JP2008111927A - Liquid crystal display device and display system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the quality of an image in a liquid crystal display device of a reflective projection system. <P>SOLUTION: A retardation film 24 is disposed in the outside of a polarizer 22 of a polarizing plate 12 disposed in a light exiting side of a liquid crystal cell 11, the retardation film 24 showing a retardation value of λ/2 which is a half of the wavelength λ of the exiting light and having an angle of (π+x)/2 or x/2 between the slow phase axis 201 and a horizontal side of the liquid crystal cell 11 with respect to an angle x between the transmission axis 200 of the polarizer 22 and the horizontal side of the liquid crystal cell 11. Thus, the polarization direction of the light transmitting through the polarizer 22 is controlled to be horizontal, thereby obtaining the image high in reflection efficiency. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device that reflects and projects an emitted image.

  In recent years, liquid crystal display devices are used in various fields. In particular, the demand for car navigation is greatly increasing, and an apparatus for projecting an image on a windshield called a head up display (HUD) is increasing.

The HUD reflects an image emitted from a liquid crystal display device by a reflection unit and projects it on a windshield, and is used for a display such as a speedometer. Recently, a high level of display image performance such as brightness and color purity is required to display various information. Patent Document 1 describes a technique related to HUD.
JP 2003-50373 A

  In-vehicle liquid crystal display devices generally use the TN (Twisted Nematic) mode, but the TN mode rubs the alignment film at 45 ° to one side of the display screen to obtain a symmetrical viewing angle. To do. The transmission axis of the polarizing plate is generally 45 ° or 135 ° in accordance with the rubbing direction.

  However, when the light emitted from a polarizing plate having a transmission axis of 45 ° or 135 ° is reflected and projected by the reflection unit, the reflection direction is poor because the direction of vibration of the emitted light is not horizontal, and only a dark image can be displayed. Has occurred.

  In order to make the oscillation direction of the emitted light horizontal, a method of changing the rubbing direction of the alignment film to 0 ° or 90 ° is conceivable. In this case, although the reflection efficiency is maximized, an asymmetrical image is transferred. As a result, there is a problem that the degree of blur differs between the left and right sides of the image.

  The present invention has been made in view of the above, and an object of the present invention is to provide a liquid crystal display device that displays a high-quality image even when reflected and projected.

  A liquid crystal display device according to a first aspect of the present invention includes a liquid crystal cell in which a liquid crystal layer is sandwiched between a pair of substrates, and a polarizing plate bonded to each of the pair of substrates. A liquid crystal display device that enters, transmits through a liquid crystal cell, and emits light from the other polarizing plate, and the polarizing plate disposed on the light emitting side includes a polarizer and a retardation film, The retardation film is arranged so that light transmitted through the polarizer is incident, and when the angle formed between the transmission axis of the polarizer and one side in the horizontal direction of the liquid crystal cell is x, the retardation phase of the retardation film is The angle between the axis and one side is x / 2 or (π + x) / 2, and the retardation value of the retardation film is half the wavelength of the emitted light.

  In the present invention, a retardation film is provided on the outside of the polarizer of the polarizing plate disposed on the output light side of the liquid crystal cell, and the slow axis of the retardation film and one side in the horizontal direction of the liquid crystal cell form. The angle is x / 2 or (π + x) / 2 where the angle formed by the transmission axis of the polarizer and the horizontal side of the liquid crystal cell is x / 2, and the retardation value of the retardation film is Since the polarization direction of the light transmitted through the polarizer can be made horizontal by being half λ / 2 of the outgoing light wavelength λ, an image with good reflection efficiency can be obtained.

  In the above liquid crystal display device, the liquid crystal cell includes one pixel composed of RGB sub-pixels, and the retardation value of the retardation film is in the range of 250 to 300 nm. .

  In the present invention, in the case of using a liquid crystal cell for full-color display by RGB three colors, a display image having little influence on coloring is obtained by setting the retardation value of the retardation film to half of the wavelength of green light. Can do.

  In the liquid crystal display device, the liquid crystal cell includes one pixel composed of sub-pixels of two colors, and the retardation value of the retardation film is half of the average value of the wavelengths of the emitted light of the two colors. It is characterized by being.

  In the present invention, when a two-color liquid crystal cell is used, a display image with little influence on coloring is obtained by setting the retardation value of the retardation film to half the average value of the wavelengths of the light of the two colors. Can be obtained.

  In the liquid crystal display device, the liquid crystal cell is in a TN mode, and the rubbing direction of the alignment film disposed on each of the pair of substrates is within an angle range of 45 ± 5 ° with respect to one side in the horizontal direction of the liquid crystal cell. The other substrate is characterized by being twisted by 90 ° with the rubbing direction of the other substrate.

  In the present invention, the alignment film disposed on the liquid crystal layer side of the pair of substrates sandwiching the liquid crystal layer is subjected to rubbing treatment at 45 ± 5 ° with respect to one side in the horizontal direction of the liquid crystal cell, thereby being symmetrical. It is possible to obtain a viewing angle.

  A display system according to a second aspect of the present invention includes the above-described liquid crystal display device and a reflection unit that reflects light emitted from the liquid crystal display device and projects an image.

  According to the present invention, it is possible to provide a liquid crystal display device that displays a high-quality image even when reflected and projected.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram showing the configuration of the HUD in the present embodiment. As shown in the figure, the HUD includes a liquid crystal display device 1 and a reflection unit 2, and displays the image 4 on the windshield 3 by reflecting light incident on the liquid crystal display device 1 from the light source by the reflection unit 2. Is.

  The liquid crystal display device 1 includes two polarizing plates 12 and 13 so as to sandwich the liquid crystal cell 11, and has a display resolution of 640 × 480 with a diagonal length of 3 inches (about 7.6 cm). Yes. The liquid crystal cell 11 is a normally white 90-degree twisted TN mode, and a single pixel is formed by R, G, and B subpixels, thereby enabling full color display.

  The liquid crystal cell 11 has a structure in which the counter substrate 112 and the array substrate 113 sandwich the liquid crystal layer 111. An alignment film (not shown) for arranging liquid crystal molecules in a certain direction is disposed on the counter substrate 112 and the array substrate 113, and the alignment film is 135 ° and 45 ° with respect to one side in the horizontal direction of the liquid crystal cell 11. The rubbing direction between the counter substrate 112 and the array substrate 113 is twisted by 90 °. The transmission axes of the polarizing plates 12 and 13 are also 135 ° and 45 ° in accordance with the rubbing direction of the alignment film. The polarizing plate 12 arranged on the light emitting surface includes a retardation film 24 having a retardation value of 275 nm and a slow axis angle of 157.5 °.

  The output side polarizing plate 12 has a phase difference value that is half λ / 2 of the outgoing light wavelength λ, and the angle of the slow axis is the angle x between the horizontal side of the liquid crystal cell 11 and the transmission axis of the polarizing plate 12. By providing the retardation film 24 that is half x / 2 or (π + x) / 2, the oscillation direction of the emitted light of the liquid crystal display device 1 can be made horizontal, so that the reflection efficiency is improved and a bright image 4 is obtained. Obtainable. Hereinafter, the polarizing plates 12 and 13 arranged in the liquid crystal display device 1 will be described.

  FIG. 2A is a cross-sectional view showing the structure of the polarizing plate 12 disposed on the light emitting side of the liquid crystal display device 1. FIG. 2B is a plan view seen from the side where light enters the polarizing plate 12 (the lower side of FIG. 1A) in order to show the transmission axis and the slow axis of the polarizing plate 12.

  A polarizing plate 12 shown in FIG. 2A includes a polarizer 22, a retardation film 24, and a support 26, and the lower side of the figure is bonded to the liquid crystal cell 11 with an adhesive 21. The retardation film 24 is adhered to the outside of the polarizer 22 with an adhesive 23, and a support 26 of triacetyl cellulose (TAC) is adhered to the outside of the retardation film 24 with an adhesive 25 to protect the polarizing plate 12. is doing. The light transmitted through the liquid crystal cell 11 enters from the lower side of the figure, passes through the polarizer 22 and the retardation film 24 in this order, and is emitted from the upper side of the figure.

  As shown in FIG. 2B, the transmission axis 200 of the polarizer 22 is an angle of 135 ° with respect to one side in the horizontal direction of the liquid crystal cell 11, and the slow axis 201 of the retardation film 24 is the liquid crystal cell 11. The angle is 157.5 ° with respect to one side in the horizontal direction. The light transmitted through the liquid crystal cell 11 is 135 ° linearly polarized light, but the transmitted light is transmitted through the retardation film 24 having a retardation value λ / 2 that is half of the wavelength λ, thereby centering on the slow axis. Since the polarization direction is converted into a symmetric direction, transmitted light oscillating in the horizontal direction can be obtained.

  The light transmitted through the phase difference film 24 is changed in polarization direction in a symmetric direction with respect to the slow axis 201, so that the angle of the slow axis 201 is such that the horizontal side of the liquid crystal cell 11 and the transmission axis 200 are When the angle x is (π + x) / 2 or x / 2, the polarization direction of the light transmitted through the retardation film can be set to the horizontal direction. Therefore, the same effect can be obtained even if the angle of the slow axis 201 is 67.5 °.

  Further, in the present embodiment, the retardation value of the retardation film 24 is set to 275 nm specially for G (green) light, but the R (red) and B (blue) coloring is greatly affected. There was no. The retardation value of the retardation film 24 in the case of full color display is not limited to the above value, and may be in the range of 250 to 300 nm, which is half the wavelength of G (green) light.

  FIG. 3A is a cross-sectional view showing the structure of the polarizing plate 13 disposed on the light incident side. FIG. 3B shows the light transmitted to the polarizing plate 13 in order to show the transmission axis of the polarizing plate 12. It is the top view seen from the side (upper side of the same figure (a)) which enters.

  A polarizing plate 13 shown in FIG. 3A has a configuration in which a polarizer 32 is protected by a support 33 and is bonded to the liquid crystal cell 11 with an adhesive 31. The light emitted from the light source enters from the upper side of the figure. 3B, the transmission axis 300 of the polarizer 32 is disposed so as to be orthogonal to the transmission axis 200 of the polarizing plate 12.

  As described above, according to the present embodiment, the phase difference value is half the wavelength λ of the emitted light λ / 2 outside the polarizer 22 of the polarizing plate 12 disposed on the emitted light side of the liquid crystal cell 11. The angle between the slow axis 201 and the horizontal side of the liquid crystal cell 11 is (π + x) / 2 with respect to the angle x between the transmission axis 200 of the polarizer 22 and the horizontal side of the liquid crystal cell 11, Alternatively, by providing the retardation film 24 of x / 2, the polarization direction of the light transmitted through the polarizer 22 can be made horizontal, so that an image with good reflection efficiency can be obtained. Further, by rubbing the alignment films arranged on the counter substrate 112 and the array substrate 113 sandwiching the liquid crystal layer 111 at 45 ° and 135 °, a symmetric viewing angle can be obtained.

  The rubbing direction of the alignment film can be adjusted in the range of 45 ± 5 ° according to the angle at which the liquid crystal display device 1 is installed, so that a symmetric viewing angle can be obtained.

  Moreover, when the liquid crystal display device 1 is not a full-color display but is composed of two color filters, the retardation value of the retardation film 24 may be half of the average value of the wavelengths of the two colors of light. For example, when the liquid crystal display device 1 is composed of pixels of two colors, red having a wavelength of 650 nm and green having a wavelength of 550 nm, the retardation value of the retardation film 24 may be set to 300 nm.

  Furthermore, the phase difference value in the case where the liquid crystal display device 1 is composed of monochrome pixels is preferably set to half of the wavelength of the monochrome color. For example, in the case of a red pixel having a wavelength of 650 nm, the retardation value of the retardation film 24 may be set to 325 nm. Needless to say, it is optimized by setting the phase difference value to 275 nm when the emitted light is green with a wavelength of 550 nm and 225 nm when the emitted light is blue with a wavelength of 450 nm.

It is the schematic of the display system in one embodiment. It is a figure which shows the structure of the polarizing plate arrange | positioned at the emitted light side of the liquid crystal display device of the said display system, (a) is sectional drawing, (b) is a top view. It is a figure which shows the structure of the polarizing plate arrange | positioned at the incident light side of the liquid crystal display device of the said display system, (a) is sectional drawing, (b) is a top view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device 2 ... Reflection unit 3 ... Windshield 4 ... Image 11 ... Liquid crystal cell 111 ... Liquid crystal layer 112 ... Opposite substrate 113 ... Array substrate 12, 13 ... Polarizing plate 21, 23, 25 ... Adhesive 22 ... Polarizer 24 ... retardation film 26 ... support 31 ... adhesive 32 ... polarizer 33 ... support 200,300 ... transmission axis 201 ... slow axis

Claims (5)

A liquid crystal cell having a liquid crystal layer sandwiched between a pair of substrates; and a polarizing plate bonded to each of the pair of substrates, wherein light is incident from one of the polarizing plates and transmitted through the liquid crystal cell. A liquid crystal display device that emits light from the other polarizing plate,
The polarizing plate disposed on the light emitting side includes a polarizer and a retardation film,
The retardation film is disposed so that light transmitted through the polarizer is incident thereon,
When the angle formed by the transmission axis of the polarizer and one side in the horizontal direction of the liquid crystal cell is x, the angle formed by the slow axis of the retardation film and the one side is x / 2 or (π + x) / 2. And the retardation value of the retardation film is half the wavelength of the emitted light. In the liquid crystal cell, one pixel is composed of RGB sub-pixels,
The liquid crystal display device according to claim 1, wherein a retardation value of the retardation film is in a range of 250 to 300 nm. In the liquid crystal cell, one pixel is composed of sub-pixels of two colors,
The liquid crystal display device according to claim 1, wherein a retardation value of the retardation film is half of an average value of wavelengths of the emitted light of the two colors. The liquid crystal cell is in TN mode,
The rubbing direction of the alignment film disposed on each of the pair of substrates is in the range of 45 ± 5 ° with respect to one side in the horizontal direction of the liquid crystal cell and twisted by 90 ° with the rubbing direction of the other substrate. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is in a state. A liquid crystal display device according to any one of claims 1 to 4,
A reflection unit that reflects light emitted from the liquid crystal display device and projects an image;
A display system comprising:

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