Method for manufacturing field emission substrate

Abstract

A method for manufacturing a field emission substrate is disclosed. The method includes the following steps: providing a substrate having a conductive layer; forming a hydrophobic layer on the conduction layer; patterning the hydrophobic layer; and removing the hydrophobic layer from the surface of the conductive layer so that the formed layer of electron-emitting materials can contact the surface of the conductive layer. The patterned hydrophobic layer can include plural bumps, and the pitches between the neighboring bumps are in a range of 1 μm to 500 μm. By way of the steps illustrated above, the emitting layer on the substrate can be made easily and arranged accurately. Hence, the electrons can be emitted homogeneously.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is a macrocosmic illustration of providing a hydrophilic solution to the surface of a hydrophobic layer in a preferred embodiment of the present invention;

FIG. 1( b) is a microcosmic illustration of providing a hydrophilic solution to the surface of a hydrophobic layer in a preferred embodiment of the present invention;

FIG. 2( a) is a photo taken after formation of an emission layer on the patterned hydrophobic layer by optical microscope showing the lateral side of the substrate;

FIG. 2( b) is a photo taken by optical microscope after singeing of the hydrophobic layer 12, which shows the lateral side of the substrate;

FIG. 2( c) is a photo taken by optical microscope after singeing of the hydrophobic layer 12, which shows the top view of the substrate;

FIG. 3 is the schematic illustration of the test results of field emission by the FED substrate prepared in this example;

FIG. 4( a) is a top view photo of the substrate taken by optic microscope after formation of an emission layer on the surface of patterned hydrophobic layer in a preferred embodiment of the present invention;

FIG. 4( b) is a top view photo of the substrate taken by optic microscope after formation of an emission layer on the surface of patterned hydrophobic layer in a preferred embodiment of the present invention; and

FIGS. 5( a)˜5(h) are schematic illustrations of the flow charts of the method to manufacture the substrate for a triode FED.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Example of Preparation: Preparation of a Hydrophilic Solution Containing Electron Emission Materials

The following examples of preparation used CNT powder, water, and dispersant to prepare the hydrophilic solutions containing electron emission materials for the examples described hereafter. There are two kinds of dispersants used, one is produced by Tego Chemie Service, the serial number of which is LA-D 868; the other is a product of Noveon, the serial number of which is solsperse 27000.

Carbon nanotube powder, water, and dispersant are mixed and rolled to form a hydrophilic solution containing electron emission materials, which serve as a slurry containing electron emission materials. Table 1 illustrates weight percentages of contents of the hydrophilic solutions prepared in Preparation Example 1, Preparation Example 2, and Preparation Example 3.

	TABLE 1
	Carbon Nanotube
	Powder	Water	Dispersant
	Preparation	4%	92%	4% s-27000
	Example 1
	Preparation	2%	89%	10% LA-D 868
	Example 2
	Preparation	1%	74%	25% LA-D 868
	Example 3

Example 1

Described herein is a method for manufacturing a substrate for a field emission display device in a preferred embodiment in the present invention, see FIG. 1(b).

First, a substrate 1 having an ITO conductive layer 11 on its surface is provided. Then a hydrophobic layer 12 is deposited on the conductive layer 11, and the hydrophobic layer 12 is patterned by photolithography. In this example, hydrophobic layer 12 is a dry-film photoresist.

The patterned hydrophobic layer 12 comprises plural bumps. The bumps are arranged in an M×N matrix on the surface of the substrate, wherein each of M and N is an integer greater than zero. The pitches between edges of neighboring bumps are equal, around 50 μm. The height of each bump is about 25 μm, and width of the cross-section area is about 50 μm, so the aspect ratio of the bumps in this example is about 0.5.

Of course, the height, width, and shape of the bumps, the pitches between neighboring bumps, and the patterns arranged via the bumps are not restricted to the conditions set forth by this example; instead, they are adjustable depending on needs.

Subsequently, a hydrophilic solution 13 is treated by spin-coating such that a thin liquid film 14 is left on the hydrophobic layer 12. After evaporation of liquid layer 14, an emission layer is formed on the patterned hydrophobic layer.

See FIG. 2(a), which is a photo taken after formation of an emission layer on the patterned hydrophobic layer by optical microscope showing the lateral side of the substrate. As shown in FIG. 2(a), the hydrophobic layer comprises plural bumps and each bump is covered by a thin black drop. Therefore, the thin black drops are the electron emitters prepared by the present invention. The thin black drops each consist an emission layer.

Finally, the obtained substrate is heated at 450° C., so that the hydrophobic layer 12 on the conductive layer 11 is burned and removed, making the electron emitters on the surface of the bumps directly contact the conductive layer 11, and the substrate for field emission display in this example is obtained.

FIG. 2( b) is a photo taken by optical microscope after burning and removing the hydrophobic layer 12, which shows the lateral side of the substrate. It is known from the photo that the sizes and shapes of electron emitters formed on the substrate and the pattern formed thereof are influenced by the size of the bumps of the hydrophobic layer 12 and the patterns arranged with the bumps.

FIG. 2( c) is a photo taken by optical microscope after burning and removing the hydrophobic layer 12, which shows the top view of the substrate. Because the bumps of the patterned hydrophobic layer in this example are identical in shapes and sizes, and the pitches between the edges of neighboring bumps are equal, it is proved by FIG. 2(c) that the electron emitters arrayed on the surface of the conductive layer are identical in sizes and shapes, and the pitches between the edges of the neighboring electron emitters are equal.

From FIG. 2(c), the electron emitters of the present invention are round-shaped with a diameter about 50 μm, roughly equal to the width of the cross-section of the bumps.

Test Results of Field Emission

The substrate 1 manufactured in this example is cut in test strips that are 1 cm long and 0.5 cm wide and used for tests of diode field emission. FIG. 3 is the schematic illustration of the test results of field emission by the FED substrate prepared in this example. According to the figure, the electron emission source of the substrate prepared in this example is able to emit electrons stably, and the current increases when higher electric field is applied.

Example 2 and Example 3

The procedures and process conditions are the same as set forth in Example 1 except the hydrophilic solutions. Refer to Example 1 for the conditions and procedures.

See FIGS. 4(a) and 4(b). FIG. 4(a) is a top view photo of the substrate taken by optic microscope after formation of an emission layer on the surface of patterned hydrophobic layer in Example 2. In FIG. 4(a), the results show that the diameters of the round electron emitters formed on the surfaces of the bumps are about 21 μm, while in Fig. (b), the diameter of the round electron emitters formed on the surfaces of the bumps are about 15 μm. Thus, the sizes of the electron emitters are affected by concentrations of carbon nanotube in the hydrophilic solution.

Example 4

The procedures and process conditions of Example 4 are the same as set forth in Example 1 except for the hydrophilic solutions. Refer to Example 1 for the conditions and procedures.

In the patterned hydrophobic layer, the pitches between edges of neighboring bumps are equal, wherein the pitches are about 25 μm. Besides, the height of the bumps is about 40 cm, and the width of the cross-section is about 20 μm.

Wherein the hydrophilic solution containing electron emission materials is the one prepared in the Preparation Example 1, and an electron emitter having a width of 20 μm is formed on the surface of each bump. Therefore, a substrate having a plurality of electron emitters arranged in a regular and ordered manner is eventually obtained.

Example 5

FIG. 5 is a schematic illustration of the flow chart of the method to manufacture the substrate for a triode FED.

First, as shown in FIG. 5(a), with the same conditions as set forth in Example 1, an emission layer is formed on the surface of the patterned hydrophobic layer 52. For the patterned hydrophobic layer 52, the method to form thereof, the sizes of the plural bumps comprised by the hydrophobic layer, the pitches between bumps, and the pattern arranged within the bumps are identical to those disclosed in Example 1.

The conductive layer of the example is Mo meta, while substrate 5, hydrophobic layer 52, and the materials of each electron emitter 53 formed on the surface of each bump are the same as the process conditions in Example 1. As shown in FIG. 5(b), the hydrophobic layer is heated and removed by heating at 450° C., so that each electron emitter 53 contacts directly the surface of the conductive layer 51 and functions to emit electrons.

The lower substrate of a conventional field emission display comprises the components of: cathode, gate electrode, an insulation layer interposed between the cathode and the gate electrode, and electron emitters.

Thus, as shown in FIG. 5 (c), when proceeding with the subsequent processes such as manufacture insulating layer 54 and gate electrode layer 55, a patterned hydrophobic layer 52 is coated on electron emitters 53 to protect electron emitters 53.

Then, as shown in FIGS. 5(d) and 5(e), an insulating layer is deposited by screen-printing on the surface of the conductive layer 51, and the hydrophobic layer is singed by heating, such that a substrate structure as FIG. 5(e) is obtained. Subsequently, as shown in FIG. 5(f), the procedures the same as those in FIG. 5(c) are performed to protect the electron emitters 53.

Finally, as shown in FIGS. 5(g) and 5(f), a gate electrode layer 55 is deposited on the surface of the insulating layer 54, and the hydrophobic layer 52 is singed by heating, such that manufacture of substrate 5 for a triode FED in this example is completed.

Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the scope of the invention as hereinafter claimed.

Claims

1. A method for manufacturing a field emission substrate, the steps comprising: (a) providing a substrate having a conductive layer;(b) forming a hydrophobic layer on the conduction layer;(c) patterning the hydrophobic layer;(d) providing a hydrophilic solution having an electron emission material on the surface of the hydrophobic layer so as to form an emission layer on the surface of the hydrophobic layer; and(e) removing the hydrophobic layer from the surface of the conductive layer so that the formed layer of electron-emitting materials can contact the surface of the conductive layer.

2. The method of claim 1, wherein the bumps are arranged in an M×N matrix, and each of M and N is an integer greater than zero.

3. The method of claim 2, wherein the emission layer comprises plural electron emitters, the electron emitters of the emission layer are arranged in an M×N matrix, and each of M and N is an integer greater than zero.

4. The method of claim 1, wherein the pitches between neighboring bumps are 1˜500 μm.

5. The method of claim 4, wherein the pitches between neighboring bumps are 10˜100 μm.

6. The method of claim 1, wherein the aspect ratio of the bumps is 0.1˜3.0.

7. The method of claim 6, wherein the aspect ratio of the bumps is 0.3˜1.2.

8. The method of claim 1, wherein the pitches between the edges of neighboring bumps are equal.

9. The method of claim 1, wherein the patterning of hydrophobic layer in step (c) is performed by photolithography.

10. The method of claim 1, wherein the hydrophilic solutions in step (d) are provided to the surface of the hydrophobic layer by dropping, spin coating, or soaking.

11. The method of claim 1, wherein the hydrophobic layer in step (e) is removed from the conductive layer by heating.

12. The method of claim 11, wherein the temperature of heating is 60° C.˜550° C.

13. The method of claim 1, wherein the hydrophobic layer is a photoresist.

14. The method of claim 13, wherein the photoresist is a dry-film photoresist.

15. The method of claim 1, wherein the hydrophilic solution comprise water or alcohol.

16. The method of claim 15, wherein the hydrophilic solution comprises a dispersant, enabling the electron materials to disperse homogenously in the hydrophilic solution.

17. The method of claim 1, wherein the bumps are of the shapes of cubes, columns, polyhedrons, ellipsoids, triangular columns, irregular shapes, or the combination thereof.

18. The method of claim 1, wherein the electron emission material comprises a carbon-based material, and the carbon-based material is selected from a group consisting of graphite, diamond, diamond-like carbon, carbon nanotubes, carbon 60, and the combination thereof.