ARTICLE FOR DISPLAY DEVICE, DISPLAY SYSTEM AND METHOD OF MANUFACTURE

An article (100) for a display device includes a diffraction grating film (102), a first optically clear adhesive layer (120), and a second optically clear adhesive layer (130). The diffraction grating film includes a base layer (104) and a plurality of microstructures (106) projecting from the base layer. The base layer defines a non-structured surface of the diffraction grating film and the plurality of microstructures define a structured surface of the diffraction grating film opposite to the non-structured surface. The first optically clear adhesive layer is disposed on the structured surface of the diffraction grating film. The second optically clear adhesive layer is disposed on the non-structured surface of the diffraction grating film.

TECHNICAL FIELD

The present disclosure relates to articles for display devices, display systems including such articles, and methods of manufacturing such articles.

BACKGROUND

A liquid crystal display (LCD) uses light-modulating properties of liquid crystals. A conventional LCD panel display may have a low on-axis contrast. A dual LCD system may provide a higher contrast and an improved black state than the conventional LCD panel display to compete with a typical organic light-emitting diode (OLED) display in terms of contrast ratio and efficiency. However, laminating a top LCD and a bottom LCD in a dual LCD system may cause optical interference and further cause moiré effect. The moiré effect may be observed as an interference phenomenon when two similar lattices are overlapped. The moiré effect may result from the optical interference between two or more regular structures having different intrinsic frequencies. Since the top LCD and the bottom LCD include a plurality of individually addressable pixels, there can be a possibility of moiré effect between an image formed by the top LCD and an image formed by the bottom LCD. One solution to reduce the optical interference and the moiré effect includes applying a matte coating on a polarizer, however, the matte coating may reduce brightness of the dual LCD system.

A standard optically clear adhesive (OCA) may not reduce the optical interference and the moiré effect. It may therefore be desirable to have an optically clear adhesive that helps in reducing the optical interference and the moiré effect without affecting the brightness and the clarity of the dual LCD system.

SUMMARY

Generally, the present disclosure relates to articles for display devices. The present disclosure also relates to display systems including such articles, and methods of manufacturing such articles.

Some embodiments of the present disclosure relate to an article for a display device including a diffraction grating film, a first optically clear adhesive layer, and a second optically clear adhesive layer. The diffraction grating film includes a base layer and a plurality of microstructures projecting from the base layer. The base layer defines a non-structured surface of the diffraction grating film and the plurality of microstructures define a structured surface of the diffraction grating film opposite to the non-structured surface. The first optically clear adhesive layer is disposed on the structured surface of the diffraction grating film. The second optically clear adhesive layer is disposed on the non-structured surface of the diffraction grating film.

In some embodiments, the base layer defines a longitudinal axis along its length and the plurality of microstructures extends along the base layer to define a primary axis.

The primary axis and the longitudinal axis define a bias angle therebetween. The bias angle is in a range of between about 0 degree and about 90 degrees.

In some embodiments, the bias angle is in a range of between about 20 degrees and about 70 degrees.

In some embodiments, the plurality of microstructures has a peak to valley height in a range of between about 2.4 microns and about 10 microns.

In some embodiments, the plurality of microstructures has a pitch in a range of between about 2 microns and about 50 microns.

In some embodiments, each microstructure is substantially prismatic.

In some embodiments, the first optically clear adhesive layer has a refractive index of between about 1.47 and about 1.49.

In some embodiments, the second optically clear adhesive layer has a refractive index of between about 1.47 and about 1.49.

In some embodiments, a thickness of the first optically clear adhesive layer is greater than the peak to valley height of the plurality of microstructures.

In some embodiments, the article further includes a first release liner immediately adjacent to the first optically clear adhesive layer and a second release liner immediately adjacent to the second optically clear adhesive layer.

Some embodiments of the present disclosure relate to a display system including an illumination source, a first liquid crystal assembly, a second liquid crystal assembly, and an article. The illumination source is configured to emit light over an emission surface of the illumination source and includes at least one light source. The first liquid crystal assembly is configured to selectively transmit and reflect light received from the emission surface of the illumination source. The second liquid crystal assembly is configured to receive light from the first liquid crystal assembly and emit an image for viewing by a viewer. The second liquid crystal assembly is disposed on the first liquid crystal assembly. The article is disposed between the first liquid crystal assembly and the second liquid crystal assembly. The article includes a diffraction grating film, a first optically clear adhesive layer, and a second optically clear adhesive layer. The diffraction grating film includes a base layer and a plurality of microstructures projecting from the base layer. The base layer defines a non-structured surface of the diffraction grating film and the plurality of microstructures define a structured surface of the diffraction grating film opposite to the non-structured surface. The first optically clear adhesive layer is disposed on the structured surface of the diffraction grating film. The second optically clear adhesive layer is disposed on the non-structured surface of the diffraction grating film.

Some embodiments of the present disclosure relate to a method of manufacturing an article for use with a display device. The method includes providing a diffraction grating film including a base layer and a plurality of microstructures projecting from the base layer. The base layer defines a non-structured surface of the diffraction grating film and the plurality of microstructures define a structured surface of the diffraction grating film opposite to the non-structured surface. The method further includes providing a first optically clear adhesive layer on the structured surface of the diffraction grating film. The method further includes providing a second optically clear adhesive layer on the non-structured surface of the diffraction grating film.

In some embodiments, the method further includes rotating the diffraction grating film to a bias angle after providing the first optically clear adhesive layer and the second optically clear adhesive layer on the diffraction grating film.

In some embodiments, the method further includes rotating the diffraction grating film to a bias angle prior to providing the first optically clear adhesive layer and the second optically clear adhesive layer on the diffraction grating film.

In some embodiments, the method further includes die cutting the diffraction grating film to a bias angle after providing the first optically clear adhesive layer and the second optically clear adhesive layer on the diffraction grating film.

In some embodiments, the method further includes die cutting the diffraction grating film to a bias angle prior to providing the first optically clear adhesive layer and the second optically clear adhesive layer on the diffraction grating film.

In some embodiments, the bias angle is in a range of between about 20 degrees and about 70 degrees.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanying figures that form a part thereof and in which various embodiments are shown by way of illustration. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense.

As recited herein, all numbers should be considered modified by the term “about”.

As used herein as a modifier to a property or attribute, the term “generally”, unless otherwise specifically defined, means that the property or attribute would be readily recognizable by a person of ordinary skill but without requiring absolute precision or a perfect match (e.g., within +/−20% for quantifiable properties).

The term “substantially”, unless otherwise specifically defined, means to a high degree of approximation (e.g., within +/−10% for quantifiable properties) but again without requiring absolute precision or a perfect match. Terms such as same, equal, uniform, constant, strictly, and the like, are understood to be within the usual tolerances or measuring error applicable to the particular circumstance rather than requiring absolute precision or a perfect match.

As used herein, layers, components, or elements may be described as being adjacent one another. Layers, components, or elements can be adjacent one another by being in direct contact, by being connected through one or more other components, or by being held next to one another or attached to one another. Layers, components, or elements that are in direct contact may be described as being immediately adjacent.

The present disclosure relates to an article. The article may be used in a display system. In some embodiments, the article may be used in a dual Liquid Crystal Display (LCD) system. The present disclosure also relates to a method of manufacturing the article for use with the display device. The article includes a diffraction grating film, a first optically clear adhesive, and a second optically clear adhesive.

A moiré effect and an optical interference may be observed when two similar lattices are overlapped. The moiré effect may result from the optical interference among two or more regular structures having different intrinsic frequencies. The display system of the present disclosure includes an illumination source, a first liquid crystal assembly and a second liquid crystal assembly. Since each of the first liquid crystal assembly and the second liquid crystal assembly includes a plurality of individually addressable pixels, there can be a possibility of the moiré effect between an image formed by the first liquid crystal assembly and an image formed by the second liquid crystal assembly.

By including the article in the display system, the optical interference and the moiré effect may be substantially reduced without affecting a brightness and a clarity of the display system.

The term “optically clear adhesive”, as used herein, refers to an adhesive that exhibits an optical transmission of at least about 80%, as measured on a sample having a thickness from about 25 microns (μm) to about 250 μm. In some embodiments, the optical transmission may be at least about 85%, 90%, 95% or even higher.

The term “microstructures”, as used herein, are generally projections, protrusions and/or indentations in the surface of an article that deviate in profile from an average center line drawn through the microstructure.

FIG.1illustrates a cross-sectional view of an article100for a display device according to the present disclosure. The article100includes a diffraction grating film102, a first optically clear adhesive layer120, and a second optically clear adhesive layer130. The article100defines mutually orthogonal X, Y and Z-axes. The X and Y-axes are in-plane axes of the article100, while the Z-axis is a transverse axis disposed along a thickness of the article100. In other words, the X and Y-axes are disposed along a plane of the article100, while the Z-axis is perpendicular to the plane of the article100. The diffraction grating film102, the first optically clear adhesive layer120, and the second optically clear adhesive layer130of the article100are disposed adjacent to each other along the Z-axis.

The diffraction grating film102includes a base layer104and a plurality of microstructures106projecting from the base layer104.

The base layer104further defines a non-structured surface110of the diffraction grating film102. The non-structured surface110is a substantially planar surface. The plurality of microstructures106further define a structured surface105of the diffraction grating film102opposite to the non-structured surface110.

In some embodiments, the structured surface105may have any periodically repeating shape, for example, a sinusoidal shape, a square wave shape, a cube-corner shape, a triangular shape, and so forth. In some other embodiments, the structured surface105may have any other periodically repeating regular or irregular shapes.

In some embodiments, the base layer104includes a polymerizable resin or any other suitable material. In some embodiments, the polymerizable resin may include a combination of a first polymerizable component and a second polymerizable component selected from (meth)acrylate monomers, (meth)acrylate oligomers, and mixtures thereof. As used herein, “monomer” or “oligomer” is any substance that can be converted into a polymer. The term “(meth)acrylate” refers to both acrylate and methacrylate compounds. In some cases, the polymerizable composition may include a (meth)acrylated urethane oligomer, (meth)acrylated epoxy oligomer, (meth)acrylated polyester oligomer, a (meth)acrylated phenolic oligomer, a (meth)acrylated acrylic oligomer, and mixtures thereof.

In some embodiments, each of the plurality of microstructures106has a peak to valley height h in a range of between about 2.4 microns and about 10 microns. In some other embodiments, the peak to valley height h of each microstructure106is in a range of between about 5 microns and about 20 microns. The peak to valley height h of each microstructure106may vary based on application requirements.

In some embodiments, the plurality of microstructures106has a pitch P in a range of between about 2 microns and about 50 microns. In some other embodiments, the pitch P of the plurality of microstructures106is in a range of between about 10 microns and about 80 microns. The pitch P of the plurality of microstructures106may vary based on application requirements.

In the illustrated embodiment ofFIG.1, each microstructure106is substantially prismatic. In some other embodiments, each microstructure106may have a substantial hemispherical shape, a substantial conical shape, a substantial cuboidal shape, and so forth. The plurality of microstructures106may have any suitable shape as per application requirements.

In some embodiments, the microstructures106are arranged in multiple rows. The rows of the microstructures106may be uniformly or non-uniformly spaced apart from each other. A distance between adjacent rows may be selected as per application requirements. In some embodiments, the pitch P of the microstructures106may vary periodically or nonperiodically in one or more rows. In some embodiments, the peak to valley height h of the microstructures106may vary periodically or nonperiodically in one or more rows.

The first optically clear adhesive layer120is disposed on the structured surface105of the diffraction grating film102. In some embodiments, the first optically clear adhesive layer120has a refractive index of between about 1.47 and about 1.49. In some other embodiments, the refractive index of the first optically clear adhesive layer120is of between about 1.49 and about 1.51. The first optically clear adhesive layer120may include any type of adhesive material, such as a liquid adhesive, an acrylate, a pressure sensitive adhesive, a stretch release adhesive, an adhesive foam, etc. The present disclosure is not limited by type of adhesive in any manner. A thickness T1 of the first optically clear adhesive layer120may vary as per application requirements. The thickness T1 of the first optically clear adhesive layer120is greater than the peak to valley height h of the plurality of microstructures106(i.e., T1>h).

The second optically clear adhesive layer130is disposed on the non-structured surface110of the diffraction grating film102. In some embodiments, the second optically clear adhesive layer130has a refractive index of between about 1.47 and about 1.49. In some other embodiments, the refractive index of the second optically clear adhesive layer130is of between about 1.49 and about 1.51. The second optically clear adhesive layer130may include any type of adhesive material, such as a liquid adhesive, an acrylate, a pressure sensitive adhesive, a stretch release adhesive, an adhesive foam, etc. The present disclosure is not limited by type of adhesive in any manner. A thickness T2 of the second optically clear adhesive layer130may vary as per application requirements.

The article100includes the first optically clear adhesive layer120and second optically clear adhesive layer130so that the diffraction grating film102may be used to laminate the article100to another layer or to a surface, for example, of a display device.

In the illustrated embodiment ofFIG.1, the article100further includes a first release liner140and a second release liner150. The first release liner140is immediately adjacent to the first optically clear adhesive layer120. In some embodiments, the first release liner140may include an anti-static tight liner, an easy liner, and so forth. The present disclosure is not limited by type of release liner in any manner.

The second release liner150is immediately adjacent to the second optically clear adhesive layer130. In some embodiments, the second release liner150may include an anti-static tight liner, an easy liner, and so forth. The present disclosure is not limited by type of release liner in any manner.

FIG.2illustrates a partial schematic view of the diffraction grating film102including the plurality of microstructures106. In the illustrated embodiment, each of the plurality of microstructures106is substantially prismatic.FIG.2further illustrates the plurality of microstructures106having an exemplary bias angle.

Referring now toFIGS.1and2, the base layer104defines a longitudinal axis LA along its length and the plurality of microstructures106extends along the base layer104to define a primary axis A. In some embodiments, the longitudinal axis LA of the base layer104may be parallel to the X-axis of the article100. The primary axis A and the longitudinal axis LA define a bias angle B therebetween. In some embodiments, the bias angle B is in a range of between about 0 degrees and about 90 degrees. In some embodiments, the bias angle B is in a range of between about 20 degrees and about 70 degrees.

FIG.3is a cross-sectional view of a display system200according to an embodiment of the present disclosure. The display system200includes an illumination source210, a first liquid crystal assembly220, a second liquid crystal assembly230, and an article240.

The display system200defines mutually orthogonal X′, Y′ and Z′-axes. The X′ and Y′-axes are in-plane axes of the display system200, while the Z′-axis is a transverse axis disposed along a thickness of the display system200. In other words, the X′ and Y′-axes are disposed along a plane of the display system200, while the Z′-axis is perpendicular to the plane of the display system200. The illumination source210, the first liquid crystal assembly220, the second liquid crystal assembly230, and the article240of the display system200are disposed adjacent to each other along the Z′-axis.

The illumination source210is configured to emit light L1 over an emission surface211of the illumination source210. The illumination source210includes at least one light source215. The at least one light source215generates light that illuminates the display system200. In some embodiments, the at least one light source215includes one or more light emitters which emit light. The light emitters may be, for example, light emitting diodes (LEDs), fluorescent lights, or any other suitable light emitting device. The LEDs may be monochromatic, or may include a number of emitters operating at different wavelengths in order to produce a white light output. In the illustrated embodiment ofFIG.3, the at least one light source215is disposed at an edge surface of the illumination source210. In some other embodiments, the at least one light source215may be located proximate a longitudinal surface of the illumination source210.

The first liquid crystal assembly220is configured to selectively transmit and reflect light L1 received from the emission surface211of the illumination source210. In some embodiments, the first liquid crystal assembly220and the illumination source210are bonded together, for example, by means of an optically clear adhesive, epoxy, lamination, or any other suitable method of attachment. In some embodiments, the first liquid crystal assembly220includes a first liquid crystal panel222. In some embodiments, the first liquid crystal panel222includes a plurality of individually addressable pixels224. In some embodiments, the first liquid crystal assembly220is a monochrome display. In other words, the first liquid crystal assembly220does not include a color filter.

The second liquid crystal assembly230is configured to receive light L2 from the first liquid crystal assembly220and emit an image IM for viewing by a viewer V. The second liquid crystal assembly230includes a second liquid crystal panel232. In some embodiments, the second liquid crystal panel232includes a plurality of individually addressable pixels234. In some embodiments, the second liquid crystal assembly230is a color display. In other words, the second liquid crystal assembly230includes a color filter.

The second liquid crystal assembly230is disposed on the first liquid crystal assembly220. The second liquid crystal assembly230and the first liquid crystal assembly220are bonded to each other by means of the article240.

The article240is substantially similar to the article100ofFIG.1. However, the article240does not include the first release liner140and the second release liner150of the article100as shown inFIG.1.

A moiré effect and an optical interference may be observed when two similar lattices are overlapped. The moiré effect may result from the optical interference among two or more regular structures having different intrinsic frequencies. Since the plurality of individually addressable pixels224,234of the first liquid crystal panel222and the second liquid crystal panel232have regular pitch structures, there can be a possibility of a moiré effect between an image formed by the first liquid crystal assembly220and an image formed by the second liquid crystal assembly230.

By including the article240in the display system200, the optical interference and the moiré effect may be substantially reduced without affecting a brightness and a clarity of the display system200.

Referring toFIGS.1-3, the diffraction grating film102including the structured surface105or structured interface may provide useful optical effects. For example, the structured surface105may provide diffraction of a light that is transmitted through the article240. According to the present disclosure, a diffraction grating film (for example, the diffraction grating film102shown inFIG.1) may be selected to reduce moiré when included between two optically clear adhesive layers (for example, the first and second optically clear adhesive layers120,130shown inFIG.1). An article including the diffraction grating film and the two optically clear adhesive layers is placed over a display panel, or placed between a backlight and a display panel.

Referring toFIG.4, the present disclosure further provides a method300of manufacturing the article100shown inFIG.1for use with a display device. The method300may also be used to manufacture the article240for use with the display system200shown inFIG.3.

Referring toFIGS.1-4, at step302, the method300includes providing the diffraction grating film102including the base layer104and the plurality of microstructures106projecting from the base layer104. The base layer104defines the non-structured surface110of the diffraction grating film102and the plurality of microstructures106define the structured surface105of the diffraction grating film102opposite to the non-structured surface110.

The microstructures106may be formed on the base layer104by various methods, such as extrusion, cast-and-cure, coating, or some other method. In some cases, the microstructures106may be micro-replicated on the base layer104. A typical micro-replication process includes depositing a polymerizable composition onto a master negative microstructured molding surface in an amount barely sufficient to fill the cavities of the master. The cavities are then filled by moving a bead of the polymerizable composition between a preformed base or substrate layer (for example, the base layer104) and the master. The composition is then cured.

At step304, the method300includes providing the first optically clear adhesive layer120on the structured surface105of the diffraction grating film102.

At step306, the method300includes providing the second optically clear adhesive layer130on the non-structured surface110of the diffraction grating film102.

In some embodiments, the method300may include rotating the diffraction grating film102to the bias angle B after providing the first optically clear adhesive layer120and the second optically clear adhesive layer130on the diffraction grating film102. In some other embodiments, the method300may include rotating the diffraction grating film102to the bias angle B prior to providing the first optically clear adhesive layer120and the second optically clear adhesive layer130on the diffraction grating film102.

In some embodiments, the method300may include die cutting the diffraction grating film102to the bias angle B after providing the first optically clear adhesive layer120and the second optically clear adhesive layer130on the diffraction grating film102. In some other embodiments, the method300may include die cutting the diffraction grating film102to the bias angle B prior to providing the first optically clear adhesive layer120and the second optically clear adhesive layer130on the diffraction grating film102. In some embodiments, the bias angle B is in a range from about 20 degrees to about 70 degrees.

Examples

The present invention is more particularly described in the following examples that are intended as illustrations only, since numerous modifications and variations within the scope of the present invention will be apparent to those skilled in the art. Unless otherwise noted, all parts, percentages, and ratios reported in the following examples are on a weight basis. The following examples explain exemplary preparation of an article of the present disclosure. The examples will be explained with reference toFIGS.5A-5C and6A-6C.

Table 1 provided below lists some exemplary materials that are used for the preparation of different articles for comparison. G′ in Table 1 refers to the shear storage modulus of a corresponding material. Further, Tg in Table 1 refers to the glass transition temperature of the corresponding material.

Sample Preparation

Two sample articles were prepared without a diffraction grating film. Specifically, first and second control OCAs were prepared without a diffraction grating film. The first control OCA was prepared using a first adhesive and the second control OCA was prepared using a second adhesive. The first control OCA and the second control OCA were both 250 microns thick and were prepared by a polymerization process.

Sample articles S1 to S11 were prepared with each including a diffraction grating film. Sample articles S1 to S9 were prepared using a direct coating process. Sample articles S10 and S11 were prepared using a lamination process.

The direct coating process is illustrated inFIGS.5A-5C.FIGS.5A-5Cillustrate first, second, and third steps, respectively of the direct coating process.

In the first step, a liquid adhesive420and an easy liner440were coated on a structured surface405of a diffraction grating film402to obtain a thickness of 100 microns. The diffraction grating film402, the liquid adhesive420, and the easy liner440went through the polymerization process to obtain a first OCA-Grating Film sample480.

In the second step, a liquid adhesive430and a tight liner450were coated on a non-structured surface410of the diffraction grating film402of the first OCA-Grating Film sample480and went through the polymerization process to obtain a second OCA-Grating Film sample490.

In the third step, the second OCA-Grating Film sample490was cut into a bias angle B′ by a plotter to obtain an article400.

The lamination process is illustrated inFIGS.6A-6C.FIGS.6A-6Cillustrate first, second, and third steps, respectively of the lamination process.

In the first step, a diffraction grating film502was cut into a bias angle B″ by a plotter to obtain to obtain a biased diffraction grating film580.

In the second step, both sides of the biased diffraction grating film580were laminated with the first adhesive to obtain a laminated diffraction grating film590. Specifically, a structured surface505of the biased diffraction grating film580was laminated with a first optically clear adhesive layer520including the first adhesive and a first liner540. A non-structured surface510of the biased diffraction grating film580was laminated with a second optically clear adhesive layer530including the first adhesive and a second liner550.

In the third step, autoclave was applied to the laminated diffraction grating film590to obtain an article500.

Sample article S12 was prepared using a diffusion film, specifically, a high haze diffusion film. The first adhesive was laminated to both sides of the diffusion film.

Sample Evaluation

Optical performance and moiré were evaluated for the prepared samples.

Total transmittance %, haze % and clarity % were measured for evaluating optical performance of the prepared sample articles. The prepared sample articles were laminated to a glass and sandwiched with an additional glass (80 mm×50 mm×0.7 mm). Autoclave conditions were applied (50 degrees Celsius, 3 kg/cm2, 20 min). Further, total transmittance, haze and clarity of the prepared sample articles were measured by a haze meter (BYK haze-gard I).

For evaluating moiré, a light control film was placed on a display module to observe moiré effect. The prepared sample articles were tested.

Tables 2 and 3 below include some exemplary results of optical performance evaluation and moiré evaluation test of the prepared sample articles.

The sample articles S3-S7 and S11 showed no moiré. The sample articles S2 and S8 showed a reduced but substantial amount of moiré and high total transmittance and clarity. Sample article S12 also showed no moiré, but low total transmittance and clarity. The moiré was observed to be significantly reduced in sample articles including a diffraction grating film having a bias angle in a range from about 20 degrees to about 70 degrees without affecting brightness and clarity.