Transparent composite substrate, preparation method thereof and touch panel

A transparent composite substrate includes a first transparent substrate, a second transparent substrate, and a binding layer bonding the first transparent substrate and the second transparent substrate with a bond therebetween.

BACKGROUND OF THE INVENTION

This application claims priority to Chinese Application Serial Number 201410562579.0, filed Oct. 21, 2014, which is herein incorporated by reference.

FIELD OF THE INVENTION

The present disclosure relates to transparent composite substrates. More particularly, the present disclosure relates to transparent composite substrates having a binding layer, preparation methods thereof, and applications thereof to touch panels.

DESCRIPTION OF RELATED ART

Sapphire substrates have excellent abrasion and scratch resistance, and Moh's hardness of sapphire substrates is about 9, which is only below that of diamond. Also, sapphire substrates have larger surface tension due to high compactness. The two characteristics mentioned above make sapphire substrates suitable for the preparation of touch panels of electronic devices. Although applications of sapphire substrates are gaining popularity, costs associated with sapphire substrates are much higher and make it difficult to achieve wide application and promotion. In addition, although sapphire substrates have higher hardness, sapphire substrates also have low compression resistance, high brittleness and low impact resistance, which limit application of sapphire substrates.

Common composite substrates are formed by a composite of sapphire substrates and glass substrates to take advantage of the abrasion and scratch resistance of sapphire substrates, while using glass substrates to further increase the compression and impact resistance of the composite substrate. Generally, an adhesive is used to bond a sapphire substrate to a glass substrate. However, the adhesive has poor transparency and adhesion, and may lose the adhesive property at high temperature and pressure. The adhesive further increases thickness of the composite substrate.

SUMMARY OF THE INVENTION

The present disclosure provides a transparent composite substrate using a binding layer to achieve a composite of the glass substrate and the sapphire substrate without using any adhesives.

The present disclosure provides a transparent composite substrate. The transparent composite substrate includes a first transparent substrate, a second transparent substrate, and a binding layer bonding the first transparent substrate and the second transparent substrate with a bond therebetween.

In one or some embodiments of the present disclosure, the binding layer includes silicon-oxygen-silicon bonds, aluminum-oxygen-silicon bonds or aluminum-oxygen-aluminum bonds.

In one or some embodiments of the present disclosure, the first transparent substrate and the second transparent substrate are independently selected from a glass substrate or a sapphire substrate.

In one or some embodiments of the present disclosure, the first transparent substrate is the sapphire substrate, and the second transparent substrate is the glass substrate.

In one or some embodiments of the present disclosure, an inorganic material layer is disposed between the binding layer and the sapphire substrate, and the binding layer has silicon-oxygen-silicon bonds.

In one or some embodiments of the present disclosure, the inorganic material layer is a silicon layer or a silicon dioxide layer.

In one or some embodiments of the present disclosure, the inorganic material layer has a thickness in a range from about 1 μm to about 10 μm.

In one or some embodiments of the present disclosure, the sapphire substrate has a thickness in a range from about 0.1 mm to about 0.3 mm, and the glass substrate has a thickness in a range from about 0.2 mm to about 1 mm.

The present disclosure provides a method of manufacturing a transparent composite substrate. The method includes following steps. A first transparent substrate and a second transparent substrate are provided, and surfaces of the first transparent substrate and the second transparent substrate are activated to adsorb a hydroxyl group thereon. The activated surfaces of the first transparent substrate and the second transparent substrate are overlapped to form a contact surface therebetween, and the first transparent substrate and the second transparent substrate are annealed to form a binding layer at the contact surface.

In one or some embodiments of the present disclosure, the surfaces of the first transparent substrate and the second transparent substrate are activated by a plasma gas comprising nitrogen gas, argon gas, neon gas, or combination thereof.

In various embodiments of the present disclosure, the first transparent substrate and the second transparent substrate are annealed between 0° C. and 1000° C.

The present disclosure provides a method of manufacturing a transparent composite substrate. The method includes following steps. A sapphire substrate and a glass substrate are provided, and an inorganic material layer is formed at a bottom surface of the sapphire substrate. Then, the sapphire substrate and the glass substrate are stacked to form a contact surface between the inorganic material layer and the glass substrate, and an electrical field is applied to the sapphire substrate and the glass substrate, which the sapphire substrate is connected to an anode of the electrical field, and the glass substrate is connected to an cathode of the electrical field. The sapphire substrate and the glass substrate are heated to form a binding layer at the contact surface.

In one or some embodiments of the present disclosure, the inorganic material layer is a silicon layer or a silicon dioxide layer.

In one or some embodiments of the present disclosure, the electrical field has a voltage in a range from about 300 V to about 800 V, and a heating temperature is in a range from about 200° C. to about 400° C.

The present disclosure provides a touch panel. The touch panel includes a transparent composite substrate and a touch sensing device. The transparent composite substrate acts as a cover plate of the touch panel, which the transparent composite substrate includes a first transparent substrate, a second transparent substrate, and a binding layer bonding the first transparent substrate and the second transparent substrate with a bond therebetween. The touch sensing device is disposed at the second transparent substrate, which the touch sensing device and the binding layer are at two opposite sides of the second transparent substrate respectively.

In one or some embodiments of the present disclosure, the first transparent substrate is a sapphire substrate, and the second transparent substrate is a glass substrate.

In one or some embodiments of the present disclosure, an anti-reflective film is disposed at the first transparent substrate, which the anti-reflective film and the binding layer are at two opposite sides of the first transparent substrate respectively.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1illustrates a cross-sectional view of a transparent composite substrate100according to various embodiments of the present disclosure. As shown inFIG. 1, the transparent composite substrate100includes a glass substrate110, a sapphire substrate120, and a binding layer130disposed between the glass substrate110and the sapphire substrate120to bond the glass substrate110and the sapphire substrate120. The bonding means that a bond is formed between the glass substrate110and the sapphire substrate120, so as to achieve a stable and strong composite of the glass substrate110and the sapphire substrate120.

Specifically, the glass substrate110includes an upper surface112and a lower surface114, and the sapphire substrate120also includes an upper surface122and a lower surface124. The glass substrate110is formed of silicon dioxide with some sodium ions, potassium ions, and calcium ions therein, and the sapphire substrate120is formed of aluminum oxide.

During the bonding process, a surface treatment is performed on the surfaces predetermined for bonding. In some embodiments, the surface treatment is performed to the lower surface124of the sapphire substrate120and the upper surface112of the glass substrate110, to make the lower surface124and the upper surface112hydrophilic and have valence bonds. Specifically, the hydrophilic lower surface124of the sapphire substrate120and the hydrophilic upper surface112of the glass substrate110adsorb hydroxyl groups, which react with silicon in the glass substrate110to form silanol bonds (Si—OH). Similarly, the hydroxyl groups also react with aluminum in the sapphire substrate120to form aluminum alcohol bonds (Al—OH).

The lower surface124of the sapphire substrate120and the upper surface112of the glass substrate110are overlapped to form a contact surface therebetween. Then, an annealing process is performed on the sapphire substrate120and the glass substrate110to polymerize silanol bonds and aluminium alcohol bonds at high temperature, and the binding layer130is formed with aluminum-oxygen-silicon bonds (Al—O—Si) therein to achieve stable composite of the sapphire substrate120and the glass substrate110. A thickness of the binding layer130is very thin, which is less than or equal to about 10 nm.

In some embodiments, the sapphire substrate120has a thickness in a range from about 0.1 mm to about 0.3 mm, and the glass substrate110has a thickness in a range from about 0.2 mm to about 1 mm. The glass substrate110may be, for example, a substrate through chemical strengthening, which has better strength to improve the sapphire substrate120with thinner thickness and lower compression resistance.

FIG. 2illustrates a cross-sectional view of a transparent composite substrate200according to various embodiments of the present disclosure. As shown inFIG. 2, the transparent composite substrate200includes a first glass substrate210, a second glass substrate220, and a binding layer230disposed between the first glass substrate210and the second glass substrate220, so as to bond the first glass substrate210and the second glass substrate220. In some embodiments, the binding layer230includes silicon-oxygen-silicon bonds (Si—O—Si).

FIG. 3illustrates a cross-sectional view of a transparent composite substrate according to various embodiments of the present disclosure. As shown inFIG. 3, a transparent composite substrate300includes a first sapphire substrate310, a second sapphire substrate320, and a binding layer330disposed between the first sapphire substrate310and the second sapphire substrate320, so as to bond the first sapphire substrate310and the second sapphire substrate320. In some embodiments, the binding layer330includes aluminum-oxygen-aluminum bonds (Al—O—Al).

As described with regard to the above embodiments, the binding layer130is formed between the sapphire substrate120and the glass substrate110, so as to achieve the composite of the two by bonding without using any adhesives, but not limited thereto. Similarly, the binding layer230or330is formed between two glass substrate210and220or between two sapphire substrate310and320to achieve stable bonding therebetween. In addition, in various embodiments, the binding layer130can be used to achieve stable bonding between a plurality of substrates. For example, a transparent composite substrate is a multi-layer composite substrate including, from top to bottom, the glass substrate110, the binding layer130, the sapphire substrate120, another binding layer130and another glass substrate110in that sequence to increase the strength of a touch panel.

FIG. 4illustrates a cross-sectional view of a transparent composite substrate according to various embodiments of the present disclosure.FIG. 4andFIG. 1use the same reference numerals to represent the same or like elements, and the description of the same portions is omitted. Description of the omitted portions can be found above, and the details are not repeated hereinafter.

As shown inFIG. 4, a transparent composite substrate400includes the glass substrate110, the sapphire substrate120, and a binding layer430disposed between the glass substrate110and the sapphire substrate120, so as to bond the glass substrate110and the sapphire substrate120. In addition, the transparent composite substrate400further includes an inorganic material layer410disposed between the binding layer430and the sapphire substrate120. The inorganic material layer410is a silicon layer or a silicon dioxide layer to achieve higher bonding strength between the glass substrate110and the sapphire substrate120.

The transparent composite substrate400is formed by an electrochemical reaction process using an external electric field. For example, the upper surface122of the sapphire substrate120is connected to an anode of the external electric field, and the lower surface112of the glass substrate110is connected to a cathode of the external electric field. Alkali metal ions in the glass substrate110, such as sodium, potassium and calcium ions, migrate toward the cathode and aggregate at the lower surface114of the glass substrate110. Therefore, a depletion region having negative charges is formed at the upper surface112of the glass substrate110adjacent to the inorganic material layer410. A huge electrostatic attraction force is formed between the depletion region having negative charges and the inorganic material layer410having positive charges to make the glass substrate110bond to the sapphire substrate120via the inorganic material layer410. In addition, oxygen ions remain at the upper surface112of the glass substrate110due to the migration of the alkali metal ions. At high temperature, these oxygen ions further react with silicon inside the inorganic material layer410to form stable silicon-oxygen-silicon bonds (Si—O—Si) in the binding layer430. The binding layer430should include sufficient silicon-oxygen-silicon bonds to achieve stable and solid bonding.

In some embodiments, the inorganic material layer410is a silicon layer having a thickness in a range from about 1 μm to about 10 μm. In various embodiments, the inorganic material layer410is a silicon dioxide layer having a thickness in a range from about 1 μm to about 10 μm.

FIG. 5is a flow chart illustrating a method of manufacturing a transparent composite substrate, according to various embodiments of the present disclosure. The method starts with step510, in which a first transparent substrate and a second transparent substrate are provided. In some embodiments, the first transparent substrate is the glass substrate110, and the second transparent substrate is the sapphire substrate120to manufacture the transparent composite substrate100shown inFIG. 1. In various embodiments, the first transparent substrate and the second transparent substrate are the glass substrate210and220to manufacture the transparent composite substrate200shown inFIG. 2. In various embodiments, the first transparent substrate and the second transparent substrate are the sapphire substrates310and320to manufacture the transparent composite substrate300shown inFIG. 3.

Continuing in step520, the surfaces of the first transparent substrate and the second transparent substrate are cleaned. Because the cleanness of the bonding surfaces will influence the bonding strength, dust and particles on the surfaces of the first transparent substrate and the second transparent substrate are cleaned away with water, alcohol, acetone, or a combination thereof before bonding. In addition, the flatness of the bonding surfaces also influences the bonding strength. The surfaces of the first transparent substrate and the second transparent substrate are polished before cleaning, so as to obtain flat and smooth surfaces.

Referring to step530, the surfaces of the first transparent substrate and the second transparent substrate are activated to adsorb a hydroxyl group thereon. A plasma gas, such as nitrogen gas, argon gas, and neon gas, generates ions or neutral atoms at high temperature and high energy, and these ions or neutral atoms physically impact the surfaces of first transparent substrate and the second transparent substrate. Therefore, the surfaces predetermined for bonding adsorb the hydroxyl groups thereon. As illustrated inFIG. 1, some unstable oxygen atoms are on the surfaces or in vivo of the glass substrate110and the sapphire substrate120. Under certain conditions, these unstable oxygen atoms are activated to leave silicon atoms and aluminum atoms, and dangling bonds are formed at the surfaces. InFIG. 1, the upper surface112of the glass substrate110and the bottom surface124of the sapphire substrate120are activated by the plasma gas to form hydrophilic lower surface124and hydrophilic upper surface112. The hydrophilic lower surface124of the sapphire substrate120and the hydrophilic upper surface112of the glass substrate110are able to adsorb hydroxyl groups, so as to form the silanol bonds (Si—OH) and the aluminium alcohol bonds (Al—OH). In some embodiments, the plasma gas is a low-temperature plasma gas. In various embodiments, the plasma gas is in a vacuum environment to increase efficiency of the process.

Continuing in step540, the activated surfaces of the first transparent substrate and the second transparent substrate are overlapped, and a contact surface is formed between the first transparent substrate and the second transparent substrate. Referring toFIG. 1at the same time, the activated upper surface112of the glass substrate110and the activated lower surface124of the sapphire substrate120are stacked to form the contact surface between the glass substrate110and the sapphire substrate120. Because the upper surface112and the lower surface124are hydrophilic, water molecules can be easily adsorbed thereon, and a hydrogen bonding bridge is formed at the contact surface to attract the upper surface112and the lower surface124. The bonding strength of the hydrogen bonding bridge is stronger than a van der Waals force between atoms, so an initial bonding is much easier to be achieved.

Continuing in step550, the first transparent substrate and the second transparent substrate are annealed to form a binding layer at the contact surface. After initial bonding, the glass substrate110and the sapphire substrate120are heated in an atmosphere furnace to perform an annealing process. During the annealing process, the hydrogen bonds between the upper surface112and the lower surface124disappear, and oxygen bonds (—O—O— or —O—) are formed to shorten the space between the atoms at the contact surface. At the same time, the silanol bonds at the upper surface112of the glass substrate110are polymerized with the aluminum alcohol bonds at the lower surface124of the sapphire substrate120, and the binding layer130having silicon-oxygen-aluminum bonds is formed at the contact surface to achieve stable composite of the glass substrate110and the sapphire substrate120.

It is worth noting that the flow chart shown inFIG. 5is not limited to manufacture of the transparent composite substrates shown inFIG. 1toFIG. 3, but could be also used to manufacture the transparent composite substrate shown inFIG. 4. For example, the inorganic material layer410is coated on the lower surface124of the sapphire substrate120, and steps of cleaning, activating, stacking and annealing are performed to form the binding layer430between the sapphire substrate120and the glass substrate110. In some embodiments, the binding layer430includes silicon-oxygen-silicon bonds (Si—O—Si) to achieve a stable composite of the glass substrate110and the sapphire substrate120.

FIG. 6is a flow chart illustrating a method of manufacturing a transparent composite substrate according to various embodiments of the present disclosure. Please refer toFIG. 6and the transparent composite substrate400shown inFIG. 4at the same time. The method starts with step610, in which a sapphire substrate120and a glass substrate110are provided to manufacture the transparent composite substrate400shown inFIG. 4.

Continuing in step620, the surfaces of the sapphire substrate120and the glass substrate110are cleaned. Because the cleanness of the bonding surfaces will influence the bonding strength, dusts and particles on the surfaces of the sapphire substrate120and the glass substrate110are cleaned away with water, alcohol, acetone, or combination thereof before bonding. In addition, the flatness of the bonding surfaces also influences the bonding strength. The surfaces of the sapphire substrate120and the glass substrate110are polished before cleaning, so as to obtain flat and smooth surfaces.

Referring to step630, an inorganic material layer410is formed at the lower surface124of the sapphire substrate120. The inorganic material layer410is a silicon layer or a silicon dioxide layer. As shown inFIG. 4, the inorganic material layer410is formed at the lower surface124of the sapphire substrate120and in contact with the sapphire substrate120. In some embodiments, the inorganic material layer410is formed by coating. In some embodiments, the inorganic material layer410is a silicon layer having a thickness in a range from about 1 μm to about 10 μm. In various embodiments, the inorganic material layer410is a silicon dioxide layer having a thickness in a range from about 1 μm to about 10 μm.

Continuing in step640, the sapphire substrate120and the glass substrate110are stacked, and a contact surface is formed between the glass substrate110and the inorganic material layer410. Referring toFIG. 4at the same time, the glass substrate110is stacked with the sapphire substrate120having the inorganic material layer410at the lower surface124to form the contact surface between the inorganic material layer410and the glass substrate110.

Continuing in step650, an electrical field is applied to the sapphire substrate120and the glass substrate110. The sapphire substrate120is connected to an anode of the electrical field, and the glass substrate110is connected to a cathode of the electrical field. After stacking, the glass substrate110and the sapphire substrate120are placed in a bonding machine for bonding. The bonding machine generates the electrical field applied to the sapphire substrate120and the glass substrate110. The top surface122of the sapphire substrate120is connected to the anode of the electrical field, and the bottom surface114of the sapphire substrate120is connected to a cathode of the electrical field. While applying the electrical field, a huge current pulse is generated. When the current pulse is gradually decreased to zero, the bonding process is completed. In some embodiments, the electrical field has a voltage in a range from about 300 V to about 800 V.

Ions in the glass substrate110migrate due to the electrical field. Specifically, the alkali metal ions in the glass substrate, such as sodium, potassium and calcium ions, migrate toward the cathode and aggregate at the bottom surface114of the glass substrate110. Therefore, the depletion region having negative charges is formed at the top surface112of the glass substrate110adjacent to the inorganic material layer410. A huge electrostatic attraction force is formed between the depletion region and the inorganic material layer410having positive charges to make the glass substrate110bond stably to the sapphire substrate120.

Continuing in step660, the sapphire substrate120and the glass substrate110are heated to form the binding layer430at the contact surface. The bonding process is performed at high temperature, about 200° C. to 400° C., to assist the electrostatic attraction force, and the bonding strength is further increased. In addition, oxygen ions remain at the top surface112of the glass substrate110due to the migration of the alkali metal ions. These oxygen ions react with silicon inside the inorganic material layer410at high temperature to form stable silicon-oxygen-silicon bonds (Si—O—Si) in the binding layer430to achieve a stable composite of the glass substrate110and the sapphire substrate120.

The transparent composite substrate in the present disclosure can act as a cover plate of a touch panel. Please refer toFIGS. 7A and 7Bfor further clarification of the present disclosure.FIG. 7Aillustrates a three-dimensional diagram of a touch panel according to various embodiments of the present disclosure, andFIG. 7Billustrates a cross-sectional view of a portion of the touch panel inFIG. 7Aalong line A-A, according to various embodiments of the present disclosure. As shown inFIG. 7A, a touch panel1000includes a touch region1100and a non-touch region1200surrounding the touch region1100. The touch region1100is a display area of the touch panel1000, and the non-touch region1200is a non-viewing area of the touch panel1000. Generally, a frame is formed by a light-shielding layer to cover the non-touch region1200. InFIG. 7B, the touch panel1000includes a cover plate1120, which is the transparent composite substrate described above. The cover plate1120includes a first transparent substrate1122, a second transparent substrate1124, and a binding layer1126bonding the first transparent substrate1122and the second transparent substrate1124with a bond therebetween.

To increase transmittance of the touch panel1000, an anti-reflective film1140is disposed on the first transparent substrate1122. The anti-reflective film1140and the binding layer1126are respectively at two opposite sides of the first transparent substrate1122to increase the transmittance. The anti-reflective film1140may be a single-layer or multi-layer transparent film having functionality of anti-reflective or anti-glare. On the other hand, a touch sensing device1160is disposed at the second transparent substrate1124, which the touch sensing device1160and the binding layer1126are respectively at two opposite sides of the second transparent substrate1124.

The touch sensing device1160includes a sensing electrode layer1162and a wire layer1164. The sensing electrode layer1162is disposed in the touch region1100, and the wire layer1164is disposed in the non-touch region1200, which the sensing electrode layer1162is extended to the non-touch region1200to electrically connect the wire layer1164. The sensing electrode layer1162is formed of transparent conductive material, such as indium tin oxide (ITO), indium zinc oxide (IZO), cadmium tin oxide (CTO), aluminum zinc oxide (AZO), indium tin zinc oxide (ITZO), graphene, Ag nanowire, or carbon nanotubes (CNT), but not limited thereto. The wire layer1164is formed of transparent conductive material the same as the sensing electrode layer1162, or opaque conductive material, such as Ag, Cu, Mo, Al, and other suitable metals and alloys. The sensing electrode layer1162and the wire layer1164may be formed on the second transparent substrate1124by printing and laser etching, or sputtering and photolithography etching. The sensing electrode layer1162generates signals when sensing touching, and the wire layer1164transfers the signals to a processor to calculate the location of touching. In addition, the sensing electrode layer1162is not limited to be directly formed at the second transparent substrate1124. In various embodiments, the sensing electrode layer1162is adhered to the second transparent substrate1124by adhesive material.

The touch panel1000further includes a light-shielding layer1180disposed on the second transparent substrate1124, which the light-shielding layer1180and the and the binding layer1126are respectively at two opposite sides of the second transparent substrate1124. The light-shielding layer1180is disposed in the non-touch region1200and between the second transparent substrate1124and the wire layer1164, so as to shield the wire layer1164and other opaque devices in the non-touch region1200. The light-shielding layer1180is formed of opaque materials, such as ink and photoresist, which the ink is formed on the second transparent substrate1124by printing, and the photoresist is formed on the second transparent substrate1124by photolithography etching.

In some embodiments, the first transparent substrate1122is the sapphire substrate, and the second transparent substrate1124is the glass substrate. It is worth noting that the sapphire substrate acts as a touching surface to make the touch panel1000have the scratch resistance of the sapphire substrate and the strength of the glass substrate. Specifically, users operate programs and give instructions by touching the sapphire substrate. In some embodiments, the sapphire is directly bonded to the glass substrate to form the binding layer1126having silicon-oxygen-aluminum bonds at the contact surface. In various embodiments, the inorganic material layer is coated on the sapphire substrate, and then the sapphire substrate is bonded to the glass substrate to form the binding layer1126having silicon-oxygen-silicon bonds between the glass substrate and the inorganic material layer.

The embodiments of the present disclosure discussed above have advantages over existing structures and methods, and the advantages are summarized below. The transparent composite substrate is formed by the composite of the sapphire substrate and the glass substrate to significantly reduce the costs of the sapphire substrate. Also, the glass substrate increases the compression resistance of the sapphire substrate to overcome the sapphire substrate's drawback of being brittle. Most importantly, the glass substrate and the sapphire substrate are bonded via the binding layer without any adhesives, so the thinner transparent composite substrate could be formed with excellent transparency. In addition, the bonding strength between the glass substrate and the sapphire substrate is strong enough to maintain stable and solid bonding at high temperature and pressure, and thereby being widely applied to the touch device.

Although the present invention has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein. Reference will now be made in detail to the embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.