JP2003279957A - Liquid crystal display device, its manufacturing method and electronic appliance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transflective liquid crystal display device in which bright display is obtained at the time of a transmission mode, its visibility is excellent and its thickness is made thin. <P>SOLUTION: In this transflective liquid crystal display device 10, a liquid crystal layer 16 is held between an upper substrate 14 and a lower substrate 13, a transflective layer 18 is provided on the lower substrate 13 and a back light 12 is provided on the outer part of the lower substrate 13. Then, an upper polarizing plate 36 is provided on the outer surface side of the upper substrate 14, a lower polarizing plate 28 is provided on the outer surface side of the lower substrate 13, and a phase difference layer 20 having the phase difference of 1/4 wavelength is successively provided only in a reflection display area R on the inner surface side of the lower substrate 13. <P>COPYRIGHT: (C)2004,JPO

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, a method of manufacturing the same, and electronic equipment, and more particularly to a technique for realizing a thin transflective liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, there has been proposed a liquid crystal display device that utilizes external light in a bright place like a normal reflection type liquid crystal display device and makes a display visually recognizable by an internal light source in a dark place. There is. This liquid crystal display device employs a display method that has both a reflective type and a transmissive type, and power consumption is reduced by switching to either a reflective display type or a transmissive display type depending on the ambient brightness. On the other hand, a clear display can be performed even when the surroundings are dark. Less than,
In this specification, this type of liquid crystal display device is referred to as a “semi-transmissive reflection type liquid crystal display device”. As one form of a semi-transmissive reflection type liquid crystal display device, there is one in which a reflective film in which an opening for light transmission is formed in a metal film such as aluminum is provided on the inner surface of the lower substrate and the reflective film functions as a semi-transmissive reflective film. Proposed. By providing a metal film on the inner surface of the lower substrate, this liquid crystal display device has an effect of preventing the influence of parallax due to the thickness of the lower substrate, and particularly preventing color mixing in a structure including a color filter. In this specification, the liquid crystal side surface of each substrate constituting the liquid crystal display device is referred to as “inner surface”,
The opposite surface is called the "outer surface".

FIG. 7 shows an example of a transflective liquid crystal display device using this type of transflective film. In this liquid crystal display device 100, a pair of glass substrates 101, 102
A liquid crystal layer 103 is sandwiched in between, and a semi-transmissive reflective layer 104 having an opening 104a on the inner surface of the lower substrate 101, a transparent conductive film such as indium tin oxide (hereinafter abbreviated as ITO). The transparent electrode 108 made of is laminated, and the alignment film 107 is formed so as to cover the transparent electrode 108. On the other hand, ITO is formed on the inner surface of the upper substrate 102.
A transparent electrode 112 made of a transparent conductive film such as the above is formed, and an alignment film 113 is formed so as to cover the transparent electrode 112. In addition, on the outer surface side of the upper substrate 102, the upper substrate 10
Two retardation plates 118 and 119 (these retardation plates function as the quarter-wave plate 120) and an upper polarizing plate 114 are arranged in this order from the 2 side, and 1 / is provided on the outer surface side of the lower substrate 101.
A four-wave plate 115 and a lower polarizing plate 116 are provided in this order. Further, the light source 122, the light guide plate 123, and the reflection plate 124.
A backlight 117 (illumination means) including the above is disposed below the lower polarizing plate 116. The quarter wave plate 1
Reference numerals 15 and 120 are capable of converting linearly polarized light into substantially circularly polarized light in a certain wavelength band.

A transflective liquid crystal display device 10 shown in FIG.
The display principle of 0 will be described below with reference to FIG. It should be noted that FIG. 8 shows only the constituent elements of the liquid crystal display device of FIG. 7 that are necessary for explaining the display principle. First, when dark display is performed, a voltage is applied to the liquid crystal layer 103 (on state) so that there is no phase difference in the liquid crystal layer 103. In reflective display, light incident from above the upper polarizing plate 114 is linearly polarized light perpendicular to the paper surface after passing through the upper polarizing plate 114, assuming that the transmission axis of the upper polarizing plate 114 is perpendicular to the paper surface. After passing through the quarter-wave plate 120, it becomes counterclockwise circularly polarized light, and the liquid crystal layer 1 remains as it is.
03 is transmitted. Then, when the light is reflected by the surface of the semi-transmissive reflective layer 104 on the lower substrate 101, the rotation direction is reversed to become clockwise circularly polarized light, and the liquid crystal layer 103 is transmitted as it is, and the quarter wavelength plate 120 is transmitted. After that, it becomes a linearly polarized light parallel to the paper surface. Here, since the upper polarizing plate 114 has a transmission axis perpendicular to the paper surface, the reflected light is absorbed by the upper polarizing plate 114 and does not return to the outside (observer side), resulting in a dark display.

On the other hand, in the transmissive display, the light emitted from the backlight 117 is transmitted through the lower polarizing plate 116 after the transmission axis of the lower polarizing plate 116 is parallel to the paper surface.
Linearly polarized light parallel to the plane of the paper, and a quarter wave plate 11
After passing through 5, the light becomes circularly polarized light in the clockwise direction and passes through the liquid crystal layer 103 as it is. Then, the clockwise circularly polarized light passes through the quarter-wave plate 120 and then becomes linearly polarized light that is parallel to the paper surface, and is absorbed by the upper polarizing plate 114 as in the reflection mode, resulting in a dark display.

Next, when performing bright display, the liquid crystal layer 10
No voltage is applied to 3 (off state), and the phase difference is set to 1/4 wavelength due to the birefringence effect in the liquid crystal layer 103 at this time. In the reflective display, the light is incident from above the upper polarizing plate 114, and the upper polarizing plate 114, 1 /
The counterclockwise circularly polarized light that has passed through the four-wave plate 120 becomes linearly polarized light that is parallel to the paper surface when it reaches the surface of the semi-transmissive reflective layer 104 after passing through the liquid crystal layer 103. Then, when the light is reflected on the surface of the semi-transmissive reflective layer 104 and transmitted through the liquid crystal layer 103, it becomes a counterclockwise circularly polarized light again, and after passing through the quarter wavelength plate 120, becomes a linearly polarized light perpendicular to the paper surface. Here, since the upper polarizing plate 114 has a transmission axis perpendicular to the paper surface,
The reflected light passes through the upper polarizing plate 114 and returns to the outside (observer side), resulting in a bright display.

On the other hand, in the transmissive display, the light is incident from the backlight 117, and the lower polarizing plate 116 and the quarter wave plate 11 are used.
The clockwise circularly polarized light after passing through 5 becomes linearly polarized light perpendicular to the paper surface at the stage of passing through the liquid crystal layer 103. When the linearly polarized light perpendicular to the paper surface passes through the quarter-wave plate 120, it becomes left-handed circularly polarized light. Since the upper polarizing plate 114 has a transmission axis perpendicular to the paper surface, among the left-handed circularly polarized light. Only linearly polarized light that is perpendicular to the paper surface passes through the upper polarizing plate 114 to provide a bright display.

[0008]

As described above, according to the liquid crystal display device 100 shown in FIGS. 7 and 8, although the display can be visually recognized regardless of the presence or absence of external light, the display is transparent as compared with the reflective display. There was a problem that the brightness of the display was insufficient.
The reason is that, of the light emitted from the backlight 117, the light that does not pass through the opening 104a of the semi-transmissive reflective layer 104 is reflected on the back surface of the semi-transmissive reflective layer 104, and the rotation direction is reversed to the left. Circularly polarized light becomes 1/4 wavelength plate 1
When it passes through 15, it becomes a linearly polarized light which is perpendicular to the paper surface. Then, this linearly polarized light is absorbed by the lower polarizing plate 116 having a transmission axis parallel to the paper surface. That is, of the light emitted from the backlight 117, the opening 104
Light that has not passed through a is transmitted through the lower polarizing plate 116 without being absorbed by the lower polarizing plate 116, and the backlight 1
When returning to 17, the return light is emitted toward the liquid crystal cell again, and the brightness of the backlight 117 is effectively improved. However, in reality, after being reflected on the back surface of the semi-transmissive reflective layer 104, the lower polarized light is emitted. This is because the plate 116 absorbs almost everything and cannot be reused.

Further, in the liquid crystal display device shown in FIG. 7, since it is necessary to attach a plurality of retardation plates and polarizing plates to both outer surfaces of a pair of substrates sandwiching the liquid crystal layer, the structure is complicated and the number of parts is large. However, there are problems such as a large number of manufacturing costs, a high manufacturing cost, and a thin liquid crystal display device.

The present invention has been made to solve the above problems, and in a transflective liquid crystal display device capable of both reflective display and transmissive display, a bright display can be obtained especially in the transmissive mode. And has excellent visibility,
An object of the present invention is to provide a liquid crystal display device having a simplified structure and a reduced thickness, and a manufacturing method thereof. It is another object of the present invention to provide an electronic device having a thin liquid crystal display unit having excellent visibility.

[0011]

In order to solve the above-mentioned problems, a liquid crystal display device according to the present invention has a liquid crystal layer sandwiched between an upper substrate and a lower substrate which are arranged to face each other. What is claimed is: 1. A transflective liquid crystal display device, comprising: an upper polarizing plate and a lower polarizing plate provided above and below a layer and having a reflective display region and a transmissive display region in one dot, wherein A reflective layer is provided in the display region, and a retardation layer is provided on the reflective layer.

Among several factors that reduce the brightness of transmissive display, the problem that the light emitted from the backlight and reflected on the back surface of the semi-transmissive reflective layer is absorbed by the lower polarizing plate and cannot be reused is solved. Therefore, the applicant has already applied for a liquid crystal display device in which a retardation layer (1/4 wavelength) is provided only in the transmissive display region on the inner surface side of the lower substrate. According to this configuration, it is not necessary to provide a retardation plate (1/4 wavelength plate) between the lower substrate and the backlight, and the light reflected on the back surface of the semi-transmissive reflective layer passes through the lower polarizing plate as it is, Since the light is reflected by the reflector of the backlight and re-enters the liquid crystal panel, the backlight light can be effectively used. However, in this configuration, the lower retardation plate is only arranged on the inner surface of the liquid crystal panel, the configuration of the upper retardation plate, the polarizing plate, etc. does not change, and the problem of a complicated structure and a large number of parts is solved. It remains untouched.

Therefore, the present inventors have conceived a structure in which a retardation layer is provided only in the reflective display region on the inner surface of the lower substrate, contrary to the above structure. In this configuration, not only the lower retardation plate but also the upper retardation plate can be eliminated. As a result, the problem that the lower polarizing plate absorbs the light reflected on the back surface of the semi-transmissive reflective layer in the conventional configuration is solved, and the transmissive display can be made brighter than in the conventional configuration.
Further, the structure is simpler than that of the conventional one, and the device can be made thinner. The display principle of the liquid crystal display device of the present invention will be described in the [Embodiment mode] section.

Next, in the liquid crystal display device according to the present invention, the retardation imparted to the transmitted light by the retardation layer is
The phase difference given to the transmitted light by the liquid crystal layer is approximately 1/4 wavelength, and the phase difference is approximately zero and approximately 1 due to the change in the voltage application state.
It can be configured to be switched to and from a quarter wavelength.

According to this structure, the maximum brightness can be obtained during the transmissive display. In addition, 1 on the outer surface side of the liquid crystal cell
The same operation as that of the conventional liquid crystal display device having the / 4 wavelength plate is possible, and the thinning can be realized by omitting the ¼ wavelength plate on the outer surface side of the liquid crystal cell.

Next, in the liquid crystal display device according to the present invention, the retardation layer may be made of a polymer liquid crystal. According to this structure, the retardation layer can be formed relatively easily on the inner surface side of the substrate.

Alternatively, the retardation layer may be formed by photopolymerizing a liquid crystalline monomer. According to this structure, the retardation layer can be easily formed at a predetermined position with a predetermined shape.

Next, in the liquid crystal display device according to the present invention, a reflective polarizing plate having a transmission axis substantially parallel to the transmission axis of the lower polarizing plate is provided on the outer surface side of the lower substrate. You can With this configuration, of the light emitted from the backlight, the linearly polarized light that would otherwise be absorbed by the lower polarizing plate without the reflective polarizing plate is reflected by the reflective polarizing plate and returned to the backlight. This light can also be reused for transmissive display. The reason why this linearly polarized light can eventually pass through the reflective polarizing plate and contribute to the display is that while the linearly polarized light reflected by the reflective polarizing plate repeats reflection, the polarization axis direction changes and has a polarizing axis in a direction different from the initial direction. This is because it is converted into linearly polarized light. By adopting this configuration, the transmissive display can be made brighter.

Next, in the method for manufacturing a liquid crystal display device according to the present invention, a step of forming a reflective layer in a region corresponding to the reflective display region on the lower substrate, a polymer liquid crystal layer and a photosensitive resin layer are sequentially formed. After that, the photosensitive resin layer is patterned by using a photolithography method, and the polymer liquid crystal layer is etched by using the patterned photosensitive resin layer as a mask to locally leave the polymer liquid crystal layer. And a step of forming a retardation layer made of the polymer liquid crystal layer above the reflective layer.

Further, as a method of manufacturing a liquid crystal display device according to the present invention, a step of forming a reflective layer in a region corresponding to the reflective display region on the lower substrate, a step of forming a layer made of a liquid crystalline monomer, A step of forming a retardation layer made of the liquid crystalline monomer polymer above the reflective layer by locally photopolymerizing the liquid crystalline monomer using a lithographic method to form a liquid crystalline monomer polymer; It is also possible to apply a manufacturing method characterized by having. The "liquid crystal monomer" referred to here is
It means a substance which can take a liquid crystal phase by itself, or a substance which does not take a liquid crystal phase by itself but does not lose the liquid crystal state of the mixture when mixed in the liquid crystal phase.

In any of the methods, the structure in which the retardation layer is locally formed only in the reflective display area can be relatively easily realized by using the ordinary photolithography method. Then, for example, after forming the retardation layer, a photosensitive resin layer is formed, and the photosensitive resin layer is patterned by using a photolithography method so that the photosensitive resin layer remains above the retardation layer. In this case, the step of removing the photosensitive resin layer can be omitted,
The manufacturing process can be simplified.

An electronic apparatus according to the present invention is characterized by including the liquid crystal display device described above. With this configuration, it is possible to provide an electronic device that includes a thin liquid crystal display unit that has a bright display in the transmissive mode, excellent visibility, and is thin.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view showing a schematic configuration of the liquid crystal display device of the present embodiment, and FIG. 2 is a diagram for explaining the display principle thereof, showing only the components necessary for explaining the display principle. Is. The present embodiment is an example of a passive matrix type transflective color liquid crystal display device. In all of the following drawings, in order to make the drawings easy to see, the film thicknesses, the dimensional ratios, and the like of the respective constituent elements are appropriately changed.

The liquid crystal display device 10 of this embodiment is shown in FIG.
As shown in, the liquid crystal cell 11 and the backlight 12 (illumination device) are provided. In the liquid crystal cell 11, a lower substrate 13 and an upper substrate 14 are arranged so as to face each other.
STN (Super Twisted) in the space sandwiched between
The liquid crystal layer 16 is formed by enclosing a liquid crystal or the like. The backlight 12 is arranged on the rear surface side of the liquid crystal cell 11 (the outer surface side of the lower substrate 13).

On the inner surface side of the lower substrate 13 made of a translucent material such as glass or plastic, a semi-transmissive reflection layer 18 made of a metal film having a high reflectance such as aluminum, silver or an alloy thereof is formed. There is. The semi-transmissive reflective layer 18 is provided with an opening 18a for transmitting the light emitted from the backlight 12 for each pixel, and in the formation region of the semi-transmissive reflective layer 18, a metal film is actually formed. The existing portion constitutes the reflective display area R, and the portion of the opening 18a constitutes the transmissive display area T.

The semi-transmissive reflective layer 18 in the reflective display region R
The retardation layer 20 is laminated on the top. Retardation layer 20
Is made of polymer liquid crystal, for example, and imparts a phase difference of ¼ wavelength of visible light incident on the liquid crystal cell 11. When the manufacturing method according to the present invention described below is applied to the manufacturing of the present embodiment, the insulating film such as the acrylic photosensitive resin used for patterning the retardation layer 20 remains on the retardation layer 20. Alternatively, a flattening film for flattening a step portion formed between the transmissive display region T and the reflective display region R by the retardation layer 20 or the insulating film may be provided so as to cover each layer. .

The retardation layer 20 can be formed, for example, by the following two methods. The first method is
First, SE-3140 (trade name, manufactured by Nissan Chemical Co., Ltd.), which is an alignment film material, is formed on a substrate on which the semi-transmissive reflective layer 18 is formed.
Is applied by a spin coating method or a flexographic printing method and baked, and then a rubbing treatment is performed. Next, a polymer liquid crystal solution is applied onto this alignment film by a spin coating method (for example, rotation speed 700 rpm for 30 seconds). The polymer liquid crystal used here is, for example, an 8% solution of PLC-7023 (trade name, manufactured by Asahi Denka Co., Ltd.), the solvent is a mixed solution of cyclohexanone and methyl ethyl ketone, the isotropic transition temperature is 170 ° C., and the refractive index is Anisotropy Δn is 0.21.

Next, the polymer liquid crystal layer is prebaked at 80 ° C.
For 1 minute and further heated for 30 minutes at 180 ° C., which is higher than the isotropic transition temperature (170 ° C.) of the polymer liquid crystal, and then gradually cooled to orient the polymer liquid crystal. When the present inventor actually manufactured under these conditions, the film thickness was 630
nm, and the phase difference was 133 nm.

Next, an acrylic photosensitive resin NN-525 (trade name, JSR) is formed so as to cover the polymer liquid crystal layer.
Manufactured by spin coat method (for example, rotation speed 700 rp)
m for 30 seconds). At this time, the film thickness is 2.3 μm
Met. Next, pre-baking the photosensitive resin layer to 80
After 3 minutes at ℃, exposure using a photomask (for example, the exposure intensity is 140 mJ / cm ² , the value measured by an ultraviolet photometer with a sensitivity of 350 nm), and immersed in an alkaline developer at room temperature for 90 seconds. Then, development is performed to leave the protective layer only in the reflective display area. Since the above acrylic photosensitive resin is a negative type, it is necessary to form a photomask so that the reflective display area is exposed.

Next, in order to completely cure the photosensitive resin layer, post exposure is performed with an exposure intensity of 2000 mJ / cm ² . At 1000 mJ / cm ² or less, peeling of the photosensitive resin layer occurred during the development of the polymer liquid crystal in the next step.
Since there was no problem at 00 mJ / cm ² or more, 2000
It was set to mJ / cm ² . Then, it is immersed in an etching solution composed of N-methyl-2pyrrolidinone at room temperature for 30 minutes,
The polymer liquid crystal is etched. Then, this substrate is
By drying at 0 ° C. for 3 minutes, the retardation layer 20 made of polymer liquid crystal and the acrylic photosensitive resin layer are formed.
Then, by removing the photosensitive resin layer, the retardation layer 20 formed only on the reflective layer 18 shown in FIG. 1 is obtained. The photosensitive resin layer may be removed, but it may be left on the retardation layer 20. With this configuration,
The operation of the liquid crystal display device is not limited.

In the second method, a UV curable liquid crystal UCL-008-K1 (trade name, Dainippon Ink and Chemicals, Inc.), which is a liquid crystalline monomer, is formed on a substrate on which an alignment film is formed in the same manner as in the first method. )) Is applied by a spin coating method (for example, rotation speed 700 rpm for 30 seconds). The liquid crystalline monomer solution used here is N-methyl-2.
25% in a mixed solvent of pyrrolidinone and γ-butyrolactone
It has been diluted to 1, and has an isotropic transition temperature of 6
The refractive index anisotropy Δn is 0.20 at 9 ° C.

Then, the liquid crystalline monomer is dried at 60 ° C. for 5 minutes, heated at 90 ° C. for 5 minutes at the isotropic transition temperature (69 ° C.) or higher, and then gradually cooled to align the liquid crystalline monomer. When the present inventor actually manufactured under this condition, a film thickness of 650 nm was obtained. Then, exposure using a photomask (for example, the exposure intensity is 3000 m
J / cm ² ) to locally photopolymerize the liquid crystalline monomer, and then develop by immersing in an alkaline developer or a ketone organic solvent for 60 seconds to develop the liquid crystalline monomer only in the reflective display area. The polymer remains. Thereby, the retardation layer 20 made of the liquid crystalline monomer polymer is formed.

In the liquid crystal display device 10 of the present embodiment, the retardation layer 20 is provided only in the reflective display region R, and the pixel electrode 23 made of a transparent conductive film such as ITO is provided so as to cover the retardation layer 20. Is formed, and an alignment film 24 made of polyimide or the like is laminated so as to cover the pixel electrode 23. Further, the lower polarizing plate 28 is provided on the outer surface side of the lower substrate 13, and the conventional retardation plate is not provided.

On the other hand, on the inner surface side of the upper substrate 14 made of a transparent material such as glass or plastic, a common electrode 32 made of a transparent conductive film such as ITO and an alignment film 33 made of polyimide are sequentially laminated. . Further, the upper polarizing plate 36 is provided on the outer surface side of the upper substrate 14, and the conventional retardation plate is not provided. Although not shown, a color filter having R (red), G (green), and B (blue) dye layers is provided on the inner surface of the upper substrate.

The backlight 12 has a light source 37, a reflection plate 38, and a light guide plate 39. The lower surface of the light guide plate 39 (the side opposite to the liquid crystal panel 1) transmits through the light guide plate 39. A reflection plate 40 for emitting light toward the liquid crystal cell 11 side is provided.

The display principle of the liquid crystal display device 10 of the present embodiment will be described below with reference to FIG. First, when performing dark display, a state in which a voltage is applied to the liquid crystal layer 16 (a selection voltage applied state) is set, and the phase difference in the liquid crystal layer 16 is set to 0 (no phase difference). In the reflective display, the upper polarizing plate 36
When the transmission axis of the upper polarizing plate 36 is perpendicular to the paper surface, the light incident from above passes through the upper polarizing plate 36, becomes linearly polarized light perpendicular to the paper surface, and passes through the liquid crystal layer 16 as it is. Then, the linearly polarized light perpendicular to the paper surface is converted into the lower substrate 13
A phase difference of ¼ wavelength is imparted by the upper phase difference layer 20, and after passing through the phase difference layer 20, it becomes counterclockwise circularly polarized light. Next, when this circularly polarized light is reflected on the surface of the semi-transmissive reflection layer 18, the rotation direction is reversed to become clockwise circularly polarized light, which after passing through the retardation layer 20 again becomes linearly polarized light parallel to the paper surface and remains as it is. In this state, the light is transmitted through the liquid crystal layer 16. here,
Since the upper polarizing plate 36 has a transmission axis perpendicular to the paper surface,
The linearly polarized light parallel to the paper surface is absorbed by the upper polarizing plate 36 and does not return to the outside (observer side), resulting in a dark display.

On the other hand, in transmissive display, the light emitted from the backlight 12 is linearly polarized light parallel to the paper surface after passing through the lower polarizing plate 28 when the transmission axis of the lower polarizing plate 28 is parallel to the paper surface. Therefore, the light passes through the liquid crystal layer 16 as it is. This light is similar to the reflection mode in that the upper polarizing plate 36
As it is absorbed by, it becomes a dark display.

Next, when performing bright display, the liquid crystal layer 16
Voltage is not applied to (non-selection voltage applied state),
The phase difference between the reflective display region R and the transmissive display region T is 1
/ 4 wavelength. In the reflective display, the linearly polarized light which is transmitted through the upper polarizing plate 36 and is perpendicular to the paper surface is
A phase difference of 1/4 wavelength is given by 6 and passes through the liquid crystal layer 16 and reaches the surface of the phase difference layer 20 to become counterclockwise circularly polarized light. Then, after passing through the phase difference layer 20, it becomes linearly polarized light parallel to the paper surface, is reflected on the surface of the semi-transmissive reflection layer 18 in the same polarization state, and when transmitted through the phase difference layer 20 again, it becomes counterclockwise circularly polarized light. Return. Next, when this light passes through the liquid crystal layer 16 again, it returns to linearly polarized light perpendicular to the paper surface, passes through the upper polarizing plate 36 having a transmission axis perpendicular to the paper surface, returns to the outside (observer side), and becomes bright. Will be displayed.

On the other hand, in the transmissive display, linearly polarized light emitted from the backlight 12 and transmitted through the lower polarizing plate 28 and parallel to the paper surface is given a phase difference of ¼ wavelength by the liquid crystal layer 16 and the liquid crystal layer 16 is provided. When it passes through, the light becomes circularly polarized light in the counterclockwise direction, and about half of the amount of light is transmitted through the upper polarizing plate 36 having a transmission axis perpendicular to the paper surface to return to the outside, resulting in a bright display.

In the transmissive display, the semi-transmissive reflective layer 1 of the linearly polarized light which is transmitted through the lower polarizing plate 28 and is parallel to the paper surface.
The light reflected on the back surface of 8 is transmitted through the lower polarizing plate 28 as it is, returns to the backlight 12, is reflected by the reflection plate 40 on the lower surface of the backlight 12, and is emitted toward the liquid crystal cell 11 again. The light reflected on the back surface of the reflective layer 18 can be reused to contribute to the transmissive display.

In the liquid crystal display device 10 of the present embodiment, the retardation layer 20 having the phase difference of ¼ wavelength is provided only in the reflective display region R on the inner surface of the lower substrate 13, so that the conventional liquid crystal display device is obtained. While enabling the same operation as
Both the upper and lower retardation plates of the liquid crystal cell used in the conventional device shown in FIG. 7 can be eliminated. Therefore, the liquid crystal cell can be thinned.

[Second Embodiment] The second embodiment of the present invention will be described below.
The embodiment will be described with reference to FIG. FIG. 3 is a sectional view showing a schematic configuration of the liquid crystal display device of the present embodiment.
The basic configuration of the liquid crystal display device of the present embodiment is the same as that of the first embodiment, and the only difference is that a reflective polarizing plate is added to the outer surface side of the lower substrate. Therefore, in FIG. 3, the same components as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

The liquid crystal display device 50 of this embodiment is shown in FIG.
As shown in, the reflective polarizing plate 51 is provided on the outer surface side of the lower substrate 13, more specifically, on the outer surface side of the lower polarizing plate 28. The reflective polarizing plate 51 has a transmission axis that transmits linearly polarized light in a predetermined direction, and has a function of reflecting linearly polarized light in a direction orthogonal to the transmission axis. The reflective polarizing plate 51 is
The transmission axis is arranged so as to be substantially parallel to the transmission axis of the lower polarizing plate 28. As the reflective polarizing plate 51, for example, D
-BEF (trade name, manufactured by Sumitomo 3M Limited), PCF
(Trade name, manufactured by Nitto Denko Corporation, JP-A-10-31923)
No. 5) and the like are used.

Also in the liquid crystal display device 50 of the present embodiment, the transmissive display can be made brighter than in the conventional case.
It is possible to obtain the same effects as those of the first embodiment such that a display with high contrast can be obtained, the number of parts can be reduced, and the device can be made thin.

Further, in the first embodiment, when the light from the backlight 12 is incident on the lower polarizing plate 28 in the transmissive display, only the linearly polarized light which matches the transmission axis of the lower polarizing plate 28 is transmitted, and Since the other linearly polarized light was absorbed by the lower polarizing plate 28, this light could not be used for display. On the other hand, in the case of the present embodiment, the light from the backlight 12 is incident on the reflective polarizing plate 51 before being incident on the lower polarizing plate 28, so in the first embodiment, the lower polarizing plate 28 is used. The linearly polarized light that was absorbed by the light is reflected by the reflective polarizing plate 51 before that, and this light can be reused and used for transmission display. Therefore, in addition to the effect that the light reflected on the back surface of the semi-transmissive reflective layer 18 can be reused for display, the light emitted from the backlight 12 is reflected by the lower polarizing plate 28.
In combination with the effect of not being absorbed by, the transmissive display can be made brighter than in the first embodiment.

[Electronic Equipment] Examples of electronic equipment equipped with the liquid crystal display device of the above-described embodiment will be described. FIG. 4 is a perspective view showing an example of a mobile phone. In FIG. 4, reference numeral 1000 indicates a mobile phone main body, and reference numeral 1001 indicates a liquid crystal display unit using the above liquid crystal display device.

FIG. 5 is a perspective view showing an example of a wrist watch type electronic device. In FIG. 5, reference numeral 1100 indicates a watch body, and reference numeral 1101 indicates a liquid crystal display unit using the above liquid crystal display device.

FIG. 6 is a perspective view showing an example of a portable information processing device such as a word processor and a personal computer. In FIG. 6, reference numeral 1200 is an information processing apparatus, reference numeral 1202 is an input unit such as a keyboard, reference numeral 1204 is an information processing apparatus main body, and reference numeral 1206 is a liquid crystal display unit using the above liquid crystal display device.

Since the electronic devices shown in FIGS. 4 to 6 are provided with the liquid crystal display unit using the liquid crystal display device of the above-described embodiment, the electronic device having the display unit capable of obtaining a bright display in the transmission mode is realized. can do.

The technical scope of the present invention is not limited to the above-mentioned embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the retardation in the retardation layer on the reflective display region is set to ¼ wavelength, the retardation of the liquid crystal layer when the selective voltage is applied is 0 in both the reflective display region and the transmissive display region, and the non-selective voltage is set. The phase difference of the liquid crystal layer during application was set to 1/4 wavelength in the reflective display region and the transmissive display region. This setting makes the transmissive display brightest and the contrast most improved, but the phase difference of each part does not necessarily have to be the above setting, and at least it is possible to make the transmissive display brighter than in the past. is there.

Further, in the above-described embodiment, the positive type liquid crystal is used, the initial state is horizontal alignment, the phase difference is 0 when voltage is applied, and the phase difference between the reflective display area and the transmissive display area is 1/4 wavelength when no voltage is applied. However, conversely to this, a negative type liquid crystal is used, and the initial state is vertical alignment with a phase difference of 0 when no voltage is applied, and a phase difference of the reflective display area and a phase difference of the transmissive display area when a voltage is applied. Can also be configured to have a quarter wavelength. Further, the present invention is not limited to the passive matrix type transflective color liquid crystal display device as in the above embodiment, but can be applied to an active matrix type liquid crystal display device of monochrome display.

[0052]

EXAMPLES In order to demonstrate the effect of the present invention, the present inventors actually manufactured a liquid crystal display device having the constitution according to the present invention, and measured the transmittance and the reflectance. The results are reported below.

As the liquid crystal display device of Example 1, the liquid crystal display device having the configuration of the above-described embodiment shown in FIG. 1 was produced.
As a panel configuration, the number of dots is 160 × (120 × 3
(RGB)), the dot pitch is 240 μm × (80 μm
× 3 (RGB)), and the area of the opening to be the transmissive display area was 68 μm × 22 μm (however, two openings were formed per dot).

A liquid crystal display device in which the configuration of the panel is the same as that of the liquid crystal display device of Example 1 and a reflective polarizing plate is provided on the outer surface side of the lower polarizing plate (the liquid crystal display device of the second embodiment shown in FIG. 3). ) Was prepared, and this was designated as Example 2.

As the liquid crystal display device of Conventional Example 1, a liquid crystal display device having the conventional structure shown in FIG. 7 was manufactured. The configuration of the panel was the same as that of the liquid crystal display device of Example 1.

A liquid crystal display device having the same structure as that of the liquid crystal display device of Conventional Example 1 and having a reflective polarizing plate provided on the outer surface of the lower polarizing plate was prepared.

Table 1 shows the results obtained by measuring the transmittance and the reflectance of each of these four samples under certain conditions.

[0058]

[Table 1]

As shown in Table 1, the reflectance is 4
There is no significant difference between the two samples, and it can be said that the brightness of the reflective display in the liquid crystal display device of the present invention is equivalent to the conventional level.
On the other hand, regarding the transmittance, the conventional example 1 and the example 1,
Alternatively, comparing the conventional example 2 with the example 2, 1.5% was 2.1% and 2.4% was 3.8%, both of which were about 1.5-fold increase. From this result, in the configuration of the present invention, the effect of allowing the light reflected on the back surface of the semi-transmissive reflective layer to be reused can make the transmissive display brighter while maintaining the brightness of the reflective display as compared with the conventional case. Was demonstrated.

Further, comparing Example 1 and Example 2,
The transmittance increased from 2.1% to 3.8%. From this result, by inserting the reflective polarizing plate between the backlight and the lower polarizing plate, the utilization efficiency of the backlight light is improved,
It was demonstrated that the transmissive display can be brightened.

[0061]

As described above in detail, according to the structure of the present invention, the phase difference plates conventionally provided on the upper and lower surfaces of the liquid crystal cell can be eliminated, and the structure is simplified.
It is possible to realize a thin liquid crystal display device. Also,
The backlight light reflected on the back surface of the reflective layer can be recycled, and the brightness during transmissive display can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining the operation principle of the liquid crystal display device shown in FIG.

FIG. 3 is a sectional configuration diagram of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 4 is a perspective view showing an example of an electronic device according to the present invention.

FIG. 5 is a perspective view showing another example of an electronic device according to the present invention.

FIG. 6 is a perspective view showing still another example of an electronic device according to the present invention.

FIG. 7 is a cross-sectional configuration diagram of a conventional liquid crystal display device.

FIG. 8 is an explanatory diagram for explaining the operation principle of the liquid crystal display device shown in FIG. 7.

[Explanation of symbols]

Liquid crystal display device 11 Liquid crystal cell 12 backlight 13 Lower substrate 14 Upper substrate 16 Liquid crystal layer 18 Semi-transmissive reflective layer 18a opening 20 Retardation layer 28 Lower polarizing plate 36 Upper polarizing plate 51 reflective polarizing plate R reflective display area T transparent display area

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H049 BA02 BA05 BA06 BA07 BB03                       BB63 BC22                 2H091 FA02Y FA11Y FA15Y FA23Z                       FA42Z FB02 FB07 FB08                       FC02 FC10 FC26 FC29 FC30                       FD04 FD06 FD12 FD22 FD23                       FD24 GA03 GA16 HA10 LA03                       LA11 LA12 LA13 LA15 LA16

Claims (8)

[Claims] 1. A liquid crystal layer is sandwiched between an upper substrate and a lower substrate arranged to face each other, and an upper polarizing plate and a lower polarizing plate are provided above and below the liquid crystal layer, and one dot is formed. A transflective liquid crystal display device having a reflective display region and a transmissive display region, wherein a reflective layer is provided in the reflective display region, and a retardation layer is provided on the reflective layer. A liquid crystal display device characterized by the above. 2. The retardation imparted to the transmitted light by the retardation layer is approximately ¼ wavelength, and the retardation imparted to the transmitted light by the liquid crystal layer is substantially zero due to a change in voltage application state. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is switched between a wavelength of 1/4 wavelength and a wavelength of approximately 1/4 wavelength. 3. The liquid crystal display device according to claim 1, wherein the retardation layer is made of polymer liquid crystal. 4. The retardation layer is formed by photopolymerizing a liquid crystalline monomer.
The liquid crystal display device according to item 2. 5. The reflective polarizing plate having a transmission axis substantially parallel to the transmission axis of the lower polarizing plate is provided on the outer surface side of the lower substrate. The liquid crystal display device according to item 1. 6. The method of manufacturing a liquid crystal display device according to claim 1, wherein a step of forming a reflective layer in a region corresponding to the reflective display region on the lower substrate, a polymer liquid crystal layer, a photosensitive resin layer After that, the photosensitive resin layer is patterned using a photolithography method, and the polymer liquid crystal layer is etched by using the patterned photosensitive resin layer as a mask to locally leave the polymer liquid crystal layer. Thereby forming a retardation layer made of the polymer liquid crystal layer above the reflective layer. 7. The method of manufacturing a liquid crystal display device according to claim 1, wherein a step of forming a reflective layer in a region corresponding to the reflective display region on the lower substrate, and a layer of a liquid crystalline monomer are formed. After that, by locally photopolymerizing the liquid crystalline monomer using a photolithography method to form a liquid crystalline monomer polymer,
And a step of forming a retardation layer made of the liquid crystalline monomer polymer above the reflective layer. 8. An electronic apparatus comprising the liquid crystal display device according to claim 1. Description: