JP2001183618A - Reflection type liquid crystal display device and image display application instrument using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more reduce the failure that a terminal part and a transparent electrode are not electrically or physically connected or that terminals adjacent to each other are short-circuited. SOLUTION: In the reflection type liquid crystal display device provided with a liquid crystal cell 12 having a liquid crystal sealed between a pair of substrates 13 and 19, a polarizing film 10, a sheet of or plural sheets of double refraction films 11a and 11b and a reflection layer 17, a rugged layer 18, the reflection layer 17, a flattened layer 16 and a transparent electrode 14 are layered in this order on the lower substrate 19. The difference between the maximum and minimum heights of the surface of the flattened layer is 0.1 μm or below and the liquid crystal layer has 220 deg.-270 deg. twist angle and 700-1,000 nm retardation value Δ Nlc.dLC.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display device and an image display application device using the same.

[0002]

2. Description of the Related Art With the rapid spread of image display application devices in the field of information communication, such as mobile phones, PHSs, and PDAs (Personal Digital Assistants), anyone can easily access and make calls regardless of time and place. Infrastructure is in place. Since these are premised on mobile applications, lightweight, thin, and low power consumption display elements are required, and currently, liquid crystal display elements are mainly used. A liquid crystal display element performs display by changing the light transmission intensity by driving liquid crystal molecules with an effective voltage of several volts. However, since the liquid crystal is a non-light emitting substance, some other light source is required. It is necessary to supply a very large amount of power to the light source compared to the power for driving the liquid crystal.However, it is necessary to provide a reflective plate below the liquid crystal display element and use a reflective liquid crystal display element that displays using ambient light. Accordingly, a display element with extremely low power consumption and utilizing the inherent characteristics of liquid crystal can be realized. The reflection type liquid crystal display device is becoming indispensable as one of displays of a portable information terminal.

[0003] Also, with the increase in the amount of information, the importance of color display as a display of a portable information terminal has been increasing.
There have been proposed several configurations of a reflective liquid crystal display element for performing color display using a color filter or a birefringence effect.

However, since the reflection type liquid crystal display element performs display using ambient light, there is a problem that the display may be dark depending on an illumination environment. As a countermeasure, several configurations have been proposed in which the shape of the reflection surface is made uneven so that the reflected light is collected in the front direction of the reflection type liquid crystal display element.

FIG. 5 shows the structure of a conventional reflection type liquid crystal display element. Reference numeral 50 denotes a polarizing plate, 51 denotes a birefringent film, 52 denotes a liquid crystal cell, 53 denotes a glass substrate, 54 denotes a transparent electrode, and 55 denotes a transparent electrode. A liquid crystal layer, 56 is a smoothing film, 57 is a reflective metal film, 58 is a protrusion, and 59 is a lower glass substrate.

[0006]

The structure of a reflection type liquid crystal display element used in a conventional image display application device has a structure in which a terminal portion is formed of a concavo-convex shape, a flattening layer, and a transparent electrode, and these are laminated. If the terminal pitch is 65 μm, electrical or physical connection is not established,
There is a problem that a short-circuit between adjacent terminals is likely to occur.

[0007]

In order to solve the above-mentioned problems, a reflection type liquid crystal display device of the present invention has a liquid crystal layer between an upper substrate and a lower substrate, and the upper substrate is provided on one surface. , 1
Having one or more birefringent films and polarizing films, and further having an upper transparent electrode on the other surface of the upper substrate,
The lower substrate has, on one surface, an uneven layer, a reflective layer for reflecting light, lower flattening means for flattening the uneven surface, and connection terminal portions for connection between the lower transparent electrode and an external circuit. The uneven layer is provided on one surface of the lower substrate, the reflective layer is provided on the liquid crystal layer side of the surface having the uneven layer, and the lower flattening means is provided on the liquid crystal layer side of the surface having the reflective layer. The lower transparent electrode is provided on the liquid crystal layer side of the surface having the lower flattening means, and the twist angle of the liquid crystal of the liquid crystal layer is in the range of 220 ° to 270 °,
The upper limit of the dimensional difference in the thickness direction between the convex portion and the concave portion of the surface flattened by the flattening means is 0.1 μm, and the birefringence ΔnL of the liquid crystal.
The retardation of the liquid crystal layer represented by the product ΔnLC · dLC of C and the liquid crystal layer thickness dLC is from 700 nm to 1000 nm
Thus, the connection terminal portion is provided around the lower substrate, and the connection terminal portion and the lower substrate are in contact with each other only through the lower transparent electrode.

As described above, since the terminal portion does not have the uneven layer and the flattening layer, the terminal portion is not electrically or physically connected to the transparent electrode, or the adjacent terminals are short-circuited. Troubles can be further reduced.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) First, Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a reflective liquid crystal display device according to Embodiment 1 of the present invention. In FIG. 1, 10 is a polarizing film (polarizer), 1
1a is a birefringent film (1), 11b is a birefringent film (2), 12 is a liquid crystal cell, 13 is an upper transparent substrate (upper substrate), 14 is a transparent electrode, 15 is a liquid crystal layer, and 16 is a flattening means. Layer, 17 is a reflective layer, 18 is an uneven layer, and 19 is a lower substrate.

FIG. 2 is an optical configuration diagram of the reflection type liquid crystal display device of the first embodiment. 20 is a reference line, 21 is the orientation direction of liquid crystal molecules on the upper substrate, 22 is the orientation direction of liquid crystal molecules on the lower substrate, 23 is the slow axis direction of the birefringent film (1) near the liquid crystal cell, Reference numeral 24 denotes a slow axis direction of the birefringent film (2) on the polarizing film side, and reference numeral 25 denotes an absorption axis direction of the polarizing film. ΦLC0 is the orientation direction 22 of the liquid crystal molecules on the lower substrate 19, φLC is the orientation direction 21 of the liquid crystal molecules on the upper transparent substrate 13, and φF1 is the slow axis direction 23 of the birefringent film (1) 11a. , ΦF2 indicates the angle between the slow axis direction 24 of the birefringent film (2) 11b and φp indicates the angle between the absorption axis direction 25 of the polarizing film 10 and the reference line 20, and the twist direction of the liquid crystal is positive. ΩLC indicates the twist angle of the liquid crystal.

Hereinafter, a detailed configuration of the reflection type liquid crystal display element according to the present embodiment will be described in accordance with a manufacturing procedure. First, a glass substrate is used as the upper transparent substrate 13 and the lower substrate 19, and the transparent electrode 1 is placed on the upper transparent substrate 13.
As 4, a pixel electrode is formed of indium / tin / oxide (ITO). The concavo-convex layer 18 is made of a material that expands and contracts by light irradiation and heat. A light and heat-stretchable resin is applied to the entire surface of the lower substrate 19 by spin coating, and is irradiated with ultraviolet rays at 80 to 100 mJ / cm ^{2, and then} irradiated with a clean oven at 150 mJ / cm ^2.
By performing the heat treatment at ℃, expansion and contraction occur, and the average distance between the convex portions is 1 μm, and the average height difference between the highest portion and the lowest portion of the unevenness is 0.
An uneven layer 18 of 4 μm is formed. The reflective layer 17 was formed by depositing silver thereon by vapor deposition. Further, a SiO ₂ film was applied thereon as the planarizing layer 16 so as to have a thickness of 2 μm, and the maximum height difference of the unevenness on the surface of the planarizing layer 16 was set to 0.08 μm. Then, an indium tin oxide (ITO) is formed on the flattening layer 16 as the transparent electrode 14.
To form a pixel electrode.

The upper transparent substrate 13 and the lower substrate 1
After an alignment film was formed on the transparent electrode 14 formed on the substrate 9, an alignment process was performed by rubbing. Then, a glass fiber is applied to the peripheral portion on the upper transparent substrate 14 by 1.0.
A thermosetting sealing resin mixed with wt% is printed, and resin beads having a predetermined diameter are sprayed on the lower substrate 19 at a rate of 200 / mm ² , and the upper transparent substrate 14 and the lower substrate 19 are bonded to each other. Together, the sealing resin was cured at 150 ° C. Thereafter, a mixed liquid crystal in which a predetermined amount of a chiral agent was mixed into an ester-based nematic liquid crystal having Δn = 0.14 was vacuum-injected, sealed with an ultraviolet curable resin, and then cured by irradiation with ultraviolet light.

On the upper transparent substrate 13 of the liquid crystal cell 12 thus formed, a birefringent film (1) 11a and a birefringent film (2) 11b having predetermined retardation values, respectively, Each was bonded so as to have a predetermined angle. Further, a neutral gray polarizing film (SQ-1852AP manufactured by Sumitomo Chemical Co., Ltd.) that has been subjected to anti-glare (AG) treatment as a polarizing film 11 thereon is applied so that the direction of the absorption axis forms a predetermined angle. Stuck together.

ΦLC0 = −35 °, φLC = 35 °, Ω
LC = 250 °, φF1 = 155 °, φF2 = 95 °,
φp = 35 °, | Rfilm (2) −Rfilm (1) | ≦
When 200 nm is satisfied, when ΔnLC · dLC is changed and the optical characteristics are measured in the reflection mode, in the range of 700 nm to 1000 nm, the reflectance is low and achromatic black display is uniform in the pixel, and the reflectance is high and the achromatic color is achromatic. A normally black mode reflective liquid crystal display device capable of obtaining a white display of the above. This is because there is a retardation difference of the liquid crystal that can sufficiently display white and black.
The reason is that the coloring due to the birefringence effect of the liquid crystal can be compensated.

With respect to the twist angle of the liquid crystal, in the case of simple matrix driving, the duty ratio, which is the number of selectable electrodes, is affected. As the twist angle increases, the duty ratio can be reduced, and the number of selected electrodes can be increased. The number of pixels can be increased. In the present embodiment, it has also been confirmed that by setting the twist angle of the liquid crystal within the range of 220 ° to 270 °, good display can be obtained even when driven at a duty ratio of 1/200 or less.

Here, specifically, ΔnLC · dLC = 85
0 nm, Rfilm (1) = 500 nm, Rfilm (2) = 7
00 nm, φLC0 = −35 °, φLC = 35 °, ΩL
C = 250 °, φF1 = 155 °, φF2 = 95 °, φ
The result of having measured the optical characteristics when p = 35 ° is shown.

The front characteristics were measured at a duty ratio of 1/240. As a result, the contrast is 13.8,
As a result, good characteristics were obtained in which the reflectance of white display in terms of the Y value was 58.5%. It was also confirmed that the color changed from black display to white display to achromatic color. Further, it has been confirmed that the variation in the reflectance within the pixel is within ± 0.2%. As a result, an achromatic black display with a low reflectance and an achromatic white display with a high reflectance are obtained, and a reflective liquid crystal display device with high contrast can be realized.

The retardation value ΔnLC · dLC of the liquid crystal layer and the retardation value Rfilm (i) of the birefringent film used here are the retardation values for light of λ = 550 nm.

(Embodiment 2) Next, Embodiment 2 of the present invention will be described with reference to the drawings. The main configuration and the manufacturing procedure of the reflective liquid crystal display element in the present embodiment are the same as the main configuration and the manufacturing procedure of the reflective liquid crystal display element in the above-described first embodiment, except for the presence or absence of a color filter. Therefore, in the present embodiment, components not particularly described are the same as those in the first embodiment,
The constituent members assigned the same reference numerals as those in the first embodiment have the same functions as those in the first embodiment unless otherwise specified. FIG. 3 shows a second embodiment of the present invention.
2 will be described with reference to the cross-sectional view of the reflective liquid crystal display device and the optical configuration diagram of the reflective liquid crystal display device of FIG. In FIG. 3, reference numeral 30 denotes a color filter. Therefore, FIG. 3A shows a case where a color filter is formed on a first substrate, and FIG. 3B shows a case where a color filter is formed on a second substrate.

Hereinafter, the detailed structure of the reflective liquid crystal display device according to the present embodiment will be described in accordance with the manufacturing procedure. The case of the configuration shown in FIG. After forming the color filter 30 on the upper transparent substrate 13,
Indium / tin / oxide (IT
O) to form a pixel electrode. The case of the configuration shown in FIG. 3B will be described. The uneven layer 18 is made of a heat-stretchable resin made of a material that expands and contracts by light irradiation and heat. Lower substrate 19
An uneven layer 18 is formed thereon using light and heat stretchable resin. After forming the color filter 30 thereon, silver was deposited by vapor deposition to form the reflective layer 17. Further, a flattening layer 16 is provided thereon by applying SiO ₂ so as to have a thickness of 2 μm, and then a pixel electrode is formed of indium-tin-oxide (ITO) as the transparent electrode 14. Here, as a method of forming the color filter 30, a printing method of transferring a pattern formed on a printing plate to a substrate surface via a blanket, or a color filter layer forming resist in which a pigment is dispersed is applied on the substrate, and the substrate is subjected to photolithography. By using the pigment dispersion method to form,
Red, green, and blue stripes were formed.

Hereinafter, in the reflective liquid crystal display device manufactured by the same manufacturing procedure as that described in the first embodiment, the twist angle of the liquid crystal is changed from 220 ° to 27 °.
0 °, and the birefringence ΔnLC of the liquid crystal and the liquid crystal layer thickness d
The retardation value represented by the product ΔnLC · dLC with LC is in the range of 700 nm to 1000 nm.

With such a configuration, a color display can be achieved by using a color filter. In particular, in the case of the configuration shown in FIG. 3B, the level difference of the unevenness on the surface of the flattening layer is reduced by the flattening layer 16 and the color filter 30 as compared with the case where only the flattening layer 16 is used. The effect of increasing the uniformity of the layer thickness is obtained. Therefore, it is possible to obtain a reflective liquid crystal display device having good optical characteristics, which enables a white display and a high contrast with uniform brightness within a pixel to be obtained and enables achromatic black and white display.

The above effectiveness was confirmed by the following examples.

Specifically, ΔnLC · dLC = 850n
m, Rfilm (1) = 500 nm, Rfilm (2) = 700
nm, φLC0 = −35 °, φLC = 35 °, ΩLC =
250 °, φF1 = 155 °, φF2 = 95 °, φp =
The result of having measured the optical characteristics at 35 ° is shown. 1
As a result of measurement as front characteristics at a duty ratio of / 240, favorable characteristics such as a contrast of 14.5 and a reflectance of white display in terms of Y value of 19.1% were obtained. Since the color changes from a black display to a white display to an achromatic color, 16 gradations 40
It was also confirmed that 96 colors can be displayed. It has been confirmed that the variation in the reflectance within the pixel is also within ± 0.1%. As a result, an achromatic black display with a low reflectance and an achromatic white display with a high reflectance are obtained, and a reflective color liquid crystal display device with high contrast can be realized.

The retardation value ΔnLC · dLC of the liquid crystal layer and the retardation value Rfilm (i) of the birefringent film used here are retardation values for light of λ = 550 nm.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to the drawings. The main configuration and the manufacturing procedure of the reflective liquid crystal display element in the present embodiment are the same as the main configuration and the manufacturing procedure of the reflective liquid crystal display element in the first embodiment. Therefore, in the present embodiment, the components which are not particularly described are the same as those in the first embodiment, and the components denoted by the same reference numerals as those in the first embodiment are the same as those in the first embodiment unless otherwise described. It has the same function as the embodiment. FIG. 1 is a cross-sectional view of the reflective liquid crystal display element according to the first embodiment of the present invention, and FIG. 4 is a cross-sectional view of a connection terminal portion on a second substrate of the reflective liquid crystal display element according to the third embodiment of the present invention. This will be described with reference to the drawings. In FIG. 4, reference numeral 40 denotes an anisotropic conductive adhesive, and 41 denotes TAB.

The detailed configuration of the reflective liquid crystal display device according to the present embodiment will be described below in accordance with the procedure.

The entire surface of the lower substrate 19 corresponding to the second substrate is coated with a heat-stretchable resin made of a material that expands and contracts by light irradiation and heat by spin coating, and a display area including a connection terminal portion with an external circuit is provided. Ultraviolet rays were irradiated at 80 to 100 mJ / cm ² using a photomask in which the other area was shielded from light. Next, development was performed for a certain period of time using an organic alkali, and then heat treatment was performed at 150 ° C. in a clean oven to cause expansion and contraction. At this time, an uneven layer 18 having an average distance between the convex portions of 15 μm and an average height difference between the highest and lowest portions of the unevenness of 0.4 μm is formed only in the display area. The reflective layer 17 was formed by depositing silver thereon by vapor deposition. Further, a SiO ₂ film having a thickness of 2 μm is formed thereon as a planarizing layer 16.
m, and the maximum height difference of the unevenness on the surface of the flattening layer 16 was 0.08 μm. Next, ultraviolet light was irradiated using a photoresist and a predetermined photomask, and thereafter, a planarizing layer 16 was formed by an etching process. Thereafter, the reflective layer 17 was formed using a phosphoric acid-based etching solution.

By the above processing, the uneven layer 18, the flattening layer 16, and the reflection layer 17 can be eliminated in the non-display area including the connection terminal area with the external circuit. That is,
The structure is such that the transparent electrode 14 is directly formed on the lower substrate 19 in the connection terminal portion. Thereby, the pitch of the terminal portion connected to the TAB 41 via the anisotropic conductive adhesive 40 can be narrowed. That is, high definition can be realized. For comparison, in the case where the terminal portion has the configuration of the concavo-convex shape 18, the flattening layer 16, and the transparent electrode 14, when the terminal portion pitch is 65 μm, the terminal portion is open and short-circuited with an adjacent terminal. Lower substrate 1 as shown
9. In the case of the configuration of the transparent electrode 14, it has been confirmed that both open and short can be connected without any problem.

In the first to third embodiments, silver is used as the reflective layer 17. However, the present invention is not limited to this. For example, a metal reflective layer containing aluminum as a constituent element may be used. The effect can be obtained.

In the first and second embodiments, the birefringent film has a retardation value of 500 n.
m and 700 nm were used, but the retardation value,
The optical axis angle is not limited to this, and the same effect can be obtained in the configuration of one or more birefringent films.

[0032]

As is apparent from the above description, since the terminal portion has no uneven layer and no flattening layer, the terminal portion is not electrically or physically connected to the transparent electrode. The disadvantage that adjacent terminals are short-circuited can be further reduced, and the industrial value is great.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a reflective liquid crystal display device according to Embodiments 1 and 3.

FIG. 2 is an optical configuration diagram of a reflective liquid crystal display device according to the first and second embodiments.

FIG. 3A is a cross-sectional view of a configuration in which a color filter is formed on an upper substrate in the reflective liquid crystal display device of the second embodiment. FIG. 3B is a sectional view of the reflective liquid crystal display device in the second embodiment on a lower substrate. Sectional view of the configuration with the color filter formed

FIG. 4 is a cross-sectional view of a connection terminal portion of the reflective liquid crystal display element of Embodiment 3 for connection to an external circuit.

FIG. 5 is a cross-sectional view showing a configuration example of a conventional reflective liquid crystal display element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Polarizing film 11a Birefringent film (1) 11b Birefringent film (2) 12 Liquid crystal cell 13 Upper transparent substrate 14 Transparent electrode 15 Liquid crystal layer 16 Flattening layer (flattening means) 17 Reflective layer 18 Uneven layer 19 Lower substrate

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Ogawa Tetsudo 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 2H049 BA06 BA42 BC02 2H089 KA17 QA12 RA10 SA04 SA07 SA12 TA04 TA14 TA15 TA17 2H091 FA08X FA11X FA16Y FB02 FC23 FD09 FD10 GA03 GA06 HA10 KA02 KA10 LA12 LA17

Claims (4)

[Claims] 1. A liquid crystal layer is provided between an upper substrate and a lower substrate. The upper substrate has one or a plurality of birefringent films and a polarizing film on one surface. The other surface has an upper transparent electrode, and the lower substrate has, on one surface, an uneven layer, a reflective layer for reflecting light, a lower flattening means for flattening the uneven surface, a lower transparent electrode, and an external circuit. A connection terminal portion for connection, the uneven layer is provided on one surface of the lower substrate, the reflective layer is provided on the liquid crystal layer side of the surface having the uneven layer, The side flattening means is provided on the liquid crystal layer side of the surface having the reflective layer, and the lower transparent electrode is provided on the liquid crystal layer side of the surface having the lower flattening means, and the twist angle of the liquid crystal of the liquid crystal layer is provided. Is from 220 to 270
Within the range of °, the upper limit value of the dimensional difference in the thickness direction between the convex portion and the concave portion of the surface flattened by the flattening means is 0.1 μm,
The product ΔnL of the birefringence ΔnLC of the liquid crystal and the liquid crystal layer thickness dLC
The retardation of the liquid crystal layer represented by C · dLC is 700
a reflection terminal, wherein the connection terminal portion is provided at a peripheral portion of the lower substrate, and the connection terminal portion and the lower substrate are in contact with each other only through the lower transparent electrode. Liquid crystal display device. 2. A liquid crystal layer is provided between an upper substrate and a lower substrate. The upper substrate has one or more birefringent films and a polarizing film on one surface, and further includes a liquid crystal layer. The other surface has a color filter, an upper flattening means, and an upper transparent electrode, the color filter is provided on the other surface of the upper substrate, and the upper flattening means is a liquid crystal on a surface provided with the color filter. Layer side, the upper transparent electrode is provided on the liquid crystal layer side of the surface provided with the upper flattening means, and the lower substrate has an uneven layer, a reflective layer for reflecting light, and an uneven surface on one surface. It has a lower flattening means for flattening and a lower transparent electrode and a connection terminal portion for connection with an external circuit, and the uneven layer is provided on one surface of the lower substrate,
The reflection layer is provided on the liquid crystal layer side of the surface having the uneven layer, the lower flattening means is provided on the liquid crystal layer side of the surface having the reflection layer, and the lower transparent electrode is flattened. The thickness direction of the convex portions and the concave portions of the surface flattened by the flattening means, when the twist angle of the liquid crystal of the liquid crystal layer is provided on the liquid crystal layer side of the surface having the means. Is 0.1 μm, and the birefringence ΔnLC of the liquid crystal
And the liquid crystal layer thickness dLC, the retardation of the liquid crystal layer represented by the product ΔnLC · dLC is from 700 nm to 1000 nm,
The reflection type liquid crystal display element, wherein the connection terminal portion is provided in a peripheral portion of the lower substrate, and the connection terminal portion and the lower substrate are in contact with each other only through the lower transparent electrode. 3. A liquid crystal layer is provided between an upper substrate and a lower substrate. The upper substrate has one or more birefringent films and a polarizing film on one surface. The other surface has an upper transparent electrode, and the lower substrate has, on one surface, an uneven layer, a reflective layer for reflecting light, a color filter, a lower flattening means for flattening the uneven surface, and a lower transparent electrode. A connection terminal portion for connection to an external circuit, the uneven layer is provided on one surface of the lower substrate, and the reflective layer is provided on the liquid crystal layer side of the surface having the uneven layer. The color filter is provided on the liquid crystal layer side of the surface having the reflective layer, the lower flattening means is provided on the liquid crystal layer side of the surface having the color filter, and the lower transparent electrode is provided on the flat surface. The liquid crystal layer of the liquid crystal layer has a twist angle of 2 Within the range of 20 ° to 270 °,
The upper limit value of the dimensional difference in the thickness direction between the convex portion and the concave portion of the surface flattened by the flattening means is 0.1 μm, and is represented by the product ΔnLC · dLC of the birefringence ΔnLC of the liquid crystal and the liquid crystal layer thickness dLC. Of the liquid crystal layer from 700 nm to 100
0 nm, wherein the connection terminal portion is provided in a peripheral portion of the lower substrate, and the connection terminal portion and the lower substrate are in contact with each other only via the lower transparent electrode. Display element. 4. An image display application device comprising the reflective liquid crystal display device according to claim 1. Description: