OPTICAL FILM HAVING HIGH RELIABILITY AND METHOD FOR MANUFACTURING THE SAME

An optical film having high reliability and a method for manufacturing the same are provided. The optical film includes a quantum dot layer, an upper protective layer and a lower protective layer. The upper protective layer is formed on a surface of the quantum dot layer. The lower protective layer is formed on another opposite surface of the quantum dot layer. The upper protective layer and the lower protective layer each include a bonding layer, a moisture and oxygen barrier layer, and a substrate layer located between the bonding layer and the moisture and oxygen barrier layer. The bonding layer is arranged proximate to the quantum dot layer and formed from an aqueous coating material. The moisture and oxygen barrier layer is arranged away from the quantum dot layer and includes an evaporated layer and an outer plastic layer formed on the evaporated layer.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of priority to Taiwan Patent Application No. 109137022, filed on Oct. 26, 2020. The entire content of the above identified application is incorporated herein by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to an optical film, and more particularly to an optical film having high reliability and a method for manufacturing the same.

BACKGROUND OF THE DISCLOSURE

With the rapid development of audiovisual entertainment industries, the demand for displays continues to rise. Displays with both high chroma and low profile have gradually become a mainstream development trend in the market.

Under the NTSC (National Television System Committee) standard, the color gamut of an LED reaches 72%, and the color gamut of an OLED can reach up to 100%. Among luminescent materials used for displays, a quantum dot film has better color purity and a wider color gamut. The color purity of the quantum dot film is 50% higher than that of the LED, and the color gamut of the quantum dot film can reach up to 110%. The quantum dot film has gradually received attention due to good optical display characteristics, and has become one of preferred materials used under the current trend of providing excellent viewing experiences.

However, quantum dot film displays are not popular in the current market, mainly because a quantum dot film is not resistant to water and oxygen. Once a peripheral edge area of the quantum dot film comes into contact with exterior air or moisture, an edge degradation problem would occur in the peripheral edge area, which does not meet the basic requirements for long-term stable use of the displays.

A common water-proof and oxygen-proof treatment method is to attach two barrier films to upper and lower sides of the quantum dot film, respectively, which can prevent the quantum dot film from being penetrated by water and oxygen and thus lose its luminous characteristics. Although the two barrier films can increase product stability, thereby extending service life, the two barrier films have high production costs, contribute to a greater thickness, and their adhesion to the quantum dot film is less than satisfactory. In consideration of market price, product quality, and economic benefits, the products of the quantum dot film displays have been unable to achieve breakthroughs in development and widespread promotion.

Therefore, how the requirements of long-term water and oxygen resistances can be met, while providing a balance between the thickness of the barrier layer and the production costs, are important issues for future promotion of the quantum dot film displays.

SUMMARY OF THE DISCLOSURE

In response to the above-referenced technical inadequacies, the present disclosure provides an optical film having high reliability that can not only prevent failure of quantum dots, but also increase structural stability. The present disclosure also provides a method for manufacturing the optical film.

In one aspect, the present disclosure provides an optical film having high reliability, which includes a quantum dot layer, an upper protective layer, and a lower protective layer. The quantum dot layer has a first surface and a second surface opposite to the first surface. The upper protective layer is formed on the first surface and the lower protective layer is formed on the second surface. The upper protective layer and the lower protective layer each include a bonding layer, a moisture and oxygen barrier layer, and a substrate layer located between the bonding layer and the moisture and oxygen barrier layer. The bonding layer is arranged proximate to the quantum dot layer and formed from an aqueous coating material. The moisture and oxygen barrier layer is arranged away from the quantum dot layer and includes an evaporated layer and an outer plastic layer formed on the evaporated layer.

In another aspect, the present disclosure provides a method for manufacturing an optical film having high reliability, which includes: providing a substrate layer; forming a moisture and oxygen barrier layer on an outer surface of the substrate layer, and coating an aqueous coating material on an inner surface of the substrate layer; the moisture and oxygen barrier layer includes an evaporated layer and an outer plastic layer formed on the evaporated layer; and attaching the substrate layer with the moisture and oxygen barrier layer to a quantum dot layer by the aqueous coating material and curing the aqueous coating material into a bonding layer; the bonding layer, the substrate layer, and the moisture and oxygen barrier layer jointly form a protective layer.

In one embodiment of the present disclosure, the evaporated layer is an evaporated layer of aluminum oxide or copper.

In one embodiment of the present disclosure, the outer plastic layer is a polyurethane (PU) layer.

In one embodiment of the present disclosure, the evaporated layer has a thickness from 0.01 μm to 0.5 μm, and the outer plastic layer has a thickness from 0.5 μm to 10 μm.

In one embodiment of the present disclosure, the substrate layer is a polyethylene terephthalate (PET) layer.

In one embodiment of the present disclosure, the aqueous coating material includes 5 to 15 wt % of isopropanol, 5 to 15 wt % of sodium bicarbonate, 5 to 20 wt % of an organic acid, and 10 to 30 wt % of at least one acrylic-based monomer.

One of the beneficial effects of the present disclosure is that, the optical film having high reliability can allow quantum dots to be completely isolated from the external environment, thereby preventing the quantum dots from failure due to coming in contact with moisture or oxygen, and can improve adhesion between layers, by virtue of “the upper protective layer and the lower protective layer each including a bonding layer proximate to the quantum dot layer and a moisture and oxygen barrier layer distant from the quantum dot layer, in which the bonding layer is formed from an aqueous coating material and the moisture and oxygen barrier layer includes an evaporated layer and an outer plastic layer formed on the evaporated layer”.

Furthermore, the optical film of the present disclosure does not need one or more additional adhesive layers, and a total thickness and production costs are therefore reduced.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The terms used herein generally have their ordinary meanings in the art. In the case of conflict, the present document, including any definitions given herein, will prevail. The same thing can be expressed in more than one way.

Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this invention belongs. As used herein, the singular forms “a,” “an,” and “the,” are intended to include the plural forms.

Unless indicated otherwise, all percentages disclosed herein are in weight percent. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges and are also encompassed within the disclosure, subject to any specifically excluded limit in the stated range.

First Embodiment

Referring toFIG. 1, a first embodiment of the present disclosure provides an optical film Z having high reliability, which includes a quantum dot layer1, an upper protective layer2a, and a lower protective layer2b. The quantum dot layer1has a first surface11(e.g., an upper surface) and a second surface12(e.g., a lower surface) opposite to the first surface. The upper protective layer2ais formed on the first surface11of the quantum dot layer1. The lower protective layer2bis formed on the second surface12of the quantum dot layer1. In use, the upper protective layer2aand the lower protective layer2bcan not only protect the quantum dot layer1from being physically damaged, but also prevent the quantum dot layer1from failure.

Reference is made toFIG. 2andFIG. 3, the upper protective layer2aand the lower protective layer2bhave the same structure. The upper protective layer2aincludes a bonding layer22a, a moisture and oxygen barrier layer23a, and a substrate layer21alocated between the bonding layer22aand the moisture and oxygen barrier layer23a. The lower protective layer2balso includes a bonding layer22b, a moisture and oxygen barrier layer23b, and a substrate layer21blocated between the bonding layer22band the moisture and oxygen barrier layer23b. It should be noted that, the bonding layer22aof the upper protective layer2aand the bonding layer22bof the lower protective layer2bare arranged proximate to the quantum dot layer1and are each formed from an aqueous coating material. The aqueous coating material can use the same polymer system (e.g., an acrylic system) as the quantum dot layer1, so as to increase adhesion of layers. The moisture and oxygen barrier layer23aof the upper protective layer2aand the moisture and oxygen barrier layer23bof the lower protective layer2bare arranged away from the quantum dot layer1, and each include an evaporated layer231a,231band an outer plastic layer232a,232bformed on the evaporated layer231a,231b. Therefore, quantum dots can be completely isolated from the external environment to effectively block moisture and oxygen.

In practice, the substrate layer21aof the upper protective layer2aand the substrate layer21bof the lower protective layer2bare each formed from a polyester, so as to have characteristics including high transparency and high stiffness. Specific examples of the polyester include polyethylene terephthalate (PET), polypropylene terephthalate (PPT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polycyclohexylenedimethylene terephthalate (PCT), polycarbonate (PC), and polyarylate. The polyester is preferably PET. Furthermore, the substrate layer21aof the upper protective layer2aand the substrate layer21bof the lower protective layer2bcan have good softness and ductility by a biaxial stretching treatment, thereby increasing a flexibility of use of the optical film Z.

The biaxial stretching treatment can be applied by a tenter-type stretching machine, but is not limited thereto. In the biaxial stretching treatment, an unstretched substrate layer21aor substrate layer21bis stretched in a machine direction (MD) (also called “length direction”) at a predetermined temperature and a desired stretch ratio, and is then stretched in a transverse direction (TD) (also called “width direction”) at another predetermined temperature and the desired stretch ratio, so as to form a biaxially stretched substrate layer21aor substrate layer21b. According to practical requirements, a stretching process of the machine direction and a stretching process of the transverse direction can be applied in the reverse order. Also, in the biaxial stretching treatment, the unstretched substrate layer21aor substrate layer21bcan be simultaneously and biaxially stretched in the machine direction and transverse direction at still another predetermined temperature and the desired stretch ratio.

The aqueous coating material for forming the bonding layer22aof the upper protective layer2aand the bonding layer22bof the lower protective layer2bincludes isopropanol (IPA), sodium bicarbonate, an organic acid, and at least one acrylic-based monomer. The aqueous coating material can be coated on an inner surface of the substrate layer21aand then be cured (e.g., cured with heat or light) to form the bonding layer22a. Based on the consideration of costs and adhesion of layers, a thickness of the bonding layer22acan be from 0.01 μm to 0.5 μm. Similarly, the aqueous coating material can be coated on an inner surface of the substrate layer21band then be cured (e.g., cured with heat or light) to form the bonding layer22b. Based on the same consideration, a thickness of the bonding layer22bcan be from 0.01 μm to 0.5 μm.

More specifically, a pH value of the aqueous coating material can be between 5.0 and 6.7. Based on 100 weight percent (wt %) of the aqueous coating material, a content of water can be from 30 wt % to 70 wt %, a content of the IPA can be from 5 wt % to 15 wt %, a content of the sodium bicarbonate can be from 5 wt % to 15 wt %, a content of the organic acid can be from 5 wt % to 20 wt %, and a content of the at least one acrylic-based monomer can be from 10 wt % to 30 wt %.

In the moisture and oxygen barrier layer23aof the upper protective layer2a, the evaporated layer231acan be an evaporated layer of aluminum oxide or copper, and the outer plastic layer232acan be a polyurethane (PU) layer formed by coating. Based on the consideration of costs and product reliability, a thickness of the evaporated layer231acan be from 0.01 μm to 0.5 μm, and a thickness of the outer plastic layer232acan be from 0.5 μm to 10 μm. Similarly, in the moisture and oxygen barrier layer23bof the lower protective layer2b, the evaporated layer231bcan be an evaporated layer of aluminum oxide or copper, and the outer plastic layer232bcan be a polyurethane (PU) layer formed by coating. Based on the same consideration, a thickness of the evaporated layer231bcan be from 0.01 μm to 0.5 μm, and a thickness of the outer plastic layer232bcan be from 0.5 μm to 10 μm.

The quantum dot layer1mainly includes quantum dots, and in addition, can include a photoinitiator, a plurality of scattering particles, a mercaptan, and at least one acrylic-based monomer. Based on a total weight of the quantum dot layer1being 100 wt %, a content of the quantum dots can be from 0.1 wt % to 10 wt %, a content of the photoinitiator can be from 1 wt % to 5 wt %, a content of the scattering particles can be from 1 wt % to 30 wt %, a content of the mercaptan can be from 15 wt % to 65 wt %, and a content of the at least one acrylic-based monomer can be from 30 wt % to 60 wt %.

The scattering particles of the quantum dot layer1can be surface treated microbeads having a diameter of 0.5 μm to 20 μm that are made of acrylic, silicon dioxide, or polystyrene.

Table 1 below shows performances of various target parameters of quantum dot layers1resulting from different ratios of mercaptan to acrylic. It can be seen from Table 1 that a preferable ratio of mercaptan to acrylic is 3:7, 5:5, or 6:4.

In Table 1, the target parameters are tested by methods as follows:

UV intensity: tested by a UV intensity sensor (UV Power Puck® II available from EIT Inc, USA).

Adhesion: tested through pulling apart upper and lower protective layers from a quantum dot layer by a tensile machine, the quantum dot layer being clamped between the upper and lower protective layers prior to the test. If the upper and lower protective layers are broken after being pulled apart from the quantum dot layer (i.e., the upper and lower protective layers cannot be pulled apart without breaking), an adhesion of the quantum dot layer is recorded as “good”. If each of the upper and lower protective layers has a gel layer adhered thereon after being pulled apart from the quantum dot layer, an adhesion of the quantum dot layer is recorded as “fair”. If only one of the upper and lower protective layers has a gel layer adhered thereon after being pulled apart from the quantum dot layer, an adhesion of the quantum dot layer is recorded as “poor”.

Physical properties: tested by a bending machine with a bending angle of 60 degrees and observed whether brittle fracture or permanent deformation occurs in the quantum dot layer after being bent for 10,000 times.

Optical properties: tested by a luminance meter with an irradiation of a backlight module, in which conditions for excitation include a 12 W blue light source, a color coordinate of (x=0.155, y=0.026), a dominant wavelength of 450 nm, and a full width at half maximum of 20 nm.

Environmental testing: tested in an environmental testing box under conditions of a temperature of 65° C. and a relative humidity of 95%, after which a difference of color coordinate is less than 0.01 and a decline rate of brightness is less than 15%. The quantum dot layers are taken out of the environmental testing box every 250 hours for testing adhesion, physical properties, and optical properties.

Second Embodiment

Reference is made toFIG. 4, which is to be read in conjunction withFIG. 1. The present disclosure further provides a method for manufacturing an optical film Z having the above-mentioned structure, which includes: step S1, providing a substrate layer; step S2, forming a moisture and oxygen barrier layer on an outer surface of the substrate layer and coating an aqueous coating material on an inner surface of the substrate layer; and step S3, attaching the substrate layer with the moisture and oxygen barrier layer to a quantum dot layer by the aqueous coating material and curing the aqueous coating material into a bonding layer. Although this embodiment merely describes forming a protective layer on one side of the quantum dot layer, in practice, the method of the present disclosure can form two protective layers on two sides of the quantum dot layer, respectively. Accordingly, quantum dots can be completely isolated from the external environment, thereby preventing the quantum dots from failure due to coming in contact with moisture or oxygen.

In step S1, the substrate layer can be formed from a polyester. Specific examples of the polyester include polyethylene terephthalate (PET), polypropylene terephthalate (PPT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polycyclohexylenedimethylene terephthalate (PCT), polycarbonate (PC), and polyarylate. The polyester is preferably PET. Furthermore, the substrate layer21can be biaxially stretched.

In step S2, an evaporated layer can be formed on the outer surface of the substrate layer by evaporating, and an outer plastic layer can then be formed on the evaporated layer by coating, so as to form the moisture and oxygen barrier layer. In addition, the aqueous coating material coated on the inner surface of the substrate layer mainly includes isopropanol (IPA), sodium bicarbonate, an organic acid and at least one acrylic-based monomer. Based on 100 weight percent (wt %) of the aqueous coating material, a content of water can be from 30 wt % to 70 wt %, a content of the IPA can be from 5 wt % to 15 wt %, a content of the sodium bicarbonate can be from 5 wt % to 15 wt %, a content of the organic acid can be from 5 wt % to 20 wt %, and a content of the at least one acrylic-based monomer can be from 10 wt % to 30 wt %.

In step S3, the substrate layer with the moisture and oxygen barrier layer is attached to a surface of the substrate layer by being spaced apart from the aqueous coating material, and the aqueous coating material is then cured into a bonding layer. The bonding layer, the substrate, and the moisture and oxygen barrier layer jointly form a protective layer. The quantum dot layer mainly includes quantum dots, and can further include a photoinitiator, a plurality of scattering particles, a mercaptan, and at least one acrylic-based monomer. Based on a total weight of the quantum dot layer1being 100 wt %, a content of the quantum dots can be from 0.1 wt % to 10 wt %, a content of the photoinitiator can be from 1 wt % to 5 wt %, a content of the scattering particles can be from 1 wt % to 30 wt %, a content of the mercaptan can be from 15 wt % to 65 wt %, and a content of the at least one acrylic-based monomer can be from 30 wt % to 60 wt %.

The scattering particles of the quantum dot layer1can be surface treated microbeads having a diameter of 0.5 μm to 20 μm that are made of acrylic, silicon dioxide, or polystyrene.

The method of the present disclosure can further include: step S4, cutting the optical film to a required size; and step S5, winding the remaining optical film into a roll for use or storage in a convenient manner.

BENEFICIAL EFFECTS OF THE EMBODIMENTS

One of the beneficial effects of the present disclosure is that, the optical film having high reliability can allow quantum dots to be completely isolated from the external environment, thereby preventing the quantum dots from failure due to coming in contact with moisture or oxygen, and can improve adhesion between layers, by virtue of “the upper protective layer and the lower protective layer each including a bonding layer proximate to the quantum dot layer and a moisture and oxygen barrier layer away from the quantum dot layer, in which the bonding layer is formed from an aqueous coating material and the moisture and oxygen barrier layer includes an evaporated layer and an outer plastic layer formed on the evaporated layer”.

The above beneficial effect(s) can be verified from performance test results shown in Table 2.

Furthermore, the optical film of the present disclosure does not need one or more additional adhesive layers, and a total thickness and production costs are therefore reduced.