KR20090118309A - Transflective display panel and display apparatus employing the same - Google Patents

Abstract

PURPOSE: A transflective display panel and a display apparatus using the same are provided to use outdoor light in forming an image, thereby improving outdoor visibility. CONSTITUTION: A color filter(160) comprises pixels. The pixel comprises a plurality of sub pixels(160a,160b,160c). The pixels are repeatedly arranged two dimensionally. The sub pixels transmit light of different wavelength bands. Using electrical control, a transmission rate of incident light is controlled at a sub pixel unit. A liquid crystal layer(130) comprises transmitting areas(Ta,Tb,Tc) and reflecting areas(Ra,Rb,Rc). The transmitting areas and reflecting areas correspond to the sub pixel. In the reflecting area, a computer generation hologram is formed.

Description

Transflective display panel and display apparatus employing the same

The present invention relates to a display panel and a display device, and more particularly, to a display panel and a display device having excellent outdoor visibility since natural light illuminated from the outside can be used.

Recently, many portable terminals have been developed due to the development of communication technology and display devices. Portable terminals include, for example, personal digital assistants (PDAs), portable multimedia players (PMPs), digital multimedia broadcasting (DMBs), and the like.

Liquid crystal display devices (LCDs), which are a type of light-receiving flat panel displays commonly used in such portable terminals, form an image by using a change in transmittance of light passing through a liquid crystal cell according to an applied voltage. Since there is no light emitting capability, a separate light source device such as a backlight unit is required.

On the other hand, the portable terminal is required to be able to be used anywhere in the nature of the portability due to the nature of portability, for example, to be used in a dark place or a sea or a ski resort with strong sunlight, high level outdoor Visibility must be secured. In addition, even when a liquid crystal display element is employed in an outdoor billboard or an exhibition display in a brightly lit public place, its utilization is not large unless visibility is secured.

To this end, recently, researches on transflective LCDs combining a transmissive LCD using a conventional backlight unit with a reflective function using outdoor light have been actively conducted. Since the transflective LCD forms an image using light from the backlight unit and / or outdoor light, visibility of the display is secured even when used in a bright environment where sunlight shines, and it is also advantageous to reduce power consumption.

The semi-transmissive LCD includes a reflection area and a transmission area for each liquid crystal cell area. The reflection area includes a reflection layer reflecting light or a scattering layer scattering light. In this case, when the direction of the reflected light in the reflection area is not controlled, the light collected at the viewing angle of the viewer may be less, and thus the front luminance may be lowered.

The present invention has been made in accordance with the above-described needs, and an object of the present invention is to provide a display panel and a display device having a structure that can be operated with excellent outdoor visibility and low power consumption by using outdoor light.

According to an exemplary embodiment of the present invention, a display panel includes a color filter in which pixels consisting of a plurality of sub pixels transmitting light of different wavelength bands are repeatedly arranged two-dimensionally; The transmittance of the incident light is controlled by the sub-pixel unit by electrical control, and a region corresponding to the sub-pixel includes a liquid crystal layer having a transmissive region and a reflective region, wherein the computer-generated hologram is formed in the reflective region. do.

Display device according to the present invention comprises a backlight unit for illuminating light; The transmittance of incident light is adjusted in units of the sub-pixels by a color filter in which pixels consisting of a plurality of sub-pixels transmitting light of different wavelength bands are repeatedly arranged two-dimensionally and electrically controlled, and an area corresponding to the sub-pixels And a display panel having a liquid crystal layer including a transmissive region and a reflective region, wherein the computer generated hologram is formed in the reflective region.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, like reference numerals refer to like elements, and the size of each element in the drawings may be exaggerated for clarity and convenience of description.

1 is a schematic view of a display panel 100 according to an embodiment of the present invention. The display panel 100 forms an image by adjusting light transmittance in units of sub-pixels emitting different color light. In the present invention, the liquid crystal layer 130 corresponding to the sub-pixels has reflection regions Ra, Rb, Rc) and transmission regions Ta, Tb, and Tc implement a mode for reflecting incident light L _R and displaying an image, and a mode for transmitting incident light L _T and displaying an image.

The liquid crystal layer 130 is provided between the upper and lower transparent substrates 180 and 120, and the color filter 160 is provided on the lower surface of the upper transparent substrate 180. The color filter 160 includes a plurality of sub-pixels that transmit light having different wavelength bands, that is, a first sub-pixel 160a, a second sub-pixel 160b, and a third sub-pixel 160c. The first, second, and third sub-pixels 160a, 160b, and 160c form one basic pixel, and the color filter 160 has a structure in which the basic pixels are repeatedly arranged two-dimensionally. However, only one basic pixel is shown in the drawing. The first, second, and third sub-pixels 160a, 160b, and 160c may be configured to transmit, for example, light having a wavelength band corresponding to red, green, and blue, respectively. Each of the regions of the liquid crystal layer 130 corresponding to the first to third sub-pixels 160a, 160b, and 160c includes the reflective regions Ra, Rb, and Rc, and the transmission regions Ta, Tb, and Tc. Each of the reflective regions Ra, Rb, and Rc is provided with a first CGH layer 150a, a second CGH layer 150b, and a third CGH layer 150c, each of which has a computer generated hologram CGH. For example, a support layer 140 made of an organic material is provided in each of the reflective regions Ra, Rb, and Rc, and the first CGH layer 150a, the second CGH layer 150b, and the third CGH layer (on the support layer 140). 150c). The computer-generated hologram is patterned such that the incident light has a predetermined light emission distribution and is diffracted and reflected, which will be described later in FIGS. 2 to 6. The thickness of the liquid crystal layer 130 in the reflective regions Ra, Rb and Rc and the thickness of the liquid crystal layer 130 in the transmissive regions Ta, Tb and Tc vary depending on the thickness of the support layer 140. For example, the thickness d1 of the liquid crystal layer 130 in the reflection regions Ra, Rb, and Rc is equal to half the thickness d2 of the liquid crystal layer 130 in the transmission regions Ta, Tb, and Tc. The support layer may be configured to compensate the optical path difference between the light L _T for forming an image in the transmission regions Ta, Tb, and Tc and the light L _R for forming an image in the reflection regions Ra, Rb, and Rc. 140 may be determined.

An upper polarizer 190 and a lower polarizer 110 are provided on the upper surface of the upper transparent substrate 180 and the lower surface of the lower transparent substrate 120, respectively, and although not shown, electrical control of incident light transmittance in sub-pixel units. A TFT layer may be further provided.

Referring to the operation of the display panel 100 of the present invention to form an image in the transmission mode and reflection mode as follows.

Light L _R incident toward the reflective regions Ra, Rb, and Rc exits the liquid crystal layer 130 to form an image. That is, for example, the light L _R incident toward the reflective region Rb passes through the upper polarizer 190 and the second sub-pixel 160b of the color filter 160 as green light linearly polarized in a predetermined direction. It is converted and is incident on the liquid crystal layer 130. Light incident on the liquid crystal layer 130 is diffracted and reflected by the second CGH layer 150b to exit the liquid crystal layer 130. The liquid crystal layer 130 is controlled so as not to change or change the polarization of incident light by electrical control of the TFT layer, which is not shown, and is controlled on / off by not transmitting or not transmitting the upper polarizer 190 according to the polarization state. Form an image.

The light L _T incident toward the transmission regions Ta, Tb, and Tc forms an image while passing through the liquid crystal layer 130. That is, for example, the light L _T incident toward the transmission region Tb may include the lower polarizer 110, the liquid crystal layer 130, the second subpixel 160b of the color filter 160, and the upper polarizer plate ( 190) sequentially pass. The polarization of the incident light passing through the lower polarizer 110 is converted into linearly polarized light in a predetermined direction. The liquid crystal layer 130 is electrically controlled so that the polarization of the incident light is changed or not changed. The light is converted into green light by the second sub-pixel 160b and controlled on / off by not transmitting or transmitting the upper polarizing plate 190 according to its polarization state, thereby forming an image. Here, the light L _T forming the image in the transmission regions Ta, Tb, and Tc is opposite to the direction shown in the upper polarizer 190, the color filter 160, the liquid crystal layer 130, and the lower polarizer 110. It is also possible to be configured to pass through the image forming sequentially.

Transmitting region light (L _T), which is incident to the light (L _T) and reflection regions (Ra, Rb, Rc) which is incident on (Ta, Tb, Tc) are provided separately with natural light, some configurations of outside light or a display device It may be light illuminated in a backlight unit or a front-light unit.

2 is a diagram illustrating a computer-generated hologram formed on the first CGH layer 150a. The computer-generated hologram is patterned by computer simulation, and the CGH unit block 152 composed of a diffraction pattern based on the urea cell 155 is an array arranged repeatedly. Here, the pattern or the number of arrays of the CGH unit blocks 152 is exemplary. The pattern of the CGH unit block 152 or the pitch in which the CGH unit block 152 is arranged is determined by computer simulation so that incident light having a predetermined wavelength has a predetermined light output distribution, and in addition, the CGH in consideration of the size of the corresponding subpixel The number of arrangements of the unit blocks 152 is determined.

Although not illustrated separately for the second CGH layer 150b and the third CGH layer 150c, the CGH unit blocks 152 are the same in that they are an array in which the CGH unit blocks 152 are repeatedly arranged. There is a difference in the specific pattern formed by the element cells 155 of the unit block 152 or the pitch in which the CGH unit block 152 is arranged.

3 is a conceptual diagram for explaining a rough estimation of the size of the element cell 155 forming the pattern of the CGH unit block 152. When the light having the wavelength λ is incident on the pattern formed by the urea cell d at the incident angle θ, the following equation is used to vertically emit the first diffracted light.

d sinθ = λ

Assuming a wavelength of 530 nm corresponding to green light and an incident angle of 30 °, d is about 1 μm.

The required size of the urea cell 155 is in a range of about 1 μm ² , which is a numerical value that can be manufactured at a relatively low resolution. For example, even when considering blue light having a shorter wavelength than green light, the element cell 155 may have a size of about 0.5 μm ² or more.

4 is a conceptual diagram for explaining and predicting, roughly, the pitch in which the CGH unit blocks 152 are arranged. When light incident on the array of CGH unit blocks 152 is diffracted, the diffraction orders and diffraction angles follow the following equation.

p sinθ _m = m λ

Assuming that the wavelength 530 nm corresponding to the green light and the viewing angle, for example, secure 10 ° (θ _{m = 5} = 10 °), it is possible to produce a pitch p of about 16 μm. In consideration of the wavelength range of red light, green light and blue light, the pitch p is in the range of approximately 5 mu m to 20 mu m.

5 is a micrograph image of a computer generated hologram made in accordance with an embodiment of the present invention. CGH unit blocks of the same structure, which can be easily manufactured at low resolution, are repeatedly arranged, so that they are structurally simpler and easier to manufacture than other technologies, for example, diffraction gratings.

6 illustrates various CGH unit blocks designed according to an embodiment of the invention. In the figure, the left row shows the outgoing distribution that is the target of computer simulation, and the middle row shows the pattern shape of the computer simulated CGH unit block to have the outgoing distribution on the left, and the next two rows on the right show the outgoing distribution predicted by the simulation. And efficiency.

7 shows a schematic structure of a display device 300 according to an embodiment of the present invention. The display apparatus 300 according to the present invention displays an image by using the display panel 100 according to the exemplary embodiment of the present invention. Referring to the drawing, the display apparatus 300 includes a backlight unit 200 for providing light and a display panel 100 for forming an image using the light from the backlight unit 200.

The backlight unit 200 includes a light source 210 and a light guide plate 230 for guiding light emitted from the light source toward the display panel 100. In the drawing, although the light source 210 is illustrated as a photometric type disposed on the side of the light guide plate 230, the light source 210 may be configured as a direct type provided with a light source on a lower front surface of the display panel 100. Generally, a metering type is adopted for a small display device and a direct type is adopted for a large display device. An optical sheet layer 250 including a plurality of layers may be further provided between the light guide plate 230 and the display panel 100 to improve light efficiency. For example, a diffuser plate for diffusing light, a prism sheet for correcting a propagation path of light, a bright enhancement film (BEF) for improving the direction of directing light passing through the prism sheet toward the display panel, and the like. It may be provided.

The display panel 100 controls the transmittance of incident light for each subpixel to form a color image. The display panel 100 of the present invention implements a reflection mode for reflecting incident light L _R according to a region where light is incident and displaying a image and a transmission mode for transmitting incident light L _T and displaying an image. Same as one. That is, the light L _T illuminated by the backlight unit 200 passes through the liquid crystal layer 130 in the transmission areas Ta, Tb, and Tc to form an image, and the external light L _R is the reflection area Ra. The liquid crystal layer 130 is returned from Rb and Rc to form an image. In particular, the external light L _R is diffracted and reflected in the first, second, or third CGH layers 140a, 140b, 140c, and the first, second, or third CGH layers 140a, 140b, 140c have a front brightness and A computer-generated hologram designed to have a predetermined light output distribution in consideration of viewing angle and wavelength characteristics provides an image of good quality even in the reflection mode. In addition, since external light is used as light for forming an image, the screen is well displayed even in bright places with sunlight or external lighting. Although the display device in the described embodiment has been described as a single-sided display device having a backlight unit, it is possible to be applied to a double-sided display device. That is, when the front light unit is provided on the front surface of the display panel and configured such that the direction in which the image is formed in the transmissive mode and the direction in which the image is formed in the reflective mode are opposite to each other, it may be used as a double-sided display device. In addition, not only the transmission mode and the reflection mode are used at the same time, but also a mode for forming an image using only external light and a mode for forming an image using both external light and internal light according to the brightness of external light. It is also possible to apply. Such a display panel and a display device employing the present invention have been described with reference to the embodiments shown in the drawings for clarity, but these are merely exemplary and various modifications and equivalents from those skilled in the art can be obtained. It will be appreciated that other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the appended claims.

1 is a view showing a schematic configuration of a display panel according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a computer-generated hologram formed in a reflective area of the display panel of FIG. 1.

FIG. 3 is a conceptual diagram for explaining roughly predicting the size of urea cells forming a pattern of a CGH unit block.

4 is a conceptual diagram for explaining and predicting roughly the pitch in which the CGH unit blocks are arranged.

5 is a micrograph image of a computer generated hologram made in accordance with an embodiment of the present invention.

6 illustrates various types of CGH unit blocks designed according to an embodiment of the invention.

7 shows a schematic structure of a display device according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100 ... display panel 110 ... lower polarizer

120 ... Lower transparent substrate 130 ... Liquid crystal layer

140 Support layer 150a, 150b, 150c ... First, second, third CGH layer

160 ... color filter 180 ... top transparent substrate

190 ... Upper Polarizer 200 ... Backlight Unit

210 Light source 230 Light guide plate

250 ... optical sheet layer 300 ... display unit

Claims (12)

A color filter in which pixels consisting of a plurality of sub pixels transmitting light of different wavelength bands are repeatedly arranged two-dimensionally; A transmittance of incident light is controlled by the sub-pixel unit by electrical control, and a region corresponding to the sub-pixels includes a liquid crystal layer comprising a transmission region and a reflection region; And a computer-generated hologram in the reflective area. The method of claim 1, The computer-generated hologram is a display panel characterized in that the unit blocks consisting of a diffraction pattern formed by the element cells are arranged repeatedly. The method of claim 2, And the arrangement pitch of the unit blocks and the shape of the pattern formed by the element cells according to the wavelength band of the light transmitted from the corresponding sub-pixel are different in the reflection area. The method of claim 2, The size of the element cells is a display panel, characterized in that more than 0.5㎛ ² . The method of claim 2, And a pitch in which the unit blocks are arranged is in a range of 5 μm to 20 μm. The method according to any one of claims 1 to 5, And the plurality of sub pixels are sub pixels transmitting red light, green light, and blue light, respectively. A backlight unit for illuminating light; The transmittance of incident light is adjusted in units of the sub-pixels by a color filter in which pixels consisting of a plurality of sub-pixels transmitting light of different wavelength bands are repeatedly arranged two-dimensionally and electrically controlled, and an area corresponding to the sub-pixels It includes; a display panel having a liquid crystal layer consisting of a transmission area and a reflection area, And a computer-generated hologram in the reflective area. The method of claim 7, wherein The computer-generated hologram is a display device characterized in that the unit blocks consisting of a diffraction pattern formed by the element cells are arranged repeatedly. The method of claim 8, And the arrangement pitch of the unit blocks and the pattern of patterns formed by the element cells according to the wavelength band of the light transmitted from the corresponding sub-pixel are different in the reflection area. The method of claim 8, Display element, characterized in that the size of the element cells is 0.5㎛ ² or more. The method of claim 8, Display unit, characterized in that the pitch in which the unit blocks are arranged in a range of 5㎛ 20㎛. The method according to any one of claims 7 to 11, And the plurality of sub-pixels are sub-pixels transmitting red light, green light, and blue light, respectively.

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