TWI861367B - Polarizing plate for light emitting displays and light emitting display comprising the same - Google Patents

Abstract

A polarizing plate for light emitting displays and a light emitting display including the same are provided. The polarizing plate includes: a polarizer; and a first bonding layer, a first liquid crystal retardation film, a second bonding layer and a second liquid crystal retardation film sequentially stacked on a surface of the polarizer, wherein the polarizing plate has a polarization degree variation ΔPE₁ of 0.7% or less according to Equation 1 and a polarization degree variation ΔPE₂ of 0.7% or less according to Equation 2, respectively.

Description

Polarizer for luminescent display and luminescent display including the same

The embodiments of the present invention relate to a polarizer for a luminescent display and a luminescent display comprising the same.

Cross-reference to related applications

This application claims priority to and the rights of Korean Patent Application No. 10-2020-0028641 filed on March 6, 2020 with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference.

Unlike liquid crystal displays, organic light-emitting displays are self-emissive display devices and do not require a separate polarizer. However, when an organic light-emitting display includes a polarizer having a retardation film having a predetermined range of phase retardation between the polarizer and the organic light-emitting device panel, the screen quality can be improved by preventing reflection of external light by converting linear polarization received from the polarizer into circular polarization.

Thin liquid crystal retardation films are currently used as retardation films, thereby achieving improved screen quality and reduced polarizer thickness. As retardation films, stacking of λ/2 retardation liquid crystal films and λ/4 retardation liquid crystal films has been used in the field, but is not limited thereto. Therefore, a bonding layer showing higher peeling strength than both λ/2 retardation liquid crystal films and λ/4 retardation liquid crystal films is required. In addition, with the recent development of foldable displays, polarizers suitable for both organic light-emitting displays and foldable displays are required.

The background technology of the present invention is disclosed in Japanese Patent Publication No. 2014-032270.

One aspect of the present invention is to provide a polarizer that exhibits good peeling strength relative to a liquid crystal retardation film and ensures good reliability and flexibility.

Another aspect of the present invention is to provide a polarizer that can minimize or reduce the effect on polarized light passing through the first liquid crystal retardation film and the second liquid crystal retardation film.

Embodiment 1: One aspect of the present invention is related to a polarizer for a luminescent display. A polarizer for a light-emitting display comprises: a polarizer; and a first bonding layer, a first liquid crystal retardation film, a second bonding layer, and a second liquid crystal retardation film sequentially stacked on a surface of the polarizer, wherein the polarizer has a polarization change ΔPE ₁ of 0.7% or less than 0.7% according to equation 1 and a polarization change ΔPE 2 of 0.7% or less than 0.7% according to equation ₂ : [Equation 1] ΔPE ₁ = |P1-P2|, wherein P1 indicates an initial polarization (unit: %) measured on a sample having a length of 3 cm and a width of 3 cm obtained by cutting the polarizer along the MD of the polarizer and the TD of the polarizer, and P2 indicates a polarization (unit: %) measured on the sample after the sample is placed at a constant temperature of 85° C. for 500 hours; and [Equation 2] ΔPE ₂ = |P1-P3|, where P1 indicates the initial polarization degree (unit: %) measured on a sample with a length of 3 cm and a width of 3 cm obtained by cutting the polarizer along the MD of the polarizer and the TD of the polarizer, and P3 indicates the polarization degree (unit: %) measured on the sample with a length of 3 cm and a width of 3 cm after the sample is placed under constant temperature and humidity conditions of 60°C and 95% for 500 hours.

Embodiment 2: In Embodiment 1, the second bonding layer may be directly formed on each of the first liquid crystal retardation film and the second liquid crystal retardation film.

Example 3: In Example 1 or Example 2, the second bonding layer may be formed of a composition including an epoxy compound and a (meth)acrylate compound, wherein the (meth)acrylate compound may include a hydrophobic (meth)acrylate compound.

Example 4: In Example 3, the hydrophobic (meth)acrylate compound may include a (meth)acrylate containing an unsubstituted linear or branched C ₆ to C ₂₀ alkyl group and a (meth)acrylate containing an unsubstituted aromatic group.

Embodiment 5: In Embodiment 4, the (meth)acrylate containing an unsubstituted linear or branched _C6 to _C20 alkyl group may include at least one of isodecyl (meth)acrylate and decyl (meth)acrylate.

Example 6: In Examples 1 to 5, the epoxy compound may include an alicyclic epoxy compound.

Example 7: In Examples 1 to 6, the epoxy compound may further include glycidyl ether containing an aromatic group.

Example 8: In Example 7, the aromatic group-containing glycidyl ether may include at least one of phenyl glycidyl ether and resorcinol diglycidyl ether.

Example 9: In Examples 1 to 8, the composition may not contain a (meth)acrylate compound containing a hydrophilic group.

Example 10: In Examples 1 to 9, the amount of the (meth)acrylate compound may be 25 to 65 parts by weight based on a total of 100 parts by weight of the epoxy compound and the (meth)acrylate compound.

Example 11: In Examples 1 to 10, the composition may further include a photocation ion initiator and a photoradical initiator.

Example 12: In Examples 1 to 11, the composition may include: 35 to 90 parts by weight of an epoxy compound; 10 to 65 parts by weight of a (meth)acrylate compound; 1 to 10 parts by weight of a photocationic ion initiator based on a total of 100 parts by weight of the epoxy compound and the (meth)acrylate compound; 0.5 to 10 parts by weight of a photoradical initiator based on a total of 100 parts by weight of the epoxy compound and the (meth)acrylate compound.

Example 13: In Examples 1 to 12, the second bonding layer may have a glass transition temperature of 70°C to 110°C.

Example 14: In Examples 1 to 13, the first bonding layer may be formed of a composition including an epoxy compound and a (meth)acrylate compound, wherein the (meth)acrylate compound may include a hydrophobic (meth)acrylate compound.

Example 15: In Example 14, the composition may not contain a (meth)acrylate compound containing a hydrophilic group.

Example 16: In Examples 1 to 15, the first bonding layer may have a glass transition temperature of 70°C to 110°C.

Embodiment 17: In Embodiments 1 to 16, each of the first liquid crystal retardation film and the second liquid crystal retardation film may be formed of a composition including at least one of a (meth)acrylic liquid crystal compound containing an alicyclic group and a (meth)acrylic liquid crystal compound containing an aromatic group.

Example 18: In Examples 1 to 17, the polarizer may further include a protective layer on another surface of the polarizer.

Another aspect of the present invention relates to a light-emitting display.

Embodiment 19: The luminescent display may include a polarizer for a luminescent display according to the present invention.

Embodiment 20: In embodiment 19, the light-emitting display may include a foldable light-emitting display.

The present invention provides a polarizer that exhibits good peeling strength relative to a liquid crystal retardation film and ensures good reliability and flexibility.

The present invention provides a polarizer capable of minimizing the influence on polarized light passing through a first liquid crystal retardation film and a second liquid crystal retardation film.

10: Polarizer

20: First liquid crystal retardation film

30: Second bonding layer

40: Second liquid crystal retardation film

50: First bonding layer

60: Protective layer

FIG1 is a cross-sectional view of a polarizer for a light-emitting display according to an embodiment of the present invention.

Figure 2 is a cross-sectional view of a polarizer for a light-emitting display according to another embodiment of the present invention.

The embodiments of the present invention will be described in detail with reference to the accompanying drawings to provide a thorough understanding of the present invention to those of ordinary skill in the art. It should be understood that the present invention can be implemented in different ways and is not limited to the following embodiments. In the drawings, parts not related to the description may be omitted for clarity. Throughout the specification, the same components will be represented by the same figure numbers. It should be understood that in order to facilitate the description of the present invention, the length, thickness, and the like of each component may be exaggerated or not described in proportion to the accompanying drawings and the present invention is not limited thereto.

In this document, spatially related terms such as "upper" and "lower" are defined with reference to the accompanying drawings. Thus, for example, it should be understood that the term "upper surface" can be used interchangeably with the term "lower surface".

In this article, "in-plane retardation (Re)" is the value measured at a wavelength of 550 nm and is expressed by equation A: [Equation A] Re = (nx-ny) × d

Where nx and ny are the refractive indices on the slow axis and fast axis of the liquid crystal retardation film at a wavelength of 550 nanometers, respectively, and d is the thickness of the liquid crystal retardation film (unit: nm).

In this document, the term "light emitting device" includes organic or inorganic light emitting devices and may refer to light emitting diodes (LEDs), organic light emitting diodes (OLEDs), quantum dot light emitting diodes (QLEDs), devices containing light emitting substances such as phosphors, and the like.

且

Y」。 In this document, "X to Y" means "X or greater than X to Y or less than Y" or "X

and

Y".

Based on the following discovery, in a polarizer for a light-emitting display comprising a polarizer, a first bonding layer, a first liquid crystal retardation film, a second bonding layer, and a second liquid crystal retardation film stacked in the stated order, the inventors improve the peeling strength of the second bonding layer relative to each of the first liquid crystal retardation film and the second liquid crystal retardation film, achieve good flexibility and reliability of the polarizer under high temperature conditions, and minimize the influence on reflected light by the liquid crystal retardation film to complete the present invention.

The present invention can ensure favorable effects by using a specific composition of a first bonding layer for bonding between a first liquid crystal retardation film and a polarizer and a specific composition of a second bonding layer for bonding the first liquid crystal retardation film to a second liquid crystal retardation film in a plurality of bonding layers or adhesive layers in a polarizer for a light-emitting display.

Hereinafter, the polarizer for a light-emitting display according to the present invention (hereinafter, "polarizer") will be described with reference to FIG. 1.

Referring to FIG. 1 , the polarizer may include a polarizer 10; and a first bonding layer 50, a first liquid crystal retardation film 20, a second bonding layer 30, and a second liquid crystal retardation film 40 sequentially formed on one surface of the polarizer 10.

Second bonding layer

The second bonding layer 30 may be formed directly on each of the first liquid crystal retardation film 20 and the second liquid crystal retardation film 40. Herein, the expression "formed directly on..." means that, except for the second bonding layer 30, another bonding layer, another adhesive layer, or another adhesive layer/bonding layer is not inserted between the first liquid crystal retardation film 20 and the second liquid crystal retardation film 40.

The second bonding layer 30 has a higher peeling strength relative to each of the first liquid crystal retardation film 20 and the second liquid crystal retardation film 40, and thus prevents separation between the first liquid crystal retardation film and the second liquid crystal retardation film, thereby maintaining the shape of the polarizer and preventing separation or bubbling under reliability test conditions (especially under high temperature/high humidity).

For each of the first liquid crystal retardation film and the second liquid crystal retardation film, the second bonding layer may have a peeling strength of 100 gf/25 mm or greater, for example, 100 gf/25 mm to 3000 gf/25 mm. Within this range, it is possible to maintain the shape of the polarizer without the first liquid crystal retardation film and the second liquid crystal retardation film being separated at room temperature.

In the evaluation of the flexibility of the polarizer described in further detail below, the second bonding layer 30 can prevent cracks or creases from being generated on each of the first liquid crystal retardation film and the second liquid crystal retardation film, thereby improving the flexibility of the polarizer. Therefore, the polarizer can improve the screen quality when used in a foldable light-emitting display.

The "flexibility evaluation" of a polarizer (a polarizer comprising a polarizer protective layer, a polarizer, a first bonding layer, a first retardation film, a second bonding layer, and a second retardation film stacked in the stated order) can be measured according to IEC-62715. Specifically, 80 μm thick polyethylene terephthalate (PET) films are attached to both surfaces of the polarizer via an acrylic adhesive, and then the polarizer is cut into a size of 6 cm × 4 cm (length × width, MD of the polarizer × TD of the polarizer) to prepare a sample. Next, the sample is mounted on a flexibility tester so that the PET film closest to the polarizer can be placed on the inner side of the polarizer during the flexibility test, and then the sample is repeatedly bent at 25°C under the conditions of a bending radius of 5 mm, a bending speed of 30 times/minute, and a bending angle of 180°, and the flexibility is evaluated by counting the number of bends until the first crack or crease appears in the first liquid crystal retardation film and/or the second liquid crystal retardation film. When the number of bends is 100,000 times or more, the polarizer can have excellent screen quality even when used in a foldable light-emitting display.

The second bonding layer 30 can be formed between the first liquid crystal retardation film 20 and the second liquid crystal retardation film 40, thereby reducing the influence on the polarization when the linear polarization light that has passed through the polarizer passes through the first liquid crystal retardation film 20, the second bonding layer 30 and the second liquid crystal retardation film 40 in sequence to be converted into circular polarization. Therefore, the second bonding layer can improve the circular polarization of the first liquid crystal retardation film and the second liquid crystal retardation film.

The second bonding layer 30 can improve the reliability of the polarizer even under high temperature conditions and/or high temperature/high humidity conditions. The first liquid crystal retardation film bonded to one surface of the polarizer has a thin thickness and cannot sufficiently suppress the change in polarization when the polarizer is kept under high temperature and/or high temperature/high humidity conditions. In contrast, the second bonding layer is formed on the other surface of the first liquid crystal retardation film, that is, on the surface of the first liquid crystal retardation film not bonded to the polarizer, thereby improving reliability by suppressing the change in polarization.

For example, according to Equation 1 or Equation 2, the polarizer according to the present invention may have a polarization change ΔPE ₁ or a polarization change ΔPE ₂ of 0.7% or less (e.g., 0 to 0.7%), respectively. For a more specific example, according to Equation 1 or Equation 2, the polarizer according to the present invention may have a polarization change ΔPE 1 or a polarization change ΔPE ₂ of 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, or 0.7%, _respectively : [Equation 1] ΔPE ₁ = |P1-P2|

Wherein P1 indicates the initial polarization degree (unit: %) measured on a sample obtained by cutting the polarizer into a size of 3 cm × 3 cm (length × width, MD of the polarizer × TD of the polarizer) and P2 indicates the polarization degree (unit: %) measured on the sample after the sample was placed at a constant temperature of 85°C for 500 hours; and [Equation 2] △PE ₂ = |P1-P3|

Wherein P1 indicates the initial polarization degree (unit: %) measured on a sample obtained by cutting the polarizer into a size of 3 cm × 3 cm (length × width, MD of polarizer × TD of polarizer) and P3 indicates the polarization degree (unit: %) measured on the sample after placing the sample under constant temperature/humidity conditions of 60°C and 95% for 500 hours.

The second bonding layer 30 may have a glass transition temperature of 70°C to 110°C. Within this range, the second bonding layer may have good peeling strength relative to the first liquid crystal retardation film and the second liquid crystal retardation film and may give the polarizer excellent reliability and flexibility. Preferably, the second bonding layer 30 may have a glass transition temperature higher than 70°C and 110°C or lower than 110°C, more preferably 85°C to 100°C.

The second bonding layer 30 may be formed of a bonding composition including an epoxy compound and a hydrophobic (meth)acrylate compound described in detail below.

Next, the bonding components will be described in more detail.

Epoxides

Epoxides may include alicyclic epoxides.

Herein, "alicyclic epoxy compound" may refer to a compound containing an epoxidized alicyclic group. For example, the alicyclic epoxy compound is a difunctional alicyclic epoxy compound and may include at least one of the following: 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl-3',4'-epoxy-6'-methylcyclohexanecarboxylate, bis(3,4-epoxy-6-methylcyclohexyl)adipate, biscyclohexyldiethoxy (3,4,3',4'-diethoxy-biscyclohexane) and 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate modified ε-caprolactone, but is not limited thereto.

The amount of the alicyclic epoxy compound can be 40 to 90 parts by weight, for example, 50 to 90 parts by weight, 50 to 80 parts by weight, relative to a total of 100 parts by weight of the epoxy compound and the (meth)acrylate compound. Within this range, excellent bonding between the liquid crystal retardation films can be obtained without reducing wettability due to an increase in the viscosity of the composition. In addition, the brittleness of the bonding layer caused by an excessive increase in the modulus does not occur, so there is no problem in terms of crack resistance and cutting characteristics of the polarizer.

In one embodiment, the amount of the alicyclic epoxy compound may be 40 parts by weight, 41 parts by weight, 42 parts by weight, 43 parts by weight, 44 parts by weight, 45 parts by weight, 46 parts by weight, 47 parts by weight, 48 parts by weight, 49 parts by weight, 50 parts by weight, 51 parts by weight, 52 parts by weight, 53 parts by weight, 54 parts by weight, 55 parts by weight, 56 parts by weight, 57 parts by weight, 58 parts by weight, 59 parts by weight, 60 parts by weight, 61 parts by weight, 62 parts by weight, 63 parts by weight, 64 parts by weight, 65 parts by weight, 66 parts by weight, 67 parts by weight, 68 parts by weight, 69 parts by weight, 70 parts by weight, 71 parts by weight, 72 parts by weight, 73 parts by weight, 74 parts by weight, 75 parts by weight, 76 parts by weight, 77 parts by weight, 78 parts by weight, 79 parts by weight, 80 parts by weight, 81 parts by weight, 82 parts by weight, 83 parts by weight, 84 parts by weight, 85 parts by weight, 86 parts by weight, 87 parts by weight, 88 parts by weight, 89 parts by weight, 90 parts by weight, 91 parts by weight, 92 parts by weight, 93 parts by weight, 94 parts by weight, 95 parts by weight, 96 parts by weight, 97 parts by weight, 98 parts by weight, 99 parts by weight, 100 parts by weight, 100 parts by weight, 62 parts by weight, 63 parts by weight, 64 parts by weight, 65 parts by weight, 66 parts by weight, 67 parts by weight, 68 parts by weight, 69 parts by weight, 70 parts by weight, 71 parts by weight, 72 parts by weight, 73 parts by weight, 74 parts by weight, 75 parts by weight, 76 parts by weight, 77 parts by weight, 78 parts by weight, 79 parts by weight, 80 parts by weight, 81 parts by weight, 82 parts by weight, 83 parts by weight, 84 parts by weight, 85 parts by weight, 86 parts by weight, 87 parts by weight, 88 parts by weight, 89 parts by weight or 90 parts by weight.

Epoxy compounds may further include glycidyl ethers containing aromatic groups.

Glycidyl ethers containing aromatic groups can provide a post-curing effect by dark reaction and improve the bonding with the liquid crystal delay film. In one embodiment, the above effects can be further improved by including alicyclic epoxy compounds and glycidyl ethers containing aromatic groups together.

The aromatic glycidyl ether may include a compound containing one or more glycidyl ether groups. "Glycidyl ether group" may refer to a portion of Formula 1: [Formula 1]

Where * is the connection point

The aromatic group-containing glycidyl ether may be a monofunctional glycidyl ether and may include an aromatic group and one glycidyl ether group. For example, the monofunctional glycidyl ether may include phenyl glycidyl ether, but is not limited thereto.

The aromatic group-containing glycidyl ether may be a difunctional diglycidyl ether and may include an aromatic group and two glycidyl ether groups. For example, the difunctional diglycidyl ether may include at least one of resorcinol diglycidyl ether and a (chloromethyl)ethylene oxide-containing 4,4'-(1-methylethylene)bisphenol polymer.

In one embodiment, the aromatic group-containing glycidyl ether may contain only monofunctional glycidyl ether.

In another embodiment, the aromatic-containing glycidyl ether may contain only difunctional diglycidyl ether.

In another embodiment, the aromatic group-containing glycidyl ether may include a mixture of monofunctional glycidyl ether and difunctional diglycidyl ether. For example, the aromatic group-containing glycidyl ether may include at least one of phenyl glycidyl ether and resorcinol diglycidyl ether.

The amount of the aromatic group-containing glycidyl ether may be 0 to 10 parts by weight, specifically 0.1 to 10 parts by weight, and more specifically 1 to 10 parts by weight, relative to a total of 100 parts by weight of the epoxy compound and the (meth)acrylate compound. Within this range, the initial curing speed is not slowed down, so that problems such as a decrease in initial bonding strength do not occur, and reliability and peeling strength may not be reduced even under high temperature and high humidity. In one embodiment, the amount of the aromatic glycidyl ether may be 0 parts by weight, 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight or 10 parts by weight.

The amount of the epoxy compound may be 35 to 90 parts by weight, specifically 35 to 85 parts by weight, 35 to 75 parts by weight, relative to 100 parts by weight of the total of the epoxy compound and the (meth)acrylate compound. Within this range, the bonding layer may have improved crack resistance due to an increase in its glass transition temperature. In one embodiment, the amount of the epoxy compound may be 35 parts by weight, 36 parts by weight, 37 parts by weight, 38 parts by weight, 39 parts by weight, 40 parts by weight, 41 parts by weight, 42 parts by weight, 43 parts by weight, 44 parts by weight, 45 parts by weight, 46 parts by weight, 47 parts by weight, 48 parts by weight, 49 parts by weight, 50 parts by weight, 51 parts by weight, 52 parts by weight, 53 parts by weight, 54 parts by weight, 55 parts by weight, 56 parts by weight, 57 parts by weight, 58 parts by weight, 59 parts by weight, 60 parts by weight, 61 parts by weight, , 62 parts by weight, 63 parts by weight, 64 parts by weight, 65 parts by weight, 66 parts by weight, 67 parts by weight, 68 parts by weight, 69 parts by weight, 70 parts by weight, 71 parts by weight, 72 parts by weight, 73 parts by weight, 74 parts by weight, 75 parts by weight, 76 parts by weight, 77 parts by weight, 78 parts by weight, 79 parts by weight, 80 parts by weight, 81 parts by weight, 82 parts by weight, 83 parts by weight, 84 parts by weight, 85 parts by weight, 86 parts by weight, 87 parts by weight, 88 parts by weight, 89 parts by weight or 90 parts by weight.

(Meth)acrylate compounds

(Meth)acrylate compounds can be polymerized by photo-radical initiators induced by light energy and can react stably by light energy without being inhibited by moisture.

The composition may include a (meth)acrylate compound that does not have any hydrophilic groups (such as hydroxyl groups, carboxyl groups, and the like). In this article, the (meth)acrylate compound that does not have any hydrophilic groups is referred to as a "hydrophobic (meth)acrylate compound".

By including a hydrophobic (meth)acrylate compound as a (meth)acrylate compound, the composition can improve the reliability of the polarizer, especially after the polarizer is placed under high temperature and high humidity for a long time.

In one embodiment, the composition may not contain a (meth)acrylate compound containing a hydrophilic group.

The hydrophobic (meth)acrylate compound may include a (meth)acrylate containing an unsubstituted linear or branched C ₆ to C ₂₀ alkyl group and a (meth)acrylate containing an unsubstituted aromatic group. If any of these is not included, the glass transition temperature of the bonding layer may exceed 110° C., and the second bonding layer does not meet the appropriate glass transition temperature range, resulting in a decrease in the peeling strength relative to the liquid crystal retardation film or a decrease in the flexibility or reliability of the polarizer. In one embodiment, the composition may include both a (meth)acrylate containing an unsubstituted linear or branched C ₆ to C ₂₀ alkyl group and a (meth)acrylate containing an aromatic group to ensure the effect of the present invention. Here, the "carbon number" of the alkyl group is a value that does not include the carbon number contained in the (meth)acrylate group.

The (meth)acrylate containing an unsubstituted linear or branched _C6 to _C20 alkyl group may include at least one of hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate. Preferably, the (meth)acrylate containing an unsubstituted linear or branched _C6 to _C20 alkyl group may include a (meth)acrylate containing an unsubstituted branched _C6 to _C20 alkyl group, more preferably a (meth)acrylate containing an unsubstituted branched _C8 to _C12 alkyl group, most preferably at least one of isodecyl (meth)acrylate and decyl (meth)acrylate.

The amount of the (meth)acrylate containing an unsubstituted linear or branched C ₆ to C ₂₀ alkyl group may be 1 to 30 parts by weight, such as 5 to 20 parts by weight, relative to 100 parts by weight of the total of the epoxy compound and the (meth)acrylate compound. Within this range, good peel strength of the bonding layer and reliability of the polarizer may be obtained even under high temperature and high humidity conditions. In one embodiment, the amount of the (meth)acrylate containing an unsubstituted linear or branched _C6 to _C20 alkyl group may be 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, 25 parts by weight, 26 parts by weight, 27 parts by weight, 28 parts by weight, 29 parts by weight, or 30 parts by weight.

The (meth)acrylate containing an aromatic group is a monofunctional (meth)acrylate or a multifunctional (meth)acrylate, and may include, for example, a (meth)acrylate containing a C ₆ to C ₂₀ aryloxy group (e.g., phenoxy group) containing a C ₁ to C ₅ alkyl group, a C ₁ to C ₅ alkylene group, or a C ₁ to C ₅ alkylene group. Preferably, the (meth)acrylate containing an aromatic group includes phenol ethoxylated (meth)acrylate.

The amount of the (meth)acrylate containing an aromatic group may be 1 to 20 parts by weight, for example, 5 to 20 parts by weight, relative to a total of 100 parts by weight of the epoxy compound and the (meth)acrylate compound. Within this range, the composition allows the bonding layer to have a glass transition temperature according to the present invention and can improve the initial bonding strength of the bonding layer. In one embodiment, the amount of the (meth)acrylate containing an aromatic group may be 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight or 20 parts by weight.

The amount of the (meth)acrylate compound (preferably a hydrophobic (meth)acrylate compound) may be 10 to 65 parts by weight, such as 15 to 65 parts by weight, or 25 to 65 parts by weight, relative to 100 parts by weight of the total of the epoxy compound and the (meth)acrylate compound. Within this range, even if shrinkage occurs during the curing of the bonding composition, the bonding layer can obtain good bonding strength and maintain good adhesion to the surface of the liquid crystal retardation film. In one embodiment, the amount of the hydrophobic (meth)acrylate compound may be 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, 25 parts by weight, 26 parts by weight, 27 parts by weight, 28 parts by weight, 29 parts by weight, 30 parts by weight, 31 parts by weight, 32 parts by weight, 33 parts by weight, 34 parts by weight, 35 parts by weight, 36 parts by weight, 37 parts by weight, 38 parts by weight, 39 parts by weight, 40 parts by weight, 41 parts by weight, 42 parts by weight, 43 parts by weight, 44 parts by weight, 45 parts by weight, 46 parts by weight, 47 parts by weight, 48 parts by weight, 49 parts by weight, 50 parts by weight, 51 parts by weight, 52 parts by weight, 53 parts by weight, 54 parts by weight, 55 parts by weight, 56 parts by weight, 57 parts by weight, 58 parts by weight, 59 parts by weight, 60 parts by weight, 61 parts by weight, 62 parts by weight, 63 parts by weight, 64 parts by weight or 65 parts by weight.

Initiator

The initiator may comprise a mixture of a photocationic ion initiator and a photoradical initiator.

The photocationic initiator may include a typical photocationic initiator capable of performing a photocuring reaction.

The photocatalytic ion initiator may include an onium salt of an onium ion including a cation and an anion. Examples of the onium ion may include diaryl iodoniums such as diphenyl iodonium, 4-methoxydiphenyl iodonium, bis(4-methylphenyl)iodonium, bis(4-tert-butylphenyl)iodonium, bis(dodecylphenyl)iodonium, and (4-methylphenyl)[(4-(2-methylpropyl)phenyl)iodonium; triaryl coroniums such as triphenyl coronium and diphenyl-4-thiophenoxyphenyl; bis(4-(diphenyldihydrosulfanyl)phenyl)sulfide, bis(4-(di(4-(2-hydroxyethyl)phenyl)dihydrosulfanyl)phenyl)sulfide, (η5-2,4-cyclopentadien-1-yl)[(1,2,3,4,5,6-η)-(1-methylethyl)phenyl]iron( ¹⁺ ), and the like. Examples of the anion may include tetrafluoroborate ( _BF4- ), _{hexafluorophosphate} ( _PF6- ⁾ , hexafluoroantimonate (SbF6- ⁾ , _{hexafluoroarsenate} ( ^ASF6- ), hexachloroantimonate ( _SbCl6- ⁾ , and the like.

The amount of the photocationic initiator may be 1 to 10 parts by weight, for example 2 to 10 parts by weight, relative to a total of 100 parts by weight of the epoxy compound and the (meth)acrylate compound. Within this range, the composition for the bonding layer can be fully cured without suffering from a reduction in peeling strength, leakage of the photocationic initiator, and the like. In one embodiment, the amount of the photocationic initiator may be 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, or 10 parts by weight.

The photoradical initiator can generate a small amount of free radicals after being irradiated with light to accelerate the curing reaction. The photoradical initiator can include phenyl ketone, phosphorus, triazine, acetophenone, benzophenone, thioxanone, benzoin, oxime compounds and mixtures thereof. In some embodiments, the photoradical initiator can include phenyl ketone compounds or mixtures thereof.

The amount of the photo radical initiator may be 0.5 to 10 parts by weight, for example 0.5 to 6 parts by weight, relative to a total of 100 parts by weight of the epoxy compound and the (meth) acrylate compound. Within this range, the (meth) acrylate compound can be fully cured under light intensity conditions for processing, and the reactivity of the photo cation initiator can be improved. In one embodiment, the amount of the photo radical initiator may be 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight or 10 parts by weight.

The composition for the second bonding layer can be prepared by mixing an epoxy compound, a (meth)acrylate compound, a photocation initiator, and a photoradical initiator. The composition for the second bonding layer can be solvent-free or can further contain a solvent to improve applicability (applicability).

Within the scope of not reducing the effect of the present invention, the composition used for the second bonding layer may further include an antioxidant, a UV absorber, an additive for imparting conductivity (such as ion conductors and conductive metal oxide particles), an additive for imparting light diffusion, a viscosity regulator, and the like.

The composition for the second bonding layer can be photocured by irradiating light having a UVA wavelength under conditions of 50 mJ/cm2 to 400 mJ/cm2, preferably 60 mJ/cm2 to 300 mJ/cm2 to form the second bonding layer.

The thickness of the second bonding layer 30 may be 0.1 μm to 30 μm, for example 1 μm to 10 μm. Within this range, the second bonding layer may have a suitable thickness to ensure the peeling strength relative to each of the first liquid crystal retardation film and the second liquid crystal retardation film and may be used in a polarizer.

First liquid crystal retardation film and second liquid crystal retardation film

The first liquid crystal retardation film 20 and the second liquid crystal retardation film 40 can improve the screen quality by preventing the reflection of external light through circular polarization of linear polarization that has passed through the polarizer.

In one embodiment, the in-plane retardation (Re) of the first liquid crystal retardation film at a wavelength of 550 nm may be 100 nm to 220 nm, specifically 100 nm to 180 nm. For example, the first liquid crystal retardation film may be a λ/4 retardation film. Here, the in-plane retardation (Re) of the second liquid crystal retardation film at a wavelength of 550 nm may be 225 nm to 350 nm, specifically 225 nm to 300 nm. For example, the second liquid crystal retardation film may be a λ/2 retardation film.

In another embodiment, the in-plane retardation (Re) of the first liquid crystal retardation film at a wavelength of 550 nm may be 225 nm to 350 nm, specifically 225 nm to 300 nm. For example, the first liquid crystal retardation film may be a λ/2 retardation film. Here, the in-plane retardation (Re) of the second liquid crystal retardation film at a wavelength of 550 nm may be 100 nm to 220 nm, specifically 100 nm to 180 nm. For example, the second liquid crystal retardation film may be a λ/4 retardation film.

The first liquid crystal retardation film and the second liquid crystal retardation film may each have the same or different thicknesses. For example, the thickness of each of the first liquid crystal retardation film and the second liquid crystal retardation film may be 0.1 micrometer to 30 micrometers, specifically 1 micrometer to 10 micrometers. Within this thickness range, the polarizer may have a thinner thickness and may achieve a target retardation value.

In one embodiment, each of the first liquid crystal retardation film and the second liquid crystal retardation film may be a liquid crystal retardation layer composed of a single layer. For each of the first liquid crystal retardation film and the second liquid crystal retardation film composed of a liquid crystal retardation layer, the liquid crystal retardation layer is composed of a single layer, thereby being able to reduce the thickness of the polarizer to a greater extent.

The liquid crystal retardation layer may be formed of a composition including at least one of a (meth) acrylic liquid crystal compound containing an alicyclic group or a (meth) acrylic liquid crystal compound containing an aromatic group. The liquid crystal retardation layer may further include additives such as a leveling agent, a polymerization initiator, an alignment aid, a thermal stabilizer, a lubricant, a plasticizer, an antistatic agent, and the like.

In another embodiment, each of the first liquid crystal retardation film and the second liquid crystal retardation film may include a base film and a liquid crystal retardation layer formed on the base film. Each of the first liquid crystal retardation film and the second liquid crystal retardation film may be formed by coating a composition for forming a liquid crystal retardation layer on the base film and then curing it.

Polarizer

The polarizer 10 is formed on the first liquid crystal retardation film to polarize internal light or external light. For the first liquid crystal retardation film composed of a liquid crystal retardation layer, a composition for forming the liquid crystal retardation layer is applied on the polarizer and then cured, whereby the first liquid crystal retardation film can be directly formed on the polarizer.

The polarizer 10 may include a polyvinyl alcohol-based polarizer formed by dyeing a polyvinyl alcohol film using iodine and the like. For example, the polyvinyl alcohol-based polarizer may be manufactured by dyeing a polyvinyl alcohol film using iodine or a dichroic dye and then stretching the dyed film in a certain direction. Specifically, the polyvinyl alcohol-based polarizer is manufactured by swelling, dyeing, and stretching. The methods used for each of these processes are well known to those of ordinary skill in the art. The thickness of the polarizer may be 1 micrometer to 50 micrometers. Within this range, the polarizer may be used in a light-emitting display.

First bonding layer

The first bonding layer 50 is formed between the polarizer 10 and the first liquid crystal retardation film 20 to bond the polarizer to the first liquid crystal retardation film. Here, the first bonding layer may be formed of the composition used for the second bonding layer described above.

The thickness of the first bonding layer 50 may be 0.1 micrometer to 30 micrometers, for example, 1 micrometer to 10 micrometers. Within this thickness range, the first bonding layer can be used in a light-emitting display.

The first bonding layer 50 may have a glass transition temperature that is equal to or different from the glass transition temperature of the second bonding layer. In one embodiment, the first bonding layer 50 may have a glass transition temperature of 70°C to 110°C. Within this range, the first bonding layer may have good peeling strength relative to each of the first liquid crystal retardation film and the polarizer and may give the polarizer excellent reliability and flexibility. Preferably, the first bonding layer 50 may have a glass transition temperature greater than 70°C and 100°C or less than 100°C, more preferably 85°C to 100°C.

Although not shown in FIG. 1 , an adhesive film is further formed on the lower surface of the second liquid crystal retardation film on which the bonding layer is not formed, that is, on the surface of the second liquid crystal retardation film, to attach the polarizer to the light-emitting device (e.g., an organic light-emitting device panel).

Referring again to FIG. 1 , the polarizer includes a first bonding layer. In one embodiment, when the first liquid crystal retardation film is a liquid crystal retardation layer, the first liquid crystal retardation film can be directly formed on the polarizer without the first bonding layer.

Next, a polarizer according to another embodiment will be described with reference to FIG. 2.

Referring to FIG. 2 , the polarizer according to this embodiment includes a polarizer 10; a protective layer 60 formed on the upper surface of the polarizer 10; and a first bonding layer 50, a first liquid crystal retardation film 20, a second bonding layer 30, and a second liquid crystal retardation film 40 sequentially formed on the lower surface of the polarizer 10. The polarizer according to this embodiment is substantially the same as the polarizer of FIG. 1 except that the protective layer 60 is further formed on the upper surface of the polarizer 10.

The protective layer 60 is formed on the upper surface of the polarizer to support the polarizer. In addition, when the first liquid crystal retardation film is formed on the lower surface of the polarizer, the protective layer formed on the upper surface of the polarizer allows the first liquid crystal retardation film to be directly formed on the polarizer without the first bonding layer. The protective layer may include at least one of an optically transparent protective film and an optically transparent protective coating.

When the protective layer is a protective film type, the protective layer 60 may include a protective film formed of an optically transparent resin. The protective film may be formed by melting and extruding the resin. The resin may be further stretched as needed. The optically transparent resin may include at least one selected from the following: a cellulose ester resin including triacetyl cellulose, a cyclic polyolefin resin including a cyclic olefin polymer (COP), a polycarbonate resin, a polyester resin including polyethylene terephthalate (PET), a polyether resin, a polysulfone resin, a polyamide resin, a polyimide resin, a non-cyclic polyolefin resin, a polyacrylate resin including poly(methyl methacrylate), a polyvinyl alcohol resin, a polyvinyl chloride resin, and a polyvinylidene chloride resin. Preferably, the protective film is a film formed of a cyclic polyolefin resin containing a cycloolefin polymer (COP).

When the protective layer is a protective coating type, the protective layer can improve adhesion to the polarizer, transparency, mechanical strength, thermal stability, moisture resistance, and durability. In one embodiment, the protective coating used for the protective layer can be formed of an actinic radiation curable resin composition containing an actinic radiation curable compound and a polymerization initiator.

The actinic radiation curable compound may include at least one of a cationic polymerizable curable compound, a free radical polymerizable curable compound, a urethane resin, and a silicone resin. The cationic polymerizable curable compound may be an epoxy compound having at least one epoxy group therein, or an oxycyclobutane compound having at least one oxycyclobutane ring therein. The free radical polymerizable curable compound may be a (meth)acrylic compound having at least one (meth)acryloyloxy group therein.

The thickness of the protective layer 60 may be 5 micrometers to 200 micrometers, specifically 30 micrometers to 120 micrometers. The thickness of the protective film type protective layer may be 30 micrometers to 100 micrometers, and the thickness of the protective coating type protective layer may be 5 micrometers to 50 micrometers. Within this thickness range, the protective layer can be used in a light-emitting display.

Although not shown in FIG. 2 , the polarizer may further include a functional coating on the upper surface of the protective layer 60 , such as a hard coating layer, an anti-fingerprint layer, and an anti-reflection layer.

Although not shown in FIG. 2 , when the protective layer 60 is a protective film type, the polarizer may further include a third bonding layer between the protective layer and the polarizer. The third bonding layer may be formed of a typical bonding agent used for polarizing plates (e.g., a water-based bonding agent including a polyvinyl alcohol resin as an adhesive resin, a photocurable bonding agent, and a pressure-sensitive bonding agent).

Next, another embodiment of the polarizer of the present invention will be described.

According to another embodiment, the polarizer is substantially the same as the above-described embodiment shown in FIG. 1 , except that at least one of the first bonding layer 50 and the second bonding layer 30 is formed of a composition in which a silane coupling agent is further added to the above-described bonding composition.

When at least one of the first bonding layer 50 and the second bonding layer 30 is formed by a composition further comprising a silane coupling agent, the reliability of the polarizer under high temperature and/or high temperature and high humidity can be further improved.

The silane coupling agent may be a compound having a siloxyalkyl group (-*Si( ^OR1 ) _n ( ^R2 ) _3-n , wherein n is an integer of 1 to 3, ^R1 is a _C1 to C5 _alkyl group, and ^R2 is a hydroxyl group, a halogen group, or a _C1 to _C4 alkyl group) and may include any suitable silane coupling agent available in the art. In one embodiment, the silane coupling agent may include at least one of the following: an epoxy-containing silane coupling agent, such as 3-glyceryloxypropyltrimethoxysilane, glyceryloxypropylmethyldimethoxysilane, etc.; an unsaturated group-containing silane coupling agent, such as vinyltrimethoxysilane, etc.; a butyl group-containing silane coupling agent, such as butylpropyltrimethoxysilane, etc.

Relative to a total of 100 parts by weight of the epoxy compound and the (meth)acrylate compound, the amount of the silane coupling agent may be 0.01 parts by weight to 10 parts by weight, for example, 0.1 parts by weight to 5 parts by weight. Within this range, the polarizer may have improved reliability under high temperature and high humidity conditions. In one embodiment, the amount of the silane coupling agent may be 0.01 parts by weight, 0.05 parts by weight, 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight or 10 parts by weight.

A light-emitting display according to an embodiment may include a polarizer according to the present invention. For example, the light-emitting display may include an organic light-emitting display, but is not limited thereto. Although the light-emitting display according to the present invention may be applicable to a non-foldable light-emitting display, the light-emitting display may exhibit good flexibility when used in a foldable light-emitting display.

Next, the present invention will be described in more detail with reference to some examples. However, it should be noted that these examples are provided for illustration only and should not be interpreted as limiting the present invention in any way.

Example 1

A polyvinyl alcohol film (saponification degree: 99.5%, polymerization degree: 2,000, thickness: 60 microns) was immersed in a 0.3% iodine aqueous solution for dyeing and then stretched to 5.0 times in the machine direction (MD). The stretched polyvinyl alcohol film was immersed in a 3% boric acid solution and a 2% potassium iodide aqueous solution for color correction and then dried at 50°C for 4 minutes to prepare a polarizer (thickness: 23 microns).

As the first liquid crystal retardation film, a liquid crystal coated retardation film (Fuji Film Co., Ltd. QL AA 328, cyclic (aromatic) acrylic liquid crystal retardation layer, Re: 234 nm at a wavelength of 550 nm) was used. Both surfaces of the liquid crystal coated retardation film were subjected to a corona treatment of 250 mJ/cm2.

As the second liquid crystal retardation film, a liquid crystal coated retardation film (Fuji Film Co., Ltd., QA AB 318, cyclic (aromatic) acrylic liquid crystal retardation layer, Re: 116 nm at a wavelength of 550 nm) was used. Both surfaces of the liquid crystal coated retardation film were subjected to a corona treatment of 250 mJ/cm2.

Step (1): Prepare pre-polarizer

A pre-polarizer laminated in order of a protective layer, a composition for a bonding layer (third bonding layer), a polarizer, a composition for a bonding layer (first bonding layer), and an unsaponified triacetylcellulose (TAC) film was prepared under conditions of 22°C to 25°C and 20% to 60% RH.

As a protective layer, a cyclic olefin polymer (COP) resin film (thickness: 30 μm, transparent protective film) was used. One surface of the cyclic olefin resin film was subjected to a corona treatment of 250 mJ/cm2.

The third bonding layer is formed of a composition including a PVA-based water-based bonding agent, the bonding agent including 100 parts by weight of water, 3 parts by weight of polyvinyl alcohol resin (product name: Z320, Nippon Synthetic Chemical Industry Co., Ltd.) and 3 parts by weight of glyoxal (TCL Corporation). The composition for the third bonding layer is applied to one surface of the protective layer and then the polarizer layer is pressed thereon, followed by heat curing at 50°C for 1 minute and at 85°C for 2 minutes in a drying oven to form the third bonding layer.

Next, the composition for the first bonding layer is applied to the other surface of the polarizer, and then the unsaponified triacetyl cellulose (TAC) film layer is pressed thereon. According to the composition shown in Table 1, the composition for the first bonding layer is prepared by mixing an epoxy compound, a (meth)acrylate compound, and an initiator.

Step (2): Prepare a laminate of the first liquid crystal retardation film-the second bonding layer-the second liquid crystal retardation film

A laminate of the first liquid crystal retardation film-the second bonding layer-the second liquid crystal retardation film was prepared under conditions of 22°C to 25°C and 20% RH to 60% RH.

A composition for a second bonding layer prepared by mixing an epoxy compound, a (meth)acrylate compound and an initiator according to the composition shown in Table 1 is applied to one side of the first liquid crystal retardation film, and then the second liquid crystal retardation film is stacked thereon, and then the first liquid crystal retardation film is exposed to obtain a laminate.

Step (3): Prepare polarizer

Polarizers were prepared at 22°C to 25°C and 20% RH to 60% RH.

The unsaponified TAC film is separated and removed from the pre-polarizer prepared in step (1). The first bonding layer of the pre-polarizer is laminated to contact the first liquid crystal retardation film of the laminate having the structure of the first liquid crystal retardation film-the second bonding layer-the second liquid crystal retardation film prepared in step (2), and then a metal halide lamp (LICHTZEN Co., Ltd.) is used to irradiate the first liquid crystal retardation film. Co., Ltd)) exposes the second liquid crystal retardation film to obtain a polarizer in which a protective layer, a third bonding layer (thickness: 0.1 micron, PVA-type water-based bonding layer), a polarizer, a first bonding layer (thickness: 3 microns, the UV-curable bonding layer of the present invention), a first liquid crystal retardation film (Re: 234 nanometers), a second bonding layer (thickness: 3 microns, the UV-curable bonding layer of the present invention) and a second liquid crystal retardation film (Re: 116 nanometers) are sequentially stacked.

For the measurement of the peeling strength, UV irradiation was performed using a light shielding member attached to a portion of the lower surface of the second liquid crystal retardation film.

Example 2 to Example 6

Each polarizer was prepared in the same manner as in Example 1, except that the components and/or contents of the compositions used for the second bonding layer and the first bonding layer were changed as shown in Table 1.

Comparison Example 1 to Comparison Example 4

Each polarizer was prepared in the same manner as in Example 1, except that the components and/or contents of the compositions used for the second bonding layer and the first bonding layer were changed as shown in Table 1.

The components and contents (unit: weight parts) of the compositions used for the first bonding layer and the second bonding layer in the examples and comparative examples are shown in Table 1. Each component in Table 1 is expressed as a solid content excluding solvent. In Table 1, "-" means that the component is not included.

Glass transition temperature (Tg) of the second bonding layer (or first bonding layer) (unit: °C):

The composition for the second bonding layer was coated on a processing film (PET film) to a predetermined thickness and cured by UV radiation, thereby preparing a sample having a second bonding layer with a thickness of 5 to 10 microns. For the prepared sample, a dynamic mechanical analyzer (DMA) was used to measure tanδ while increasing the temperature from 0°C at a heating rate of 5°C/min. Among the tanδ values according to temperature, the temperature that provides the highest tanδ is defined as the glass transition temperature and is shown in Table 1 below. The first bonding layer is formed of the same composition as the composition for the second bonding layer, so the first bonding layer also has the same glass transition temperature as in Table 1 below.

A: 3,4-Epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (CELLOXIDE 2021P, DAICEL CORPORATION)

B: Resorcinol diglycidyl ether (EX-201, NAGASE CHEMTEX)

C: Phenyl glycidyl ether (EX-141, Nagase Chemical Co., Ltd.)

D: 4-Hydroxybutyl acrylate (OSAKA ORGANIC)

E: Isodecyl acrylate (M-130, MIWON SPECIALTY CHEMICAL)

F: Phenol (EO) acrylate (M-140, Miwon Specialty Chemicals Co., Ltd.)

G: Diphenyl-4-(phenylthio)phenylcopperthionium hexafluorophosphate (CPI-100P, SAN-APRO)

H: 1-Hydroxycyclohexylphenylketone (IRGACURE 184, BASF)

I: 3-Glyceryloxypropyltrimethoxysilane (SHIN-ETSU CHEMICAL CO.)

The physical properties of the polarizers prepared in the examples and comparison examples were evaluated by the following method, and the results are shown in Table 2.

(1) Peel strength: Each of the polarizers prepared in the examples and comparative examples was placed at 25°C for 2 minutes. Then, the polarizer was cut into a size of 25 mm × 150 mm (width × length) including a light shielding member (3 cm), and a double-sided adhesive film was attached to the lower surface of the second liquid crystal retardation film to fix the polarizer to a tensile tester (texture analyzer). By opening the light shielding member of the polarizer, the first liquid crystal retardation film of the polarizer was fixed to the fixture of the texture analyzer. Then, the polarizer was placed at 25°C for 72 hours. Thereafter, when the first liquid crystal retardation film and the second liquid crystal retardation film were peeled off at 25°C under the conditions of a peeling speed of 300 mm/min and a peeling angle of 90°, the peeling strength was measured and defined as the peeling strength:

The peel strength less than 50 gf/25 mm is rated as x,

The peeling strength of 50 gf/25 mm or greater than 50 gf/25 mm and less than 100 gf/25 mm is rated as △,

The peel strength of 100 gf/25 mm or more is rated as o.

(2) Reliability (unit: %): Each of the polarizers prepared in the examples and comparative examples was cut into a sample having a size of 3 cm × 3 cm (length × width, MD of the polarizer × TD of the polarizer). The polarization degree was measured with the second liquid crystal retardation film of the sample positioned to face the light-emitting surface of V-7100 (JASCO).

For the prepared samples, measure the initial polarization (P1).

The polarization degree (P2, P3) was measured by the same method as mentioned above when the prepared samples were placed in a heating chamber (constant temperature of 85°C, high temperature) or a humid heating chamber (constant temperature of 60°C and constant humidity of 95%, high temperature/high humidity) for 500 hours. The polarization degree change was calculated according to Equation 1 and Equation 2.

(3) Flexibility: A 80 μm thick polyethylene terephthalate (PET) film was attached to one surface of the polarizer via an acrylic adhesive and an 80 μm PET film was attached to the other surface via an acrylic adhesive, and then the polarizer was cut into a size of 6 cm × 4 cm (length × width, length: MD of the polarizer, width: TD of the polarizer), thereby preparing a sample having a structure of PET film/polarizer/PET film.

According to IEC-62715, the sample is mounted on the flexibility tester so that the PET film closest to the polarizer can be placed on the inner side of the polarizer during the flexibility test. The sample is then bent repeatedly at 25°C under the conditions of a bending radius of 5 mm, a bending speed of 30 times/min, and a bending angle of 180°. The flexibility is evaluated by counting the number of bends until the first crack or crease appears in the first liquid crystal retardation film and/or the second liquid crystal retardation film. Flexibility is evaluated according to the following criteria:

○: The number of bends is 100,000 times or more

△: The number of bends is 50,000 times or more and less than 100,000 times

X: The number of bends is less than 50,000 times

(4) Curability: In step (2), the laminate was left for 24 hours after exposure, and then the bonded parts were separated to evaluate the curability.

○: The liquid crystal retardation film is easy to separate.

X: The bonding layer is not cured or sticks to your hands.

As shown in Table 2, the polarizer for a light-emitting display according to the present invention exhibits good peeling strength of the bonding layer relative to the liquid crystal retardation film and shows good reliability and flexibility.

On the other hand, the polarizer of the comparative example having the first bonding layer or the second bonding layer deviating from the present invention cannot achieve the object of the present invention.

It should be understood that although some example embodiments have been described herein, various modifications, changes, alterations, and equivalent embodiments may be made by those skilled in the art without departing from the spirit and scope of the present invention.

10: Polarizer

20: First liquid crystal retardation film

30: Second bonding layer

40: Second liquid crystal retardation film

50: First bonding layer

Claims (14)

A polarizer for a light-emitting display, comprising: a polarizer; and a first bonding layer, a first liquid crystal retardation film, a second bonding layer, and a second liquid crystal retardation film, which are sequentially stacked on the surface of the polarizer, wherein the polarizer has a polarization degree change ΔPE ₁ of 0.7% or less according to equation 1 and a polarization degree change ΔPE 2 of 0.7% or less according to equation ₂ : [Equation 1] ΔPE ₁ = |P1-P2|, wherein P1 indicates a polarization degree change along the longitudinal direction (machine direction, MD) of the polarizer and the transverse direction (transverse direction, MD) of the polarizer. direction, TD) is the initial polarization measured on a sample with a length of 3 cm and a width of 3 cm obtained by cutting the polarizer, and P2 indicates the polarization measured on the sample after the sample is placed at a constant temperature of 85° C. for 500 hours; and [Equation 2] ΔPE ₂ =｜P1-P3｜, wherein P1 indicates the initial polarization measured on a sample with a length of 3 cm and a width of 3 cm obtained by cutting the polarizer along the MD of the polarizer and the TD of the polarizer, and P3 indicates the polarization measured on the sample with a length of 3 cm and a width of 3 cm after the sample is placed under constant temperature and humidity conditions of 60° C. and 95% for 500 hours, and the unit of the polarization is %, wherein the second bonding layer has a glass transition temperature of 85° C. to 100° C., wherein the first bonding layer and the second bonding layer are formed of a composition including an epoxy compound and a (meth)acrylate compound, wherein the (meth)acrylate compound includes a hydrophobic (meth)acrylate compound, wherein the hydrophobic (meth)acrylate compound includes a straight chain or branched chain C ₆ to C 6 containing unsubstituted The invention relates to a liquid crystal retardation film comprising a (meth)acrylate containing an alicyclic group and a (meth)acrylate containing an unsubstituted aromatic group, wherein the amount of the (meth)acrylate containing an unsubstituted aromatic group is ₁ to 20 parts by weight based on 100 parts by weight of the total of the epoxy compound and the (meth)acrylate compound, wherein each of the first liquid crystal retardation film and the second liquid crystal retardation film is formed of a composition including at least one of a (meth)acrylic liquid crystal compound containing an alicyclic group and a (meth)acrylic liquid crystal compound containing an aromatic group. A polarizer for a light-emitting display as described in claim 1, wherein the second bonding layer is directly formed on each of the first liquid crystal retardation film and the second liquid crystal retardation film. The polarizer for a light-emitting display as described in claim 1, wherein the (meth)acrylate containing an unsubstituted linear or branched _C6 to _C20 alkyl group includes at least one of isodecyl (meth)acrylate and decyl (meth)acrylate. A polarizer for a light-emitting display as described in claim 1, wherein the epoxy compound includes an alicyclic epoxy compound. The polarizer for a light-emitting display as described in claim 4, wherein the epoxy compound further includes a glycidyl ether containing an aromatic group. The polarizer for a light-emitting display as described in claim 5, wherein the aromatic-containing glycidyl ether includes at least one of phenyl glycidyl ether and resorcinol diglycidyl ether. A polarizer for a light-emitting display as described in claim 1, wherein the composition does not contain a (meth)acrylate compound containing a hydrophilic group. The polarizer for a light-emitting display as described in claim 1, wherein the amount of the (meth)acrylate compound is 25 to 65 parts by weight based on a total of 100 parts by weight of the epoxy compound and the (meth)acrylate compound. The polarizer for a luminescent display as described in claim 1, wherein the composition further includes a photocation ion initiator and a photoradical initiator. The polarizer for a light-emitting display as described in claim 9, wherein the composition comprises: 35 to 90 parts by weight of the epoxy compound, 10 to 65 parts by weight of the (meth)acrylate compound, 1 to 10 parts by weight of the photo-cationic ion initiator based on a total of 100 parts by weight of the epoxy compound and the (meth)acrylate compound, and 0.5 to 10 parts by weight of the photo-radical initiator based on a total of 100 parts by weight of the epoxy compound and the (meth)acrylate compound. A polarizer for a light-emitting display as described in claim 1, wherein the first bonding layer has a glass transition temperature of 70°C to 110°C. The polarizer for a light-emitting display as described in claim 1 further includes a protective layer on another surface of the polarizer. A light-emitting display, comprising a polarizer for a light-emitting display as described in any one of claim 1 to claim 12. A light-emitting display as described in claim 13, wherein the light-emitting display includes a foldable light-emitting display.