Liquid crystal display apparatus and method for manufacturing the same

A first transparent substrate and a second transparent substrate having such a plurality of protrusions on the liquid crystal layer side as to contact with the first transparent substrate are so fixed by means of a sealant that they bend convexly to the liquid crystal layer. Thus, it is possible to suppress the mura defect of a panel, which might otherwise be caused by the heat radiation from a back light when a liquid crystal display apparatus is driven.

BACKGROUND OF THE INVENTION

The present invention relates to a structure of a liquid crystal panel to be mounted in a liquid crystal display apparatus, and a method for manufacturing the liquid crystal display apparatus.

A liquid crystal display apparatus is known as an In-plane-switching liquid crystal display apparatus in Japanese Patent Laid-open No. 2003-186023, for example. In this liquid crystal display apparatus, on the inner side face (i.e., the face on the side of a liquid crystal layer) of one of two opposite substrates with a liquid crystal layer between them, there are formed post spacers for retaining a cell gap from the other substrate.

SUMMARY OF THE INVENTION

In the liquid crystal display apparatus disclosed in the publication of the related art, however, when the liquid crystal layer between the two substrates expands with the heat coming from a back light, a variation in the thickness of the liquid crystal layer may occur to cause the mura defect.

Therefore, the invention helps provide a liquid crystal display apparatus which can suppress the mura defect.

According to one aspect of the invention, there is provided a liquid crystal display apparatus comprising: a first substrate including a first film formed; a second substrate confronting the first substrate and including a second film having first protrusions formed on a face facing the first substrate to contact with the first film; a frame-shaped sealant interposed between the first and second substrates and along the edges of the first and second substrates; and a liquid crystal layer enclosed by the frame-shaped sealant and formed in regions between the first and second films. The sealant fixes the first and second substrates such that the first substrate bulges toward the liquid crystal layer.

According to the invention, it is possible to suppress the mura defect effectively during the operation of the liquid crystal display apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the invention will be described with reference to the accompanying drawings.

First of all, a liquid crystal display apparatus according to the embodiment will be described in the following.

The image display apparatus according to the embodiment is provided with a liquid crystal panel LCD, which displays an image, as shown inFIG. 4.

As shown inFIG. 1andFIG. 2, this liquid crystal panel LCD includes: a pair of opposite transparent substrates (of glass, plastics or the like)10and20; a sealant30which fixes the frame-shaped edge region in the inner face (i.e., the face on the side of the substrate20)10A of the transparent substrate10on the inner face (i.e., the face on the side of the substrate10) of the other transparent substrate20; drivers (or terminals, to which signals from a driver chip are inputted)50formed in the edge regions along two sides of the inner face of one transparent substrate20; and a liquid crystal40which is sealed between the transparent substrates10and20.

In the sealant30, there are fitted fibers (e.g., glass fibers)31of a suitable diameter, which extend along the sealant30so as to control the spacing between the inner faces10A and20A of the transparent substrates10and20.

At least one of the paired transparent substrates10and20is fixed on the sealant30so that it stay a state in which it has been bended convexly to the liquid crystal40by the pressure applied at a substrate assembling step. Specifically, the sealant30existing on at least one of the four sides of the liquid crystal panel constrains the edge portions of the transparent substrates10and20so that the spacing between the inner sides10A and20A of the transparent substrates10and20may become gradually narrower from the edges of the transparent substrates10and20toward a interface30A between the sealant30and the liquid crystal layer40(i.e., so that the spacing may satisfy the following Relation (1)):
h3a<h3b  (1).

Here, h3bdesignates the spacing between the inner faces10A and20A at the edge position of the transparent substrates, and h3adesignates the spacing between the inner faces10A and20A of the transparent substrates at a position closer to the interface30A between the sealant30and the liquid crystal layer40than the edge position of the transparent substrates.

As shown inFIG. 2, one transparent substrate10of the two transparent substrates is provided on its inner face10A with a multi-layered film11including a color film, and the other transparent substrate20is provided on its inner face20A with a multi-layered film21containing the TFTs. Here, the structures of the multi-layered films11and21are omitted inFIG. 2.

The multi-layered film21of one transparent substrate20is provided with a plurality of protrusions21A which function as a spacer for restricting the deformations of the transparent substrates10and20toward the liquid crystal40, in image display regions A (i.e., the regions in which pixel regions54enclosed by drain lines51and gate lines52and passed by common electrode signal lines53and a color filter exist in a matrix shape so that the image is displayed by the transmission of light) and in an image non-display regions B (i.e., the regions which are located between the image display regions A and the sealant30so that the image is not displayed). Moreover, the multi-layered film11of the other transparent substrate10is so formed that a film thickness t1at positions facing the individual protrusions21A in the image display regions A is smaller than a film thickness t2at positions facing the individual protrusions21A in the image non-display regions B.

Here, the plural protrusions are formed on the multi-layered film21containing the TFTs and the thickness of the multi-layered film11including the color filter layer is made smaller in the image display regions A than in the image non-display regions B. However, it is not necessary to do so.

For example, to the contrary ofFIG. 2, the plural protrusions may be formed on the multi-layered film11including the color filter layer, and the thickness of the multi-layered film21containing the TFTs may be smaller in the image display regions A than in the image non-display regions B. Moreover, the protrusions in the image non-display regions B and the image display regions A may also be formed on the multi-layered film11.

The thicknesses of those multi-layered films11and21have the following Relations (2):
t1+T1<t2+T2<t3+d+T3  (2).

T1: the thickness of the multi-layered film21at the protrusion positions in the image display regions A;

T2: the thickness (=T1) of the multi-layered film21at the protrusion positions in the image non-display regions B;

T3: the thickness of the multi-layered film21in regions C forming the sealant30;

d: the diameter of the fibers31; and

t3: the thickness of the multi-layered film11in the regions C forming the sealant30.

As a result, the spacing between the inner faces10A and20A of the transparent substrates10and20is so gradually narrowed from the edges of the transparent substrates10and20toward the image display regions A as to satisfy the following Relations (3), and is substantially constant in the image display regions A:
h1<h2<h3  (3).

h1: the spacing in the image display regions A between the inner faces10A and20A of the transparent substrates10and20;

h2: the spacing in the image non-display regions B between the inner faces10A and20A of the transparent substrates10and20; and

h3: the spacing in the regions C forming the sealant30between the inner faces10A and20A of the transparent substrates10and20.

The structure thus made can suppress the variation in the thickness of the liquid crystal layer40for the following reasons so that it can prevent the mura defect, as might otherwise be caused by the heat coming from a back light.

Under pressure applied at the substrate assembling step, the individual transparent substrates10and20are deformed convexly toward each other using the fibers31of the sealant30in the regions C as a support point, as indicated by a broken curve inFIG. 3. However, this deformation is restricted at the positions of the protrusions in the image display regions A and in the image non-display regions B. As the sealant30becomes hardened, the edge portions of the two transparent substrates10and20are restrained while keeping their shapes under pressure by the sealant30. As a result, the two transparent substrates10and20put the forces in the directions to compress the protrusions21A to each other, after the pressure is released.

As indicated by a solid curve inFIG. 3, therefore, the variation in the positions of the inner faces of the transparent substrates within the image display regions A is suppressed, so that variation in the thickness of the liquid crystal layer40can be resultantly suppressed.

In the image non-display regions B in which the spacing between the inner faces10A and20A of the two transparent substrates10and20are larger than in the image display regions A, the multi-layered film11of the transparent substrate10is accordingly thicker. In the image non-display regions B, therefore, the multi-layered film11of the transparent substrate10will not be excessively away from the protrusions21A of the multi-layered film21of the transparent substrate20. As a result, the thickness fluctuation in the liquid crystal film20can be prevented, which is caused by the partial deformation of the transparent substrate, even if the image non-display regions B are touched by the user, for example.

In a case the percentage of width of the image non-display regions B to that of the image display regions A is equal or smaller than a predetermined value, it is not necessarily essential that the thickness of the multi-layered film11be made larger in the image non-display regions B than in the image display regions A.

According to the liquid crystal panel of this embodiment, therefore, the mura defect can be suppressed, as described above.

A method for manufacturing a liquid crystal panel having such structure above will be described.

FIG. 13is a flow chart showing a process for manufacturing a liquid crystal display apparatus having the liquid crystal panel ofFIG. 1andFIG. 2, from a sealant printing step to a sealing step.

Two transparent substrates (hereinafter, called to as “mother substrates”)100and200capable of taking the one-side substrates for the four liquid crystal panel are prepared, as shown inFIG. 5, and are subjected to a predetermined pretreatment such as a rinsing treatment to these mother substrates100and200. InFIG. 5: broken lines50designate cutting plane lines for defining the regions (hereinafter, called to as “panel regions”) to become one-side substrates of the individual liquid crystal panels; regions d other than the panel regions are the regions (hereinafter, called to as “cut regions”) to be cut off at a panel cutting step; regions a in the individual panel regions are the regions to become the image display regions A of the individual liquid crystal panels; regions b are the regions to become the image non-display regions B of the individual liquid crystal panels; and regions enclosing the regions b in the individual panel regions are the regions to become the sealant forming regions C of the individual liquid crystal panels.

Here, the dotted lines and the broken lines shown inFIG. 5are virtual lines which are not actually formed in the mother boards. Moreover, here is enumerated an example, in which the four transparent substrates for the liquid crystal panels are taken from the mother substrates100and200. The number of the substrates to be taken from the mother substrates100and200are determined according to the aspect ratios of the mother substrates100and200and the aspect ratios (or the screen sizes) of the liquid crystal panels.

On the one-side face (hereinafter, called to as “pattern forming face”) of one mother substrate200, there is formed a multi-layered film21′, as shown inFIG. 6. This multi-layered film21′ is composed of: (1) RGB color filter films22disposed for individual sub-pixels in the individual regions a; (2) grid-shaped black matrix films23formed in the individual regions b between the color filter films22; (3) an overcoat film24covering the pattern forming face side of the mother substrate200entirely as the upper layer film above the black matrix films23and the color filter films22; (4) post-shaped films25of an organic substance (or an inorganic substance) formed at positions confronting the black matrix films23across the overcoat film24and at positions in the cut regions d; and (5) an alignment layer26covering the overcoat film24in the regions a and b.

This multi-layered film21′ includes the plural post-shaped films25so that a surface of the multi-layered film21′ protrudes at the positions of the individual post-shaped films25toward the mother substrate200by a height T0of the individual post-shaped films25.

On the one-side face (hereinafter, called to as “pattern forming face”) of the other mother substrate100, there is formed a multi-layered film11′, as shown inFIG. 7. Thus multi-layered film11′ is composed of: (1) gate lines12; (2) drain lines (not shown); (3) an insulating film13covering as the upper layer above the gate lines12the pattern forming face side of the mother substrate100entirely; (4) an amorphous silicon film14of the TFTs formed at positions confronting the terminals12A of the gate lines12in the regions a across the insulating film13; (5) an amorphous silicon film14A formed at positions confronting the terminals12A of the gate lines12in the regions b across the insulating film13; (6) an organic film (or an inorganic film)15A interposed only between the amorphous silicon film14and the insulating film13in the individual regions b; (7) a protective film19covering as the upper layer above the amorphous silicon film14the pattern forming side of the mother substrate100entirely; (8) transparent electrodes18formed at positions confronting the amorphous silicon film14across the protective film19; (9) an alignment layer16covering as the upper layer above the transparent electrodes18the regions a and b; and (10) an organic film (or an inorganic film)15B formed in the cut regions d along the individual sides of the regions b so that the film thickness t4in the cut regions d is larger than that t2in the regions b.

This multi-layered film11′ contains the organic film (or the inorganic film)15A existing only in the regions b so that its film thickness is larger in the regions b than in the regions a. Moreover, the multi-layered film11′ contains the organic film (or the inorganic film)15B formed only in the cut regions d so that its thickness is far larger in the cut regions d than in the regions b.

Here, the organic film (or the inorganic film)15A may have a frame-shaped pattern (excepting the liquid crystal injection port) enclosing the regions a, as shown inFIG. 8, or may have a circular or rectangular pattern formed only at positions confronting the individual post-shaped films25of the other mother substrate20′. Likewise, the organic film (or the inorganic film)15B may have a frame-shaped pattern enclosing the regions b, as shown inFIG. 8, or may have a circular or rectangular pattern formed only at positions confronting the individual post-shaped films25of the other mother substrate20′.

Next, the sealant30of a thermoset or UV-set type containing the fibers31kneaded is applied (at S1) to the individual regions c (although the portion for the liquid crystal injection port is excluded) in the pattern forming face of either of those two mother substrates100and200. The fibers31to be used have the diameter d satisfying the following conditions:
(t2+T2)−(T3+t3)<d≦(T4+t4)−(T3+t3).

T2: the film thickness of the multi-layered film21′ at the positions of the post-shaped films25in the regions b;

T3: the film thickness of the multi-layered film21′ in the regions c;

T4: the film thickness of the multi-layered film21′ at the positions of the post-shaped films25in the cut regions d;

t2: the film thickness of the multi-layered film11′ at the positions of the post-shaped films25in the regions b;

t3: the film thickness of the multi-layered film11′ in the. regions c; and

t4: the film thickness of the multi-layered film11′ in the cut regions d.

In order to prepare the liquid crystal panel having a screen size of 28 inches, image non-display regions B of a width of 5 cm and sealant forming regions of 1 cm, for example, the post-shaped film in the regions d is placed at a position of about 4 cm from the boundary between the regions c and the regions d. Then, it is desired to fix the thickness of each component films forming the individual multi-layered films11′ and21′ such that: (t2+T1)=about 2.10 μm; (T2+t3)+d=about 12.30 μm; (T3+t4)=about 12.80 μm; and (h2−h1)=0.5 μm or less.

After this, the individual panel regions are positioned, as shown inFIG. 9, to superpose the pattern forming faces of the two mother substrates100and200. Moreover, the sealant30is set (at S2) by heating it or by irradiating it with an ultraviolet ray while applying a load to the two superposed mother substrates100and200in the direction to press the contact face between the multi-layered films11′ and21′ . As a result, the two mother substrates100and200are fixed, as indicated by a broken curve inFIG. 10, such that the individual image display regions A or the like bend convexly to the other substrate and such that cut regions D bend convexly outward.

When the load is then released, the sealant forming portions C of the two mother substrates100and200are constrained by the hardened sealant30while keeping their pressed shapes. As a result, the two mother substrates100and200are fixed to satisfy the following Relations (4), as indicated by a solid curve in FIG.10.
h1<h2<h3<h4  (4).

h1: the spacing (=t1+T1) of the pattern forming faces at the protrusion positions in the regions a;

h2: the spacing (=t2+T1) of the pattern forming faces at the protrusion positions in the regions b;

h3: the spacing (=t3+T2+d) of the pattern forming faces in the regions c; and

h4: the spacing (=t4+T3) of the pattern forming faces in the cut regions d.

After this, the mother substrates100and200are divided into individual liquid crystal panels by cutting them along the cutting plane lines50(at S3). Then, the inside (i.e., the space between the two transparent substrates, enclosed by the sealant30) of the individual liquid crystal panels is filled with the liquid crystal (at S4), and the liquid crystal injection port is sealed with a sealing material (at S5).

As a result, it is possible to manufacture the liquid crystal panel having the structure, as shown inFIG. 1andFIG. 2. Moreover, the liquid crystal panels are subjected to a predetermined treatment and are inserted into a casing, so that the liquid crystal display apparatus, as shown inFIG. 4, can be manufactured.

Here, the liquid crystal is injected into the individual liquid crystal panels after they are divided, but this sequence is not indispensable. For example, the two transparent substrates may be superposed after a necessary quantity of liquid crystal is applied to the pattern forming face of either transparent substrate.

Here, the multi-layered film containing the TFTs is made thicker in the image non-display regions B than in the image display regions A. However, the multi-layered film containing the color filter films may be made thicker in the image non-display regions B than in the image display regions A, as described hereinbefore. In this case, multi-layered films11″ and21″, as shown inFIG. 11, may be formed on the pattern forming faces of the two mother substrates100and200.

The multi-layered film11″ of one mother substrate100is composed of: (1) RGB color filter films112disposed for individual sub-pixels in the regions a; (2) grid-shaped black matrix films113formed between the regions b and the color filter films112; (3) a color filter film112A formed on the black matrix film112in the regions b; (4) an overcoat film114covering the one face of the mother substrate100entirely as the upper layer film above the black matrix films113and the color filter films112and112A; (5) an alignment layer116covering the overcoat film114in the regions a and b; and (6) an organic film (or an inorganic film)115along the individual sides of the regions b in the cut regions d.

The multi-layered film21″ of the other mother substrate200is composed of: (1) gate lines226; (2) drain lines (not shown); (3) an insulating film227covering the gate lines226; (4) an amorphous silicon film221of the TFTs formed at positions confronting the terminals226A of the gate lines226across the insulating film227; (5) a protective film223covering as the upper layer above the amorphous silicon film221the one side of the mother substrate200entirely; (6) transparent electrodes224formed at positions confronting the amorphous silicon film221across the protective film223; (7) post-shaped films225formed of an organic substance or an inorganic substance at positions over the transparent electrodes224and in the regions d; (8) an alignment layer226covering as the upper layer above the post-shaped films225the regions a and b entirely.

The mother substrates100and200thus having the multi-layered films11″ and21″ formed are assembled like the aforementioned case. Then, it is possible to manufacture the liquid crystal panel having the two transparent substrates which are made to bend convexly to the liquid crystals by the pressure applied at the substrate assembling step.

Here, the shapes of the multi-layered films over the pattern forming faces of the individual mother substrates100and200need not be limited to the aforementioned ones, if the total film thicknesses of the multi-layered films interposed between the pattern forming faces of the mother substrates100and200at the contact positions of the multi-layered films over the pattern forming faces of the mother substrates100and200satisfy “the relations of the total film thickness in the regions a≦the total film thickness in the regions b<the total film thickness in the seal regions c≦the total film thickness in the cut regions d”.

In the description thus far made, the spacing between the pattern forming faces of the mother substrates100and200is controlled by the thickness of the multi-layered films on the mother substrates100and200. However, this control may not be made just in the aforementioned manner, if the spacing between the pattern forming faces of the mother substrates100and200can be controlled.

For example, the spacing between the pattern forming faces of the mother substrates100and200may be made to satisfy the Relations (4), as shown inFIG. 12, by applying a sealant33kneaded with fibers32radially smaller than the fibers31in the regions c to the regions band by applying a sealant35kneaded with fibers34radially larger than the fibers31in the regions c to the regions d.

Even if the temperature of the liquid crystal panels themselves is raised by the heat radiation from the back light during the operation of the liquid crystal display apparatus, as has been described hereinbefore, it is possible to suppress the resultant mura defect effectively.