KR101749748B1 - Transparent Liquid Crystal Display Device Having High Brightness - Google Patents

Abstract

The present invention relates to a transparent liquid crystal display device. A transparent liquid crystal display according to the present invention includes: a liquid crystal panel; A first polarizer disposed on a front surface of the liquid crystal panel; A first optical film disposed between a front surface of the liquid crystal panel and the first polarizing plate; A light guide plate disposed directly opposite to the back surface of the liquid crystal panel; A linearly polarized light source disposed on one side of the light guide plate; And a second optical film disposed directly facing the back surface of the light guide plate. The present invention can provide a high luminance transparent liquid crystal display device having a wide viewing angle and a fast response speed.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a transparent high-

The present invention relates to a transparent liquid crystal display device. In particular, the present invention relates to a high-luminance liquid crystal display device that maintains the same state as a transparent glass during non-operation but operates in a normally black mode during operation.

BACKGROUND ART [0002] Liquid crystal display devices are becoming increasingly widespread due to features such as light weight, thinness, and low power consumption driving. The liquid crystal display device is used as a portable computer such as a notebook PC, an office automation device, an audio / video device, and an indoor / outdoor advertisement display device. Transmittive liquid crystal display devices, which occupy the majority of liquid crystal display devices, control an electric field applied to the liquid crystal layer to modulate light incident from the backlight unit using external light, thereby displaying an image.

BACKGROUND ART [0002] A liquid crystal display device has been applied to various purposes as a typical flat panel display device. The liquid crystal display device uses polarized light and can be applied in various applications. In addition, since it basically implements an image by adjusting the amount of light passing through the transparent substrate, it has various applications in which it functions as a glass when not in use and is used as a display device only when it is used.

FIG. 1 is a perspective view showing the structure of a transparent liquid crystal display device which has recently been spotlighted. The transparent liquid crystal display device includes a liquid crystal display panel (LCDP), a light guide plate (LG), and a light source (LS).

The liquid crystal display panel (LCDP) includes two polarizing plates arranged so that their light transmission axes are orthogonal to each other and a liquid crystal panel (LCP) interposed therebetween. The liquid crystal panel LCP includes an upper substrate SU, a lower substrate SL, and a liquid crystal layer LC interposed therebetween. An upper polarizer PU and a lower polarizer PL are attached to the upper and lower portions of the liquid crystal panel LCP, respectively. Although not shown in the drawings, the upper substrate SU and the lower substrate SL may be formed with wirings and black matrixes defining pixel regions arranged in a matrix manner, and common electrodes for driving the liquid crystal layer LC, Electrode. In addition, it may include a color filter for implementing color. An upper polarizer PU is attached to the front surface of the upper substrate SU and a lower polarizer PL is attached to the rear surface of the lower substrate SL. The light transmission axes of the upper polarizer PU and the lower polarizer PL should be arranged so as to be orthogonal to each other so that a complete black gradation can be realized when black is expressed. In order to implement a transparent liquid crystal display device, the liquid crystal display panel (LCDP) should be in a transparent state when not in use. Therefore, the liquid crystal display panel (LCDP) must operate in a normally white (NW) mode.

A light guide plate (LG) and a light source (LS) are disposed under the liquid crystal display panel (LCDP). The light source LS is disposed on one side of the light guide plate LG and irradiates light into the light guide plate LG. The light guide plate LG diffuses the light incident from the side to the entire area inside the light guide plate LG, and refracts the light to the front surface, that is, the surface on which the liquid crystal display panel (LCDP) is located. To this end, a reflection pattern is formed on the back surface of the light guide plate LG. In particular, since the light guide plate LG must also ensure transparency, it is preferable that the light guide plate LG be a prism shape, a lenticular shape, or a pattern in which the microlens shape is engraved on the back surface.

When the transparent liquid crystal display device is not used, the liquid crystal display device itself is transparent like a glass. In addition, when power is applied and used as a display device, an image can be realized. Since the liquid crystal display device includes a liquid crystal display panel in which liquid crystal cells are interposed between two polarizing plates whose light transmission axes are orthogonal to each other, the liquid crystal display panel can be used as a transparent liquid crystal display device when it operates in a normally white mode. In the case of a liquid crystal display panel operating in the normally white mode, the liquid crystal cell is preferably driven by a twisted nematic (TN) method. In the case of a liquid crystal display panel driven in the TN mode, there is a limitation in applying to a display device such as a television in which a viewing angle is narrow and a response time of the liquid crystal is slow, and a user views an image moving.

On the other hand, although an IPS driving method (a type of a horizontal field driving method) having a wide viewing angle and a fast response time of a liquid crystal can be implemented in a normally white mode, It is common to implement. The normally black mode is a state in which light can not pass through the liquid crystal display panel in a normal state without using the liquid crystal display device, so that it has not been proposed to be implemented as a transparent liquid crystal display device.

Further, unlike a general liquid crystal display device, a transparent liquid crystal display device must have a structure in which a backlight unit secures transparency. Therefore, it has a structure in which all of the optical sheets for improving brightness used in a general liquid crystal display device are excluded. As a result, the transparent liquid crystal display device has a problem that luminance is remarkably lowered as compared with a general liquid crystal display device. That is, the problem of improving the luminance in the transparent liquid crystal display device implemented in the normally black mode is also one of the important problems.

It is an object of the present invention to provide a transparent liquid crystal display device using a liquid crystal display panel which operates in a normally black mode, which is designed to overcome the limitations of the conventional transparent liquid crystal display device. It is another object of the present invention to provide a transparent liquid crystal display device using a liquid crystal display panel operating in a normally black mode having a high luminance.

In order to achieve the object of the present invention, a transparent liquid crystal display according to the present invention includes: a liquid crystal panel; A first polarizer disposed on a front surface of the liquid crystal panel; A first optical film disposed between a front surface of the liquid crystal panel and the first polarizing plate; A light guide plate disposed directly opposite to the back surface of the liquid crystal panel; A linearly polarized light source disposed on one side of the light guide plate; And a second optical film disposed directly facing the back surface of the light guide plate.

And the polarization axis of the linearly polarized light source is orthogonal to the light transmission axis of the first polarizing plate.

And the light transmission axis of the first polarizing plate and the light transmission axis of the first optical film are parallel to each other.

And the light transmission axis of the first optical film and the light transmission axis of the second optical film are parallel to each other.

The light transmission axis of the first polarizing plate, the light transmission axis of the first optical film, and the light transmission axis of the second optical film are parallel to each other.

And a low reflection layer formed on the back surface of the liquid crystal panel.

The liquid crystal panel may include: a first substrate; A second substrate facing the first substrate; And a liquid crystal layer interposed between the first substrate and the second substrate.

The first optical film and the second optical film have a structure in which a plurality of transparent optical sheets are laminated.

The polarized light source includes: a light source; And a side polarizer interposed between the light source and the light guide plate.

A transparent liquid crystal display according to the present invention includes a liquid crystal display panel operating in a normally black mode. Therefore, a transparent liquid crystal display device can be realized using a liquid crystal display panel having a wide viewing angle and a high response speed such as IPS. Further, the transparent liquid crystal display device according to the present invention has a structure for improving polarization efficiency and luminance while maintaining transparency. Therefore, the present invention can provide a high luminance transparent liquid crystal display device having a wide viewing angle and a fast response speed.

1 is a perspective view showing a structure of a transparent liquid crystal display device;
2 is a perspective view illustrating a structure of a transparent liquid crystal display device using a liquid crystal display panel operating in a normally black mode according to Embodiment 1 of the present invention.
3 is a cross-sectional view showing the structure and operating state of the transparent liquid crystal display device according to FIG.
4 is a cross-sectional view showing the structure of an integrated top sheet combining multiple optical sheets and an upper polarizer plate applied to a transparent liquid crystal display according to the present invention.
5 is a cross-sectional view illustrating the structure and operation state of a transparent liquid crystal display device using a liquid crystal display panel operating in a normally black mode according to a second embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to FIGS. 2 to 5 attached hereto. 2 is a view illustrating a structure of a transparent liquid crystal display device using a liquid crystal display panel operating in a normally black mode according to a first embodiment of the present invention.

2, the transparent liquid crystal display according to the present invention includes a liquid crystal display panel 100, a liquid crystal display panel 100, a light guide plate LG, a polarizing source PLS, and a lower multilayer optical sheet ML .

The liquid crystal display panel 100 includes a liquid crystal panel (LCP) and an upper polarizer PU attached to the front surface. The liquid crystal panel LCP includes an upper substrate SU, a lower substrate SL, and a liquid crystal layer LC interposed therebetween. Although not shown in the drawings, the upper substrate SU and the lower substrate SL may be formed with wirings and black matrixes defining pixel regions arranged in a matrix manner, and common electrodes for driving the liquid crystal layer LC, Electrode. In addition, it may include a color filter for implementing color.

A light guide plate LG and a polarization source PLS are positioned under the liquid crystal display panel 100. The polarization source PLS is disposed on one side of the light guide plate LG and irradiates linearly polarized light into the light guide plate LG. To this end, the polarization source PLS may include a light source LS such as an LED and a side polarizer PS for linearly polarizing the light emitted from the light source LS. In particular, the side polarizing plate PS is preferably arranged so as to linearly polarize the light emitted from the light source LS in a direction orthogonal to the light transmission axis of the upper polarizer PU. This is to realize a full black gradation when the black gradation is to be expressed. The light guide plate LG diffuses the linearly polarized light incident from the side to the entire area inside the light guide plate LG and refracts the light to the front surface, that is, the surface on which the liquid crystal display panel 100 is located. To this end, a reflection pattern is formed on the back surface of the light guide plate LG. In particular, since the light guide plate LG must also ensure transparency, it is preferable that the light guide plate LG be a prism shape, a lenticular shape, or a pattern in which the microlens shape is engraved on the back surface.

The transparent liquid crystal display device according to the first embodiment of the present invention having the above-described structure is not in a state in which the liquid crystal panel (LCP) is interposed between two polarizing plates having optical axes orthogonal to each other as compared with the conventional liquid crystal display device . Therefore, whether the liquid crystal panel LCP is in operation or not, the light incident in the back direction of the liquid crystal panel LCP is transparent to be transmitted to the front side. However, in the case where the light incident on the light guide plate LG is incident on the linear polarized light having the optical axis of the upper polarizer PU orthogonally, the black color gradation PU, which does not transmit the upper polarizer PU, Can be implemented. That is, the liquid crystal display device having the structure according to the first embodiment of the present invention can be used as a transparent liquid crystal display device even in a normally white mode as well as a normally black mode.

Further, in the case of a transparent liquid crystal display device, the brightness of the backlight is raised on the light guide plate LG, and the light path is adjusted so that the light dispersed by the light guide plate LG is incident on the incident surface of the liquid crystal panel The optical sheets are excluded. To compensate for this, the transparent liquid crystal display according to the first embodiment of the present invention further includes an upper optical film (MU) for increasing the brightness of the liquid crystal panel (LCP). The upper optical film (MU) is preferably a multilayer optical film in which a plurality of transparent optical films are laminated. The multilayer optical film has a linearly polarized light property. Therefore, it is preferable that the light transmission axis of the upper optical film MU constituted of the multilayer optical film is set parallel to the light transmission axis of the upper polarizer PU.

Hereinafter, the case of utilizing the liquid crystal display device having the structure according to FIG. 2 as a transparent liquid crystal display device in the normally black mode will be described in more detail. 2, in order to realize a normally black mode for providing images of better quality than the normally white mode in the liquid crystal display device having the structure of FIG. 2, the optical axis of the light linearly polarized by the polarizing source PLS is shifted from the light of the upper polarizer PU It shall be perpendicular to the transmission axis. The liquid crystal panel LCP is preferably a horizontal electric field system in which the initial alignment state of the liquid crystal layer LC is oriented parallel to or perpendicular to the light transmission axis of the upper polarizer PU. For example, the optical axis that is linearly polarized by the side polarizing plate PS may be parallel to the X axis (0 degrees), and the optical transmission axis of the upper polarizing plate PU may be parallel to the Y axis (90 degrees). The liquid crystal layer LC can be oriented in the 0 degree direction parallel to the X axis (or in the 90 degree direction parallel to the Y axis).

Hereinafter, the operating state of the transparent liquid crystal display device according to the first embodiment will be described with reference to FIG. In Fig. 3, arrows indicate paths of light. First, operation in the normal state in which the light source LS is turned on to use the liquid crystal display panel 100 but no power is applied to the liquid crystal panel LCP is as follows. Light emitted from the light source LS is linearly polarized in the X-axis (0 degree) direction by the side polarizing plate PS (region 1). The light which is linearly polarized in the 0 degree direction is uniformly dispersed over the entire area of the LGP, is totally reflected on the lower surface, and emitted outside the LGP on the upper surface.

In addition, some light leaks to the outside through the lower surface of the LGP (region 2). In the transparent liquid crystal display device, a reflection plate can not be provided on the lower surface of the light guide plate LG. Therefore, it is difficult to secure the brightness due to light leaked through the lower surface of the light guide plate LG. In order to recycle the leaked light, the present embodiment further comprises a lower optical film ML having a light transmission axis in a direction orthogonal to the optical axis of linearly polarized light. In particular, since the lower optical film ML must maintain the transmittance of the transparent liquid crystal display device, it is preferable that the lower optical film ML is an optical film in which a transparent multilayer film is laminated. That is, the light leaking to the lower surface area (2) of the light guide plate (LG) is linearly polarized light in the 0 degree direction and is reflected by the light guide plate (LG) by the lower optical film (ML) and then emitted to the upper part of the light guide plate (LG).

Light emitted to the upper surface of the light guide plate LG is linearly polarized in the 0-degree direction until it is incident on the liquid crystal panel LCP (region 3). In the normal state in which no electric field is applied to the liquid crystal panel LCP, the liquid crystal layers LC are arranged in the 0-degree direction in the initial alignment state. That is, in parallel with the line polarization axis of the light in the region?. Therefore, the linearly polarized light transmitted through the liquid crystal panel LCP maintains a state in which the retardation does not occur. That is, the light in the region? Keeps the linear polarization state in the 0 degree direction. Since the optical axes of the upper optical film MU and the upper polarizer PU are arranged in the 90 degree direction, the linearly polarized light in the 0 degree direction present in the current region 4 can not transmit the upper polarizer PU. That is, the liquid crystal display panel 100 operates in the normally black mode in which the black gradation is realized in the normal state.

Next, the operation in the state where the light source LS is turned on to use the liquid crystal display panel 100 and power is applied to the liquid crystal panel LCP to implement an image is as follows. The state where the light is emitted from the light source LS and is linearly polarized by the side polarizing plate PS is the same as described above. That is, the light is polarized in the 0 degree direction in the region 1 (inside the LG). The light of the light source polarized in the 0 degree direction leaking from the light guide plate LG in the region 2 is reflected by the lower optical film ML and returned to the light guide plate LG.

Light emitted to the upper surface of the light guide plate LG is linearly polarized in the 0-degree direction until it is incident on the liquid crystal panel LCP (region 3). When a horizontal electric field is applied to the liquid crystal panel LCP and the liquid crystal layer LC is oriented in the direction of 45 degrees, the light linearly polarized in the 0 degree direction passes through the liquid crystal molecules of the liquid crystal layer LC inclined by 45 degrees, A phase difference is generated by anisotropy. As a result, the light passing through the liquid crystal panel LCP becomes (④) elliptically polarized state. The light in the elliptically polarized state in the region ④ is linearly polarized in parallel with the upper optical film MU and the upper polarizer PU and exits to the front portion (region ⑤) of the liquid crystal display panel 100. At this time, part of the light orthogonal to the optical axes of the upper optical film MU and the upper polarizing plate PU in the elliptically polarized state of the region 4 is returned to the liquid crystal panel LCP. As described above, the light reflected by the upper optical film MU is polarized in the 0-degree direction and can leak toward the back surface of the liquid crystal display device through the liquid crystal panel LCP and the light guide plate LG. However, since the optical axis of the lower optical film ML is oriented at 90 degrees, the light that can be reflected by the upper optical film MU and leaked can be utilized again as a backlight by the lower optical film ML.

If there is no upper optical film MU, the zero-degree direction component of the elliptically polarized light in the region 4 is absorbed by the upper polarizer PU, and only the 90-degree direction component is transmitted through the upper polarizer PU. However, since the upper optical film MU having the same optical axis as that of the upper polarizer MU is present, light to be absorbed by the upper polarizer PU and to be lost can be reflected to the back surface in advance and reproduced by the lower optical film ML , The light luminance can be further increased. That is, the light transmission axes of the upper optical film MU and the lower optical film ML are arranged parallel to each other, and the linearly polarized light emitted from the linearly polarized light source PLS is orthogonal to the upper and lower optical films MU and ML Therefore, the leaked light can be recycled in the past. As a result of the experiment, it has been found that the luminance of the transparent liquid crystal display device including the upper optical film (MU) is improved by about 7% or more compared with the case of the transparent liquid crystal display device including only the lower optical film ML I could.

As described above, the transparent liquid crystal display device according to the first embodiment of the present invention operates in a normally black mode, while being a transparent liquid crystal display device, using light that is linearly polarized by a polarizing source (PLS). Therefore, it is possible to realize a higher quality image than normally white. Further, the lower optical film having the multilayer optical film laminated thereon can be used to recycle the light leaked to the back surface, thereby improving the light luminance. The upper optical film having the multilayer optical film laminated thereon can be further improved in light brightness by returning light that is absorbed and leaked by the upper polarizer to the back surface and is reflected back to the lower optical film and reused.

4 is a cross-sectional view showing the structure of an integrated top sheet combining multiple optical sheets and an upper polarizer applied to a transparent liquid crystal display according to the present invention. It is preferable that the upper polarizer plate PU and the upper optical film MU, which are disposed on the front surface of the liquid crystal panel (LCP) in Embodiment 1 of the present invention, have a structure as shown in FIG. That is, the upper polarizer PU is attached with TAC on the front and rear sides, respectively, and the upper optical film (MU) is attached to the lower side of the rear TAC with the PSA. It is preferable that PSA, which is an adhesive, is applied to the back surface of the upper optical film MU so that the upper polarizer PU and the upper optical film MU can be attached to the liquid crystal panel LCP.

In the second embodiment of the present invention, a structure capable of further improving the brightness of the transparent liquid crystal display according to the present invention is proposed. 5 is a cross-sectional view illustrating the structure and operating state of a transparent liquid crystal display device using a liquid crystal display panel operating in a normally black mode according to a second embodiment of the present invention.

Referring to FIG. 5, the structure of the transparent liquid crystal display device according to the second embodiment is basically the same as that of the transparent liquid crystal display device according to the first embodiment. Therefore, the same components and detailed descriptions are omitted. The difference is the structure of the liquid crystal panel 200. The liquid crystal panel 200 according to the second embodiment includes a liquid crystal panel LCP having an upper substrate SU, a lower substrate SL, a liquid crystal layer LC interposed therebetween, (ARC). ≪ / RTI > The low reflection layer (ARC) serves to reduce the amount of total reflection of the backlight emitted from the light guide plate LG on the surface of the lower substrate SL of the liquid crystal panel 200. To this end, the low emission layer (ARC) can be formed by coating a low reflective material with Anti Reflective Coating. Although not shown in the drawings, the upper substrate SU and the lower substrate SL may be formed with wirings and black matrixes defining pixel regions arranged in a matrix manner, and common electrodes for driving the liquid crystal layer LC, Electrode. In addition, it may include a color filter for implementing color.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the 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.

LCDP, 100: liquid crystal display panel LCP, 200: liquid crystal panel
SU: upper substrate SL: lower substrate
LC: liquid crystal layer PS: side polarizer plate
PU: Upper polarizer PL: Lower polarizer
LG: Light guide plate LS: Light source
PLS: linear light source MU: upper optical film
ML: lower optical film ARC: low reflection layer

Claims (9)

A liquid crystal panel;
A first polarizer disposed on a front surface of the liquid crystal panel;
A first optical film disposed between a front surface of the liquid crystal panel and the first polarizing plate;
A light guide plate disposed directly opposite to the back surface of the liquid crystal panel;
A linearly polarized light source disposed on one side of the light guide plate; And
And a second optical film disposed directly opposite to a back surface of the light guide plate,
The polarization axis of the linearly polarized light source is orthogonal to the light transmission axis of the first polarizer plate,
Wherein the light transmission axis of the first polarizer, the light transmission axis of the first optical film, and the light transmission axis of the second optical film are parallel to each other.
delete delete delete delete The method according to claim 1,
And a low reflection layer formed on a back surface of the liquid crystal panel.
The liquid crystal display device according to claim 1,
A first substrate;
A second substrate facing the first substrate; And
And a liquid crystal layer interposed between the first substrate and the second substrate.
The method according to claim 1,
Wherein the first optical film and the second optical film have a structure in which a plurality of transparent optical sheets are laminated.
The apparatus according to claim 1,
Light source; And
And a side polarizer interposed between the light source and the light guide plate.

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