KR20080054573A - Display device - Google Patents

Abstract

A display device is provided to form an upper quarter wave plate under an upper polarizer of a display device having a touch screen panel to prevent light inputted to the display device from being reflected and emitted to the outside. A display device includes an LCD panel, a touch screen panel, an upper quarter wave plate(25), and an upper polarizer(22). The LCD panel includes a lower substrate(110) and an upper substrate(210). The touch screen panel is attached to the upper substrate of the LCD panel. The upper quarter wave plate is attached to the top face of the touch screen panel. The upper polarizer is attached to the top face of the quarter wave plate.

Description

Display device {DISPLAY DEVICE}

1 is a cross-sectional view of a display device according to an exemplary embodiment of the present invention.

2 is a view showing a display principle of white and black according to an embodiment of the present invention.

3 is a cross-sectional view illustrating a principle of removing reflected light according to an embodiment of the present invention.

<Description of Drawing>

3: liquid crystal layer 12: lower polarizing plate

15: lower λ / 4 plate 22: upper polarizing plate

25: upper λ / 4 plate 110: lower substrate

190: pixel electrode 210: upper substrate

230: color filter 250: common electrode

310: lower contact electrode 320: upper contact electrode

350: spacer 370: seal member

360: air layer

The present invention relates to a display device having a touch screen panel.

Typical liquid crystal displays (LCDs) among display devices include two display panels provided with pixel electrodes and a common electrode, and a liquid crystal layer having dielectric anisotropy interposed therebetween. The pixel electrodes are arranged in a matrix and connected to switching elements such as thin film transistors (TFTs) to receive data voltages one by one in sequence. The common electrode is formed over the entire surface of the display panel and receives a common voltage. The pixel electrode, the common electrode, and the liquid crystal layer therebetween form a liquid crystal capacitor, and the liquid crystal capacitor becomes a basic unit that forms a pixel together with a switching element connected thereto.

In such a liquid crystal display, a voltage is applied to two electrodes to generate an electric field in the liquid crystal layer, and the intensity of the electric field is adjusted to adjust the transmittance of light passing through the liquid crystal layer to obtain a desired image.

A touch screen panel refers to a device that touches a finger or a pen on the screen to write and draw a character or a picture, or executes an icon to perform a desired command on a machine such as a computer. The liquid crystal display with a touch screen panel may find out whether the user's finger or a touch pen touches the screen and the contact position information.

The touch screen panel is formed outside the upper substrate of the liquid crystal display. As described above, when the touch screen panel is formed on the outside of the touch screen panel, light incident on the touch screen panel from the outside is reflected to blur the image of the display device. That is, as a few more layers are added on the upper side of the display device, reflection occurs at the boundary between each layer and the layers, thereby degrading display quality.

An object of the present invention is to provide a display device having a touch screen panel to reduce the display of light incident from the outside to be visually recognized to improve the display quality.

In order to solve this problem, in the present invention, a λ / 4 plate is attached to the outside of the touch screen and a polarizer is attached to the upper portion thereof.

Specifically, the display device according to the embodiment of the present invention includes a liquid crystal display including a lower substrate and an upper substrate; A touch screen unit attached to an upper substrate of the liquid crystal display unit; And an upper λ / 4 plate attached to an upper surface of the touch screen portion, and an upper polarizer plate attached to an upper side of the upper λ / 4 plate.

The liquid crystal display may further include a lower λ / 4 plate attached to a lower side of the lower substrate of the liquid crystal display unit, and a lower polarizer attached to a lower side of the lower λ / 4 plate.

Transmission axes of the upper polarizer and the lower polarizer may be perpendicular to each other.

The slow axis of the upper λ / 4 plate and the lower λ / 4 plate may form 45 degrees with the upper and lower polarizers.

The touch screen unit may include a lower contact electrode attached to an upper surface of the upper substrate, and an upper contact electrode formed to face the lower contact electrode and to be spaced apart at a predetermined distance.

The touch screen unit may further include a seal member formed along both ends of the lower contact electrode and the upper contact electrode to support the upper contact electrode, and a spacer to maintain a distance between the lower contact electrode and the upper contact electrode. can do.

The lower contact electrode may be formed of a transparent conductor, and the upper contact electrode may be formed of an ITO film.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

First, a display device according to an exemplary embodiment of the present invention will be described in detail with reference to FIG. 1.

1 is a cross-sectional view of a display device according to an exemplary embodiment of the present invention.

The display device according to the exemplary embodiment of the present invention includes a pixel electrode 190, a common electrode 250, a color filter 230, a liquid crystal layer 3, and the like between the upper substrate 210 and the lower substrate 110. (Hereinafter referred to as a liquid crystal display unit), the lower λ / 4 plate 15 and the lower polarizing plate 12 are sequentially attached to the lower side of the lower substrate 110.

The lower contact electrode 310 is formed on the upper side of the upper substrate 210, and the spacer 350 and the seal member 370 are formed on the upper side of the lower contact electrode 310. An upper contact electrode 320 is formed on the seal member 370 and the spacer 350, and the upper contact electrode 320 is supported by the seal member 370. An air layer 360 is formed in a space between the upper contact electrode 320 and the lower contact electrode 310. If necessary, other materials other than the air layer 360 may be filled. The upper contact electrode 320, the lower contact electrode 310, and a structure therebetween are referred to as a “touch screen portion” below.

The upper λ / 4 plate 25 and the upper polarizer 22 are sequentially attached to the upper surface of the upper contact electrode 320.

Looking at the structure of the display device according to the embodiment of Figure 1 in detail as follows.

FIG. 1 briefly illustrates only common components of the liquid crystal display. The liquid crystal display may be formed in various embodiments, and the structure of the general liquid crystal display is as follows.

A plurality of gate lines (not shown) and a plurality of storage electrode lines (not shown) are formed on the lower substrate 110 made of transparent glass or plastic.

The gate line transmits a gate signal and mainly extends in the horizontal direction. Each gate line includes a wide end portion for connection with a plurality of gate electrodes (not shown) protruding downward and another layer or an external driving circuit.

The storage electrode line receives a predetermined voltage and includes a storage electrode (not shown). In addition, the sides of the gate line and the storage electrode line are inclined with respect to the lower substrate 110 surface, and the inclination angle is preferably about 30 ° to about 80 °.

A gate insulating film (not shown) made of silicon nitride (SiNx) or silicon oxide (SiOx) is formed on the gate line and the storage electrode line.

A semiconductor (not shown) made of hydrogenated amorphous silicon, polycrystalline silicon, or the like is formed on the gate insulating film. The semiconductor mainly extends in the longitudinal direction and includes a plurality of protrusions (not shown) extending toward the gate electrode.

An ohmic contact (not shown) is formed on the semiconductor. The ohmic contact member may be made of a material such as n + hydrogenated amorphous silicon in which n-type impurities such as phosphorus (P) are heavily doped, or may be made of silicide. The linear ohmic contact has a plurality of protrusions (not shown), and the protrusion and the ohmic contact are paired and disposed on the protrusion of the semiconductor.

Sides of the semiconductor and the ohmic contact are also inclined with respect to the lower substrate 110, and the inclination angle is about 30 ° to 80 °.

A plurality of data lines (not shown) and a plurality of drain electrodes (not shown) are formed on the ohmic contact member and the gate insulating film.

The data line transmits a data signal and mainly extends in the vertical direction to intersect with the gate line and intersect with the storage electrode line. Each data line includes a plurality of source electrodes (not shown) extending toward the gate electrode and end portions (not shown) having a large area for connection with another layer or an external driving circuit.

The drain electrode is separated from the data line and faces the source electrode with respect to the gate electrode.

One gate electrode, one source electrode, and one drain electrode form one thin film transistor together with the protrusion of the semiconductor, and a channel of the thin film transistor is formed in the protrusion between the source electrode and the drain electrode.

It is also preferable that the data line and the drain electrode are inclined at an inclination angle of about 30 ° to about 80 ° with respect to the lower substrate 110 surface.

The ohmic contact is present only between the semiconductor underneath and the data line and drain electrode thereon and lowers the contact resistance therebetween.

A protective film (not shown) is formed on the data line, the drain electrode, and the exposed semiconductor portion. The protective film is made of an inorganic insulator such as silicon nitride or silicon oxide, an organic insulator, or a low dielectric insulator.

A plurality of contact holes (not shown) are formed in the passivation layer to expose an end portion of the data line and a drain electrode, respectively. A plurality of contact holes (not shown) are exposed in the passivation layer and the gate insulating film, and the sustain electrode is fixed. A plurality of contact holes (not shown) are formed to expose a part of the sustain electrode line near the end.

A plurality of pixel electrodes 190 and a plurality of contact assistants (not shown) are formed on the passivation layer. These may be made of a transparent conductive material such as ITO or IZO or a reflective metal such as aluminum, silver or an alloy thereof.

The pixel electrode 190 is physically and electrically connected to the drain electrode through the contact hole, and receives a data voltage from the drain electrode. In addition, the pixel electrode 190 overlaps the storage electrode line including the storage electrode. The capacitor formed by the pixel electrode 190 and the drain electrode electrically connected thereto is called a storage capacitor, and the storage capacitor enhances the voltage holding capability of the liquid crystal capacitor.

The contact auxiliary members are connected to the ends of the gate lines and the ends of the data lines through contact holes, respectively.

Meanwhile, the upper substrate 210 is made of glass, plastic, or the like, and a light blocking member (not shown) is formed on the insulating substrate 210. The light blocking member includes a linear portion corresponding to the gate line and the data line and a planar portion corresponding to the thin film transistor, and prevents light leakage between the pixel electrodes 190.

A plurality of color filters 230 is also formed on the upper substrate 210. The color filter 230 is mostly present in an area surrounded by the light blocking member, and may extend in the vertical direction along the column of the pixel electrodes 190. Each color filter 230 may display one of primary colors such as three primary colors of red, green, and blue.

An overcoat (not shown) is formed on the color filter 230 and the light blocking member. The overcoat may be made of an organic insulator, which prevents the color filter 230 from being exposed and provides a flat surface.

The common electrode 250 is formed on the overcoat. The common electrode 250 is made of a transparent conductor such as ITO or IZO.

An alignment layer (not shown) is coated on the inner surfaces of the pixel electrode 190 and the common electrode 250, and may be a vertical alignment layer or a horizontal alignment layer.

The liquid crystal layer 3 positioned between the pixel electrode 190 and the common electrode 250 has dielectric anisotropy. In the absence of an electric field, the liquid crystal molecules of the liquid crystal layer 3 are in a vertical alignment (VA) mode in which their major axes are oriented perpendicular to the surfaces of the two substrates 110 and 210 or the two substrates 110 and 210. It may have a twisted nematic (TN) mode that is oriented to be horizontal to the surface of.

When a common voltage is applied to the common electrode 250 and a data voltage is applied to the pixel electrode 190, an electric field (electric field) is generated therebetween. Liquid crystal molecules change their orientation in response to an electric field.

The liquid crystal display may be formed in various embodiments, and thus, the liquid crystal display may be formed in an embodiment in which the common electrode 250 and the pixel electrode 190 are formed on the same substrate.

The lower λ / 4 plate 15 and the lower polarizer 12 are sequentially attached to the lower side of the liquid crystal display lower substrate 210. The lower λ / 4 plate 15 and the lower polarizer 12 are attached to each other via an adhesive.

On the other hand, the touch screen unit is formed above the liquid crystal display upper substrate 110. The touch screen unit generates a signal by detecting a contacted position when the lower contact electrode 310 and the upper contact electrode 320 are touched by an external touch.

The lower contact electrode 310 is formed on the upper surface of the liquid crystal display upper substrate 110. The seal member 370 is positioned along the outer surface of the lower contact electrode 310, and the spacer 350 is disposed at a predetermined interval inside the seal member 370 above the lower contact electrode 310. Is located. The upper contact electrode 320 is formed on the lower contact electrode 310 to face the lower contact electrode 310 while being supported by the seal member 370. The seal member 370 supports the upper contact electrode 320 and the components thereon (upper λ / 4 plate 25 and upper polarizer 22). The spacer 350 prevents the upper contact electrode 320 and the lower contact electrode 310 from contacting each other even without an external touch, and the upper contact electrode 320 and the lower contact electrode 310 are contacted by an external touch. After contact, it serves to fall back. The spacer 350 is preferably formed of an insulating material. An air layer 360 is formed in a space between the upper contact electrode 320 and the lower contact electrode 310 formed by the seal member 370.

The upper contact electrode 320 and the lower contact electrode 310 are formed of a transparent conductor such as ITO or IZO, and the upper contact electrode 320 is formed of an ITO film such that the upper λ / 4 plate 25 and the upper polarizer ( 22) may be attached.

On the other hand, the upper λ / 4 plate 25 and the upper polarizer 22 are sequentially attached to the upper side of the touch screen upper contact electrode 320 by an adhesive.

The image display operation of the display device having the touch screen unit as described above will be described.

2 is a view showing a display principle of white and black according to an embodiment of the present invention.

FIG. 2 briefly illustrates a structure of the liquid crystal display according to the present embodiment shown in FIG. 1. That is, only the upper and lower polarizing plates 22 and 12, the upper and lower λ / 4 plates 25 and 15, and the liquid crystal layer 3 are shown. Other components are omitted because they do not affect the polarization direction of light.

First, the left phase shift of FIG. 2 displaying white through the display device will be described.

Light incident from the backlight unit 500 includes light in all directions. This light first passes the lower polarizer 12 and then the lower λ / 4 plate 15. Light having components in all directions is polarized while passing through the lower polarizer 12 to have only components in one direction. As shown in FIG. 2, in the display device according to the exemplary embodiment of the present invention, the lower polarizer 12 blocks light in the X-axis (↔) direction and transmits light in the Y-axis (⊙) direction. have. That is, the absorption axis is in the X axis (↔) direction, and the transmission axis is in the Y axis (⊙) direction. As a result, the light transmitted through the lower polarizing plate 12 has only components in the Y-axis direction.

Light passing through the lower polarizer 12 is incident on the lower λ / 4 plate 15. The lower λ / 4 plate 15 according to the embodiment of the present invention has a slow axis at an angle of 45 degrees with respect to the X axis or the Y axis. In addition, the lower λ / 4 plate 15 has a fast axis perpendicular to the slow axis. The light transmitted through the λ / 4 plate is delayed in phase by λ / 4 as compared with light in the slow axial direction. As a result, light that is linearly polarized becomes circularly polarized light after passing the [lambda] / 4 plate. In the embodiment of the present invention, light having a component in the Y-axis direction is transmitted to the lower λ / 4 plate 15 and has left circularly polarized light.

After passing through the lower λ / 4 plate 15, the light enters the liquid crystal layer 3, and in the liquid crystal layer 3, the voltage between the pixel electrode 190 and the common electrode 250 is adjusted to λ / Give phase difference of 2. That is, the liquid crystal layer 3 also has a slow axis and a fast axis that are the same or perpendicular to the lower λ / 4 plate 15, and provide a phase difference of λ / 2 between both axes. As a result, the left circularly polarized light turns into right circularly polarized light. The upper λ / 4 plate 25 also has the same slow axis and faster axis as the lower λ / 4 plate 15, and the upper polarizer 22 has a transmission axis and an absorption axis in a direction perpendicular to the lower polarizer 12, X The light in the axial direction is transmitted and the light in the Y direction is blocked.

Therefore, the light converted into the right polarized light through the liquid crystal layer 3 enters the upper λ / 4 plate 25 to be converted into light in the X-axis (↔) direction, and then passes through the upper polarizing plate 22 to produce white light. Will be displayed. Although the color filter 230 is omitted in the present description, when the color filter 230 is considered, the color of the color filter 230 is displayed to display a color image.

Meanwhile, a case in which the display device displays black through the right phase relationship of FIG. 2 will be described below.

Light incident from the backlight unit 500 includes light in all directions. This light first passes the lower polarizer 12 and then the lower λ / 4 plate 15. Light having components in all directions is polarized while passing through the lower polarizer 12 to have only components in one direction. As shown in FIG. 2, in the display device according to the exemplary embodiment of the present invention, the lower polarizer 12 blocks light in the X-axis (↔) direction and transmits light in the Y-axis (⊙) direction. have. That is, the absorption axis is in the X-axis (↔) direction, and the transmission axis is in the Y-axis (⊙) direction. As a result, the light transmitted through the lower polarizing plate 12 has only components in the Y-axis direction.

Light passing through the lower polarizer 12 is incident on the lower λ / 4 plate 15. The lower λ / 4 plate 15 according to the embodiment of the present invention has a slow axis at an angle of 45 degrees with respect to the X axis or the Y axis. In addition, the lower λ / 4 plate 15 has a fast axis perpendicular to the slow axis. The light transmitted through the λ / 4 plate is delayed in phase by λ / 4 as compared with light in the slow axial direction. As a result, light that is linearly polarized becomes circularly polarized light after passing the [lambda] / 4 plate. In the embodiment of the present invention, light having a component in the Y-axis direction is transmitted to the lower λ / 4 plate 15 and has left circularly polarized light.

After passing through the lower λ / 4 plate 15, the light is incident on the liquid crystal layer 3, and the liquid crystal layer 3 adjusts a voltage between the pixel electrode 190 and the common electrode 250 to adjust a phase difference to light transmitted therethrough. Form not to add. As a result, the light transmitted through the liquid crystal layer 3 is maintained in the left circularly polarized light as it is. The upper λ / 4 plate 25 also has the same slow and fast axis as the lower λ / 4 plate 15, and the upper polarizer 22 has a transmission axis and an absorption axis in a direction perpendicular to the lower polarizer 12, X The light in the axial direction is transmitted and the light in the Y direction is blocked.

Therefore, even after passing through the liquid crystal layer 3, the light maintained in the left circularly polarized light is incident on the upper λ / 4 plate 25 to be turned into the light in the Y-axis direction, and then blocked by the upper polarizing plate 22. It is displayed black.

The reflection light removal principle of the display device having the touch screen unit operating as described above will be described.

3 is a cross-sectional view illustrating a principle of removing reflected light according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of the structure of the liquid crystal display according to the present exemplary embodiment of FIG. 1 according to a path of reflected light. That is, only the upper polarizing plate 22, the upper λ / 4 plate 25, and the layer on which the light is reflected (such as the air layer 360 or the lower contact electrode 310) are shown. Other components are omitted because they do not affect the reflection of light.

Light incident from the outside is light having components in all directions. When the external light passes through the upper polarizing plate 22, only the light corresponding to the transmission axis of the upper polarizing plate 22 (the X axis ↔ direction) is transmitted, and other light is blocked.

Light in the X-axis (↔) direction passing through the upper polarizing plate 22 is incident and transmitted to the upper λ / 4 plate 25. The upper λ / 4 plate 25 has a slow axis that makes an angle of 45 degrees with respect to the X or Y axis, and has a fast axis perpendicular thereto. The light transmitted through the upper λ / 4 plate 25 has a phase difference of λ / 4 between the axes of which fast reflection is slow. As a result, the light in the X-axis (↔) direction passes through the upper λ / 4 plate 25 and changes into right polarized light.

The light transmitted through the upper λ / 4 plate 25 while being converted into right polarized light is reflected at the interface of the air layer 360 or the lower contact electrode 310 of the touch screen, and the phase is changed 180 degrees, thereby changing to left circular polarized light. The reflected left circularly polarized light is incident on the upper λ / 4 plate 25 and transmitted to change its phase in the Y-axis direction. As a result, the reflected light does not pass through the upper polarizing plate 22, and the display quality does not deteriorate due to the reflected light when viewed from the outside.

As described above, in the display device having the touch screen panel, the upper λ / 4 plate is formed under the upper polarizing plate so that light incident from the outside is not reflected and emitted to the outside. As a result, when the image of the display device is viewed from the outside, the display quality is not degraded due to the reflected light.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (7)

A liquid crystal display including a lower substrate and an upper substrate; A touch screen unit attached to an upper substrate of the liquid crystal display unit; An upper λ / 4 plate attached to an upper surface of the touch screen portion, and And an upper polarizing plate attached to an upper surface of the upper λ / 4 plate. In claim 1, A lower λ / 4 plate attached to a lower side of the lower substrate of the liquid crystal display, and And a lower polarizer attached to the lower side of the lower λ / 4 plate. In claim 2, And a transmission axis of the upper polarizer and the lower polarizer is perpendicular to each other. In claim 3, The slow axis of the upper λ / 4 plate and the lower λ / 4 plate is 45 degrees with the upper and lower polarizers. In claim 1, The touch screen unit A lower contact electrode attached to an upper surface of the upper substrate, and And an upper contact electrode facing the lower contact electrode and spaced apart from each other at a predetermined distance. In claim 5, The touch screen unit A seal member formed along both ends of the lower contact electrode and the upper contact electrode and supporting the upper contact electrode; And a spacer configured to maintain a gap between the lower contact electrode and the upper contact electrode. In claim 5, The lower contact electrode is formed of a transparent conductor and the upper contact electrode is formed of an ITO film.

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