discotic compound has a disc surface, and the disc surface has an inclination angle in a range of about <NUM> degrees to about <NUM> degrees with respect to a surface of the half-wave plate.

Nx and Nz can be in a range of about <NUM> to about <NUM>.

Ny can be in a range of about <NUM> to about <NUM>.

A difference between Nx and Ny can be in a range of about <NUM> to about <NUM>.

The refractive index anisotropic layer can have a thickness in a range of about <NUM> to about <NUM>.

The half-wave plate can further include an alignment layer, and the refractive index anisotropic layer is disposed on the alignment layer.

The quarter-wave plate can include a COP.

The display panel can include: a first substrate; a first electrode disposed on the first substrate; an organic light emitting layer disposed on the first electrode; and a second electrode disposed on the organic light emitting layer.

The display device can further include: a second substrate disposed on the second electrode, wherein the polarizer is disposed on the second substrate.

The display device can further include: a thin film encapsulation layer disposed on the second electrode, wherein the polarizer is disposed on the thin film encapsulation layer.

Another aspect is a polarizer, comprising: a linear polarizer; and a phase retardation layer on the linear polarizer and comprising a quarter-wave plate and a half-wave plate, wherein the half-wave plate comprises a refractive index anisotropic layer, wherein the refractive index anisotropic layer has a refractive index Nx defined in a direction of an x axis, a refractive index Ny defined in a direction of a y axis, and a refractive index Nz defined in a direction of a z axis, and wherein Nx = Nz > Ny.

In the above polarizer, the refractive index anisotropic layer comprises a liquid crystal layer. In the above polarizer, the liquid crystal layer comprises a discotic compound. In the above polarizer, the discotic compound has a disc surface, and wherein the disc surface has an inclination angle in the range of about <NUM> degrees to about <NUM> degrees with respect to a surface of the half-wave plate. In the above polarizer, each of Nx and Nz is in the range of about <NUM> to about <NUM>. In the above polarizer, Ny is in the range of about <NUM> to about <NUM>. In the above polarizer, the difference between Nx and Ny is in the range of about <NUM> to about <NUM>. In the above polarizer, the refractive index anisotropic layer has a thickness in the range of about <NUM> micrometer (µm) to about <NUM>.

In the above polarizer, the refractive index anisotropic layer has a thickness of "a" µm, and wherein "b" = Nx - Ny, where <NUM> < a x b < <NUM>. In the above polarizer, the half-wave plate comprises an alignment layer, and wherein the refractive index anisotropic layer is on the alignment layer. In the above polarizer, the quarter-wave plate comprises a cyclic olefin polymer (COP). In the above polarizer, the quarter-wave plate is on the linear polarizer, and wherein the half-wave plate is on the quarter-wave plate. In the above polarizer, the half-wave plate is on the linear polarizer, and wherein the quarter-wave plate is on the half-wave plate.

Another aspect is a display device, comprising: a display panel; and a polarizer on the display panel, wherein the polarizer comprises: a linear polarizer; and a phase retardation layer on the linear polarizer and comprising a quarter-wave plate and a half-wave plate, wherein the half-wave plate comprises a refractive index anisotropic layer, wherein the refractive index anisotropic layer has a refractive index Nx defined in a direction of an x axis, a refractive index Ny defined in a direction of a y axis, and a refractive index Nz defined in a direction of a z axis, and wherein Nx = Nz > Ny.

In the above display device, the refractive index anisotropic layer comprises a liquid crystal layer. In the above display device, the liquid crystal layer comprises a discotic compound. In the above display device, the discotic compound has a disc surface, and wherein the disc surface has an inclination angle in the range of about <NUM> degrees to about <NUM> degrees with respect to a surface of the half-wave plate. In the above display device, each of Nx and Nz is in the range of about <NUM> to about <NUM>. In the above display device, Ny is in the range of about <NUM> to about <NUM>. In the above display device, the difference between Nx and Ny is in a range of about <NUM> to about <NUM>. In the above display device, refractive index anisotropic layer has a thickness in the range of about <NUM> micrometer (µm) to about <NUM>. In the above display device, the refractive index anisotropic layer has a thickness of "a" µm, and wherein Nx - Ny = "b", <NUM> < a x b < <NUM>.

In the above display device, the half-wave plate further comprises an alignment layer, and wherein the refractive index anisotropic layer is on the alignment layer. In the above display device, the quarter-wave plate comprises a cyclic olefin polymer (COP). In the above display device, the quarter-wave plate is on the linear polarizer, and wherein the half-wave plate is on the quarter-wave plate. In the above display device, the half-wave plate is on the linear polarizer, and wherein the quarter-wave plate is on the half-wave plate. In the above display device, the display panel comprises: a first substrate; a first electrode on the first substrate; an organic light emitting layer on the first electrode; and a second electrode on the organic light emitting layer. The above display device further comprises a second substrate on the second electrode, wherein the polarizer is on the second substrate. The above display device further comprises a thin film encapsulation layer on the second electrode, wherein the polarizer is on the thin film encapsulation layer.

Another aspect is a polarizer, comprising: a linear polarizer; and a quarter-wave plate on the linear polarizer; and a half-wave plate on the quarter-wave plate and comprising a refractive index anisotropic layer, wherein the refractive index anisotropic layer has a refractive index Nx defined in a direction of an x axis, a refractive index Ny defined in a direction of a y axis, and a refractive index Nz defined in a direction of a z axis, and wherein Nx = Nz > Ny.

In the above display device, each of the half-wave and quarter-wave plates is thinner than the linear polarizer.

According to an aspect of the invention, there is provided a display device as set out in claim <NUM>. Preferred features are set out in claim <NUM>.

Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they can be embodied in different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey exemplary implementations to those skilled in the art.

All terminologies used herein are merely used to describe exemplary embodiments and can be modified according to the relevant art and the intention of an applicant. Therefore, the terms used herein should be interpreted as having a meaning that is consistent with their meanings in the context of the present disclosure, and is not intended to limit the exemplary embodiments.

In the drawings, certain elements or shapes can be simplified or exaggerated to better illustrate the described technology, and other elements present in an actual product can also be omitted. Thus, the drawings are intended to facilitate the understanding of the described technology. Like reference numerals refer to like elements throughout the specification.

When a layer or element is referred to as being "on" another layer or element, the layer or element can be directly on the other layer or element, or one or more intervening layers or elements can be interposed therebetween. In this disclosure, the term "substantially" includes the meanings of completely, almost completely or to any significant degree under some applications and in accordance with those skilled in the art. The term "connected" can include an electrical connection.

Hereinafter, a first exemplary embodiment will be described with reference to <FIG>.

<FIG> is a cross-sectional view illustrating a polarizer <NUM> according to the first exemplary embodiment. <FIG> is an exploded perspective view of <FIG>.

The polarizer <NUM> according to the first exemplary embodiment can include a linear polarizer <NUM> and a phase retardation layer <NUM> formed on the linear polarizer <NUM>. The polarizer <NUM> can serve to prevent reflection of external light.

The linear polarizer <NUM> can serve to linearly polarize an external light incident on the polarizer <NUM>.

The linear polarizer <NUM> can use a film obtained by a dichroic dye being adsorbed onto and aligned in a polyvinyl alcohol (PVA) resin. Examples of the PVA resin can include a homopolymer of vinyl acetate or a copolymer of a monomer different from vinyl acetate.

The polarizer <NUM> can be prepared through a scheme including, for example, a process of uniaxially stretching a PVA resin film, a process of dyeing the PVA resin film with a dichroic dye such that the dichroic dye is adsorbed onto the PVA resin film, a process of treating the PVA resin film, onto which the dichroic dye is adsorbed, using a boron aqueous solution, and a washing process. However, the scheme of manufacturing the linear polarizer <NUM> according to the first exemplary embodiment is not limited thereto.

The dichroic dye can use, for example, iodine and another dichroic dye used in the pertinent art. In the case of using iodine as the dichroic dye, the linear polarizer <NUM> can be prepared through a process of dyeing the PVA resin film by immersing the PVA resin film in an aqueous solution containing iodine and potassium iodine.

Iodine can be arranged in a direction parallel to a direction in which the PVA resin film is stretched. A transmission axis A1 of the linear polarizer <NUM> can be determined based on the arrangement of iodine, and the transmission axis A1 of the linear polarizer <NUM> can be substantially parallel to the direction of the arrangement of iodine.

A thickness of the linear polarizer <NUM> can vary based on a product to which the linear polarizer <NUM> is to be applied. For example, the linear polarizer <NUM> has a thickness in the range of about <NUM> micrometers (µm) to about <NUM>.

The phase retardation layer <NUM> can be formed on a surface of the linear polarizer <NUM>.

The phase retardation layer <NUM> can retard a phase of light. The phase retardation layer <NUM> can convert a linearly polarized light to a circularly polarized light, or can convert a circularly polarized light to a linearly polarized light. For example, an external light incident on the polarizer <NUM> is linearly polarized by the linear polarizer <NUM>, or circularly polarized by the phase retardation layer <NUM>. The circularly polarized external light can be reflected within a device to which the polarizer <NUM> is attached, for example, a display device, to thereby be converted to a reflected light. During the reflection process, a phase and a polarization axis of the light can vary. In some embodiments, the reflected light with the varied phase does not pass through the polarizer <NUM>, and thus, reflection of the external light can be prevented by the polarizer <NUM>.

The phase retardation layer <NUM> can use a phase difference plate having a film shape. For example, a single layer of the phase difference plate is used, or a plurality of layers of the phase difference plate are stacked to be used.

The phase retardation layer <NUM> according to the first exemplary embodiment can include a quarter-wave plate (QWP) <NUM> and a half-wave plate (HWP) <NUM>.

For example, the phase retardation layer <NUM> can include the QWP <NUM> formed on the linear polarizer <NUM> and the HWP <NUM> formed on the QWP <NUM>. However, the first exemplary embodiment is not limited thereto, and the HWP <NUM> can be formed on the linear polarizer <NUM> and the QWP <NUM> can be formed on the HWP <NUM>.

The QWP <NUM> can be prepared by stretching a film. For example, the QWP <NUM> is be prepared by stretching a film formed of polycarbonate (PC), polyvinyl alcohol (PVA), polystyrene (PS), poly(methyl methacrylate) (PMMA), polypropylene (PP), polyolefin, polyarylate (PAR), or polyamide (PA).

The QWP <NUM> can include a film formed of a cyclic olefin polymer (COP). The COP film can be prepared using, for example, a norbomene-based COP. The COP film can have high light transmittance, high thermal resistance, high strength, low moisture absorption, and high cost-efficiency. A phase difference plate formed of such a COP film can represent a relatively stable phase retardation value, irrespective of a wavelength of incident light.

In addition, the QWP <NUM> can be prepared using a photocurable liquid crystal compound. For example, an alignment layer is formed on a base film, and liquid crystal compounds is arranged on the alignment layer to be patterned thereon, such that the QWP <NUM> can be prepared. In this instance, based on the alignment layer and the arrangement of the liquid crystal compounds, the type of the phase difference plate to be prepared, that is, whether the quarter-wave plate or the half-wave plate, can be determined.

The type or the manufacturing scheme of the QWP <NUM> is not limited to the above description in embodiments of the invention.

The QWP <NUM> can have a transmission axis A2. The transmission axis A2 of the QWP <NUM> can be determined by a stretching axis of a film or a direction in which the liquid crystal compounds are aligned.

The QWP <NUM> according to the first exemplary embodiment can be prepared by stretching the COP film, and the transmission axis A2 of the QWP <NUM> can be substantially parallel to a stretching axis of the COP film.

The QWP <NUM> according to the first exemplary embodiment can be designed to be optimized for preventing reflection of an external light incident frontwards, that is, an external light vertically incident on a surface of the polarizer <NUM>. Accordingly, in a case of a polarizer using only the QWP <NUM> as the phase retardation layer <NUM>, reflection of an external light incident on the polarizer at a predetermined incident angle is not effectively prevented by the polarizer. In other words, in the case of using only the QWP <NUM> as the phase retardation layer <NUM>, a path of an external light can vary based on an incident angle of the external light such that a phase retardation effect can change, and the effect of preventing reflection of the external light can also change based on the incident angle.

In this case, when the incident angle of the external light increases, reflectivity of the polarizer can increase, and when a viewing angle of a user increases, an amount of reflected light to be visible to the user can increase.

In order to prevent the increase in reflectivity of the polarizer in response to the increase in the incident angle of the external light, the HWP <NUM> can be used along with the QWP <NUM>.

The HWP <NUM> according to the first exemplary embodiment can have a refractive index anisotropic layer.

The refractive index anisotropic layer can have a refractive index Nx in a direction of an x axis, a refractive index Ny in a direction of a y axis, and a refractive index Nz in a direction of a z axis, and a relationship thereamong in which "Nx = Nz > Ny" can be satisfied. A phase difference plate satisfying the relationship in which "Nx = Nz > Ny" can be referred to as a negative A-plate.

<FIG> is a structural view illustrating the HWP <NUM>. The HWP <NUM> of <FIG> can include a liquid crystal layer <NUM> as the refractive index anisotropic layer.

In detail, the HWP <NUM> according to the first exemplary embodiment can include a support member <NUM> and the liquid crystal layer <NUM> formed on the support member <NUM>. The liquid crystal layer <NUM> can have a refractive index anisotropy.

The support member <NUM> can serve to support the liquid crystal layer <NUM>. The support member <NUM> can be formed of a transparent plastic film and can include, for example, one or more of the following materials: tri-acetyl cellulose (TAC), polyethylene terephthalate (PET), polyimide (PI), and polycarbonate (PC).

In addition, an alignment layer can be used as the support member <NUM>. A description pertaining to the alignment layer will be provided further below.

The liquid crystal layer <NUM> includes a discotic compound <NUM>. For example, the liquid crystal layer <NUM> can include a binder compound, and the discotic compounds <NUM> can be arranged through being dispersed in the binder compound. The liquid crystal layer <NUM> including the discotic compound <NUM> can also be referred to as a discotic liquid crystal layer.

The discotic compound <NUM> of <FIG> has a predetermined inclination angle θ1 with respect to a surface of the HWP <NUM>. In detail, the discotic compound <NUM> of <FIG> can have a disc surface DS, and the disc surface DS has an inclination angle θ1 in the range of about <NUM> degrees to about <NUM> degrees with respect to a surface RS of the support member <NUM>.

In general, the inclination angle θ1 of the discotic compound <NUM> can vary based on the type of the discotic compound <NUM>, the alignment scheme of the discotic compound <NUM>, the type of material used in the alignment of the discotic compound <NUM>, and the type of alignment layer.

The liquid crystal layer <NUM> can be prepared by aligning the discotic compound <NUM> using the alignment layer and fixing the discotic compound <NUM> in the aligned state.

A discotic compound known to those skilled in the art can be used to form the liquid crystal layer <NUM>, and a polymerization scheme known to those skilled in the art can be used to fix the discotic compound <NUM>.

For example, to fix the discotic compound <NUM> by polymerization, a compound having a polymerizable group is used. Examples of the compound having the polymerizable group include a monomer or an oligomer. In this instance, a linking group can be introduced between the discotic compound <NUM> and the polymerizable group. For example, the liquid crystal layer <NUM> can include a compound expressed by Formula <NUM>.

In Formula <NUM>, "D" denotes the discotic compound <NUM>, "L" denotes the linking group, and "P" denotes the polymerizable group. "n" denotes an integer in the range of <NUM> to <NUM>.

The liquid crystal layer <NUM> can be prepared by coating, drying, and heating a composition for forming a liquid crystal layer including the discotic compound <NUM> up to a temperature at which a discotic nematic phase is formed, on the alignment layer and then polymerizing and cooling the composition for forming the liquid crystal layer. The temperature for forming the discotic nematic phase can be in the range of about <NUM> degrees Celsius (°C) to about <NUM>, which is lower than a thermal deformation temperature of the alignment layer, and more particularly, in the range of about <NUM> to about <NUM>.

The composition for forming the liquid crystal layer can include the discotic compound <NUM> in an amount of about <NUM> percentage by weight (wt%) to about 70wt% with respect to a total weight of the composition for forming the liquid crystal layer.

In addition, the composition for forming the liquid crystal layer can further include a polymerizable monomer, a polymerization initiator, and an additive, in addition to the discotic compound <NUM>.

The polymerizable monomer can use a monomer having a vinyl group, a vinyloxy group, an acryl group, and a methacryl group. The composition for forming the liquid crystal layer can include the polymerizable monomer in an amount of about 1wt% to about 50wt% with respect to the total weight of the composition for forming the liquid crystal layer.

The additive can use a polymer, a plasticizer, and a surfactant.

The polymer can use a polymer which is highly compatible with the discotic compound <NUM>. An example of such a polymer includes a cellulose ester polymer. Examples of the cellulose ester polymer include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose, cellulose acetate butyrate, and the like. The composition for forming the liquid crystal layer can include the polymer in an amount of about 1wt% to about 30wt% with respect to the total weight of the composition for forming the liquid crystal layer.

The plasticizer and the surfactant can use any plasticizer and surfactant commonly used in manufacturing a polymerizable composition.

The polymerization initiator can use a photopolymerization initiator and a thermal polymerization initiator.

The polymerization scheme of the composition for forming the liquid crystal layer can include a thermal polymerization scheme using a thermal polymerization initiator and a photopolymerization scheme using a photopolymerization initiator. In particular, in order to maintain the aligned state of the discotic compound <NUM> and polymerize the composition for forming the liquid crystal layer, the photopolymerization scheme can be used.

For the photopolymerization, the composition for forming the liquid crystal layer can include a photopolymerization initiator. Examples of the photopolymerization initiator include one or more of the following materials: an α-carbonyl compound, acyloin ether, an α-hydrocarbon-substituted aromatic acyloin compound, a polynuclear quinone compound, a combination of triarylimidazole dimer and p-aminophenylketone, an acridine compound, a phenazine compound, and an oxadiazole compound. The composition for forming the liquid crystal layer can include the photopolymerization initiator in an amount of about <NUM>. 01wt% to about 20wt% with respect to the total weight of the composition for forming the liquid crystal layer.

For the photopolymerization of the composition for forming the liquid crystal layer, light can be irradiated on the composition for forming the liquid crystal layer. Such light to be irradiated thereon can use ultraviolet (UV) light having energy in the range of about <NUM> millijoules per square centimeter (mJ/cm2) to about 5000mJ/cm2. The light irradiation can be conducted during the heating process in order to accelerate the photopolymerization reaction.

The composition for forming the liquid crystal layer can be cured to thereby form the liquid crystal layer <NUM> and to fix the discotic compound <NUM>.

As such, as the discotic compounds <NUM> are arranged at an inclination angle θ1 in the range of about <NUM> degrees to about <NUM> degrees, the liquid crystal layer <NUM> can have the refractive index Nx in the direction of the x axis and the refractive index Nz in the direction of the z axis in the range of about <NUM> to about <NUM>, and the refractive index Ny in the direction of the y axis in the range of about <NUM> to about <NUM>. In addition, a difference between Nx and Ny can have a value in the range of about <NUM> to about <NUM>.

However, the first exemplary embodiment is not limited thereto, and the refractive index Nx in the direction of the x axis, the refractive index Ny in the direction of the y axis, and the refractive index Nz in the direction of the z axis can vary based on the materials forming the liquid crystal layer <NUM> and the arrangement of the materials.

A thickness of the liquid crystal layer <NUM> can be adjusted to allow phase retardation, which is required for circular polarization, to occur. The thickness of the liquid crystal layer <NUM> can vary based on a refractive index of the liquid crystal layer <NUM>. The liquid crystal layer <NUM> according to the first exemplary embodiment can have a thickness in the range of about <NUM> to about <NUM>.

In addition, in order to compensate for a phase retardation variation based on an incident angle of an external light, a thickness and a refractive index of the liquid crystal layer <NUM> can be adjusted to satisfy the following relationship. For example, when the liquid crystal layer <NUM> has a thickness of "a" µm and a difference between the refractive index Nx and the refractive index Ny is given by an equation in which "Nx - Ny = b", the thickness and the refractive index of the liquid crystal layer <NUM> is adjusted so as to satisfy the relationship in which "<NUM> ≤ a x b ≤ <NUM>".

In a case in which a value calculated by "a x b" is in the range of about <NUM> to about <NUM>, a phase retardation variation in the range of about <NUM> nanometers (nm) to about <NUM> can be compensated. For example, even in the case in which a laterally incident external light has the phase retardation variation in the range of about <NUM> to about <NUM>, as compared to an external light incident frontwards, the laterally incident external light can be circularly polarized by the polarizer <NUM>.

More particularly, the value calculated by "a x b" can be in the range of about <NUM> to about <NUM>. In this case, the phase retardation variation can be compensated in the range of about <NUM> to about <NUM>.

In the case of using the liquid crystal layer <NUM> as the refractive index anisotropic layer of the HWP <NUM>, circular polarization of the external light can occur by the polarizer <NUM> despite varying incident angles of the external light. Accordingly, the polarizer <NUM> including the HWP <NUM> can effectively prevent reflection of the external light, irrespective of the incident angle of the external light.

The HWP <NUM> according to the first exemplary embodiment can include an alignment layer, and the alignment layer can function as the support member <NUM>. Accordingly, the liquid crystal layer <NUM> can be formed on the alignment layer.

The alignment layer can serve to determine an alignment direction of the discotic compound <NUM>.

The alignment layer can be prepared through a rubbing treatment of a polymer, a rhombic vacuum deposition process, a Langmuir-Brojet (LB) process, or the like. In this instance, the polymer for forming the alignment layer can include ω- tricosanoic acid, dioctadecylmethylammonium chloride, methyl stearic acid, and the like.

In detail, the alignment layer can be prepared through a rubbing treatment of a polymer. The polymer for forming the alignment layer can include PVA. In addition, a polymer which is modified through a hydrophobic group being bonded thereto can be used to form the alignment layer. For example, a polymer in which a hydrophobic group is introduced to PVA is used. Due to the affinity of the hydrophobic group with the discotic compound <NUM>, the hydrophobic group can be suitable for uniformly aligning the discotic compound <NUM>.

The hydrophobic group can be bonded to an end of a backbone of PVA or a side chain of PVA.

The hydrophobic group can include an aliphatic group having <NUM> or more carbon atoms or an aromatic group. For example, an alkyl group or an alkenyl group having <NUM> or more carbon atoms is used as the hydrophobic group.

In a case of bonding the hydrophobic group to the end of the backbone of PVA, a linking group can be introduced between the hydrophobic group and the end of the backbone of PVA. Examples of the linking group can include -S-, -C(CN)R<NUM> -, -NR<NUM>-, and the like. As used herein, R<NUM> and R<NUM> each denote a hydrogen atom or an alkyl group having one to <NUM> carbon atoms.

To prepare the alignment layer, a commercially available PVA film can be used.

The rubbing treatment can be performed by rubbing a surface of a film for forming the alignment layer a few number of times in a predetermined direction. For the rubbing treatment, a cloth in which a fiber has a uniform length and thickness and is uniformly arranged can be used.

The alignment layer can have an alignment direction RD, and in a case of forming the alignment layer by the rubbing treatment, the alignment direction RD can be parallel to a direction of the rubbing treatment. The discotic compound <NUM> can be aligned based on the alignment direction RD of the alignment layer.

A transmission axis of the liquid crystal layer <NUM> can be determined based on the alignment direction of the discotic compound <NUM>. The transmission axis of the liquid crystal layer <NUM> can be a transmission axis of the HWP <NUM>.

The alignment layer is not necessarily required in the polarizer <NUM>, and can be omitted. For example, the alignment layer is omitted in the preparing process of the polarizer <NUM>, subsequently to using the alignment layer for aligning the discotic compound <NUM>. In this case, a transparent base film can be used as the support member <NUM> for supporting the discotic compound <NUM>, in lieu of the alignment layer.

Further, the support member <NUM> can be omitted. For example, the liquid crystal layer <NUM>, aligned by the alignment layer, is formed directly on the QWP <NUM>.

Although not illustrated, the polarizer <NUM> according to the first exemplary embodiment can further include an adhesive layer interposed between the linear polarizer <NUM> and the QWP <NUM> and an adhesive layer interposed between the QWP <NUM> and the HWP <NUM>.

In addition, the linear polarizer <NUM>, the QWP <NUM>, and the HWP <NUM> can be formed to intersect one another at a predetermined angle to achieve effective reflection of external light.

For example, the QWP <NUM> is formed to intersect the linear polarizer <NUM> at an angle of θ2 based on a transmission axis, and the HWP <NUM> is formed to intersect the linear polarizer <NUM> at an angle of θ3 based on the transmission axis. As used herein, θ2 is an angle between the transmission axis A1 of the linear polarizer <NUM> and the transmission axis A2 of the QWP <NUM>, and can be in a range of about <NUM> degrees to about <NUM> degrees. In addition, θ3 is an angle between the transmission axis A1 of the linear polarizer <NUM> and the alignment direction RD of the alignment layer, and can be in the range of about <NUM> degrees to about <NUM> degrees.

When the polarizer <NUM> is formed on the display device, and the like, the y axis can be a direction parallel to a direction in which the range of an incident angle of external light is relatively great when viewed from a user. For example, in a case of using the polarizer <NUM> in a display device having a greater horizontal length than a vertical width, the y axis can be a direction parallel to the horizontal length of the display device.

<FIG> are graphs illustrating results of experiments on reflectivity of a polarizer. <FIG> illustrates a result of a simulation experiment on reflectivity of a polarizer including a HWP in which a refractive index anisotropy is absent; and <FIG> illustrates a result of a simulation experiment on reflectivity of the polarizer <NUM> according to the first exemplary embodiment.

In detail, the HWP used in the experiment of <FIG> can have a refractive index in which "Nx = Ny = Nz = <NUM>", and a HWP used in the experiment of <FIG> can have a refractive index in which "Nx = Nz = <NUM>" and "Ny = <NUM>". A relatively dark portion of <FIG> indicates a portion in which reflection of external light is effectively prevented, and a relatively bright portion thereof indicates a portion in which relatively low efficiency in preventing reflection of external light is exhibited. As illustrated in <FIG>, the polarizer <NUM> according to the first exemplary embodiment can effectively prevent reflection of external light in all directions irrespective of an incident angle of external light and can be excellent in representing a black color.

As such, the polarizer <NUM> according to the first exemplary embodiment can have the HWP <NUM> having a negative A-plate property, and can prevent reflection of external light irrespective of an incident angle of external light. Accordingly, a product using the polarizer <NUM> according to the first exemplary embodiment can be excellent in representing a black color and can have an excellent contrast ratio.

Hereinafter, a second exemplary embodiment will be described with reference to <FIG>. A repeated description of the aforementioned component will be omitted herein for conciseness.

<FIG> is an exploded perspective view illustrating a polarizer <NUM> according to the second exemplary embodiment.

The polarizer <NUM> according to the second exemplary embodiment includes a linear polarizer <NUM>, a HWP <NUM> formed on the linear polarizer <NUM>, and a QWP <NUM> formed on the HWP <NUM>. A configuration of the HWP <NUM> and the QWP <NUM> according to the second exemplary embodiment can be the same as that of the first exemplary embodiment.

Hereinafter, a third exemplary embodiment will be described with reference to <FIG>.

<FIG> is a cross-sectional view illustrating a polarizer <NUM> according to the third exemplary embodiment.

The polarizer <NUM> according to the third exemplary embodiment can include a linear polarizer <NUM>, a QWP <NUM>, a HWP <NUM>, and a support layer <NUM> interposed between the linear polarizer <NUM> and the QWP <NUM>.

The support layer <NUM> can serve to support and protect the polarizer <NUM>. The support layer <NUM> can use, for example, a tri-acetyl cellulose (TAC) film. The TAC film can have excellent durability and mechanical strength.

In addition, the polarizer <NUM> according to the third exemplary embodiment can further include an adhesive layer <NUM> formed on the HWP <NUM>. The adhesive layer <NUM> can be formed of an adhesive resin.

Hereinafter, a fourth exemplary embodiment will be described with reference to <FIG> and <FIG>.

<FIG> is a plan view illustrating an OLED display <NUM> according to the fourth exemplary embodiment. <FIG> is a cross-sectional view taken along line I-I' of <FIG>.

As illustrated in <FIG> and <FIG>, the OLED display <NUM> according to the fourth exemplary embodiment can include a display panel <NUM> and a polarizer <NUM>.

The display panel <NUM> can include a first substrate <NUM>, a wiring unit <NUM>, an OLED <NUM>, and a second substrate <NUM>.

The first substrate <NUM> can use an insulating substrate formed of one or more of the following materials: glass, quartz, ceramic, and plastic. However, the fourth exemplary embodiment is not limited thereto, and the first substrate <NUM> can also use a metallic substrate formed of stainless steel, or the like.

A buffer layer <NUM> can be formed on the first substrate <NUM>. The buffer layer <NUM> can include one or more of various inorganic and organic layers. The buffer layer <NUM> can serve to reduce or effectively prevent the infiltration of impure elements such as moisture into the wiring unit <NUM> or the OLED <NUM> through the first substrate <NUM> and can also planarize a surface of the first substrate <NUM>. However, the buffer layer <NUM> is not necessarily required, and can be omitted.

The wiring unit <NUM> can be formed on the buffer layer <NUM>. The wiring unit <NUM> can include a switching thin film transistor (TFT) <NUM>, a driving TFT <NUM>, and a capacitor <NUM>, and can drive the OLED <NUM>. The OLED <NUM> can display an image by emitting light based on a driving signal transmitted from the wiring unit <NUM>.

<FIG> and <FIG> illustrate the OLED display <NUM> as an active matrix organic light emitting diode (AMOLED) display having a 2Tr-1Cap structure in which a single pixel includes two thin film transistors, for example, the switching TFT <NUM> and the driving TFT <NUM>, and a single capacitor, for example, the capacitor <NUM>. However, the fourth exemplary embodiment is not limited thereto. For example, the OLED display <NUM> according to the fourth exemplary embodiment can have various structures in which a single pixel includes three or more thin film transistors and two or more capacitors and an additional wiring can further be included. As used herein, the term "pixel" refers to a minimum unit for displaying an image, and the OLED display <NUM> can display an image through a plurality of pixels.

The switching TFT <NUM>, the driving TFT <NUM>, the capacitor <NUM>, and the OLED <NUM> can be included in each pixel. In addition, a gate line <NUM>, a data line <NUM> insulated from and intersecting the gate line <NUM>, and a common power line <NUM> can be formed in the wiring unit <NUM>. A single pixel can be defined by a boundary among the gate line <NUM>, the data line <NUM>, and the common power line <NUM>. However, the definition of the pixel is not limited thereto in embodiments of the invention. The pixel can be defined by a pixel defining layer (PDL) <NUM> or a black matrix.

The OLED <NUM> can include a first electrode <NUM>, an organic light emitting layer <NUM> formed on the first electrode <NUM>, and a second electrode <NUM> formed on the organic light emitting layer <NUM>. A hole and an electron from the first electrode <NUM> and the second electrode <NUM>, respectively, are injected into the organic light emitting layer <NUM> to be combined with one another to thereby form an exciton. The OLED <NUM> can emit light by energy generated when the exciton falls from an excited state to a ground state.

The capacitor <NUM> can include a pair of capacitor plates <NUM> and <NUM>, which are formed to have an insulating interlayer <NUM> therebetween. In this instance, the insulating interlayer <NUM> can be a dielectric material. Capacitance of the capacitor <NUM> can be determined by an amount of electric charges stored in the capacitor <NUM> and a level of a voltage between the capacitor plates <NUM> and <NUM>.

The switching TFT <NUM> can include a switching semiconductor layer <NUM>, a switching gate electrode <NUM>, a switching source electrode <NUM>, and a switching drain electrode <NUM>. The driving TFT <NUM> can include a driving semiconductor layer <NUM>, a driving gate electrode <NUM>, a driving source electrode <NUM>, and a driving drain electrode <NUM>. The switching semiconductor layer <NUM> can be insulated from the switching gate electrode <NUM> by a gate insulating layer <NUM>, and the driving semiconductor layer <NUM> can be insulated from the driving gate electrode <NUM> by the gate insulating layer <NUM>.

The switching TFT <NUM> can be used as a switching element that selects a pixel to perform light emission. The switching gate electrode <NUM> can be connected to the gate line <NUM>. The switching source electrode <NUM> can be connected to the data line <NUM>. The switching drain electrode <NUM> can be formed to be spaced apart from the switching source electrode <NUM> and can be connected to one of the capacitor plates, for example, the capacitor plate <NUM>.

The driving TFT <NUM> can apply, to the first electrode <NUM>, a driving power for allowing the organic light emitting layer <NUM> of the OLED <NUM> in the pixel selected by the switching TFT <NUM>, to perform light emission. The driving gate electrode <NUM> can be connected to the capacitor plate <NUM>, which is connected to the switching drain electrode <NUM>. The driving source electrode <NUM> and the other capacitor plate <NUM> can be connected to the common power line <NUM>. The driving drain electrode <NUM> can be connected to the first electrode <NUM> of the OLED <NUM> through a contact hole.

Due to the configuration of the switching TFT <NUM> and the driving TFT <NUM> as described above, the switching TFT <NUM> can be operated by a gate voltage applied to the gate line <NUM> to thereby transmit a data voltage applied to the data line <NUM> to the driving TFT <NUM>. A voltage having a level that is substantially equal to a difference between a level of a data voltage transmitted by (or from) the switching TFT <NUM> and a level of a common voltage applied from the common power line <NUM> to the driving TFT <NUM> can be stored in the capacitor <NUM>. A current having a level equivalent to the level of the voltage stored in the capacitor <NUM> can flow into the OLED <NUM> through the driving TFT <NUM> such that the OLED <NUM> can emit light.

In the fourth exemplary embodiment, the first electrode <NUM> can be an anode that injects holes and the second electrode <NUM> can be a cathode that injects electrons. However, the fourth exemplary embodiment is not limited thereto, and can be modified such that the first electrode <NUM> is a cathode and the second electrode <NUM> is an anode.

A planarization layer <NUM> can be formed on the insulating interlayer <NUM>. The planarization layer <NUM> can be formed of an insulating material, and can protect the wiring unit <NUM>. The planarization layer <NUM> and the insulating interlayer <NUM> can be formed of the same material.

The driving drain electrode <NUM> of the driving TFT <NUM> can be connected to the first electrode <NUM> of the OLED <NUM> through the contact hole formed in the planarization layer <NUM>.

In the fourth exemplary embodiment, the first electrode <NUM> can include a reflective layer and the second electrode <NUM> can include a transflective layer. Accordingly, a light generated in the organic light emitting layer <NUM> can be transmitted through the second electrode <NUM> to be emitted. For example, the OLED display <NUM> according to the fourth exemplary embodiment is a top-emission-type display device.

The reflective layer and the transflective layer can be formed of one or more of the following metals: magnesium (Mg), silver (Ag), gold (Au), calcium (Ca), lithium (Li), chromium (Cr), aluminum (A1), and copper (Cu) or an alloy thereof. In this instance, the type of the layer, that is, whether the reflective layer or the transflective layer, can be determined based on a thickness of the layer. In general, the transflective layer has a thickness of less than or equal to about <NUM>. As the thickness of the transflective layer decreases, a level of light transmittance can increase, and as the thickness of the transflective layer increases, the level of light transmittance can decrease.

In detail, the first electrode <NUM> can include a reflective layer formed of one or more of the following metals: Mg, Ag, Au, Ca, Li, Cr, Al, and Cu, and a transparent conductive layer formed on the reflective layer. In this instance, the transparent conductive layer can be formed of transparent conductive oxide (TCO), for example, one or more of the following materials: indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), aluminum zinc oxide (AZO), and indium oxide (In2O3). Since such a transparent conductive layer has a relatively high work function, hole injection through the first electrode <NUM> can be readily performed.

In addition, the first electrode <NUM> can have a triple-layer structure in which a transparent conductive layer, a reflective layer, and a transparent conductive layer are sequentially stacked.

The second electrode <NUM> can include a transflective layer formed of one or more of the following metals: Mg, Ag, Au, Ca, Li, Cr, Al, and Cu.

Although not illustrated, at least one of a hole injection layer (HIL) and a hole transporting layer (HTL) can further be interposed between the first electrode <NUM> and the organic light emitting layer <NUM>. In addition, at least one of an electron transporting layer (ETL) and an electron injection layer (EIL) can further be interposed between the organic light emitting layer <NUM> and the second electrode <NUM>.

The organic light emitting layer <NUM>, the HIL, the HTL, the ETL, and the EIL can be referred to as an organic layer. Such an organic layer can be formed of a low molecular weight organic material or a polymer organic material.

The PDL <NUM> can have an aperture. The aperture of the PDL <NUM> can expose a portion of the first electrode <NUM>. The first electrode <NUM>, the organic light emitting layer <NUM>, and the second electrode <NUM> can be sequentially stacked in the aperture of the PDL <NUM>. The second electrode <NUM> can be formed on the organic light emitting layer <NUM> and on the PDL <NUM>. The PDL <NUM> can define a light emission area.

Although not illustrated, a capping layer can be formed on the second electrode <NUM>. The capping layer (not illustrated) can protect the OLED <NUM>.

In order to protect the OLED <NUM>, the second substrate <NUM> can be formed on the OLED <NUM> to be opposite to the first substrate <NUM>. The second substrate <NUM> can be formed of the same material as that forming the first substrate <NUM>.

The polarizer <NUM> can be formed on the display panel <NUM>. The polarizer <NUM> according to the fourth exemplary embodiment can have the same configuration as that of the polarizer according to the first exemplary embodiment. In detail, the polarizer <NUM> can be formed on the second substrate <NUM> corresponding to a display surface of the display panel <NUM>. In this instance, the polarizer <NUM> can be adhered to the second substrate <NUM> by the adhesive layer <NUM>. Since a description pertaining to the configuration of the polarizer <NUM> is provided with reference to the first exemplary embodiment, a detailed description thereof will be omitted herein for conciseness.

Hereinafter, a fifth exemplary embodiment will be described with reference to <FIG> is a cross-sectional view illustrating an OLED display <NUM> according to the fifth exemplary embodiment.

The OLED display <NUM> according to the fifth exemplary embodiment can include a thin film encapsulation layer <NUM> formed on an OLED <NUM>.

The thin film encapsulation layer <NUM> can include one or more inorganic layers <NUM>, <NUM>, and <NUM> and one or more organic layers <NUM> and <NUM>. The thin film encapsulation layer <NUM> can have a structure in which the inorganic layers <NUM>, <NUM>, and <NUM> and the organic layers <NUM> and <NUM> are alternately stacked. In this instance, the inorganic layer <NUM> can be formed as a lowermost layer of the stacked structure of the thin film encapsulation layer <NUM>. For example, the inorganic layer <NUM> is formed to be most adjacently to the OLED <NUM>. Although <FIG> illustrates the thin film encapsulation layer <NUM> as including the three inorganic layers <NUM>, <NUM>, and <NUM> and the two organic layers <NUM> and <NUM>, the fifth exemplary embodiment is not limited thereto.

The inorganic layers <NUM>, <NUM>, and <NUM> can be formed of one or more of the following materials: Al<NUM>O<NUM>, TiO<NUM>, ZrO, SiO<NUM>, AlON, A1N, SiON, Si<NUM>N<NUM>, ZnO, and Ta<NUM>O<NUM>. The inorganic layers <NUM>, <NUM>, and <NUM> can be formed through a chemical vapor deposition (CVD) process or an atomic layer deposition (ALD) process. However, the fifth exemplary embodiment is not limited thereto, and the inorganic layers <NUM>, <NUM>, and <NUM> can be formed through various processes known in the pertinent art.

The organic layers <NUM> and <NUM> can be formed of a polymer-based material. Such a polymer-based material can include an acrylic resin, an epoxy resin, polyimide, polyethylene, and the like. The organic layers <NUM> and <NUM> can be formed through a thermal deposition process. The thermal deposition process for forming the organic layers <NUM> and <NUM> can be performed within the range of temperature in which the OLED <NUM> is not damaged. However, the fifth exemplary embodiment is not limited thereto, and the organic layers <NUM> and <NUM> can be formed through various processes known in the pertinent art.

The inorganic layers <NUM>, <NUM>, and <NUM> formed to have a high density of a thin film can serve to reduce or effectively prevent the infiltration of moisture or oxygen thereinto. The infiltration of moisture or oxygen into the OLED <NUM> can be prevented largely by the inorganic layers <NUM>, <NUM>, and <NUM>.

Moisture or oxygen passing through the inorganic layers <NUM>, <NUM>, and <NUM> can be blocked further by the organic layers <NUM> and <NUM>. The organic layers <NUM> and <NUM> can exhibit relatively low efficiency in preventing the moisture infiltration, as compared to the inorganic layers <NUM>, <NUM>, and <NUM>. However, the organic layers <NUM> and <NUM> can also serve as a buffer layer to reduce stress between respective layers of the inorganic layers <NUM>, <NUM>, and <NUM> and the organic layers <NUM> and <NUM>, aside from preventing the moisture infiltration. Further, since the organic layers <NUM> and <NUM> have a planarization property, an uppermost surface of the thin film encapsulation layer <NUM> can be planarized.

The thin film encapsulation layer <NUM> can have a thickness of about <NUM> or less. Accordingly, an overall thickness of the OLED display <NUM> can be significantly reduced.

The polarizer <NUM> can be formed on the thin film encapsulation layer <NUM>. The polarizer <NUM> can use the polarizer according to the first exemplary embodiment.

As discussed, embodiments of the invention can provide a polarizer comprising: a linear polarizer; and a quarter-wave plate and a half-wave plate, wherein the half-wave plate comprises a refractive index anisotropic layer, wherein the refractive index anisotropic layer has a refractive index Nx defined in a direction of an x axis, a refractive index Ny defined in a direction of a y axis, and a refractive index Nz defined in a direction of a z axis, and wherein Nx = Nz > Ny.

In some embodiments, a phase retardation layer is provided on the linear polarizer that includes the quarter-wave plate and a half-wave plate. In some embodiments, each of the half-wave and quarter-wave plates is thinner than the linear polarizer.

As set forth above, according to at least one of the disclosed embodiments, the polarizer can include the phase difference plate having refractive index anisotropy, and can effectively prevent reflection of an external light irrespective of an incident angle of the external light. In addition, the display device can include the polarizer capable of effectively preventing reflection of external light, can be excellent in representing a black color, and can have a high contrast ratio.

Claim 1:
A polarizer (<NUM>) comprising:
a linear polarizer (no); and
a phase retardation layer (<NUM>) including a quarter-wave plate (<NUM>) and a half-wave plate (<NUM>) layered in a direction of a z axis,
wherein the half-wave plate comprises a refractive index anisotropic layer,
wherein the refractive index anisotropic layer has a refractive index Nx defined in a direction of an x axis, a refractive index Ny defined in a direction of a y axis, and a refractive index Nz defined in a direction of the z axis,
wherein the linear polarizer (no) and the phase retardation layer (<NUM>) are layered in a direction of the z axis,
wherein Nx = Nz > Ny,
wherein the refractive index anisotropic layer comprises a liquid crystal layer (<NUM>) comprising a discotic compound (<NUM>), and
wherein the discotic compound (<NUM>) has a disc surface, and wherein the disc surface has an inclination angle in the range of about <NUM> degrees to about <NUM> degrees with respect to a surface of the half-wave plate (<NUM>).