KR102480477B1 - Reflective polarizing film, and backlight assembly and display device including the same - Google Patents

Abstract

A reflective polarizing film, and a backlight assembly and display device including the same are disclosed. The disclosed reflective polarizing film includes a substrate; and a coating layer on at least one surface of the substrate, wherein the coating layer includes at least one particle having a K-value of 145 to 175, the particle has a diameter of 1 to 20 μm, and an average diameter of the particle Particles with a size of ±50% may be polydisperse particles of 90% or more of the total particle volume.

Description

Reflective polarizing film, and backlight assembly and display device including the same

It relates to a reflective polarizing film, and a backlight assembly and display device including the same.

A display device, for example, a liquid crystal display, is currently being used in laptop computers, personal computer monitors, liquid crystal TVs, automobiles, and airplanes. An optical film used in a liquid crystal display cannot be said to have high utilization efficiency of light emitted from a backlight. This is because more than 50% of the light emitted from the backlight is absorbed by the polarizing film. In order to increase the efficiency of backlight use in a liquid crystal display, a reflective polarizing film is installed between the optical cavity and the liquid crystal assembly.

Since the reflective polarizing film is located at the top of the optical cavity, it must have shielding ability and at the same time include a particle coating layer within a range that does not deteriorate luminance performance.

In general, however, the particles used in the coating layer are satisfactory in shielding, light transmittance, and low refractive performance, but may cause friction with the prism due to their strong hardness. This has a problem of reducing luminance as well as generating black spots on the liquid crystal display.

Therefore, there is still a need for a reflective polarizing film having a certain level of shielding ability and not causing splitting with the prism.

One aspect is provided with a reflective polarizing film capable of preventing friction with a prism while having excellent light transmittance and luminance.

Another aspect is provided with a backlight assembly including the reflective polarizing film.

Another aspect is provided with a liquid crystal display device including the reflective polarizing film.

According to one aspect,

write; and

Including; a coating layer on at least one surface of the substrate,

The coating layer includes at least one particle having a K-value of 145 to 175,

The diameter of the particles is 1 to 20 μm

A reflective polarizing film is provided in which the particles having a size of ±50% of the average diameter of the particles are polydisperse particles of 90% or more of the total particle volume.

The refractive index of the particles may be 1.00 to 1.50.

The light transmittance of the particles represented by Equation 1 below may be 85% or more:

<Equation 1>

Particle light transmittance (%) = [{(light amount of transmitted light + light amount of refracted light) / light amount of incident light} x 100]

The particles may include nylon, polyethylene terephthalate (PET), or a combination thereof.

The coating layer may further include a binder.

The content of the particles may be 0.2% to 8.0% by weight based on 100% by weight of the entire coating layer.

The substrate is polyethylene terephthalate (PET), polyethylene naphthalate (PEN), co-polyethylene naphthalate (co-PEN), polycarbonate (PC), polystyrene (PS), polymethyl methacrylate (PMMA), polybutylene Terephthalate (PBT), Polypropylene (PP), Polyethylene (PE), Acrylonitrile Butadiene Styrene (ABS), Polyurethane (PU), Polyimide (PI) Polyvinyl Chloride (PVC), StyreneAcrylonitrile (SAN) ) resin, ethylene vinyl acetate (EVA) resin, polyamide (PA), polyacetal (POM), phenol resin, epoxy (EP) resin, urea (UF) resin, melanin (MF) resin, polyester (UP), It may be a silicone (SI) resin, a cycloolefin polymer (COP), or a combination thereof.

The luminance of the reflective polarizing film may be 85% or more.

The reflective polarizing film may further include a skin layer between the substrate and the coating layer.

The reflective polarizing film may have a thickness of 125 μm to 350 μm.

According to other aspects,

A backlight assembly including the above-described reflective polarizing film is provided.

According to another aspect,

A liquid crystal display device including the above-described reflective polarizing film is provided.

The reflective polarizing film according to an embodiment includes a coating layer on at least one surface of a substrate, and the coating layer includes at least one particle having a K-value of 145 to 175, and the diameter of the particle is 1 to 20 μm Since the particles having a size of ±50% of the average diameter of the particles are polydisperse particles of 90% or more of the total particle volume, friction with the prism can be prevented while having excellent light transmittance and brightness.

1A is a schematic cross-sectional view of a reflective polarizing film according to an embodiment.
Figure 1b is a schematic cross-sectional view of a reflective polarizing film according to another embodiment.
2a to 2d show the coating layer of the reflective polarizing film prepared in Examples 1 to 2 and Comparative Examples 1 to 2, respectively, in contact with the prism, and a weight having a load of 200 g was raised and rubbed left and right 100 times using a force of 20 N. Here is a picture of the top of the prism.
3a to 3d are particle size distribution diagrams of particles included in the coating layer of the reflective polarizing film prepared in Examples 1 and 2 and Comparative Examples 1 and 2, respectively.

A reflective polarizing film, a backlight assembly and a display device including the same will be described in detail with reference to the embodiments and drawings of the present invention. These examples are only presented as examples to explain the present invention in more detail, and it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples. .

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control.

Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

In this specification, the expression "at least one side" in front of a component means to include both "one side" or "both sides" of the component. The expression “at least one”, “one or more”, or “one or more” in front of elements herein means that they can complement the entire list of elements and can complement individual elements in the description. I never do that.

The term “and/or” as used herein is meant to include any and all combinations of one or more of the items listed in relation to it. The term "or" as used herein means "and/or".

In this specification, the term "include" is used to indicate that other components may be added or/or intervened, not excluded, unless otherwise stated. The term "combination of these" is used herein to denote a mixture or alloy of two or more of the foregoing components, or the like. In this specification, the term "~ resin" is used to denote a broad concept including "~ resin" or/and "~ resin derivative".

In the present specification, unless otherwise specified, the unit "parts by weight" means the weight ratio between each component.

In this specification, when an element is referred to as being disposed "on" another element, one element may be directly disposed on the other element, or there may be intervening elements between the elements. It can be. On the other hand, when an element is referred to as being placed “directly on” another element, intervening elements may not exist.

In general, in a liquid crystal display, a liquid crystal part has an optical state that is changed as an electric field generated by applying a voltage to two electrodes moves the liquid crystal part. This process displays an image by using information-loaded 'pixels' polarized light in a specific direction. For this reason, liquid crystal displays include a front optical film and a rear optical film for inducing polarization. Since the optical film used in the liquid crystal display cannot be said to have high efficiency in the use of light emitted from the backlight, a reflective polarizing film is installed between the optical cavity and the liquid crystal assembly.

However, particles included in the coating layer disposed on the top surface of the reflective polarizing film have strong hardness in addition to shielding properties, light transmittance, and low refractive performance, causing friction with the prism, which may cause black spots on the liquid crystal display and decrease in luminance. there is.

In order to solve this problem, the inventors of the present invention propose the following reflective polarizing film, and a backlight assembly and display device including the same.

A reflective polarizing film according to an embodiment includes a substrate; and a coating layer on at least one surface of the substrate, wherein the coating layer includes at least one particle having a K-value of 145 to 175, the particle has a diameter of 1 to 20 μm, and an average diameter of the particle Particles with a size of ±50% may be polydisperse particles of 90% or more of the total particle volume.

The reflective polarizing film may include a substrate and a coating layer on at least one surface of the substrate.

The substrate is polyethylene terephthalate (PET), polyethylene naphthalate (PEN), co-polyethylene naphthalate (co-PEN), polycarbonate (PC), polystyrene (PS), polymethyl methacrylate (PMMA), polybutylene Terephthalate (PBT), Polypropylene (PP), Polyethylene (PE), Acrylonitrile Butadiene Styrene (ABS), Polyurethane (PU), Polyimide (PI) Polyvinyl Chloride (PVC), StyreneAcrylonitrile (SAN) ) resin, ethylene vinyl acetate (EVA) resin, polyamide (PA), polyacetal (POM), phenol resin, epoxy (EP) resin, urea (UF) resin, melanin (MF) resin, polyester (UP), It may be a silicone (SI) resin, a cycloolefin polymer (COP), or a combination thereof. For example, the substrate is co-polyethylene naphthalate (co-PEN) in which monomers such as dimethyl-2,6-naphthalene dicarboxylate, dimethyl terephthalate, ethylene glycol, and cyclohexanedimethanol (CHDM) are appropriately polymerized. ) can be. For example, the substrate may be a mixed film of polyethylene terephthalate (PET) and polycarbonate (PC).

The substrate may have a plurality of dispersions randomly dispersed therein. Through this, it is possible to enhance the viewing angle characteristics through light diffusion and more easily express the light modulation effect at the boundary between the randomly dispersed dispersion and the substrate. A birefringent interface may be formed between the substrate and the dispersion included inside the substrate.

The material of the dispersion may be the same as or including the material of the above-described substrate. The dispersion may be, for example, polyethylene naphthalate (PEN). However, the material of the dispersion is not limited thereto, and any material of the dispersion commonly available in the art can be used.

A skin layer may be included on at least one surface of the substrate. In other words, a skin layer may be further included between the substrate and the coating layer. The skin layer serves to supplement the mechanical strength of the substrate. For example, the skin layer may be integrally formed by co-extrusion with a substrate without a separate adhesive layer. The skin layer integrally formed with such a substrate can not only prevent deterioration of optical properties due to the adhesive layer, but also significantly improve optical properties because many layers can be added to a limited thickness. In addition, since the skin layer integrally formed with the substrate is co-extruded and then subjected to a stretching process, it may be stretched in at least one axial direction. Through this, surface hardness may be improved compared to the unstretched skin layer, and thus scratch resistance may be improved. In some cases, a separate adhesive layer may be disposed between the substrate and the skin layer.

The material of the skin layer may be a material of a skin layer commonly used to perform the supporting function of the reflective polarizing film. For example, the material of the skin layer may be the same as or including the material of the above-described substrate.

For example, the substrate may have a thickness of 20 to 180 μm. For example, the skin layer may have a thickness of 50 to 500 μm. In addition, the total number of dispersions may be 25,000,000 to 80,000,000 when the thickness of the substrate is 120 μm based on 32 inches, but is not limited thereto.

The coating layer may include at least one particle having a K-value of 145 to 175. If the K-value of the particles is too high, the prism may be damaged, and if the K-value of the particles is too low, the reflective polarizing film may be damaged.

The diameter of the particles is 1 to 20 ㎛, and the particles having a size of ±50% of the average diameter of the particles may be polydisperse particles of 90% or more of the total particle volume. If the particles are monodisperse particles, the contact area between the particles and the prism increases, and as a result, the possibility of cracking may increase.

The refractive index of the particles may be 1.00 to 1.50. If the particle is out of the refractive index range, it may cause light diffusion and decrease luminance.

The light transmittance of the particles represented by Equation 1 below may be 85% or more:

<Equation 1>

Light transmittance of particles (%) = [{(Amount of transmitted light + Amount of refracted light) / Amount of incident light} x 100]

It is possible to prevent the luminance from deteriorating due to loss of light coming from the bottom of the backlight assembly unit including the reflective polarizing film due to particles.

The particles may be, for example, organic particles including nylon, polyethylene terephthalate (PET), or a combination thereof.

The particles of the coating layer can prevent friction with the prism while having excellent light transmittance and luminance when all of the K-value value, the diameter range of the particle, and the characteristics of the polydisperse particle are satisfied.

The coating layer may be formed by applying a composition for forming a coating layer on a base layer. The composition for forming the coating layer may include the aforementioned particles, a binder, and a solvent. If necessary, the composition for forming the coating layer may further include additives such as a slip agent, an antifoaming agent, a wetting and dispersing agent, an antistatic agent, a leveling agent, and a light stabilizer.

The binder serves to attach particles forming protrusions to the substrate of the reflective polarizing film. As the binder, both thermosetting and ultraviolet curable resins may be used. For example, the binder may be an acrylic resin, and may be used alone or in combination with an epoxy resin, a melamine resin, a polyurethane resin, a urethane acrylic resin, or the like, depending on the purpose of use.

As the solvent, methyl propylene glycol, toluene, methyl ethyl ketone, or ethyl acetate may be used. If necessary, these solvents may be used alone or in combination of two or more.

The content of the particles may be 0.2% to 8.0% by weight based on 100% by weight of the entire coating layer. If the content of the particles is less than 0.2% by weight, the content of the particles is not sufficient and there is a possibility of causing damage to the coating layer of the reflective polarizing film due to friction with the prism, and an appropriate haze cannot be applied to other films located at the bottom of the reflective polarizing film. may not be able to mask its flaws. If the content of the particles is 8.0% by weight or more, light coming from the lower end of the backlight assembly unit is lost and diffused, thereby reducing luminance.

The luminance of the reflective polarizing film may be 85% or more.

The thickness of the reflective polarizing film may be, for example, 125 μm to 350 μm.

1A is a schematic cross-sectional view of a reflective polarizing film according to one embodiment, and FIG. 1B is a schematic cross-sectional view of a reflective polarizing film according to another embodiment.

Referring to FIG. 1A , a coating layer 4 is disposed on both sides of the core layer 1 . Referring to FIG. 1B, skin layers 12 are disposed on both sides of the core layer 11, and coating layers 14 are disposed on the opposite side of the skin layer 12 in contact with the core layer 11, respectively. . The substrate 13 may be formed by combining the core layer 11 and the skin layer 12 .

A backlight assembly according to another embodiment may include the reflective polarizing film described above.

A liquid crystal display device according to another embodiment may include the above-described reflective polarizing film.

Hereinafter, the configuration of the present invention and its effects will be described in more detail through Examples and Comparative Examples. However, these examples are intended to explain the present invention in more detail, and it will be obvious that the scope of the present invention is not limited to these examples.

[Example]

Example 1: Reflective polarizing film

As a substrate, a polyethylene terephthalate (PET) film (Toray Advanced Materials Co., Ltd.) having a thickness of about 300 μm was used. After applying the composition for forming a coating layer on the substrate to a thickness of 5 μm with a Meyer bar, drying at 90 ° C. for 30 seconds and using a light amount of 300 mW / cm ² at a rate of 5 mpm, a reflective polarizing film as shown in FIG. 1 described later produced.

<Composition for Forming Coating Layer>

Acrylic resin binder (SH-340, Samhwa Paint): 50% by weight

Curing agent (IRG184, Ciba): 1% by weight

Acrylic polymer slip agent (BYK-UV3500, BYK-Chemie GmbH.): 0.5% by weight

Methyl Propylene Glycol: 45% by weight

Nylon particles (SP-10, average diameter: 10 μm, Toray): 3.5% by weight

Example 2: Reflective polarizing film

In the composition for forming a coating layer, except for using 3.5% by weight of polyethylene terephthalate particles (TCP5010, average diameter: 10 μm, 2H Chem Co., Ltd.) instead of 3.5% by weight of nylon particles (SP-10, average diameter: 10 μm, Toray) A reflective polarizing film was prepared in the same manner as in Example 1.

Comparative Example 1: Reflective polarizing film

Except for using 3.5% by weight of polymethyl methacrylate particles (MF5FD, average diameter: 5 ㎛, Kolon) instead of 3.5% by weight of nylon particles (SP-10, average diameter: 10 ㎛, Toray) in the composition for forming the coating layer. , A reflective polarizing film was prepared in the same manner as in Example 1.

Comparative Example 2: Reflective polarizing film

In the coating layer forming composition, 3.5 wt% of polybutyl methacrylate particles (GB-05S, average diameter: 5 μm, AICA KOGYO) were used instead of 3.5 wt% of nylon particles (SP-10, average diameter: 10 μm, Toray) Except, a reflective polarizing film was prepared in the same manner as in Example 1.

Evaluation Example 1: Evaluation of physical properties of reflective polarizing film

The physical properties of the reflective polarizing films prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were measured according to the following method, and the results are shown in Table 1, FIGS. 2a to 2d, and FIGS. 3a to 3d .

(1) Relative luminance evaluation

After bringing the coating layer of each reflective polarizing film and the reflective polarizing disc into contact with the prism, the frontal luminance (nit) was measured with a Minolta luminance measuring device (CA-210). Thereafter, the luminance of each reflective polarizing film, that is, the relative luminance (%), was calculated based on the luminance of the reflective polarizing disk 100 as a standard.

(2) Difference evaluation with Prism

The coating layer of each reflective polarizing film was brought into contact with the prism, and a weight having a load of 200 g was raised and rubbed from side to side 100 times using a force of 20 N, and then the degree of scratches on the surface of the reflective film coating layer and the prism surface was confirmed by a photograph. The results are shown in Figs. 2a to 2d, and the split evaluation was performed in the following manner.

O: Forking River

△: about splitting

X: no split

(3) Evaluation of light transmittance of particles

For the particles included in the coating layer of each of the reflective polarizing films, the light transmittance was calculated according to Equation 1 below using a UV/VIS spectrophotometer.

<Equation 1>

Particle light transmittance (%) = [{(light amount of transmitted light + light amount of refracted light) / light amount of incident light} x 100]

(4) Evaluation of K-value (particle hardness)

The K-value (particle hardness) of the particles included in the coating layer of each of the reflective polarizing films was measured using a Micro Compression Tester.

(5) Evaluation of particle size distribution

The particle size of the particles included in the coating layer of each of the reflective polarizing films was measured using a particle size analyzer, and the results are shown in FIGS. 3A to 3D.

division particle type particle content
(weight%) relative luminance
(%) split of particles
light transmittance
(%) K-value value Example 1 nylon 3.5 89.6 △ 85 160 Example 2 Polyethylene terephthalate 3.5 89.2 △ 85 170 Comparative Example 1 polymethyl methacrylate 3.5 90.7 O 87 375 Comparative Example 2 polybutyl methacrylate 3.5 90.2 O 85 205

Referring to Table 1, the reflective polarizing film prepared in Examples 1 and 2 has a similar level of light transmittance and relative luminance to the reflective polarizing film manufactured in Comparative Examples 1 and 2, but the light guide plate (prism) It can be confirmed that it exhibits improved characteristics in the presence or absence of grinding.

In addition, referring to FIGS. 3A to 3D, the reflective polarizing film prepared in Examples 1 and 2 has particles having an average diameter of 10 μm and a size of ±50% compared to the reflective polarizing film prepared in Comparative Examples 1 and 2. It can be confirmed that more than 90% of the particle volume is polydisperse particles.

1, 11: core layer, 4, 14: coating layer,
10, 20: reflective polarizing film, 12: skin layer, 13: substrate

Claims (12)

write; and
Including; a coating layer on at least one surface of the substrate,
The coating layer includes at least one particle having a K-value of 145 to 175,
The diameter of the particles is 1 to 20 μm
Particles having a size of ±50% of the average diameter of the particles are polydisperse particles of 90% or more of the total particle volume,
A reflective polarizing film in which the content of the particles is 0.2% to 8.0% by weight based on 100% by weight of the total coating layer. According to claim 1,
The refractive index of the particles is 1.00 to 1.50, the reflective polarizing film. According to claim 1,
A reflective polarizing film having a light transmittance of 85% or more represented by Equation 1 below of the particles:
<Equation 1>
Particle light transmittance (%) = [{(light amount of transmitted light + light amount of refracted light) / light amount of incident light} x 100] According to claim 1,
A reflective polarizing film in which the particles include nylon, polyethylene terephthalate (PET), or a combination thereof. According to claim 1,
The coating layer further comprises a binder, the reflective polarizing film. delete According to claim 1,
The substrate is polyethylene terephthalate (PET), polyethylene naphthalate (PEN), co-polyethylene naphthalate (co-PEN), polycarbonate (PC), polystyrene (PS), polymethyl methacrylate (PMMA), polybutylene Terephthalate (PBT), Polypropylene (PP), Polyethylene (PE), Acrylonitrile Butadiene Styrene (ABS), Polyurethane (PU), Polyimide (PI) Polyvinyl Chloride (PVC), StyreneAcrylonitrile (SAN) ) resin, ethylene vinyl acetate (EVA) resin, polyamide (PA), polyacetal (POM), phenol resin, epoxy (EP) resin, urea (UF) resin, melanin (MF) resin, polyester (UP), A reflective polarizing film that is a silicone (SI) resin, a cycloolefin polymer (COP), or a combination thereof. According to claim 1,
A reflective polarizing film in which the luminance of the reflective polarizing film is 85% or more. According to claim 1,
The reflective polarizing film further comprises a skin layer between the substrate and the coating layer. According to claim 1,
The reflective polarizing film has a thickness of 125 μm to 350 μm. A backlight assembly comprising the reflective polarizing film according to any one of claims 1 to 5 and 7 to 10. A display device comprising the reflective polarizing film according to any one of claims 1 to 5 and 7 to 10.

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