JP2010008616A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display wherein exfoliation of an alignment film can be prevented even when the alignment film is formed by application using an inkjet system. <P>SOLUTION: The liquid crystal display includes: a first substrate 110 having a surface on which a plurality of first projections 112 are formed, and having a first alignment film 113 formed to cover this surface; and a second substrate 120 having a surface on which a plurality of second projections 121 lower than the first projections 112 are formed, and having a second alignment film 122 formed to cover this surface. The first substrate 110 and the second substrate 120 are disposed facing each other so that tops 114 of the first projections 112 and tops 123 of the second projections 121 are brought into contact with one another, and the first alignment film 113 is thinner than the second alignment film 122. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device.

  In recent years, as described in Cited Document 1, an alignment film in a liquid crystal display device is formed by coating using an inkjet method.

Reference 2 describes that the thickness of the alignment film at the top of the photo spacer is reduced by leveling in order to prevent the alignment film from being peeled in the vicinity of the photo spacer.
JP 2004-126424 A JP 2000-267114 A

  In the application using the ink jet method, in order to stably discharge droplets, the viscosity of the solution to be used must be lowered to some extent. For this purpose, the ratio of the solvent in the solution to be used is increased, and the solid content concentration is lowered. If it does so, the application quantity of the solution per unit area required in order to obtain a predetermined film thickness after drying of a solution will increase.

  FIG. 6 is a schematic diagram showing a process of forming an alignment film on the color filter substrate of the liquid crystal display device using an ink jet method. FIG. 4A shows a state immediately after coating, FIG. 5B shows a state during drying, and FIG.

  In FIG. 5A, a color filter layer 611 and a photo spacer 612 are formed on a color filter substrate 610. Note that only a necessary configuration is shown here for the sake of brevity, but a black matrix, a transparent electrode, an overcoat layer, and the like may be formed on the color filter substrate 610 in addition. Here, reference numeral 613 denotes an alignment film solution applied by an ink jet technique. In the inkjet method, the alignment film solution 613 discharged as droplets lands on the surface of the color filter substrate 610, and adjacent droplets are connected to form a liquid film. Therefore, the surface of the liquid film is waved as illustrated. I'm hitting. As described above, since the application amount of the alignment film solution 613 is large, the photo spacer 612 is buried in the alignment film solution 613.

  When the alignment film solution 613 is dried in this state, the alignment film solution 613 remains on the top portion 614 of the photo spacer 612 as shown in FIG. At this time, a thick portion 613a and a thin portion 613b of the liquid film are formed due to the undulation of the surface of the initial liquid film of the alignment film solution 613 and surface tension.

  When drying is finally completed, an alignment film 615 is obtained as shown in FIG. The top portion 614 of the photospacer 612 has variations such as the formation of a thick portion 615a and a thin portion 615b, but in any case, the alignment film 615 is formed with a certain thickness.

  FIG. 7 is a schematic diagram of a conventional liquid crystal display device 600 using such a color filter substrate 610. The liquid crystal display device 600 has a structure in which a liquid crystal 630 is sandwiched between a color filter substrate 610 and a TFT (Thin Film Transistor) substrate 620. The polarizing plate, various optical films, the backlight, and accessories such as circuit elements formed on the TFT substrate 620 are not shown for the sake of simplicity. The TFT substrate 620 is provided with a pedestal 621 corresponding to the photo spacer 612, and an alignment film 622 is formed similarly to the color filter substrate 610. The height of the pedestal 621 is lower than the height of the photo spacer 612.

  Here, when an external force such as bending or vibration acts on the liquid crystal display device, the photo spacer 612 is bent, or the top portion 614 of the photo spacer 612 and the top portion 623 of the pedestal 621 rub against each other. As shown by, the alignment film 615 may be peeled off and released into the liquid crystal 630. In this case, the alignment of the liquid crystal 630 is disturbed, causing a reduction in image quality.

  The present invention has been made in view of such a viewpoint, and an object of the present invention is to provide a liquid crystal display device capable of preventing the peeling of the alignment film even when the alignment film is formed by coating using an inkjet method. is there.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  (1) A first substrate having a surface on which a plurality of first protrusions are formed and having a first alignment film covering the surface, and a second protrusion lower than the plurality of first protrusions And a second substrate on which a second alignment film covering the surface is formed, and the top of the first protrusion and the top of the second protrusion are in contact with each other As described above, the first substrate and the second substrate are arranged to face each other, and the first alignment film is thinner than the second alignment film.

  (2) In the liquid crystal display device according to (1), the thickness of the first alignment film is 3% or less of the height of the first protrusion.

  (3) In the liquid crystal display device according to (1), the area of the top of the first protrusion is smaller than the area of the top of the second protrusion.

  (4) In (1), the thickness of the first alignment film formed on the top of at least one of the first protrusions is the thickness of the first alignment film formed on the top of at least one other first protrusion. A liquid crystal display device having a thickness different from that of the first alignment film.

  (5) The liquid crystal display device according to (4), wherein the first alignment film is formed by using an inkjet method.

  According to the invention disclosed in the present application, it is possible to provide a liquid crystal display device that can prevent peeling of the alignment film even when the alignment film is formed by coating using an inkjet method.

  FIG. 1 is a schematic diagram showing a liquid crystal display device 100 according to the first embodiment of the present invention.

  The liquid crystal display device 100 has a structure in which a liquid crystal 130 is sandwiched between a color filter substrate 110 that is a first substrate and a TFT substrate 120 that is a second substrate. On one surface of the color filter substrate 110, a color filter layer 111 and a plurality of first protrusions photo spacers 112 are formed, and a first alignment film 113 is formed to cover the surface. Yes. On one surface of the TFT substrate 120, a pedestal 121 that is a plurality of second protrusions is formed, and a second alignment film 122 is formed so as to cover the surface. The photo spacer 112 and the pedestal 121 are disposed so as to face each other, and the width of the gap between the color filter substrate 110 and the TFT substrate 120, that is, the cell, by contacting the top 114 of the photo spacer 112 and the top 123 of the pedestal 121. It defines a gap.

  In addition, in order to make description simple here, illustration and description of various accessories including a polarizing plate are abbreviate | omitted. In addition, the liquid crystal display device 100 according to the present embodiment may use any known driving method such as an IPS (In Plane Switching) method, a VA (Vertical Alignment) method, or a TN (Twisted Nematic) method. .

  As illustrated, the height T1 of the photo spacer 112 is higher than the height T2 of the pedestal 121. Further, the thickness t1 of the first alignment film 113 on the surface of the color filter substrate 110 is thinner than the thickness t2 of the second alignment film 122 on the surface of the TFT substrate 120. The first alignment film 113 is hardly formed on the top portion 114 of the photo spacer 112 or is very thin even if it exists. On the other hand, the second alignment film 122 is formed with a certain thickness on the top 123 of the pedestal 121. The area of the top 114 of the photo spacer 112 is smaller than the area of the top 123 of the pedestal 121.

  As will be described later, the first alignment film 113 is formed by coating using an inkjet method. Although the formation method of the second alignment film 122 is not necessarily limited, the second alignment film 122 can be formed by coating using an ink jet method similarly to the first alignment film.

  With such a configuration, the peeling of the alignment film as described above can be substantially prevented. Although the reason for this is not necessarily clear, it is considered as follows.

  FIG. 2 is a schematic diagram of a state when an external force is applied to the liquid crystal display device 100. As shown in the figure, when an external force is applied to the liquid crystal display device 100, the positions of the color filter substrate 110 and the TFT substrate 120 are slightly shifted. Then, since the photo spacer 112 has an elongated shape, the bending rigidity is low, and it is considered that the photo spacer 112 is deformed as illustrated. On the other hand, the base 121 is hardly deformed because of its low height. At this time, the force acting on the first alignment film 113 is the bending M at the side surface 115 of the photo spacer 112 and the rubbing F at the top 114 of the photo spacer 112. The force acting on the second alignment film 122 is only the rubbing F at the top 123 of the pedestal 121.

  Here, as described above, the first alignment film 113 is not formed on the top portion 114 of the photo spacer 112 or is extremely thin, so that it is not peeled off due to the rubbing F. The first alignment film 112 on the side surface 115 of the photo spacer 112 is also thin, and the first alignment film 112 in the vicinity of the top portion 114 where the bending M works most strongly is particularly thin and flexible, so that the bending M breaks and peels off. It is thought that it does not.

  On the other hand, the second alignment film 123 is subjected to the action of rubbing F at the top 123 of the pedestal 121. At this time, the area of the top of the photo spacer 112 is smaller than the area of the top 123 of the pedestal 121. The corners 116 of 112 will rub against the second alignment film 123. In order to withstand this action, the strength of the second alignment film 123 at the top 123 of the pedestal 121 must be high. For this reason, it is considered that the second alignment film 123 is less likely to be peeled off, as opposed to the first alignment film 113.

  Next, a method of forming the first alignment film 113 in this embodiment will be described with reference to FIG.

The first alignment film 113 has the following steps:
(1) After performing the step of applying the alignment film solution 117 on the color filter substrate 110 on which the color filter layer 111 and the plurality of photo spacers 112 are formed, using an inkjet method,
(2) It is obtained by executing the step of drying the alignment film solution 117.
FIG. 3A shows a state immediately after step (1). Here, the broken line 118 indicates the average depth d1 of the alignment film solution 117. At this time, the alignment film solution 117 is applied in such an amount that the average depth d1 is equal to or less than the height T1 of the photo spacer 112. In this way, the top 114 of the photo spacer 112 is exposed from the surface of the alignment film solution 117 as shown in the figure. This is because when the ink jet method is applied, the droplets also land on the top 114 of the photospacer 112, but due to the surface tension of the alignment film solution 117, the alignment film solution 117 at the top 114 of the photospacer 112 This is because it is pulled in between 112. As a result, the alignment film solution 117 does not remain on the top 114 of the photospacer 112, or the amount of the alignment film solution 117 remains very small.

  FIG. 5B shows a state immediately after step (2). As illustrated, the first alignment film 113 has a thickness t1 on the surface of the color filter substrate 110, and the first alignment film 113 is not formed on the top 114 of the photo spacer 112. Is extremely thin. In addition, the first alignment film 113 formed on the top portion 114 of the photo spacer 112 is caused by chance due to the surface of the initial liquid film of the alignment film solution 117 being wavy, surface tension, or the like. Except for the coincidence, the thickness differs for each photo spacer 112. In other words, since the application by the inkjet method is performed, as a result, the thickness of the first alignment film 113 formed on the top 114 of the at least one photo spacer 112 is equal to that of the at least one other photo spacer 112. This is different from the thickness of the first alignment film 113 formed on the top portion 114.

Here, the thickness t1 is the ratio of the photo spacer 112 to the color filter substrate 110, the adhesion amount of the alignment film solution 117 to the photo spacer 112, the shrinkage amount of the first alignment film 113 after drying, and the alignment film solution 117. Although there are some fluctuations depending on the specific gravity of the constituent materials, the influence is small, and is almost equal to the average depth d1 multiplied by the solid content concentration W weight% of the alignment film solution 117. That is,
t1≈d1 × W × 1/100 (Expression 1)
It becomes. And
d1 ≦ T1 (Equation 2)
Because
t1 ≦ T1 × W × 1/100 (Equation 3)
It becomes.

  On the other hand, in order to perform application by an ink jet method, the viscosity of the solution to be used must be about 10 mPa · s or less in practice. However, in the alignment film solution, when the solid content concentration exceeds 3% by weight, it is difficult to set the viscosity to 10 mPa · s or less. Therefore, considering (Equation 3), it is preferable that the thickness t1 of the first alignment film 113 be 3% or less of the height T1 of the photo spacer 112. More preferably, it is 2% or less, and more preferably 1% or less.

  FIG. 4 is a diagram illustrating a method for forming the second alignment film 122.

For the formation of the second alignment film 122, a known coating method such as roll coating or curtain coating may be used. However, here, in order to simplify the process, an inkjet method is used as in the first alignment film 113. Application shall be used. That is, the next step (3) applying the alignment film solution 117 to the TFT substrate 120 on which the circuit element and the plurality of pedestals 121 are formed by application using an ink jet method (4) drying the alignment film solution 117 The step to be executed is executed.

  In this case, since the average depth d2 of the alignment film solution 117 is larger than the height T2 of the pedestal 121, as shown in FIG. It is buried in the solution 117.

  In this state, the alignment film solution 117 is dried in step (4) to obtain the second alignment film 122. FIG. In this case, the second alignment film 122 having a predetermined thickness is also formed on the top 123 of the pedestal 121. At this time, in order to sufficiently secure the strength of the second alignment film at the top 123 of the pedestal 121, the entire second alignment film 122 must be thickened. Therefore, as a result, the thickness t2 of the second alignment film 122 is thicker than the thickness t1 of the first alignment film 113.

  As described with reference to FIG. 2, the second alignment film 122 is peeled off by the rubbing F at the top 123 of the pedestal 121, so in principle, the first alignment film 113 at the top 114 of the photo spacer 112 is used. Similarly, it is considered that peeling of the second alignment film 122 can be prevented by forming the second alignment film 122 at the top 123 of the pedestal 121 little or making it very thin. However, as shown in FIG. 1, since the height T2 of the pedestal 121 is low, it is difficult to apply the alignment film solution 117 on the TFT substrate 120 so thin that the top 123 of the pedestal 121 is exposed. This is because in the ink jet method, since the minimum diameter of the ejected droplets is determined, it is not possible to apply the coating more thinly than a certain amount. In other application methods, it is generally difficult to apply thinly. Therefore, in the present embodiment, attention is paid to the fact that the bending M hardly acts on the second alignment film 122, and the strength is improved by increasing the thickness opposite to the first alignment film 113. .

  FIG. 5 is a schematic diagram showing a liquid crystal display device 200 according to the second embodiment of the present invention.

  The present embodiment is different from the first embodiment in that the photo spacer 221 is formed on the TFT substrate 220 and the pedestal 212 is formed on the color filter substrate 210. Specifically, a color filter layer 211 and a pedestal 212 are formed on one surface of the color filter substrate 210, and a second alignment film 213 is formed so as to cover the surface. A photo spacer 221 is formed on one surface of the TFT substrate 220, and a first alignment film 222 is formed so as to cover the surface. The photo spacer 221 and the pedestal 212 are disposed so as to face each other, and the liquid crystal 230 is sandwiched between the color filter substrate 210 and the TFT substrate 220. The height of the photo spacer 221 is higher than the height of the pedestal 212. That is, in this embodiment, the TFT substrate 220 corresponds to the first substrate, the photo spacer 221 corresponds to the first protrusion, the color filter substrate 210 corresponds to the second substrate, and the pedestal 212 corresponds to the second protrusion. Then, the first alignment film 222 is formed by application using an inkjet method. The dimensions of the first alignment film 222, the second alignment film 213, the photo spacer 221 and the pedestal 212 have the same relationship as in the first embodiment.

  Even if it does in this way, peeling of the alignment film can be prevented like the first embodiment.

The liquid crystal display device described in the first embodiment is
T1 = 3000nm
T2 = 800nm
t1 = 26nm
t2 = 75nm
Created as. The composition of the alignment film solution used is as follows.
Solid content: Polyimide ... 2.5% by weight
Solvent: n-methyl-2-pyrrolidone (NMP) 70.5% by weight
Ethylene glycol monobutyl ether (butyl cellosolve) 27% by weight
Viscosity: 9 ± 1 mPa · s
Moreover, the average depth of the alignment film solution at the time of application is
First alignment film: 1040 nm
Second alignment film: 3000 nm
It is.

  When the thus manufactured liquid crystal display device was inspected, the alignment film was not peeled off, and a high-quality liquid crystal display device was obtained.

  According to the invention described above, it is possible to provide a liquid crystal display device that can prevent peeling of the alignment film even when the alignment film is formed by coating using an inkjet method.

1 is a schematic diagram illustrating a liquid crystal display device according to a first embodiment. It is a schematic diagram of a mode when an external force is applied to the liquid crystal display device. It is a schematic diagram which shows the formation method of a 1st orientation film. It is a schematic diagram which shows the formation method of a 2nd alignment film. It is a schematic diagram which shows the liquid crystal display device which concerns on 2nd Embodiment. It is a schematic diagram which shows the process in which alignment film is formed on the color filter substrate of a liquid crystal display device using an inkjet system. It is a schematic diagram of the conventional liquid crystal display device.

Explanation of symbols

100, 200, 600 Liquid crystal display device, 110, 210, 610 Color filter substrate, 111, 211, 611 Color filter layer, 112, 221, 612 Photo spacer, 113, 222, 615 First alignment film, 114, 614 Top 115, 116 corners, 117,613 alignment film solution, 118 average depth of alignment film solution, 120, 220, 620 TFT substrate, 121, 212, 621 pedestal, 122, 213, 622 second alignment film, 123, 623 Top, 124 Average depth of alignment film solution, 130, 230, 630 Liquid crystal, 613a thick part, 613b thin part, 615a thick part, 615b thin part.

Claims (5)

A first substrate having a surface on which a plurality of first protrusions are formed and having a first alignment film covering the surface;
A second substrate having a surface on which a second protrusion lower than the plurality of first protrusions is formed, and a second alignment film covering the surface;
Have
The first substrate and the second substrate are arranged to face each other so that the top of the first projection and the top of the second projection are in contact with each other.
The first alignment film is thinner than the second alignment film,
A liquid crystal display device characterized by the above.   The liquid crystal display device according to claim 1, wherein a thickness of the first alignment film is 3% or less of a height of the first protrusion.   The liquid crystal display device according to claim 1, wherein an area of a top portion of the first protrusion is smaller than an area of a top portion of the second protrusion.   The thickness of the first alignment film formed on the top of at least one of the first protrusions is the same as the thickness of the first alignment film formed on the top of at least one other first protrusion. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display devices are different. The liquid crystal display device according to claim 4, wherein the first alignment film is formed by using an inkjet method.

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