This invention relates to a trans-reflective liquid crystal display and the manufacturing method thereof, and more especially, to a reflective film with multi-layer in a trans-reflective liquid crystal display and its manufacturing method.
A trans-reflective liquid crystal display (LCD) utilizes the incident light from front panel, and the light from a backlight module as its light source. In manufacturing, a reflective film is deposited on the partial substrate to reflect the incident light which is to provide a portion of light source for the LCD panel. Therefore, the other portion of light source is from the backlight module for the LCD panel.
After that, a transparent conductive film, such as a pixel electrode 400, is formed in the transmissive area. An organic insulating layer 500 is formed on the reflective area, and a reflective layer 600 is on the organic insulating layer 500. For the improvement in adhesion, an adhesive layer 410 is formed among the organic insulating layer 500, the passivation layer 300 and the transparent conductive film. Then, the organic insulating layer 500, a liquid crystal layer 700 and a color filter (CF) substrate 800 are stacked on sequentially to complete the LCD. As the result, the transparent conductive film is electrically connected to the TFTs by contact holes (CH).
For equaling the distance on the light paths of the incident light from front panel and the transmissive light from backlight module, the organic insulating layer 500 is formed to achieve the cell gap (d) in the reflective area is half of cell gap (2d) in the transmissive area. The ratio of the structures in
The ratio of the structures in
As the foregoing discussion, there are three subjects in manufacturing a trans-reflective LCD: (1) to increase the utility ratio of the light, (2) to simplify the manufacturing process, and (3) to enhance the adhesive strength of the reflective layer.
For solving the problems mentioned above, an object of this invention is to provide a more efficient reflective film to increase the utility ratio of the light.
One object of this invention is to provide a more adhesive reflective film to enhance the adhesion, and to solve the peeling issue.
One object of this invention is to provide an integrated manufacturing process without depositing a metallic reflective layer to reduce the expense of a mask.
For achieving the objects mentioned above, an embodiment of this invention implements a trans-reflective liquid crystal display (trans-reflective LCD). The trans-reflective LCD includes a substrate, a plurality of thin film transistors (TFTs) formed on the substrate, a dielectric layer formed on the substrate over the thin transistors. The dielectric layer includes a plurality of contact holes to expose a portion of each TFT. The reflective film with multi-layer includes a plurality of openings and forms on the partial dielectric layer. Some openings expose the contact holes and others form the transmissive area. The rest area without openings will form the reflective area. Pixel electrodes are formed on the reflective film with multi-layer, and each pixel electrode is connected electrically to a TFT by the contact holes. Thus, a TFT array substrate is complete. After that, a liquid crystal layer is formed on the TFT array substrate, and then an opposite substrate, like a color substrate, is disposed on the liquid crystal layer to complete the trans-reflective liquid crystal display panel.
Each reflective film with multi-layer includes at least one unit consisting of a first reflective layer and a second reflective layer which have different refractive indexes, and the unit amount of the reflective film with multi-layer depends on the ratio of the refractive indexes. In general, the first refractive index is larger than the second one. The amount of the layers makes a net reflective index. The more the net reflective index approaches to 1, the higher the utility of the light is.
The material of the reflective film with multi-layer is similar to that of the dielectric layer. In general, the material is SiNy, SiOx, SiOxNy or the combination thereof. When the x and y are different (the ratio of Silicon, Oxygen and Nitrogen is different), the refractive indexes will be different. Therefore, the net reflective index may approach to 1 by modifying the values of x or y and setting the amount of the layers. And, the adhesion between the reflective film with multi-layer and the dielectric layer will be enhanced due to the similar materials. Moreover, the reflective film with multi-layer and the dielectric layer can be integrated into a process.
For achieving the objects mentioned above, a manufacturing method of a trans-reflective liquid crystal display according to an embodiment of this invention is provided. The manufacturing method includes providing a bare TFT array substrate, forming a dielectric layer on the bare TFT array substrate, forming a reflective film with multi-layer on the dielectric layer, forming a photo-resist layer on the reflective film with multi-layer, exposing with a mask and developing. The mask includes a transparent region, a semi-transparent region and an opaque region to transfer a given pattern to the photo-resist layer after developing. The portion corresponding to the transparent region of the mask is removed by etching to expose the devices of the TFT array with contact holes. Next, an ashing step takes off the photo-resistance corresponding to the semi-transparent region of the mask. The another etching step is employed on the reflective film with multi-layer to expose the dielectric layer corresponding to the semi-transparent region of the mask. After the residual photo-resist layer is stripped away to form the pixel electrode, and then the TFT array substrate is complete. Continuously, an assembling process will complete the LCD panel. The first step of the assembling process is to set an opposite substrate, like a color filter substrate and then to inject the liquid crystal into the space between the substrates.
The steps of forming the dielectric layer and forming the reflective film with multi-layer may be merged to a single process when taking similar materials used into consideration. The single process may be the plasma enhanced chemical vapor deposition (PECVD), the physical vapor deposition (PVD) or the evaporation. What is considered in the single process is to form the different refractive indexes of the first and the second reflective layers in each reflective film with multi-layer by modifying temperature, pressure, gas flow or power.
The mask employed in the exposing step includes a full-transparent region, a semi-transparent region and an opaque region. After developing step, on one hand, the photo-resist layer corresponding to the full-transparent region has been removed to expose the reflective film with multi-layer. On the other hand, the photo-resist layer corresponding to the semi-transparent region is partially removed to leave about ⅓ to ½ thickness of the opaque region. The first etching step will form the contact holes corresponding to the full-transparent region of the mask. After the ashing step, the photo-resist layer corresponding to the semi-transparent region is taken off. The second etching step will remove reflective film with the multi-layer corresponding to the semi-transparent region to form the transmissive area. The rest area is the reflective area. When a dry etching is employed, the first etching, ashing and the second etching can be finished in a chamber to avoid repeating the complicated procedures such as vent and vacuum procedures.
As shown above, the steps of etching, ashing and depositing for the reflective film with multi-layer and the dielectric layer can be integrated into one process respectively, and the transmissive area and reflective area can be formed, and the trans-reflective LCD will be complete.
The reflective film with multi-layer 620 and the dielectric layer 300 are made of the similar materials, such as the silicon nitride SiNy, the silicon oxide SiOx, silicon nitro oxide SiOxNy or their combination. When x and y are different (it means the ratio of the Si, O and N be different), the refractive index is different, that is, the first reflective layer 621 and the second reflective layer 622 of the reflective film with multi-layer 620 have different refractive indexes, and it varies according to the formula:
R={[(na/ns)(n2/n1)2N31 1]/[(na/ns)(n2/n1)2N+1]}2, where R is the net reflective index, na is the air refractive index, ns is the dielectric refractive index of the dielectric layer, n2 is the refractive index of the second reflective layer in one unit of the reflective film with multi-layer, n1 is the refractive index of the first reflective layer of the unit of the reflective film with multi-layer, and N is the unit amount of the reflective film with multi-layer.
For better understanding this invention, a simulation is calculated to show relationship of the amount of the layers, the net reflective index and the thickness of the reflective film with multi-layer under the following assumptions, wherein na=1, ns=1.52, n1=1.8, n2=1.6, and the thickness of the first reflective layer=76.39 nanometer(nm) and the thickness of the second reflective layer=85.94 nanometer(nm). This is, the thickness of each unit of the reflective film with multi-layer=0.162 micrometer(μm). The relationship is represented as following table:
As shown in the above table, for a trans-reflective LCD with double cell gaps, it can replace the structure which is made of an organic insulating layer and a reflective layer in prior arts by forming 20-layer reflective film, and for a trans-reflective LCD with single cell gap, it can replace the structure which is made of a reflective layer in prior arts by forming 4-layer reflective film for enhancing the adhesion. Moreover, the net reflective index of the reflective film with multi-layer is almost equal to 1, this is, the whole incident light is almost reflected into liquid crystal, so the utility ratio of the reflective light is very high.
Finally, the assembling process is performed. After assembling a color filter substrate 800 and injecting the liquid crystal to form the liquid crystal layer 700, the trans-reflective LCD is complete, as shown in
Usually, the plasma enhanced chemical vapor deposition (PECVD), the physical vapor deposition (PVD) or the evaporation are employed in the step of forming the dielectric layer 300 as shown in
When the dry etching technique are employed in the etching steps in
Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that other modifications and variation can be made without departing the spirit and scope of the invention as claimed.
Number | Date | Country | Kind |
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95141579 | Nov 2006 | TW | national |