JP3293167B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device having a screen concealing function that allows only a specific viewer to view an image.

A liquid crystal display device can be made thinner and lighter than a CRT or the like and consumes less power because of its low power consumption, such as a book-type personal computer and a word processor. Widely used as a display.

When the information processing apparatus is installed in a dedicated space, the number of people who see the screen is limited and the information is not seen by an unspecified number of people. It may be operated in a space shared with an unspecified number of people, such as in a train or train.

[0004] In an apparatus used in a space shared with an unspecified number of people, it is desirable that a displayed image is visible only to a specific viewer. Therefore, realization of a liquid crystal display device having a screen concealing function that allows only a specific viewer to view an image is demanded.

[0005]

2. Description of the Related Art FIG. 5 is a schematic view showing a conventional liquid crystal display device with a screen concealment function. A conventional display device having a screen concealing function comprises a liquid crystal display device main body 1 and a polarizing plate 2 which can be mounted on a human body as shown in FIG. And the backlight 5.

The liquid crystal cell 3 is composed of two glass panels 31 and 32 facing each other with a predetermined gap therebetween and liquid crystal molecules 33 sealed between them, and is formed inside the glass panels 31 and 32, respectively. The plurality of transparent electrodes 34 and 35 are configured to be orthogonal to each other.

In the light emitted from the backlight 5 in the main body 1 of the liquid crystal display device, a component that matches the polarization direction of the polarizing plate 4, for example, a polarization component in the vertical direction if the polarization direction of the polarizing plate 4 is the vertical direction. Only the light passes through the polarizing plate 4 and enters the liquid crystal cell 3.

The voltage is applied to the liquid crystal cell 3 by selecting the transparent electrodes 34 and 35 corresponding to the display image, and the polarized component transmitted through the polarizing plate 4 is not applied to the transparent electrodes 34 and 35. In the region, the direction turns 90 degrees while passing through the liquid crystal cell 3 as shown in FIG.

On the other hand, in a region where a voltage is applied to the transparent electrodes 34 and 35, the polarized light component is transmitted without rotating as shown in FIG. As a result, an image corresponding to the electrode selected by the polarized light component whose direction is shifted by 90 degrees is displayed on the image display surface of the liquid crystal cell 3.

It is impossible to distinguish the polarized light component in the vertical direction and the polarized light component in the horizontal direction directly with the naked eye without passing through a polarizing plate, and the image is displayed by a polarized light component whose direction is shifted by 90 degrees on the image display surface of the liquid crystal cell 3. The resulting image cannot be read directly by the naked eye.

On the other hand, the polarization component in the vertical direction and the polarization component in the horizontal direction can be discriminated by viewing the image through the polarizing plate 2. For example, a viewer wearing the polarizing plate 2 like spectacles can use the liquid crystal cell 3. The image displayed on the image display surface can be read.

[0012]

However, polarizers that can be worn on the human body are used for extremely general purposes such as OA glasses and sunglasses that block the incidence of reflected light, and are displayed by conventional liquid crystal display devices. There is a problem that an image to be read can be read by passing through such a polarizing plate.

An object of the present invention is to provide a liquid crystal display device having a screen concealing function in which an image cannot be read even through a simple polarizing plate.

[0014]

FIG. 1 is a schematic view showing a main part of a liquid crystal display device according to the present invention. The same object is denoted by the same symbol throughout the drawings.

The object is to provide a liquid crystal display device in which a polarizing plate is not superimposed on an image display surface of a liquid crystal cell and a polarizing plate that can be mounted on a human body, and the polarizing plate that can display a display image of the liquid crystal cell on a human body. In a liquid crystal display device seen through, a quarter-wave plate is layered on a surface of a polarizing plate that can be worn on a human body and faces the liquid crystal display device main body, and the liquid crystal display device main body faces a backlight. A polarizing plate, a liquid crystal cell for normal image display, and a second polarizing plate are sequentially laminated, and a liquid crystal cell for confidential image display and a quarter wavelength are provided outside the second polarizing plate.
And a liquid crystal display device configured so that only one polarized light component of the light transmitted through the liquid crystal cell is transmitted through the polarizing plate that can be mounted on the human body. You.

[0016]

1 (a), the liquid crystal display device main body 7 comprises a liquid crystal cell 3, a polarizing plate 4 overlaid on the liquid crystal cell 3, and a backlight 5, and the liquid crystal cell 3 has an image display surface shown in FIG. As shown in the figure, an image composed of a polarization component in the vertical direction and a polarization component in the horizontal direction is displayed.

The front of the liquid crystal display device main body 7 has a 1/4
As shown in FIG. 1 (c), the polarization components whose directions are shifted by 90 degrees due to the attachment of the wave plate 9 are converted into circularly polarized lights having different rotation directions, so that an image which cannot be discriminated by the naked eye or through a simple polarizing plate is formed. Is done.

In FIG. 1 (a), a polarizing plate 6 which can be mounted on a human body has a 波長 wavelength plate 8
The circularly polarized light shown in FIG. 1C is returned to the vertical and horizontal polarization components corresponding to the rotation direction, and can be distinguished by the polarizing plate 6.

By mounting the quarter-wave plate on the opposing surfaces of the polarizing plate that can be mounted on the human body and the main body of the liquid crystal display device in this way, a viewer wearing a normal polarizing plate can read. An image that cannot be displayed can be displayed on the main body of the liquid crystal display device.

That is, it is possible to realize a liquid crystal display device having a screen concealing function in which an image cannot be read even through a simple polarizing plate.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 2 is a schematic diagram showing an embodiment of the liquid crystal display device according to the present invention, FIG. 3 is a schematic diagram showing an operation when displaying a normal screen, and FIG. 4 is a schematic diagram showing an operation when displaying a secret screen. It is.

One embodiment of the liquid crystal display device according to the present invention comprises, as shown in FIG. 2, a liquid crystal display device main body 7 and a polarizing plate 6 which can be mounted on a human body. A 波長 wavelength plate 8 is overlaid on the surface facing the liquid crystal display main body 7.

The liquid crystal display device main body 7 has two types of liquid crystal cells, a liquid crystal cell 3a for displaying a normal image and a liquid crystal cell 3b for displaying a confidential image. The liquid crystal cells 3a for displaying a normal image have polarization directions orthogonal to each other. The first polarizing plate 4a and the second polarizing plate 4
It is arranged between b.

A backlight 5 is mounted on the outside of the first polarizing plate 4a mounted on the liquid crystal cell 3a for normal image display, and a quarter-wave plate 9 is mounted on the opposite surface. The attached liquid crystal cell 3b for displaying a confidential image is a second polarizing plate 4b.
It is layered outside.

Each of the liquid crystal cells 3a and 3b has liquid crystal molecules 33 sealed between glass panels 31 and 32 facing each other with a predetermined gap therebetween, and a plurality of liquid crystal cells formed inside the glass panels 31 and 32, respectively. Transparent electrodes 34 and 35 are configured to be orthogonal to each other.

The case of displaying a normal image that can be viewed by anyone on the main body 7 of the liquid crystal display will be described in more detail with reference to FIG. 3. For example, if the polarization direction of the first polarizing plate 4a is set to the vertical direction, FIG. As described above, the vertical polarization component enters the liquid crystal cell 3a.

The liquid crystal cell 3a for normal image display is shown in FIG.
When a voltage is applied to the transparent electrodes 34 and 35 by inputting an image signal indicated by diagonal lines to the transparent electrode 34 and 35, the polarized light component rotates 90 degrees in a region where no voltage is applied when transmitting the liquid crystal cell 3a, but in a region where the voltage is applied. Do not turn.

The polarized light component rotated by 90 degrees while passing through the liquid crystal cell 3a passes through the second polarizing plate 4b, so that the portion looks bright, but the polarized light component that does not rotate while passing through the liquid crystal cell 3a is the second component. 3 cannot be transmitted through the polarizing plate 4b of FIG.
The shadow becomes as shown in (c).

During normal screen display, the circuit connected to the confidential image display liquid crystal cell 3b is cut off, and no voltage is applied to all the electrodes. Therefore, the light passing through the second polarizing plate 4b is transmitted by the liquid crystal cell 3b for displaying a confidential image as shown in FIG.
Turn 90 degrees as shown in (d).

The polarized light component transmitted through the liquid crystal cell 3b for displaying a confidential image is converted into circularly polarized light by the quarter-wave plate 9 attached to the outside, and as shown in FIG. The image is displayed with the converted light and shadow, so that anyone can easily read the image.

Similarly, the case where a screen to be concealed is displayed on the liquid crystal display device main body 7 will be described in more detail with reference to FIG. 4. For example, if the polarization direction of the first polarizing plate 4a is set to the vertical direction, FIG. As described above, the vertical polarization component enters the liquid crystal cell 3a.

In this case, a liquid crystal cell 3a for normal image display is used.
Is disconnected, and no voltage is applied to all the electrodes. Accordingly, the polarized light component incident on the liquid crystal cell 3a rotates 90 degrees as shown in FIG. 4A and transmits through the liquid crystal cell 3a and the second polarizing plate 4b.

The liquid crystal cell 3b for displaying a secret image is shown in FIG.
When a voltage is applied to the transparent electrodes 34 and 35 by inputting an image signal indicated by oblique lines to the transparent electrodes 34 and 35, the polarized light component rotates 90 degrees in a region where no voltage is applied when passing through the liquid crystal cell 3b, but in a region where the voltage is applied. Do not turn.

As a result, as shown in FIG. 4 (c), an image is formed on the surface of the liquid crystal cell 3b consisting of a polarized light component rotated by 90 degrees and a polarized light component not rotated by 90 degrees. The confidential image which cannot be distinguished because the image cannot be displayed is displayed on the liquid crystal cell 3b.

The polarized light component transmitted through the liquid crystal cell 3b for confidential image display is converted into circularly polarized light having different rotation directions by a quarter wave plate 9 attached to the outside as shown in FIG. An image that cannot be distinguished by a naked eye or a mere polarizing plate is formed.

When such an image is viewed through a polarizing plate 6 in which a quarter-wave plate 8 is laminated on the surface facing the liquid crystal display device main body 7, the circularly polarized light is vertical and horizontal corresponding to the rotation direction, respectively. The polarization component is returned to the polarization component in the direction, and the polarization component can be determined by the polarizing plate 6.

For example, if the polarizing direction of the polarizing plate 6 that can be mounted on a human body is the vertical direction, only the polarized light component in the vertical direction is transmitted through the polarizing plate 6, and the polarized light component in the horizontal direction cannot be transmitted through the polarizing plate 6, so that the shadowing is not possible. As a result, an image composed of light and shadow is formed as shown in FIG.

Conversely, if the polarization direction of the polarizing plate 6 that can be worn on the human body is horizontal, only the horizontal polarization component passes through the polarizing plate 6 and the vertical polarization component cannot pass through the polarizing plate 6. As a shadow, an image composed of light and a shadow is formed as shown in FIG.

That is, by selecting a liquid crystal cell when inputting an image signal, a normal image and a concealed image that can be viewed by anyone can be displayed, and the displayed concealed image can be read without passing through a dedicated polarizing plate. It is possible to configure a liquid crystal display device that cannot be used.

As described above, by mounting the quarter-wave plate on the opposing surfaces of the polarizing plate that can be mounted on the human body and the main body of the liquid crystal display device, a viewer wearing a normal polarizing plate can read. An image that cannot be displayed can be displayed on the main body of the liquid crystal display device. That is, it is possible to realize a liquid crystal display device having a screen concealing function in which an image cannot be read even through a simple polarizing plate.

[0041]

As described above, according to the present invention, there is provided a liquid crystal display device having an advanced screen concealing function in which an image cannot be read through a mere polarizing plate such as OA glasses or sunglasses which are usually used. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a main part of a liquid crystal display device according to the present invention.

FIG. 2 is a schematic view showing one embodiment of a liquid crystal display device according to the present invention.

FIG. 3 is a schematic diagram showing an operation when a normal screen is displayed.

FIG. 4 is a schematic diagram showing an operation when a secret screen is displayed.

FIG. 5 is a schematic view showing a conventional liquid crystal display device with a screen concealment function.

[Explanation of symbols]

 3, 3a, 3b Liquid crystal cell 4, 4a, 4b, 6 Polarizer 5 Backlight 7 Liquid crystal display main body 8, 9 Quarter wave plate 31, 32 Glass panel 33 Liquid crystal molecule 34, 35 Transparent electrode

Continuation of the front page (56) References JP-A-63-44686 (JP, A) JP-A-1-220997 (JP, A) JP-A-62-191820 (JP, A) JP-A-2-71821 (JP) , U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/1335 510 G09F 9/35 345

Claims (2)

(57) [Claims] 1. A liquid crystal display device comprising: a liquid crystal display main body in which a polarizing plate is not overlaid on an image display surface of a liquid crystal cell; and a polarizing plate mountable on a human body, wherein the display image of the liquid crystal cell can be mounted on a human body. In the liquid crystal display device seen through, a quarter-wave plate is layered on a surface of the polarizing plate that can be mounted on a human body and faces the liquid crystal display device main body, and the liquid crystal display device main body faces a backlight. The polarizing plate, the liquid crystal cell for normal image display, and the second polarizing plate are sequentially laminated, and the liquid crystal cell for confidential image display and the quarter-wave plate are layered on the outside of the second polarizing plate. A liquid crystal display device, wherein, of the light transmitted through the liquid crystal cell, only light of one polarization component is transmitted through a polarizing plate that can be mounted on the human body. 2. A liquid crystal cell for displaying a confidential image outside a second polarizing plate, wherein a first polarizing plate facing a backlight, the liquid crystal cell for displaying a normal image, and a second polarizing plate are sequentially arranged. And a quarter-wave plate are sequentially arranged.