JP2008129292A - Color purity improving sheet, optical device, image display device, liquid crystal display device and solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color purity improving sheet excellent in practicality, the sheet capable of improving color purity of light transmitting through the sheet while preventing the occurrence of color irregularity and luminance irregularity. <P>SOLUTION: The color purity improving sheet has a light emitting layer containing a light emitting means that improves color purity in a target wavelength band by absorbing and converting wavelengths of light in a specified wavelength band except for a target wavelength band and emitting light in the target wavelength band. Since the light emitting means can be uniformly distributed in the sheet by forming the sheet as a single sheet having the light emitting layer, the color purity of light transmitting the sheet can be improved while preventing the occurrence of color irregularity and luminance irregularity. By using the above color purity improving sheet, for example, color purity of a liquid crystal display device can be improved by only disposing the sheet in the device, and the sheet therefore is excellent in practicality. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a color purity improving sheet, an optical device, an image display device, a liquid crystal display device, and a solar cell.

It is well known that light emitted from sunlight or an artificial light source is a mixture of light of various colors (wavelengths). For example, when such light is used in a device such as a liquid crystal display (LCD) or a solar cell, not all colors (wavelengths) are used. For this reason, from the viewpoint of energy efficiency, a device has been devised that converts unnecessary color (wavelength) light into necessary color (wavelength) light. For example, for LCDs that convert unnecessary light (yellow with a wavelength of 575 to 605 nm) out of light emitted from a light source into light of a required color (red with a wavelength of 610 nm or more) using a fluorescent material. An optical device has been proposed (see Patent Document 1). In this optical apparatus, a method in which the fluorescent material is contained in a light guide plate or a reflection plate has been proposed. In this optical apparatus, a method of applying the fluorescent material to the upper surface or end surface of the light guide plate or the surface of the light source has been proposed. However, in the method in which the fluorescent material is contained in the light guide plate or the reflection plate, there are portions where the fluorescent material exists and portions where the fluorescent material is not present depending on the position of the light guide plate or the reflection plate, and the wavelength distribution spectrum of the emitted light is not constant. There was a problem that uneven color occurred. In addition, the method of applying the fluorescent material to the upper surface of the light guide plate has a problem that uneven luminance occurs in the surface. Furthermore, the light source device lacks practicality because its structure is complicated.
JP 2005-276586 A

  Accordingly, an object of the present invention is to provide a color purity improving sheet that is capable of improving the color purity of transmitted light while preventing the occurrence of color unevenness and brightness unevenness and is excellent in practicality.

  In order to achieve the above object, the color purity improving sheet of the present invention absorbs light in a specific wavelength band other than the target wavelength band, converts the wavelength, and emits light in the target wavelength band, thereby generating a color in the target wavelength band. It has a light emitting layer including a light emitting means for improving purity.

  The image display device of the present invention is an image display device including a color purity improving sheet, wherein the color purity improving sheet is the color purity improving sheet of the present invention.

  The liquid crystal display device of the present invention is a liquid crystal display device including a color purity improving sheet, wherein the color purity improving sheet is the color purity improving sheet of the present invention.

  The solar cell of the present invention is a solar cell including a color purity improving sheet, wherein the color purity improving sheet is the color purity improving sheet of the present invention.

  The color purity improving sheet of the present invention is not provided on a constituent member such as a light guide plate or a reflecting plate as in a conventional optical device, but is a single sheet. In this way, the color purity improving sheet of the present invention absorbs light in a specific wavelength band (unnecessary color light) other than the target wavelength band and converts the wavelength to light in the target wavelength band (light of the required color). By using a single sheet having a light emitting layer including a light emitting means that improves the purity of the color in the target wavelength band by emitting light, the light emitting means can be uniformly distributed in the sheet. It is possible to improve the color purity of transmitted light while preventing the occurrence of the above. Furthermore, if the color purity improving sheet of the present invention is used, for example, the color purity can be improved only by arranging the sheet in a liquid crystal display device, which is excellent in practicality.

  In the present invention, “improvement of color purity” includes, for example, converting yellow light, which is an intermediate color between red and green, into red light, converting light of an intermediate color between green and blue into green light, For example, converting light of any one color of red, green, and blue into light of other colors such as red, green, and blue.

  In the color purity improving sheet of the present invention, the light emitting means preferably contains a fluorescent substance.

  In the color purity improving sheet of the present invention, the light emitting layer is preferably formed of a matrix polymer and a fluorescent material.

  In the color purity improving sheet of the present invention, the specific wavelength band absorbed by the light emitting layer is not particularly limited, but can be, for example, in the range of 560 to 610 nm, and the target wavelength band emitted by the light emitting layer is Although it does not restrict | limit in particular, For example, it can be set as the range of 610-700 nm.

  The present invention will be described in detail below.

  In the present invention, the planar shape of the color purity improving sheet is rectangular and may be a square or a rectangle, but is preferably a rectangle.

  The color purity improving sheet absorbs light in a specific wavelength band (unnecessary color light) other than the target wavelength band, converts the wavelength, and emits light in the target wavelength band (light of the required color) to thereby generate a target wavelength. It has a light emitting layer including light emitting means for improving the purity of the color of the band.

  As described above, the light emitting means preferably includes a fluorescent material. Examples of the fluorescent substance include fluoresceins, rhodamines, coumarins, dansyls (dimethylaminonaphthalene sulfonic acids), 7-nitrobenzo-2-oxa-1,3-diazole (NBD) type dyes, pyrene, and perylene series. And fluorescent substances such as phycobiliprotein, cyanine dye, anthraquinone, thioindigo, and benzopyran. The fluorescent substance may be used alone or in combination of two or more.

  Specific examples of the fluorescent substance include, for example, a trade name “Lumogen F Red 305 (perylene)” manufactured by BASF Corporation, and a trade name “Plast Red 8355 (anthraquinone series) manufactured by Arimoto Chemical Industry Co., Ltd. 8365 (Anthraquinone), Red D-54 (thioindigo), Red DR-426 (benzopyran), Red DR-427 (benzopyran)), manufactured by Hayashibara Biochemical Research Institute Trade name "NK-1533 (carbocyanine dye)" etc. are mentioned. These fluorescent substances absorb yellow (wavelength 560 to 610 nm), which is an intermediate color between red and green, and emit red light (wavelength 610 to 650 nm).

前記式（１）において、４つのＸは、それぞれ、独立して、ハロゲン基またはアルコキシ基である。また、前記式（１）において、２つのＲは、それぞれ、独立して、アリール基またはアルキル基である。前記４つのＸは、それぞれ同一であってもよいし、全て異なっていてもよい。また、前記２つのＲは、同一であってもよいし、異なっていてもよい。 The structural formula of an example of the perylene fluorescent material is shown in the following formula (1).

In the formula (1), the four Xs are each independently a halogen group or an alkoxy group. In the formula (1), two Rs are each independently an aryl group or an alkyl group. The four Xs may be the same or different from each other. Further, the two Rs may be the same or different.

  The graph of FIG. 1 shows the absorption spectrum of the fluorescent material having the structure of the formula (1). As shown, the maximum absorption wavelength of this fluorescent material is around 585 nm.

  As described above, the light emitting layer is preferably formed of a matrix polymer and a fluorescent material. The light emitting layer can be produced, for example, by mixing the fluorescent material with a matrix polymer that can be formed as a film and forming the film as a film. The matrix polymer is preferably highly transparent, for example, polyacrylic resins such as polymethyl methacrylate, polyethyl acrylate, polybutyl acrylate; polyoxycarbonyloxyhexamethylene, polyoxycarbonyloxy-1, Polyvinyl alcohol resins such as polycarbonate resins such as 4-isopropylidene-1,4-phenylene, polynorbornene resins, polyvinyl formal, polyvinyl acetal, polyvinyl butyral; cellulose resins such as methyl cellulose, ethyl cellulose and derivatives thereof Can be mentioned. Among these, polymethyl methacrylate is preferable. The said matrix polymer may be used individually by 1 type, and may mix and use 2 or more types.

  The “polynorbornene-based resin” refers to a (co) polymer obtained by using a norbornene-based monomer having a norbornene ring as part or all of a starting material (monomer). The “(co) polymer” represents a homopolymer or a copolymer (copolymer).

  Next, a method for forming the light emitting layer will be described with an example. However, the method for forming the light emitting layer is not limited to this example.

  First, the matrix polymer is dissolved in a solvent to prepare a polymer solution. As the solvent, for example, toluene, methyl ethyl ketone, cyclohexanone, ethyl acetate, ethanol, tetrahydrofuran, cyclopentanone, water and the like can be used.

  Next, the fluorescent material is dissolved in a solvent to prepare a fluorescent material solution. As the solvent, for example, the same solvent as that used to dissolve the matrix polymer described above can be used.

  Next, the polymer solution and the fluorescent substance solution are mixed, and the mixed solution is applied onto a substrate to form a coating film, followed by heating and drying to form a film. In addition, it is preferable to perform a defoaming process before apply | coating to the said liquid mixture on a base material.

  Next, the said light emitting layer can be obtained by peeling the said film from the said base material.

The concentration of the fluorescent substance in the light emitting layer can be appropriately determined according to the type of the fluorescent substance. For example, for 100 parts by weight of the matrix polymer, for example,
It is the range of 0.01-80 weight part, Preferably, it is the range of 0.1-50 weight part, More preferably, it is the range of 0.1-30 weight part.

  The thickness in particular of the said light emitting layer is not restrict | limited, For example, it is the range of 0.1-1000 micrometers, Preferably, it is the range of 1-200 micrometers, More preferably, it is the range of 2-50 micrometers.

  The color purity improving sheet of the present invention may have any configuration as long as it has the light emitting layer. For example, the sheet | seat which consists only of the said light emitting layer, and the sheet | seat which laminated | stacked another layer on the said light emitting layer are mention | raise | lifted.

  The optical device of the present invention includes a light source device and the color purity improving sheet of the present invention.

  The light source device is not particularly limited, and examples thereof include a cold cathode tube and a light emitting diode (LED).

  The color purity improving sheet of the present invention can be preferably used for various image display devices such as a liquid crystal display device (LCD) and an EL display (ELD), a solar cell, and the like.

  An example of the configuration of the liquid crystal display device of the present invention is shown in the sectional view of FIG. In addition, in the same figure, in order to make it intelligible, the size, ratio, etc. of each structural member differ from actual. As illustrated, the liquid crystal display device includes a liquid crystal panel 11, a color purity improving sheet 10 of the present invention, a light source device 14, and a light guide plate 15 as main components. The liquid crystal panel 11 has a configuration in which a first polarizing plate 131 and a second polarizing plate 132 are disposed on both sides of the liquid crystal cell 12, respectively. In the liquid crystal cell 12, a first alignment film 151 and a second alignment film 152 are disposed on both sides of the liquid crystal layer 140, respectively, and a first transparent electrode 161 and a second transparent film are disposed on the outer sides of the first alignment film 151 and the second alignment film 152, respectively. An electrode 162 is disposed, and a color filter 170 and a black matrix 190 of R (red), G (green), B (blue), etc. in a predetermined arrangement are disposed outside the first transparent electrode 162 and a protective film 180. In addition, the first substrate 101 and the second substrate 102 are respectively disposed outside the second transparent electrode 162, the color filter 170, and the black matrix 190, respectively. In the liquid crystal panel 11, the first polarizing plate 131 side is a display side, and the second polarizing plate 132 side is a back side. The color purity improving sheet 10 of the present invention is disposed on the back side of the liquid crystal panel 11. The light guide plate 15 is arranged in parallel outside the color purity improving sheet 10 of the present invention so as to overlap the liquid crystal panel 11. The light source device 14 is disposed on the opposite side of the light guide plate 12 from the liquid crystal panel 11. In FIG. 2, the color purity improving sheet 10 of the present invention is arranged between the liquid crystal panel 11 and the light guide plate 15, but the color purity improving sheet 10 of the present invention is the light guide plate. 15 and the light source device 14. Further, in the liquid crystal display device of this example, a case where the light source device 14 employs a direct method in which the light source device 14 is disposed directly below the liquid crystal panel 13 via the color purity improving sheet 10 and the light guide plate 15 of the present invention is employed. Although shown, this invention is not limited to this, For example, a sidelight system may be used. Furthermore, the liquid crystal display device of the present invention may have a diffuse reflector. For example, in FIG. 2, the diffuse reflection plate is disposed between the light source device 14 and the light guide plate 15 or on the side opposite to the light guide plate 15 of the light source device 14.

  In the liquid crystal display device of this example, the color purity is improved, for example, as follows. For example, the light source device 14 has a blue light emission peak near 435 nm, green light near 545 nm, and a red light emission peak near 610 nm, and the liquid crystal display device uses only green and red light emission. It is assumed that light emission of yellow (near 585 nm) which is a red intermediate color is unnecessary. In this case, the color purity improving sheet 10 includes, for example, a fluorescent material having a maximum absorption wavelength near 585 nm and emitting light at 610 nm or more. By doing so, the yellow light is absorbed by the fluorescent material, and red light of 610 nm or more is emitted. Thereby, the color purity of the light emitted from the light source device 14 is improved. Further, the color purity improving sheet 10 of the present invention is not provided on a constituent member such as a light guide plate or a reflecting plate as in a conventional optical device, but is a single sheet. In this way, by making the color purity improving sheet 10 of the present invention a single sheet having a fluorescent material, the fluorescent material can be uniformly distributed in the sheet, thereby preventing the occurrence of color unevenness and luminance unevenness. Is done.

  The image display device of the present invention is used for any appropriate application. Applications include, for example, OA equipment such as desktop personal computers, notebook personal computers, and copiers, mobile phones, watches, digital cameras, personal digital assistants (PDAs), portable devices such as portable game machines, video cameras, televisions, microwave ovens, etc. Household electrical equipment, back monitor, car navigation system monitor, car audio and other in-vehicle equipment, display equipment for commercial store information monitors, security equipment such as monitoring monitors, nursing care monitors, medical monitors, etc. Nursing care / medical equipment.

  Next, examples of the present invention will be described together with comparative examples. The present invention is not limited or restricted by the following examples and comparative examples. Moreover, the measurement of the front luminance in Examples and Comparative Examples was performed by the following method. In this example and comparative example, a light source device having a large emission peak of blue near 435 nm, green near 545 nm, and red near 610 nm was used. In this example and comparative example, only blue, green and red light emission was required, and light emission of yellow (near 585 nm), which is an intermediate color between green and red, was unnecessary.

(1) Front luminance By using a spectrophotometer (manufactured by Otsuka Electronics Co., Ltd., trade name “instant multiphotometry system MCPD-3000”), the front luminance of the liquid crystal display device (absolute energy of emission intensity: μW / cm ² / nm) Was measured. At this time, the light receiving part was installed at a position 3 cm above (display side) the liquid crystal display device.

(Example 1)
[Preparation of sheet for improving color purity]
First, a polymethyl methacrylate resin (trade name “Parapet EH-1000P” manufactured by Kuraray Co., Ltd.) was dissolved in toluene to prepare a 30 wt% polymer solution. Next, a phosphor having the structure of the above formula (1) (trade name “Lumogen F Red 305” manufactured by BASF Corporation) was dissolved in toluene to prepare a 19 wt% phosphor solution. After 100 parts by weight of the polymer solution and 19 parts by weight of the fluorescent substance solution were mixed with a hybrid mixer, defoaming treatment was performed. The obtained mixed liquid was cast on a PET base material using an applicator and dried at 90 ° C. for 20 minutes to obtain a film. The film was peeled from the PET substrate to obtain a color purity improving sheet. The thickness of this color purity improving sheet was 30 μm.

[Measurement of front brightness]
The color purity improving sheet was incorporated into a liquid crystal display device having the configuration shown in FIG. 2 and front luminance was measured.

(Comparative Example 1)
Front luminance was measured in the same manner as in Example 1 except that the color purity improving sheet was not incorporated into the liquid crystal display device.

In Example 1, compared with Comparative Example 1 in which the color purity improving sheet was not incorporated, yellow light emission near 585 nm was suppressed, blue light near 435 nm, green light near 545 nm, and red light emission near 610 became stronger. And the color purity was improved. Further, in Example 1, the occurrence of uneven color and brightness was prevented, and the color and brightness of the entire display surface were uniform.

  As described above, the color purity improving sheet of the present invention can improve the color purity of transmitted light while preventing the occurrence of color unevenness and brightness unevenness, and is excellent in practicality. Therefore, the color purity improving sheet of the present invention can be suitably used for, for example, an image display device, a solar cell, etc., but its use is not limited and can be applied to a wide field.

FIG. 1 is a graph showing an absorption spectrum of an example of a fluorescent material used in the present invention. FIG. 2 is a cross-sectional view showing an example of the configuration of the liquid crystal display device of the present invention.

Explanation of symbols

10 color purity improving sheet 11 liquid crystal panel 12 liquid crystal layer 14 light source device 15 light guide plate 101 first substrate 102 second substrate 131 first polarizing plate 132 second polarizing plate 140 liquid crystal layer 151 first alignment film 152 first Two alignment films 161 First transparent electrode 162 Second transparent electrode 170 Color filter 180 Protective film 190 Black matrix

Claims (7)

It has a light emitting layer including a light emitting means for improving the purity of color in a target wavelength band by absorbing light in a specific wavelength band other than the target wavelength band and converting the wavelength to emit light in the target wavelength band. Color purity improving sheet. The color purity improving sheet according to claim 1, wherein the light emitting means contains a fluorescent material. The color purity improving sheet according to claim 1, wherein the light emitting layer is formed of a matrix polymer and a fluorescent material. An optical device including a light source device and a color purity improving sheet, wherein the color purity improving sheet is the color purity improving sheet according to any one of claims 1 to 3. 4. An image display device including a color purity improving sheet, wherein the color purity improving sheet is the color purity improving sheet according to claim 1. 4. A liquid crystal display device including a color purity improving sheet, wherein the color purity improving sheet is the color purity improving sheet according to claim 1. It is a solar cell containing a color purity improvement sheet | seat, Comprising: The said color purity improvement sheet | seat is a solar cell which is a color purity improvement sheet | seat as described in any one of Claim 1 to 3.

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