JP2012064347A - Method of forming light extracting structure, and method of manufacturing light-emitting board having light extracting structure and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form a structure in which materials having mutually different refraction factors are periodically arranged and which is required as a light extracting structure, without leaving high polymer materials.SOLUTION: A coated film of an inorganic particle dispersion in which inorganic particles 12 are dispersed in a liquid dispersion medium 22 is formed on a capture layer 21 containing a high polymer, and the liquid dispersion medium 22 is volatilized to form a sedimentary layer of the inorganic particles 12 on the capture layer 21. The capture layer 21 is then heated, the inorganic particles 12 in the undermost layer of the sedimentary layer are embedded in the capture layer 21 to capture the inorganic particles, the capture layer is then calcined after the excessive inorganic particles 12 that have not been captured are removed, and the capture layer 21 is thereby removed and the inorganic particles 12 that have been captured by the capture layer 21 is bonded to a transparent board 8 to make a light extracting structure 9 by embedding the inorganic particles 12 with an inorganic binder 13 having a different refraction factor from the inorganic particles 12.

Description

  The present invention relates to a method for forming a light extraction structure used for facilitating extraction of light generated from a light source to the outside of a display surface in order to improve luminance of an image display device that displays an image by light emission. The present invention also relates to a light emitting substrate having a light extraction structure and a method for manufacturing an image display device.

  The light extraction structure is a structure in which materials having different refractive indexes are periodically arranged, and is usually configured by forming a fine uneven pattern by a photolithography process used for general semiconductor microfabrication. However, when the pitch of the fine concavo-convex pattern is about 2 μm or less, an expensive exposure apparatus and a complicated process are required, and the manufacturing cost becomes very high.

  Therefore, conventionally, a method described in Patent Document 1 has been proposed as a method for easily forming a fine concavo-convex pattern used as a light extraction structure. That is, in the method described in Patent Document 1, while preparing a particle dispersion in which particles are dispersed in a liquid dispersion medium, a trapping layer containing a polymer is formed on a substrate, and the trapping layer is formed on the trapping layer. A coating film of the particle dispersion is formed. After the liquid dispersion medium is volatilized from the coating film to form a deposited layer of the particles on the trapping layer, the particles in the lowermost layer of the deposited layer are only heated by heating the trapping layer to a glass transition point or higher. Only embedded in the acquisition layer by capillary action. Then, the particle deposition layer is immersed in a liquid to remove particles that are not embedded in the trapping layer, and a single particle layer in which the lowermost layer of the particles is arranged in the trapping layer is formed to form fine irregularities A pattern.

Japanese Patent No. 4085578

  In the above conventional method, a structure in which materials having different refractive indexes, which are necessary as a light extraction structure, are periodically arranged is formed by arranging particles. Therefore, compared to the case where a photolithography process is used. There is an advantage that it can be easily formed. However, the fine concavo-convex pattern obtained by the conventional method has a problem that it cannot be used for an image display device that requires a high vacuum because the trapping layer made of a polymer material remains. . For example, in an image display device that displays an image by exciting an electron beam of a phosphor, the interior is required to be in a high vacuum in order to maintain the performance and life of the electron source. However, since a large amount of gas is generated from the polymer material in a vacuum atmosphere, the required degree of vacuum cannot be maintained and the function cannot be maintained.

  An object of the present invention is to make it possible to easily form a structure necessary for a light extraction structure in which materials having different refractive indexes are periodically arranged without leaving a polymer material. Another object of the present invention is to make it possible to easily manufacture an image display device with high brightness.

The first of the present invention is a step of forming a capture layer on a transparent substrate;
Providing an inorganic particle dispersion liquid in which inorganic particles are dispersed in a dispersion medium on the trapping layer, volatilizing the dispersion medium, and forming a deposition layer of the particles on the trapping layer;
Embedding and trapping inorganic particles in the bottom layer of the deposited layer in the trapping layer;
Removing inorganic particles not captured by the capturing layer, and forming an inorganic particle layer in which the inorganic particles captured by the capturing layer are disposed in the capturing layer;
Heating the transparent substrate having the inorganic particle layer, removing the capture layer and bonding the inorganic particles constituting the inorganic particle layer to the transparent substrate;
And a step of embedding the inorganic particles adhered to the transparent substrate with an inorganic binder having a refractive index different from that of the inorganic particles.

  According to a second aspect of the present invention, in the method for manufacturing a light emitting substrate having a light extraction structure for extracting light generated from the light emitter layer, the light extraction structure is formed as the light extraction structure according to the first aspect of the present invention. It is a manufacturing method of the light emitting board | substrate characterized by forming by the method.

  Further, a third aspect of the present invention is a method of manufacturing an image display device having a light extraction structure for extracting light generated from a light emitting layer that displays an image by light emission, wherein the light extraction structure is the first of the present invention. It is formed with the formation method of the light extraction structure concerning this.

  In the present invention, a structure in which materials having different refractive indexes, which are necessary as a light extraction structure, are periodically arranged is formed by arranging inorganic particles. Therefore, compared to the case where a photolithography process is used. Formation is easy and manufacturing cost can be reduced. In the present invention, since the trapping layer is removed by baking, even if the trapping layer contains a polymer, the trapping layer can be used to form a light extraction structure of an image display device that requires high vacuum.

1A and 1B are diagrams illustrating an example of an image display device having a light extraction structure, in which FIG. 1A is a schematic perspective view with a part cut away, FIG. 2B is a schematic plan view of an electron source substrate, and FIG. It is an expanded sectional view. It is explanatory drawing of the procedure of the formation method of the light extraction structure which concerns on this invention. It is explanatory drawing of the evaluation method of light extraction efficiency, (a) is a top view of the transparent substrate which has the light extraction structure which is evaluation object, (b) is a schematic explanatory drawing of an evaluation apparatus.

  As an image display device that is one of the objects to be manufactured according to the present invention, for example, a field emission display (FED), a cathode ray tube display (CRT), a plasma display (PDP) or the like displays an image by emitting light from a phosphor layer. In addition to the image display device, an electroluminescence display (EL), a light emitting diode display (LED), and the like can be given. Among these, the present invention can be preferably applied to FEDs and ELs that are preferably provided with a light extraction structure in order to improve luminance. Hereinafter, specific embodiments of the present invention will be described using FEDs as examples. Explained.

  FIG. 1 is a view showing an example of an image display device (FED) having a light extraction structure. In FIG. 1, 1 is a rear plate, and 2 is a face plate which is a light emitting substrate.

  The rear plate 1 includes m scanning wirings 3, n modulation wirings 4, and an electron source substrate 6 having a plurality of electron-emitting devices 5 connected to the scanning wirings 3 and the modulation wirings 4 on the inner surface side. The rear substrate 7 is provided on the outer surface side of the electron source substrate 6. The m scanning wirings 3 are connected to the terminals Dx1, Dx2,. The n modulation wirings 4 are connected to the terminals Dy1, Dy2,. An interlayer insulating layer (not shown) is provided between the m scanning wirings 3 and the n modulation wirings 4 to electrically insulate them. The electron-emitting device 5 is driven in a matrix by electrical signals input from terminals Dx1, Dx2,... Dxm and terminals Dy1, Dy2,.

  The face plate 2 is a member constituting the image display surface side, and has a structure in which a light extraction structure 9, an anode electrode 10, and a phosphor layer 11 are sequentially formed on the inner surface side of the transparent substrate 8. The light emitting substrate has a substrate configuration including a phosphor layer 11 that is a light emitting layer in SED, CRT, and PDP. In EL and LED, a layer that emits light using the electroluminescence effect is a light emitting layer, and a substrate configuration including the layer is a light emitting substrate. As a transparent substrate, substrates, such as float glass, such as blue plate glass and non-alkali glass, can be used, for example. The light extraction structure 9 is composed of inorganic particles 12 arranged in a single layer and an inorganic binder 13 having a refractive index different from that of the inorganic particles and embedded with the inorganic particles 12. The anode electrode 10 is made of a transparent conductive material such as ITO. The phosphor layer 11 emits light when irradiated with electrons from the electron-emitting device 5 included in the rear plate, and contains a large number of phosphor particles. A high voltage terminal 14 is connected to the anode electrode 10 so that, for example, a DC voltage of several kV is supplied. This voltage is an accelerating voltage for applying sufficient energy to excite phosphor particles to electrons emitted from the electron-emitting device 5. The positions of the anode electrode 10 and the phosphor layer 11 can be interchanged, and when the anode electrode 10 is the innermost side, a metal electrode that is not transparent can be obtained.

  The rear plate 1 and the face plate 2 are arranged such that the frame body 15 is sandwiched between the outer peripheral portions of the rear plate 1 and the inner surfaces are spaced apart from each other. The rear plate 1 and the face plate 2 are joined to the frame body 15 in a sealed state via frit glass or the like to form a panel-like sealed container, and the inside is in a vacuum atmosphere. Since the back plate 7 is provided mainly for the purpose of reinforcing the strength of the electron source substrate 6, the separate back substrate 7 can be omitted if the electron source substrate 6 itself has sufficient strength. In addition, by installing a support body (not shown) called a spacer between the rear plate 1 and the face plate 2 inside the frame body 15, the strength against atmospheric pressure is improved. You can also.

  As the image display device becomes higher in definition, the area of the phosphor layer 11 constituting one pixel is also reduced. In order to facilitate the formation of the phosphor layer 11 having a small area, the average particle diameter of the phosphor particles constituting the phosphor layer 11 is preferably 1000 nm or less, and more preferably 100 nm or less. The average particle diameter of the phosphor particles can be measured by estimating the Stokes diameter of the nanoparticles by a dynamic light scattering method. Specifically, it can be measured using Zetasizer Nano ZS [manufactured by Sysmex Corporation]. When the phosphor particles having the particle diameter as described above are used, the amount of light extracted to the display surface side is reduced and the luminance of the image is lowered as compared with the case where the phosphor particles having a large particle diameter are used. The light extraction structure 9 is for allowing more light generated by the light emission of the phosphor particles to be extracted to the outside of the face plate 2 and displaying an image with high luminance.

  Next, a method for forming the light extraction structure 9 and a method for manufacturing the face plate 2 and the image display device will be described.

[1] Formation of trapping layer [FIG. 2 (a)]
As shown in FIG. 2A, the capturing layer 21 is formed on the transparent substrate 8. As the transparent substrate 8, a glass substrate can be preferably used. As the trapping layer 21, a layer containing a polymer compound can be preferably used. Since the trapping layer 21 is usually patterned according to the size and shape of the pixel and adheres the inorganic particles 12 by heating, a thermoplastic photosensitive resin can be preferably used. Moreover, in the manufacturing method of this invention, it is preferable to control the surface charge of the acquisition layer 21 with respect to the dispersion medium 22 [refer FIG.2 (b)] mentioned later. For this reason, it is preferable to select a material that can easily control the surface charge as the constituent material of the trapping layer 21. Specifically, it is preferable to select a polymer having a polar functional group such as —OH or —COOH. Furthermore, the film thickness of the trapping layer 21 is in the range of not more than the median diameter (median value of particle size distribution) of the inorganic particles 12 to 1/4 or more of the median diameter in order to facilitate the formation of a single particle layer to be described later. It is preferable to set.

  The formation method of the acquisition layer 21 is not specifically limited. Generally, it can be formed by applying a solution of the constituent material of the capturing layer 21 onto the transparent substrate 8. The method for applying the solution is not particularly limited. For example, widely known coating methods such as spin coating, dipping, and slit coating can be used. Among them, the slit coat method is preferable because a thin film having a predetermined pattern can be formed in a large area.

  This is not necessary when the light extraction structure 9 is formed on the entire surface of the transparent substrate 8 or when the capturing layer 21 is formed in a predetermined pattern by printing or the like. Usually, the pattern is formed so as to correspond to the pixel pattern of the image display device. Ning. Here, the patterning method is not particularly limited, but a general photolithography method can be used. In this case, a photosensitive resin is used as a constituent material of the capturing layer 21.

[2] Surface treatment of trapping layer Immediately before applying the inorganic particle dispersion shown below, the trapping layer 21 is subjected to a surface treatment (primary treatment), and a dispersion medium 22 of an inorganic particle dispersion described later [FIG. It is preferable to increase the affinity with reference. That is, it is preferable that the surface potential of the trapping layer 21 is set higher than that of the dispersion medium 22. Specifically, when the dispersion medium 22 is water, the surface treatment is preferably performed so that the water contact angle on the surface of the trapping layer 21 is 15 ° or less, and the water contact angle is 10 ° or less. A surface treatment is more preferable. As the surface treatment method of the trapping layer 21, ultraviolet irradiation or plasma treatment can be used. Here, when the constituent material of the trapping layer 21 is a polymer having a polar functional group such as —OH group or —COOH group, the surface polarity is further increased by ultraviolet irradiation or plasma treatment, and the water contact angle is 15 ° or less. Can be.

[3] Application of inorganic particle dispersion [FIG. 2 (b)]
Next, an inorganic particle dispersion liquid composed of the inorganic particles 12 and the dispersion medium 22 is prepared, and this inorganic particle dispersion liquid is applied onto the trapping layer 21. Hereinafter, the inorganic particles 12, the dispersion medium 22, the inorganic particle dispersion liquid in which these are mixed, and the coating thereof will be described.

-Inorganic particles-
The inorganic particles 12 contained in the inorganic particle dispersion are particles of a material having a glass transition point or a melting point higher than the glass transition point of the transparent substrate 8 so as not to be deformed or adhered to each other at the time of firing described later. Further, it is translucent and has a refractive index different from that of an inorganic binder 13 described later, and forms a structure in which materials having different refractive indexes are periodically arranged together with the inorganic binder 13. The inorganic particles 12 are preferably a material having a large refractive index difference from the inorganic binder 13. Therefore, among inorganic materials, a material having a large or small refractive index is preferable. Examples of the material having a high refractive index include titanium oxide, and examples of the material having a low refractive index include silica. Further, the form of the inorganic particles 12 is a spherical shape with a high roundness and a narrow particle size distribution so that a structure in which a material having a large refractive index and a material having a small refractive index are regularly arranged can be formed. desirable. Here, the particle size distribution is defined by the following formula (1).

    Particle size distribution (%) = (Particle size standard deviation / Average particle size) × 100 (1)

  In the formula (1), the average particle diameter represents an average value obtained by measuring the diameters of 100 particles randomly extracted. The particle size standard deviation represents the standard deviation for the 100 particles. The particle size distribution obtained by the formula (1) is preferably 5% or less, more preferably 2% or less. Specifically, as for the particle diameter of the inorganic particles 12 contained in the inorganic particle dispersion liquid, 100 particles are randomly selected from the inorganic particles 12 photographed with an electron microscope, and the 100 inorganic particles 12 are imaged. Obtained by analysis. The particle diameter corresponds to the pitch of the light extraction structure (fine concavo-convex pattern) described later. The particle size of the inorganic particles 12 used when producing the image display device is preferably 3000 nm or less, and more preferably 200 nm to 2000 nm.

  In the forming method of the present invention, in order to regularly arrange the inorganic particles 12 on the trapping layer 21, it is preferable to consider the zeta potential of the inorganic particles 12 in the state of being dispersed in the dispersion medium 22. Specifically, as a condition for arranging the inorganic particles 12 regularly, the surface charge of the inorganic particles 12 in the dispersion medium and the surface charge of the trapping layer 21 are preferably negative potentials. This potential is more preferable as the absolute values thereof are higher. In this way, the individual inorganic particles 12 become slippery due to electrostatic repulsion on the transparent substrate 8 and are arranged by the capillary force by the dispersion medium 22. If the electrostatic repulsion is weak, the interaction with the transparent substrate 8 causes the inorganic particles 12 to be easily adsorbed on the transparent substrate 8, and the arrangement due to the capillary force is likely to be hindered. This leads to deterioration of regularity.

  The zeta potential of the inorganic particles 12 can be measured with a commercially available zeta potential measuring device. In the case where water is used as the dispersion medium 22, the absolute value of the average zeta potential of the inorganic particles 12 is preferably 80 mV or more. When the dispersion medium 22 is a polar dispersion medium such as water, as a method for increasing the value of the zeta potential of the inorganic element 12, the surface of the inorganic particle 12 can be increased by increasing the number of polar functional groups on the surface of the inorganic particle 12. Is modified with a polar molecule.

-Dispersion medium-
The dispersion medium 22 is not particularly limited. For example, water, various organic solvents, or a mixture thereof can be used. In order to arrange the inorganic particles 12 more regularly on the trapping layer 21, it is preferable to use a liquid having a large surface tension as the dispersion medium 22. The dispersion medium 22 is preferably a liquid that does not dissolve or swell the trapping layer 21. In the present invention, water is most preferred.

-Dispersion concentration of inorganic particles-
In order to regularly arrange the inorganic particles 12 on the trapping layer 21, the dispersion concentration of the inorganic particles 12 in the dispersion medium 22 is also important. In the present invention, the dispersion concentration of the inorganic particles 12 is preferably 30% by weight to 40% by weight.

-Application of inorganic particle dispersion (application)-
The application method of the inorganic particle dispersion is not particularly limited, and can be applied by any method such as a dipping method, a spray coating method, or a scan coating method. If the amount of liquid at the time of application is excessively increased, the amount of the dispersion medium 22 increases accordingly, and the force that the dispersion medium 22 pushes the inorganic particles 12 increases. When this force is too large, the arrangement of the inorganic particles 12 placed on the trapping layer 21 is deteriorated. For this reason, in the present invention, a technique that can be applied over a wide range with a small amount of liquid, such as spray coating, is preferred. Specifically, the liquid amount at the time of application is preferably in the range of 0.005 ml / cm ^{2 to} 0.02 ml / cm ² . If the surface potential of the inorganic particles 12 and the surface potential of the trapping layer 21 are set to the same charge (negative charge), electrostatic repulsion occurs between the polymer layer 16 and the particles 17, thereby The arrangement state is improved.

[4] Formation of inorganic particle deposition layer [FIG. 2 (c)]
Next, the coating film of the inorganic particle dispersion is dried, and the dispersion medium 22 [see FIG. 2B] is volatilized to form a deposited layer of the inorganic particles 12. In the process of removing the dispersion medium 22 from the coating film, the inorganic particles 12 are placed and arranged on the trapping layer 21. As described above, electrostatic repulsion occurs between the inorganic particles 12 and the trapping layer 21. Nevertheless, the inorganic particles 12 are placed and arranged on the trapping layer 21 in spite of the static repulsion. This is because a force stronger than the electrostatic repulsion force due to the electric repulsion, that is, the capillary force of the dispersion medium 22 works. The drying method after the application is not particularly limited, but the transparent substrate 8 can be appropriately dried by leaving it at about 100 ° C. for about 20 minutes. In addition, when the substrate is properly applied by spraying, the transparent substrate 8 is particularly heated. It is also possible to dry by natural drying without doing. When the coating film is dried and the dispersion medium 22 is completely removed, a deposited layer of inorganic particles 12 is formed on the trapping layer 21 as shown in FIG.

[5] Capturing inorganic particles in the trapping layer [FIG. 2 (d)]
Next, the trapping layer 21 is heated to the glass transition point or melting point of the polymer that is the constituent material. Then, with the fluidization of the trapping layer 21, the lowermost inorganic particles 12 of the deposited layer of the inorganic particles 12 sink into the trapping layer 21 and are embedded and trapped in the trapping layer 21. The inorganic particle layer in which the inorganic particles 12 trapped in the trapping layer 21 are arranged in the trapping layer 21 is a single particle layer in which only the lowermost inorganic particles 12 of the deposited layer sink into the trapping layer 21 and are trapped. It is preferable that A substantially linear relationship is obtained between the submerged depth of the inorganic particles 12 into the trapping layer 21 and the heating temperature. For this reason, in order to make it easy to obtain the single particle layer, by selecting an appropriate heating temperature, ¼ to ３ of the diameter of each inorganic particle 12 is embedded in the trapping layer 21. Is preferred. If the embedding depth of the inorganic particles 12 is too shallow, the inorganic particles 12 are likely to fall off during subsequent cleaning. In addition, if the embedding depth is too deep, not only the inorganic particles 12 at the lowest layer of the deposited layer but also the second and higher inorganic particles 12 are captured by the capturing layer 21 and it is difficult to obtain a single particle layer after the subsequent cleaning step. Become.

[6] Removal of excess inorganic particles [FIG. 2 (e)]
Next, the inorganic particles 12 other than the inorganic particles 12 captured by the capturing layer 21 are removed. The specific method of removal is not particularly limited. For example, ultrasonic cleaning or high pressure shower cleaning can be used. After the cleaning, as shown in FIG. 2 (d), only the inorganic particle layer in which the inorganic particles 12 captured by the capturing layer 21 are disposed on the capturing layer 21 remains.

[7] Removal of trapping layer by heating (firing) [FIG. 2 (f)]
The transparent substrate 8 having the inorganic particle layer is heated at a temperature equal to or lower than the annealing point of the transparent substrate 8 to remove the capturing layer 21 and adhere the inorganic particles 12 constituting the inorganic particle layer to the transparent substrate 8. By removing the trapping layer 21, it is possible to form the light extraction structure 9 that does not emit gas even when an electron beam hits it in a vacuum, for example. When heating is performed at a temperature exceeding the annealing point, irregular distortion occurs in the transparent substrate 8, and it becomes difficult to manufacture a particularly large image display device. The lower limit of the heating temperature is sufficient as long as it can cause adhesiveness to the transparent substrate 8. Specifically, the temperature of the strain point of the transparent substrate 8 is −20 ° C. or higher. When the strain point of the transparent substrate 8 is lower than −20 ° C., it is difficult to obtain a sufficient adhesive force of the inorganic particles 12 to the transparent substrate 8. The lower limit temperature of this heating can be lowered by adding frit glass to the trapping layer 21. That is, by containing 0.1 to 5% by weight of frit glass, if the transparent substrate 8 is heated at a temperature higher than the softening point of the frit glass, the inorganic particles 12 are sufficiently bonded to the transparent substrate 8. It becomes possible to do. If the addition amount of the frit glass is less than 0.1 w%, it is difficult to obtain the necessary adhesive strength at the softening point of the frit glass, and if the addition amount of the frit glass exceeds 5% by weight, the light transmittance decreases or coloring Occurs and it becomes difficult to obtain sufficient light extraction efficiency. Usually, since the softening point of the frit glass is lower than the strain point of the transparent substrate 8 -20 ° C, the lower limit temperature of heating can be lowered.

[8] Embedding with inorganic binder [Fig. 2 (g)]
Subsequently, the inorganic particles 12 are filled with a light-transmitting inorganic binder 13 having a refractive index different from that of the inorganic particles 12 bonded to the transparent substrate 8 to form a light extraction structure 9. The embedding with the inorganic binder 13 can be performed by applying a precursor solution of the inorganic binder 13 and baking it. The inorganic binder 13 is a material having a refractive index different from that of the inorganic particles 12. When the inorganic particles 12 have a low refractive index, a material having a high refractive index is selected. When the inorganic particles 12 have a high refractive index, the refractive index is low. Low material is selected. Examples of the inorganic binder 13 having a high refractive index include a TiO ₂ film (refractive index of 2.0 to 2.3) obtained by coating and baking a peroxotitanic acid solution. On the other hand, examples of the inorganic binder 13 having a low refractive index include a film made of a glass material such as SiO ₂ (refractive index of 1.2 to 1.5) obtained by coating and baking a dibutyl ether solution of polysilazane. it can.

[9] Manufacture of face plate [FIGS. 2 (h), (i)]
After the light extraction structure 9 is formed as described above, the transparent anode electrode 10 is formed thereon. The transparent anode electrode 10 is formed by depositing a transparent conductive film such as an ITO film, a ZnO film, or a SnO film. The refractive index of the transparent conductive film described above is typically in the range of 1.8 to 2.2. Thereafter, the face plate 2 can be obtained by further forming a phosphor layer 11 as a light emitting layer on the anode electrode 10.

[10] Manufacture of Image Display Device The image display device described in FIG. 1 can be easily manufactured using the face plate 2 manufactured as described above. First, the face plate 2 and the rear plate 1 manufactured by the above-described process are arranged so that the phosphor layer 11 and the electron-emitting device 5 face each other with the closed-loop frame 15 interposed therebetween. Next, the face plate 2 and the rear plate 1 are bonded to the frame body 15. Next, the high-voltage terminal 14 penetrates the transparent substrate 8 and is electrically connected to the anode electrode 10. Finally, the space surrounded by the face plate 2, the rear plate 1, and the frame 15 is evacuated to a vacuum. In this way, an image display device can be manufactured. In addition, the manufacturing method of the rear plate 1 is not specifically limited.

Examples 1 to 3, Comparative Examples 1 and 2
(Formation of trapping layer)
A 100 mm × 94 mm high strain point glass [PD200 manufactured by Asahi Glass Co., Ltd., strain point 570 ° C., annealing point 620 ° C.] was used as the transparent substrate. This transparent substrate was thoroughly washed, and an acrylic negative photoresist (model number TR2009) manufactured by JSR Co., Ltd. was applied by a spin coating method to obtain a resist film having a film thickness of 1.5 μm after drying (film during application) 8 μm thick, drying temperature 60 ° C., drying time 12 minutes). Next, using a proxy exposure apparatus, 500 mJ / cm ² irradiation (illuminance: 11 mW / cm ² ) of ultra high pressure mercury lamp light was performed in the atmosphere with a distance of 100 μm between the transparent substrate and the mask. Subsequently, a 0.5% aqueous solution of TMAH (tetramethylammonium hydroxide) was sprayed at room temperature (spreading amount: 88.5 L / min, transparent substrate transport speed: 4 m / min). Thereafter, the resist pattern was formed as a trapping layer by rinsing with water so that a plurality of regions having a film thickness of 1.3 μm and 100 × 250 μm existed.

(Surface treatment of acquisition layer)
An excimer UV lamp was installed at a position 5 mm above the transparent substrate on which the trapping layer was formed, and was irradiated with light having a wavelength of 172 nm in an air atmosphere at 1.5 J / cm ² . This treatment reduced the water contact angle on the surface of the trapping layer to 10 °.

(Application of inorganic particle dispersion and formation of inorganic particle deposition layer)
As the inorganic particles, “HI-PRECICA SS (N7N)” which is silica particles having an average particle diameter of 1.7 μmφ manufactured by Ube Nitto Kasei Co., Ltd. is used, and a 40 wt% aqueous dispersion of the silica particles is used as an inorganic particle dispersion. It was. The transparent substrate subjected to the surface treatment of the trapping layer was heated to 70 ° C. on a hot plate, and the inorganic particle dispersion, which is an aqueous dispersion of the silica particles, was sprayed on the entire surface of the transparent substrate with a dropper. Water as the dispersion medium was dried in about 15 minutes, and the entire surface of the transparent substrate was evenly covered with the deposited layer of silica particles.

(Capturing inorganic particles in the trapping layer and removing excess inorganic particles)
Subsequently, the transparent substrate is again held on a hot plate at 230 ° C. for 20 minutes, the silica particles in the lowermost layer of the silica particle deposition layer are embedded in the trapping layer, and the transparent substrate is returned to room temperature. Excess silica particles were removed by treatment for ~ 5 minutes. When the cross section of the transparent substrate is observed with an SEM in this state, the silica particles are held in a state where the trapping layer is submerged by about 500 nm, and the silica particles are based on a six-layer closest packing arrangement only on the trapping layer. The result is an ordered arrangement.

  The embedding depth of the silica particles in the trapping layer depends on the thermoplastic properties of the trapping layer and can be adjusted by the heating temperature and time. Specifically, the embedding is performed by varying the heating temperature and time of the transparent substrate, the embedding depth is measured by observing the cross section of the sample, and the particles after the second layer are trapped and dropped off when excess particles are removed. The depth of embedding that was difficult to occur was determined. As a result, if about ¼ to ３ of the diameter of the particle is embedded, it is confirmed that it is difficult to capture the second layer and subsequent particles and to drop off when removing excess silica particles. It was done. The amount of silica particles sinking into the trapping layer was determined based on this.

(Removal of trapping layer)
Subsequently, the transparent substrate from which excess silica particles have been removed is heated at a rate of 5 ° C./min in a baking furnace (Super High Temp Oven manufactured by Tabai Espec), and the maximum temperature is 450 ° C., 500 ° C., 560 ° C., 580 ° C. Five types of samples at 600 ° C. were prepared. The holding time at the maximum temperature was 90 minutes.

(Embedded with inorganic binder)
Subsequently, the silica particles adhering to the transparent substrate after firing were embedded with an inorganic binder. Using an aqueous solution of peroxotitanic acid [“PTA-170” manufactured by Kon Corporation], a film of about 1.3 μm is repeatedly applied by spin coating to about 200 nm on a transparent substrate and dried at 200 ° C. on a hot plate. Formed. Thereafter, a single baking was performed at 580 ° C. to refill the silica particles. The refractive index of the titanium oxide film after baking at 580 ° C. was 2.1.

(Evaluation of light extraction effect)
As described above, as shown in FIG. 3A, a transparent substrate 8 is obtained in which a plurality of light extraction structures 9 are patterned in a 100 × 250 μm area, and the light extraction efficiency is directly compared. In order to evaluate, this transparent substrate 8 was cut into a 10 mm square size. In FIG. 3A, reference numeral 31 denotes a region where the light extraction structure is not formed. Then, an IPA solution containing ethyl cellulose and phosphor particles was spin-coated and dried to form a phosphor-containing ethyl cellulose film as the phosphor layer 11 on the transparent substrate 8. After the formation of the phosphor layer 11, the phosphor was excited with UV (254 nm wavelength) in the configuration as shown in FIG. In FIG. 3B, 32 is a handy UV lamp “SLUV-6” manufactured by AS ONE Co., Ltd., which excites and emits a phosphor formed on the transparent substrate 8 with UV light having a wavelength of 254 nm. 33 is a spectroradiometer “SR-UL1” manufactured by Topcon Technohouse Co., Ltd., and 34 is an attachment lens “AL-11” manufactured by Topcon Technohouse Co., Ltd. By combining the two, the focus was focused on an area of about 70 μmφ, and the luminance was measured for each of the area where the light extraction structure 9 was formed and the area 31 where the light extraction structure 9 was not formed, and the magnification was compared. The results are shown in Table 1. Note that the luminance magnification is a magnification obtained by (luminance of the region where the light extraction structure is formed) / (luminance of the region where the light extraction structure is not formed).

(Evaluation of adhesion state of inorganic particles)
After firing and before embedding with an inorganic binder, a peel test is performed with a protective adhesive film No. 702 [manufactured by Nichiban Co., Ltd., adhesive strength: 0.4 N / 10 mm], and the peeled state of the silica particles is observed, and no peel is observed. Was good. In addition, when peeling does not occur in this evaluation method, it has been found that the silica particles do not peel even if the conditions of spin coating for subsequent application of the precursor solution of the inorganic binder fluctuate. Further, even when peeling occurs by this evaluation method, if a coating method that does not apply shear to the silica particles and the transparent substrate, such as a die coater, the peeling hardly occurs. In general, it has also been found that if the adhesion after firing is about 0.1 N / 10 mm or more, particles will not be peeled off by the embedding process.

  High strain point glass used as a transparent substrate [“PD200” manufactured by Asahi Glass Co., Ltd.] has a strain point of 570 ° C. and good light with good adhesion of inorganic particles even when baked at 560 ° C. which is 10 ° lower than that. It can be seen that an extraction structure is obtained. However, when the firing temperature is 70 ° or more lower than the strain point, some of the inorganic particles are peeled off, resulting in a light extraction structure with many defects with low luminance magnification.

Example 4
When ordinary SL glass (strain point 511 ° C., annealing point 554 ° C.) was used as the transparent substrate and the formation from the trapping layer to firing was performed in the same manner as in Example 1, the beads were hardly peeled even at a firing temperature of 500 ° C. Thus, it was confirmed that good luminance magnification and good adhesion of inorganic particles can be obtained.

Comparative Example 3
Example 1 except that the transparent substrate similar to Example 1 and the transparent substrate similar to Example 4 were used, and the firing temperature was set to a temperature exceeding the annealing point of each transparent substrate from the formation of the capture layer to the firing. The same was done. As a result, irregular distortion occurred in the transparent substrate after firing, and it was confirmed that it was not suitable for manufacturing a large display.

Example 5
Titanium oxide particles [“JR-1000” manufactured by Teika Co., Ltd.] were used as the inorganic particles, and polysilazane dibutyl ether solution [“Aquamica NN120-20” manufactured by AZ Electronic Materials Co., Ltd.] was used as the inorganic binder. In other steps, a light extraction structure pattern was formed in the same manner as in Example 2, and the luminance magnification was evaluated. The results are shown in Table 2.

Examples 6-8, Comparative Example 4
Bi-type glass frit (softening point 450 ° C.) was added in an amount of 0.01 wt% to 1 wt% to the acrylic negative photoresist (model number TR2009) manufactured by JSR Corporation used in Example 1. Moreover, except having set baking temperature to 500 degreeC, it was set as the conditions similar to the above-mentioned Example 5, and the adhesion body of an inorganic particle and the brightness | luminance magnification were calculated | required. The results are shown in Table 3. As shown in Table 3, in all cases, a luminance magnification of 1.4 times or more was obtained, but in order to improve the adhesion of inorganic particles, the addition amount of frit was 0.1% by weight or more. It can be seen that it is preferable.

  1: rear plate, 2: face plate, 3: scanning wiring, 4: modulation wiring, 5: electron-emitting device, 6: electron source substrate, 7: back substrate, 8: transparent substrate, 9: light extraction structure, 10: Anode electrode, 11: phosphor layer, 12: inorganic particles, 13: inorganic binder, 14: high-voltage terminal, 15: frame, 21: trapping layer, 22: dispersion medium

Claims (11)

Forming a capture layer on a transparent substrate;
Providing an inorganic particle dispersion liquid in which inorganic particles are dispersed in a dispersion medium on the trapping layer, volatilizing the dispersion medium, and forming a deposition layer of the particles on the trapping layer;
Embedding and trapping inorganic particles in the bottom layer of the deposited layer in the trapping layer;
Removing inorganic particles not captured by the capturing layer, and forming an inorganic particle layer in which the inorganic particles captured by the capturing layer are disposed in the capturing layer;
Heating the transparent substrate having the inorganic particle layer, removing the capture layer and bonding the inorganic particles constituting the inorganic particle layer to the transparent substrate;
And a step of embedding the inorganic particles adhered to the transparent substrate with an inorganic binder having a refractive index different from that of the inorganic particles.   The trapping layer contains a polymer compound, and the step of trapping the trapping layer by embedding the inorganic particles in the lowermost layer of the deposited layer in the trapping layer is performed at a glass transition point or a melting point of the polymer compound or higher. The method for forming a light extraction structure according to claim 1, wherein the light extraction structure is formed by heating.   The transparent substrate is made of glass, and the inorganic particles are a material having a glass transition point or a melting point higher than the glass transition point of the transparent substrate, and the inorganic particles constituting the inorganic particle layer are removed while the trapping layer is removed. 3. The method for forming a light extraction structure according to claim 1, wherein the step of adhering to the transparent substrate is performed by baking at a temperature not higher than the annealing point of the transparent substrate.   The method for forming a light extraction structure according to claim 3, wherein the baking of the transparent substrate is performed at a temperature of a strain point of the transparent substrate of -20 ° C or higher.   The method for forming a light extraction structure according to any one of claims 1 to 3, wherein the trapping layer contains 0.1 to 5% by weight of frit glass.   6. The method for forming a light extraction structure according to claim 5, wherein the baking of the transparent substrate is performed at a temperature equal to or higher than a softening point of the frit glass.   The inorganic particles are trapped in the trapping layer by embedding ¼ to ３ of the particle diameter of each inorganic particle in the trapping layer. The method for forming the light extraction structure according to item.   8. A method for manufacturing a light emitting substrate having a light extraction structure for extracting light generated from a light emitting layer, wherein the light extraction structure is formed by the method for forming a light extraction structure according to claim 1. A method for manufacturing a light-emitting substrate.   The light extraction structure according to any one of claims 1 to 7, wherein the light extraction structure is a method for manufacturing an image display device having a light extraction structure for extracting light generated from a light emitting layer that displays an image by light emission. A method for manufacturing an image display device, characterized in that the image display device is formed by a structure forming method.   The method of manufacturing an image display device according to claim 9, wherein the image display device is a field emission display.   The method for manufacturing an image display device according to claim 9, wherein the image display device is an electroluminescence display.

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