JPH09127477A - Color liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double refraction control type element capable of displaying a bright image. SOLUTION: Pixel electrodes 15 and TFTs 14 are arranged in matrix shape on a TFT substrate 11. A common electrode 17 and a blackmask BM are formed at a counter substrate 12 side. The blackmask BM is formed of a semipermeable film having 40 to 60% light transmitivity and noncoloring character. The TFT substrate 11 and the counter substrate 12 are aligned and are stuck together. Since the blackmask BM is formed of the semitransmissive film, numerical aperture is not reduced too much even if misregistration is generated and the display region is covered with the blackmask BM. In succession, a liquid crystal 13 is poured. Further, a pair of polarizing plates 23, 24 are arranged so that desired color is developed corresponding to the change of orientation state of the liquid crystal 13.

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 capable of full color display, and more particularly to a birefringence control type full color liquid crystal display device.

[0002]

2. Description of the Related Art As a color liquid crystal display device capable of displaying a color image, a color filter type, a birefringence control type and the like are known. Widely used color filter type is
A color image is displayed by absorbing light in a specific wavelength region by a color filter to color transmitted light, and the display is dark, and it is unsuitable as a reflection type color liquid crystal display element.

On the other hand, birefringence control (ECB: electrically
A controlled birefringence type liquid crystal display element
By applying an electric field to the liquid crystal, the molecular alignment of the liquid crystal is changed, the birefringence effect of the liquid crystal layer is changed, and the change in the birefringence effect changes the spectral distribution of the light transmitted through the pair of polarizing plates. The color of is displayed. This type of color liquid crystal display device has a bright display and is suitable for a reflective color liquid crystal display device.

In the birefringence control type liquid crystal display element, when a voltage is applied between the electrodes, a desired voltage is applied to the liquid crystal in a portion facing the electrodes, and a desired color can be displayed, but its peripheral portion is , Shows an electro-optical response different from the part that develops color depending on the applied voltage. For this reason, the display color is different from that of the display area, and thus the purity of the display color and the contrast of the entire display image are deteriorated. This problem is particularly remarkable in the case of an active matrix type birefringence control type color liquid crystal display element capable of displaying a high quality image.

[0005]

To solve this problem, a black mask made of a light-shielding material is arranged in the non-display area so that the display in the non-display area is not leaked to the outside, that is, shielded. It is being appreciated. However, when a black mask is formed on the common electrode side of the active matrix liquid crystal display element, the black mask covers the pixel portion due to misalignment of the upper and lower substrates, that is, a part of the electrodes on the opposing substrate. It will overlap.

In this case, there is a problem that the effective display area of each pixel is reduced and the brightness of the display image is reduced.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a birefringence control type color liquid crystal display element capable of displaying a bright image.

[0008]

In order to achieve the above object, a color liquid crystal display element of the present invention comprises a first substrate on which pixel electrodes and active elements connected to the pixel electrodes are arranged in a matrix. A second substrate which is arranged so as to face the first substrate and has a common electrode which is arranged so as to face the pixel electrode, and is arranged between the first substrate and the second substrate. A liquid crystal whose alignment state changes according to a voltage applied between the pixel electrode and the common electrode, and a liquid crystal which is arranged with the first substrate and the second substrate sandwiched therebetween, and the alignment state of the liquid crystal changes. A pair of polarizing plates arranged so as to display a color corresponding to the above, and a semi-transmissive black mask arranged in the non-display area corresponding to the space between the pixel electrodes.

According to this structure, since the black mask is formed of the semi-transmissive film, even if the first substrate and the second substrate are misaligned with each other, each pixel is exposed through the black mask. Light is emitted to some extent. Therefore, the aperture ratio can be maintained at a value close to the design value.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A birefringence control type liquid crystal display device according to embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) As shown in the sectional view of FIG. 1, a birefringence control type liquid crystal display element 1 is roughly
A pair of transparent substrates 11, 12 and a pair of transparent substrates 11, 1
The liquid crystal 13 sealed by the sealing material SC between the two, the two phase plates 21 and 22 arranged outside the substrate 12, the pair of transparent substrates 11 and 12 and the two phase plates 21 and 22. A pair of polarizing plates 23 and 24, which are sandwiched, and a polarizing plate 2
3 and a reflection plate 25 arranged outside.

The pair of transparent substrates 11 and 12 are made of glass, transparent resin or the like. As shown in FIG. 2, on the lower transparent substrate (TFT substrate) 11, TFTs 14 and pixel electrodes 15 are arranged in a matrix, and further, the TFTs 14 and the pixel electrodes 15 are opposed to each other to form auxiliary capacitances. Capacitance line C
S is arranged.

The gate electrode 14G of the TFT 14 is connected to the corresponding gate line GL, the source electrode 14S is connected to the corresponding pixel electrode 15, and the drain electrode 14D is connected to the data line DL.

FIG. 3 is an enlarged plan view of one pixel of the TFT substrate 11, and the cross sections taken along the lines AA, BB and CC are shown in FIGS. 4 to 6, respectively. Each TFT14
As shown in FIG. 4, a gate electrode 14G formed on the TFT substrate 11, a gate oxide film 31 formed by anodizing the surface of the gate electrode 14G, an insulating film 32 made of SiN or the like, An intrinsic semiconductor layer 33 formed on the insulating film 32, a blocking layer 34 formed on the intrinsic semiconductor layer 33 to protect the channel region, an n-type semiconductor layer 35S connected to the intrinsic semiconductor layer 33, 35D, and chromium layers 36S and 36D arranged on the n-type semiconductor layer,
It is composed of aluminum titanium (AlTi) layers 37S and 37D formed on the chromium layers 36S and 36D. The pixel electrode 15 is formed on the insulating film 32 and corresponds to the source electrode 14S (n-type semiconductor layer 35) of the TFT 14.
S and the chrome layer 36S).

An overcoat layer (protective layer) 38 made of SiN or the like is formed on the ends of the TFT 34 and the pixel electrode 15.
Are formed.

The gate line GL is formed of a film of aluminum titanium or the like formed on the TFT substrate 11, as shown in an enlarged view in FIG. The surface of the gate line GL is anodized to form the insulating layer 41. On the gate line GL, the above-mentioned insulating film 32 that functions as a gate insulating film of the TFT 14 is formed. An overcoat layer 38 is formed on the gate line GL. The overcoat layer 38 protects the gate line GL and extends in a stripe shape.

As shown in an enlarged view in FIG. 5, the auxiliary capacitance line CS is formed of a film of aluminum titanium or the like formed on the TFT substrate 11, and its surface is anodized to form an insulating layer 42. It faces the pixel electrode 15 via the insulating film 32.

The data line DL is, as shown in an enlarged view in FIG. 6, an insulating film 32 formed on the entire surface of the TFT substrate 11.
It is formed of a laminated structure of a chromium film 43 and an aluminum titanium film 44 formed on the above. The drain electrode 14D of the TFT 13 is connected to the data line DL. An overcoat layer 38 is formed on the data line DL. The overcoat layer 38 protects the data lines DL and extends in stripes.

An alignment film 16 is arranged on the entire surface of the pixel electrode 15 and the overcoat layer 38. As shown in FIG. 7D, the surface of the alignment film 16 is subjected to an alignment treatment such as rubbing in a direction 16a at a lower right angle of 45 °.

On the other hand, on the upper transparent substrate (counter substrate) 12, a common electrode 17 facing each pixel electrode 15 is arranged. A common voltage is applied to the common electrode 17.

In the portion of the non-display area on the common electrode 17 corresponding to each of the pixel electrodes 15, FIGS.
As shown in FIG. 6, a black mask BM is formed. An overcoat layer 38 is formed in this non-display area, and the layer thickness of the liquid crystal 13 is thinner than the other portions, and is a region where the color is different from the other areas even when the same voltage is applied. Further, since the display voltage is not applied and the gate signal (voltage of the gate line GL) and the data signal (voltage of the data line DL) are applied, an image different from the image originally desired to be displayed is displayed. It is also a realm. Therefore, a black mask BM is arranged in order to prevent the coloring in these non-display areas from directly appearing on the display surface.

As shown in FIG. 8, the black mask BM is composed of a semi-transparent film having a substantially flat transmittance-wavelength characteristic, and is approximately 30% to 70% (preferably,
40 to 60% of the light is transmitted without coloring. This type of black mask BM can be achieved by forming a thin metal film of chromium or the like forming the black mask BM (for example, 0.1 μ or less). Further, it can be achieved by forming the black mask BM from a resin layer containing a black pigment, a black dye, etc. and adjusting the amounts of the pigment, the dye, etc.

An alignment film 18 is arranged on the entire surface of the common electrode 17 and the black mask BM. The orientation film 18 has a direction 18a shown in FIG. 7D (a direction of 90 ° counterclockwise with respect to the orientation treatment direction 16a of the orientation film 16).
Is subjected to orientation treatment such as rubbing.

The liquid crystal 13 is composed of nematic liquid crystal to which a chiral material is added, and is directed from the TFT substrate 11 to the counter substrate 12 as shown in FIG. 7D according to the alignment treatment applied to the alignment films 16 and 18. Twisted by 90 ° and oriented.

The reflecting plate 25 has a surface 25a shown in FIG.
Hairline treatment is applied in the direction of. Phase plate 21
Is arranged so that the axis (stretching axis) 21a having the largest refractive index on the plane intersects with the horizontal direction H parallel to one side of the substrate in the counterclockwise direction at 113 °, as shown in FIG. 7C. Has been done. As shown in FIG. 7B, the phase plate 22 is arranged such that the axis (stretching axis) 22a having the largest refractive index on the plane intersects the horizontal direction H at 20 ° counterclockwise. . The transmission axis 23a of the polarizing plate 23 intersects the horizontal direction H at 90 °, as shown in FIG. 7 (E).
The transmission axis 24a of the polarizing plate 24 intersects the horizontal direction H at 72 ° counterclockwise as shown in FIG. 7 (A).

In the liquid crystal display device having such a structure,
When a voltage (electric field) is applied between the pixel electrode 15 and the common electrode 17, the alignment (tilt angle) of the liquid crystal molecules changes according to this voltage, and the birefringence of the layer of the liquid crystal 13 changes. For this reason, the linearly polarized light that has passed through the upper polarizing plate 24 is not reflected by the phase plate 2
2, 21 and the liquid crystal 13 are subjected to different birefringence effects for each wavelength, and have different polarization states (elliptically polarized light) while passing through the layer of the liquid crystal 13.

Of the light of each wavelength that has passed through the layer of liquid crystal 13, the polarized component parallel to the transmission axis 23a of the polarizing plate 23 is reflected by the reflection plate 25 and enters the layer of liquid crystal 13 again.
While passing through the layer of the liquid crystal 13, it is again subjected to a birefringence action different for each wavelength, and further subjected to a birefringence action by the phase plates 21 and 22. Therefore, the polarization states of the lights of the respective wavelengths emitted from the phase plate 22 are different from each other. Of the light of each wavelength, only the light of the polarization component parallel to the transmission axis 24a exits the polarizing plate 24. Therefore, the light emitted from the polarizing plate 24 has different intensity for each wavelength, and its intensity distribution changes according to the applied voltage. Therefore, the display color can be changed according to the applied voltage.

The optical axis is set as shown in FIG. 7, the retardation of the phase plate is set to 590 nm, and Δn of the layer of the liquid crystal 13 is set.
FIG. 9 shows a CIE chromaticity diagram when d (product of refractive index anisotropy and layer thickness d) is set to 0.99.

In the portion where the pixel electrode 15 and the common electrode 17 face each other, as shown in FIG. 9, a high-purity color corresponding to the applied voltage is displayed. However, each pixel electrode 15
In the portion where the corresponding overcoat layer 38 is formed, the layer of the liquid crystal 13 is thinner than the other portions and shows optical characteristics different from those of the pixel region (display region), and even when the same voltage is applied. Other areas are areas with different colors. In addition, it is a region that develops a color different from the color originally desired to be displayed, such as when a gate signal or a data signal is applied. When such a color of the non-display area is displayed outside as it is, the purity of the display color and the contrast of the color liquid crystal display element 1 as a whole decrease.

In order to prevent such a situation, the black mask BM is arranged as described above. Since the black mask BM is formed of the semi-transmissive film, the color development (light amount) in the non-display area is attenuated and is recognized by the viewer. Therefore, it is possible to prevent the color development of the non-display area from lowering the purity of the display color of the entire display element 1 and the contrast.

Further, when the TFT substrate 11 and the counter substrate 12 are aligned and bonded to each other via the sealing material SC, a positional shift occurs, and the black mask BM is arranged in the pixel portion (display portion).
The black mask BM is formed of a semi-transmissive film even when it is covered, so that the light of each pixel portion is attenuated but passes through the black mask and is emitted. Therefore, the reduction rate of the opening area of the pixel portion is small. Therefore, a bright image can be displayed even if displacement occurs during assembly, which is particularly effective for a reflective liquid crystal display element.

Next, a method of manufacturing the color liquid crystal display element 1 having the above structure will be described. First, an AlTi film is formed on the TFT substrate 11 and patterned to form the gate electrode 14G, the gate line GL, and the auxiliary capacitance line CS. Next, these surfaces are anodized to form the insulating film 3
1, 41, 42 are formed. Then, a SiN film is formed on the entire surface of the substrate by the CVD method or the like.

An intrinsic semiconductor such as amorphous Si is deposited by the CVD method or the like and patterned to form an intrinsic semiconductor layer 33. A blocking layer 34 made of SiN or the like is formed on the planned channel region of the intrinsic semiconductor layer 33. Subsequently, amorphous silicon or the like to which n-type impurities have been added is deposited by a CVD method or the like, and patterned into electrode shapes to form n-type semiconductor layers 35S and 35D.

ITO or the like is deposited on the entire surface by sputtering or the like, and this is patterned to form the pixel electrode 15. Then, a chromium (Cr) layer and an aluminum titanium (AlTi) layer are sequentially deposited, and these are patterned using the same mask to form the source electrode 14S and the drain electrode 14D and the data line DL.

An insulating film made of SiN or the like is formed on the entire surface of the substrate by the CVD method or the like, and the TFT 14 and the data line D are formed.
The overcoat layer 38 is formed by patterning into shapes corresponding to L and the gate line GL, respectively.

Next, an alignment film 16 made of a polyimide film is formed on the entire surface, and the surface is rubbed in a direction 16a to perform an alignment treatment. This is the end of the process on the TFT substrate 11 side.

On the other hand, on the counter substrate 12 side, an ITO film is deposited on the entire surface of the counter substrate 12 and patterned to form a common electrode 17. Next, a Cr film is thinly formed on the counter substrate 12 by sputtering or the like, and the Cr film is patterned to form a black mask BM. It is also possible to form a black mask BM by applying a resin containing a black color, a content dye or the like on a substrate and patterning the resin.

Next, the common electrode 17 and the black mask BM
An alignment film 18 is formed on the top and an alignment treatment is performed. This is the end of the process on the counter substrate 12 side.

TFT substrate 1 formed as described above
1 or the counter substrate 12 is coated with an uncured sealing material,
Further, spacers are sprinkled. Then, the TFT substrate 11
And the counter substrate 12 are aligned with each other and then bonded. At this time, even if a slight displacement occurs, the black mask BM is formed of a semi-transmissive film. Therefore, even if the black mask BM covers a part of the display area, the transmitted light of each pixel still has the black mask BM. There is no significant reduction in the aperture ratio.

After the sealing material SC is hardened, the liquid crystal 13 is filled in the liquid crystal cell formed by the substrates 11 and 12 and the sealing material SC by a vacuum injection method or the like, and the liquid crystal injection port is sealed, and then the phase is set. Plates 21, 22, polarizing plates 23, 24, reflection plate 2
The color liquid crystal display element 1 is completed by bonding 5 together.

As described above, the birefringence control type color liquid crystal display element 1 having an appropriate aperture ratio can be obtained regardless of the relative displacement between the substrates 11 and 12. In addition,
Although the black mask BM is formed to be smaller than the non-display area in the above description, the black mask BM may be formed to have substantially the same size as the size of the non-display area.

(Second Embodiment) In the first embodiment, the black mask BM is arranged on the counter substrate 12, but it is also possible to arrange the black mask BM on the TFT substrate 11. 10 to 12 show sectional structures taken along the line AA, the line BB, and the line CC shown in FIG. 3 when the black mask BM is arranged on the TFT substrate 11 side.

In the structure shown in FIGS. 10 to 12, the black mask BM is formed on the overcoat layer 38. The black mask BM having such a shape is, for example,
After forming the SiN film for forming the overcoat layer 38,
It can be formed by forming a semi-transmissive film for forming the black mask BM and performing patterning on these films using a common patterning mask. Therefore, the number of steps of photolithography processing can be reduced.

The present invention is not limited to the first and second embodiments described above, and various modifications and applications are possible.
For example, although the present invention is applied to the birefringence control type liquid crystal display element using the TFT as an active element in the above embodiment, the present invention is also applied to the birefringence control type liquid crystal display element using the MIM as an active element. It is possible. Also,
The present invention is also applicable to a passive matrix type birefringence control type liquid crystal display element which does not use an active element.

Further, the transmission axes 23a of the polarizing plates 23 and 24,
The arrangement of the stretching shafts 21a and 22a of the phase plate 24a and the phase plates 21 and 22 may be appropriately changed. In addition, the polarizing plates 23, 2
4 and the phase plates 21 and 22 may be omitted as appropriate. Further, although the present invention is applied to the reflection type birefringence control type color liquid crystal display element in the above-mentioned embodiment, the present invention is also applicable to the transmission type birefringence control type color liquid crystal display element.

[0046]

As described above, according to the present invention, when the black mask is formed on the side of the substrate on which the active elements are formed, it is possible to prevent the aperture ratio from decreasing due to the misalignment of the two substrates. . Further, when the black mask is formed on the counter substrate side, the manufacturing process can be simplified.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a birefringence control type color liquid crystal display element according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a configuration on a TFT substrate side of a birefringence control type color liquid crystal display element according to the first embodiment.

FIG. 3 is an enlarged plan view showing a configuration on the TFT substrate side of the birefringence control type color liquid crystal display element according to the first embodiment.

FIG. 4 is a cross-sectional view taken along line AA of FIG.

5 is a cross-sectional view taken along line BB of FIG.

6 is a cross-sectional view taken along the line CC of FIG.

FIG. 7 shows a transmission axis of a pair of polarizing plates and a stretching axis of a phase plate,
It is a figure which shows the relationship with the direction of alignment processing.

FIG. 8 is a graph showing the relationship between the wavelength and the transmittance of the black mask BM.

9 is a CIE chromaticity diagram of display colors of the birefringence control type color liquid crystal display device shown in FIGS.

FIG. 10 is a sectional view taken along line AA of the liquid crystal display element according to the second embodiment of the present invention.

FIG. 11 is a cross-sectional view taken along line BB of the liquid crystal display element according to the second embodiment of the present invention.

FIG. 12 is a sectional view taken along line CC of the liquid crystal display element according to the second embodiment of the present invention.

[Explanation of symbols]

1 ... Birefringence control type liquid crystal display element, 11 ... TFT substrate,
12 ... Counter substrate, 13 ... Liquid crystal, 14 ... TFT, 15 ...
..Pixel electrode, 16 ... Alignment film, 17 ... Common electrode, 18 ...
-Alignment film, 21 ... Phase plate, 22 ... Phase plate, 23 ... Polarizing plate, 24 ... Polarizing plate, 25 ... Reflecting plate, GL ... Gate line, DL ... Data line, SC ... Seal material, BM ...
・ Black mask

Claims (5)

[Claims] 1. A first substrate in which pixel electrodes and active elements connected to the pixel electrodes are arranged in a matrix, the first substrate is arranged to face the first substrate, and the pixel electrodes are arranged to face the pixel electrode. A second substrate on which the common electrode is formed, and an alignment state according to a voltage applied between the pixel electrode and the common electrode, which is arranged between the first substrate and the second substrate. And a pair of polarizing plates arranged so as to sandwich the first substrate and the second substrate between the first substrate and the second substrate so as to display a color according to a change in the alignment state of the liquid crystal, and the pixel. A color liquid crystal display device, comprising: a semi-transmissive black mask disposed in a non-display area portion corresponding to between electrodes. 2. The non-display area is composed of an area in which a desired color cannot be displayed when a predetermined voltage is applied between the pixel electrode and the common electrode. 1. The color liquid crystal display element according to 1. 3. The black mask comprises a light-shielding film formed in a non-display area portion on a second substrate on which a common electrode is formed, according to claim 1 or 2. Color liquid crystal display device. 4. The black mask comprises an overcoat layer formed on the first substrate to cover the active element, and a light-shielding film formed to be smaller than a non-display area between the pixel electrodes. The color liquid crystal display element according to claim 1, 2 or 3, which is configured. 5. The black mask is 30% to 70% of light.
5. The color liquid crystal display element according to claim 1, wherein the color liquid crystal display element is transparent.