Patent Application
20080186428
This application claims priority from Japanese Patent Application Nos. 2007-027302 filed on Feb. 6, 2007 and 2007-185427 filed on Jul. 17, 2007. The entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates generally to optical apparatuses, image displays and liquid crystal displays.
2. Description of the Related Art
Recently, liquid crystal displays that control light emitted from a light source device such as a cold-cathode tube or a light-emitting diode (LED) using a liquid crystal panel to form images have been developed and put into practical use. In the above-mentioned liquid crystal display, a light guide plate is disposed to uniformly distribute light emitted from the light source device over the whole display surface. The light guide plate is disposed in parallel with the liquid crystal panel so as to allow them to be placed on top of each other, and on an optical path extending to the light source device. The light source device is disposed beside the light guide plate or on the opposite side to the liquid crystal panel of the light guide plate.
Furthermore, recently, in order to improve brightness of the screen of the liquid crystal display, a reflective polarizer may be disposed between the light guide plate and the liquid crystal panel. The reflective polarizer transmits light that has been polarized in a predetermined manner, and reflects light other than the transmitted light.
An example of conventional liquid crystal displays is shown in the sectional view in
In this liquid crystal display, light emitted by the cold-cathode tube 92 is adjusted with the light guide plate 91 so that a uniform in-plane brightness distribution is obtained, and then is emitted to the second polarizing plate 932 side. Furthermore, after the emitted light is controlled pixel by pixel in the liquid crystal layer 940, only light in a predetermined wavelength range (for example, each wavelength range of R, G, and B) is transmitted by the color filter 970. Thus a color display is obtained. Light polarized in a predetermined manner that is contained in light emitted from the light guide plate 91 is transmitted through the reflective polarizer 90 and then passes through the liquid crystal panel 94 to exit to the display side. On the other hand, light other than that polarized in the predetermined manner is reflected by the reflective polarizer 90, is reversed by the reflective layer 93, and then enters the reflective polarizer 90 again. The light reversed by the reflective layer 93 is transmitted this time through the reflective polarizer 90 and passes through the liquid crystal panel 94 to exit to the display side.
In the conventional liquid crystal display, however, colors between any two of R, G, and B (for example, yellow light in the wavelength range between the wavelength range of R and the wavelength range of G, and light in the wavelength range between the wavelength range of G and the wavelength range of B) other than R, G, and B are mixed in the emission spectrum of a cold cathode tube, and they are not filtered out sufficiently with color filters. As a result, there has been a problem in that the color reproducibility deteriorates in the display image quality.
An optical apparatus for a liquid crystal display has been proposed as a means for solving this problem. The optical apparatus contains a fluorescent material that absorbs yellow light (light in the wavelength range between the wavelength range of R and the wavelength range of G) with a wavelength of 575 to 605 nm and emits light of R with a wavelength of at least 610 nm, and this fluorescent material converts the yellow light contained in the emission spectrum of a light source into the light of R (see JP 2005-276586 A). For this optical apparatus, a method has been proposed in which a light guide plate or a light reflector contains the fluorescent material. Furthermore, for this optical apparatus, another method also has been proposed in which the fluorescent material is applied to the upper surface or end faces of the light guide plate or the surface of a light source.
However, in the method in which a light guide plate or a light reflector contains the fluorescent material, there is a problem in that the fluorescent material is present in some regions and absent in other regions in the light guide plate or the light reflector depending on the locations thereof, and thereby the wavelength distribution spectrum of the light emitted is not constant, which causes unevenness in color. Furthermore, in the method in which the fluorescent material is applied to, for example, the upper surface of the light guide plate, there is a problem in that in-plane unevenness in brightness occurs. Moreover, the optical apparatus lacks is not suitable for practical use as, for example, the configuration thereof becomes complicated.
The present invention therefore is intended to provide an optical apparatus that while preventing unevenness in color and brightness from occurring in an image display, can improve the color purity of transmitted light, can improve color reproducibility of the image display, and is excellent in practical use.
In order to achieve the above-mentioned object, an optical apparatus of the present invention includes:
a light source device;
a reflective layer;
a color purity improving sheet; and
a reflective polarizer,
wherein the color purity improving sheet includes a light-emitting layer containing a light-emitting means for improving purity of a color in a target wavelength range by absorbing light in a specific wavelength range other than the target wavelength range and then converting its wavelength to emit light in the target wavelength range,
light emitted from the light source device exits through the reflective polarizer to the outside,
the color purity improving sheet is disposed between the reflective polarizer and the reflective layer, and
the light source device is disposed in at least one location selected from a location between the color purity improving sheet and the reflective layer, a location between the reflective polarizer and the color purity improving sheet, and a location on the opposite side to the color purity improving sheet side of the reflective layer.
An image display of the present invention includes:
an optical apparatus, and
a display panel,
wherein the display panel including a display layer and a color filter,
wherein the display panel and the optical apparatus being disposed so that the display layer is located between the color filter and the optical apparatus, and
wherein light emitted from the optical apparatus passes through the display layer and then enters the color filter,
wherein the optical apparatus is an optical apparatus of the present invention described above.
A liquid crystal display of the present invention includes:
an optical apparatus, and
a liquid crystal panel,
with the liquid crystal panel including a liquid crystal layer and a color filter,
with the liquid crystal panel and the optical apparatus being disposed so that the liquid crystal layer is located between the color filter and the optical apparatus, and
with light emitted from the optical apparatus passes through the liquid crystal layer and then enters the color filter,
wherein the optical apparatus is an optical apparatus of the present invention described above.
In the optical apparatus of the present invention, the light-emitting means is contained in a single sheet (a light-emitting layer). Accordingly, in the optical apparatus of the present invention, the light-emitting means can be distributed uniformly in a sheet (light-emitting layer). As a result, the optical apparatus of the present invention makes it possible to improve the color purity of transmitted light while preventing unevenness in color and brightness from occurring. In the optical apparatus of the present invention, a color purity improving sheet including the light-emitting layer is disposed between the reflective polarizer and the reflective layer. In this case, at least a part of the light transmitted through the color purity improving sheet is reflected by the reflective polarizer or the reflective layer and then enters the color purity improving sheet again. Thus, in the optical apparatus of the present invention, since there is light that enters the color purity improving sheet repeatedly, the light wavelength conversion efficiency improves and the color purity further improves. As a result, with the optical apparatus of the present invention, the color reproducibility of the image display also can be improved. Moreover, with the optical apparatus of the present invention, the color purity can be improved by, for example, merely disposing the optical apparatus in a liquid crystal display. Thus, it is excellent in practical use.
In the present invention, “improvement in color purity” embraces, for example, conversion of yellow light, which is a color between R and G, into light of R or G, conversion of light of a color between G and B into light of G, and/or conversion of light of any of R, G, and B into light of a color other than R, G, and B.
In the optical apparatus of the present invention, it is preferable that the light source device be disposed between the color purity improving sheet and the reflective layer.
In the optical apparatus of the present invention, it is preferable that the light-emitting layer be formed of a matrix polymer and a fluorescent material.
In the optical apparatus of the present invention, examples of the fluorescent material include fluoresceins, rhodamines, coumarins, dansyls (dimethylaminonaphthalenesulfonic acids), 7-nitrobenzo-2-oxa-1,3-diazol (NBD) dyes, pyrene, perylene, phycobiliprotein, cyanine pigment, anthraquinone, thioindigo, and benzopyran fluorescent materials. One of the fluorescent materials can be used individually or two or more of them can be used in combination.
In the optical apparatus of the present invention, it is preferable that the fluorescent material be a perylene fluorescent material.
In the optical apparatus of the present invention, it is preferable that the perylene fluorescent material be represented by the following structural formula (1):
where four Xs each are a halogen group or an alkoxy group, the respective Xs can be identical to or different from one another, and two Rs each are an aryl group or an alkyl group, the respective Rs can be identical to or different from each other.
In the optical apparatus of the present invention, it is preferable that the fluorescent material be a thioindigo fluorescent material.
In the optical apparatus of the present invention, it is preferable that the thioindigo fluorescent material be represented by the following structural formula (2):
In the optical apparatus of the present invention, it is preferable that the fluorescent material be an anthraquinone fluorescent material.
In the optical apparatus of the present invention, it is preferable that the anthraquinone fluorescent material be represented by the following structural formula (3):
In the optical apparatus of the present invention, examples of the matrix polymer include polymethylmethacrylate, polyacrylic resin, polycarbonate resin, polynorbornene resin, polyvinyl alcohol resin, and cellulose resin. One of the matrix polymers may be used individually or two or more of them may be used in combination.
In the optical apparatus of the present invention, it is preferable that the matrix polymer be polymethylmethacrylate.
In the optical apparatus of the present invention, the specific wavelength range of light that is absorbed by the light-emitting layer is not particularly limited, and it can be, for example, in the range of 560 to 610 nm. The target wavelength range of light emitted by the light-emitting layer is not particularly limited, and it can be, for example, in the range of 610 to 700 nm.
Preferably, the optical apparatus of the present invention further includes a light guide plate, and light emitted from the light source device exits to the reflective polarizer side through the light guide plate.
Next, the optical apparatus of the present invention is described using examples.
As described above, the optical apparatus of the present invention includes a light source device, a reflective layer, a color purity improving sheet, and a reflective polarizer. In the optical apparatus of the present invention, for example, as shown in
The reflective polarizer to be employed herein can be, for example, an arbitrary suitable film that separates linearly polarized light from natural light or polarized light. Examples of the film that separates the linearly polarized light include a film that transmits one of linearly polarized lights orthogonal in the axis direction and reflects the other. Specific examples of such a reflective polarizer include a grid polarizer, a multilayer thin film laminate including at least two layers made of at least two types of materials having a difference in refractive index from each other, a vapor-deposited multilayer thin film having different refractive indices, which is used, for example, for a beam splitter, and one obtained by stretching a resin laminate including at least two layers made of at least two types of resins having a difference in refractive index from each other. More specifically, the reflective polarizer to be used herein can be, for example, one obtained by uniaxially stretching a multilayer laminate formed by alternately laminating a resin that exhibits less phase difference (for example, norbornene resin such as one of a series of “ARTON” (trade name) manufactured by JSR Corporation) and a material that exhibits a phase difference through stretching (for example, polyethylene naphthalate, polyethylene terephthalate (PET), or polycarbonate) or acrylic resin (for example, polymethylmethacrylate). A commercially available reflective polarizer is, for example, as “DBEF” (trade name) manufactured by Sumitomo 3M Limited. The thickness of the reflective polarizer is not particularly limited and is, for example, in the range of 50 to 200 μm.
The color purity improving sheet has a light-emitting layer including the light-emitting means that improves the purity of the color in the target wavelength range by absorbing light (light of an unnecessary color) in a specific wavelength range other than the target wavelength range, converting its wavelength, and then emitting light (light of a required color) in the target wavelength range.
It is preferable that the light-emitting means contain a fluorescent material. Examples of the fluorescent material are as described above.
Specific examples of the fluorescent material include “Lumogen F Red 305 (perylene)” (trade name) manufactured by BASF AG, “Plast Red 8355 and 8365 (anthraquinone), Plast Red D-54 (thioindigo), Plast Red DR-426 and DR-427 (benzopyran)” (trade names) manufactured by Arimoto Chemical Co., Ltd., and “NK-1533 (carbocyanine dye)” (trade name) manufactured by Hayashibara Biochemical Labs., Inc. These fluorescent materials absorb yellow light (with a wavelength of 560 to 610 nm), which is a color between R and G, and emit light (with a wavelength of 610 to 650 nm) of R.
As described above, it is preferable that the perylene fluorescent material be represented by the structural formula (1). The absorption spectrum of the fluorescent material represented by the structural formula (1) is shown in the graph in
As described above, it is preferable that the thioindigo fluorescent material be represented by the structural formula (2). The absorption spectrum of the fluorescent material represented by the structural formula (2) is shown in the graph in
As described above, it is preferable that the anthraquinone fluorescent material be represented by the structural formula (3). The absorption spectrum of the fluorescent material represented by the structural formula (3) is shown in the graph in
As described above, it is preferable that the light-emitting layer be formed of a matrix polymer and a fluorescent material. The light-emitting layer can be produced by, for example, mixing the fluorescent material with a matrix polymer capable of being formed into a film and then forming the mixture into a film. Preferably, the matrix polymer has high transparency and examples thereof include polyacrylic resins such as polymethylmethacrylate, polyethyl acrylate, and polybutyl acrylate; polycarbonate resins such as polyoxycarbonyloxyhexamethylene, and polyoxycarbonyloxy-1,4-isopropylidene-1,4-phenylene, polynorbornene resins, polyvinyl alcohol resins such as polyvinyl formal, polyvinyl acetal, and polyvinyl butyral; and cellulose resins such as methylcellulose, ethylcellulose, and derivatives thereof. Among them, polymethylmethacrylate is preferred. One of the matrix polymers may be used individually or two or more of them may be used in combination.
The abovementioned term “polynorbornene resins” denotes (co)polymers obtained with a norbornene monomer having a norbornene ring used for a part or all of a starting material (a monomer). The term “(co)polymers” denotes homopolymers or copolymers.
Next, the method of forming the light-emitting layer is described using an example but is not limited to the example.
First, the matrix polymer is dissolved in a solvent and thereby a polymer solution is prepared. Examples of the solvent to be used herein include toluene, methyl ethyl ketone, cyclohexanone, ethyl acetate, ethanol, tetrahydrofuran, cyclopentanone, and water.
Next, the fluorescent material is added to and dissolved in the polymer solution. The amount of the fluorescent material to be added can be determined suitably according to the type of the fluorescent material. With respect to 100 parts by weight of the matrix polymer, it can be, for example, in the range of 0.01 to 80 parts by weight, preferably in the range of 0.1 to 50 parts by weight, and more preferably in the range of 0.1 to 30 parts by weight.
Subsequently, the polymer solution to which the fluorescent material has been added is applied onto a substrate to form a coating film, which is then dried by heating. Thus, a film is formed.
Next, the film is separated from the substrate and thereby the light-emitting layer can be obtained. The thickness of the light-emitting layer is not particularly limited. It is, for example, in the range of 0.1 to 1000 μm, preferably in the range of 1 to 200 μm, and more preferably in the range of 2 to 50 μm.
The color purity improving sheet may have any structure as long as it includes the light-emitting layer. For example, the color purity improving sheet may be composed of the light-emitting layer alone. Furthermore, the color purity improving sheet may include something other than the light-emitting layer.
The light source device is not particularly limited. Examples thereof include a cold-cathode tube and a light-emitting diode (LED).
The type and the material of the reflective layer are not particularly limited, for example. Preferably, the reflective layer is formed of a material with a high optical reflectance. Examples of the material include a plastic film or sheet that has a silver sputtered layer, a silver deposited layer, or a high optical reflectance ink layer. The thickness of the reflective layer is not particularly limited and is, for example, in the range of 100 to 500 μm.
An example of the configuration of an optical apparatus of the present invention is shown in the sectional view in
Improvement in color purity of the optical apparatus of the present invention is described using the optical apparatus shown in
As described above, the optical apparatus of the present invention further includes a light guide plate. In the optical apparatus of the present invention, light emitted from the light source device may be allowed to exit to the reflective polarizer side through the light guide plate.
The optical apparatus of the present invention further may include another component, examples of which include a diffuser plate and a prism sheet. It can be disposed, for example, between any adjacent components of the respective components (for example, between the reflective polarizer and the color purity improving sheet or between the color purity improving sheet and the light guide plate).
The optical apparatus of the present invention can be used suitably for various image displays such as liquid crystal displays (LCDs) and EL displays (ELDs). The optical apparatus of the present invention may be formed monolithically with an image display or may be configured as a separate apparatus. An example of the configuration of a liquid crystal display of the present invention is shown in the sectional view in
Another example of the configuration of the liquid crystal display according to the present invention is shown in the sectional view in
In the liquid crystal display (optical apparatus 101) shown in
Still another example of the configuration of the liquid crystal display according to the present invention is shown in the sectional view in
In the liquid crystal display (optical apparatus 102) shown in
Next, examples of the present invention are described. The present invention is neither limited nor restricted by the following examples by any means. In the respective examples, a light of R alone was necessary and lights other than that were unnecessary.
A fluorescent material (“Lumogen F Red 305” (trade name), manufactured by BASF Corporation) represented by the aforementioned structural formula (1) was added to and dissolved in 30% by weight toluene solution of polymethyl methacrylate so as to be 0.19% by weight with respect to polymethyl methacrylate. This solution was applied onto a PET film base material, which had been subjected to a treatment for separation, with an applicator to form a coating film. This was dried at 80° C. for 30 minutes. Thus, a film was obtained. After drying, the film was separated from the PET film base material and thereby a color purity improving sheet composed of a 30-μm thick light-emitting layer alone was obtained.
The color purity improving sheet 11 was mounted onto a liquid crystal display including an optical apparatus 100 in the manner as shown in
The emission spectrum was measured in the same manner as in Example 1 except that the color purity improving sheet 11 was mounted onto a liquid crystal display including an optical apparatus 101 in the manner as shown in
The emission spectrum was measured in the same manner as in Example 2 except that the color purity improving sheet 11 was mounted between the prism sheet 22 and the diffuser plate 23.
The emission spectrum was measured in the same manner as in Example 2 except that the color purity improving sheet 11 was mounted between the diffuser plate 23 and the light guide plate 21.
A fluorescent material (“Plast Red D-54” (trade name), manufactured by Arimoto Chemical Co., Ltd.) represented by the aforementioned structural formula (2) was added to and dissolved in 30% by weight toluene solution of polymethyl methacrylate so as to be 0.21% by weight with respect to polymethyl methacrylate. This solution was applied onto a PET film base material, which had been subjected to a treatment for separation, with an applicator to form a coating film. This was dried at 80° C. for 30 minutes. Thus, a film was obtained. After drying, the film was separated from the PET film base material and thereby a color purity improving sheet composed of a 63-μm thick light-emitting layer alone was obtained.
The emission spectrum was measured in the same manner as in Example 1 except that the color purity improving sheet 11 was mounted onto the liquid crystal display including an optical apparatus 102 in the manner as shown in
The emission spectrum was measured in the same manner as in Example 5 except that the color purity improving sheet 11 was mounted between the second diffuser plate 23b and the third diffuser plate 23c.
The emission spectrum was measured in the same manner as in Example 5 except that the color purity improving sheet 11 was mounted between the third diffuser plate 23c and the light guide plate 21.
A fluorescent material (“Plast Red 8355” (trade name), manufactured by Arimoto Chemical Co., Ltd.) represented by the aforementioned structural formula (3) was added to and dissolved in 30% by weight toluene solution of polymethyl methacrylate so as to be 0.19% by weight with respect to polymethyl methacrylate. This solution was applied onto a PET film base material, which had been subjected to a treatment for separation, with an applicator to form a coating film. This was dried at 80° C. for 30 minutes. Thus, a film was obtained. After drying, the film was separated from the PET film base material and thereby a color purity improving sheet composed of a 31-μm thick light-emitting layer alone was obtained.
The emission spectrum was measured in the same manner as in Example 1 except that the color purity improving sheet 11 was mounted onto the liquid crystal display including an optical apparatus 102 in the manner as shown in
The emission spectrum was measured in the same manner as in Example 8 except that the color purity improving sheet 11 was mounted between the second diffuser plate 23b and the third diffuser plate 23c.
The emission spectrum was measured in the same manner as in Example 8 except that the color purity improving sheet 11 was mounted between the third diffuser plate 23c and the light guide plate 21.
The emission spectrum was measured in the same manner as in Example 1 except that the color purity improving sheet 11 was mounted on the first polarizing plate 231.
The emission spectrum was measured in the same manner as in Example 1 except that the color purity improving sheet 11 was mounted between the second polarizing plate 232 and the diffuser plate 23.
Reference Example 3
The emission spectrum was measured in the same manner as in Example 2 except that the color purity improving sheet 11 was mounted between the second polarizing plate 232 and the reflective polarizer 10.
The emission spectrum was measured in the same manner as in Example 5 except that the color purity improving sheet 11 was mounted between the second polarizing plate 232 and the reflective polarizer 10.
The emission spectrum was measured in the same manner as in Example 8 except that the color purity improving sheet 11 was mounted between the second polarizing plate 232 and the reflective polarizer 10.
Results of emission spectrum measurement in Examples 1 to 4 and Reference Examples 1 to 3 are indicated in
As can be understood from Table 1 above and
As described above, while preventing unevenness in color and brightness from occurring in an image display, the optical apparatus of the present invention can improve the color purity of transmitted light and can improve color reproducibility of the image display. The optical apparatus of the present invention and an image display including the same can be used, for example, for office equipment such as a desktop PC, a notebook PC, and a copy machine, portable devices such as a cell phone, a watch, a digital camera, a personal digital assistant (PDA), and a handheld game machine, home electric appliances such as a video camera, a television set, and a microwave oven, vehicle equipment such as a back monitor, a monitor for car-navigation systems, and a car audio, display equipment such as an information monitor for stores, security equipment such as a surveillance monitor, and care and medical equipment such as a monitor for care and a monitor for medical use. However, the uses thereof are not limited and they are applicable to a wide field.
The invention may be embodied in other forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed in this application are to be considered in all respects as illustrative and not limiting. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-027302 | Feb 2007 | JP | national |
| 2007-185427 | Jul 2007 | JP | national |
