Patent Application
20130027642
This application claims the benefit of Korean Patent Application No. 10-2011-0074168 filed on Jul. 26, 2011, the contents of which are herein incorporated by reference in their entirety.
1. Field of Disclosure
The present invention relates to an optical film, a method of manufacturing the same, and a display apparatus having the same. More particularly, the present invention relates to an optical film capable of increasing the brightness of light provided to a display panel, a method of manufacturing the optical film, and a display apparatus having the same.
2. Description of the Related Art
In general, a liquid crystal display includes a display panel displaying an image with a liquid crystal layer and a backlight unit providing light to the display panel. Since the display panel represents a gray scale using an anisotropic characteristic of liquid crystals included in the liquid crystal layer, the liquid crystal display further includes a linear polarizing plate disposed between the display panel and the backlight unit.
However, the linear polarizing plate transmits about 50% of the light that is not polarized and absorbs about 50% of the light not polarized, so that about 50% of the light provided from the backlight unit is provided to the display panel to be used to display the image. Accordingly, light utilization efficiency of the liquid crystal display is lowered and the liquid crystal display does not to provide the image having a relatively high brightness.
Exemplary embodiments of the present invention provide an optical film capable of increasing brightness of the light provided to a display panel.
Other exemplary embodiments of the present invention provide methods of manufacturing the optical film.
Exemplary embodiments of the present invention provide a display apparatus that includes the optical film.
According to certain exemplary embodiments, an optical film includes a base film, a plurality of thin film patterns, and a plurality of cholesteric liquid crystals.
The thin film patterns are disposed on the base film to be spaced apart from each other and have a first property corresponding to one of a hydrophilic property and a hydrophobic property. The cholesteric liquid crystals have the first property and are respectively disposed on the thin film patterns to transmit one of a right-circularly polarized light and a left-circularly polarized light and reflect the other one of the right-circularly polarized light and the left-circularly polarized light.
According to the exemplary embodiments, a display apparatus includes a light source unit emitting a light, a display panel, and an optical film.
The display panel receives the light and controls a transmittance of the light to display an image. The optical film is disposed between the light source unit and the display panel and includes a base film, a plurality of thin film patterns, and a plurality of cholesteric liquid crystals.
The thin film patterns are disposed on the base film to be spaced apart from each other and have a first property corresponding to one of a hydrophilic property and a hydrophobic property. The cholesteric liquid crystals have the first property and are respectively disposed on the thin film patterns to transmit one of a right-circularly polarized light and a left-circularly polarized light and reflect the other one of the right-circularly polarized light and the left-circularly polarized light.
According to the exemplary embodiments, a method of manufacturing an optical film is provided as follows.
A plurality of thin film patterns are formed on a base film to be spaced apart from each other. The thin film patterns each have a first property corresponding to one of a hydrophilic property and a hydrophobic property. Cholesteric liquid crystals are then formed on each of the thin film patterns. The cholesteric liquid crystals initially include a reactive mesogen and represent a blue color. Light is subsequently non-uniformly irradiated onto the cholesteric liquid crystals to change a part of the cholesteric liquid crystals to a red cholesteric liquid crystal representing a red color, or to a green cholesteric liquid crystal representing a green color.
In an optical film manufactured according to the above method, the light provided from the light source unit may be provided to the display panel without loss of the light. Thus, the light utilization efficiency of the display apparatus may be improved, the power consumption in the display apparatus may be reduced, and the display apparatus may provide observers with the image having a high brightness.
The above and other advantages of the present invention will become readily apparent by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:
It will be understood that when an element or layer is referred to as being “on”, “connected to” or “coupled to” another element or layer, it can be directly on, connected or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.
Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms, “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes” and/or “including”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Unless otherwise defined, all terms (including 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. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Hereinafter, the present invention will be explained in detail with reference to the accompanying drawings.
Referring to
The display panel 100 includes a first substrate 110, a second substrate 120 facing the first substrate 110, and a liquid crystal layer 130 disposed between the first and second substrates 110 and 120. The liquid crystal layer 130 may include twisted nematic liquid crystals, vertically aligned liquid crystals, or cholesteric liquid crystals.
Although not shown in
The backlight unit 171 includes a light source 190 emitting the light, a light guide plate 170 guiding the light to the display panel 100, and a light source cover 191 covering the light source 190 to allow the light emitted from the light source 190 to travel to the light guide plate 170. The light source 190 may be a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), or a hot cathode fluorescent lamp (HCFL), etc.
The light guide plate 170 is disposed adjacent to the light source 190 to guide the light emitted from the light source 190 to the display panel 100. To this end, the light guide plate 170 has a thickness that gradually increases as it is closer to the light source 190.
The display apparatus 10 further includes a first polarizing plate 141 and a second polarizing plate 142 facing the first polarizing plate 141. Each of the first and second polarizing plates 141 and 142 transmits a light polarized in a specific direction and absorbs a light polarized in a direction substantially perpendicular to the specific direction. The first and second polarizing plates 141 and 142 may be formed of polyvinyl alcohol (PVA). A transmission axis of the first polarizing plate 141 may be substantially parallel to or perpendicular to a transmission axis of the second polarizing plate 142 according to the liquid crystal layer 130 employed to the display panel 100.
In
Referring to
The optical film 160 transmits one of a right-circularly polarized light and a left-circularly polarized light and reflects the other one of the right-circularly polarized light and the left-circularly polarized light.
The reflection plate 180 includes a material having a high light reflectance and reflects the light incident thereto to the display panel 100. The reflection plate 180 may be a metal material having a superior light reflectance. The retardation plate 150 converts the circularly polarized light into the linearly polarized light. The circularly polarized light is changed into the linearly polarized light. In the present exemplary embodiment, the retardation plate 150 may be a quarter-wave plate.
The optical film 160, the reflection plate 180, and the retardation plate 180 effectively provides the light exiting from the light guide plate 170 to the display panel 100, thereby improving the light utilization efficiency. In detail, referring to
Hereinafter, as shown in
Since the optical film 160 transmits the left-circularly polarized light of the first light L1, the left-circularly polarized light transmitted through the optical film 160 is provided to the retardation plate 150 as a second light L2. In addition, the optical film 160 reflects the right-circularly polarized light component of the first light L1, and thus the right-circularly polarized light reflected by the optical film 160 travels to the reflection plate 180 as a third light, L3.
The third light, L3 is reflected by the reflection plate 180 and provided again to the optical film 160. L3 is converted into a left-circularly polarized light when it is reflected by the reflection plate 180. That is, the phase of the third light, L3 is changed by 180 degrees when being reflected by the reflection plate 180. Accordingly, a right-circularly polarized light incident to the reflection plate 180 is converted into a left-circularly polarized light when being reflected by the reflection plate 180 and vice versa, and the third light L3 that is right-circularly polarized light is converted into a third light L3′ that is left-circularly polarized light.
The left-circularly polarized third light L3′ is transmitted through the optical film 160, and as a result the second light L2 and the third light L3′, originating from the first light L1, are transmitted through the optical film 160. Similarly, the right-circularly polarized light originating from L1 is transmitted through the optical film 160 or reflected and transmitted through the optical film 160. Thus, the light emitted from the light source 190 may be transmitted through the optical film 160 without loss of the light.
The second light L2 of the left-circularly polarized light and the third light L3′ of the left-circularly polarized light are provided to the retardation plate 150, so that the second light L2 and the third light L3′ are converted into the second light L2′ and the third light L3″ as the linearly polarized lights. The retardation film 150 may be the quarter-wave plate and change the phase of the light incident thereto by about 90 degrees, thereby changing the circularly polarized light into the linearly polarized light. Thus, the light transmitted through the retardation plate 150 becomes the light polarized in the specific direction, and the linearly polarized second and third lights L2′ and L3″ are provided to the display panel 100.
In other words, the optical film 160, the reflection plate 180, and the retardation plate 150 may polarize the light, which is not polarized, in the specific direction without the loss of the light and provide the polarized light to the display panel 100, thereby improving the light utilization efficiency.
Referring to
The base film 210 may be polyethylene terephthalate (PET), polyethylene naphthalate (PEN), fiber reinforced plastic (FRP), or glass. In addition, the base film 210 may include a hydrophobic material or a surface of the base film 210 may be subjected to modification treatment to have hydrophobic property.
The thin film patterns 220 are disposed on the base film 210 to be spaced apart from each other. The thin film patterns 220 may include a hydrophilic material, such as indium tin oxide (ITO), indium zinc oxide (IZO), etc.
An alignment layer 230 is disposed on the base film 210 to cover the thin film patterns 220 to define an alignment direction of the liquid crystals, and the alignment layer 230 may be vertically aligned or horizontally aligned.
The alignment layer 230 may be formed of at least one of eight materials (“a” to “h”) shown below, or binding materials of these eight materials.
The cholesteric liquid crystals 240 are disposed on the alignment layer 230 so as to correspond in position to the thin film patterns 220. The cholesteric liquid crystals 240 may be formed in a left- or right-handed helical structure according to the amount of chiral dopant added to the cholesteric liquid crystals.
In detail, in the case that the cholesteric liquid crystals 240 are formed in a left-handed helical structure, the cholesteric liquid crystals 240 having the left-handed helical structure transmit the left-circularly polarized light and reflect the right-circularly polarized light. Alternatively, in the case when the cholesteric liquid crystals 240 are formed in a right-handed helical structure, the cholesteric liquid crystals 240 having a right-handed helical structure transmit the right-circularly polarized light and reflect the left-circularly polarized light.
The cholesteric liquid crystals 240 include a red cholesteric liquid crystal R representing a red color, a green cholesteric liquid crystal G representing a green color, and a blue cholesteric liquid crystal B representing a blue color. The red, green, and blue cholesteric liquid crystals R, G, and B transmit or reflect red, green, and blue lights, respectively. In detail, the red cholesteric liquid crystal R transmits one of a red right-circularly polarized light and a red left-circularly polarized light and reflects the other one of the red right-circularly polarized light and the red left-circularly polarized light. The green cholesteric liquid crystal G transmits one of a green right-circularly polarized light and a green left-circularly polarized light and reflects the other one of the green right-circularly polarized light and the green left-circularly polarized light. The blue cholesteric liquid crystal B transmits one of a blue right-circularly polarized light and a blue left-circularly polarized light and reflects the other one of the blue right-circularly polarized light and the blue left-circularly polarized light.
One of the red, green, and blue cholesteric liquid crystals R, G, and B is disposed on the alignment layer 230 to corresponding to one of the thin film patterns 220. In other words, each of the cholesteric liquid crystals 240 disposed on a corresponding thin film pattern of the thin film patterns 220 represents one of the red, green, and blue colors.
Since the cholesteric liquid crystals 240 have the hydrophilic property and portions of the alignment layer 230, on which the thin film patterns 220 are not formed, have the hydrophobic property, the cholesteric liquid crystals 240 may be concentrated on areas respectively corresponding to the thin film patterns 220 when the cholesteric liquid crystals 240 are formed on the alignment layer 230 by an inkjet method. The method of allowing the cholesteric liquid crystals 240 to represent the red, green, and blue colors will be described in detail with reference to
The cholesteric liquid crystals 240 are obtained by adding at least one of chiral dopants as shown in Table 1 below into liquid crystal molecules having a positive dielectric anisotropy or a negative dielectric anisotropy.
In addition, in order to change the pitch of the cholesteric liquid crystals 240 using ultraviolet light, a functional group, e.g., acrylate
is included as a reactant to engage in a polymerization reaction at one end or both ends of the molecular structure of one or more of the dopants.
A capping layer 250 may be disposed on the cholesteric liquid crystals 240 to cover the cholesteric liquid crystals 240 and fix the cholesteric liquid crystals 240 to the alignment layer 230.
Referring to
Referring to
When the cholesteric liquid crystals 240 are formed in the perfect planar texture, a front visibility becomes high, but a side visibility becomes low. On the contrary, when the cholesteric liquid crystals 240 are formed in the imperfect planar texture, the front visibility becomes low, but the side visibility becomes high when compared to those of the perfect planar texture.
Referring to
That is, in the case that the base film 210 is difficult to have the hydrophobic property, the transparent layer 260 having the hydrophobic property may be further formed on the base film 210 as shown in
Referring to
In detail, the cholesteric liquid crystals 240 and the thin film patterns 220 may have a first property corresponding to either the hydrophilic property or the hydrophobic property. In the case that the cholesteric liquid crystals 240 and the thin film patterns 220 have the first property, the base film 210 and the transparent layer 260 may have a second property corresponding to either the hydrophilic property or the hydrophobic property, which is different from the first property. Thus, when the cholesteric liquid crystals 240 and the thin film patterns 220 have the first property and the base film 210 and the transparent layer 260 have the second property, the cholesteric liquid crystals 240 may be disposed respectively corresponding to the thin film patterns 220 as shown in
Referring to
Referring to
The barrier walls 270 are disposed in the areas in which the cholesteric liquid crystals 240 are not formed in a plan view, thereby preventing the movement of the cholesteric liquid crystals 240 and preventing the lights respectively transmitting the adjacent two cholesteric liquid crystals 240 from mixing with each other. Accordingly, the barrier walls 270 may improve the side visibility of the optical film 160.
Referring to
Although not shown in
Referring to
Then, the blue cholesteric liquid crystal B is formed on the alignment layer 230 to correspond to each of the thin film patterns 220. The blue cholesteric liquid crystal B may be formed on the alignment layer 230 by the inkjet method using an inkjet device 300.
Although not shown in
Referring to
The mask MA includes a first area A1, a second area A2, and a third area A3. An opening is formed in the first area A1, a slit pattern is formed in the second area A2, and the opening or the slit pattern is not formed in the third area A3 to block the light incident thereto.
The first area A1 corresponds to an area with the blue cholesteric liquid crystal B that will be changed to the red cholesteric liquid crystal R, the second area A2 corresponds to an area with the blue cholesteric liquid crystal B that will be changed to the green cholesteric liquid crystal G, and the third area A3 corresponds to an area with the remaining blue cholesteric liquid crystals B.
In
Referring to
In detail, the blue cholesteric liquid crystal disposed in the first area A1 among the blue cholesteric liquid crystals B is exposed to the largest amount of the light, so that the chirality of the blue cholesteric liquid crystal in the first area A1 is relatively largely reduced. As a result, the blue cholesteric liquid crystal in the first area A1 is changed to a long-pitch cholesteric liquid crystal, and thus the blue cholesteric liquid crystal in the first area A1 is changed to the red cholesteric liquid crystal R as shown in
In addition, the blue cholesteric liquid crystal disposed in the second area A2 among the blue cholesteric liquid crystals B is exposed to the amount of the light, which is smaller than the amount of the light passing through the first area A1, so that the reduction of the chirality of the blue cholesteric liquid crystal in the second area A2 is relatively small when compared to the reduction of the chirality of the blue cholesteric liquid crystal in the first area A1. As a result, the blue cholesteric liquid crystal in the second area A2 is changed to a cholesteric liquid crystal having a pitch between the red cholesteric liquid crystal R and the blue cholesteric liquid crystal B, and thus the blue cholesteric liquid crystal in the second area A2 is changed to the green cholesteric liquid crystal G as shown in
The blue cholesteric liquid crystal disposed in the third area A3 among the blue cholesteric liquid crystals B is not exposed to the light, so the blue cholesteric liquid crystal in the third area A3 is maintained in the blue cholesteric liquid crystal.
The capping layer 250 may be further formed on the cholesteric liquid crystals 240 to cover the cholesteric liquid crystals 240. The capping layer 250 prevents the movement of the cholesteric liquid crystals 240 and fixes the cholesteric liquid crystals 240 to the optical film 160. The capping layer 250 may include parlyrene and may be formed on the cholesteric liquid crystals 240 by a chemical vapor deposition method.
Referring to
In
Although the exemplary embodiments of the present invention have been described, it is understood that the present invention should not be limited to these exemplary embodiments but various changes and modifications can be made by one ordinary skilled in the art within the spirit and scope of the present invention as hereinafter claimed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2011-0074168 | Jul 2011 | KR | national |
