Optical laminates and optical display devices including them

Abstract

This invention discloses an optical laminate and an optical display device comprising the thereof. The optical laminate comprises: a polarizer; and a retardation layer stacked on the light incident surface of the polarizer, wherein the retardation layer comprises a positive C layer, the positive C layer having an in-plane retardation of 0 nm to 30 nm and an out-of-plane retardation of -50 nm to -15 nm at a wavelength of 550 nm, and the absolute values ​​of the in-plane retardation of the positive C layer and the tilt angle of the slow axis of the positive C layer relative to the light absorption axis of the polarizer at a wavelength of 550 nm satisfy Equation 1.

Description

[0001] Cross-citation of related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2021-0099112, filed on July 28, 2021, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to an optical laminate and an optical display device comprising the thereof. Background Technology

[0004] As a type of liquid crystal display, there exists an in-plane switching (IPS) mode liquid crystal display. IPS mode liquid crystal displays suffer from a low contrast ratio at diagonal angles and a large difference in visibility between the right and left sides due to the tilt of the liquid crystal.

[0005] Therefore, IPS-mode liquid crystal displays include a positive C-layer in the viewfinder-side polarizer to improve contrast ratio at diagonal angles and the difference in visibility between the right and left sides. However, there are limitations to achieving a significant reduction in the difference in visibility between the right and left sides while simultaneously significantly improving contrast ratio. Although the difference in visibility between the right and left sides is reduced, the improvement in contrast is not always consistent. In addition to the positive C-layer, a retardation layer providing a certain degree of phase retardation can be stacked on the lower surface of the polarizer, such as the upper or lower surface of the positive C-layer. However, this structure has the problem of increased polarizer thickness. The positive C-layer can be formed from liquid crystal. However, due to the high cost of liquid crystal and the low durability of the positive C-layer, this structure is economically infeasible.

[0006] The background technology of this invention is disclosed in Japanese Unexamined Patent Publication No. 2006-251659, etc. Summary of the Invention

[0007] One aspect of the present invention provides an optical laminate that improves the contrast ratio at the diagonal angle while reducing the visibility difference between the right and left sides when applied to an optical display panel.

[0008] Another aspect of the present invention provides an optical laminate capable of suppressing light leakage.

[0009] One aspect of the present invention relates to an optical laminate.

[0010] 1. An optical laminate comprises: a polarizer; and a retardation layer stacked on the light-incident surface of the polarizer, wherein the retardation layer comprises a positive C layer having an in-plane retardation of 0 nm to 30 nm and an out-of-plane retardation of -50 nm to -15 nm at a wavelength of 550 nm, and the absolute values ​​of the in-plane retardation of the positive C layer and the tilt angle of the slow axis of the positive C layer relative to the light absorption axis of the polarizer at a wavelength of 550 nm satisfy Equation 1:

[0011] [Relation 1]

[0012] 0°≤Y≤ax X b ,

[0013] Where X is the in-plane retardation of the positive C layer at a wavelength of 550 nanometers (unit: nanometer);

[0014] Y is the absolute value of the tilt angle of the slow axis of the positive C layer relative to the light absorption axis of the polarizer (unit: °);

[0015] a is 13.666; and b is -1.056.

[0016] 2. In 1, the tilt angle of the slow axis of the positive C layer relative to the light absorption axis of the polarizer can be in the range of -14° to +14°.

[0017] 3. In 1 and 2, Y in relation 1 can be in the range of 0° to 14.5°.

[0018] 4. In 1 to 3, the delay layer can be a single positive C layer.

[0019] 5. In 1 to 3, the slow axis of the positive C layer can be tilted at an angle of -14° to -1° or +1° to +14° relative to the longitudinal direction (machine direction; MD) of the positive C layer.

[0020] 6. In 1 to 5, the positive C layer may contain a stretched non-liquid crystal film.

[0021] 7. In 6, the positive C layer may include a stretch film, said stretch film comprising at least one resin selected from the following: cellulose ester resins, polyester resins, cyclic polyolefin resins, polycarbonate resins, polyethersulfone resins, polysulfone resins, polyamide resins, polyimide resins, polyolefin resins, polyaryl ester resins, polyvinyl alcohol resins, polyvinyl chloride resins, polyvinylidene chloride resins, and acrylic resins.

[0022] 8. In steps 1 to 7, the positive C layer can be bonded to the polarizer via an adhesive layer.

[0023] 9. In 1 to 8, the optical laminate may further include a protective layer stacked on the light-emitting surface of the polarizer.

[0024] 10. In 9, the tilt angle of the slow axis of the protective layer relative to the slow axis of the positive C layer can be in the range of -14° to +14°.

[0025] 11. In 9, the protective layer may have an in-plane delay of 3,000 nanometers or more at a wavelength of 550 nanometers.

[0026] Another aspect of the present invention relates to an optical display device.

[0027] The optical display device includes an optical laminate according to the present invention.

[0028] The present invention provides an optical laminate that improves the contrast ratio at the diagonal angle while reducing the visibility difference between the right and left sides when applied to an optical display panel.

[0029] This invention provides an optical laminate that can suppress light leakage. Attached Figure Description

[0030] Figure 1 This is a cross-sectional view of an optical laminate according to an embodiment of the present invention.

[0031] Figure 2 To illustrate the graph of relation 1.

[0032] Explanation of icon numbers

[0033] 10: Polarizing film;

[0034] 20: Positive C layer;

[0035] 30: Protective layer;

[0036] 40, 50: Adhesive layer;

[0037] Re: In-plane delay. Detailed Implementation

[0038] In the following description, embodiments of the invention will be described in detail with reference to the accompanying drawings to provide a thorough understanding of the invention by those skilled in the art. It should be understood that the invention may be embodied in different ways and is not limited to the following embodiments.

[0039] In the accompanying drawings, components irrelevant to the description are omitted for clarity of the invention, and the same components will be indicated by the same reference numerals throughout the specification. Although the length, thickness, or width of various components may be enlarged for understanding the drawings, the invention is not limited thereto.

[0040] In this document, spatial relative terms such as “upper” and “lower” are defined with reference to the accompanying drawings. Therefore, it will be understood that “upper surface” and “lower surface” can be used interchangeably, and when an element such as a layer or film is referred to as being placed “on” another element, the element may be placed directly on the other element, or there may be intervening elements present. On the other hand, when an element is referred to as being “placed directly on” another element, “immediately placed on” another element, “formed directly on” another element, or “formed in direct contact” with another element, there are no intervening elements between the element and the other element.

[0041] In this paper, "in-plane delay Re", "out-of-plane delay Rth", and "degree of biaxiality (NZ)" are represented by equations A, B, and C, respectively:

[0042] Re=(nx-ny)xd, ---(A)

[0043] Rth=((nx+ny) / 2-nz)xd, ---(B)

[0044] NZ=(nx-nz) / (nx-ny), ---(C)

[0045] Where nx, ny, and nz are the refractive indices of the optical device in the slow axis, fast axis, and thickness directions, respectively, at the measurement wavelength, and d is its thickness (unit: nanometers).

[0046] In this document, "+" indicates an angle in the clockwise direction, and "-" indicates an angle in the counterclockwise direction relative to the reference (0°).

[0047] As used in this article to indicate a specific numerical range, "X to Y" means "greater than or equal to X and less than or equal to Y".

[0048] The inventors of this invention provide an optical laminate that improves the contrast ratio at the diagonal angle while reducing the visibility difference between the right and left sides when applied to an optical display panel, specifically an IPS-mode liquid crystal panel. In related technologies, there are limitations in achieving a significant reduction in the visibility difference between the right and left sides while simultaneously significantly improving the contrast ratio.

[0049] The optical laminate according to the present invention comprises: a polarizer; and a retardation layer stacked on the light incident surface of the polarizer, wherein the retardation layer comprises a positive C layer having an in-plane retardation of 0 nm to 30 nm and an out-of-plane retardation of -50 nm to -15 nm at a wavelength of 550 nm, and the absolute values ​​of the in-plane retardation of the positive C layer and the tilt angle of the slow axis of the positive C layer relative to the light absorption axis of the polarizer at a wavelength of 550 nm satisfy Equation 1. The optical laminate according to the present invention can significantly improve the contrast ratio at the diagonal direction angle, and significantly reduce the visibility difference between the right and left sides when applied to an IPS mode liquid crystal panel.

[0050] In one embodiment, the delay layer may be a separate positive C layer, as described below. This means that the positive C layer exists only between the polarizer and the display panel as a delay layer.

[0051] In the following text, reference will be made to Figure 1 An optical laminate according to an embodiment of the present invention is described.

[0052] refer to Figure 1 The optical laminate may include a polarizer 10, a positive C layer 20, a protective layer 30, and adhesive layers 40 and 50.

[0053] A positive C layer is stacked on the lower surface of the polarizer 10, i.e., the light incident surface of the polarizer, through which internal light enters the polarizer. A protective layer is stacked on the upper surface of the polarizer 10, i.e., the light emitting surface of the polarizer, through which internal light exits the polarizer. Here, "internal light" refers to light emitted from an optical display panel, such as an IPS or FFS liquid crystal panel, and entering the polarizer. Internal light can also be light emitted from a backlight unit and exiting the liquid crystal panel after passing through it.

[0054] Positive C layer

[0055] The positive C layer 20 is obtained from the optical display panel (placed in) Figure 1 The transmission direction of the internal light emitted from the lower surface of the positive C layer 20 (not shown) is changed, causing the light to be emitted toward the polarizer 10. According to the present invention, the positive C layer improves the contrast and visibility on the right and left sides even when there is no other retardation layer on the light incident surface of the polarizer.

[0056] The positive C layer can have an in-plane retardation of 0 nm to 30 nm and an out-of-plane retardation of -50 nm to -15 nm at a wavelength of 550 nm. Within this range, the positive C layer can help maximize the contrast ratio at the diagonal angles while improving visibility on the right and left sides. Choosing the in-plane and out-of-plane retardations in combination with Relationship 1 described below improves the contrast ratio and visibility on the right and left sides, even when there is no other retardation layer between the positive C layer and the polarizer and / or on the lower surface of the positive C layer, i.e., when there is no other retardation layer between the positive C layer and the liquid crystal panel.

[0057] Specifically, the positive C layer can have wavelengths of 0 nm, 0.5 nm, 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm, 10 nm, 10.5 nm, 11 nm, 11.5 nm, 12 nm, 12.5 nm, 13 nm, 13.5 nm, 14 nm, 14.5 nm, and 15 nm at a wavelength of 550 nm. In-plane delay of nanometers, 15.5 nanometers, 16 nanometers, 16.5 nanometers, 17 nanometers, 17.5 nanometers, 18 nanometers, 18.5 nanometers, 19 nanometers, 19.5 nanometers, 20 nanometers, 20.5 nanometers, 21.5 nanometers, 22 nanometers, 22.5 nanometers, 23 nanometers, 23.5 nanometers, 24 nanometers, 24.5 nanometers, 25 nanometers, 25.5 nanometers, 26 nanometers, 26.5 nanometers, 27 nanometers, 27.5 nanometers, 28 nanometers, 28.5 nanometers, 29 nanometers, 29.5 nanometers, or 30 nanometers. To be precise, the positive C layer can have out-of-plane retardations of -50 nm, -49 nm, -48 nm, -47 nm, -46 nm, -45 nm, -44 nm, -43 nm, -42 nm, -41 nm, -40 nm, -39 nm, -38 nm, -37 nm, -36 nm, -35 nm, -34 nm, -33 nm, -32 nm, -31 nm, -30 nm, -29 nm, -28 nm, -27 nm, -26 nm, -25 nm, -24 nm, -23 nm, -22 nm, -21 nm, -20 nm, -19 nm, -18 nm, -17 nm, -16 nm, or -15 nm at a wavelength of 550 nm.

[0058] Preferably, the positive C layer has an in-plane retardation of 0.5 nm to 9 nm, more precisely 1 nm to 8 nm, at a wavelength of 550 nm. Preferably, the positive C layer has an out-of-plane retardation of -25 nm to -10 nm, more precisely -25 nm to -15 nm, at a wavelength of 550 nm.

[0059] The positive C layer is a stretched film and has a slow axis and a fast axis in its in-plane direction. Here, the slow axis corresponds to the direction that provides a relatively high refractive index in the in-plane direction, and the fast axis corresponds to the direction that provides a relatively low refractive index in the in-plane direction. According to the invention, a stretched film is used as the positive C layer in order to use a positive C layer with a slow axis. Since typical positive C layers composed of crystalline layers or positive C layers composed of amorphous layers and formed by coating do not require a stretching process, these positive C layers do not have a slow axis.

[0060] In one embodiment, the slow axis of the positive C layer is tilted relative to its longitudinal direction (MD) at an angle of -14° to -1° or +1° to +14°, specifically -14°, -13°, -12°, -11°, -10°, -9°, -8°, -7°, -6°, -5°, -4°, -3°, -2°, -1°, +1°, +2°, +3°, +4°, +5°, +6°, +7°, +8°, ​​+9°, +10°, +11°, +12°, +13°, or +14°, preferably at an angle of -10° to -2° or +2° to +10°. Within this range, the optical laminate can readily satisfy Relation 1.

[0061] In optical laminates, the absolute values ​​of the angles between the in-plane retardation and absorption axes of the positive C layer and the slow axis of the positive C layer at a wavelength of 550 nm satisfy Equation 1:

[0062] 0°≤Y≤ax X b , ---(1)

[0063] Where X is the in-plane retardation of the positive C layer at a wavelength of 550 nanometers (unit: nanometer);

[0064] Y is the absolute value of the tilt angle of the slow axis of the positive C layer relative to the light absorption axis of the polarizer (unit: °);

[0065] a is 13.666; and

[0066] b is -1.056.

[0067] In Equation 1, the tilt angle of the slow axis of the positive C layer relative to the light absorption axis of the polarizer can be positive (+) or negative (-).

[0068] Reference Figure 2 Describe relation 1 in detail. Figure 2 To illustrate the graph of relation 1.

[0069] refer to Figure 2 The X-axis indicates the in-plane retardation of the positive C layer (in nanometers), and the Y-axis indicates the absolute value of the tilt angle of the slow axis of the positive C layer relative to the light absorption axis of the polarizer (in degrees). Figure 2The graph shows a curved curve, where Y = ax × b, a is 13.666, and b is -1.056. Figure 2 The graphs shown correspond to the results in Tables 1 and 2.

[0070] Table 1

[0071] Y value 14.5 13.7 8.3 6.6 5.9 5.4 5.0 4.6 4.3 3.2 2.5 2.1 1.8

[0072] Table 2

[0073] Y value 1.5 1.3 1.2 1.1 1.0 0.9 0.8 0.8 0.7 0.6 0.5 0.5 0.4 0.4

[0074] Within the range of in-plane and out-of-plane retardation of the positive C layer, the combination of the tilt angle of the slow axis of the positive C layer relative to the light absorption axis of the polarizer and the in-plane retardation of the positive C layer, wherein the positive C layer has a certain in-plane retardation in the range of 0 nm to 30 nm, the positive C layer can be stacked on the polarizer such that the tilt angle of the slow axis of the positive C layer relative to the light absorption axis of the polarizer is included Figure 2 The curve diagram and the lower area below the curve diagram shown are shown. Figure 2 In the diagonal portion (as shown in the diagram), when applied to an IPS-mode LCD panel, a significant improvement in contrast ratio is achieved at the diagonal angle, while simultaneously significantly reducing the color visibility difference between the left and right sides. The inventors confirmed that when the absolute value of the angle between the slow axis of the positive C layer and the light absorption axis of the polarizer is greater than the Y value, an improvement in at least one of the contrast ratio at the diagonal angle and the color visibility difference at the diagonal angle can be easily achieved.

[0075] Despite the in-plane retardation variation of the positive C layer, the Y value can be in the range of 0° to 14.5°, specifically 0°, 0.5°, 1°, 1.5°, 2°, 2.5°, 3°, 3.5°, 4°, 4.5°, 5°, 5.5°, 6°, 6.5°, 7°, 7.5°, 8°, 8.5°, 9°, 9.5°, 10°, 10.5°, 11°, 11.5°, 12°, 12.5°, 13°, 13.5°, 14°, or 14.5°, preferably greater than 0° to 14.5° or 1° to 14.5°. Within this range, the optical laminate can effectively achieve the effects of the present invention.

[0076] In other words, the angle between the slow axis of the positive C layer and the light absorption axis of the polarizer can be in the range of -14.5° to +14.5°, specifically -14.5° to less than 0°, -14.5° to -1°, greater than 0° to +14.5°, or +1° to +14.5°. Within this range, the optical laminate can effectively achieve the effects of the present invention.

[0077] Next, we will describe the method to satisfy relation 1.

[0078] When determining the in-plane retardation of the positive C layer in an optical laminate, according to equation 1: Y = ax X b (a = 13.666, b = -1.056) Calculate the Y value, which is the range of absolute values ​​of the tilt angle of the slow axis of the positive C layer relative to the light absorption axis of the polarizer, and the positive C layers are stacked on the polarizer to satisfy the range of the calculated absolute values.

[0079] The positive C layer can be formed from a non-liquid crystal material that can achieve in-plane and out-of-plane retardation within the above range by stretching the non-liquid crystal material in a certain direction, so as to satisfy nz>nx=ny at a wavelength of 550 nm (nx, ny and nz are the refractive indices in the slow axis, fast axis and thickness direction at a wavelength of 550 nm, respectively).

[0080] In one embodiment, the positive C layer may be a stretched film formed from at least one resin selected from the following: cellulose resins, such as triacetyl cellulose (TAC); polyester resins, such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, etc.; cyclic polyolefin (COP) resins; polycarbonate resins; polyethersulfone resins; polysulfone resins; polyamide resins; polyimide resins; polyolefin resins; polyarylate resins; polyvinyl alcohol resins; polyvinyl chloride resins; polyvinylidene chloride resins; and acrylic resins, but not limited thereto.

[0081] In another embodiment, the positive C layer can be formed by preparing a non-stretched film from a composition comprising a cellulose compound or a polymer thereof and / or an aromatic compound or a polymer thereof, followed by stretching the non-stretched film. The compound may comprise monomers, oligomers, polymers, or resins.

[0082] Cellulose compounds may contain at least one unit in which at least some of the hydroxyl groups [C2 hydroxyl, C3 hydroxyl, or C6 hydroxyl] of the sugar monomer constituting cellulose are substituted with acyl or ester groups. That is, cellulose compounds may contain cellulose ester compounds and / or cellulose ether compounds.

[0083] For example, a cellulose compound may contain at least one unit in which at least some of the hydroxyl groups [C2 hydroxyl, C3 hydroxyl, or C6 hydroxyl] of the sugar monomer constituting cellulose are substituted with acyl groups, as represented by Formula 1, wherein the acyl groups may be substituted with substituents or unsubstituted:

[0084]

[0085] Where n is an integer of 1 or greater.

[0086] Substituents used for cellulose esters or acyl groups may include at least one selected from the following: halogen atom, nitro group, alkyl group (e.g., C1 to C1). 20 Alkyl), alkenyl (e.g., C2 to C3) 20 alkenyl), cycloalkyl (e.g., C3 to C4) 10 cycloalkyl), aryl (e.g., C6 to C6) 20 aryl), heteroaryl (e.g., C3 to C4), 10 aryl), alkoxy (e.g., C1 to C1) 20 Alkoxy, acyl, and halogen-containing functional groups. Substituents may be the same as or different from each other.

[0087] In this article, "acyl group" may refer to RC (=O)- * ( * For the linking site, R is C1 to C. 20 Alkyl, C3 to C 20 cycloalkyl, C6 to C 20 Aryl or C7 to C 20 Arylalkyl), as is well known in the field. The "acyl" group is coupled to the cellulose ring via an ester bond (through an oxygen atom) in cellulose.

[0088] Here, for convenience, "alkyl," "alkenyl," "cycloalkyl," "aryl," "heteroaryl," "alkoxy," and "acyl" refer to non-halogenated compounds. The composition used for the second retardation layer may comprise a single cellulose ester compound or a mixture comprising cellulose ester compounds.

[0089] Here, "halogen" refers to fluorine (F), Cl, Br or I, preferably F.

[0090] A "halogen-containing functional group" is an organic functional group containing at least one halogen atom and may include aromatic, aliphatic, or alicyclic functional groups. For example, a halogen-containing functional group may refer to a C1 to C2 group that has been halogenated. 20 Alkyl groups, halogenated C2 to C3 groups 20 Alkenyl, halogenated C2 to C 20 Alkyne group, halogenated C3 to C 10 cycloalkyl, halogenated C1 to C 20 Alkoxy, halogenated acyl, halogenated C6 to C 20 Aryl or halogenated C7 to C 20 Aryl groups, but not limited to them.

[0091] The halogen-substituted acyl group can be R'-C(=O)- * ( * R' is the linking site, where C1 to C is halogenated. 20Alkyl groups, halogenated C3 to C4 groups 20 cycloalkyl, halogenated C6 to C 20 Aryl or halogenated C7 to C 20 Arylalkyl). "Halogen-substituted acyl groups" can couple to the cellulose ring via ester bonds (through oxygen atoms) in cellulose.

[0092] For the formation of a positive C layer, cellulose ester compounds can be prepared by typical methods known to those skilled in the art, or can be obtained from commercially available products. For example, cellulose ester compounds having an acyl group as a substituent can be prepared by reacting trifluoroacetic acid or trifluoroacetic anhydride with a sugar monomer or polymer of a sugar monomer constituting cellulose represented by Formula 1, by reacting trifluoroacetic acid or trifluoroacetic anhydride with it, followed by further reacting with an acylating agent (e.g., an anhydride of a carboxylic acid or a carboxylic acid), or by reacting trifluoroacetic acid or trifluoroacetic anhydride with an acylating agent.

[0093] The aromatic compound contains a phenyl group and may contain, but is not limited to, a polystyrene compound, a fluorobenzene, or a difluorobenzene structure. In one embodiment, the polystyrene compound may contain a portion represented by Formula 2:

[0094]

[0095] in For the linking sites of atoms,

[0096] R 1 R 2 and R 3 Each is independently a hydrogen atom, alkyl group, substituted alkyl group, or halogen;

[0097] R are each an independent substituent on the styrene ring; and

[0098] n is an integer from 0 to 5 indicating the number of substituents on the styrene ring.

[0099] Examples of substituents R on the styrene ring may include alkyl, substituted alkyl, halogen, hydroxyl, carboxyl, nitro, alkoxy, amino, sulfonate, phosphate, acyl, acyloxy, phenyl, alkoxycarbonyl, and cyano.

[0100] In one embodiment, R 1 R 2 and R 3 At least one of them may be hydrogen or halogen, preferably hydrogen or fluorine.

[0101] The composition for the positive C layer may further comprise additives containing aromatic fused rings, other than cellulose compounds and aromatic compounds. These aromatic fused ring additives are used to adjust wavelength dispersion. They may include 2-naphthylbenzoate, anthracene, phenanthrene, 2,6-naphthalenedicarboxylate, etc. The aromatic fused ring additives may be present in the positive C layer composition in an amount from 0.1 wt% to 30 wt%, preferably from 1 wt% to 10 wt%. Within this range, the aromatic fused ring compounds can adjust retardation and wavelength dispersion.

[0102] A non-stretched film is prepared from the composition used for the positive C layer. The non-stretched film can be prepared from the composition used for the positive C layer by solution casting, melt extrusion, etc. Preferably, the non-stretched film is prepared from the composition used for the positive C layer by solution casting to improve processability and economic feasibility.

[0103] The positive C layer can be formed by uniaxially stretching a non-stretched film in an MD or TD. Stretching can be achieved by dry stretching and / or wet stretching and can be performed at temperatures from 70°C to 250°C, more precisely 80°C to 200°C, and even more precisely 100°C to 200°C. Within this range, the same stretching effect can be achieved.

[0104] The elongation can be adjusted depending on the in-plane and out-of-plane retardation of the positive C layer. For example, the unstretched membrane can be stretched to 1.2 to 5 times its initial length in each of the MD and TD, preferably 1.2 to 3 times.

[0105] Preferably, the positive C layer satisfies the equation: (nx + ny + nz) / 3 = 1.4 to 1.6, specifically 1.4, 1.41, 1.42, 1.43, 1.44, 1.45, 1.46, 1.47, 1.48, 1.49, 1.5, 1.51, 1.52, 1.53, 1.54, 1.55, 1.56, 1.57, 1.58, 1.59, 1.6, more precisely 1.48 to 1.51, and more precisely 1.49 to 1.50 (where nx, ny, and nz are the refractive indices along the slow axis, fast axis, and thickness direction, respectively, at a wavelength of 550 nm). Within this range, the positive C layer can improve color deviation when stacked on a polarizer via an adhesive layer.

[0106] Preferably, the positive C layer is formed of a material exhibiting negative birefringence. Here, "negative birefringence" means the characteristic of a transparent film that exhibits birefringence when stretched and has a refractive index that increases in the direction orthogonal to the stretching direction. For example, the positive C layer may be a film formed of at least one resin selected from cellulose ester resins including triacetyl cellulose (TAC), cyclic olefin polymer (COP) resins, and acrylic resins.

[0107] The positive C layer can have a size ranging from 1 micrometer to 60 micrometers, specifically 1 micrometer, 2 micrometers, 3 micrometers, 4 micrometers, 5 micrometers, 6 micrometers, 7 micrometers, 8 micrometers, 9 micrometers, 10 micrometers, 11 micrometers, 12 micrometers, 13 micrometers, 14 micrometers, 15 micrometers, 16 micrometers, 17 micrometers, 18 micrometers, 19 micrometers, 20 micrometers, 21 micrometers, 22 micrometers, 23 micrometers, 24 micrometers, 25 micrometers, 26 micrometers, 27 micrometers, 28 micrometers, 29 micrometers, 30 micrometers, and 31 micrometers. Thicknesses ranging from 20 to 50 micrometers are preferred, including 32 micrometers, 33 micrometers, 34 micrometers, 35 micrometers, 36 micrometers, 37 micrometers, 38 micrometers, 39 micrometers, 40 micrometers, 41 micrometers, 42 micrometers, 43 micrometers, 44 micrometers, 45 micrometers, 46 micrometers, 47 micrometers, 48 ​​micrometers, 49 micrometers, 50 micrometers, 51 micrometers, 52 micrometers, 53 micrometers, 54 micrometers, 55 micrometers, 56 micrometers, 57 micrometers, 58 micrometers, 59 micrometers, or 60 micrometers. Within this range, the positive C layer can be applied to optical laminates, and the phase retardation according to the invention can be readily achieved.

[0108] polarizer

[0109] The polarizer 10 includes a light-absorbing polarizer that divides the incident light into two polarized portions that are orthogonal to each other, allowing one of the two polarized portions to pass through while absorbing the other portion.

[0110] In one embodiment, in the in-plane direction of the polarizer, the axis of the polarizer exhibiting a higher refractive index can be the light absorption axis, and the axis of the polarizer exhibiting a lower refractive index can be the light transmission axis.

[0111] In one embodiment, the light absorption axis of the polarizer may correspond to the longitudinal direction (MD), and the light transmission axis of the polarizer may correspond to its transverse direction (TD).

[0112] The polarizer 10 may have a polarization of 95% or greater, specifically 95% to 100%, more precisely 98% to 100%. Within this range, the polarizer can further improve frontal contrast while also improving durability.

[0113] The polarizer 10 may have a transmittance of 40% or greater, specifically 40% to 45%. Within this range, the polarizer can be used in optical laminates.

[0114] The polarizer 10 may comprise a polarizer containing a dichroic dye that has undergone uniaxial stretching.

[0115] Specifically, a dichroic dye-containing polarizer may be prepared by uniaxially stretching a base film in a dielectric film (MD) and then dyeing it with a dichroic dye (e.g., iodine or potassium iodide as the iodine-containing substance). The base film may comprise, but is not limited to, a polyvinyl alcohol film or a derivative thereof. The polarizer may be manufactured by typical methods known to those skilled in the art.

[0116] The polarizer 10 may have a thickness of 1 micrometer to 40 micrometers, more precisely 5 micrometers to 30 micrometers, and even more precisely 10 micrometers to 25 micrometers. Within this range, the polarizer can be used in optical laminates.

[0117] protective layer

[0118] The protective layer 30 can be placed on the light emitting surface of the polarizer 10 to protect the polarizer or to further improve image quality by controlling the light emitted from the polarizer.

[0119] The protective layer 30 may include a protective film or a protective coating.

[0120] The protective film is an optically transparent film and can be formed from at least one resin selected from the following: for example, cellulose resins, such as triacetyl cellulose (TAC); polyester resins, such as polyethylene terephthalate, polybutylene terephthalate (PET), polyethylene naphthalate, and polybutylene naphthalate; cyclic polyolefin resins; polycarbonate resins; polyethersulfone resins; polysulfone resins; polyamide resins; polyimide resins; polyolefin resins; polyarylate resins; polyvinyl alcohol resins; polyvinyl chloride resins; and polyvinylidene chloride resins. Specifically, TAC films or PET films can be used. The protective coating can be formed from a heat-curable composition and / or a light-curable composition.

[0121] In one embodiment, the protective layer may be a delay film.

[0122] In one embodiment, the protective layer may have an in-plane retardation (Re) of 3,000 nm or greater at a wavelength of 550 nm, specifically 3,000 nm, 4,000 nm, 5,000 nm, 6,000 nm, 7,000 nm, 8,000 nm, 9,000 nm, 10,000 nm, 11,000 nm, 12,000 nm, 13,000 nm, 14,000 nm, or 15,000 nm, preferably 5,000 nm to 15,000 nm, and more preferably 5,000 nm to 12,000 nm. Within this range, the protective film can achieve improved frontal contrast while suppressing the formation of rainbow spots.

[0123] In one embodiment, the protective layer may have an out-of-plane retardation (Rth) of 6,000 nm or more at a wavelength of 550 nm, specifically 6,000 nm, 7,000 nm, 8,000 nm, 9,000 nm, 10,000 nm, 11,000 nm, 12,000 nm, 13,000 nm, 14,000 nm, or 15,000 nm, preferably 6,000 nm to 15,000 nm, and more preferably 6,000 nm to 12,000 nm. Within this range, the protective layer can suppress the generation of light spots attributable to birefringence, while improving the viewing angle characteristics in the liquid crystal display device.

[0124] In one embodiment, the protective layer may have a degree of biaxiality (NZ) of 2.5 or less at a wavelength of 550 nm, specifically 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, or 2.5, preferably 1.0 to 2.2, more preferably 1.2 to 2.0, and even more preferably 1.4 to 1.8. Within this range, the protective layer can suppress the generation of light spots attributable to birefringence while maintaining its mechanical strength.

[0125] In one embodiment, the protective layer may be a film formed from the aforementioned material and stretched at a predetermined elongation rate. Therefore, the protective layer may have a slow axis and a fast axis in its in-plane direction.

[0126] In one embodiment, the axis of the protective layer exhibiting a low refractive index can be its longitudinal direction (MD), and the axis of the protective layer exhibiting a high refractive index can be its transverse direction (TD). In this case, the protective layer can be a TD uniaxially stretched protective film.

[0127] In another embodiment, the axis of the protective layer exhibiting a low refractive index can be its TD, and the axis of the protective layer exhibiting a high refractive index can be its MD. In this case, the protective layer can be a protective film uniaxially stretched by MD.

[0128] In another embodiment, in the in-plane direction of the protective layer, the axis of the protective layer exhibiting a low refractive index may be an inclined direction relative to its TD, and the axis of the protective layer exhibiting a high refractive index may be an inclined direction relative to its MD. In this case, the protective layer may be a protective film or coating biaxially stretched by MD / TD.

[0129] Preferably, in the in-plane direction of the protective layer, the axis exhibiting a high refractive index can be its MD, and the axis exhibiting a low refractive index can be its TD. This allows the axial relationship between the retardation layer and the polarizer to be considered during the manufacture of the optical laminate, improving processability and economic feasibility through roll-to-roll processing. The following description will focus on the above structure.

[0130] In one embodiment, the protective layer may comprise a TD uniaxially stretched protective film to have an axis exhibiting a low refractive index and an axis exhibiting a high refractive index in an in-plane direction.

[0131] TD uniaxial stretch protective film can be manufactured by stretching a non-stretched film formed by melt extrusion of a resin used for the protective film to a length that is only 100% to 200% of the width of the initial resin film in TD, preferably 120% to 140%.

[0132] Stretching can be achieved by dry stretching and / or wet stretching and can be performed at temperatures ranging from (Tg-20)℃ to (Tg+50)℃, where Tg is the glass transition temperature of the resin used for the protective film, specifically 70℃ to 250℃, more precisely 80℃ to 200℃, and even more precisely 100℃ to 200℃. Within this range, it is possible to achieve the same stretching effect.

[0133] In one embodiment, the slow axis of the protective layer is tilted relative to the slow axis of the positive C layer at an angle of -14° to +14°, specifically -14°, -13°, -12°, -11°, -10°, -9°, -8°, -7°, -6°, -5°, -4°, -3°, -2°, -1°, 0°, +1°, +2°, +3°, +4°, +5°, +6°, +7°, +8°, ​​+9°, +10°, +11°, +12°, +13°, or +14°, preferably -9° to +9°, more preferably 0°. Within this range, the protective film can provide improved contrast while reducing the impact of visibility differences on the right and left sides.

[0134] The protective layer 30 may have a thickness of 100 micrometers or less, more precisely greater than 0 micrometers to 70 micrometers, more precisely 5 micrometers to 70 micrometers, and more precisely 15 micrometers to 80 micrometers. Within this range, the protective layer may be used in optical laminates.

[0135] although Figure 1 Not shown, but the protective layer 30 may have a functional coating formed on its upper surface to provide additional functionality to the optical laminate. For example, the functional coating may include at least one selected from the group consisting of: a hard coating, an anti-fingerprint layer, an anti-reflective layer, an anti-glare layer, a low-reflective layer, and combinations thereof.

[0136] Adhesive layer

[0137] The polarizer 10 can be bonded to the positive C layer 20 via the adhesive layer 50. The polarizer 10 can be bonded to the protective layer 30 via the adhesive layer 40.

[0138] Each of the bonding layers 40 and 50 may be formed by a typical adhesive, such as a water-based adhesive or a light-curable adhesive, as is well known to those skilled in the art. Preferably, each of the bonding layers 40 and 50 is formed by a light-curable adhesive. The bonding layers 40 and 50 may have the same thickness or different thicknesses, and each of the bonding layers 40 and 50 may have a thickness of 1 micrometer to 10 micrometers, specifically 2 micrometers to 5 micrometers, but is not limited thereto.

[0139] The polarizing plate can have a polarization degree of 99.999% or greater, for example, from 99.999% to 100%. To measure the polarization degree, an optical laminate is mounted in a device for measuring polarization degree, such as a UV-VIS spectrophotometer, in which a reference polarizer with a polarization degree of 99.999% is mounted. Subsequently, with the polarizer in the optical laminate positioned such that its absorption axis is orthogonal or parallel to the absorption axis of the reference polarizer, light is transmitted through the optical laminate from the positive C layer toward the polarizer to measure the polarization degree.

[0140] The optical display device according to the present invention comprises an optical laminate according to the present invention. In one embodiment, the optical display device comprises an IPS or FFS mode liquid crystal display device.

[0141] The liquid crystal display device includes a liquid crystal panel, an optical laminate according to the invention on the light emitting surface of the liquid crystal panel, and a polarizing plate (light source-side polarizing plate) on the light incident surface of the liquid crystal panel. The polarizing plate disposed on the light incident surface of the liquid crystal panel may include typical polarizing plates known to those skilled in the art. The optical laminate according to the invention can be used as a viewer-side polarizing plate, but is not limited thereto. Alternatively, the optical laminate can be used as a viewer-side polarizing plate or a light source-side polarizing plate.

[0142] The liquid crystal panel allows the alignment of the liquid crystals to be changed depending on whether a voltage is applied to it, so that light emitted from the light source can pass through the liquid crystal panel.

[0143] A liquid crystal panel may comprise a pair of substrates and a liquid crystal layer inserted between the substrates and serving as a display medium. One substrate (color filter substrate) is equipped with a color filter and a black matrix, and the other substrate (active matrix substrate) is equipped with switching elements (e.g., TFTs) for controlling the electrical and optical properties of the liquid crystal and signal lines and pixel lines for supplying gate signals to the switching elements, but is not limited thereto.

[0144] In one embodiment, the liquid crystal panel may employ in-plane switching (IPS) mode or edge field switching (FFS) mode liquid crystal. Therefore, the liquid crystal display can improve viewing angle characteristics.

[0145] Liquid crystal panels can have an in-plane delay of 60 nanometers to 150 nanometers, more precisely 70 nanometers to 120 nanometers, at a wavelength of 550 nanometers. Within this range, liquid crystal panels can help improve viewing angle characteristics. The in-plane delay of a liquid crystal panel at a wavelength of 550 nanometers can be controlled by adjusting the thickness of the liquid crystal layer.

[0146] The liquid crystal display device includes a light source on the lower surface of the light source-side polarizing plate. The light source may include a light source with a continuous emission spectrum. For example, the light source may include a white LED light source, a quantum dot (QD) light source, a metal fluoride red phosphor light source, specifically KSF (K2SiF6:Mn). 4+ ) fluorophore or KTF(K2TiF6:Mn 4+ (Including phosphor light sources, etc.)

[0147] The invention will now be described in more detail with reference to examples. However, it should be noted that these examples are provided for illustrative purposes only and should not be construed as limiting the invention in any way.

[0148] Example 1

[0149] A polyvinyl alcohol film (VF-TS#4500, thickness: 45 μm, Kuraray Co., Ltd.) was uniaxially stretched to twice its initial length in MD at 30°C, stained with iodine, and stretched in an aqueous boric acid solution at 60°C to prepare a polarizer (thickness: 18 μm).

[0150] Unstretched films are produced by solution casting of a composition for a positive C layer (containing cellulose ester compounds, VM series, Eastman Co., Ltd.) followed by biaxial stretching at 140°C to prepare a positive C film (thickness: 30 micrometers).

[0151] A polyethylene terephthalate (PET) film with an anti-glare coating (thickness: 85 μm, Re: 8,500 nm at 550 nm, Rth: 9,300 nm at 550 nm, TD uniaxial stretched film, Toyobo Co., Ltd.) is bonded to the upper surface of a polarizer. A positive C film is bonded to the lower surface of the polarizer to prepare an optical laminate. Bonding is performed using a UV-curable adhesive, and each bonded layer has a thickness of 2 to 3 μm.

[0152] In the optical laminate, the slow axis of the PET film is tilted at an angle of 0° relative to the slow axis of the positive C film.

[0153] Examples 2 to 10

[0154] Each optical laminate is manufactured in the same manner as in Example 1, except that the retarded positive C film, as listed in Table 3, is formed by changing the elongation and / or stretching temperature of the positive C film and the tilt angle of the positive C film relative to the light absorption axis of the polarizer listed in Table 3.

[0155] Comparison Example 1

[0156] The optical laminate was manufactured in the same manner as in Example 1, except that the tilt angle of the positive C film relative to the light absorption axis of the polarizer was changed as listed in Table 3.

[0157] Comparison Example 2

[0158] The optical laminate was manufactured in the same manner as in Example 3, except that the tilt angle of the positive C film relative to the light absorption axis of the polarizer was changed as listed in Table 3.

[0159] Comparison Example 3

[0160] The optical laminate was manufactured in the same manner as in Example 5, except that the tilt angle of the positive C film relative to the light absorption axis of the polarizer was changed as listed in Table 3.

[0161] Compare Example 4 to Compare Example 6

[0162] Each optical laminate is manufactured in the same manner as in Example 1, except that the retarded positive C film, as listed in Table 3, is formed by changing the elongation and / or stretching temperature of the positive C film and the tilt angle of the positive C film relative to the light absorption axis of the polarizer listed in Table 3.

[0163] Manufacturing light source side polarizer

[0164] The polarizer is manufactured in the same manner as described above. A triacetyl cellulose (TAC) film (KC4CT1SW, thickness: 40 micrometers, Konica Minolta Opto Inc.) is bonded to the upper surface of the polarizer, and a polyethylene terephthalate (PET) film (thickness: 80 micrometers, Re: 8,400 nm at 550 nm, Rth: 9,800 nm at 550 nm, Toyoboki Co., Ltd.) is bonded to the lower surface of the polarizer to manufacture the light source-side polarizer.

[0165] Manufacturing LCD modules

[0166] In the examples and comparative examples, each of the optical laminates manufactured is bonded to the light-emitting surface of the liquid crystal panel containing the IPS liquid crystal via an adhesive layer. Here, the positive C layer of the optical laminate is bonded to the liquid crystal panel. A liquid crystal module is manufactured by bonding a light source-side polarizing plate to the light-incident surface of the liquid crystal panel containing the IPS liquid crystal via an adhesive layer. Here, the TAC film of the light source-side polarizing plate is bonded to the liquid crystal panel.

[0167] Regarding the optical laminates manufactured in the attribute evaluation examples and comparison examples listed in Table 3.

[0168] (1) Right and Left Visibility: Liquid crystal modules were manufactured from each of the optical laminates in the examples and comparative examples using the method described above. The left (45°) / right (135°) angles were set at a black azimuth angle of 60° using the EZ-contrast XL-88, and color coordinates (x, y) were obtained at each of (45°, 60°) and (135°, 60°). The distance between (45°, 60°) and (135°, 60°) was calculated as Δ(x, y). Δ(x, y) of 0.21 or less was rated ◎; Δ(x, y) greater than 0.21 to 0.23 was rated ○; Δ(x, y) greater than 0.23 to 0.25 was rated △; and Δ(x, y) greater than 0.25 was rated x.

[0169] (2) Contrast Ratio: The contrast ratio of the liquid crystal module at a diagonal angle is measured using an SR3 spectroradiometer (TOPCON). The contrast ratio is obtained by calculating the ratio of brightness in white mode to brightness in black mode. A higher contrast ratio of 1,140 or higher indicates better screen quality.

[0170] Table 3

[0171]

[0172] * The angles in Table 3: In optical laminates (unit: °), the angle of the slow axis of the positive C layer relative to the light absorption axis of the polarizer.

[0173] * In Equation 1, Y: a × X b The absolute value of (X is the in-plane retardation of the positive C layer at a wavelength of 550 nanometers (unit: nanometer), a is 13.666 and b is -1.056)

[0174] As shown in Table 3, the optical laminate according to the present invention achieves an improved contrast ratio at the diagonal angle, while reducing the visibility difference between the right and left sides when applied to an optical display panel. Furthermore, although not shown in Table 3, the optical laminate according to the present invention suppresses light leakage. Conversely, the optical laminates of the comparative examples failed to provide the effects of the present invention.

[0175] Although some embodiments have been described herein, it should be understood that those skilled in the art can make various modifications, alterations, changes and equivalent embodiments without departing from the spirit and scope of the invention.

Claims

1. An optical laminate, comprising: Polarizing film; as well as Delay layer, stacked on the light incident surface of the polarizer. The retardation layer comprises a positive C layer, which has an in-plane retardation of 0 nm to 30 nm and an out-of-plane retardation of -50 nm to -15 nm at a wavelength of 550 nm. The absolute values ​​of the in-plane retardation of the positive C layer and the tilt angle of the slow axis of the positive C layer relative to the light absorption axis of the polarizer at a wavelength of 550 nm satisfy Equation 1: [Relation 1] 0° < Y < a x X b Where X is the in-plane delay of the positive C layer at a wavelength of 550 nanometers, and the unit of X is nanometers; Y is the absolute value of the tilt angle of the slow axis of the positive C layer relative to the light absorption axis of the polarizer, where the unit of Y is °; a is 13.666; and b is -1.056; The delay layer is a single positive C layer; The slow axis of the positive C layer is tilted relative to the longitudinal direction of the positive C layer at an angle of -14° to -1° or +1° to +14°.

2. The optical laminate according to claim 1, wherein the tilt angle of the slow axis of the positive C layer relative to the light absorption axis of the polarizer is in the range of -14° to +14°.

3. The optical laminate according to claim 1, wherein Y in relation 1 is in the range of 0° to 14.5°.

4. The optical laminate according to claim 1, wherein the positive C layer comprises a stretched non-liquid crystal film.

5. The optical laminate according to claim 4, wherein the positive C layer comprises a stretch film, the stretch film comprising at least one resin selected from the group consisting of cellulose ester resins, polyester resins, cyclic polyolefin resins, polycarbonate resins, polyethersulfone resins, polysulfone resins, polyamide resins, polyimide resins, polyolefin resins, polyaryl ester resins, polyvinyl alcohol resins, polyvinyl chloride resins, polyvinylidene chloride resins, and acrylic resins.

6. The optical laminate of claim 1, wherein the positive C layer is stacked on the polarizer via an adhesive layer.

7. The optical laminate of claim 1, further comprising: A protective layer stacked on the light-emitting surface of the polarizer.

8. The optical laminate of claim 7, wherein the tilt angle of the slow axis of the protective layer relative to the slow axis of the positive C layer is in the range of -14° to +14°.

9. The optical laminate of claim 7, wherein the protective layer has an in-plane delay of 3,000 nanometers or more at a wavelength of 550 nanometers.

10. An optical display device comprising an optical laminate as claimed in any one of claims 1 to 9.

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