JPH10123549A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate light leakage from an alignment area without increasing a manufacturing process. SOLUTION: Alignement marks 2a, 2b are provided on a light shield part 7 formed around an effective display area 8. Further, transparent electrodes 3a, 3b and an oriented film 30 are provided on the alignment marks 2a, 2b. The transparent electrodes 3a, 3b perform film-forming of ITO and pattering in the same process as the electrode of the effective display area 8, and the oriented film 30 is formed also in the same process as the effective display area 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display device having an alignment mark used when two substrates are bonded to each other.

[0002]

2. Description of the Related Art The basic structure of a liquid crystal display device generally comprises a substrate provided with electrodes for switching liquid crystals, a counter substrate, and a liquid crystal composition sandwiched between these two substrates. In addition to this basic configuration, there is a type in which a color filter is mounted for performing color display, and a polarizing plate is installed depending on a liquid crystal display mode to be adopted.

As a liquid crystal display device using a polarizing plate, T
The N (twisted nematic) mode is best known. In this display mode, two polarizers whose polarization directions are orthogonal to each other are arranged on the surfaces of the two substrates, respectively, and a nematic liquid crystal is sandwiched between the two substrates, so that the light enters from one substrate side. The twisted light is twisted along the arrangement of the liquid crystal molecules having optical anisotropy, and transmits through the polarizing plate on the other substrate side. In this liquid crystal display element, when a voltage of sufficient intensity is applied to the liquid crystal layer, the liquid crystal is aligned in a state where the long axis of the molecule is aligned with the direction of the electric field, so that the light is shielded by the polarizing plate on the emission side. Will be.

In manufacturing such a liquid crystal display device, there is a method of forming alignment marks on both substrates in advance in order to bond two substrates with high accuracy. More specifically, a plurality of alignment marks are formed outside the effective display area of each substrate, and alignment is performed by optically determining whether the alignment marks of both substrates match. According to this method, the alignment mark formed outside the effective display area becomes unnecessary after bonding, so that the portion of the substrate on which the alignment mark is placed is usually cut and discarded. However, such a dividing process is performed only for cutting off the alignment mark, and causes a great loss in cost and time.

[0005] In order to eliminate such a dividing process,
For the purpose of preventing light leakage from the outer periphery of the effective display area, on a light shielding film provided so as to surround the effective display area,
A technique for arranging an alignment mark is known. By arranging the alignment marks on the light-shielding film in this way, the above-described dividing processing is not required, and the substrate can be used without waste. In this method, an alignment mark including a light-transmitting portion and a non-light-transmitting portion is formed on a light-shielding film. As an example, the patterns of the two alignment marks formed at the corresponding positions on each of the substrates are such that each pattern covers each other's translucent portion when the alignment is performed accurately. Since they overlap, they function as complete light-blocking parts when viewed from outside the substrate. At the time of alignment, the degree of overlap between the patterns of the two alignment marks is optically determined. However, even if there is a slight misalignment, light leakage will occur, resulting in observational problems. Further, in another example, even if the patterns of the two corresponding alignment marks overlap each other, the alignment marks are formed so that the light-transmitting portion remains.

Therefore, as a method for solving the problem caused by light leakage from the alignment mark, for example,
Japanese Patent Application Laid-Open No. 8-43806 proposes the following methods (1) to (3). In addition, FIG.
(B) corresponds to the following methods (1) and (2), respectively. That is, according to the above publication, (1) the light shielding layer 110 for shielding the portion (alignment region) where the alignment marks 102a and 102b are formed from light.
(2) alignment mark 102 is disposed on at least one surface of glass substrate 101a or 101b.
a, 102b of the glass substrate 101a,
The liquid crystal composition is not interposed by sandwiching the transparent member 120 between the substrates 101b, or (3) after the alignment treatment on the alignment film on the substrate, only the alignment film on the alignment mark is aligned by laser irradiation. The alignment region is shielded from light, or a process that does not have optical anisotropy is performed, such as eliminating the function.

[0007]

However, according to the method (1), the light shielding layer 110 for shielding light is used.
According to the method (2), the step of disposing the transparent member 120 between the substrates, and according to the method (3), laser irradiation is performed only on the alignment film in the alignment region. However, since it is necessary to newly provide each of the steps described above, there has been a problem that the manufacturing cost is increased.

The present invention has been made to solve such problems, and an object of the present invention is to provide a liquid crystal display device which can eliminate light leakage from an alignment region without providing a new process. Is to provide.

[0009]

The liquid crystal display device of the present invention has a pair of alignment marks formed on each of a pair of insulating substrates, the pair of alignment marks facing each other, and the pair of alignment marks. In a liquid crystal display element having liquid crystal interposed therebetween, a pair of electrodes are provided so as to cover each of the pair of alignment marks, and the liquid crystal interposed between the alignment marks is driven by the pair of electrodes. Characterized by
Thereby, the above object is achieved.

[0010] It is preferable that the alignment mark is formed on a light shielding area surrounding an effective display area.

It is preferable that the electrode is equal to or larger than the light transmitting portion of the alignment mark.

Hereinafter, the operation of the above configuration will be described.

According to the first aspect of the present invention, there is no need to arrange the alignment mark outside the effective display area, and the electrodes provided in the alignment area can be formed by the same process as the electrodes in the effective display area. Therefore, light leakage from the alignment region can be efficiently prevented without newly adding a process.

According to the second aspect of the present invention, even if an alignment mark is arranged on the light-shielding film, light leakage can be reliably prevented.

According to the third aspect of the present invention, the size of the electrode formed on the alignment mark is large enough to cover at least the translucent portion of the alignment mark, so that the alignment region can be reliably shielded from light. There is no discomfort.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the liquid crystal display device of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 are schematic diagrams showing a liquid crystal display device of the present invention. FIG. 1 is a sectional view taken along the line AA in the top view of the liquid crystal display element of the present invention shown in FIG.

In FIGS. 1 and 2, a glass substrate 1a
An electrode for driving liquid crystal and an alignment film 30 are formed thereon, respectively, in the effective display area 8 on the first and second substrates 1b, and these two substrates are arranged to face each other. A liquid crystal composition 4 is injected between the two glass substrates 1a and 1b, and the liquid crystal is sealed by a sealing material 5 surrounding the effective display area 8, and at the same time, the glass substrates 1a and 1b are sealed by the sealing material 5. Is supported. A polarizing plate 6 is arranged outside the glass substrates 1a and 1b.

In order to bond the glass substrates 1a and 1b with high accuracy, alignment marks 2a and 2a for positioning are used.
2b is formed. The alignment mark 2b is provided on the light-shielding portion 7 formed around the effective display area 8, and is a light-transmitting pattern. On the other hand, the pattern of the alignment marks 2a is formed on a glass substrate using a light shielding member. In the present embodiment, the pattern of the light-shielding portion 7 and the alignment mark 2b is formed of Cr, but is not limited to this. Other metals such as Ta or a black resin having high light-shielding ability can also be used.

On the alignment marks 2a and 2b,
Further, transparent electrodes 3a and 3b and an alignment film 30 are provided. In the present embodiment, the transparent electrodes 3a and 3b are formed and patterned by ITO in the same process as the electrodes in the effective display region 8, and the alignment film 30 is formed by the same process as the effective display region 8.

Here, an alignment method using the alignment marks 2a and 2b will be described. FIGS. 3A to 3C show enlarged patterns of the alignment marks 2a and 2b.
It is shown in (c). FIG. 3A shows the alignment mark 2a.
FIG. 3B is a top view of FIG.
It is a top view of b. FIG. 3C shows a case where a pair of substrates are adhered to each other and two corresponding alignment marks 2a and 2a.
It is a figure showing the state where b overlapped.

3 (a) and 3 (b), the alignment mark 2a is formed by patterning a Ta thin film on a glass substrate 1a in a rectangular shape, and is smaller than the light transmitting portion of the alignment mark 2b. On the other hand, the alignment mark 2b formed on the other substrate is patterned into a shape in which the light-shielding film 7 is hollowed out in a square, and has a light transmitting property. By optically observing a pattern synthesized by overlapping these alignment marks 2a and 2b, the relative position of the two substrates can be grasped. In the liquid crystal display device of the present embodiment,
When the two substrates are bonded with good pattern accuracy, the two corresponding alignment marks 2a and 2b are
The state is as shown in FIG. That is, the alignment mark 2a overlaps with a state where the alignment mark 2a is located exactly at the center of the light transmitting portion of the alignment mark 2b.

Alignment mark 2 as described above
After aligning and bonding the two substrates using a and 2b, a liquid crystal composition is injected between the substrates, and an injection port (not shown) is sealed. At this time, the liquid crystal composition is also held between the alignment marks 2a and 2b. The alignment marks 2a and 2b have transparent electrodes 3a and 3
b is formed and the alignment region is shielded from light by keeping the voltage constantly applied to the transparent electrodes 3a and 3b.

FIG. 4 shows the liquid crystal molecules 1 in the alignment region.
FIG. 9 is a simplified diagram showing an arrangement of 9 and a state of light transmission. FIG.
(A), (b) is a figure which shows the state at the time of no voltage application and at the time of application, respectively.

As shown in FIG. 4A, when no voltage is applied to the alignment region, a pair of alignment films 30 is formed.
Are oriented in directions different from each other by 90 °,
In accordance with this, the liquid crystal molecules 19 are arranged while twisting between the substrates. Further, since the two polarizing plates 6 are arranged so that the optical axis directions thereof coincide with the alignment processing direction of the alignment film 30, the alignment portion is in a light-transmitting state at the unshielded portion. Therefore, light leakage is observed in the alignment region from outside the substrate, and the observer feels discomfort.

On the other hand, as shown in FIG. 4 (b), when a voltage is applied to the alignment region, the liquid crystal molecules 19 are arranged along the direction perpendicular to the substrate. Light does not pass. Therefore, light leakage from the alignment portion is not observed from outside the substrate, and the observer does not feel uncomfortable.

The transparent electrodes 3a, 3 in the alignment area
The supply of the voltage to b can be performed, for example, by a method as shown in FIG. FIG. 5 is a diagram for explaining voltage supply to the alignment region on the glass substrate 1a side. In FIG. 5, a voltage supply line 10 for an alignment region is taken out from a transparent electrode 3a and extends so as to be adjacent to a voltage supply terminal 9 for an effective display region 8 formed at an end of the substrate. Thus, the voltage supply to the alignment region can be performed using the same method as the voltage supply to the effective display region 8.

On the other hand, the transparent electrodes 3a, 3b and the alignment film 30 provided on the alignment marks 2a, 2b have the same size as the light-transmitting portion of the alignment mark 2b in the present embodiment, and have a position just covering the light-transmitting portion. Formed. The size of the transparent electrodes 3a and 3b is not limited to this, and it is desirable that the size is at least the same as the size of the light transmitting portion when the alignment marks 3a and 3b are bonded. More desirably, in addition to this size, the size is set so as to cover an area in which a margin of a shift allowable in bonding the substrates is taken as a margin. As a result, even if misalignment occurs after alignment, light leakage from the alignment region does not occur.

Further, a thin film transistor (TFT) 11 may be formed in the alignment region. FIG. 6 shows a simplified diagram when the TFT 11 is formed in the alignment region.
FIG. 6 is an enlarged configuration diagram of the alignment mark 2a on the glass substrate 1a side. One alignment mark 2b
Is the same as that described above, and the drawing is omitted. The TFT 11 is a known TFT including a gate electrode, a source electrode, a drain electrode, and a semiconductor layer, and is formed in a pixel in an effective display area.
Since it can be formed by the same process as that (not shown), a new manufacturing process is not added.

Further, in the present embodiment, the liquid crystal display element in which the alignment area is formed on the light-shielding film surrounding the effective display area has been described. However, the present invention is not limited to this. For example, the alignment area is formed inside the effective display area. Even if it is not formed on the light-shielding film, or by having the same configuration as the liquid crystal display element,
It is possible to shield the alignment region from light.

[0031]

According to the liquid crystal display element of the present invention, since the alignment mark is not provided outside the effective display area, a dividing step after bonding is not required, and even if the alignment mark is arranged on the light-shielding film, it is ensured. Light leakage can be prevented. Further, since the electrodes provided in the alignment region can be formed in the same process as the electrodes in the effective display region, light leakage from the alignment region can be effectively prevented without newly adding a process. it can.

[Brief description of the drawings]

FIG. 1 is a schematic view of a liquid crystal display device of the present invention, and is a cross-sectional view taken along line AA of FIG.

FIG. 2 is a top view of the liquid crystal display device of the present invention.

FIG. 3 is a diagram showing a pattern of an alignment mark according to an embodiment of the present invention. (A) is a top view of the alignment mark 2a, (b) is a top view of the alignment mark 2b, and (c) is a state where a pair of substrates are bonded and two corresponding alignment marks overlap each other. FIG.

FIG. 4 is a simplified diagram showing an arrangement of a liquid crystal composition and a state of light transmission in an alignment region. (A), (b) is a figure which shows the state at the time of application of no voltage and at the time of application, respectively.

FIG. 5 is a view showing a method of taking out an alignment mark terminal in the liquid crystal display element of the present invention.

FIG. 6 is a diagram showing a configuration of an alignment mark in which TFTs are arranged.

FIG. 7 is a diagram showing a configuration of a conventional liquid crystal display element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1a, 1b Substrate 2a, 2b Alignment mark 3a, 3b Transparent electrode 4 Liquid crystal composition 5 Sealing material 6 Polarizing plate 7 Shielding film 8 Effective display area 9 Voltage supply terminal (for effective display area) 10 Voltage supply terminal (alignment) Mark) 11 TFT 19 liquid crystal molecule 30 alignment film 101a, 101b glass substrate 102a, 102b alignment mark 110 light shielding layer 120 transparent member 106 polarizing plate

Claims (3)

[Claims] 1. A liquid crystal display device wherein a pair of alignment marks are formed on each of a pair of insulating substrates, and the pair of alignment marks face each other, and a liquid crystal is interposed between the pair of alignment marks. 2. The liquid crystal display device according to claim 1, wherein a pair of electrodes is provided so as to cover each of the pair of alignment marks, and a liquid crystal interposed between the alignment marks is driven by the pair of electrodes. 2. The liquid crystal display device according to claim 1, wherein said alignment mark is formed on a light shielding area surrounding an effective display area. 3. The liquid crystal display device according to claim 1, wherein the electrode is equal to or larger than a light transmitting portion of the alignment mark.