Liquid crystal display with built-in touch screen having particles for pressure concentration

The present invention relates to a liquid crystal display (LCD) panel with a built-in touch screen capable of maintaining touch sensitivity at a certain level regardless of touch circumstances, and an LCD having the LCD panel with a built-in touch screen. According to the present invention, there are provided an LCD panel with a built-in touch screen, comprising a first substrate; a second substrate positioned opposite to first substrate; a liquid crystal layer injected between first and second substrates; a sensing unit including a conductive column spacer and a conductive pad spaced apart from conductive column spacer by a predetermined interval to sense a touch point; and a plurality of pressure particles with certain hardness positioned on an outer surface of first substrate. Further, there is provided an LCD having the LCD panel with a built-in touch screen.

REFERENCE TO RELATED APPLICATION

The present application claims the benefit of priority of Korean Patent Application No. 10-2006-0041786 filed on May 10, 2006 in the Korean Intellectual Property Office.

FIELD OF THE INVENTION

The present invention relates to a liquid crystal display panel having a built-in touch screen and a liquid crystal display (LCD) having the same.

DESCRIPTION OF THE RELATED ART

FIG. 1is a schematic sectional view of a conventional LCD panel with a built-in touch screen having a color filter substrate10including a plurality of color filters13, a thin film transistor (TFT) substrate20including a plurality of pixels26, a liquid crystal layer30between color filter substrate10and TFT substrate20, and polarizing plates41and42attached to the outer surfaces of the substrates. A sensing unit which is composed of a conductive column spacer17and a pad27spaced apart from conductive column spacer17by a predetermined interval is formed between the substrates to sense touch points.

The touch screen so configured induces sensing unit to operate by touching an upper substrate, i.e. color filter substrate10. That is, if color filter substrate10is touched, the gap changes between conductive column spacer17and the pad27causing a detectable change in resistance at the touch point. However, in the aforementioned structure, touch sensitivity depends on touch circumstances. That is, the touch sensitivity is high when a relatively rigid bar having a relatively small contact area is used, (case ‘A’), whereas the touch sensitivity is low when a relatively soft tool having a large contact area, e.g. a finger or the like, is used, (case ‘B’).

SUMMARY OF THE INVENTION

The present invention provides a liquid crystal display (LCD) panel with a built-in touch screen having improved touch sensitivity regardless of the characteristics of the contacting instrumentality. According to an aspect of the present invention the touch screen, comprises a first substrate; a second substrate positioned opposite to first substrate; a liquid crystal layer between first and second substrates; a sensing unit including a conductive column spacer and a conductive pad spaced apart from conductive column spacer by a predetermined interval to sense a touch point; and a plurality of pressure particles exhibiting a predetermined degree of hardness positioned on an outer surface of first substrate. The LCD panel of the present invention may further comprise first and second polarizing plates attached respectively to outer surfaces of first and second substrates.

Preferably, first substrate comprises a transparent insulative substrate, a black matrix for blocking light, a plurality of color filters, and a common electrode formed on an entire surface of the plurality of color filters, wherein conductive column spacer is formed on first substrate.

Preferably, conductive column spacer is formed on the black matrix.

Preferably, conductive column spacer is composed of a projection made of an insulative material and a conductive layer formed on the projection.

Preferably, conductive column spacer is composed of a projection made of a conductive material. Preferably, the spacer includes a ball spacer or column spacer; pressure particles is in the form of a ball; the size of pressure particles is 1 to 100 μm. Preferably, the plurality of pressure particles are dropped at positions corresponding to conductive column spacer and conductive pad and are dispersed on the outer surface of first substrate at a predetermined dispersion density.

Preferably, the plurality of pressure particle are dispersed on an adhesive layer of first polarizing plate at a predetermined dispersion density.

The LCD panel may further comprise a controller for receiving a signal from sensing unit to detect a voltage change and to create a coordinate of a touch point; and a driver for receiving the coordinate from the controller to operate a pointer.

According to another aspect of the present invention, there is provided an LCD, comprising an LCD panel with a built-in touch screen including a first substrate, a second substrate positioned opposite to first substrate, a liquid crystal layer injected between first and second substrates, a sensing unit including a conductive column spacer and a conductive pad spaced apart from conductive column spacer by a predetermined interval to sense a touch point, and a plurality of pressure particles with certain hardness positioned on an outer surface of first substrate; and a backlight for providing light to the LCD panel.

DESCRIPTION OF THE INVENTION

An expression that one element such as a layer, film, region or plate is placed on or above the other element indicates not only a case where the element is placed directly on or above the other element but also a case where an additional element is interposed between the two aforementioned elements.

FIG. 2is a schematic sectional view of a liquid crystal display (LCD) panel with a built-in touch screen according to the present invention.

Referring toFIG. 2, the LCD panel with a built-in touch screen comprises a color filter substrate100, a thin film transistor (TFT) substrate200, a sensing unit300, a liquid crystal layer400, a polarizing plate500and a pressure particle600.

Color filter substrate100comprises a transparent insulative substrate110; a black matrix120formed on the transparent insulative substrate110to block light; a plurality of red, green and blue color filters130formed on the transparent insulative substrate110and the black matrix120; and a common electrode140formed on an entire surface of the plurality of color filters130. Further, color filter substrate100includes a conductive column spacer310of sensing unit300.

TFT substrate200comprises a transparent insulative substrate210, a plurality of TFTs (not shown) formed on the transparent insulative substrate210, and a plurality of pixel electrodes290. Further, TFT substrate200includes a conductive pad320of sensing unit300.

Liquid crystal layer400is injected between color filter substrate100and TFT substrate200; first and second polarizing plates510and520are positioned on outer surfaces of color filter substrate100and TFT substrate200, respectively; and a spacer450for maintaining a cell gap of the substrates is positioned between color filter substrate100and TFT substrate200. Although a column spacer is installed in this embodiment, the present invention is not limited thereto. That is, a ball spacer may be installed.

Further, sensing unit300is composed of conductive column spacer310formed on color filter substrate100and conductive pad320formed on TFT substrate200, and conductive column spacer310and conductive pad320are positioned at a position corresponding to each other in a state where they are spaced apart from each other by a predetermined interval. Sensing unit300detects the change in resistance due to the change in gap between conductive column spacer310and conductive pad320to sense touch points. That is, if a user touches a predetermined position, conductive column spacer310corresponding to the touched position is subjected to a force in a downward direction, i.e. in a direction toward conductive pad320, so that conductive column spacer310is brought into contact with conductive pad320. Then, if the user's touch is released, the force applied at the position is removed. Accordingly, conductive column spacer310and conductive pad320are positioned in such a state where they are spaced apart from each other by the predetermined interval. In other words, if a predetermined position is touched, the change in resistance is produced at the position while there occur short and open between conductive column spacer310and conductive pad320. Accordingly, the touched position can be sensed based on the detection of the changed voltage.

Pressure particles600having a predetermined hardness are positioned between color filter substrate100and first polarizing plate510to perform the function of adjusting the pressure range such that the force transmitted through first polarizing plate510positioned at an outermost surface of color filter substrate100can be concentrated on a local region, i.e. a region corresponding to conductive column spacer310. The hardness of pressure particles600is preferably similar to or greater than that of first polarizing plate510or the transparent insulative substrate110.

In addition, pressure particles600may be formed into various shapes. However, they is preferably formed into a ball shape. More preferably, pressure particles600is formed to have a size of 1 to 100 .mu.m and made of a transparent material such as silicate. For example, pressure particles600may be made of a transparent glass bead. In such a case, if the size of pressure particles600is too small, it is difficult to concentrate the touch pressure force on the corresponding column spacer. But, if the size thereof is too large, it may have a bad influence on an image output from the LCD panel. Therefore, it is preferred that pressure particles600be formed to have a size of 1 to 100 .mu.m as described above.

FIG. 3illustrates what happens when a soft tool with a large touch area, e.g. a finger or the like, touches the LCD panel with a built-in touch screen according to the present invention. As described above, pressure particles600are positioned between color filter substrate100and first polarizing plate510. In general, under the circumstances where a touch tool having a small contact area with the LCD panel is used, i.e. in a case where a pen-shaped bar with a small touch area and certain hardness is used, most of the touch pressure is used to change a gap between conductive column spacer310and conductive pad320of sensing unit300. However, in a case where a soft touch tool having a large contact area with the LCD panel, i.e. a finger of the user, is used, most of the touch pressure is not used to change the gap between a conductive spacer and pad but to deform color filter substrate. Therefore, much larger touch pressure is necessary to sufficiently produce the change in gap between conductive column spacer310and conductive pad320.

On the other hand, if the LCD panel with a built-in touch screen according to the present invention, in which pressure particles600are disposed between color filter substrate100and first polarizing plate510, is touched with a user's finger or the like, an application range of touch pressure is concentrated on a local region, i.e. a region of conductive column spacer310, by means of pressure particles600. As a result, even though a soft touch tool having a large contact area with the LCD panel is used to touch the screen, an effect that is substantially the same is achieved as when a hard touch tool having a small contact area with the LCD panel is used.

FIG. 4is a block diagram schematically illustrating functions of a touch screen of the LCD panel according to the present invention.

Referring toFIG. 4, the touch screen comprises a sensing unit300, a controller350and a driver360. As described above, sensing unit300is composed of conductive column spacer310formed on color filter substrate100and conductive pad320formed on TFT substrate200to detect the change in resistance, and thus in voltage, due to the change in gap between conductive column spacer310and conductive pad320.

The controller350receives a signal from sensing unit300to detect the change in voltage and then to create a desired coordinate corresponding to the received signal. The coordinate created by the controller350is transmitted to the driver360, and the driver360receives the coordinate and operates a pointer.

The controller350and the driver360may be mounted to one side of the LCD panel or on a circuit board electrically connected to the LCD panel.

FIG. 5is a schematic plan view of an LCD panel with a built-in touch screen according to the present invention.FIG. 5is also a partial plan view illustrating a color filter substrate100and a TFT substrate200in the LCD panel with a built-in touch screen according to the present invention.

Red, green and blue color filters130are formed on a transparent insulative substrate of color filter substrate100, and a conductive column spacer310is disposed on a region between the respective adjacent color filters, i.e. a region of a black matrix. Although a single conductive column spacer310is installed at each unit pixel in this embodiment, the number and shape of conductive column spacer310may be changed in various ways.

Further, TFT substrate200positioned opposite to color filter substrate100comprises gate lines220which are disposed on the transparent insulative substrate and extend in a first direction to transmit a gate signal, data lines270which extend in a second direction and intersect the gate lines220in an insulated state, a pixel electrode290which is formed in a pixel region defined by the gate and data lines220and270, and a plurality of TFTs which are formed at intersection points of the gate and data lines220and270in a matrix form and connect with the pixel electrode290. Furthermore, first and second sensing lines331and333which are spaced apart from the gate and data lines220and270, respectively, by a predetermined interval are formed on TFT substrate200.

Conductive pad320is formed on a region corresponding to conductive column spacer310, i.e. on an intersection region of first and second sensing lines331and333, and conductive pad320is brought into contact with first and second sensing lines331and333. At this time, conductive pad320is formed such that it is spaced apart from conductive column spacer310by a predetermined distance when color filter substrate100and TFT substrate are bonded with each other.

When the LCD panel with a built-in touch screen so configured is touched, the touch pressure is transmitted to conductive column spacer310such that conductive column spacer310is brought into contact with the relevant conductive pad320. Then, the change in resistance, and thus the change in voltage, is produced at a contact position. At this time, the change in voltage is transmitted to the controller350through first and second sensing lines331and333, and the controller350detects the change in voltage and creates a coordinate corresponding to the change in voltage.

Meanwhile, although conductive pad320is formed on the intersection region of first and second sensing lines331and333in a state where conductive pad is spaced apart from the pixel electrode290by a predetermined interval in this embodiment, the present invention is not limited thereto. That is, conductive pad320may be formed on a variety of regions, so long as conductive pad is positioned to correspond to conductive column spacer310.

FIGS. 6A to 6Dare sectional views taken along line I-I in the LCD panel shown inFIG. 5to illustrate a process of manufacturing an example of a color filter substrate in the LCD panel with a built-in touch screen according to the present invention.

Referring toFIG. 6A, a black matrix120is first formed on a transparent insulative substrate110. At this time, the transparent insulative substrate110is generally made of a glass substrate, and the black matrix120is formed of a thin film of metal such as Cr or a carbon-based organic material. Further, the black matrix120is installed in the vicinity of a boundary of each pixel to separate color filters from one another and simultaneously blocks light transmitted through a liquid crystal cell in a region not controlled by a pixel electrode of a TFT substrate to enhance a contrast ratio of an LCD.

Referring toFIG. 6B, a plurality of color filters130, e.g. red (R), green (G) and blue (B) color filters, are formed on the substrate110with the black matrix120formed thereon. A process of forming such color filters130will be explained. A negative color photoresist with a red pigment dispersed therein is first applied on a substrate and then light-exposed using a mask. At this time, the mask is configured in such a manner that regions where red color filters will be formed are opened to be light-exposed. Then, if the negative color photoresist is developed using a developing liquid, photoinitiator in the exposed region reacts to form a polymer. Thus, the light-exposed regions are not removed but remain as a pattern during the above developing process, while only the other regions that are not light-exposed are removed. As a result, the red color filters are formed on the substrate, and green and blue color filters are also formed by repeating the aforementioned process.

Referring toFIG. 6C, a projection311is formed on the black matrix120at a predetermined interval. A process of forming the projection311will be explained as follows. That is, an organic or inorganic insulation film is first applied on an entire surface of the plurality of color filters130and a photolithography process using a mask is then performed to form the projection311.

Referring toFIG. 6D, a transparent conductive layer serving as a common electrode140is formed on an entire surface of the plurality of color filters130and the projection311through a sputtering method or the like. At this time, the common electrode140may be made of a material such as indium tin oxide (ITO) or indium zinc oxide (IZO). According to the above process of manufacturing color filter substrate, the transparent conductive layer is formed on the projection311such that a conductive column spacer310can be formed.

In order to obtain good step coverage when forming the common electrode140, an overcoat film may be formed on the plurality of color filters130.

FIG. 7is a sectional view showing another example of color filter substrate in the LCD panel with a built-in touch screen according to the present invention.

Referring toFIG. 7, color filter substrate comprises a transparent insulative substrate110, a black matrix120, a plurality of color filters130, a conductive column spacer315composed of a conductive projection, and a common electrode140.

The black matrix120is formed on the transparent insulative substrate110, e.g. a glass substrate. The plurality of color filters130, e.g. red (R), blue (B) and green (G) color filters, are then formed on the substrate with the black matrix formed thereon. Further, a transparent conductive layer serving as the common electrode140is formed on an entire surface of the plurality of color filters130through a sputtering method, and a projection made of a conductive material, i.e. conductive column spacer315, is formed on the common electrode140at a predetermined interval.

FIGS. 8A to 8Eare sectional views taken along line II-II in the LCD panel shown inFIG. 5to illustrate a process of manufacturing an example of a TFT substrate in the LCD panel with a built-in touch screen according to the present invention.

Referring toFIG. 8A, a first conductive film is first formed on a transparent insulative substrate210. Then, a gate line220, which includes a gate electrode with a predetermined line width and a storage capacitor electrode (not shown), and a first sensing line331are formed through an etching process using a first photoresist mask pattern (not shown).

Referring toFIG. 8B, a gate insulation film240, an active layer250and an ohmic contact layer260are sequentially formed on an entire surface of the substrate210shown inFIG. 8a, and an active region of a TFT is then formed through an etching process using a second photoresist mask pattern (not shown). At this time, the gate insulation film240is preferably made of an inorganic insulation material including silicon oxide or silicon nitride. An amorphous silicon layer is used as the active layer250, and a silicide or amorphous silicon layer heavily doped with N-type impurities is used as the ohmic contact layer260.

Referring toFIG. 8C, a second conductive film is formed on the entire surface of the substrate210with the active region of the TFT formed thereon, and a data line270including source and drain electrodes and a second sensing line333are then formed through an etching process using a third photoresist mask pattern (not shown).

Referring toFIG. 8D, a protection film280is formed on the entire surface of the substrate210with the TFT and the data line270formed thereon, and a portion of the protection film280is removed through an etching process using a fourth photoresist mask pattern (not shown) to form a contact hole for bringing the drain electrode into contact with an underlying pixel electrode and to form contact holes for bringing first and second sensing lines331and333into contact with an underlying conductive pad, respectively.

Referring toFIG. 8E, a third conductive film is formed on the protection film280, and then patterned using a fifth photoresist mask pattern (not shown) to form a pixel electrode290and a conductive electrode pad320. At this time, a transparent conductive film containing ITO or IZO is preferably used as the third conductive film, and conductive electrode pad320is formed on an intersection region of first and second sensing lines331and333in a state where it is spaced apart from the pixel electrode290by a predetermined interval.

FIGS. 9A to 11Bare views illustrating methods of arranging pressure particles on the LCD panel with a built-in touch screen according to the present invention, respectively.

The method shown inFIGS. 9A and 9Bwill be explained as follows. First, pressure particles600are sprayed onto color filter substrate100of the LCD panel with a built-in touch screen through a spraying method such that they are dispersed at a predetermined dispersion density (FIG. 9A). At this time, pressure particless600may be sprayed in a state where they are mixed with a solvent or using air or nitrogen. Then, the polarizing plates510and520are attached to the opposite outer surfaces of the LCD panel, respectively (FIG. 9B).

The method shown inFIGS. 10A and 10Bwill be explained below. Pressure particless600are sprayed onto an adhesive layer of first polarizing plate510to be attached to an outer surface of the LCD such that they are dispersed at a predetermined dispersion density (FIG. 10A). At this time, pressure particless600may be sprayed in a state where they are mixed with a solvent or using air or nitrogen. Then, the polarizing plates510and520are attached to the opposite outer surfaces of the LCD panel, respectively (FIG. 10B).

The method shown inFIGS. 11A and 11Bwill be explained below. First, pressure particless600are dropped on a predetermined region of color filter substrate100, i.e. on an upper region of a conductive column spacer, using a dispenser (FIG. 11A). Then, the polarizing plates510and520are attached to the opposite outer surfaces of the LCD panel, respectively (FIG. 11B).

Furthermore, to provide light to the aforementioned LCD panel, a backlight including a plurality of optical sheets, a lamp unit, a reflection plate, a light guide plate and the like is positioned below the LCD panel such that an LCD can be implemented.

As described above, an LCD panel with a built-in touch screen according to the present invention, in which pressure particles are disposed, has the following advantage. That is, an application range of touch pressure is concentrated on a local region by means of pressure particles. Thus, even though a soft touch tool having a large contact area with the LCD panel is used on the screen, it achieves substantially same effect as when a hard touch tool having a small contact area is used. As a result, the touch sensitivity can be kept at a certain level regardless of touch circumstances.

The foregoing is merely an exemplary embodiment of an LCD panel with a built-in touch screen and an LCD having the same according to the present invention. Thus, the present invention is not limited thereto. Although the present invention has been described in detail in connection with the preferred embodiment, it will be readily understood by those skilled in the art that various modifications and changes can be made thereto within the technical spirit and scope of the present invention. It is also apparent that the modifications and changes fall within the scope of the present invention defined by the appended claims.