WO2007055548A1

WO2007055548A1 - Liquid crystal display device and mobile communication terminal having the same

Info

Publication number: WO2007055548A1
Application number: PCT/KR2006/004756
Authority: WO
Inventors: Hyun Ha Hwang; Yong Gu Cho; Seung Gon Kang
Original assignee: Lg Innotek Co., Ltd
Priority date: 2005-11-14
Filing date: 2006-11-14
Publication date: 2007-05-18

Abstract

An embodiment of the present invention provides a liquid crystal display device including a liquid crystal panel, a first polarizer on a front side of the liquid crystal panel, a reflection type polarizer on a rear side of the liquid crystal panel and a second polarizer on a rear side of the reflection type polarizer.

Description

LIQUID CRYSTAL DISPLAY DEVICE AND MOBILE COMMUNICATION TERMINAL HAVING THE SAME

Technical Field

[1] The present invention relates to a liquid crystal display device and a mobile terminal having the same. Background Art

[2] Cathode ray tubes (CRTs) among screen display devices for displaying image data on a screen have been widely used, but the CRTs have a large volume and a heavy weight compared to their display area, which have been inconvenient.

[3] Accordingly, thin flat display devices that have a slim profile and a large display area and thus can be easily used in any place have been developed and are gradually replacing CRTs. Particularly, liquid crystal display (LCD) devices have excellent display resolution compared to other flat display device and have fast response time that can be compared to that of CRTs when realizing a moving image.

[4] A driving principle of the LCD device uses optical anisotropy and polarization characteristic of liquid crystal. Liquid crystal has a long and thin structure. Therefore, it is possible to control an alignment direction of liquid crystal molecules by artificially applying an electric field to the liquid crystal molecules having directionality and polarization in the molecular arrangement. Accordingly, when an alignment direction is arbitrarily controlled, light can be transmitted or blocked depending on an alignment direction of the liquid crystal molecules by optical anisotropy of the liquid crystal, so that color and an image can be displayed.

[5] Meanwhile, various studies on a dual display device that can display an image in dual directions including a front side and a rear side of an LCD device are in process. Disclosure of Invention Technical Problem

[6] An embodiment of the present invention provides a liquid crystal display device that can display an image in dual directions including a front direction and a rear direction of the liquid crystal (LC) panel using one liquid crystal (LC) panel.

[7] An embodiment of the present invention provides a thin mobile communication terminal that can display an image in dual directions using a liquid crystal display device that adopts one LC panel. Technical Solution

[8] An embodiment of the present invention provides a liquid crystal display device including: a liquid crystal panel; a first polarizer on a front side of the liquid crystal panel; a reflection type polarizer on a rear side of the liquid crystal panel; a second polarizer on a rear side of the reflection type polarizer.

[9] An embodiment of the present invention provides a mobile communication terminal including: a liquid crystal display device having a liquid crystal panel, a first polarizer on a front side of the liquid crystal panel, a reflection type polarizer on a rear side of the liquid crystal panel, and a second polarizer on a rear side of the reflection type polarizer; a communication element for performing communication with an outside; and a controller for controlling the communication element and an image displaying operation of the liquid crystal display device.

Advantageous Effects

[10] According to a liquid crystal display device of an embodiment of the present invention, an image can be displayed in dual directions of a front direction and a rear direction of a liquid crystal panel using one liquid crystal panel.

[11] According to a mobile communication terminal of an embodiment of the present invention, a thin mobile communication terminal can display an image in dual directions using a liquid crystal display device that adopts one liquid crystal panel. For example, according to an embodiment of the present invention, when a liquid crystal display module for displaying an image in dual directions is manufactured, a thin thickness of 3.5 mm or less can be achieved.

[12] According to a mobile communication terminal of an embodiment of the present invention, since images displayed on a front side and a rear side, respectively, are realized by driving modes opposite to each other, a direction in which a primary image is displayed can be selected, so that a user's privacy can be protected. Brief Description of the Drawings

[13] Fig. 1 is a conceptual view of an LCD device according to an embodiment of the present invention.

[14] Fig. 2 is a view explaining an image is displayed when a voltage is not applied to an

LC panel in an LCD device according to an embodiment of the present invention.

[15] Fig. 3 is a view explaining an image is displayed when a voltage is applied to an LC panel in an LCD device according to an embodiment of the present invention.

[16] Fig. 4 is a view illustrating an example of a folder- type mobile communication terminal that adopts an LCD device according to an embodiment of the present invention.

[17] Fig. 5 is a view illustrating an example of a bar-type mobile communication terminal that adopts an LCD device according to an embodiment of the present invention.

[18] Figs. 6 and 7 are views illustrating an example of a slide-type mobile com- munication terminal that adopts an LCD device according to an embodiment of the present invention.

[19] Fig. 8 is an exploded view of an upper unit of a slide-type mobile communication terminal according to an embodiment of the present invention. Mode for the Invention

[20] It will be understood that when a layer (or film), a region, patterns, or a structure is referred to as being "on" or "under" another layer (or film), region, or patterns, it can be directly on the other layer (or film), region, or patterns, or intervening layers may also be present.

[21] An embodiment according to the present invention will be described below in detail with reference to the accompanying drawings.

[22] Fig. 1 is a conceptual view of an LCD device according to an embodiment of the present invention.

[23] Referring to Fig. 1, the LCD device includes an LC panel 110, a first polarizer 111, a reflection type polarizer 115, a second polarizer 117, and a front light unit 120.

[24] The first polarizer 111 is formed on a front side of the LC panel 110. The reflection type polarizer 115 and the second polarizer 117 are formed on a rear side of the LC panel 110. Also, the front light unit 120 is formed on a front side of the first polarizer 111.

[25] The first and second polarizers 111 and 117 are an absorption type polarizer to transmit light linearly polarized in a direction corresponding to a transmission axis of the polarizer. The first and second polarizers 111 and 117 can be realized to have the same transmission axis or transmission axes perpendicular to each other. A suitable optical system including polarizers can be selectively realized depending on purpose, which will be described in more detail.

[26] The reflection type polarizer 115 reflects light linearly polarized in a first direction and transmits light linearly polarized in a perpendicular direction to the first direction. The reflection type polarizer 115 is designed to have the same transmission axis as that of the second polarizer 117. A dual brightness enhancement film (DBEF) can be used as the reflection type polarizer 115. Here, the first and second directions are intended for explaining directions perpendicular to each other, and actual directions associated with the LC panel 100 may change depending on a construction of an optical system.

[27] The LCD device 100 provides a first display mode displaying an image on a front side of the LC panel 110 using light passing through the LC panel 110 and reflected by the reflection type polarizer 115. Also, the LCD device 100 provides a second display mode displaying an image on a rear side of the LC panel 110 using light passing through the LC panel 110 and the reflection type polarizer 115. [28] Accordingly, images can be displayed in dual directions of the front side and the rear side of the LC panel 110. At this point, an image displayed on the front side of the LC panel 110 can be realized in a normally white mode, and an image displayed on the rear side of the LC panel 110 can be realized in a normally black mode. Also, the image displayed on the front side of the LC panel 110 can be realized in a normally black mode, and the image displayed on the rear side of the LC panel 110 can be realized in a normally white mode. Here, the images displayed on the front and rear sides depending on a selected mode are realized such that driving modes of the images are opposite to each other. Accordingly, a dark image is displayed on one of the front and rear sides such that the image is not visible by allowing a direction in which a primary image is displayed is selected.

[29] Meanwhile, the LC panel 110 includes a first substrate 101, a second substrate 103, and an LC layer 105. Since details of respective elements are well known in the art, only brief description thereof will be made.

[30] The first substrate 101 includes an array device having a thin film transistor (TFT), and a pixel electrode formed on the array device, for transmitting incident light to display an image. The array device includes a plurality of gate lines formed in a first direction, a plurality of data lines formed in a direction perpendicular to the first direction of the gate lines, a pixel region defined by the gate lines and the data lines, and a TFT formed on each of intersections of the gate lines and the data lines.

[31] Also, the second substrate 103 is disposed in a position facing the first substrate

101. The second substrate 103 includes color filters formed on position corresponding to regions of the first substrate 101 where pixel electrodes are formed, a black matrix formed between the color filters, and a common electrode formed under the color filters.

[32] The LC layer 105 is interposed between the first and second substrates 101 and 103.

A diffuser 113 may be formed between the LC panel 110 and the reflection type polarizer 115 to enhance light efficiency even more. Also, an anti-reflection film may be formed on a front side of the first polarizer to enhance quality of a displayed image even more. The anti-reflection film may be formed on a rear side of the front light unit 120.

[33] The front light unit 120 includes a light source 121 at its lateral side. For example, the light source 121 may be a light-emitting device (LED). The LED may be one of a white LED and a red LED/a green LED/a blue LED. Also, the light source 121 may be one of a cold cathode fluorescent lamp (CCFL) and an external electrode fluorescent lamp (EEFL).

[34] A process for displaying an image in the LCD device having the above construction will be described with reference to Figs. 2 and 3. Fig. 2 is a view explaining an image is displayed when a voltage is not applied to an LC panel in an LCD device according to an embodiment of the present invention, and Fig. 3 is a view explaining an image is displayed when a voltage is applied to an LC panel in an LCD device according to an embodiment of the present invention.

[35] Referring to Fig. 2, the LCD device 100 displays an image on the front side of the

LC panel 110 in white using light provided from the light source 121 of the front light unit 120 when a voltage is not applied to the LC panel 110.

[36] The light provided from the front light unit 120 becomes light linearly polarized in a first direction (e.g., a direction of <→) by passing through the first polarizer 111 because an optical system has been designed such that the first polarizer 111 has a transmission axis parallel to the first direction (the direction of <→).

[37] The light that has passed through the first polarizer 111 does not change at all while passing through the LC panel 110. This can be realized by forming the LC layer 105 such that a phase delay is not generated when a voltage is not applied to the LC panel 110. Accordingly, the light that has passed through the LC panel 110 exists as light linearly polarized in the first direction.

[38] The light that has passed through the LC panel 110 passes through the diffuser 113 and is incident on the reflection type polarizer 115. The light incident on the reflection type polarizer 115 is reflected and incident back to the LC panel 110 because the optical system has been designed such that the reflection type polarizer 115 reflects light linearly polarized in the first direction (the direction of <→) and transmits light linearly polarized in a second direction (a direction Θ) perpendicular to the first direction.

[39] When a voltage is not applied to the LC panel 110, the light incident back on the

LC panel 110 passes through the LC panel 110 without any phase delay and propagates as light linearly polarized in the first direction (the direction of <→). Also, the light that has passed through the LC panel 110 passes through the first polarizer 111 to display an image on the front side of the LC panel 110 because the linearly polarized direction (the direction of <→) of the light that has passed through the LC panel 110 is the same as the transmission axis (the direction of <→) of the first polarizer 111.

[40] As described above, when a voltage is not applied to the LC panel 110, an image is displayed on the front side of the LC panel 110 in a normally white mode, and an image is displayed on the rear side of the LC panel 110 in a normally black mode.

[41] Also, referring to Fig. 3, the LCD 100 displays an image in white on the rear side of the LC panel 110 using light provided from the light source 121 of the front light unit 120 when a voltage is applied to the LC panel 110.

[42] Light provided from the front light unit 120 becomes light linearly polarized in a first direction (e.g., a direction of <→) by passing through the first polarizer 111 because an optical system has been designed such that the first polarizer 111 has a transmission axis parallel to the first direction (the direction of <→).

[43] The light that has passed through the first polarizer 111 becomes light linearly polarized in the second direction (the direction Θ) perpendicular to the first direction (the direction of <→) by passing through the LC panel 110, which can be realized by forming the LC panel 105 such that a phase delay of λ/2 is generated when a voltage is applied to the LC panel 110. Therefore, the light that has passed through the LC panel 110 exists as light linearly polarized in the second direction (the direction Θ) perpendicular to the first direction (the direction of <→).

[44] The light that has passed through the LC panel 110 passes through the diffuser 113 and is incident on the reflection type polarizer 115. The diffuser 113 can be located on the rear side or the front side of the LC panel 110. The light that has been incident on the reflection type polarizer 115 passes through the reflection type polarizer 115 and is incident on the second polarizer 117 because the optical system has been designed such that the reflection type polarizer 115 reflects light linearly polarized in the first direction (the direction of <→) and transmits light linearly polarized in a second direction (the direction Θ) perpendicular to the first direction.

[45] The light that has been incident on the second polarizer 117 can display an image in white on the rear side of the LC panel 110 because a linearly polarized direction (the direction Θ) of the light incident on the second polarizer 117 is the same as the transmission axis direction (the direction Θ) of the second polarizer 117.

[46] That is, as described with reference to Figs. 2 and 3, in the case where the transmission axis direction of the first polarizer 111 is the first direction (the direction of <→), a phase delay difference caused by application of a voltage to the LC panel 110 is λ/2, the transmission axis direction of the reflection type polarizer 115 is the second direction (the direction Θ), and the transmission axis direction of the second polarizer 117 is the second direction (the direction Θ), the front side of the LC panel 110 is driven in the normally white mode, and the rear side of the LC panel 110 is driven in the normally black mode, so that images can be displayed in dual directions of the front and rear sides of the LC panel 110.

[47] Meanwhile, the LCD device according to an embodiment of the present invention, a construction of an optical system thereof can be controlled and a driving mode of the optical system can be modified according to the control. For example, in the case where the transmission axis direction of the first polarizer 111 is the first direction (the direction of <→), a phase delay difference caused by application of a voltage to the LC panel 110 is λ/2, the transmission axis direction of the reflection type polarizer 115 is also the first direction (the direction <→), and the transmission axis direction of the second polarizer 117 is also the first direction (the direction <→), the front side of the LC panel 110 is driven in the normally black mode, and the rear side of the LC panel 110 is driven in the normally white mode, so that images can be displayed in dual directions of the front and rear sides of the LC panel 110. Since an operation principle of the LCD device is similar to the above description, detailed description thereof will be omitted.

[48] Meanwhile, though the description has been made on the assumption that a phase delay of λ/2 is generated when a voltage is applied to the LC panel, an opposite case can be possible. That is, the LCD device can be realized such that a phase delay of λ/2 is generated when a voltage is not applied to the LC panel. The LC panel can be freely selectively operated according to user convenience.

[49] Also, though not shown in the drawing, the LCD device according to an embodiment of the present invention can display an image in dual directions of the front and rear sides of the LC panel 110 using light provided from an external light source, e.g., the sun and a surrounding lighting apparatus. That is, in the case where the front light unit 120 is in an off state, the LCD device can display an image in dual directions of the LC panel 110 using light incident from the external light source.

[50] Meanwhile, the LCD device having the above construction can be utilized as a dual sided display device. Accordingly, since the LCD device according to an embodiment of the present invention can display an image in dual directions of the front and rear sides of the LC panel in the case where the LCD device is applied to a mobile communication terminal, more various image display functions can be realized in the mobile communication terminal. Application examples are illustrated in Figs. 4 and 5. Fig. 4 is a view illustrating an example of a folder-type mobile communication terminal that adopts an LCD device according to an embodiment of the present invention, and Fig. 5 is a view illustrating an example of a bar-type mobile communication terminal that adopts an LCD device according to an embodiment of the present invention.

[51] Also, in the case where the LCD device according to an embodiment of the present invention is adopted, images displayed on the front and rear sides of the LC panel applied to a mobile communication terminal are realized such that driving modes for the images are opposite to each other. Therefore, the images displayed on the front and rear sides of the LC panel are inverted in their brightness. Accordingly, since an inverted dark image is displayed on the rear side of the LC panel in the case where a user views a bright image through the front side of the LC panel, privacy of a user can be protected. Also, in the case where a user uses a mobile communication terminal, a driving mode of the front side of the LC panel can be selected. A driving mode is set and a control signal is generated, so that a primary image can be displayed in a selected direction. [52] The mobile communication terminal includes the LCD device, a communication element, and a controller. The communication element communicates with the outside, and the controller controls the communication element and a displaying operation of the LCD device.

[53] Meanwhile, the above-descried LCD can be applied to a slide-type mobile communication terminal. Figs. 6 and 7 are views illustrating an example of a slide-type mobile communication terminal that adopts an LCD device according to an embodiment of the present invention, and Fig. 8 is an exploded view of an upper unit of a slide-type mobile communication terminal according to an embodiment of the present invention.

[54] Referring to Figs. 6 to 8, the mobile communication terminal 200 according to an embodiment of the present invention includes a main body unit 210, and an upper unit 220 mounted on a front side of the main body unit 210 in a sliding manner.

[55] The mobile communication terminal 200 can further include a camera module 215 including an image sensor and a lens. A position in which the camera module 215 is mounted can be changed in various ways depending on a mobile communication terminal. Here, description will be made for the case where the camera module 215 is mounted in the main body unit 210.

[56] The main body unit 210 includes a button part 211 for receiving a command from a user, a main board (not shown) to which a command signal input by an operation of the button part 211 is delivered, and a battery 213 detachably coupled to the main body unit 210.

[57] The upper unit 220 of the mobile communication terminal 200 includes an LCD device 230 for displaying an image data in a front direction, a front case 222 and a rear case 229 formed to protect inner parts therein, and a button part for receiving a command from a user.

[58] Also, a guide slot or a guide rail 226 is formed in the rear case 229 to allow the upper unit 220 to slide on the main body unit 210.

[59] The LCD device 230 includes a front display window for displaying an image in the front direction, and a rear display window for displaying an image in the rear direction. Referring to Fig. 7, as the upper unit 220 slides with respect to the main body unit 210 and moves to an upper side, the rear display window of the LCD device 230 can be exposed to the outside through one side of the rear case 229 of the upper unit 220.

[60] The upper unit 220 includes the front case 222 and the rear case 229 injection- molded to receive the LCD device 230.

[61] A window 223 for a front display window is formed in the front case to expose the front display window of the LCD device 230 to the outside. Also, a window 228 for a rear display window is formed in the rear case 229 to expose the rear display window to the outside.

[62] Also, the mobile communication terminal further includes a flexible circuit board

225 for delivering signals to the main board of the main body unit 210 and the LCD device 230 of the upper unit 220. The upper unit 220 is repeatedly driven in a sliding manner with respect to the main body unit 210. Therefore, the flexible circuit board 225 is formed to have elasticity and bending strength of a predetermined level or more so that a line connecting the main board with the LCD device 230 is not cut.

[63] The camera module 215 is also connected to the main board mounted on the main body unit 210. Also, an image signal obtained by the camera module 215 can be displayed as an image on the LCD device 230.

[64] When a user take a photograph of other object using the camera module 215 or views contents of a character/image, the user generally uses only the front display window of the LCD device.

[65] Unlike this, when a user drives the camera module 215 to take a photograph of himself, the user selects a drive mode so that an image is displayed in the rear direction of the LCD device 230 and thus the user can view a figure of himself through the LCD device 230. At this point, the upper unit 220 of the main body unit 210 slides with respect to the main body unit 210 to expose the rear display window of the LCD device 230 to the outside.

[66] Image signals can be processed such that an image displayed in the rear direction of the LCD device 230 is horizontally inverted with respect to an image displayed in the front direction. Accordingly, when an image obtained by the camera module 215 is displayed on the front and rear sides of the LCD device 230, the same image can be displayed.

[67] For example, when image signals obtained by the camera module 215 are delivered to the LCD device 230 via the main board, the horizontal inversion can be realized by allowing the image signals delivered via the main board to be read in a reverse direction to a standard reading direction.

[68] The above description has been made using an example where a camera module is mounted on a rear side of an LCD device. Therefore, when a position where the camera module is mounted in the LCD device changes, selection of a driving mode for displaying an image can change. Industrial Applicability

[69] According to a liquid crystal display device of an embodiment of the present invention, an image can be displayed in dual directions of a front direction and a rear direction of a liquid crystal panel using one liquid crystal panel.

[70] According to a mobile communication terminal of an embodiment of the present invention, a thin mobile communication terminal can display an image in dual directions using a liquid crystal display device that adopts one liquid crystal panel. For example, according to an embodiment of the present invention, when a liquid crystal display module for displaying an image in dual directions is manufactured, a thin thickness of 3.5 mm or less can be achieved.

[71] According to a mobile communication terminal of an embodiment of the present invention, since images displayed on a front side and a rear side, respectively, are realized by driving modes opposite to each other, a direction in which a primary image is displayed can be selected, so that a user's privacy can be protected.

Claims

[I] A liquid crystal display device comprising: a liquid crystal panel; a first polarizer on a front side of the liquid crystal panel; a reflection type polarizer on a rear side of the liquid crystal panel; a second polarizer on a rear side of the reflection type polarizer.

[2] The liquid crystal display device according to claim 1, wherein a first display mode and a second display mode are provided, the first display mode displaying an image on a front side of the liquid crystal panel using light passing through the liquid crystal panel and reflected by the reflection type polarizer, and the second display mode displaying an image on a rear side of the liquid crystal panel using light passing through the liquid crystal panel and the reflection type polarizer.

[3] The liquid crystal display device according to claim 1, comprising a front light unit on the first polarizer.

[4] The liquid crystal display device according to claim 1, wherein a phase delay difference of λ/2 is generated between transmitted light when a voltage is applied to the liquid crystal display panel, and transmitted light when a voltage is not applied to the liquid crystal display panel.

[5] The liquid crystal display device according to claim 1, wherein each of the first polarizer and the second polarizer is an absorption type polarizer.

[6] The liquid crystal display device according to claim 1, wherein the first polarizer and the second polarizer have transmission axes that are the same or perpendicular to each other.

[7] The liquid crystal display device according to claim 1, wherein the reflection type polarizer transmits light that has been linearly polarized in a first direction and reflects light that has been linearly polarized in a direction perpendicular to the first direction.

[8] The liquid crystal display device according to claim 1, wherein the reflection type polarizer and the second polarizer have the same transmission axes.

[9] The liquid crystal display device according to claim 1, wherein the reflection type polarizer comprises a dual brightness enhancement film.

[10] The liquid crystal display device according to claim 1, comprising an anti- reflection film on a front side of the first polarizer.

[I I] The liquid crystal display device according to claim 1, comprising a diffuser on one of a front side and a rear side of the liquid crystal panel.

[12] The liquid crystal display device according to claim 1, wherein one of images displayed on a front side and a rear side of the liquid crystal panel is realized in a normally white mode and the other is realized in a normally black mode.

[13] A mobile communication terminal comprising: a liquid crystal display device having a liquid crystal panel, a first polarizer on a front side of the liquid crystal panel, a reflection type polarizer on a rear side of the liquid crystal panel, and a second polarizer on a rear side of the reflection type polarizer; a communication element for performing communication with an outside; a controller for controlling the communication element and an image displaying operation of the liquid crystal display device.

[14] The mobile communication terminal according to claim 13, comprising a front light unit on the first polarizer.

[15] The mobile communication terminal according to claim 13, wherein each of the first polarizer and the second polarizer is an absorption type polarizer.

[16] The mobile communication terminal according to claim 13, wherein the first polarizer and the second polarizer have transmission axes that are the same or perpendicular to each other.

[17] The mobile communication terminal according to claim 13, wherein the reflection type polarizer transmits light that has been linearly polarized in a first direction and reflects light that has been linearly polarized in a direction perpendicular to the first direction.

[18] The mobile communication terminal according to claim 13, wherein the reflection type polarizer and the second polarizer have the same transmission axes.

[19] The mobile communication terminal according to claim 13, comprising a camera module for obtaining an external image.

[20] The mobile communication terminal according to claim 19, wherein the image obtained by the camera module is displayed in at least one direction of a front direction and a rear direction of the liquid crystal display device.