JP5182851B2 - Method for producing vanadium oxide phosphor thin film - Google Patents

Description

  The present invention relates to a method for producing a vanadium oxide phosphor thin film that emits white light by using light in an ultraviolet / near ultraviolet region suitable for a light emitting material such as a white LED as excitation light.

  In recent years, white LEDs are used in mobile phones and various display devices, and at the same time, are attracting attention as indoor lighting devices instead of fluorescent lamps from the viewpoint of energy saving. White LEDs use near-ultraviolet or blue LEDs as excitation light sources, and produce white light by combining phosphors having emission intensities at various wavelengths. Specifically, a blue LED emits yellow, green, and red phosphors as excitation light to obtain white light. (Patent Document 1)

However, the white LED white light obtained by combining a plurality of phosphors has problems such as color loss and strong light emission only at a specific wavelength, and efforts to improve color rendering properties when used as indoor lighting. Is required. For this reason, it is most desirable that the phosphor used in the white LED for illumination has a wide emission wavelength, does not have a sharp emission peak at a specific wavelength, and further exhibits white fluorescence with as few phosphor combinations as possible. In recent years, phosphors having a relatively wide emission wavelength such as α-sialon phosphors excited by blue LEDs (Patent Document 2) have been developed. However, since the emission spectrum range is not sufficiently wide, In addition, it was necessary to improve the color rendering properties in combination with some phosphors.
Thus, it was difficult to show white fluorescence with a color rendering property as good as possible with a single substance.
In order to solve such problems, the present inventors have intensively studied. As a result, vanadium oxide (AVO ₃ ; A is one or more selected from the group consisting of K, Rb, and Cs, and Li , Na and NH ₄ may be included, but it shows a broad emission spectrum of a single substance, and a fluorescence spectrum of 490 to 495 nm by excitation with ultraviolet / near ultraviolet light at 250 to 390 nm. It has been found that the phosphor has a maximum in the vicinity and emits white fluorescence that broadens in the range of 390 to 680 nm, and a patent application has been filed earlier (Patent Document 3).

  The fluorescence spectrum emitted from the phosphor of the present invention is an emission spectrum close to the spectrum of lighting fixtures currently used in consumer products and ordinary fluorescent lamps, so that it can be used as it is as a phosphor for white LEDs. it can. Moreover, although the emission spectrum has a peak in the range of 490 to 495 nm, the color temperature is high, but it can be combined with a phosphor having strong emission on the long wavelength side, and a warmer white color can be obtained. Since it does not contain mercury or lead, it has many advantages such as less adverse effects on the environment and human body.

However, in the method for producing a vanadium oxide phosphor disclosed herein, vanadium oxide V ₂ O ₅ powder and carbonate A ₂ CO ₃ powder containing A ions are pulverized and mixed, and the mixture is 300 at atmospheric pressure. Temporarily calcining at around ℃, and then firing at around 450 ℃, mainly to obtain powder and bulk vanadium oxides. Is not taught at all.

By the way, generally, in the application of inorganic solids, when applied to a small device or a member having a planar shape, it is desired to make the film thinner than a powder body or a bulk body. Also, in relation to the substrate, it is considered preferable to lower the film forming temperature as much as possible, and in recent years, the demand for it has been increasing abundantly. There is a strong demand for methods.
For example, even when forming a film on a glass substrate, it is necessary to carry out at a low temperature of 600 ° C. or lower, and it is necessary to reduce the film forming process temperature. Here, the reduction of the film formation temperature increases the choices of the substrate, so that the application range is expected to be expanded. For example, if it becomes possible to lower the film forming temperature to about 200 ° C. or less, it becomes possible to form a film on an organic substrate such as plastic, and development of a flexible light-emitting material can also be expected.

In addition, as a film formation method for AVO ₃ -based compounds, a method of depositing by an immersion method using an aqueous solution has been developed so far (Patent Document 4), but PH must be adjusted to 3 or less with hydrochloric acid, sulfuric acid, nitric acid or the like. In addition, the crystallinity was inferior.

When a certain kind of metal oxide film is produced, a metal organic acid salt or an organic metal compound M _m R _n (where M = typical elements such as Si and Ge, transition metal elements such as Ti and Mn, K, Sr, etc.) Alkali metal, alkaline earth metal elements such as: R = CH ₃ , C ₂ H ₅ , alkyl groups such as C ₃ H ₇ , C ₄ H ₉ , or CH ₃ COO ⁻ , C ₂ H ₅ COO ⁻ , C ₃ A carboxyl group such as H ₇ COO ⁻ or C ₄ H ₉ COO ^— or a carbonyl group of CO (m and n are integers) is dissolved in a soluble solvent, or the liquid is dispersed and coated on the substrate as it is. A method of manufacturing a metal oxide thin film by irradiating an excimer laser in an oxygen atmosphere is also known (Patent Documents 5 to 6). However, a vanadium oxide thin film is formed by a more relaxed process. Nothing is taught about the law.

JP-A-11-31845 JP 2006-257326 A Japanese Patent Application No. 2007-224846 JP 59-121121 A JP 2001-31417 A JP 2000-256862 A

  INDUSTRIAL APPLICABILITY In the present invention, a thin film of vanadium oxide phosphor having excellent crystallinity can be formed at a low temperature of room temperature to 400 ° C., and can be directly formed on an organic substrate which has been difficult in the past without using a binder. It aims to provide a method.

According to this application, the following invention is provided.
<1> A thin film formed on a substrate and containing A (A is one or more atoms selected from K, Rb and Cs) and V in an atomic ratio of substantially 1: 1. A method for producing a vanadium oxide phosphor thin film represented by a composition formula AVO ₃ characterized by irradiating an ultraviolet laser having a wavelength of 400 nm or less after being maintained at a temperature of 25 ° C. to 450 ° C. to crystallize vanadium oxide. .
<2> The method for producing a vanadium oxide phosphor thin film according to <1>, wherein the ultraviolet laser is irradiated in a range of 10 to ²⁰ mJ / cm ² .
<3> A thin film formed on a substrate and containing A (A is one or more atoms selected from K, Rb and Cs) and V in an atomic ratio of substantially 1: 1. after holding at a temperature of 25 ° C. to 450 ° C., and irradiated with UV light below the lamp wavelength 400 nm, a method of manufacturing vanadium oxide phosphor thin film represented by the composition formula AVO _3, characterized in that crystallizing the vanadium oxide .
<4> The method for producing a vanadium oxide phosphor thin film according to <3>, wherein the ultraviolet lamp is irradiated in a range of 15 to 50 mW / cm ² .
<5> The method for producing a vanadium oxide phosphor thin film according to any one of <1> to <4 >, wherein the thin film is irradiated with an ultraviolet lamp and then irradiated with an ultraviolet laser to be crystallized.

According to the method of the present invention, a target AVO ₃ phosphor crystallized thin film can be produced even when the substrate temperature is room temperature. In addition, since film formation by light irradiation can be performed at a low temperature of 200 ° C. or lower, it can be directly formed not only on an inorganic solid substrate such as a glass substrate but also on an organic substrate such as plastic. Therefore, not only can the material cost be reduced, but it can also be applied to flexible light-emitting materials such as displays and lighting fixtures that can be bent freely.
Further, the vanadium oxide phosphor thin film represented by the composition formula AVO ₃ obtained in the present invention has an excitation spectrum in a range of 250 to 390 nm that can be excited by an ultraviolet / near ultraviolet LED that is an excitation light source of a white LED. The fluorescence spectrum emitted by this excitation light spreads from 390 to 680 nm and emits white light. Therefore, it is suitable as a phosphor for white LED. Since the peak of the emission spectrum is in the range of 490 to 502 nm, the color temperature is relatively high, but a warm white color can be obtained by combining with a phosphor having strong emission on the long wavelength side. In addition, since it does not contain mercury or lead, there are few negative effects on the environment and human body.

In the method for producing a vanadium oxide phosphor thin film represented by the composition formula AVO ₃ of the present invention, A formed on a substrate (A is one or more atoms selected from K, Rb and Cs). And a thin film containing V (vanadium) in a substantially 1: 1 atomic ratio is maintained at a temperature of 25 ° C. to 450 ° C., and then irradiated with an ultraviolet laser or an ultraviolet lamp having a wavelength of 400 nm or less to crystallize vanadium oxide. It is characterized by making it.

A formed on a substrate (A is one or more atoms selected from K, Rb and Cs) and a thin film containing V are a compound containing A (ion) and a compound containing V Is a thin film obtained by depositing the above mixture on a substrate by various methods.
Examples of the compound containing A (ion) include inorganic compounds or organic compounds containing one or more atoms selected from K, Rb, and Cs.
Examples of inorganic compounds include precursors such as amorphous KVO ₃ , RbVO ₃ , and CsVO ₃ that have not been crystallized.
Examples of organic compounds generally include β-diketonates, long-chain alkoxides having 6 or more carbon atoms, and organic acid salts that may contain halogen.
Specific examples include naphthenate, 2-ethylhexanoate, and acetylacetonate.
In addition, the compound containing A (ion) may contain one or more selected from Li, Na, and NH ₄ .

As a compound containing V, the inorganic compound or organic compound containing this is mentioned.
Examples of inorganic compounds include precursors such as amorphous KVO ₃ , RbVO ₃ , and CsVO ₃ that have not been crystallized.
Examples of organic compounds generally include vanadium-containing β-diketonates, long-chain alkoxides having 6 or more carbon atoms, and organic acid salts that may contain halogen.
Specific examples include naphthenate, 2-ethylhexanoate, and acetylacetonate.

The compound containing A and V is mixed so that the atoms of A and V are substantially 1: 1 to obtain a solution for forming a thin film. In this case, a solvent such as toluene / xylene may be used if necessary.
Subsequently, this solution is formed into an organic metal thin film on a substrate by an appropriate method. In this case, in order to produce a high-quality film that easily reacts with an oxide, it is desirable to form a film immediately after the preparation of the solution (after mixing the organometallic solution containing A and V).
The film forming method is not limited, and sputtering, MBE, vacuum deposition, CVD, chemical solution method (coating pyrolysis method, spray method) and the like are appropriately used.

Next, after the formed thin film is kept at a temperature of 25 ° C. to 450 ° C., it is irradiated with an ultraviolet laser or an ultraviolet lamp having a wavelength of 400 nm or less.
In the case of an ultraviolet laser, specifically, after film formation, for example, drying is performed at 100 ° C., and then the substrate temperature is set to room temperature, and ultraviolet laser irradiation is performed with low energy. In this case, it is desirable to perform laser irradiation in a range of 10 to ²⁰ mJ / cm ² in order to suppress a decrease in film thickness due to ablation and promote crystallization of vanadium oxide.
In the case of an ultraviolet lamp, after film formation, the substrate temperature is set to room temperature, and ultraviolet lamp irradiation is performed with low energy. In this case, in order to promote crystallization of vanadium oxide, it is desirable to irradiate with an ultraviolet lamp under a condition of 15 to 50 mW / cm ² .
In the present invention, when aiming at shortening the film formation time, it is preferable to crystallize the thin film by irradiating it with an ultraviolet lamp for a short time and then irradiating it with an ultraviolet laser.

When light irradiation by such an ultraviolet laser or ultraviolet lamp having a wavelength of 400 nm or less is used, it is crystallized and emits fluorescence even when the substrate temperature is room temperature.
As the substrate, either an inorganic substrate or an organic substrate can be used. However, in the case of an inorganic solid, it can be formed on any substrate as long as it does not melt at room temperature or melt due to humidity in the air. Is possible. In addition, although the organic substrate is crystallized by light irradiation, in actuality, when light irradiation is performed, the substrate temperature is heated to about 60 to 70 ° C. for an irradiation time of about 10 minutes. Therefore, it is desirable to use a material that does not melt near this temperature. In addition, since many organic substrates such as plastic emit blue light, it is desirable to select a material such as polycarbonate that emits blue light from the substrate or to increase the film thickness of the phosphor in order to exhibit white light.

The vanadium oxide phosphor thin film represented by the composition formula AVO ₃ obtained in the present invention has an excitation spectrum in a range of 250 to 390 nm that can be excited by an ultraviolet / near ultraviolet LED that is an excitation light source of a white LED. The fluorescence spectrum emitted by this excitation light spreads from 390 to 680 nm and emits white light. Therefore, it is suitable as a phosphor for white LED. Since the peak of the emission spectrum is in the range of 490 to 502 nm, the color temperature is relatively high, but a warm white color can be obtained by combining with a phosphor having strong emission on the long wavelength side. In addition, since it does not contain mercury or lead, there are few negative effects on the environment and human body.
Therefore, the vanadium oxide phosphor thin film is extremely useful as a white LED, and can be used, for example, as a lighting device such as a daily light that requires white light or a display device such as a backlight used in various display devices. Can do.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
A solution (C1 solution; Rb: V = 1: 1 (atomic ratio)) in which the vanadium 2-ethylhexanoate solution was mixed with the rubidium 2-ethylhexanoate solution at a constant ratio was prepared. The C1 solution was spin-coated on a glass substrate at 4000 rpm for 10 seconds and dried at 100 ° C. for 10 minutes. Thereafter, a pulse laser of 308 nm was irradiated at a fluence of 20 mJ / cm ² , 10 Hz, and 10 minutes in the atmosphere at room temperature. The RbVO ₃ film thus produced showed white fluorescence due to ultraviolet excitation.

Example 2
In Example 1, when irradiated with a laser fluence of 30 mJ / cm ² , the laser irradiation part showed white fluorescence by ultraviolet excitation.

Example 3
The C1 solution was spin-coated on an organic substrate (PET film) at 4000 rpm for 10 seconds and dried at 100 ° C. for 10 minutes. Thereafter, an ultraviolet lamp of 172 nm was irradiated at an irradiation energy of 38 mW / cm ² for 10 minutes in the atmosphere at room temperature. The RbVO ₃ film produced in this way had good crystallinity only in the light irradiation part, and showed white fluorescence by ultraviolet excitation.

Example 4
In Example 3, when the ultraviolet lamp was irradiated without performing the drying step, only the light irradiation part had good crystallinity and showed white fluorescence by ultraviolet excitation.

Example 5
In Example 4, when the wavelength of the ultraviolet lamp was set to 222 nm and irradiated with light at an energy density of 15 mW / cm ² , only the irradiated portion had good crystallinity and exhibited white fluorescence by ultraviolet excitation.

Example 6
The C1 solution was spin-coated on a glass substrate at 4000 rpm for 10 seconds and dried at 100 ° C. for 10 minutes. Thereafter, an ultraviolet lamp of 172 nm was irradiated at an irradiation energy of 38 mW / cm ² for 10 minutes in the atmosphere at room temperature. The RbVO ₃ film produced in this way had good crystallinity only in the light irradiation part, and showed white fluorescence by ultraviolet excitation.

Example 7
In Example 6, when the ultraviolet lamp was irradiated without performing the drying process, only the light irradiation part had good crystallinity and showed white fluorescence by ultraviolet excitation.

Example 8
In Example 7, when the wavelength of the ultraviolet lamp was set to 222 nm and irradiated with light at an energy density of 15 mW / cm ² , only the irradiated portion had good crystallinity and exhibited white fluorescence by ultraviolet excitation.

According to the method of the present invention, a target AVO ₃ phosphor crystallized thin film can be produced even when the substrate temperature is room temperature. In addition, since film formation by light irradiation can be performed at a low temperature of 200 ° C. or lower, it can be directly formed not only on an inorganic solid substrate such as a glass substrate but also on an organic substrate such as plastic. Therefore, not only can the material cost be reduced, but it can also be applied to flexible light-emitting materials such as displays and lighting fixtures that can be bent freely.
Further, the vanadium oxide phosphor thin film represented by the composition formula AVO ₃ obtained in the present invention has an excitation spectrum in a range of 250 to 390 nm that can be excited by an ultraviolet / near ultraviolet LED that is an excitation light source of a white LED. The fluorescence spectrum emitted by this excitation light spreads from 390 to 680 nm and emits white light. Therefore, it is suitable as a phosphor for white LED. Since the peak of the emission spectrum is in the range of 490 to 502 nm, the color temperature is relatively high, but a warm white color can be obtained by combining with a phosphor having strong emission on the long wavelength side. In addition, since it does not contain mercury or lead, there are few negative effects on the environment and human body.

PL spectrum of RbVO ₃ thin film obtained in Example 1 PL spectrum of RbVO ₃ thin film obtained in Example 3

Claims (5)

A thin film formed on a substrate and containing A (A is one or more atoms selected from K, Rb, and Cs) and V at a substantially 1: 1 atomic ratio, A method for producing a vanadium oxide phosphor thin film represented by the composition formula AVO ₃ , wherein the vanadium oxide is crystallized by being irradiated with an ultraviolet laser having a wavelength of 400 nm or less after being held at a temperature of 450 ° C. 2. The method for producing a vanadium oxide phosphor thin film according to claim 1, wherein an ultraviolet laser is irradiated in a range of 10 to ²⁰ mJ / cm < ² >. A thin film formed on a substrate and containing A (A is one or more atoms selected from K, Rb, and Cs) and V at a substantially 1: 1 atomic ratio, A method for producing a vanadium oxide phosphor thin film represented by the composition formula AVO ₃ , wherein the vanadium oxide is crystallized by irradiating an ultraviolet lamp having a wavelength of 400 nm or less after being held at a temperature of 450 ° C. 4. The method for producing a vanadium oxide phosphor thin film according to claim 3, wherein the ultraviolet lamp is irradiated in a range of 15 to 50 mW / cm < ² >.   The method for producing a vanadium oxide phosphor thin film according to any one of claims 1 to 4, wherein the thin film is irradiated with an ultraviolet lamp and then irradiated with an ultraviolet laser to cause crystallization.

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