JP3218222B2 - Reflective liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reflection type liquid crystal display device having a reflection electrode .

[0002]

2. Description of the Related Art A conventional reflection type liquid crystal display device is of a TN mode or an STN mode, in which a liquid crystal cell sandwiching a liquid crystal between two substrates on which transparent electrodes are formed, and a liquid crystal cell interposed therebetween. And a reflector disposed on the lower substrate outside the polarizer. However, in this configuration, the display is dark because light passes through the polarizing plate four times. The transmittance of one polarizing plate is at most about 45%. At this time, the transmittance of polarized light parallel to the absorption axis of the polarizing plate is almost 0%.
The transmission of vertically polarized light is approximately 90%. Therefore, in this configuration, (0.9) 4 × 50% = 32.8%, and
The reflectance reaches a peak at about 33% even for a black and white panel. In particular, a color liquid crystal display panel display in which a color filter is formed on one substrate in a black and white panel configuration is darker than a black and white panel due to absorption of the color filter. Becomes difficult.

[0003] In order to make the display brighter, there have been proposed some arrangements in which only one polarizing plate is provided above the liquid crystal cell and the liquid crystal cell is sandwiched between one polarizing plate and a reflection plate (for example, see, for example, Japanese Patent Application Laid-Open No. H11-157572. JP-A-07-146469, JP-A-07-8
4252). In this case, since the light passes through the polarizing plate only twice, the reflectance of the monochrome panel is (0.9) 2 × 50% = 4.
0.5%, which is about 23.5 for the configuration of two polarizing plates.
% Reflectance can be expected to improve.

[0004] In addition, a PCGH mode reflection type liquid crystal display panel (see H. Seki: 1996SID, P.614SID96DIGEST) has been proposed as a configuration not using a polarizing plate in order to make the display brighter. The reflectance of this configuration as a monochrome panel is about 66%, and bright display can be expected.

In the configuration using one polarizing plate or no polarizing plate proposed as described above, in order to solve the problem such as parallax due to the thickness of the substrate between the reflecting plate and the liquid crystal, the reflecting plate is used. A metal reflective electrode also serving as an electrode is formed on the lower substrate, and a reflective plate is disposed in the liquid crystal cell. As the material of the metal reflective electrode, there are Al-based and Ag-based materials that are metals having low resistance and high reflectivity as wiring. Ag-based materials are expensive, but A
Since the l-based material is used as a material for an integrated circuit of a general semiconductor device (that is, a semiconductor device that forms an element on a Si wafer), an Al-based material is practical as a material for a metal reflective electrode.

[0006]

However, among Al-based materials used as metal reflective electrodes, pure Al is the best in terms of low resistance, but has the problem of causing stress migration and electromigration (here. The term “stress migration” refers to bulging and disconnection of a thin film caused by stress, which is mainly caused by heating, and the term “electromigration” refers to disconnection of thin film wiring caused by electrophoresis, which is mainly caused by electric current (especially It is generated by energization under high temperature and high humidity environment).

As an Al-based material for improving the above problems,
Various Al alloys have been developed, but simply alloying increases the resistance and lowers the reflectivity. Therefore, the problem that the stress migration resistance, electromigration resistance, and corrosion resistance are still insufficient. Had.

According to the present invention, a reflective liquid crystal display using a metal reflective electrode has a low resistance as a wiring, a high reflectivity of a display electrode portion, and a high reliability in terms of stress migration resistance, electromigration resistance and corrosion resistance. It is intended to provide a device.

[0009]

According to the present invention, there is provided a reflective liquid crystal display device comprising an upper substrate having an electrode pattern formed by transparent electrodes.
And a metal reflective electrode
A lower substrate on which an electrode pattern is formed, and the transparent electrode
On the electrode pattern and the electrode pattern of the metal reflective electrode
Each of the formed alignment films, and the alignment film of the upper substrate
Liquid crystal having a liquid crystal interposed between the lower substrate and an alignment film
Cell and connected to the liquid crystal cell to drive the liquid crystal cell
The upper substrate and the lower substrate
Is soda lime glass on which a SiO ₂ film is formed,
The electrode pattern of the transparent electrode and the electrode of the metal reflective electrode
Electrode pattern is formed on the SiO ₂ film, further wherein
The electrode pattern of the metal reflective electrode is formed on the lower substrate
A two-layer film of Ti and Al alloy,
The Ti is provided in a lower layer, and the Al alloy is an alloy.
Contains at least one of Zr, Ti, and Ta as a component.
And the content of the alloy component is from 0.1 at%
5 at% .

[0010] According to this configuration, the metal reflective electrode is made of A
By providing Ti in the lower layer of the 1 alloy, a reflective liquid crystal display device having improved stress migration resistance, electromigration resistance, and corrosion resistance can be obtained.

[0011] Then, in the two substrates, on a soda lime glass having an SiO ₂ film is formed, it is preferable that the formation of the electrodes, with this configuration, it is possible to use an inexpensive glass substrate .

Further , an Al alloy contains Zr as an alloy component.
0.1 at% to 5 at least one of Ti and Ta
It is preferable that the Al alloy material of the metal reflective electrode has improved stress migration resistance, electromigration resistance, and corrosion resistance, and has low resistance as a wiring.
A reflective liquid crystal display device having a high reflectance of the display electrode portion can be provided.

[0013] Incidentally, in the electrode of the liquid crystal cell having the above structure of the present invention, the exposed portion of the electrode between the electrodes of the display unit electronic part connecting the electrode portion is coated with a resin. It is preferable that the coating resin having this configuration is an acrylic resin. With such a configuration, it is possible to provide a reflective liquid crystal display device having improved electromigration resistance and corrosion resistance between the electrode surfaces of the exposed metal reflective electrode portions and between the electrode patterns.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1 is a sectional view of a reflection type liquid crystal display device according to a first embodiment. 10 is a polarizing plate, 11 is a polymer film, 12 is a scattering film, 13
Is an upper substrate, 14 and 15 are alignment films, 16 is a transparent electrode, 1
7 is a liquid crystal, 18 is a seal, 19 is a lower substrate, 20 is Al
Alloy electrode, 21 is a Ti electrode, 22 is an acrylic resin, 2
3 is an anisotropic conductive adhesive, 24 is a TAB tape carrier,
25 denotes an LSI chip, and 26 denotes a printed circuit board.

FIG. 2 is a sectional view showing a state in which an Al alloy electrode 20 and a Ti electrode 21 which are metal reflective electrodes are formed on the lower substrate 19 of FIG. 28 is a soda lime glass substrate, and 27 is a SiO2 film. The formation of the SiO2 film 27 on the soda lime glass substrate 28 is for preventing alkali elution into the liquid crystal. On this lower substrate 19,
The Ti film 21 is sequentially laminated at 500 ° and the Al alloy film 20 at 2000 °, and the same electrode pattern is formed by the two layers.
A two-layer mirror-reflection type metal reflection electrode was used. On the lower substrate 19, no thin-film active element such as a transistor is formed.

[0017] Then, in the upper substrate 13, the lower substrate 19
A transparent electrode 16 was formed from indium tin oxide using a substrate in which a SiO ₂ film was formed on a soda lime glass substrate in the same manner as described above. On the upper substrate 13, no thin film active element such as a transistor is formed.

After the electrodes of the upper substrate 13 and the lower substrate 19 are formed, a 5 wt% solution of N-methyl-2-pyrrolidinone of polyimide is printed and cured at 200 ° C.
Alignment films 14 and 15 were formed by performing an alignment treatment by a rotational rubbing method using rayon cloth so as to realize a 50 ° twist STN mode liquid crystal.

In the peripheral portion on the upper substrate 13, 5.
A thermosetting sealing resin 18 mixed with glass fiber having a diameter of 5 μm of 1.0 wt% is printed, and resin beads having a diameter of 5.0 μm are sprayed on the lower substrate 19 at a rate of 200 beads / mm 2. After the substrate 13 and the lower substrate 19 are bonded together and the sealing resin 18 is cured at 150 ° C.,
A liquid crystal 17 obtained by mixing a predetermined amount of chiral liquid crystal with an ester nematic liquid crystal having an LC of 0.16 was injected in vacuum, sealed with an ultraviolet curable resin, and then cured with ultraviolet light.

The upper substrate 1 of the liquid crystal cell thus formed
3, a scattering film 12 is a forward scattering film (trade name: Lumisty) manufactured by Sumitomo Chemical Co., Ltd., and the scattering direction is from 0 ° to 50 ° measured from the film normal.
° scattering film was laminated. Polycarbonate was adhered thereon as the polymer film 11. The polymer film 11 comprises two polymer films having different slow axes. The polymer film on the liquid crystal cell side has a retardation of 0.3 μm and the slow axis is 90 ° with respect to the orientation direction of the upper substrate 13. The upper polymer film has a retardation of 0.5 μm and a slow axis of 45 ° with respect to the orientation direction of the upper substrate 13. Further, as the polarizing plate 10, a neutral gray polarizing plate (manufactured by Sumitomo Chemical Co., Ltd., S
Q-1852AP), which had been subjected to an antiglare (AG) treatment, was affixed so that the absorption axis thereof coincided with the lower slow axis of the polymer film 11.

Further, as the electronic components for driving the liquid crystal cell, a printed board 26 on which the electronic components are mounted and an LSI
Using the TAB tape carrier 24 on which the chip 25 was mounted, the printed circuit board 26 and the TAB tape carrier 24 were connected. Further, the electrodes 20, 21 of the liquid crystal cell are extended to form an extension 100, and the tip 100a of the extension 100 is connected to the end of the TAB tape carrier 24 by an anisotropic conductive adhesive 23. I have.

[0022] In addition, the extension of the electrodes 20, 21 100
The acrylic resin 22 was coated on a part 100b of the extension 100 so that the resin was not exposed to the outside. That is, the portion 1 between the tip 100a of the extension 100 and the seal 18
00b from TUFFY (TF1) manufactured by Hitachi Chemical Co., Ltd.
141).

With this configuration, the achromatic black display with a low reflectance, the achromatic white display with a high reflectance, and the achromatic color from black to white are obtained by simple matrix driving with a 1/240 duty ratio. A normally black mode reflective liquid crystal display device capable of changing display was obtained.

In the metal reflective electrode of such a reflective liquid crystal display device, Z is used as an alloy component of the Al alloy electrode 20.
In the case where each of r, Ti, and Ta is changed from 0 at% to a content exceeding 5 at%, stress migration resistance, electromigration resistance and corrosion resistance as a metal reflective electrode, reflectance, ratio The resistance was checked.

(Example 1) Each of Zr, Ti, and Ta was selected from 0 at% to 5 at%.
Using an Al alloy target and a Ti target up to the contents of over 500 nm, a Ti film is sequentially laminated on a soda lime glass substrate on which a SiO ₂ film is formed by DC magnetron sputtering method at a thickness of 500Å and an Al alloy film at 2000Å. The same electrode pattern was formed with a two-layer film, and a two-layer film mirror-reflection type metal reflective electrode was used as a sample.

After heat-treating the sample at 200 ° C. for 1 hour in the air, the number of hillocks generated on the surface of the stripe pattern was measured to determine the hillock density. The result is shown in FIG. By adding Zr, Ti, and Ta at 0.1 at% or more, the hillock density was significantly reduced, and the stress migration resistance was improved.

[0027] Then, PCT as an environmental acceleration test for the sample: perform (Pressure Cooker Test temperature 105 ° C., pressure 1.2 atm, humidity 100% RH), was evaluated the corrosion resistance of the film. In the surface observation after 60 hours of PCT, the discoloration of the surface occurred in the metal reflective electrode of 0 at% of the alloy content, that is, pure Al, but the content of the alloy was 0.1 a.
Above 5 at% from t%, no abnormalities on the surface were observed. From these results, the corrosion resistance was improved by adding 0.1 at% or more of Zr, Ti, and Ta.

Further , in the configuration of the reflection type liquid crystal display device shown in FIG. 1 described above, the energization test 500h of the reflection type liquid crystal display device was performed in an environment of a temperature of 60 ° C. and a humidity of 90% RH using the metal reflection electrode. Then, the electromigration resistance of the electrode was evaluated. The alloy content is 0 at%, that is, pure A
In the metal reflective electrode of No. 1, disconnection occurred, but when the content of the alloy exceeded 0.1 at% to 5 at%, there was no abnormality such as disconnection and no abnormality on the surface was observed.
From these results, the electromigration resistance was improved by adding 0.1 at% or more of Zr, Ti, and Ta.

From the above results, in the metal electrode having the above structure, in the Al alloy having a content of Zr, Ti, and Ta of 0.1 at% to more than 5 at%, the resistance to stress migration, the resistance to electromigration, and the corrosion resistance And a highly reliable reflective liquid crystal display device can be obtained. This effect is achieved by simultaneously containing two or more of Zr, Ti, and Ta, and having a total amount of 0.1 at% to 5 at%.
% Can be obtained.

(Example 2) With respect to a sample of a metal reflective electrode formed in the same manner as in Example 1, the reflectance of light at a wavelength of 555 nm with high visibility and the specific resistance were measured by a four probe method. FIG. 4 shows the result of the reflectance, and FIG. 5 shows the result of the specific resistance.

As the contents of Zr, Ti and Ta increase, the reflectance decreases and the specific resistance increases. In particular, Z
If the content of r, Ti, and Ta exceeds 5 at%, the reflectance decreases sharply, and the specific resistance sharply increases. For this reason, in order to obtain a reflective liquid crystal display device which is a wiring having low resistance and low resistance variation and a display electrode portion having high reflectance, the content of Zr, Ti, and Ta should be up to 5 at%. I understand. This effect can be obtained even when two or more of Zr, Ti and Ta are simultaneously contained and the total amount thereof is up to 5 at%.

According to Examples 1 and 2, it is preferable that the Al alloy contains at least one of Zr, Ti, and Ta as an alloy component in an amount of 0.1 at% to 5 at%. Thus, the reflection type liquid crystal display device has improved resistance to stress migration, resistance to electromigration, and corrosion resistance of the Al alloy material itself of the metal reflective electrode, low resistance as wiring, and high reflectance of the display electrode portion. be able to.

In the above (Embodiment 1), a substrate on which a thin film active element such as a transistor is not formed is used.
By forming the display electrode portions 20 and 21 of the lower substrate, the electrode portion 100a for connecting the electronic component 25 for driving the liquid crystal cell, and the electrode portion 100b therebetween as a two-layer film of Ti and Al alloy, a thin film is formed. A substrate on which an active element is formed can be used.

[0034] Then, in the (Embodiment 1), Si
Although a soda lime glass substrate with an O ₂ film was used,
An alkali-free glass substrate or a liquid crystal film substrate may be used.

In the above (Embodiment 1), the acrylic resin 22 covers the exposed portion of the electrode 100b between the electrode portion 100a to which the electronic component for driving the liquid crystal cell is connected and the display electrodes 20 and 21. However, it may be covered with another resin such as a silicon-based resin. In addition , as the resin to be coated, an acrylic resin having an effect of suppressing permeation of water is preferable from the viewpoint of improving electromigration resistance.

Further, in the above (Embodiment 1), the mirror type is used as the metal reflection electrode and the scattering film is arranged on the upper substrate, but the metal reflection electrode may be the scattering type.

Further, in the above (Embodiment 1), the reflection type liquid crystal display device for displaying black and white is used. However, a reflection type liquid crystal display device for color display may be used by using a color filter or the like.

In the above (Embodiment 1), the STN
Although the liquid crystal of the mode is used, a configuration of a reflection type liquid crystal display device in which a polarizing plate, a polymer film, or the like is adjusted to the liquid crystal mode using another liquid crystal mode such as a TN mode or a PCGH mode may be used.

In the following, in each embodiment, the same components as those in the first embodiment are denoted by the same reference numerals.

(Embodiment 2) FIG. 6 is a sectional view of a reflection type liquid crystal display device according to a second embodiment. The reflection type liquid crystal display device according to the second embodiment has substantially the same configuration as the reflection type liquid crystal display device according to the first embodiment.
The fifth mounting method is different from the TAB mounting method of the first embodiment in that the COG mounting method is used in the second embodiment.

That is, a printed board 26 on which electronic components (not shown) are mounted, a flexible board 29 and an LS
Using the I chip 25, the printed board 26 and the flexible board 29 are connected, the electrodes 20 and 21 of the liquid crystal cell and the flexible board 29 are connected via the anisotropic conductive adhesive 23, and The electrodes 20, 21 and the LSI chip 25 were connected via an anisotropic conductive adhesive 23.
The liquid crystal cell is driven by the electronic components (not shown) and the LSI chip 25. The electrode portions 200b and 200c between the electrode portion 200a to which the flexible substrate 29 was connected and the electrodes of the display portion were covered with acrylic resins 22 so as not to be exposed to the outside.

Also in the configuration of the second embodiment, 1 /
A simple matrix drive with a duty ratio of 240, the achromatic black display with low reflectance, the achromatic white display with high reflectance, and the normally black mode that can display achromatically changing from black to white A reflection type liquid crystal display device was obtained.

[0043] Then, was described in Examples 1 and 2 of the first embodiment, the same effect also in the metallic reflecting electrodes of the reflection type liquid crystal display device of Embodiment 2 is obtained, Al alloy Preferably contains 0.1 at% to 5 at% of at least one of Zr, Ti, and Ta as alloy components. With such a configuration, stress migration resistance of the Al alloy material itself of the metal reflective electrode is improved. Liquid crystal display device having improved resistance, electromigration resistance and corrosion resistance, low resistance as wiring, and high reflectance of the display electrode portion.

In the above (Embodiment 2), a substrate on which a thin film active element such as a transistor is not formed is used. However, the display electrode portions 20 and 21 on the lower substrate and electronic components for driving the liquid crystal cell are used. If the electrode portion 200a connecting the second electrode 29 and the electrode portions 200b and 200c between them are two-layer films of Ti and Al alloys, a substrate on which a thin film active element is formed may be used.

In the above (Embodiment 2), SiO 2
_Although a soda-lime glass substrate having _two films is used, an alkali-free glass substrate or a liquid crystal film substrate may be used.

In the above (Embodiment 2), the exposed portions of the electrodes 200b and 200c between the electrode portion 200a to which the electronic component for driving the liquid crystal cell is connected and the electrodes 20 and 21 of the display portion are made of acrylic resin. However, another resin such as a silicon-based resin may be used. In addition , as the resin to be coated, an acrylic resin having an effect of suppressing permeation of water is preferable from the viewpoint of improving electromigration resistance.

Further, in the above (Embodiment 2), although the mirror type is used as the metal reflection electrode and the scattering film is arranged on the upper substrate, the metal reflection electrode may be of the scattering type.

In the above (Embodiment 2), the reflection type liquid crystal display device for monochrome display is used. However, a reflection type liquid crystal display device for color display may be used by using a color filter or the like.

In the above (Embodiment 2), the STN
Although the liquid crystal of the mode is used, a configuration of a reflection type liquid crystal display device in which a polarizing plate, a polymer film, or the like is adjusted to the liquid crystal mode using another liquid crystal mode such as a TN mode or a PCGH mode may be used.

[0050]

As described above, according to the reflection type liquid crystal display device of the present invention, a reflection type liquid crystal display device having improved stress migration resistance, electromigration resistance and corrosion resistance can be obtained.

[0051] Then, in the two substrates, on a soda lime glass having an SiO ₂ film is formed, when forming the electrode may be used an inexpensive glass substrate can be suppressed in cost.

Further , the Al alloy contains Zr,
0.1 at% to 5 a of at least one of Ti and Ta
When t% is contained, the anti-stress migration property, electro-migration resistance, and corrosion resistance of the Al alloy material itself of the metal reflective electrode are improved, the resistance as a wiring is low, the reflectance of the display electrode portion is high, and the reflective type. A liquid crystal display device can be obtained.

[0053] Incidentally, in the electrode of the liquid crystal cell, when the electrode portion connecting the electronic components, the resin covering the exposed portion of the electrode present between the electrodes of the display unit and the acrylic resin, a metal reflecting electrode A reflection type liquid crystal display device having improved electromigration resistance and corrosion resistance between the electrode surfaces and electrode patterns in the exposed portions of the present invention can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a reflective liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a state in which a metal reflective electrode is formed on a lower substrate according to the first embodiment of the present invention.

FIG. 3 shows the Z of the Al alloy film of Example 1 of the present invention.
The figure which shows the relationship between the content of r, Ti, Ta and hillock density.

FIG. 4 shows the Z of the Al alloy film of Example 2 of the present invention.
The figure which shows the relationship between the content of r, Ti, and Ta, and a reflectance.

FIG. 5 is a graph showing Z of an Al alloy film according to Example 2 of the present invention.
The figure which shows the relationship between content of r, Ti, Ta and specific resistance.

FIG. 6 is a sectional view of a reflective liquid crystal display device according to a second embodiment of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 10 polarizing plate 11 polymer film 12 scattering film 13 upper substrate 14, 15 alignment film 16 transparent electrode 17 liquid crystal 18 seal 19 lower substrate 20 Al alloy electrode 21 Ti electrode 22 acrylic resin 23 anisotropic conductive adhesive 24 TAB tape Carrier 25 LSI chip 26 Printed circuit board 27 SiO ₂ film 28 Soda lime glass substrate 29 Flexible board 100 Extended section 100a Tip of extended section 100b Part of extended section 200a Electrode section 200b Electrode section 200c Electrode section

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ogawa Tetsudo 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-9-171195 (JP, A) JP-A-3-3 125443 (JP, A) JP-A-5-224225 (JP, A) JP-A-9-133929 (JP, A) JP-A 9-138397 (JP, A) JP-A-2000-47201 (JP, A) ( 58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/1333 G02F 1/1335 G02F 1/1343 G02F 1/1345 G02F 1/136 G09F 9/00-9/46

Claims (1)

(57) [Claims] 1. A an upper substrate formed with an electrode pattern of a transparent electrode, is disposed opposite to the upper substrate, a lower substrate provided with the electrode pattern by the metal reflecting electrode, the transparent
Electrode pattern of electrode and electrode pattern of said metal reflective electrode
And alignment films formed respectively on the emission, distribution of the upper substrate
A liquid crystal cell having a liquid crystal sandwiched between the alignment film of the alignment film and the lower substrate is connected to the liquid crystal cell, and an electronic component for driving the liquid crystal cell, the upper substrate and the lower Substrate formed SiO ₂ film
It was a soda lime glass, conductive electrode pattern and the metal reflection electrode of the transparent electrode
The electrode pattern is formed on the SiO ₂ film, and the electrode pattern of the metal reflection electrode is formed on the lower substrate.
A two-layer film of Ti and Al alloy formed on a plate,
The Ti is provided below the Al alloy , and the Al alloy contains Zr, Ti, and Ta as alloy components.
And the content of the alloy component is from 0.1 at% to 5 at%.
% , A reflective liquid crystal display device.