JP2999317B2 - Reflective color 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 reflection type color liquid crystal display, and more particularly to a reflection type color liquid crystal display in which a fluorescent layer made of a transparent resin to which a fluorescent dye is added is formed on a reflection electrode.

[0002]

2. Description of the Related Art In recent years, applications of liquid crystal display devices to OA equipment such as word processors and laptop personal computers and pocket televisions have been rapidly advancing. In particular, a reflection type liquid crystal display device that uses ambient light and does not newly use a backlight has attracted attention because of its low power consumption and the possibility of reduction in thickness and weight.

Conventionally, a reflection type liquid crystal display device employs a twisted nematic (TN) system and a super twisted nematic (STN) system. In these systems, a polarizing plate is used so that incident light is incident on the polarizing plate. Is cut off, which does not effectively contribute to the display, and there is a problem that the display becomes dark.

To solve such a problem, there has been proposed a display mode in which all incident light is effectively used without using a polarizing plate. An example of such a mode is the phase-transition guest-host mode (DL White and G.
N. Taylor: J. Appl. Phys., 45.P. 4718, 1974). In this mode, a cholesteric-nematic phase transition phenomenon caused by an electric field is used.

[0005] There is also a reflection type multi-color filter liquid crystal display device in which a micro color filter is combined with this method (T. Ucida et al: Japan Display, P.312, 1986).
As shown in FIG. 5, the substrate 9 comprises a glass substrate 8, a transparent electrode 19 and a color filter 12, and a TFT
The other substrate 10 on which the (thin film transistor) is formed is a glass substrate 1, a first insulating layer 3, and a second insulating layer 17 having irregularities.
And the reflection electrode 18. A liquid crystal 15 is sealed between the substrates 9 and 10.

In this method, the color filter 12 and the reflection electrode 18 are provided on separate substrates (in FIG.
The substrate 9 and the reflective electrode 18 are provided on the TFT-side substrate 10), and irregularities are formed on the reflective electrode 18 to reduce scattering on the color filter 12, increase the intensity of light in the vertical direction, and increase the display surface. Is to make it brighter.

The TFT 11 has a gate electrode 2, a first insulating layer 3, a semiconductor layer 4 made of amorphous silicon, a contact electrode 5 made of phosphorus-doped silicon formed on the semiconductor layer 4, and furthermore, It is composed of a source electrode 6 and a drain electrode 7 stacked on each other, and has a function of a switching element.

[0008]

However, in the structure shown in FIG. 5 described above, the display is still dark as a reflection type color liquid crystal display device using no backlight, and the material of the reflection plate is used as a means for further increasing the brightness. And the surface shape of the reflection plate, the mutual positional relationship between the color filter and the reflection plate, and the formation of an anti-reflection film on the glass substrate surface to reduce the reflection on the glass substrate surface, etc. Is still not enough.

An object of the present invention is to solve the above-mentioned problems and to provide a reflective color liquid crystal display device having a bright display surface.

[0010]

According to the present invention, of a pair of transparent substrates disposed to face each other with a liquid crystal layer interposed therebetween, one of the substrates reflects an incident light from the other substrate side to the liquid crystal layer side. In a reflective color liquid crystal display device in which a reflective electrode is formed, a transparent fluorescent layer in which a fluorescent dye is added to a transparent resin is formed on the reflective electrode, and the fluorescent dye absorbs ultraviolet light. A reflective type color liquid crystal display device that emits fluorescent light in a visible region.

[0011]

The present invention is also characterized in that the liquid crystal display device is an active matrix type in which a non-linear element such as a thin film transistor is added to each picture element.

In the present invention, the fluorescent layer is formed on the reflective electrode on the one substrate, and a mosaic color filter made of red, green, and blue is formed on the other substrate opposed to the fluorescent layer. It is characterized by the following.

Further, according to the present invention, the nonlinear element is a thin film transistor, and an insulating layer is formed on the entire surface of the one substrate over the nonlinear element including a drain electrode and over a remaining region where the nonlinear element is not formed. The reflective electrode, which is a picture element electrode, is connected to the drain electrode through a through hole provided in the insulating layer.

[0015]

According to the present invention, in a reflective type color liquid crystal display device, by forming a fluorescent layer on a reflective electrode,
By effectively converting ultraviolet light that has not contributed to display to visible light in the visible region and combining it with an active device such as a TFT, a reflective color liquid crystal display device with excellent display contrast is obtained. Obtainable.

[0016]

EXAMPLES The reflective color liquid crystal display device according to the present invention will be described more specifically with reference to the following examples.

Embodiment 1 FIG. 1 is a sectional view of a reflective type color liquid crystal display device 30 according to an embodiment of the present invention, and FIG. 2 is a part of a reflective electrode 43 of the TFT-side substrate 26 shown in FIG. FIG. 4 is a plan view in which the fluorescent layer 44 is removed. In this embodiment, an active matrix element such as a TFT is added to each picture element of the TFT-side substrate 26, and a liquid crystal 49 is sealed between the TFT and the opposing substrate 27. A plurality of gate bus lines 32 made of chromium, tantalum, or the like are provided in parallel on an insulating substrate 31 made of glass or the like, and a gate electrode 33 branches from the gate bus line 32. The gate bus wiring 32 functions as a scanning line.

The silicon nitride (SiN _x ), silicon oxide (Si)
The gate insulating film 34 consisting of O _x) or the like is formed.
On the gate bus insulating film 34 above the gate electrode 33,
A semiconductor layer 35 made of amorphous silicon (a-Si) is formed. Above the semiconductor layer 35, a contact electrode 41 made of phosphorus-doped amorphous silicon is formed with an etch stopper (ES) layer 42 interposed therebetween. On one contact electrode 41, a source electrode 36 made of titanium, molybdenum, aluminum, or the like is superposed, and on the other contact electrode 41, a drain electrode 37 made of titanium, molybdenum, aluminum, or the like is formed, similarly to the source electrode 36. Are superimposed.

As shown in FIG. 2, the source electrode 36 is connected to a source bus line 39 which intersects the gate bus line 32 with the gate insulating film 34 interposed therebetween. The source bus wiring 39 functions as a signal line. The source bus wiring 39 is also formed of the same metal as the source electrode 36. Gate electrode 33, gate insulating film 34, semiconductor layer 3
5, ES layer 42, source electrode 36 and drain electrode 3
Reference numeral 7 denotes a TFT 40, which has a function of a switching element.

Reflective electrode 4 made of aluminum, silver, etc.
3 is formed on a region 38 corresponding to each picture element and also serves as a picture element electrode.
2. Including the source bus wiring 39 and the ES layer 42,
It is covered with a fluorescent layer 44 made of a transparent resin to which a fluorescent dye has been added.

The opposing substrate 27 opposing the liquid crystal 49 therebetween.
Comprises a transparent substrate 45 made of glass or the like, a transparent counter electrode 47 made of indium-tin oxide (ITO) formed on almost the entire surface thereof, and a color filter 46 formed on the surface thereof.

The incident light 20 enters from the opposing substrate 27, and the glass substrate 45, the opposing electrode 47, the color filter 4
6. The light passes through the liquid crystal 49 and reaches the TFT-side substrate 26. Here, first, a part of the ultraviolet light is absorbed by the fluorescent layer 44. Light not absorbed by the fluorescent layer 44 is reflected by the reflective electrode 43, and a part of the ultraviolet light is absorbed by the fluorescent layer 44. The ultraviolet light absorbed by the fluorescent layer 44 at the time of incidence and reflection is converted into visible light, and together with the reflected light 21,
The light passes through the liquid crystal 49, the color filter 46, the counter electrode 47, and the glass substrate 45, and is emitted to the display surface.

As fluorescent dyes, thioflavin, brilliant sulfoflavin, brilliant yellow, fluorol green gold, rhodamine B, rhodamine 6G
CP, fluorescein, eosin and the like are used alone or in combination of several kinds.

Next, a brief description will be given of a method of manufacturing the reflection type color liquid crystal display device of this embodiment. TFT side substrate 26
The source electrode 36 and the drain electrode 37 are formed by the method used in the prior art. The reflective electrode 43 is formed on the region 38 thereon. Since the reflection electrode 43 also serves as a pixel electrode, aluminum or silver having high reflectivity is used for the reflection electrode 43. In this embodiment, aluminum was used. On the reflection electrode 43, the fluorescent layer 4 including the gate bus wiring 32, the source bus wiring 39, and the ES layer 42 is formed.
4 is formed. In this embodiment, "PC White 3P" (manufactured by Nippon Kayaku Co., Ltd.) is used as a fluorescent dye used in the fluorescent layer.
1 to 1% by weight, dissolved in a thermosetting resin "OCMX-2" (manufactured by Nippon Kayaku Co., Ltd.), applied to the reflective electrode 43 to a thickness of 2 to 3 [mu] m using a spinner, and then heated at 170 [deg.] C. It was baked for 2 hours.

After forming the counter electrode 47 on the glass substrate 45 by the method used in the prior art on the glass substrate 45, the counter substrate 27 is changed from red, green and blue to correspond to each picture element region. Is formed. Examples of a method for forming a color filter include a gelatin dyeing method, a pigment dispersion method, an electrodeposition method, a printing method, and a vapor deposition method. In this example, a gelatin staining method was used. In the case of a reflection type color liquid crystal display device, it is necessary to reduce the color density and the color density of the color filter in terms of brightness. An alignment film (not shown) of polyimide or the like is formed on the TFT-side substrate 26 and the opposite-side substrate 27 manufactured as described above. Complete the liquid crystal display device.

As described above, according to the present embodiment, ultraviolet light, which has not conventionally contributed to display, can be converted into visible light and used as display light, and bright display can be achieved without using a backlight. Can be implemented.

Embodiment 2 FIG. 3 is a sectional view of a reflection type color liquid crystal display device 50 according to another embodiment of the present invention.

In this embodiment, a transparent picture element electrode 54 is formed on a glass substrate 58 of a TFT side substrate 51 and a color filter 53 is formed thereon, and a reflection electrode 55 is formed on a glass substrate 59 of an opposite side substrate 52. Next, a fluorescent layer 56 is formed. TFT
The configuration of 40 is similar to the configuration of the first embodiment, and corresponding parts are denoted by the same reference numerals. The color filter 53 is formed on the pixel electrode 54 because the scattering on the color filter surface increases when the color filter 53 is formed on the reflective electrode 55. Must be provided on separate substrates. In this embodiment, a mosaic color filter 53 composed of red, green and blue is formed on a transparent picture element electrode 54 connected to the drain electrode 37 of the TFT.

On the other hand, a reflective electrode 55 made of aluminum in this embodiment is formed on a glass substrate 59 of the opposing substrate 52, and "rhodamine 6" which is a kind of fluorescent substance is formed thereon.
“GCP” was uniformly dispersed in a thermosetting resin, applied by a spinner, baked and cured to form a fluorescent layer 56.

The incident light 20 enters from the TFT-side substrate 51, and the glass substrate 58, the gate insulating film 34, the pixel electrode 5
4. The light passes through the color filter 53 and the liquid crystal 49 and reaches the opposing substrate 52. Here, first, a part of the ultraviolet light is absorbed by the fluorescent layer 56. Light not absorbed by the fluorescent layer 56 is reflected by the reflective electrode 55, and a part of the ultraviolet light is absorbed by the fluorescent layer 56. The fluorescent layer 56 at the time of incidence and reflection
The ultraviolet light absorbed by the liquid crystal is converted into visible light,
9, the light passes through the color filter 53, the pixel electrode 54, the gate insulating film 34, and the glass substrate 58, and is mixed with the reflected light 21 and emitted to the display surface.

Embodiment 3 FIG. 4 is a sectional view of a reflection type color liquid crystal display device 60 according to still another embodiment of the present invention.

In this embodiment, as in the first embodiment, a reflective electrode 65 is formed on a glass substrate 68 of a TFT-side substrate 61, and a fluorescent layer 66 is formed thereon, and a transparent counter electrode is formed on a glass plate 69 of a counter-side substrate 62. An electrode 64 and a color filter 63 are formed thereon. The configuration of the TFT 40 is similar to the configuration of the first embodiment, and corresponding portions are denoted by the same reference numerals.

In this embodiment, the insulating film 67 covers the entire upper surface on which the TFT 40 is formed, and thus the drain electrode 37 is formed.
The insulating film 67 is formed over the entire surface over the TFT 40 including the TFT and over the remaining region where the TFT 40 is not formed. The thickness of the insulating film 67 is 5000 to 8000 °, and the material is preferably an inorganic material such as an oxide film or an organic material such as a polyimide resin, an acrylic resin, or an epoxy resin. Particularly, an acrylic resin is preferable. A through hole 70 is formed in a part of the insulating film 67 by dry etching or wet etching, and a part of the drain electrode 37 is exposed by the through hole 70. After that, a layer of the reflective electrode 65 such as aluminum is formed on the entire surface, and the reflective electrode 65 and the drain electrode 37 are connected by a through hole portion.
The reflective electrode 65 is patterned as a picture element electrode. Further, on the reflective electrode 65, “thioflavin”, which is a kind of fluorescent dye, was uniformly dispersed in a thermosetting resin, applied by a spinner, and baked and cured to form a fluorescent layer 66.

In this embodiment, the TFT 40 and the source electrode 36
Since the surface on which the drain electrode 37 is formed and the surface on which the reflective electrode 65 also serving as a pixel electrode is formed are located on different surfaces via the insulating layer 67, the pixel electrode 65 can be widened. Panel aperture ratio can be made larger than that of

[0035]

As described above, according to the present invention, a fluorescent layer made of a transparent resin to which a fluorescent dye is added is formed on a reflective electrode, whereby ultraviolet light can be converted to visible light. A reflective color liquid crystal display device with a bright display can be obtained without using a light. Furthermore, according to the present invention, the fluorescent layer is transparent, so that the incident light is converted into visible light by absorbing a part of the ultraviolet light by the fluorescent layer, and the light not absorbed by the fluorescent layer is The light passes through the fluorescent layer, is reflected by the reflective electrode, and a part of the ultraviolet light included in the reflected light is absorbed by the fluorescent layer and converted into visible light. In this way, the fluorescent layer efficiently converts the ultraviolet light into visible light, and the display surface can be brightened as described above together with the visible light used for display as it is by the reflective electrode. It is composed of an active matrix type to which a non-linear element such as a thin film transistor is added. In particular, a fluorescent layer is formed on a reflective electrode, and a mosaic color filter is not formed on a reflective electrode. Can be prevented, and the drain electrode of the thin film transistor
The reflective electrode is connected to the reflective electrode via a through hole provided in the insulating layer, so that the reflective electrode on the insulating layer can be recorded as a pixel electrode, and the panel aperture ratio can be increased, thereby providing a bright display. Face can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of one embodiment of the present invention.

FIG. 2 is a plan view of the TFT-side substrate 26 of the embodiment shown in FIG.

FIG. 3 is a sectional view of another embodiment of the present invention.

FIG. 4 is a sectional view of still another embodiment of the present invention.

FIG. 5 is a cross-sectional view for explaining a conventional technique.

[Explanation of symbols]

 Reference Signs List 20 incident light 21 reflected light 30, 50, 60 reflective color liquid crystal display device 40 TFT (thin film transistor) 43, 65 reflective electrode 44, 56, 66 serving also as pixel electrode fluorescent layer 46, 53, 63 color filter 47, 64 Electrode 49 Liquid crystal 54 Transparent picture element electrode 55 Reflection electrode

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-75686 (JP, A) JP-A-59-171928 (JP, A) JP-A-3-228022 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G02F 1/1335 G09F 9/30

Claims (4)

(57) [Claims] 1. A reflective type in which, of a pair of transparent substrates disposed to face each other with a liquid crystal layer interposed therebetween, a reflective electrode for reflecting incident light from the other substrate is formed on one of the substrates on the liquid crystal layer side. In a color liquid crystal display device, a transparent fluorescent layer in which a fluorescent dye is added in a transparent resin is formed on the reflective electrode, and the fluorescent dye absorbs ultraviolet light and emits visible light. Characteristic reflective color liquid crystal display device. 2. The reflection type color liquid crystal display device according to claim 1, wherein the liquid crystal display device is an active matrix type in which a non-linear element such as a thin film transistor is added to each picture element. 3. The method according to claim 1, wherein the reflecting electrode on the one substrate is
The reflective color liquid crystal display device according to claim 2, wherein the fluorescent layer is formed, and a mosaic color filter made of red, green, and blue is formed on the other substrate facing the fluorescent layer. 4. The non-linear element is a thin film transistor, and an insulating layer is formed on the entire surface of the one substrate over the non-linear element including a drain electrode and over a remaining region where the non-linear element is not formed, 4. The reflective color liquid crystal display device according to claim 3, wherein the reflective electrode serving as a picture element electrode and the drain electrode are connected through a through hole provided in the insulating layer.