MANUFACTURING METHOD OF LIQUID CRYSTAL DISPLAY DEVICE

A manufacturing method of a liquid crystal display device, includes forming sealants on a first substrate, forming the dummy sealants including forming a first straight portion from a first start point and then, forming a second straight portion, thereby forming a first dummy sealant having a first end point overlapping the first start point, and forming a third straight portion from a second start point and then, forming a fourth straight portion, thereby forming a second dummy sealant having a second end point overlapping the second start point, and forming a first air inlet between the first dummy sealant and the second dummy sealant, dropping a liquid crystal material, and disposing a second substrate in a pressure-reduced environment.

DETAILED DESCRIPTION

In general, according to one embodiment, a manufacturing method of a liquid crystal display device, includes: forming sealants each having a closed loop shape surrounding each of a plurality of active areas on a first substrate; forming dummy sealants each located on an outside of the plurality of active areas and having a closed loop shape at a plurality of end portions of the first substrate, said forming the dummy sealants including forming a first straight portion from a first start point and then, with a U-turn being made, forming a second straight portion which is spaced apart from the first straight portion and is parallel to the first straight portion, thereby forming a first dummy sealant having a first end point overlapping the first start point, and forming a third straight portion from a second start point and then, with a U-turn being made, forming a fourth straight portion which is spaced apart from the third straight portion and is parallel to the third straight portion, thereby forming a second dummy sealant having a second end point overlapping the second start point, and forming a first air inlet between the first dummy sealant and the second dummy sealant; dropping a liquid crystal material in an inside surrounded by each of the sealants; and disposing a second substrate such that the second substrate is opposed to each of regions surrounded by the sealants and the dummy sealants of the first substrate in a pressure-reduced environment, and subsequently pressurizing the first substrate and the second substrate by an atmospheric pressure, introducing atmospheric air from the first air inlet into a space between the first substrate and the second substrate, and curing the sealants and the dummy sealants.

According to another embodiment, a manufacturing method of a liquid crystal display device, includes: forming sealants each having a closed loop shape surrounding each of a plurality of active areas on a first substrate; forming dummy sealants each located on an outside of the plurality of active areas and having a closed loop shape at a plurality of end portions of the first substrate, said forming the dummy sealants including forming a first dummy sealant including a first straight portion, a second straight portion which is spaced apart from the first straight portion and is parallel to the first straight portion, a first curved portion connecting one end portion of the first straight portion and one end portion of the second straight portion, and a second curved portion connecting the other end portion of the first straight portion and the other end portion of the second straight portion, and forming a second dummy sealant including a third straight portion, a fourth straight portion which is spaced apart from the third straight portion and is parallel to the third straight portion, a third curved portion connecting one end portion of the third straight portion and one end portion of the fourth straight portion, and a fourth curved portion connecting the other end portion of the third straight portion and the other end portion of the fourth straight portion, and forming a first air inlet between the second curved portion and the third curved portion; dropping a liquid crystal material in an inside surrounded by each of the sealants; and disposing a second substrate such that the second substrate is opposed to each of regions surrounded by the sealants and the dummy sealants of the first substrate in a pressure-reduced environment, and subsequently pressurizing the first substrate and the second substrate by an atmospheric pressure, introducing atmospheric air from the first air inlet into a space between the first substrate and the second substrate, and curing the sealants and the dummy sealants.

According to another embodiment, a manufacturing method of a liquid crystal display device, includes: forming sealants each having a closed loop shape on a first substrate; forming dummy sealants each having a closed loop shape at a plurality of end portions of the first substrate, said forming the dummy sealants including forming at a first end portion a first dummy sealant including a first straight portion, a second straight portion which is spaced apart from the first straight portion and is parallel to the first straight portion, a first curved portion connecting one end portion of the first straight portion and one end portion of the second straight portion, and a second curved portion connecting the other end portion of the first straight portion and the other end portion of the second straight portion, and forming at a second end portion, which is perpendicular to the first end portion, a second dummy sealant including a third straight portion, a fourth straight portion which is spaced apart from the third straight portion and is parallel to the third straight portion, a third curved portion connecting one end portion of the third straight portion and one end portion of the fourth straight portion, and a fourth curved portion connecting the other end portion of the third straight portion and the other end portion of the fourth straight portion, the second dummy sealant being spaced apart from the first dummy sealant; dropping a liquid crystal material in an inside surrounded by each of the sealants; and disposing a second substrate such that the second substrate is opposed to each of regions surrounded by the sealants and the dummy sealants of the first substrate in a pressure-reduced environment, and subsequently pressurizing the first substrate and the second substrate by an atmospheric pressure, introducing atmospheric air into a space between the first substrate and the second substrate, and curing the sealants and the dummy sealants.

An embodiment will be described hereinafter with reference to the accompanying drawings. In the drawings, structural elements having the same or similar functions are denoted by like reference numerals, and an overlapping description is omitted.

FIG. 1is a plan view which schematically shows the structure of a liquid crystal display device1according to an embodiment.

Specifically, the liquid crystal display device1includes an active-matrix-type liquid crystal display panel LPN, and a signal supply source such as a driving IC chip2and a flexible wiring board3which are connected to the liquid crystal display panel LPN.

The liquid crystal display panel LPN is configured to include an array substrate AR as a first substrate, a counter-substrate CT as a second substrate which is disposed to be opposed to the array substrate AR, and a liquid crystal layer LQ which is held between the array substrate AR and the counter-substrate CT. The array substrate AR and the counter-substrate CT are attached by a sealant SE in a state in which a predetermined cell gap is formed between the array substrate AR and the counter-substrate CT. The cell gap is formed by columnar spacers (not shown) which are formed on the array substrate AR or counter-substrate CT. The liquid crystal layer LQ is held in an inside surrounded by the sealant SE in the cell gap between the array substrate AR and the counter-substrate CT.

The liquid crystal display panel LPN includes an active area ACT, which displays an image, in the inside surrounded by the sealant SE. The active area ACT has, for example, a substantially rectangular shape, and is composed of a plurality of pixels PX which are arrayed in a matrix of m×n (m and n are positive integers).

The array substrate AR includes gate lines G extending in a first direction X, source lines S extending in a second direction Y crossing the first direction X, a switching element SW which is electrically connected to the gate line G and source line S and is disposed in association with each of pixels PX, and a pixel electrode PE which is electrically connected to the switching element SW. A counter-electrode CE, which is opposed to each pixel electrode PE via the liquid crystal layer LQ, is provided, for example, on the counter-substrate CT.

Although a description of the detailed structure of the liquid crystal display panel LPN is omitted, the liquid crystal display panel LPN is configured such that a mode which mainly uses a vertical electric field, such as a TN (Twisted Nematic) mode, an OCB (Optically Compensated Bend) mode or a VA (Vertical Aligned) mode, or a mode which mainly uses a lateral electric field, such as an IPS (In-Plane Switching) mode or an FFS (Fringe Field Switching) mode, is applicable to the liquid crystal display panel LPN. In the structure in which a mode using a lateral electric field is applied, both the pixel electrode PE and counter-electrode CE are provided on the array substrate AR.

The signal supply source, such as the driving IC chip2and flexible wiring board3, is located on a peripheral area PRP on the outside of the active area ACT, and is mounted on a mount portion MT of the array substrate AR, which extends outward from a substrate terminal end CTE of the counter-substrate CT.

The sealant SE is located on the peripheral area PRP between the active area ACT and end portions of the counter-substrate CT. This sealant SE has a closed-loop shape (i.e. is continuous without a break), and is formed, for example, in a substantially rectangular frame shape. Specifically, a filling port for filling a liquid crystal material is not formed in the sealant SE.

The sealant SE is formed of a sealing material such as an ultraviolet-curing resin or a thermosetting resin, and is formed by a method of continuously drawing the sealing material from a start point to an end point with use of a dispenser or the like.

Next, a manufacturing method of the above-described liquid crystal display panel LPN is described.

To begin with, as shown inFIG. 2, a first mother-substrate M1for forming array substrates AR is prepared. The first mother-substrate M1is formed by using a transparent insulative substrate such as a glass substrate. The first mother-substrate M1has a pair of long sides L1and L2, and a pair of short sides S1and S2. A plurality of effective regions EF are formed on the first mother-substrate M1. Each of the effective regions EF corresponds to a region for forming the array substrate AR. The effective region EF includes an active area ACT and a peripheral area PRP. In the active area ACT, various insulation films, switching elements SW, pixel electrodes PE and an alignment film are formed. In the peripheral area PRP, for example, the mount portion MT for mounting the driving IC chip2and flexible wiring board3is formed, although the detailed depiction of these components is omitted.

In addition, “CTL” on the first mother-substrate M1, which is illustrated, denotes cutting lines for cutting the first mother-substrate M1when array substrates AR are individually cut out of the first mother-substrate M1in a subsequent step. Each of the effective regions EF corresponds to a region surrounded by the cutting lines CTL.

Although not illustrated, a second mother-substrate M2for forming a counter-substrate CT is prepared, on the other hand. The second mother-substrate M2has, for example, the same size as the first mother-substrate M1.

Subsequently, as illustrated inFIG. 3, a sealant SE having a closed loop shape, which surrounds each of the active area ACT of the effect region EF, is formed on the first mother-substrate M1. The sealant SE with this shape is formed by continuously drawing a sealing material such that the start point and end point thereof overlap, by using a dispenser. In the sealant SE, a position indicated by a black point in the Figure corresponds to a close portion SEC. Specifically, in the formation of the sealant SE, the drawing of the sealing material is started from a start point that is a position corresponding to the close portion SEC, and the drawing of the sealing material is continuously performed along a direction indicated by an arrow in the Figure so that the sealing material may form a substantially rectangular closed loop surrounding the active area ACT. Then, the drawing of the sealing material is terminated at an end point that is a position corresponding to the close portion SEC. In short, the position of the start point of the drawing of each sealant SE substantially agrees with the position of the end point of the drawing.

In addition, as shown inFIG. 3, dummy sealants DM are formed along a plurality of end portions of the first mother-substrate M1. Each of the dummy sealants DM is formed in a closed loop shape (endless shape) and is located on the outside of the effective region EF (or active area ACT). In the example illustrated, four dummy sealants DM1to DM4are formed on the first mother-substrate M1.

The dummy sealant DM1is formed along a first end portion E1, that is, the long side L1of the first mother-substrate M1, and extends substantially in parallel to the long side L1. The dummy sealant DM1includes a straight portion LN11, a straight portion LN12which is spaced apart from the straight portion LN11and is substantially parallel to the straight portion LN11, a curved portion CM11which connects one end portion of the straight portion LN11and one end portion of the straight portion LN12, and a curved portion CM12which connects the other end portion of the straight line LN11and the other end portion of the straight line LN12. The straight portion LN11and straight portion LN12are linearly formed substantially in parallel to the long side L1. Each of the curved portion CM11and curved portion CM12is formed in a U shape. The curved portion CM11is located near a corner C4at which the long side L1and the short side S2intersect, and the curved portion CM12is located near a corner C1at which the long side L1and the short side S1intersect.

The dummy sealant DM2is formed along a second end portion E2, that is, the short side S1of the first mother-substrate M1, and extends substantially in parallel to the short side S1. The second end portion E2is perpendicular to the first end portion E1. The dummy sealant DM2includes a straight portion LN21, a straight portion LN22which is spaced apart from the straight portion LN21and is substantially parallel to the straight portion LN21, a curved portion CM21which connects one end portion of the straight portion LN21and one end portion of the straight portion LN22, and a curved portion CM22which connects the other end portion of the straight line LN21and the other end portion of the straight line LN22. The straight portion LN21and straight portion LN22are linearly formed substantially in parallel to the short side S1. Each of the curved portion CM21and curved portion CM22is formed in a U shape. The curved portion CM21is located near a corner C2at which the long side L2and the short side S1intersect, and the curved portion CM22is located near the corner C1at which the long side L1and the short side S1intersect.

The dummy sealant DM3is formed along a third end portion E3, that is, the long side L2of the first mother-substrate M1, and extends substantially in parallel to the long side L2. The third end portion E3is parallel to the first end portion E1and is perpendicular to the second end portion E2. The dummy sealant DM3includes a straight portion LN31, a straight portion LN32which is spaced apart from the straight portion LN31and is substantially parallel to the straight portion LN31, a curved portion CM31which connects one end portion of the straight portion LN31and one end portion of the straight portion LN32, and a curved portion CM32which connects the other end portion of the straight line LN31and the other end portion of the straight line LN32. The straight portion LN31and straight portion LN32are linearly formed substantially in parallel to the long side L2. Each of the curved portion CM31and curved portion CM32is formed in a U shape. The curved portion CM31is located near the corner C2at which the long side L2and the short side S1intersect, and the curved portion CM32is located near a corner C3at which the long side L2and the short side S2intersect.

The dummy sealant DM4is formed along a fourth end portion E4, that is, the short side S2of the first mother-substrate M1, and extends substantially in parallel to the short side S2. The fourth end portion E4is parallel to the second end portion E2and is perpendicular to the first end portion E1and third end portion E3. The dummy sealant DM4includes a straight portion LN41, a straight portion LN42which is spaced apart from the straight portion LN41and is substantially parallel to the straight portion LN41, a curved portion CM41which connects one end portion of the straight portion LN41and one end portion of the straight portion LN42, and a curved portion CM42which connects the other end portion of the straight line LN41and the other end portion of the straight line LN42. The straight portion LN41and straight portion LN42are linearly formed substantially in parallel to the short side S2. Each of the curved portion CM41and curved portion CM42is formed in a U shape. The curved portion CM41is located near the corner C4at which the long side L1and the short side S2intersect, and the curved portion CM42is located near the corner C3at which the long side L2and the short side S2intersect.

Like the sealant SE, each of the dummy sealants DM1to DM4with the above-described shapes is formed by continuously drawing a sealing material such that the start point and end point of the drawing overlap, by using a dispenser. In each of the dummy sealants DM1to DM4, a position indicated by a circle in the Figure is a position where the start point and end point of the drawing overlap and corresponds to a close portion DMC. For example, in the dummy sealant DM1, the drawing of a sealing material is started from a start point which is a position corresponding to the close portion DMC. From the start point, the sealing material is drawn substantially parallel to the long side L1, and the straight portion LN11is formed. Then, the sealing material is drawn with a U-turn being made, thereby forming the curved portion CM11. The sealing material is then drawn once again in parallel to the long side L1, thereby forming the straight portion LN12. Then, with a U-turn being made, the sealing material is drawn and the curved portion CM12is formed, and the continuous drawing of the sealing material is terminated at an end point that is a position overlapping the start point. Thereby, the dummy sealant DM1having the closed loop shape is formed. Although not described in detail, the dummy sealants DM2to DM4are formed by similar drawing.

The dummy sealants DM1to DM4are spaced apart from each other. Specifically, one end side of the dummy sealant DM1, that is, the curved portion CM12is spaced apart from one end side of the dummy sealant DM2, that is, the curved portion CM22. The other end side of the dummy sealant DM2, that is, the curved portion CM21is spaced apart from other end side of the dummy sealant DM3, that is, the curved portion CM31. The one end side of the dummy sealant DM3, that is, the curved portion CM32is spaced apart from one end side of the dummy sealant DM4, that is, the curved portion CM42. The other end side of the dummy sealant DM4, that is, the curved portion CM41is spaced apart from the other end side of the dummy sealant DM1, that is, the curved portion CM11.

An air inlet H1is formed between the dummy sealant DM1and dummy sealant DM2(i.e. between the curved portion CM12and curved portion CM22). An air inlet H2is formed between the dummy sealant DM2and dummy sealant DM3(i.e. between the curved portion CM21and curved portion CM31). An air inlet H3is formed between the dummy sealant DM3and dummy sealant DM4(i.e. between the curved portion CM32and curved portion CM42). An air inlet H4is formed between the dummy sealant DM4and dummy sealant DM1(i.e. between the curved portion CM41and curved portion CM11).

The close portions DMC of the dummy sealants DM1to DM4are located near the air inlets H1to H4, respectively. Specifically, each close portion DMC is formed at a location where a relatively wide space can be secured. Alternatively, the close portion DMC of the dummy sealant DM1is located between the other end portion of the straight portion LN11and the other end portion of the straight portion LN12. In the example illustrated, the close portion DMC of the dummy sealant DM1is located near the air inlet H1and is located between the straight portion LN11and curved portion CM12, but the close portion DMC may be located at an intermediate part of the curved portion CM12or may be located between the straight portion LN12and the curved portion CM12. Similarly, the close portion DMC of the dummy sealant DM2is located near the air inlet H1, and the close portion DMC of each of the dummy sealant DM3and dummy sealant DM4is located near the air inlet H3.

Following the above, as illustrated inFIG. 4, on the first mother-substrate M1, a liquid crystal material LM is dropped in an inside (including the active area ACT) surrounded by the sealant SE with respect to each of the effective regions EF. At this time, the liquid crystal material LM is disposed on an alignment film which is formed on the surface of each effective region EF.

Subsequently, as illustrated inFIG. 5, the first mother-substrate M1and second mother-substrate M2are attached. Specifically, the first mother-substrate M1is disposed in a pressure-reduced environment (or a vacuum environment) such as a vacuum chamber, and the second mother-substrate M2is disposed to be opposed to each of the regions surrounded by the sealants SE and dummy sealants DM. In the example illustrated, columnar spacers are formed on the second mother-substrate M2. The columnar spacers SP may be disposed not only in the inside surrounded by each sealant SE, but also on the outside of each sealant SE or in the inside surrounded by the dummy sealants DM.

Then, by properly pressurizing the first mother-substrate M1and second mother-substrate M2, the second mother-substrate M2is put in contact with the sealants SE and dummy sealants DM, and the sealants SE and dummy sealants DM are collapsed between the first mother-substrate M1and second mother-substrate M2. Thereby, the inside region surrounded by the dummy sealants DM becomes a sealed space. In the state in the example illustrated, while a liquid crystal material LM spreads in the inside region surrounded by each sealant SE, a sealed space SC is created in the inside of the dummy sealant DM4.

Thereafter, as illustrated inFIG. 6, by restoring the reduced-pressure environment to the atmospheric-pressure environment, the first mother-substrate M1and second mother-substrate M2are pressurized by the atmospheric pressure, and atmospheric air is introduced from the air inlets H1to H4into the space between the first mother-substrate M1and second mother-substrate M2. InFIG. 6, areas indicated by hatching correspond to the inside regions surrounded by the sealants SE, which include the liquid crystal material and columnar spacers. Areas indicated by half-tone dots correspond to the inside regions surrounded by the dummy sealants DM, which are kept in a pressure-reduced state (or a vacuum state). Specifically, when the pressure is restored to the atmospheric pressure, the atmospheric pressure acts on the peripheries of the first mother-substrate M1and second mother-substrate M2, while the inside regions surrounded by the sealants SE and dummy sealants DM are substantially kept in a vacuum state. Thus, a pressure difference occurs between the inside regions surrounded by the sealants SE and dummy sealants DM and the outside region. By making use of this pressure difference, the first mother-substrate M1and second mother-substrate M2are pressurized.

In particular, since the inside region of each of the dummy sealants DM1to DM4is the sealed space SC having a lower air pressure than the atmospheric pressure, the volume of the sealed space SC contracts so as to make the air pressure in the sealed space SC closer to the atmospheric pressure. Thereby, a strong pressurizing force occurs centering on the sealed space SC, so as to decrease the distance between the first mother-substrate M1and second mother-substrate M2. At this time, since the dummy sealants DM1to DM4are disposed at the four sides of the first mother-substrate M1and second mother substrate M2, a substantially equal in-plane pressure acts on the first mother-substrate M1and second mother-substrate M2.

In the meantime, as shown inFIG. 7, when the resultant structure is opened to the atmospheric pressure, the liquid crystal material LM further spreads in the inside regions surrounded by the sealants SE, and these inside regions are properly collapsed until a desired cell gap is obtained by the columnar spacers SP.

Then, the sealants SE and dummy sealants DM are cured. In the curing process of the sealants SE and dummy sealants DM, a method, such as ultraviolet irradiation or baking under a high-temperature environment, is applied. Thereby, in each of the effective regions EF, the liquid crystal layer LQ is formed between the first mother-substrate M1and second mother-substrate M2.

Thereafter, both the first mother-substrate M1and second mother-substrate M2are cut along cutting lines CTL. Thereby, as shown inFIG. 8, the array substrate AR is taken out of the first mother-substrate M1, the counter-substrate CT is taken out of the second mother-substrate M2, and the liquid crystal display panel LPN, in which the liquid crystal layer LQ is held between the array substrate AR and counter-substrate CT, is fabricated.

According to the present embodiment, each of the plural dummy sealants DM is formed in a closed loop shape between the first mother-substrate M1and second mother-substrate M2which are attached to each other under the pressure-reduced environment. Thus, when the environment is restored from the pressure-reduced environment to the atmospheric-pressure environment, the inside regions surrounded by the dummy sealants DM are kept in the pressure-reduced state. By the effect of the pressure difference between the inside and the outside of the dummy sealant DM, a large pressure acts on both the first mother-substrate M1and second mother-substrate M2in such a direction to collapse the sealants SE and dummy sealants DM. The inside regions surrounded by the sealants SE are properly collapsed until a desired cell gap is obtained. In addition, since the air inlet H is formed between the neighboring dummy sealants DM, atmospheric air is introduced from the air inlet H when the pressure is restored to the atmospheric pressure. Thus, excessive collapse of the region on the outside of the region surrounded by the sealant SE can be suppressed. Thereby, the uniformity in cell gap in each effective region EF can be improved. Therefore, degradation in display quality due to non-uniformity in cell gap can be suppressed, and the manufacturing yield can be improved.

In addition, the air inlet H is formed between the U-shaped curved portions of the neighboring dummy sealants DM. Thus, compared to the case in which an air inlet H is formed at an intermediate part of the straight portion of the dummy sealant, it is possible to suppress the occurrence of such a disadvantage that the air inlet H is locally narrowed and the introduction of atmospheric air is hindered.

The close portion DMC of the dummy sealant DM, which is formed by drawing the sealing material in the closed loop shape, is located at an intermediate part of the curved portion or at a part between the straight portion and the curved portion. Specifically, the close portion DMC is formed near the air inlet H or at a location where a relatively wide space can be secured. Thus, when the dummy sealant DM is collapsed, the line width of the close portion DMC becomes locally greater than the line width of the part at the other location (the straight portion or curved portion), but the spreading to the effective region EF can be suppressed. Therefore, the effective regions EF can be allocated up to the end portions of the first mother-substrate M1, and the manufacturing yield can be enhanced.

Besides, the dummy sealants DM are located, respectively, at the four sides of the first mother-substrate M1and second mother-substrate M2. Thus, when the pressure is restored to the atmospheric pressure, the first mother-substrate M1and second mother-substrate M2are pressurized by a substantially uniform in-plane pressure. Thereby, the uniformity of the cell gap is further enhanced.

The shapes of the dummy sealants DM or the locations of the air inlets H are not limited to the example shown inFIG. 3. For example, as shown inFIG. 9, a plurality of dummy sealants DM each having a closed loop shape may be disposed to be arranged along each of the long sides L1and L2of the first mother-substrate M1. Specifically, the plural dummy sealants DM are linearly arranged in parallel to the long sides L1and L2, and an air inlet H is formed between the dummy sealants DM. In this manner, as regards each dummy sealant DM, by forming each dummy sealant DM with a relatively small length, it becomes possible to prevent breakage of the sealing material while the dummy sealant DM is being formed.

As has been described above, according to the present embodiment, it is possible to provide a manufacturing method of a liquid crystal display device which can improve the uniformity of the cell gap.