KR100641730B1 - Display Device Using Micro Light Modulator - Google Patents

Abstract

The present invention relates to a display element configured to display an image by opening and closing an optical path.

The display device using the conventional optical modulator can be applied to the front projection display device only, whereas the display device using the optical modulator according to the present invention displays an image by opening and closing the light generated from the backlight, as well as the rear projection display device. It can be applied to various display devices such as a direct view display device.

Description

Display device using micro light modulator             

1A and 1B are cross-sectional views showing display elements using a conventional optical modulator.

FIG. 2 is a perspective view showing in detail the ribbons shown in FIGS. 1A and 1B.

3 is a plan view showing the configuration of one pixel cell of the display element according to the first embodiment of the present invention;

4A is a cross-sectional view of the pixel cell taken along the line "A-A '" in FIG.

4B is a cross-sectional view of the pixel cell taken along the line "B-B '" in FIG.

5A through 5F are steps of a manufacturing method of a display device according to a first exemplary embodiment of the present invention.

6A and 6B illustrate an operation of the display device illustrated in FIG. 3.

FIG. 7 is a cross-sectional view showing design values and paths of light of the fixing member and the movable member shown in FIG. 3; FIG.

FIG. 8 is a schematic cross-sectional view of a display device to which the display device illustrated in FIG. 3 is applied.

9 is a sectional view schematically showing a liquid crystal display device.

10A and 10B are plan views showing the configuration of one pixel cell of the display element according to the second embodiment of the present invention.

FIG. 11 is a cross-sectional view showing dimensions and intervals of respective components for simulating light transmittance for the display elements shown in FIGS. 10A and 10B.

FIG. 12 is a characteristic diagram illustrating light transmittance when a back light having an angular distribution is used when the distance t between the movable members and the fixed members is changed when the dimensions and the intervals of each component are set as shown in FIG. 11. .

<Description of Symbols for Main Parts of Drawings>

1 Ribbon 2, 13, 53, 54: Board

11, 51: movable member 12, 52: fixed member

14: sacrificial layer 22: LV panel

24, 34: diffusion sheet 26, 36: back light

32: liquid crystal panel 54a: transparent electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display element for displaying an image by modulating a light beam, and more particularly, to a display element for displaying an image by opening and closing an optical path.

As a next generation display device, research on various flat panel display devices has been actively conducted. Such flat panel display devices include liquid crystal displays (hereinafter referred to as "LCDs") that have been generalized, and plasma display panels (hereinafter referred to as "PDPs") using gas discharge. The LCD has a narrow viewing angle and a slow response time, and the manufacturing process is complicated because it forms a thin film transistor (TFT) and an electrode, which are switching elements, in the semiconductor manufacturing process. PDP has the disadvantage of low discharge and luminous efficiency and high cost. In order to solve the problems of the flat panel display device, the research is continuously progressing, and new display devices are being developed to minimize these problems.

Recently, a display device capable of displaying an image by forming a fine optical modulator for each pixel cell using a micro electromechanical system (hereinafter referred to as "MEMS"), which is an ultra-fine processing technology, has been proposed. .

1A to 2, a display device using an optical modulator including a plurality of ribbons 1 in the form of strips formed on a substrate 2 is illustrated. The ribbons 1 are electrically controlled to serve to reflect or diffract incident light. These ribbons 1 comprise alternately arranged radix ribbons 1A and even ribbons 1B. The odd ribbons 1A are kept parallel to the even ribbons 1B in a dark state in which no control signal is applied to them. At this time, light incident toward the ribbons 1 is reflected at the surface of the ribbons 1 forming a plane. On the other hand, in the bright state, the odd ribbons 1A move vertically toward the silicon substrate 2 in response to the control signal. At this time, the incident light is diffracted by the interference effect of light between the odd ribbons 1A and the even ribbons 1B.

However, although the display device using the optical modulator has an advantage in that the response speed is fast, as shown in FIGS. 1A and 1B, the display device is displayed as an image using external light incident from the front of the display surface. There is a disadvantage that it can only be applied to the projective display. Since the front projection display enlarges and displays the image displayed on the display element, the display element is manufactured in a small size, and the pixel cell becomes smaller by that amount. Accordingly, the display element using the optical modulator applied to the front projection display device requires high precision in forming the ribbons 1 and the gap therebetween. In particular, in order for the normal operation to be performed in the display mode and the non-display mode, the interval between the odd ribbons 1A and the even ribbons 1B must be kept small, thus increasing the difficulty of the manufacturing process. For normal operation, the spacing d between the odd ribbons 1A and the even ribbons 1B should be 0.6 μm or less. In addition, due to the manufacturing process having high precision and difficulty, the display device using the optical modulator becomes difficult to be enlarged.

Accordingly, an object of the present invention is to provide a display device using an optical modulator to be applied to various display devices.                         

Another object of the present invention is to provide a display device using an optical modulator to improve the response speed.

Another object of the present invention is to provide a display device using an optical modulator suitable for large screen.

In order to achieve the above objects, the display device using the optical modulator according to the present invention is incident from the rear by driving by a plurality of fixing members installed side by side with a predetermined interval, and by the electrostatic force interacting with the fixing members And a plurality of movable members for opening and closing a path of light, wherein the fixing members and the movable members are installed on a substrate through which light passes, and each of the fixing members and the movable members is formed with a conductor material and an electrode. It is characterized in that any one of the non-conductive material, is provided to face the back surface of the substrate and the back light for inclining the light inclined at a predetermined angle with respect to the incident surface of the substrate, and is installed facing the exit surface of the substrate And a light diffusing member for diffusing the light emitted from the substrate.

The display device using the optical modulator according to the present invention includes a plurality of fixing members installed side by side on the lower substrate at predetermined intervals, and an upper substrate installed on the lower substrate so as to overlap both sides of the fixing members and facing the lower substrate. And a plurality of movable members for opening and closing the optical path by driving by an electrostatic force interacting with each other.

Other objects and features of the present invention in addition to the above objects will become apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 3 to 12.

Referring to FIG. 3, both ends of the fixing members 12 formed side by side at a predetermined interval on the substrate 13 and both sides of the fixing members 12 and both ends of the fixing member 12 are fixed to the substrate 13. One pixel cell of the display element using the optical modulator according to the first embodiment of the present invention having the movable member 11 is shown. The fixing members 12 may have a stripe shape as shown in FIGS. 3 and 4A and are spaced apart from the adjacent fixing members 12 by a predetermined distance. The movable members 11 overlap with both sides of the fixing members 12 in the longitudinal direction as can be seen in FIGS. 4A and 4B. The central portions of the movable members 11 overlapping each other form a plane and are lifted by a predetermined height from the substrate 13. In addition, both ends of the movable members 11 are bent toward the substrate 13 and fixed to the substrate 13. The fixing members 12 and the movable members 11 are controlled by an electrical signal to serve to open and close the optical path by an electrostatic force that interacts with the display state and the non-display state. The fixing members 12 may be made of a conductive material, an insulator material having electrodes formed thereon, or an opaque material having conductivity, and the movable members 11 may be made of an opaque material having good elastic properties. To this end, each of the fixing members 12 and the movable members 11 may be made of a multilayer thin film. Meanwhile, in FIG. 3, both sides of the movable members 11 and the fixing members 12 overlap each other, but may be installed so as not to overlap each other.

5A through 5F are steps illustrating a method of manufacturing a display device using an optical modulator according to the present invention.

Referring to FIGS. 5A and 5B, electrode materials are entirely deposited on the front surface of the substrate 13. A mask pattern is formed on the electrode material layer 12a, and the fixing members 12 are patterned by removing an unmasked portion by the mask pattern by an exposure and development process. The sacrificial layer 14 made of SiO ₂ is entirely deposited on the fixing members 12 and the substrate 13 formed as described above to cover the fixing members 22 as shown in FIG. 5C. The elastic layer material 16a and the electrode material 15a made of SiNx are sequentially deposited on the surface of the sacrificial layer 14 as shown in FIG. 5D. The elastic layer material 16a and the electrode material 15a are simultaneously patterned as shown in FIG. 5E by a photolithography process to form the elastic layer 16 and the electrode layer 15, respectively. The elastic layer 16 increases the elastic restoring force of the movable member 11. Finally, the sacrificial layer 14 is removed as shown in FIG. 5F by precipitating the substrate 13 in the etching solution containing hydrofluoric acid (HF). Here, a protective film may be formed on the substrate 13 to prevent damage of the substrate 13 from the etching solution.

6A and 6B show the operation of the display and non-display states of the display element using the optical modulator according to the first embodiment of the present invention.

Light is incident on the back surface of the substrate 13. That is, as the display device using the optical modulator according to the present invention, a back light type light source is used as a transmissive LCD.

In a non-display state as shown in FIG. 6A, a voltage of a predetermined level is applied to the fixing members 12 and the movable members 11. Then, since the attraction force by the electrostatic force is applied to the fixing members 12 and the movable members 11, the movable members 11 are in contact with the adjacent fixing members 11. At this time, the fixing members 12 and the movable members 11 block light incident from the rear surface of the substrate 13.

In the display state as shown in FIG. 6B, no voltage is applied to the fixing members 12 and the movable members 11. Then, since the movable members 11 are returned to their original state by their elastic force, they are lifted from the substrate 13 and the fixing members 11. At this time, an optical path is formed between the fixing members 12 and the movable members 11. Through this optical path, incident light is transmitted toward the display surface to display an image or an image.

As a result, in the display device using the optical modulator according to the first embodiment of the present invention, an image is displayed when no electric field is applied between the fixing members 12 and the movable members 11, so that Normally White Driven by).

For example, as shown in FIG. 7, the width of the movable member 11 is 14 μm, the distance between the adjacent movable members 11 is 6 μm, the width of the fixing member 12 is 12 μm, and the distance between the adjacent fixing members 12 is 14 μm. 8 μm, the distance between the movable member 11 and the substrate 13 is 2 μm, and the width of the overlapping portion of the movable member 11 and the fixed member 12 is 3 μm, and the incident light is perpendicular to the substrate 13. When incident at an angle of incidence of 80 ° with respect to the incident light, 8μm / 20μm = 40% is transmitted through a gap between the fixing members 12. Light incident through the gap between the movable members 11 through the gap between the fixing members 12 is about 70% or more except for the amount of light blocked at the overlapping portion of the fixing member 12 and the movable member 11. This is transmitted to the outside. In this case, the total light transmittance of the incident light is 40% x 70% = 28%. In addition, when the reflective film is formed on the bottoms of the fixing members 12, light efficiency may be increased by reflecting light reflected from the reflective film back to the display surface using the light guide plate. In addition, when the overlap width of the fixing member 12 and the movable member 11 is set to 3 μm or less, the light transmittance can be improved to about 50% or more.

FIG. 8 illustrates a display device in which pixel cells as illustrated in FIG. 3 are formed in a display panel.

Referring to FIG. 8, a display device using an optical modulator according to an exemplary embodiment of the present invention is a grating in which pixel cells having fixing members 12 and movable members 11, which serve as light valves, are arranged in a matrix form. (Grating) light valve panel (hereinafter referred to as " LV panel ") 22, which is installed on the back of the LV panel 22, passes through the back light 26 including the light source and the light guide plate, and the LV panel 22 A diffusing sheet 24 for diffusing one light is provided. The light guide plate of the back light 26 causes the white light generated from the light source to be inclined at an angle of 60 to 80 degrees with respect to the incident surface of the LV panel 22, and serves to make the distribution of the light uniform. A prism sheet may be provided on the rear surface of the diffusion sheet 24 to fold a traveling path of light emitted obliquely from the LV panel 22 in a direction perpendicular to the diffusion sheet 24.

In the LV panel 22, the fixing members 12 and the movable members 11 formed in the respective pixel cells are electrically controlled to open and close the light to display an image according to input video data. Here, since the moving distance of the movable members 11 is a small distance of 2 to 3μm has a response speed of μsec unit. The LV panel 22 is provided with driving circuit portions for driving the fixing members 12 and the movable members 11. The gray scale of the image displayed on the LV panel 22 is enabled by passive driving for dividing and displaying the video data in a time division manner according to the luminance value of the input video data. Red, green and blue color filters are formed on the LV panel 22 to realize full color.

Meanwhile, the LV panel 22 may improve light efficiency by using a color field sequential method of sequentially irradiating red, green, and blue light from the backlight 26 without forming a color filter.

Referring to FIG. 9, an LCD includes a liquid crystal panel 34 including a liquid crystal, a TFT, a data / gate driving integrated circuit, a polarizing plate, a back light 36 including a light source and a light guide plate, a liquid crystal panel 34, Diffusion sheet 34 is provided between the back light (36). The diffusion sheet 34 serves to diffuse the light irradiated from the bare 36 to the liquid crystal panel 34. A prism sheet may be formed on the back surface of the diffusion sheet 34 to fold the path of light in a direction perpendicular to the diffusion sheet 34. When the LCD is compared with the display device using the optical modulator shown in FIG. 8, the display device using the optical modulator and the backlight (26, 36), the diffusion sheet (24, 34), the prism sheet, etc. used in the LCD The same can be used to share the parts. On the other hand, the LV panel 22 has a simple structure compared to the liquid crystal panel 32 and its manufacturing method is simple as shown in FIGS. 5A to 5D.

10A and 10B show a display device using an optical modulator according to a second embodiment of the present invention.

10A and 10B, the fixing members 52 are formed side by side at a predetermined interval on the lower substrate 53 and the electrostatic force generated by the electric field applied between the upper substrate 54 and itself. One pixel cell of a display element using an optical modulator according to a second embodiment of the present invention having movable members 51 for opening and closing an optical path is shown. The fixing members 52 may be formed of a non-conductive material because no voltage is applied. However, the fixing members 52 may be formed of a material having no external light and low reflectivity to external light. The movable members 51 overlap both sides of the fixing members 52 and both ends of the movable members 51 are fixed on the lower substrate 53. The movable members 51 are made of an elastic layer for increasing the elastic restoring force and a multilayer structure of an electrode to which a voltage is applied or an electrode material having a large elastic force. On the upper substrate 54, a transparent electrode 54a made of indium tin oxide (ITO) is patterned in the form of total surface deposition or stripe. The optical path is opened and closed in accordance with the presence or absence of a voltage applied between the upper substrate 54 and the movable members 51.

The operation of the display device using the optical modulator according to the second embodiment of the present invention is as follows. First, in a non-display state as shown in FIG. 10A, no voltage is applied to the transparent electrode 54a and the movable members 51 of the upper substrate 54. At this time, the fixing members 52 and the movable members 51 maintain the interval such that the incident light incident at an oblique angle is not transmitted. For example, when incident light irradiated from the backlight is incident at an angle of 60 to 80 ° with respect to the incident surface of the lower substrate 53, the distance between the fixing members 52 and the movable members 51 is approximately 0.5 to Maintaining about 0.8μm to block incident light.

In the display state as shown in FIG. 10B, a voltage is applied between the transparent electrode 54a of the upper substrate 54 and the movable members 51. Then, the movable members 51 are attracted toward the upper substrate 54 by the electrostatic force applied between the upper substrate 54 and the movable members 51. At this time, an optical path is formed between the fixing members 52 and the movable members 51, and the light incident from the backlight through the optical path is transmitted toward the display surface to display an image or a production signal. .

Meanwhile, since the display device using the fine optical modulator shown in FIG. 3 is driven by normally white, light may pass through the gap between the fixing members 12 and the movable members 11 when no voltage is applied. An interval as large as, for example, 2 μm or more should be maintained. On the other hand, since the display device using the fine optical modulator shown in FIGS. 10A and 10B is driven with normally black, the gap between the fixing members 52 and the movable members 51 when the voltage is not applied is increased. Only 0.5 ~ 0.8μm should be maintained. Accordingly, the display device using the fine optical modulator shown in FIGS. 10A and 10B has an advantage in the manufacturing process that the thickness of the sacrificial layer 14 becomes thin.

As shown in FIG. 11, the widths a and c of each of the movable members 51 and the fixing members 52 are 12 μm, the distance b between the movable members 51 is 8 μm, and between the fixing members 52. When the interval is set to 8 μm (d) and an existing back light having an incident light angle of approximately 60 ° is used, the light transmittance with respect to incident light when a voltage is applied between the upper substrate 54 and the movable members 51 ( %) Is shown in FIG. 12. As can be seen in FIG. 12, the distance t between the movable members 51 and the fixing members 52 is caused by an electrostatic force generated as a voltage is applied between the upper substrate 54 and the movable members 51. It can be seen that as the) increases, the light transmittance (%) increases. In other words, when the distance between the movable members 51 and the fixed members 52 is within about 0.8 μm, most of the incident light is blocked by the movable members 51 and the fixed members 52, As the distance between the movable members 51 and the fixing members 52 becomes larger than 0.8 μm, the light transmittance (%) increases in proportion to the interval.

As described above, the display device using the optical modulator according to the present invention can be applied only to the front projection display device of the display device using the conventional optical modulator, whereas the display device is opened by opening and closing the light generated from the backlight. The projection display device may be applied to various display devices such as a direct view display device. In the display device using the optical modulator according to the present invention, a minute optical switching member is installed in a pixel cell using MEMS, and the optical switching member is electrically controlled according to input video data and a control signal to increase the response speed in μsec units. Can be. Accordingly, the display device using the optical modulator according to the present invention is suitable for displaying a video. The display device using the optical modulator according to the present invention has a large design margin and a simple manufacturing method as the fixing members and the movable members used as the optical switching members overlap each other, and the pixel cells are much more than the display devices for the projection display device. Since it can be applied to a large direct-view display device, it is suitable for the display of a large screen.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (12)

A plurality of fixing members installed side by side with a predetermined interval, It is provided with a plurality of movable members for opening and closing the path of light incident from the back by driving by the electrostatic force interacting with the fixing members, The fixing members and the movable members are installed on a substrate through which light passes, and each of the fixing members and the movable members is any one of a conductor material and a non-conductive material having electrodes formed thereon. A back light provided to face the back surface of the substrate to irradiate light at an angle with respect to the incident surface of the substrate at a predetermined angle; And a light diffusing member disposed to face the exit surface of the substrate to diffuse the light emitted from the substrate. delete The method of claim 1, And the fixing members and the movable members are installed in the pixel cells, respectively. delete The method of claim 1, And the fixed members and the movable members generate the electrostatic force in response to an electrical control signal supplied to the fixed members and the movable members. The method of claim 3, wherein And a display panel in which the pixel cells are arranged in a matrix to display images in full color by sequentially irradiating red, green, and blue light. A plurality of fixing members are installed side by side on the lower substrate at a predetermined interval, And a plurality of movable members installed on the lower substrate so as to overlap both sides of the fixing members and driven by an electrostatic force interacting with the upper substrate facing the lower substrate to open and close the optical path. Display element using a modulator. The method of claim 7, wherein And each of the movable members and the upper substrate is formed with an electrode to which a voltage signal is applied. The method of claim 7, wherein The fixing members may be any one of a conductive material and a non-conductive material having electrodes formed thereon, and the display device using the optical modulator characterized in that the material is made of a material having a low light transmittance with respect to external light and a low external light reflectance. The method of claim 7, wherein And the fixing members and the movable members are installed in the pixel cells, respectively. The method of claim 7, wherein And the movable members and the upper substrate generate the electrostatic force in response to an electrical control signal supplied to the movable members and the upper substrate. The method of claim 10, And a display panel in which the pixel cells are arranged in a matrix to display images in full color by sequentially irradiating red, green, and blue light.

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