JP4581450B2 - Transflective liquid crystal display device. - Google Patents

Description

  The present invention relates to a transflective liquid crystal display device capable of selectively executing a reflective display using external light and a transmissive display using irradiation light from a built-in backlight.

  In recent years, a liquid crystal display device has been widely used as a display of a mobile phone, which is becoming a necessity for young people. As a display of a mobile phone, which is a mobile device, low power consumption is required. Therefore, a transflective liquid crystal display device that can selectively display both reflective display and transmissive display is advantageous. This transflective liquid crystal display device performs reflective display using external light in an environment where sufficient external light such as natural light can be obtained, and backlight in an environment where sufficient external light cannot be obtained. Transmitted display by irradiation light from is performed.

  In a transflective liquid crystal display device, a transflective film that reflects part of incident light and transmits part of light is usually provided in a liquid crystal cell in order to prevent image blur due to parallax. As the semi-transmissive reflective film, there are a film formed in a thin film shape such as a metal vapor-deposited film and a film provided with an opening of a predetermined size for each pixel area.

  When the former thin-film transflective film is used, it is easy to manufacture, but the light use efficiency is poor in both reflective display and transmissive display. Tends to decrease.

On the other hand, the latter liquid crystal display device using the aperture-type transflective film is difficult to manufacture with a transparent electrode film or the like as compared with the former, but is not easy to manufacture. Since it is not necessary to reduce the film thickness simply by providing an opening in a predetermined area in one pixel, the reduction in light use efficiency in reflective display is eliminated. However, in transmissive display, only the light passing through the aperture is used for display and other light is lost, so the light utilization efficiency is poor, which is an obstacle to the low power consumption of the transflective liquid crystal display device. It has become.
JP 2001-281649 A

An object of the present invention is to provide a transflective liquid crystal display device capable of increasing the light use efficiency of light emitted from a backlight .

To solve the above problem, a semi-transmissive reflective liquid crystal display device of the present invention includes a liquid crystal display panel in which a liquid crystal layer is formed between the first substrate and the second substrate, between said liquid crystal layer A backlight in which a light guide plate is arranged so that the second substrate is interposed , and a reflective display area and a transmissive display area are formed for each display pixel , so that the first substrate side Reflective display using external light incident on the liquid crystal layer toward the second substrate side and the backlight incident on the liquid crystal layer from the second substrate side toward the first substrate side A transflective liquid crystal display device capable of transmissive display using light emitted from the liquid crystal display device, wherein the liquid crystal display device is disposed between the second substrate and the liquid crystal layer, and is disposed in a region corresponding to the transmissive display area. a first light reflecting film 1 of the opening portion is formed, the second A polarizing plate disposed between the plate light guiding plate, wherein disposed between the polarizing plate and the light guide plate, the second opening is formed in a region corresponding to said first opening and it is characterized in that it comprises a second light reflecting film.

According to the transflective liquid crystal display device of the present invention, the light use efficiency of the irradiation light from the backlight can be increased.

  In the transflective liquid crystal display device of the present invention, a plurality of pixels are arranged in a matrix, and each of the red, green, and blue color element stripe pieces extending along the rows or columns of the plurality of pixels. It is preferable that the color filter layer is disposed on the inner surface of either the front transparent substrate or the rear transparent substrate, so that the necessary color brightness is ensured and the color characteristics are substantially equal. A transparent color display is obtained.

  The green color element stripe piece among the red, green, and blue color element stripe pieces is preferably formed to have a width narrowed by a predetermined dimension at a predetermined position for each area corresponding to one pixel. Thus, it is possible to accurately ensure the area ratio between the green element and other color elements necessary for preventing white light from being colored.

  Furthermore, in the transflective liquid crystal display device according to the present invention, the second light reflecting film is a light reflecting film having the same shape in which the openings having the same arrangement pattern as the openings in the first light reflecting film are formed. Preferably, the utilization efficiency of the backlight light can be remarkably improved.

Hereinafter, preferred embodiments of the present invention will be described.
FIG. 1 is an explanatory view showing the overall configuration of a transflective liquid crystal display device as a first embodiment of the present invention, FIG. 2 is a partially enlarged sectional view thereof, and FIG. 3 is a liquid crystal in the transflective liquid crystal display device. FIG. 4 is a partially enlarged plan view of the display panel as seen from the front side which is the display viewing side, and FIG. 4 is a partially enlarged plan view of the liquid crystal display panel as seen from the rear side.

  As shown in FIG. 1, the transflective liquid crystal display device of the present embodiment is roughly composed of a liquid crystal display panel LP and a backlight BL.

  The backlight BL is a side-light type surface emitting illumination device, and includes a light guide plate 1 made of a transparent resin plate, a cold cathode tube 2 as a light source disposed opposite to one end surface thereof, and a liquid crystal display of the light guide plate 1. The light reflecting plate 3 is disposed on the back surface 1b opposite to the light emitting surface 1a opposed to the panel LP. According to the backlight BL, after the light emitted from the cold cathode tube 2 enters the light guide plate 1, it is diffusely reflected by the back surface 1b processed on the diffuse reflection surface, and is reflected from the light emission surface 1a to the liquid crystal display panel LP. It is emitted in a planar shape.

  As shown in FIG. 2, the liquid crystal display panel LP includes a pair of glass substrates 4 and 5 which are joined by a frame-shaped sealing material (not shown) with a predetermined gap therebetween and surrounded by a sealing material. The liquid crystal L is sealed between the five.

  The front glass substrate 4 disposed on the front side, which is the viewing side of the display of the pair of glass substrates 4 and 5, leaks light from other than the pixel region Dp on the inner surface facing the rear glass substrate 5. In order to prevent this, a black mask 6 (see FIG. 3) made of a light shielding material such as resin black is provided. The transflective liquid crystal display device according to the present embodiment is a dot matrix type liquid crystal display device in which pixels are arranged in a matrix. Therefore, the black mask 6 has an outer periphery surrounding a display region in which pixels are arranged in a matrix. A frame portion (not shown) disposed in the display portion and a crosspiece portion 6a disposed in a lattice pattern corresponding to the pixels in the display area.

  A color filter layer 7 is provided on the inner surface of the front glass substrate 4 so as to cover the exposed surface where the black mask 6 and the black mask 6 are not disposed. As shown in FIG. 3, the color filter layer 7 is formed by sequentially and sequentially arranging red, green, and blue color element stripe pieces 7r, 7g, and 7b. Each of the red, green, and blue color element stripe pieces 7r, 7g, and 7b is formed to extend along the arrangement direction of one row or one column of pixels.

  By the way, in color display by additive color mixing using color filters composed of red, green and blue color elements, if the area of each color element of red, green and blue is equal from the spectral characteristics of each color element, white light is emitted. Light green color. Therefore, in the present embodiment, only the green element stripe piece 7g among the red, green, and blue color element stripe pieces 7r, 7g, and 7b is provided with a predetermined value for each pixel as shown in FIG. A constricted portion n whose width is reduced by a predetermined dimension at the position is formed. As a result, the area of the green element stripe piece 7g is smaller than the other red and blue color element stripe pieces 7r and 7b by a pair of filter blanks e and e generated at the neck n. Green coloring is eliminated.

  In this case, as the configuration for reducing the area of the green element, the configuration in which slits or hole openings o are formed at predetermined positions in one pixel area as in the green element stripe piece 7g0 shown in FIG. However, it is extremely difficult to accurately form such a small closed compartment opening o by photolithography due to limitations of the resolution of the exposure machine and problems such as expansion during firing of the color element material. is there. On the other hand, when the constriction portion n is provided for each pixel as in this embodiment, the above-described problem is effectively solved, and the green element stripe piece 7g having a predetermined area is accurately obtained by photolithography. Can be formed. It should be noted that the green element 7g1 shown in FIG. 5 (b) has a configuration in which it is separated into islands by a predetermined area, and the green element stripe piece 7g 'shown in FIG. The desired green element area can be accurately ensured even by a narrow configuration.

  Referring back to FIG. 2, a transparent protective film 8 is laminated on the color filter layer 7 described above, and a plurality of scanning electrodes 9 made of a transparent conductive film are formed on the surface of the transparent protective film 8 with red element stripe pieces 7r. Are arranged in parallel along a direction (perpendicular to the paper surface) perpendicular to the extending direction of the color element stripe pieces. Each of these scanning electrodes 9 is disposed so as to correspond to a pair of adjacent beam portions 6a extending in the same direction (perpendicular to the paper surface) of the black mask 6. Then, the alignment film 10 is uniformly applied over the scan electrodes 9. The alignment film 10 is subjected to an alignment process in a predetermined direction.

  A front polarizing plate 11 is attached to the outer surface (front surface) of the front glass substrate 4 with its transmission axis positioned in a predetermined direction.

  On the other hand, a single film-like first light reflecting film 12 is provided on the inner surface of the rear glass substrate 5. The first light reflecting film 12 is a metal thin film formed by vapor deposition using a metal material such as aluminum or an alloy of silver, palladium, and copper, and has a smooth surface facing the liquid crystal layer L as a light reflecting surface. It is finished. As shown in FIG. 4, the first light reflecting film 12 has openings 12a corresponding to predetermined areas in the center of each pixel region. The area where the opening 12a is provided becomes the transmissive display area At of each pixel.

  On the first light reflecting film 12, a plurality of display electrodes 13 made of a transparent conductive film are arranged in parallel to each other so as to extend in a direction perpendicular to the scanning electrode 9 described above (the paper surface direction in FIG. 2). Yes. Similarly to the scanning electrode 9, the display electrode 13 is also arranged corresponding to a pair of adjacent beam portions (not shown) of the black mask 6 extending in the same direction (paper surface direction). The alignment film 14 is uniformly applied over the display electrodes 13. The alignment film 14 is subjected to an alignment process in a predetermined direction.

  In the present embodiment, a pair of liquid crystal molecules facing each other with the liquid crystal layer L interposed therebetween so that the liquid crystal molecules of the liquid crystal layer L are twisted and oriented from the alignment film 14 toward the counter-side alignment film 10 by about 230 ° ± 20 °. The alignment treatment direction of the alignment films 10 and 14 is set. That is, the liquid crystal display panel LP of the present embodiment is an STN (Super Twisted Nematic) type liquid crystal display panel LP.

  A rear polarizing plate 15 is attached to the outer surface of the rear glass substrate 5 with its transmission axis positioned in a predetermined direction.

  A second light reflecting film 16 is provided on the surface of the rear polarizing plate 15. The second light reflecting film 16 is disposed except for the area corresponding to the opening 12a provided in the first light reflecting film 12, and the surface facing the light emitting surface 1a of the backlight BL is used as a light reflecting surface. Of the irradiated light emitted from the backlight BL, light other than the light that passes through the opening 12a and is used for transmissive display is reflected toward the light emitting surface 1a of the backlight BL.

  As shown in FIG. 4, the second light reflecting film 16 of the present embodiment includes a plurality of light reflecting film bands 16 a arranged in parallel to the extending direction of the scanning electrode 9 between the openings 12 a of adjacent pixels. Become. These light reflecting film bands 16a can be easily installed by selectively attaching a metal foil such as silver to a predetermined area on the surface of the polarizing plate 15 and forming it on a member integrated with the polarizing plate 15. .

  As the second light reflecting film, an opening 16′a that is the same as the opening 12a of the first light reflecting film 12 is formed as in the second light reflecting film 16 ′ shown in FIG. 4B. It is good also as a structure which installs the thing of the same shape inside out, and this can further improve the light utilization efficiency of backlight irradiation light. However, in this case, if the positions of the openings 12a and 16'a of the respective light reflecting films 12 and 16 'are shifted, the aperture ratio is lowered, so that high installation accuracy is required. Therefore, in this case, it is preferable to employ a manufacturing method such as a vapor deposition method that can ensure high installation accuracy stably.

  The second light reflecting film is preferably laminated on the rear polarizing plate 15 so as to face the light guide plate 1 of the backlight BL as in the present embodiment. Can be further increased.

  A display operation in the transflective liquid crystal display device of the present embodiment configured as described above will be described below.

  First, the transmissive display operation will be described. As shown in FIG. 1, the light ray B out of the light emitted from the cold-cathode tube 2 is incident on the light guide plate 1 and diffusely reflected on the back surface thereof, and then emitted from the light exit surface 1a. 2, the light passes through the light reflecting film band 12 a of the second light reflecting film 12 and enters the rear polarizing plate 15. Here, only the linearly polarized light component along the transmission axis of about half of the light beam a incident on the polarizing plate 15 is transmitted, passes through the rear glass substrate 5, and passes through the opening 12a of the first light reflecting film 12. pass. The light beam a that has passed through the opening 12a sequentially passes through the display electrode 13 and the alignment film 14 and is emitted into the liquid crystal layer L.

  The pixels through which the light rays B are transmitted are in an initial alignment state in which the liquid crystal molecules are twisted and oriented at 230 ° in the off state, and the light rays A are subjected to the birefringence when passing through the pixels. Thereafter, the light ray B sequentially passes through the alignment film 10, the scanning electrode 9, and the transparent protective film 8, and is colored red when passing through the red element stripe piece 7r of the next color filter layer 7, and then the front side. The light passes through the glass substrate 4, passes through the front polarizing plate 11, and is emitted to the front side of the liquid crystal display panel LP which is the observation side. When the red colored light passes through the front polarizing plate 11, only the red component light along the transmission axis is transmitted, so that the red colored light with high color purity is emitted.

  On the other hand, the light beam B emitted from the cold cathode tube 2 is incident on the light guide plate 1, is diffusely reflected on the back surface thereof, then exits from the light exit surface 1 a, and the light reflection film band 12 a in the second light reflection film 12. The light is incident on the smoothed light reflecting surface, reflected there, and returned to the light guide plate 1 side. Thereafter, the light beam B passes through the light guide plate 1 and is reflected by the light reflecting plate 3 on the back side, then exits the light guide plate 1 again, and this time is directed between the light reflecting film bands 12a of the second light reflecting film 12, The light passes through the light reflecting film band 12a, and is emitted to the front side of the liquid crystal display panel LP along the same path as that of the light ray A described above.

  Even if the light emitted from the cold cathode tube 2 reenters the light guide plate 1 and is reflected by the light reflection plate 3 as in the case of the light beam b, it is emitted from the light guide plate 1 and is again reflected by the second light reflection film 12. Although there is also light incident on the light reflecting film band 12a, such light is finally reflected between the light reflecting film band 12a and the light reflecting plate 3 while being repeatedly reflected between the light reflecting film band 12a and the light reflecting film band 12a. Pass through.

  As described above, in the transmissive display by the transflective liquid crystal display device of the present embodiment, the backlight irradiation light, which has been conventionally blocked by the transflective film and lost, is re-reflected and used as display light. Therefore, the light use efficiency is significantly improved. As a result, low power consumption of the transflective liquid crystal display device is greatly promoted.

  In the reflective display, external light such as natural light enters from the front side of the liquid crystal display panel LP, and this incident light passes through the front polarizing plate 11 and is linearly polarized, and then passes through the front glass substrate 4 to form a color. The filter layer 7 passes through, for example, the red element stripe piece 7r and is colored red. Thereafter, the light passes through the transparent protective layer 8, the scanning electrode 9, and the alignment film 10 in order and enters the liquid crystal layer L, where it undergoes birefringence. Light incident on the liquid crystal layer L and subjected to birefringence is sequentially transmitted through the rear alignment film 14 and the display electrode 13 and then incident on the first light reflecting film 12.

  Of the light incident on the first light reflecting film 12, the light incident on the light reflecting surface is reflected here, passes through the display electrode 13 and the alignment film 14 again, and reenters the liquid crystal layer L. And after receiving the birefringence action by the liquid crystal layer again, the front alignment film 10, the scanning electrode 9, the transparent protective film 8, the red element stripe piece 7r, the front glass substrate 4, and the front polarizing plate 11 are sequentially transmitted, The light is emitted to the front side of the liquid crystal display panel LP. This emitted light is red colored light having a sufficient luminance by reciprocatingly transmitted through the front polarizing plate 11 and the liquid crystal layer L and having a sufficiently high color purity and being reflected by the first light reflecting film 12 with a high reflectance. .

  Of the light incident on the first light reflecting film 12, the light incident on the opening 12 a is incident on the rear glass substrate 5 as it is, and is sequentially transmitted through the rear glass substrate 5 and the rear polarizing plate 15 to generate the second light. The light is emitted between the light reflection film bands 16a of the reflection film 16 and then radiates out of the liquid crystal display panel LP to be lost light that is not used for display. However, the ratio of the above-mentioned dissipative loss light in the incident external light is at most about the ratio of the opening 12a with respect to the first light reflection film 12, and there is no risk of insufficient brightness in the reflective display.

  As described above, in the reflective display by the transflective liquid crystal display device of the present embodiment, the incident light is reflected with high reflection efficiency by the first light reflection film 12 having a high light shielding property. A reflective display is obtained.

  In addition, this invention is not limited to embodiment mentioned above. For example, the present invention can be effectively applied to the case where the color filter layer is formed not on the front substrate but on the rear substrate.

  Moreover, in the said embodiment, although the 2nd light reflection film is installed in the outermost surface in the back side board | substrate of a liquid crystal display panel, not only this but a phase difference film is further provided on a 2nd light reflection film. It is also possible to laminate various optical sheets such as.

  In addition, the present invention is not limited to the simple matrix type but can be applied to various other transflective liquid crystal display devices such as a segment type and an active matrix type.

1 is a configuration explanatory diagram showing an overall configuration of a transflective liquid crystal display device as a first embodiment of the present invention. It is a partial expanded sectional view which shows the detailed structure of the said transflective liquid crystal display device. It is the elements on larger scale which looked at the liquid crystal display panel of the said transflective liquid crystal display device from the front side. (A) is the partial enlarged plan view which looked at the said liquid crystal display panel from the back side, (b) is the partial enlarged plan view which shows the modification. (A)-(c) is each partial enlarged plan view which shows the various structure of the color filter layer which should be employ | adopted in the said transflective liquid crystal display device, (d) is a color filter layer structure as a comparative example with respect to them. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light guide plate 2 Cold cathode tube 3 Light reflecting plate 4 Front side glass substrate 5 Rear side glass substrate 6 Black mask 7 Color filter layer 7r Red element stripe piece 7g Green element stripe piece 7b Blue element stripe piece 8 Transparent protective film 9 Scanning electrode 10 , 14 Alignment film 11, 15 Polarizing plate 12 First light reflection film 12a Opening 13 Display electrode 16 Second light reflection film 16a Light reflection film band

Claims (4)

A liquid crystal display panel in which a liquid crystal layer is formed between a first substrate and a second substrate, and a backlight in which a light guide plate is disposed so that the second substrate is interposed between the liquid crystal layer and With
By forming a reflective display area and a transmissive display area for each display pixel, a reflective display using external light incident on the liquid crystal layer from the first substrate side toward the second substrate side; A transflective liquid crystal display device capable of transmissive display using irradiation light from the backlight incident on the liquid crystal layer from the second substrate side toward the first substrate side, ,
A first light reflecting film disposed between the second substrate and the liquid crystal layer and having a first opening formed in a region corresponding to the transmissive display area ;
A polarizing plate disposed between the second substrate and the light guide plate;
A second light reflecting film disposed between the polarizing plate and the light guide plate and having a second opening formed in a region corresponding to the first opening ;
A transflective liquid crystal display device comprising: The first opening and the second opening are formed for each display pixel so that one second opening corresponds to one first opening. The transflective liquid crystal display device according to claim 1, wherein The transflective system according to claim 1, wherein the backlight includes a reflecting plate disposed such that the light guide plate is interposed between the backlight and the second light reflecting film. Liquid crystal display device. A color filter in which each color element is arranged in a stripe shape corresponding to the arrangement of the display pixels,
The color filter is characterized in that a stripe width of the predetermined color element is partially narrowed by a predetermined dimension for each display pixel in a region where the predetermined color element overlaps the first light reflection film. The transflective liquid crystal display device according to any one of claims 1 to 3 .

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