JP2009229933A - Absorption band control method of optical film, method of manufacturing optical film, optical film, color purity improving sheet, and image display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an absorption band control method of an optical film, which is capable of easily controlling the width of an absorption band of a fluorescent material, to provide a method of manufacturing the optical film, to provide an optical film and a color purity improving sheet which have controlled absorption bands, and to provide an image display apparatus. <P>SOLUTION: In the absorption band control method of the optical film, which controls a half value width of a maximum absorption peak of an absorption spectrum of an optical film obtained by coating a base material with a coating liquid containing a matrix polymer and an ionic colorant to form a coating film and drying the coating film, the half value width is controlled by adjusting the concentration of the matrix polymer in the coating liquid when coating the base material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical film absorption band control method, an optical film manufacturing method, an optical film, a color purity improving sheet, and an image display device.

  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). According to this proposal, it is disclosed that a fluorescent coloring means is configured by selecting a fluorescent material having desired absorption and emission characteristics. In this case, even if a fluorescent substance whose absorption wavelength and emission wavelength are suitable for the purpose can be searched, the fluorescent substance does not necessarily have a desired absorption band width. If the absorption band of the fluorescent material is too wide, the color purity and the overall luminance may be lowered, but it has been difficult to search for a fluorescent material having optimal optical characteristics and to design an optical device.

JP 2005-276586 A

  Therefore, the present invention can easily control the absorption band width of the optical film, the optical film absorption band control method, the optical film manufacturing method, the optical film with the absorption band controlled, and the color purity improvement. An object is to provide a sheet and an image display device.

  In order to achieve the above object, the method for controlling the absorption band of an optical film according to the present invention forms a coating film by applying a coating solution containing a matrix polymer and an ionic dye on a substrate, and dries the coating film. An absorption band control method for an optical film that controls the half-width of the maximum absorption peak of the absorption spectrum of the optical film obtained by adjusting the concentration of the matrix polymer in the coating liquid when applied to the substrate Thus, the half width is controlled. In the present invention, the half-value width of the maximum absorption peak of the optical film is a difference in wavelength between two points that take half the maximum absorbance at the maximum absorption peak of the optical film. The half width can be determined from, for example, the maximum absorption peak of the optical film obtained by measuring the absorption spectrum of the optical film with an ultraviolet-visible spectrophotometer, as described in Examples below.

  The method for producing an optical film of the present invention is a method for producing an optical film in which a coating liquid containing a matrix polymer and an ionic dye is applied to a substrate to form a coating film, and the coating film is dried. A film absorption band control step, wherein the absorption band control step is performed by the optical film absorption band control method of the present invention.

  The optical film of the present invention is manufactured by the method for manufacturing an optical film of the present invention.

  The color purity improving sheet of the present invention is a color purity improving sheet containing an optical film, wherein the optical film is the optical film of the present invention.

  The color purity improving sheet of the present invention contains a matrix polymer and an ionic dye, has a maximum absorption peak wavelength of an absorption spectrum in the range of 560 to 610 nm, a half-value width of the maximum absorption peak is 100 nm or less, and emits maximum light. The peak wavelength is in the range of 600 to 700 nm.

  The image display device of the present invention is an image display device including an optical film or a color purity improving sheet, wherein the optical film is the optical film of the present invention, and the color purity improving sheet is a color of the present invention. It is a purity improving sheet.

  The method for controlling the absorption band of the optical film of the present invention enables the optical absorption characteristics of the resulting optical film to be controlled by a very simple method of adjusting the concentration of the matrix polymer in the coating liquid that is the optical film forming material. Is. Since the half-value width of the absorption spectrum can be easily controlled, the optical film can be easily designed and controlled in accordance with the intended use of the optical film.

  In the method for controlling the absorption band of an optical film of the present invention, the matrix polymer is preferably at least one polymer selected from the group consisting of polyvinyl alcohol, polymethyl methacrylate, and modified polymers thereof.

  In the method for controlling the absorption band of the optical film of the present invention, the matrix polymer is preferably polyvinyl alcohol, and the concentration of polyvinyl alcohol in the coating solution is preferably in the range of 6 to 15% by weight.

  In the method for controlling the absorption band of the optical film of the present invention, the matrix polymer is preferably polymethyl methacrylate, and the concentration of polymethyl methacrylate in the coating solution is preferably in the range of 20 to 35% by weight.

前記一般式（１）において、ｎは１〜４の自然数、Ｒは炭素原子数１〜４の直鎖または分岐アルキル基、Ｘはハロゲン、ＣｌＯ_４またはＰＦ_６、Ｙはヘテロ原子またはイソプロピリデン基である。 In the method for controlling the absorption band of the optical film of the present invention, the ionic dye is preferably a cyanine dye, and more preferably the cyanine dye is represented by the following general formula (1).

In the general formula (1), n is a natural number of 1 to 4, R is a linear or branched alkyl group having 1 to 4 carbon atoms, X is a halogen, ClO ₄ or PF ₆ , and Y is a hetero atom or an isopropylidene group. It is.

Furthermore, it is preferable that the cyanine dye is represented by the following structural formula (2) or (3).

  In the method for controlling an absorption band of an optical film of the present invention, the coating liquid preferably contains a mixed solvent, and the mixed solvent includes a solvent that dissolves the matrix polymer, and a solvent that dissolves the ionic dye. It is more preferable that these are mixed.

  In the present invention, “improvement of color purity” means that light in a specific wavelength band (unnecessary color light) other than the target wavelength band is absorbed and wavelength-converted to obtain light in the target wavelength band (light of the required color). It includes improving the purity of the color in the target wavelength band by emitting light. Specifically, for example, converting yellow light that is an intermediate color between red and green into red light, converting blue-green light that is an intermediate color between green and blue into green light, red, green, Conversion of light of any blue color into light of other colors of red, green, and blue.

  The color purity improving sheet of the present invention includes an optical film produced using the absorption band control method for the optical film.

  In the color purity improving sheet of the present invention, the maximum absorption peak wavelength of the absorption spectrum is in the range of 560 to 610 nm, the half width of the maximum absorption peak is 100 nm or less, and the maximum emission peak wavelength is in the range of 600 to 700 nm. It is preferable. When the half width is in the above range, intermediate color (yellow) light can be selectively removed without absorbing light in the wavelength band (red and green light) necessary for color tone expression.

The color purity improving sheet of the present invention contains a matrix polymer and an ionic dye, has a maximum absorption peak wavelength of an absorption spectrum in the range of 560 to 610 nm, a half-value width of the maximum absorption peak is 100 nm or less, and emits maximum light. The peak wavelength is in the range of 600 to 700 nm. In the color purity improving sheet of the present invention, the ionic dye is preferably a cyanine dye represented by the following structural formula (2). .

  In the color purity improving sheet of the present invention, the matrix polymer is preferably at least one polymer selected from the group consisting of polyvinyl alcohol, polymethyl methacrylate, and modified polymers thereof.

  Next, the present invention will be described in detail. However, the present invention is not limited by the following description.

  In the present invention, the optical film is produced from a coating solution containing a matrix polymer and an ionic dye. The optical film can be produced by applying a coating liquid containing the matrix polymer that can be formed as a film and the ionic dye onto a substrate and drying it to form a film.

  The matrix polymer is not particularly limited, but a matrix polymer having excellent visible light transmittance (preferably light transmittance of 90% or more) and transparency (preferably having a haze value of 1% or less) is preferable. Examples of the matrix polymer include polyacrylic resins such as polymethyl methacrylate, polyethyl acrylate, and polybutyl acrylate; polyoxycarbonyloxyhexamethylene, polyoxycarbonyloxy-1,4-isopropylidene-1,4 -Polyvinyl alcohol resins such as polycarbonate resins such as phenylene, polynorbornene resins, polyvinyl formal, polyvinyl acetal, and polyvinyl butyral; cellulose resins such as methyl cellulose, ethyl cellulose, and derivatives thereof. Among these, polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), and modified polymers thereof are 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).

  The PVA can be obtained, for example, by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester monomer. The degree of saponification of the PVA is preferably in the range of 95 to 99.9 mol%. By using PVA whose saponification degree is in the above range, a color purity improving sheet having more excellent durability can be obtained. The average degree of polymerization of the PVA can be appropriately selected depending on the purpose. The average degree of polymerization is preferably in the range of 1200 to 3600. The average degree of polymerization can be determined according to, for example, JIS K 6726 (1994 edition).

  It is also preferable that the ionic dye contains a fluorescent substance. By including a fluorescent material having light absorption / emission characteristics in a specific wavelength region, an optical film can be used as the color purity improving sheet. Examples of the fluorescent substance include fluoresceins, rhodamines, coumarins, dansyls (dimethylaminonaphthalene sulfonic acids), 7-nitrobenzo-2-oxa-1,3-diazole (NBD) type dyes, pyrenes, and perylenes. 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 type)” 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 Laboratories, Inc. Trade names “NK-1533 (carbocyanine dye)”, “NK-3918 (carbocyanine dye)” and the like can be 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).

The ionic dye is preferably a cyanine dye. Specific examples of the cyanine dye are shown in the following structural formulas (4) to (11).

前記一般式（１）において、ｎは１〜４の自然数、Ｒは炭素原子数１〜４の直鎖または分岐アルキル基、Ｘはハロゲン、ＣｌＯ_４またはＰＦ_６、Ｙはヘテロ原子またはイソプロピリデン基である。 The cyanine dye is particularly preferably the one represented by the following general formula (1).

In the general formula (1), n is a natural number of 1 to 4, R is a linear or branched alkyl group having 1 to 4 carbon atoms, X is a halogen, ClO ₄ or PF ₆ , and Y is a hetero atom or an isopropylidene group. It is.

Of the cyanine dyes represented by the general formula (1), those represented by the following structural formula (2) or (3) are more preferable.

  Next, the method for producing the optical film will be described with examples. However, the method for preparing the coating solution in the production of the optical film is not limited to this example.

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

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

  Next, the matrix polymer solution and the dye solution are mixed, and the coating liquid, which is the mixed liquid, is applied onto the substrate to form a coating film and dried to form the optical film in the present invention. . When the solvent in which the matrix polymer is soluble and the solvent in which the dye is soluble are different, a mixed solvent of these solvents is included. In addition, it is preferable to perform a defoaming process before apply | coating the said coating liquid on a base material.

  The optical film can be used after being peeled from the substrate, or can be used as it is formed on the substrate.

  The method for controlling the absorption band of the optical film of the present invention controls the half width of the maximum absorption peak in the absorption spectrum of the obtained optical film by adjusting the concentration of the matrix polymer in the coating solution. In the coating solution, the half width can be narrowed by increasing the concentration of the matrix polymer. In order to narrow the half width, for example, when the matrix polymer is PVA, the PVA concentration in the coating solution is preferably in the range of 3 to 15% by weight, more preferably 4 to 12% by weight. More preferably, it is the range of 6 to 10 weight%. When the matrix polymer is PMMA, the PMMA concentration in the coating solution is preferably 20 to 35% by weight, more preferably 20 to 30% by weight, and still more preferably 20 to 28. It is in the range of wt%. The upper limit value of the matrix polymer concentration is set within a viscosity range that can be applied to obtain a desired film thickness. The matrix polymer concentration can be adjusted to an appropriate range depending on the viscosity and degree of polymerization of the matrix polymer itself and the composition of the solvent used.

  In the coating solution, the concentration of the ionic dye with respect to the matrix polymer can be appropriately determined according to the type of the ionic dye. The range is 0.001 to 30 parts by weight, preferably 0.002 to 25 parts by weight, and more preferably 0.005 to 20 parts by weight.

  The relationship between the present invention and its effects is inferred as follows, but the present invention is not limited by the inference. That is, it is generally known that an ionic dye such as a cyanine dye forms a dimer or a higher-order aggregate in a solution. Therefore, it is considered that various association states exist in the coated thin film when the solution containing the ionic dye is applied. And, when it does not converge to the most stable state (monomer or aggregate) until drying, the light absorption spectrum of the obtained thin film becomes a set of spectra that reflect all the associated states, It is expected to show a broad and broad shape. Conversely, if it can converge to the most stable structure before drying, it is expected to show a narrow-band spectral shape that reflects only that structure. In the present invention, the state change process of the ionic dye from coating to drying is controlled by the concentration of the matrix polymer to obtain a target half-width spectrum. In particular, a narrow band spectrum can be obtained by increasing the concentration of the matrix polymer.

  The thickness of the optical film obtained by drying the coating solution is not particularly limited, and is, for example, in the range of 0.1 to 1000 μm, preferably in the range of 1 to 200 μm, more preferably 2 to 50 μm. Range.

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

  The optical film and the color purity improving sheet of the present invention can be suitably used for an optical device having a configuration including a light source device. The light source device is not particularly limited, and examples thereof include a cold cathode tube and a light emitting diode (LED).

  The optical film and 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 a liquid crystal display device using the optical film and the color purity improving sheet 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 shown in the figure, this liquid crystal display device includes a liquid crystal panel 11, the optical film or 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 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 optical film or 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 so as to overlap the liquid crystal panel 11 on the outside of the optical film or color purity improving sheet 10 of the present invention. 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. 6, the optical film or color purity improving sheet 10 of the present invention is disposed between the liquid crystal panel 11 and the light guide plate 15, but the optical film or color purity improving sheet of the present invention. 10 may be disposed between the light guide plate 15 and the light source device 14. Further, in the liquid crystal display device of this example, a direct method is adopted in which the light source device 14 is disposed directly below the liquid crystal panel 13 via the optical film or color purity improving sheet 10 of the present invention and the light guide plate 15. However, the present invention is not limited to this. For example, a side light system may be used. Furthermore, the liquid crystal display device may have a diffuse reflector. For example, in FIG. 6, the diffuse reflection plate is disposed between the light source device 14 and the light guide plate 15 or on the opposite side of the light source device 14 from the light guide plate 15.

  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, as the optical film or the color purity improving sheet 10, for example, an optical film having a maximum absorption wavelength in the vicinity of 585 nm is used. By doing so, the yellow light is absorbed by the fluorescent material. At this time, if the half width of the maximum absorption peak in the absorption spectrum is 100 nm or less, there is little influence on the absorption band of light other than yellow (green or red), so that the decrease in luminance of green and red is suppressed, The color purity of the light emitted from the light source device 14 can be improved.

  Moreover, as the optical film or the color purity improving sheet 10, for example, a color purity improving sheet containing an ionic dye having a maximum absorption wavelength near 585 nm and emitting light at 610 nm or more is used. By doing so, the yellow light is absorbed by the ionic dye, and red light of 610 nm or more is emitted. At this time, if the half width of the maximum absorption peak in the absorption spectrum is 100 nm or less, there is little influence on the absorption band of light other than yellow (green or red). Since red light is emitted by the color purity improving sheet, the color purity of the light emitted from the light source device 14 can be further improved.

  According to the method for controlling the absorption band of an optical film of the present invention, the half width of the absorption spectrum of the optical film can be easily controlled. Therefore, since the optical film can be designed to meet the intended use and required performance, it can be applied in the production of optical films for various uses.

  The optical film and color purity improving sheet of the present invention can be suitably used for an image display device. The image display device 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. The present invention is not limited or restricted by the following examples.

(1) Absorption spectrum of optical film, maximum absorption peak wavelength, half-width of maximum absorption peak and absorbance at maximum absorption peak wavelength The absorption spectrum of the optical film is an ultraviolet-visible spectrophotometer (trade name “manufactured by JASCO Corporation” V-560 "). From the measured absorption spectrum, the maximum absorption peak wavelength, the half width of the maximum absorption peak, and the absorbance at the maximum absorption peak wavelength of the optical film were determined.

(2) Thickness of optical film The thickness of the optical film was measured with a micro gauge thickness gauge manufactured by Mitutoyo Corporation. An optical film was formed on a glass substrate (base material), the total thickness was measured, and the thickness of the optical film was calculated by subtracting the thickness of the glass substrate from the total thickness.

(3) Emission spectrum of optical film, maximum emission peak wavelength The emission spectrum of the optical film was measured using a spectrofluorometer (trade name “F-4500” manufactured by Hitachi, Ltd.). The maximum emission peak wavelength of the optical film was determined from the measured emission spectrum.

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

Example 1
[Production of optical film]
First, polyvinyl alcohol resin (PVA) (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “GOHSENOL 1800NH”) was dissolved in water to prepare a 10% by weight matrix polymer solution. Next, 0.103 g of a cyanine dye having a structure of the above formula (2) (trade name “NK-1533” manufactured by Hayashibara Biochemical Laboratories Co., Ltd.) 2 in an ethanol / water mixed solvent (weight ratio 1: 1) 2 Dissolved in 257 g to prepare a dye solution. This was mixed with 13.228 g of the matrix polymer solution to prepare a coating solution A containing PVA and the cyanine dye in a weight ratio of 92: 8. The coating liquid A was further diluted with an ethanol / water mixed solvent (weight ratio 1: 1) to prepare a coating liquid having the composition shown in Table 1 below. The obtained coating solution was spin-coated on a glass substrate under the condition of 1000 rpm × 30 sec and dried to obtain a thin film shown in Table 1 below.

(Example 2)
[Production of optical film]
First, polyvinyl alcohol resin (PVA) (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “GOHSENOL 1800NH”) was dissolved in water to prepare a 10% by weight matrix polymer solution. Next, 0.041 g of a cyanine dye having a structure of the above formula (2) (trade name “NK-1533” manufactured by Hayashibara Biochemical Laboratories Co., Ltd.) is mixed with ethanol / water mixed solvent (weight ratio 1: 1) 1 Dissolved in 0.063 g to prepare a dye solution. This was mixed with 13.104 g of the matrix polymer solution to prepare a coating solution B containing PVA and the cyanine dye in a weight ratio of 97: 3. The coating liquid B was further diluted with an ethanol / water mixed solvent (weight ratio 1: 1) to prepare a coating liquid having the composition shown in Table 1 below. The obtained coating solution was spin-coated on a glass substrate under the condition of 1000 rpm × 30 sec and dried to obtain a thin film shown in Table 1 below.

(Example 3)
[Production of optical film]
First, polymethyl methacrylate resin (PMMA) (trade name “Parapet EH-1000P” manufactured by Kuraray Co., Ltd.) was dissolved in toluene to prepare a 30 wt% matrix polymer solution. Next, 0.103 g of a cyanine dye having the structure of the above formula (2) (trade name “NK-1533” manufactured by Hayashibara Biochemical Laboratories Co., Ltd.) is mixed with an ethanol / toluene mixed solvent (weight ratio 1: 1) 1 And dissolved in 834 g to prepare a dye solution. This was mixed with 15.131 g of the matrix polymer solution to prepare a coating solution C containing PMMA and the cyanine dye at a weight ratio of 98: 2. The coating liquid C was further diluted with an ethanol / toluene mixed solvent (weight ratio 1: 1) to prepare a coating liquid having the composition shown in Table 2 below. The obtained coating solution was spin-coated on a glass substrate under the condition of 1000 rpm × 30 sec and dried to obtain a thin film shown in Table 2 below.

Example 4
[Production of optical film]
First, polymethyl methacrylate resin (PMMA) (trade name “Parapet EH-1000P” manufactured by Kuraray Co., Ltd.) was dissolved in toluene to prepare a 30 wt% matrix polymer solution. Next, 0.094 g of a cyanine dye having a structure of the above formula (3) (trade name “NK-3918” manufactured by Hayashibara Biochemical Laboratories Co., Ltd.) is mixed with ethanol / toluene mixed solvent (weight ratio 1: 1) 1 A dye solution was prepared by dissolving in .983 g. This was mixed with 14.984 g of the matrix polymer solution to prepare a coating solution D containing PMMA and the cyanine dye at a weight ratio of 98: 2. The coating liquid D was further diluted with an ethanol / toluene mixed solvent (weight ratio 1: 1) to prepare a coating liquid having the composition shown in Table 3 below. The obtained coating solution was spin-coated on a glass substrate under the condition of 1000 rpm × 30 sec and dried to obtain a thin film shown in Table 3 below.

  In FIGS. 1-4, the absorption spectrum of the optical film obtained above is shown. Each absorption spectrum shows the absorbance at the maximum absorption peak wavelength normalized to 1. In each Example, the half value width of the absorption spectrum changed as shown in FIGS. 1 to 4 by changing the concentration of the matrix polymer. In each example, the half width was narrowed as the concentration of the matrix polymer was increased. In particular, the optical films of A, B, B-1 and C have a maximum absorption peak wavelength of the absorption spectrum in the range of 560 to 610 nm, and the half width of the absorption spectrum is 100 nm or less by adjusting the concentration of the matrix polymer. Controlled. Furthermore, since the optical film of A, B, B-1 and C has the maximum light emission peak wavelength in the range of 600 to 700 nm, it can be favorably used as a color purity improving sheet. As an example, FIG. 5 shows an emission spectrum of the optical film of C when the wavelength of the excitation light is 590 nm.

[Measurement of front brightness]
When the optical purity of the A, B, B-1 and C is placed on the light source device as a color purity improving sheet and the front luminance is measured, it is used as a base material when the color purity improving sheet is placed. Compared with the case where only the glass plate was placed and measured, yellow light emission near 585 nm was suppressed, red light emission near 610 was strengthened, and color purity was improved.

  As described above, when the method for controlling the absorption band of the optical film of the present invention is used, the half width of the absorption spectrum of the optical film can be easily controlled. Therefore, an optical film having desired optical properties can be easily obtained. For image display devices, it is possible to easily design a color purity improving sheet that matches the emission wavelength of the light source. The optical film and the color purity improving sheet obtained by the method for controlling the absorption band of the optical film of the present invention can be suitably used for, for example, an image display device, a solar cell, etc. Is possible.

1 is a graph showing the absorption spectrum of the optical film obtained in Example 1. FIG. FIG. 2 is a graph showing the absorption spectrum of the optical film obtained in Example 2. FIG. 3 is a graph showing the absorption spectrum of the optical film obtained in Example 3. FIG. 4 is a graph showing the absorption spectrum of the optical film obtained in Example 4. FIG. 5 is a graph showing an emission spectrum of the optical film obtained in Example 3. FIG. 6 is a cross-sectional view showing an example of the configuration of a liquid crystal display device using the optical film or color purity improving sheet of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical film or color purity improvement sheet | seat 11 Liquid crystal panel 12 Liquid crystal layer 14 Light source device 15 Light guide plate 101 1st board | substrate 102 2nd board | substrate 131 1st polarizing plate 132 2nd polarizing plate 140 Liquid crystal layer 151 1st orientation Film 152 Second alignment film 161 First transparent electrode 162 Second transparent electrode 170 Color filter 180 Protective film 190 Black matrix

Claims (17)

An optical system that controls the half-value width of the maximum absorption peak of the absorption spectrum of an optical film obtained by applying a coating solution containing a matrix polymer and an ionic dye to a substrate to form a coating film and drying the coating film. An absorption band control method for an optical film, comprising: controlling the half width by adjusting a concentration of a matrix polymer in the coating solution when applied to the substrate. Method. The method for controlling an absorption band of an optical film according to claim 1, wherein the matrix polymer is at least one polymer selected from the group consisting of polyvinyl alcohol, polymethyl methacrylate, and modified polymers thereof. The method for controlling the absorption band of an optical film according to claim 1 or 2, wherein the matrix polymer is polyvinyl alcohol, and the concentration of polyvinyl alcohol in the coating solution is in the range of 6 to 15% by weight. The method for controlling an absorption band of an optical film according to claim 1 or 2, wherein the matrix polymer is polymethyl methacrylate, and the concentration of polymethyl methacrylate in the coating solution is in the range of 20 to 35% by weight. The method for controlling an absorption band of an optical film according to any one of claims 1 to 4, wherein the ionic dye is a cyanine dye. The method for controlling an absorption band of an optical film according to claim 5, wherein the cyanine dye is represented by the following general formula (1).

In the general formula (1), n is a natural number of 1 to 4, R is a linear or branched alkyl group having 1 to 4 carbon atoms, X is a halogen, ClO ₄ or PF ₆ , and Y is a hetero atom or an isopropylidene group. It is. The method for controlling an absorption band of an optical film according to claim 6, wherein the cyanine dye is represented by the following structural formula (2) or (3).

The method for controlling an absorption band of an optical film according to any one of claims 1 to 7, wherein the coating liquid contains a mixed solvent. The method for controlling an absorption band of an optical film according to claim 8, wherein the mixed solvent is a mixture of a solvent that dissolves the matrix polymer and a solvent that dissolves the ionic dye. A method for producing an optical film comprising applying a coating liquid containing a matrix polymer and an ionic dye to a substrate to form a coating film, and drying the coating film, comprising an optical film absorption band control step, The said absorption zone control process is implemented by the absorption zone control method of the optical film as described in any one of Claim 1 to 9. The manufacturing method of the optical film characterized by the above-mentioned. It is an optical film, Comprising: The optical film manufactured by the manufacturing method of the optical film of Claim 10. A color purity improving sheet comprising an optical film, wherein the optical film is the optical film according to claim 11. The color purity improvement according to claim 12, wherein the maximum absorption peak wavelength of the absorption spectrum is in the range of 560 to 610 nm, the half width of the maximum absorption peak is 100 nm or less, and the maximum emission peak wavelength is in the range of 600 to 700 nm. Sheet. Including a matrix polymer and an ionic dye, the maximum absorption peak wavelength of the absorption spectrum is in the range of 560 to 610 nm, the half width of the maximum absorption peak is 100 nm or less, and the maximum emission peak wavelength is in the range of 600 to 700 nm. A color purity improving sheet characterized by being. The color purity improving sheet according to claim 14, wherein the ionic dye is a cyanine dye represented by the following structural formula (2).

The color purity improving sheet according to claim 14 or 15, wherein the matrix polymer is at least one polymer selected from the group consisting of polyvinyl alcohol, polymethyl methacrylate, and modified polymers thereof. It is an image display apparatus containing an optical film or a color purity improvement sheet | seat, Comprising: The said optical film is an optical film of Claim 11, The said color purity improvement sheet | seat is any one of Claims 12-16. Display device which is a color purity improving sheet.

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