WO2009118806A1

WO2009118806A1 - Phosphor mixture and plasma display panel using the phosphor mixture

Info

Publication number: WO2009118806A1
Application number: PCT/JP2008/055446
Authority: WO
Inventors: 福田　晋也; 別井　圭一; 小坂　忠義; 長谷川　実; 井上　一; 瀬尾　欣穂; 智也三澤
Original assignee: 株式会社日立製作所
Priority date: 2008-03-24
Filing date: 2008-03-24
Publication date: 2009-10-01

Abstract

A phosphor mixture composed of phosphor particles, which emit light upon excitation with excitation light, and inorganic pigment particles mixed in the phosphor particles, is used in the formation of a phosphor part in a display device such as PDP. The inorganic pigment particle comprises a crystal matrix having a band gap (W1) larger than the energy of excitation light and an impurity level formed within the band gap (W1). The energy width (W3) from the HOMO level in the impurity level to the conduction band (CB) of the crystal matrix is rendered different from the energy of the excitation light. According to the above constitution, external light can be absorbed while preventing a lowering in luminescence brightness caused by the absorption of the excitation light, and, thus, the roomlight contrast of the display device can be improved.

Description

Phosphor mixture and plasma display panel using the same

The present invention relates to a phosphor technology, and more particularly, to a technology effective when applied to a phosphor used in a display device that displays an image by exciting the phosphor with light, such as a plasma display panel.

There is a plasma display panel (PDP) as a display device using light emission of a phosphor.

The PDP has a front substrate and a rear substrate, and a discharge space in which a discharge gas is sealed is formed between the front substrate and the rear substrate. A desired image is displayed by generating a discharge in the discharge space and exciting the phosphor with vacuum ultraviolet rays generated at this time.

The PDP has phosphors that emit red (R), green (G), and blue (B) colors, and these phosphors are generally white. For this reason, when the PDP is observed in a bright environment, there is a problem that external light incident on the PDP is reflected with a high reflectance, and the contrast (bright room contrast) is lowered.

In order to suppress this reflection of external light, a technique of mixing a white phosphor with an inorganic pigment has been proposed.

For example, Japanese Patent Application Laid-Open No. 10-152680 (Patent Document 1) and Japanese Patent Application Laid-Open No. 11-1331059 (Patent Document 2) disclose a technique of mixing a pigment in a predetermined weight ratio with a phosphor.

Further, for example, in Japanese Patent Application Laid-Open No. 9-40945 (Patent Document 3), Japanese Patent Application Laid-Open No. 10-269952 (Patent Document 4), and Japanese Patent Application Laid-Open No. 11-43670 (Patent Document 5), A technique for coating a pigment with a pigment is disclosed.

Further, for example, Japanese Patent Application Laid-Open No. 2007-80556 (Patent Document 6) discloses a technique of dividing a region where a phosphor layer portion is formed and containing a pigment at a different content in each of the divided regions. ing.
Japanese Patent Laid-Open No. 10-152680 Japanese Patent Laid-Open No. 11-131059 Japanese Patent Laid-Open No. 9-40945 Japanese Patent Laid-Open No. 10-269952 JP 11-43670 A JP 2007-80556 A

However, when an inorganic pigment is mixed with the phosphor, there is a problem that the display brightness of the PDP is lowered. This is because, firstly, the vacuum ultraviolet rays generated by the discharge are absorbed by the inorganic pigment and attenuated, and the light emission luminance is lowered. The second reason is that visible light excited by vacuum ultraviolet rays and emitted from the phosphor is absorbed by the inorganic pigment and attenuated.

For example, in Patent Document 2, when 5 wt% of the pigment is added, the display brightness of the PDP is reduced by about 50% compared to the case where the pigment is not mixed with the phosphor.

Thus, when the inorganic pigment is mixed with the phosphor, the problem that the display brightness of the PDP is lowered has not been solved, and the bright room contrast of the PDP has not been improved stably. For this reason, although the structure which mixes an inorganic pigment with fluorescent substance is variously examined, it has not yet reached practical use.

The present invention has been made in view of the above problems, and a purpose thereof is a technique capable of reducing the reflectance of external light while suppressing a decrease in display luminance of a display device using a phosphor such as PDP. Is to provide.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.

That is, a phosphor mixture used for forming a phosphor part included in a display device such as a PDP in an embodiment of the present invention is a mixture of phosphor particles that emit light when excited by excitation light, and the phosphor particles. The inorganic pigment particles have a crystal matrix having a band gap larger than the energy of the excitation light and an impurity level formed in the band gap, and the impurities The energy width from the HOMO level of the level to the conduction band of the crystal matrix is different from the energy of the excitation light.

Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

That is, it is possible to reduce the reflectance of external light while suppressing a decrease in display brightness of the display device.

It is a principal part expansion assembly perspective view which expands and shows the principal part of PDP which is one embodiment of this invention. It is explanatory drawing which shows the relationship between the external light which injects into PDP, and the display light from a display apparatus. It is explanatory drawing shown as a model simplified in order to demonstrate the effect of a reflectance reduction about the structure of the back substrate structure which PDP shown in FIG. 1 has. It is a principal part expanded sectional view which shows the detailed structure of the fluorescent substance part shown in FIG. It is a band figure which shows the energy band of the inorganic pigment which comprises the fluorescent substance part shown in FIG. It is explanatory drawing which shows the manufacture flow of the fluorescent substance part 23 which PDP which is one embodiment of this invention has.

In the drawings for explaining the present embodiment, parts having the same function are given the same reference numerals, and repeated explanation thereof is omitted in principle. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In this embodiment, a PDP will be described as an example of a display device using a phosphor.

<Basic structure of PDP>
First, an example of the structure of the PDP according to the present embodiment will be described with reference to FIG. 1 using an AC surface discharge type PDP as an example. FIG. 1 is an enlarged perspective view of an essential part of the PDP according to the present embodiment.

In FIG. 1, the PDP 1 has a front substrate structure (first substrate structure) 11 and a back substrate structure (second substrate structure) 12. The front substrate structure 11 and the back substrate structure 12 are overlapped with each other so as to face each other, and have a discharge space 24 therebetween. That is, the front substrate structure 11 and the back substrate structure 12 are disposed to face each other with the discharge space 24 interposed therebetween.

The front substrate structure 11 has a display surface of the PDP 1 and has a front substrate 13 mainly made of glass. A plurality of X electrodes (sustain electrodes, sustain electrodes) 14 and Y electrodes (scan electrodes, scan electrodes) 15 which are display electrodes of the PDP 1 are formed on the inner surface side of the front substrate 13.

The X electrode 14 and the Y electrode 15 constitute a pair of display electrodes for performing a sustain discharge (display discharge, sustain discharge), and are alternately arranged so as to extend in a strip shape along the row direction DX, for example. ing. The pair of X electrode 14 and Y electrode 15 form a display line in the row direction DX in the PDP 1. In FIG. 1, two pairs of the X electrode 14 and the Y electrode 15 are shown in an enlarged manner. However, the PDP 1 has a plurality of X electrodes 14 and Y electrodes 15 according to the number of display lines. Yes.

The X electrode 14 and the Y electrode 15 are generally composed of, for example, an X transparent electrode 14a and a Y transparent electrode 15a made of a transparent electrode material such as ITO (Indium Tin Oxide) or SnO _2, and, for example, Ag (silver), Au X bus electrode (metal electrode part) 14b made of (gold), Al (aluminum), Cu (copper), Cr (chromium), or a laminate thereof (for example, a laminate of Cr / Cu / Cr), Y bus It is comprised with the electrode (metal electrode part) 15b.

FIG. 1 shows the X transparent electrode 14a and the Y transparent electrode 15a extending in a strip shape, but the electrode structure of the X transparent electrode 14a and the Y transparent electrode 15a is not limited to this. For example, in order to stabilize sustain discharge and improve discharge efficiency, the position where the shortest distance between the pair of electrodes (referred to as a discharge gap) overlaps with the X bus electrode 14b and the Y bus electrode 15b so as to approach the cell. It is good also as a structure which forms a protrusion part in the direction which respectively opposes. The electrode structure may be a so-called ALIS (AlternateternLighting of Surface Method).

These electrodes (X electrodes 14, Y electrodes 15) is mainly covered by the configured dielectric layers 17 of a glass material such as SiO _2. The dielectric layer 17 is formed on the second surface 13b side of the front substrate 13, and a third surface 17a facing the second surface 13a and a fourth surface positioned on the opposite side of the third surface 17a. And a surface 17b.

A protective film 18 made of a metal oxide such as MgO is formed on the surface of the dielectric layer 17. The protective film 18 is formed so as to cover one surface of the dielectric layer 17.

On the other hand, the back substrate structure 12 has a back substrate (substrate) 19 mainly made of glass. A plurality of address electrodes (second electrodes) 20 are formed on the surface (inner surface) of the rear substrate 19 facing the front substrate structure 11. Each address electrode 20 is formed so as to extend along a column direction DY intersecting (substantially orthogonal to) the direction in which the X electrode 14 and the Y electrode 15 extend. The address electrodes 20 are arranged with a predetermined arrangement interval so as to be substantially parallel to each other.

Similarly to the X bus electrode 14b and the Y bus electrode 15b, the address electrode 20 is made of, for example, Ag, Au, Al, Cu, Cr, or a laminate thereof (for example, a laminate of Cr / Cu / Cr). Can do.

The address electrode 20 and the Y electrode 15 formed on the front substrate structure 11 constitute an electrode pair for performing address discharge, which is discharge for selecting lighting / non-lighting of the cell 25. That is, the Y electrode 15 has both a function as a sustain discharge electrode and a function as an address discharge electrode (scanning electrode).

Each cell 25 is configured to correspond to the intersection of the address electrode 20 and the pair of X electrode 14 and Y electrode 15. That is, the cell 25 is formed at each intersection of the display electrode pair (a pair of the X electrode 14 and the Y electrode 15) and the address electrode 20. Each cell 25 emits red (R), green (G), and blue (B) visible light by sustain discharge, and a pixel (pixel) is configured by the set of each R, G, and B cell 25. The

The address electrode 20 is covered with a dielectric layer 21. A plurality of partition walls 22 extending in the thickness direction of the back substrate structure 12 are formed on the dielectric layer 21. The barrier ribs 22 are formed to extend in a line along the column direction DY in which the address electrodes 20 extend. The front substrate structure 11 and the rear substrate structure 12 are fixed in a state where the surface on which the protective film 18 is formed and the surface on which the partition wall 22 is formed face each other. A position on the plane of the partition wall 22 is disposed between the adjacent address electrodes 20. By disposing the barrier ribs 22 between the adjacent address electrodes 20, a discharge space 24 for dividing the surface of the dielectric layer 21 in the column direction DY corresponding to the position of each address electrode is formed.

In the discharge space 24 (specifically, the upper surface of the dielectric layer 21 on the address electrode 20 and the side surface of the barrier rib 22), a phosphor portion that is excited by vacuum ultraviolet rays and generates visible light of each color of R, G, and B. 23r, 23g, and 23b are formed.

Further, each discharge space 24 is filled with a gas such as a rare gas called a discharge gas at a predetermined pressure. As the discharge gas, for example, a mixed gas such as Xe-Ne whose Xe partial pressure ratio is adjusted to several to several tens of percent is used, and the pressure of the gas to be filled is 350 to 500 torr (about 47 to 67 kPa), for example. It can be.

The PDP 1 generates a discharge (sustain discharge) for each cell 25 in the discharge space 24, and is generated by the discharge (specifically, generated when an ion excited by the discharge transitions to a ground state). Thus, the R, G, B phosphor portions 23 are excited to emit light. When a mixed gas of Ne and Xe is used as the discharge gas, vacuum ultraviolet rays of 147 nm and 172 nm are generated as excitation light for exciting the phosphor parts 23. The wavelength of this vacuum ultraviolet ray (particularly the vacuum ultraviolet ray from the excimer) may have a certain range, but falls within the range of 147 nm to 180 nm.

Although FIG. 1 shows an example in which the partition wall 22 is formed in a strip shape, the arrangement of the partition wall is not limited to this. For example, in addition to the barrier ribs 22 as the first barrier ribs extending along the column direction DY, a second barrier rib extending along the row direction DX may be arranged to partition the discharge space 24 in a grid pattern. . In this case, since the discharge space 24 is partitioned into a box shape for each cell 25 by the barrier ribs 22 and the second barrier ribs, such a barrier rib structure is called a box structure. 1 shows an example in which the address electrode 20 is formed on the back substrate structure 12, the address electrode 20 can also be formed on the front substrate structure 11.

<About bright room contrast>
Next, the bright room contrast of the PDP will be described with reference to FIG. FIG. 2 is an explanatory diagram showing the relationship between external light incident on the PDP and display light from the PDP. In FIG. 2, the structure of the PDPs 1 and 2 is shown as a simplified model so that the relationship between the external light and the display light can be easily understood.

In FIG. 2, PDP1 and PDP2 are display devices whose display light P has emission luminance I _i and reflectance R _i , and a filter F having transmittance T _i is disposed on the display surface (front surface) side. . Here, the bright room contrast when the external light L luminance I ₀ was vertically incident on the display surface side of the PDP1 and C _i, C _i is given by Equation (1) below.

C _i = I _i / (T _i × R _i × I ₀ ) (1)
In order for the above formula (1) to hold, it is necessary that the term in which the external light L is reflected by the filter F is negligible. This is because the transmittance T _i of the filter F is several tens of percent. Since it is established if there is, it is established in a general display device.

Here, when there are two PDPs 1 and 2 (i = 1, 2), and the bright room contrast of the PDPs 1 and 2 is the same, the following equation (2) is established.

I ₁ / (T ₁ × R ₁ ) = I ₂ / (T ₂ × R ₂ ) (2)
Therefore, the following equation (3) is obtained by substituting the above equation (2) into the luminance ratio (T ₁ × I ₁ ) (T ₂ × I ₂ ) of the PDPs _{1 and} ₂ viewed from the observer of the PDPs _{1 and} ₂ .

(T ₁ × I ₁ ) / (T ₂ × I ₂ ) = (I ₁ ² × R ₁ ) / (I ₂ ² × R ₂ ) (3)
Therefore, under the condition that the same bright room contrast is obtained, the display brightness of the PDP 1 (the brightness seen by the observer) is advantageous in the inverse proportion of the reflectance. That is, if the luminance I ₀ of the external light L is constant, the bright room contrast C _i can be improved as the light emission luminance I _i is increased and the reflectance R _i is decreased.

Here, the PDP 1 shown in FIG. 1 has a structure in which a front substrate structure 11 and a rear substrate structure 12 disposed opposite to each other are overlapped. In the PDP 1, a member having a large influence on the reflectance of external light is the phosphor portion 23 of the back substrate structure 12. Hereinafter, a means for reducing the reflectance of the back substrate structure 12 on which the phosphor portion 23 is formed will be described.

FIG. 3 is an explanatory diagram showing a simplified model for explaining the effect of reducing the reflectivity of the structure of the back substrate structure of the PDP shown in FIG.

In FIG. 3, a phosphor portion 23 is formed on the back substrate 19 included in the back structure 12. This phosphor portion 23 is arranged with

phosphor portions

23r, 23g, and 23b that emit visible light of red, green, and blue, respectively.

First, the case where the phosphor part 23 is white will be described. Here, for easy understanding, it is assumed that the white phosphor portion 23 and the back substrate 19 are in a completely reflective state (a state where the reflectance is 100%).

When the phosphor part 23 and the back substrate 19 are in a completely reflective state, the reflectivity of the back substrate structure 12 is 1 (100%). Further, assuming that the luminance of visible light emitted from the phosphor portion 23 is I, all the light emission from the phosphor portion 23 is also reflected, and thus the emission luminance of the rear substrate structure 12 is also I.

Next, the case where the color tone of the phosphor part 23 is the same color tone as the visible light emitted from each

phosphor part

23r, 23g, 23b will be considered. In this case, when the reflectances at the

phosphor portions

23r, 23g, and 23b of the back substrate structure 12 are averaged, the average reflectance can be reduced to 1/3 (about 33%). On the other hand, the emission luminance of the rear substrate structure 12 is ideally set to I because all visible light emitted from the phosphor portion 23 is reflected.

Accordingly, when the bright room contrast is constant, the display luminance of the back substrate structure 12 is obtained by setting the color tone of the phosphor portion 23 to the same color tone as the visible light emitted by the

phosphor portions

23r, 23g, and 23b. (Luminance as viewed from the observer) can be made three times as high (as compared to the case where the phosphor portion 23 is white).

In the PDP 1 shown in FIG. 1, when the above technique is applied, a phosphor that is a mixture of inorganic pigment particles having red, green, and blue color tones and substantially white phosphor particles is used as the phosphor portion 23. It will be.

However, the effect of improving the display luminance cannot be obtained by simply mixing phosphor particles and inorganic pigment particles generally used as pigments.

For example, when the surface of the phosphor particles is covered with inorganic pigment particles, the inorganic pigment particles absorb the excitation light irradiated on the phosphor particles. For this reason, when the penetration length to the substance is an excitation source that is equal to or less than the average particle diameter of the inorganic pigment particles, such as vacuum ultraviolet rays that are the excitation source of PDP1, absorption of excitation energy by the inorganic pigment particles occurs, This loss is one of the causes that cause a decrease in the light emission luminance of the phosphor portion 23. Further, even if the excitation light reaches the phosphor particles, visible light emitted from the phosphor particles is absorbed by the inorganic pigment particles covering the surface. As a result, the light emission luminance of the phosphor portion 23 is lowered.

On the other hand, when the surface of the inorganic pigment particles is covered with the phosphor particles, it is possible to suppress a decrease in emission luminance. However, if the thickness of the phosphor particle layer formed on the surface of the inorganic pigment particle is too thick, scattering of the external light L irradiated to the phosphor particle layer occurs, and the reflectance increases due to this scattering. To do. In particular, when the average particle diameter of the phosphor particles is 1 to 5 μm, the reflectance increases by 10% or more with only the reflection component resulting from the scattering. For this reason, the reflectance of the phosphor portion 23 cannot be sufficiently reduced, and as a result, the above-described effect of improving the display luminance cannot be obtained.

The present inventor has studied a technique for reducing the reflectance of outside light while suppressing a decrease in light emission luminance or display luminance, and a band gap larger than the energy of excitation light and impurities formed in the band gap. And a phosphor part by mixing inorganic pigment particles having different energy widths from the HOMO level of the impurity level to the conduction band of the crystal matrix and the energy of the excitation light with the phosphor particles. The structure which forms 23 was found. Hereinafter, a specific configuration of the phosphor portion 23 will be described.

<Detailed structure of phosphor>
FIG. 4 is an enlarged cross-sectional view of the main part showing the detailed configuration of the phosphor part of the present embodiment, and FIG. 5 is a band diagram showing the energy band of the inorganic pigment constituting the phosphor part shown in FIG. The structure of the phosphor portion 23 shown in FIG. 4 is a structure common to the phosphor portion 23r for red, the phosphor portion 23g for green, and the phosphor portion 23b for blue.

4, the phosphor portion 23 includes phosphor particles (phosphor) 31 and inorganic pigment particles (inorganic pigment) 32 mixed with the phosphor particles 31. In FIG. 4, in order to show the distinction between the phosphor particles 31 and the inorganic pigment particles 32, these are shown as particles having a circular cross-sectional shape, but the structures of the phosphor particles 31 and the inorganic pigment particles 32 are the same. It is not limited to. For example, the phosphor particles 31 and the inorganic pigment particles 32 may have a flat cross-sectional shape. Further, for example, there are various heating processes in the manufacturing process of the PDP 1 (see FIG. 1). By this heating process, a part of the phosphor particles 31 and the inorganic pigment particles 32, the phosphor particles 31 each other, the inorganic pigment particles In some cases, a part of 32 may be fixed and integrated. The phosphor part 23 may be a mixture of a phosphor and an inorganic pigment, and may have a structure in which a part of each particle is fixed and integrated.

The material constituting the phosphor particles 31 is, for example, (Y, Gd) ₂ O ₃ : Eu for the phosphor particles 31r for red, and Zn ₂ SiO ₄ : Mn, YBO ₃ for the phosphor particles 31g for green. BaMgAl ₁₀ O ₁₇ : Eu ²⁺ can be exemplified as the phosphor particles 31b for: Tb and blue. The

phosphor particles

31r, 31g, and 31b emit red, green, and blue light, respectively, by being excited by excitation light that is an excitation source (in this embodiment, vacuum ultraviolet rays having wavelengths of 147 nm and 172 nm). To do.

On the other hand, the inorganic pigment particles 32 include, for example, ruby (Al ₂ O ₃ : Cr) for red inorganic pigment particles 32r, green sapphire (Al ₂ O ₃ : Fe) for blue inorganic pigment particles 31g, and blue Blue sapphire (Al ₂ O ₃ : Ti) is used for the inorganic pigment particles 32b. All of these are crystal bodies called corundum, in which 3d transition metals Cr, Fe (iron), and Ti (titanium) are introduced as impurities into alumina (Al ₂ O ₃ ), which is a crystal base. .

As shown in FIG. 5, alumina, which is the crystal matrix of the inorganic pigment particles 32, has a band gap W1 of about 10 eV between the conduction band CB and the valence band VB. On the other hand, vacuum ultraviolet rays having wavelengths of 147 nm and 172 nm, which are excitation sources of PDP1, are about 8.4 eV and 7.2 eV, respectively, and the band gap W1 of alumina is larger than the energy of the excitation light. The above-described light shielding of the excitation light by the inorganic pigment particles constituting the phosphor portion 23 is such that the inorganic pigment particles absorb the energy of the excitation light (electrons in the valence band VB are excited by the excitation light and transition to the conduction band CB. Generated). Since alumina used in this embodiment has a band gap W1 larger than the energy of excitation light, electrons in the valence band VB do not transition to the conductor CB even when irradiated with excitation light, and the absorption rate of excitation light is high. Low. That is, it is transparent to vacuum ultraviolet rays that are excitation light. As described above, spinel (MgAl ₂ O ₄ ) can be used as a material having a high transmittance with respect to vacuum ultraviolet rays, but alumina is more sensitive to light having a wavelength of 147 nm and 172 nm (vacuum ultraviolet light) than excitation light. Since the transmittance is high, it is more preferable.

Further, the reflectance of the phosphor portion 23 with respect to the external light is determined by the visible light absorption characteristics of the inorganic pigment particles 32. The visible light absorption characteristics of the inorganic pigment 32 are determined as follows. When a 3d transition metal element is introduced into alumina, the 3d transition metal ions are replaced with alumina Al ³⁺ ions. For example, when Cr is introduced as a 3d transition element, Cr ³⁺ ions are replaced with some Al ³⁺ ions, and at the substituted sites, as shown in FIG. 5 between the band gap W1 of alumina, which is the crystal matrix. Impurity levels are formed. 3d electron orbit of Cr ³⁺ ion, 3d orbital which was degenerate in 5fold is degenerated due to the influence of ligand field around Cr3 ⁺ ion, and _t2g orbital with low energy (triple degeneracy) If, it split into high e _g orbitals energy (double stuck), which is the impurity level.

Energy width W2 of the lower t _{2 g} orbitals and high e _g orbitals energy of this energy is a factor which determines the visible light absorption properties of the inorganic pigment particles 32. For example, in the case of ruby, the energy width W2 is about 2.3 eV, and when it is irradiated with external light (white light for simplicity), visible light in the wavelength range of purple and yellow-green has low energy. It is absorbed as the transition energy of electrons clogged in the t _2g orbital (as a result, ruby exhibits a complementary color, red). For this reason, since external light is absorbed by the inorganic pigment particles 32, the reflectance of the PDP 1 (see FIG. 1) can be reduced.

When a 3d transition metal is introduced into alumina, an impurity level having a strong light absorption characteristic in the visible light region is formed. Therefore, in addition to Cr, Fe, and Ti, the impurities are Sc (scandium), V (vanadium), Mn (manganese), Co (cobalt), Ni (nickel), Cu (copper), Zn (zinc), etc. can also be introduced. Two or more 3d transition metals can also be introduced. For example, some sapphires exhibiting a blue color tone have Fe and Ti introduced as impurities. In addition, the impurity level includes a defect level formed in alumina which is a crystal base. When this defect level has a visible light absorption characteristic, external light is emitted in the same manner as when impurities are introduced. Can be absorbed.

However, as described above, when the

inorganic pigment particles

32r, 32g, and 32b having the same color tone as that of the

phosphor particles

31r, 31g, and 31b are mixed with the

phosphor particles

31r, 31g, and 31b, respectively, Absorption of visible light emitted from the body particles 31 can be suppressed. Accordingly, it is possible to suppress a decrease in the light emission luminance of the phosphor portion 23. Therefore, any one or two or more impurities of Cr, Fe, or Ti having red, green, and blue color tones (having visible light absorption characteristics in the color tone complementary to the emission color of the phosphor particles 31) are contained. It is particularly preferable to introduce impurity levels.

Here, the impurity level formed by the impurities introduced into the alumina affects not only the absorption characteristic of visible light but also the absorption characteristic of vacuum ultraviolet light that is excitation light. More specifically, from the energy level of the highest energy orbital (HOMO) occupied by electrons among the low energy t _2g orbitals (hereinafter referred to as the HOMO level), the crystal matrix of alumina. When the energy width W3 to the conduction band CB is equal to the energy of vacuum ultraviolet light as excitation light, electrons occupying the orbit of the HOMO level absorb the vacuum ultraviolet light as excitation energy and transition to the conduction band CB of alumina. Therefore, in order to prevent absorption of vacuum ultraviolet rays, the energy width W3 and the energy of vacuum ultraviolet rays need to be different. In the case of the ruby shown in FIG. 5, the energy width W4 from the valence band VB of alumina to the HOMO level is about 0.9 eV, and the energy width W3 is 9.1 eV. As described above, since the energy width W3 is larger than the energy of the excitation light, the absorption of the excitation light due to the impurity level can be prevented or suppressed.

In the actual excited state, electrons are excited by the absorption of visible light, which is complicated as described in the Tanabe / Ogino diagram. However, the present inventor has the energy level of the t _2g orbit with low energy. Of these, if the energy width W3 from the highest energy level (HOMO level) to the conduction band CB of alumina is different from the energy of vacuum ultraviolet rays, the decrease in emission luminance due to absorption of excitation light is effectively negligible. It was confirmed that it can be prevented.

Further, for the green sapphire (Al ₂ O ₃ : Fe) which is the green inorganic pigment particle 31g and the blue sapphire (Al ₂ O ₃ : Ti) which is the blue inorganic pigment particle 32b shown in FIG. The energy width W4 from the band VB to the HOMO level is smaller than 1 eV. Therefore, since the energy width W3 is 9 eV or more, which is larger than the energy of the excitation light, absorption of the excitation light due to the impurity level can also be prevented.

As described above, according to the present embodiment, the crystal matrix of the inorganic pigment particles 32 mixed with the phosphor particles 31 is alumina having a band gap W1 larger than the energy of the excitation light, thereby absorbing the excitation light. Can be prevented or suppressed. Further, by forming an impurity level (impurity level having visible light absorption characteristics) in the band gap W1, it is possible to absorb external light irradiated on the phosphor portion and reduce the reflectance. Further, by making the energy width W3 from the HOMO level of the impurity level to the conduction band of the crystal base different from the energy of the excitation light, the transition of electrons from the HOMO level to the conduction band is prevented or suppressed. be able to. Accordingly, absorption of excitation light due to the impurity level can be prevented or suppressed.

<Relationship of particle size between phosphor particles and inorganic pigment particles>
By the way, the particle diameter of the phosphor particles is generally about 1 to 10 μm. On the other hand, the particle diameter of general inorganic pigment particles is 1 μm or less, typically 5 to 500 nm so that they can be dispersed even when mixed in a liquid such as ink. That is, the particle diameter of the inorganic pigment particles is generally smaller than the particle diameter of the phosphor particles.

For example, the particle size of the red pigment described in Patent Document 1 (manufactured by Sakai Chemical Industry Co., Ltd .: “FRO-3”) is about 100 nm. The specific surface area of the green pigment (manufactured by Nissei Kagaku Kogyo Co., Ltd .: “TM Green # 3340”) is 100 m ² / g, and the particle diameter is about 10 to 20 nm. The particle diameter of the blue pigment (Asahi Sangyo Co., Ltd .: “Asahi Super Blue CR”) is about 200 nm.

However, in the present embodiment, as shown in FIG. 4, the particle diameter (average particle diameter) of the inorganic pigment particles 32 is larger than the particle diameter (average particle diameter) of the phosphor particles 31. Hereinafter, the effect obtained by making the particle diameter of the inorganic pigment particles 32 larger than the particle diameter (average particle diameter) of the phosphor particles 31 will be described.

The alumina used as the crystal matrix of the inorganic pigment particles 32 in the present embodiment has a band gap W1 (see FIG. 5) of 10 eV, which is larger than the energy in the visible light region. Therefore, alumina itself is transparent not only for excitation light but also for visible light. The inorganic pigment particles 32 obtain visible light absorption characteristics by, for example, introducing impurities into the band gap W1 to form impurity levels.

However, not all Al ³⁺ ions in alumina can be replaced with impurity ions, and the ratio of introducing impurities is limited. Accordingly, the inorganic pigment particles 32 used in the present embodiment have a lower amount of visible light absorption per unit surface area than the above-described generally used inorganic pigments.

Therefore, in the present embodiment, the particle diameter (average particle diameter) of the inorganic pigment particles 32 is larger than the particle diameter (average particle diameter) of the phosphor particles 31. Thereby, since the surface area ratio which the inorganic pigment particle 32 occupies in the fluorescent substance part 23 shown in FIG. 1 can be enlarged, external light can fully be absorbed as the fluorescent substance part 23 whole. Therefore, the reflectance of the phosphor part 23 can be reduced.

<Manufacturing method of PDP>
Next, a method for manufacturing the PDP according to the present embodiment will be described. The manufacturing process of the PDP 1 is roughly divided into a process of preparing the front substrate structure 11 and the rear substrate structure 12 shown in FIG. 1, and the front substrate structure 11 and the rear substrate structure 12 facing each other through the discharge space 24. And arranging and assembling. In the present embodiment, the step of forming the phosphor portion 23 in the discharge space 24 formed in the back substrate structure 12 will be described in detail.

FIG. 6 is an explanatory diagram showing a manufacturing flow of the phosphor portion 23 included in the PDP of the present embodiment. The phosphor part 23 shown in FIG. 1 is formed as follows, for example.

(A) First, phosphor particles 31 and inorganic pigment particles 32 having an average particle diameter larger than the average particle diameter of the phosphor particles 31 are prepared in the preparation step shown in step S1. In this step, impurity levels are formed in the band gap W1 (see FIG. 5) of the inorganic pigment particles 32.

(B) Next, the inorganic pigment particles 32 and the phosphor particles 31 are mixed in the mixing step shown in step S2 to obtain a phosphor mixture 33. In this step, the inorganic pigment particles 32 and the phosphor particles 31 are mixed so that they are dispersed. Therefore, various mixing methods can be used as long as each particle can be dispersed and mixed. For example, mixing can be performed using a mixer or the like. Further, for example, the phosphor particles 31 and the inorganic pigment particles 32 can be dispersed and mixed in the solution.

Further, in this step, in order to control the surface area ratio of the inorganic pigment particles 32 in the phosphor portion 23 to be finally formed, in this coating step, the surface areas of the inorganic pigment particles 32 and the phosphor particles 31 to be added are determined. It is preferable to determine the addition amount by measuring the sum. By managing the total surface area of each particle at the stage of mixing, the surface area ratio of the inorganic pigment particles 32 in the phosphor portion 23 can be easily controlled. As a result, the reflectance with respect to the external light of the phosphor part 23 can be controlled.

When the

phosphor parts

23r, 23g, and 23b (see FIG. 1) include different

inorganic pigment particles

32r, 32g, and 32b (see FIG. 4), the red phosphor particles 31r and the red inorganic pigment are used. Particles 32r, green phosphor particles 31g and green inorganic pigment particles 32g, and blue phosphor particles 31b and blue inorganic pigment particles 32b are mixed separately.

(C) Next, a phosphor paste 34 is obtained by mixing the phosphor mixture 33 in a vehicle composed of an organic solvent, an organic binder agent, and the like in the pasting step shown in step S3.

In this pasting step, the phosphor mixture 33 may be dispersed in the phosphor paste 34, and the mixing method is not particularly limited.

(D) Next, in the phosphor paste application step shown in step S4, the phosphor paste 34 is applied to the region where the phosphor part 23 shown in FIG. 1 is formed. Specifically, a plurality of address electrodes 20 are formed in advance on the surface of the back substrate 19 shown in FIG. 3, then a dielectric layer 21 is formed so as to cover the address electrodes 20, and then the surface of the dielectric layer 21 is formed. The barrier ribs 22 that define the plurality of discharge spaces 24 are formed. In step S4, the phosphor paste 34 is applied to the discharge space 24 (bottom surface and side wall) partitioned by the barrier ribs 22 by, for example, a screen printing method or a dispensing method.

Needless to say, in order to form the

phosphor portions

23r, 23g, and 23b shown in FIG. 1, the phosphor pastes 34 for red, green, and blue are separately applied.

(E) Next, the organic compound components (organic solvent and organic binder agent) contained in the phosphor paste 34 are removed in the drying and firing steps shown in step S5, and the phosphor portion 23 is obtained.

The phosphor part 23 obtained in this way is formed in a state where the primary particles of the inorganic pigment particles 32 and the phosphor particles 31 are dispersed, and therefore when set in the mixing step shown in step S2. The surface area ratio is reflected.

Further, in this step, since the phosphor paste 34 is heated, as described above, a part of the phosphor particles 31 and the inorganic pigment particles 32, a part of the phosphor particles 31 and a part of the inorganic pigment particles 32 are fixed. Integrate.

As described above, in the present embodiment, in the step of mixing phosphor particles 31 and inorganic pigment particles 32 shown in step S2, the surface areas of phosphor particles 31 and inorganic pigment particles 32 are measured, and the amount of each particle added is determined. By determining, the reflectance with respect to the external light of the fluorescent substance part 23 can be reduced stably.

As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment of the invention, and various modifications can be made without departing from the scope of the invention. is there.

For example, although the PDP has been described as an application example of the display device, the display device can be widely applied to any display device that displays an image by exciting a phosphor with light.

The present invention can be applied to a display device such as a PDP that displays an image by exciting a phosphor with light.

Claims

A phosphor mixture having phosphor particles that emit light when excited with excitation light, and inorganic pigment particles mixed with the phosphor particles,
The inorganic pigment particles have a crystal matrix having a band gap larger than the energy of the excitation light and an impurity level formed in the band gap;
A phosphor mixture, wherein an energy width from a HOMO level of the impurity level to a conduction band of the crystal base is different from an energy of the excitation light.
The phosphor mixture according to claim 1,
A phosphor mixture, characterized in that the wavelength of the excitation light is vacuum ultraviolet light having a wavelength of 147 nm to 180 nm.
The phosphor mixture according to claim 2,
The phosphor mixture, wherein the crystal matrix is alumina, and the impurity level is formed by impurities introduced into the crystal matrix.
The phosphor mixture according to claim 3,
The phosphor mixture, wherein the impurity is substituted with aluminum of the crystal matrix.
The phosphor mixture according to claim 3,
The phosphor mixture, wherein the impurity is a 3d transition metal.
The phosphor mixture according to claim 3,
The phosphor mixture is characterized in that the impurity is one or more of Cr (chromium), Fe (iron), and Ti (titanium).
The phosphor mixture according to claim 1,
The phosphor mixture, wherein the inorganic pigment particles have a particle size larger than that of the phosphor particles.
A substrate,
Partition walls that divide one surface side of the substrate into a plurality of discharge spaces;
A phosphor portion formed in each of the plurality of discharge spaces,
The phosphor portion is
A phosphor that emits light when excited by excitation light, and an inorganic pigment mixed with the phosphor,
The inorganic pigment has a crystal matrix having a band gap larger than the energy of the excitation light and an impurity level formed in the band gap;
A plasma display panel, wherein an energy width from a HOMO level of the impurity level to a conduction band of the crystal base is different from an energy of the excitation light.
The plasma display panel according to claim 8, wherein
A plasma display panel characterized in that the wavelength of the excitation light is vacuum ultraviolet light having a wavelength of 147 nm to 180 nm.
The plasma display panel according to claim 9, wherein
The plasma display panel according to claim 1, wherein the crystal matrix is alumina, and the impurity level is formed by impurities introduced into the crystal matrix.
The plasma display panel according to claim 10, wherein
The plasma display panel, wherein the impurities are substituted with aluminum of the crystal base.
The plasma display panel according to claim 10, wherein
The plasma display panel, wherein the impurity is a 3d transition metal.
The plasma display panel according to claim 10, wherein
The plasma display panel according to claim 1, wherein the impurity is one or more of Cr (chromium), Fe (iron), and Ti (titanium).
The plasma display panel according to claim 8, wherein
The phosphor portion is formed of a mixture of phosphor particles that are particles of the phosphor and inorganic pigment particles that are particles of the inorganic pigment, and the particle size of the inorganic pigment particles is the particle size of the phosphor particles. A plasma display panel characterized by being larger than.