JP2004126197A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device that prevents the occurrence of display irregularity and bubbles unlike the conventional liquid crystal display device in which the device is formed as a solid body and the utilization is limited and thin glass substrates are newly used for array substrates and opposing substrates to realize a flexible liquid crystal display device resulting in the occurrence of display irregularity caused by fluctuation in gaps among substrates at a liquid crystal center portion due to opposing stress being applied to the substrates while the substrates are bent and the occurrence of bubbles as temperature varies. <P>SOLUTION: Spacers 15 arranged between the array substrate 20 and the opposing substrate 21 are distributed so that the distribution density or the contact area per unit area at the center portion are made larger compared with the peripheral portions in the bending direction. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device in which a liquid crystal member is sandwiched between a flexible array substrate and a counter substrate, and in particular, a spacer in which one end is fixed to one of the substrates is more centrally located than peripheral portions of the substrate. The present invention relates to a liquid crystal display device in which the spacing between both substrates is defined to be a predetermined value by arranging spacers so as to increase the distribution density or the contact area per unit area.
[0002]
[Prior art]
As a current color liquid crystal display device, an active matrix type color liquid crystal display device is predominant because there is no crosstalk between adjacent pixels and a good display image can be realized. As shown in FIG. 4, this active matrix type color liquid crystal display device has a thin film transistor using amorphous silicon as a semiconductor layer in a matrix on a substrate 41 made of a transparent glass material having a thickness of about 0.5 to 1 mm. (TFT) 42 is provided, and a plurality of coloring layers 43B, 43G, 43R forming three color filters 43 of blue, green, and red made of an acrylic material or the like are provided so as to cover at least a part of the TFT 42. . Through holes 44B, 44G, and 44R are formed in the coloring layers 43B, 43G, and 43R, respectively, and a plurality of transparent pixel electrodes 45 connected to the TFTs 42 are arranged on the color filter 43. And an array substrate 47 on which an alignment film 46 made of polyimide or the like is formed.
[0003]
A counter substrate 48 disposed to face the array substrate 47 has a substrate 49 similarly formed of a transparent glass material having a thickness of about 0.5 to 1 mm. A transparent opposing electrode 50 made of ITO or the like is provided on the opposing surface opposing the. On the counter electrode 50, an alignment film 51 made of polyimide or the like is provided.
[0004]
A silver paste (not shown) or the like is disposed around the screen as an electrode transfer material for applying a voltage from above the array substrate 47 to the opposing substrate 48, and the electrode transfer material causes a gap between the array substrate 47 and the opposing substrate 48. The connection is made electrically.
[0005]
As shown in FIG. 5, a space between the array substrate 47 and the opposing substrate 48 is defined by a plurality of spacers 52 interposed between the two substrates 47 and 48 at substantially equal intervals. At the same time, the peripheral portion is bonded via a sealing material 53 made of a heat or ultraviolet curable acrylic or epoxy adhesive, and a liquid crystal member 54 is sealed in the gap, In addition, a frame layer 55 is arranged on a surface of the substrate 41 or the like as necessary to form a liquid crystal panel 56.
[0006]
A polarizing plate 57 is attached to both outer surfaces of the liquid crystal panel 56 with an adhesive, and a backlight or a reflecting plate (not shown) is provided outside the polarizing plate 57 on the array substrate 47 side as necessary. ) Are arranged to constitute a color liquid crystal display device.
[0007]
In the color liquid crystal display device configured as described above, for example, the backlight serving as a light source is turned on, and the TFT 42 is driven to control the switching of the pixel electrode 45 so as to be supplied to the counter electrode 50 facing the voltage of the pixel electrode 45. A predetermined color image is displayed by controlling the liquid crystal member 54 on each pixel electrode 45 according to a potential difference from the applied voltage to act as an optical shutter. This color liquid crystal display device can display a color image with sufficient display quality such as luminance and contrast even in this configuration.
[0008]
However, this color liquid crystal display device has no flexibility since both substrates 41 and 49 are made of a glass material having a plate thickness of about 0.5 to 1 mm, and is exclusively used for color televisions. It is used as a solid-state display device such as a John receiver, a color terminal display, or a monitor screen of a mobile phone. In the solidified liquid crystal display device, an attempt to give flexibility to the liquid crystal display device itself has been promoted in order to specify an intended use.
[0009]
In order to realize flexibility in this liquid crystal display device, it is essential that both the substrates 41 and 49 have flexibility. However, recently, the glass substrate has a thickness of 0.1 mm or less. Ultra-thin substrates have been developed. By applying this substrate to the array substrate 47 and the opposing substrate 48 of the liquid crystal display device, it is possible to constitute a liquid crystal display device which is reduced in weight and has improved strength so that it is not broken even when bent. In the future, there is a possibility that the present invention can be applied to new fields such as an electronic book, an electronic organizer, and various forms of advertising media having a curved surface.
[0010]
[Problems to be solved by the invention]
However, it has been found that even if such a flexible glass substrate is simply employed as the array substrate 47 and the counter substrate 48 of the liquid crystal display device, it cannot be configured as a liquid crystal display device having good image quality. did.
[0011]
That is, as shown in FIG. 6, in a liquid crystal display device having flexibility, the array substrate 47 and the opposing substrate 48 are frequently bent and used inevitably. Therefore, the two substrates 47 and 48 receive stresses in opposite directions as indicated by arrows in the figure. Therefore, at least one end of one of the spacers 52 interposed between the two substrates 47 and 48 to keep the distance between the array substrate 47 and the opposing substrate 48 in order to prevent the spacer 52 from moving. It must be fixed to one side and fixed in position.
[0012]
In this manner, for example, when one end of the spacer 52 is fixed to the array substrate 47 and the other end is brought into contact with the surface of the counter substrate 48 as a free end, such stress is applied to the two substrates 47 and 48 in a curved direction. In the central portion, the distance between the substrates 47 and 48 is reduced, in other words, the direction of the normal to the substrates 47 and 48 is applied, and the bending direction of the counter substrate 48 with which the free end of the spacer 52 is in contact. And is deformed so as to be forcibly dragged on the surface of the counter substrate 48 in the bending direction.
[0013]
On the free end side of the spacer 52, when the degree of the curvature is weak, the spacer 52 is only deformed in accordance with the stress, but when the degree of the curvature further increases, the spacer 52 resists the stress. The surface of the alignment film 51 formed on the counter substrate 48 can be dragged without being completely removed. As a result, if the spacer 52 is insufficient in strength against stress, the spacer 52 is deformed and it becomes difficult to maintain the space between the substrates 47 and 48 at a predetermined value, and the space 52 becomes narrower. Due to the deformation, the thickness of the liquid crystal member 54 in the central portion of the liquid crystal panel 56 becomes thin, which causes display unevenness.
[0014]
In order to solve this problem, if the spacers 52 are densely arranged over the entire area of the liquid crystal panel 56 so as to oppose these bending stresses and maintain the interval between the substrates 47 and 48 at a predetermined value, the liquid crystal panel 56 will When the volume of the liquid crystal member 54 is reduced due to the influence of an external temperature change or the like, the substrates 47 and 48 cannot change following the change because the density of the spacer 52 is too high. For this reason, there is a problem that a gap is generated between the liquid crystal member 54 and the substrates 47 and 48, and bubbles (low-pressure bubbles) are generated in the liquid crystal member 54.
[0015]
The present invention has been made to address such a problem, and the distribution density of the spacers in the central portion or the contact area per unit area is set to be larger in the bending direction of the liquid crystal panel than in the peripheral portion. By doing so, the thickness of the liquid crystal member in the center portion is prevented from being reduced, thereby preventing the occurrence of display unevenness and preventing bubbles from being generated in the liquid crystal member, thereby providing a liquid crystal display having a good display quality. It is intended to provide a device.
[0016]
[Means for Solving the Problems]
The present invention relates to a flexible array substrate provided with pixel electrodes, a flexible opposing substrate disposed opposite to the array substrate and provided with opposing electrodes on an opposing surface, the opposing substrate and the array substrate In a liquid crystal display device including a spacer that defines a gap between the array substrate and a liquid crystal member sandwiched between the opposing array substrate and the opposing substrate, one end of the spacer is disposed on at least one of the array substrate and the opposing substrate. The substrates were fixed and arranged so that the distribution density of the spacers in the central portion was higher than the peripheral portion of the substrate.
[0017]
In addition, a flexible array substrate having pixel electrodes, a flexible opposing substrate disposed opposite to the array substrate and having opposing electrodes on an opposing surface, and a flexible substrate between the opposing substrate and the array substrate are provided. In a liquid crystal display device including a spacer that defines a gap and a liquid crystal member sandwiched between an opposing array substrate and an opposing substrate, one end of the spacer is fixed to at least one of the array substrate and the opposing substrate. In addition, the contact area per unit area between the spacer and the substrate in the central portion is larger than that in the peripheral portion of the substrate.
[0018]
With this configuration, even when the liquid crystal display device is curved and a stress in the opposite direction is applied between the array substrate and the counter substrate, the distribution density of the spacer in the central portion with respect to the peripheral portion of the substrate or By arranging spacers so that the contact area per unit area is large, it is possible to prevent the thickness of the liquid crystal member from being reduced due to the stress due to the curvature of the substrate and to prevent bubbles from being generated in the liquid crystal member. Thus, a liquid crystal display device having good display quality can be obtained.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0020]
As shown in FIGS. 1A and 1B, a color liquid crystal display device according to the present invention is made of an ultrathin plate-shaped transparent glass material having a plate thickness of 0.1 mm or less and having flexibility. The electrode wiring and the TFT 12 are provided on the main surface of the substrate by making use of fine techniques such as film formation and patterning. The TFT 12 and the electrode wiring are configured as follows, for example.
[0021]
That is, after depositing a molybdenum-tungsten (MoW) film on the main surface of the substrate 11 by using a sputtering method, patterning is performed, and a gate electrode constituting the TFT 12 and a scanning line for supplying a scanning signal are arranged. A gate insulating film made of silicon oxide or silicon nitride is provided on the substrate 11 so as to cover the gate electrodes and the scanning lines, and the surface of the gate insulating film on which the gate electrodes are arranged is formed by CVD. After depositing an amorphous silicon film, patterning is performed, and a semiconductor layer forming the TFT 12 is disposed. Further, molybdenum (Mo) / aluminum (Al) / molybdenum (Mo) is sequentially deposited and patterned on this semiconductor layer, so that a source electrode, a drain electrode and a video signal constituting the TFT 12 having a three-layer structure are formed. It is configured to form a signal line to be supplied.
[0022]
Around the TFT 12, RGB colored layers 13R, 13G, and 13B serving as color filters 13 that are color-coded into red (R), blue (B), and green (G) so as to cover at least a part thereof. A stripe is provided for each color. For example, when the first color is formed of red, the colored layers 13R, 13G, and 13B are formed by uniformly coating the entire surface of the substrate 11 with a UV-curable acrylic resin resist in which a red pigment is dispersed by using a spinner. Then, exposure is performed by irradiating an ultraviolet ray having a wavelength of 365 nm and an intensity of 100 mj / cm ² through a photomask pattern that irradiates a portion to be colored red with light. The photomask pattern includes a stripe-shaped pattern portion corresponding to the first color, a square-shaped pattern portion of a through-hole portion for connection between a pixel electrode and a TFT 12 to be described later, and a square-shaped pattern portion for a stacked spacer. Pattern portion.
[0023]
Thereafter, development is performed with a 1% aqueous solution of KOH for 20 seconds to form a 3.2 μm-thick red colored layer 13R and a through-hole portion 14R in the pattern portion. Subsequently, the green coloring layer 13G and the blue coloring layer 13B, and the respective through-hole portions 14G, 14B are formed in the same manner.
[0024]
Next, as shown in FIG. 1C, a plurality of columnar spacers 15 having one end fixed to the color filter 13 and the other end as a free end are provided at a predetermined portion located in the non-display area of the color filter 13. The substrate 11 is arranged such that the distribution density increases from the peripheral portion to the central portion of the substrate 11 with respect to the bending directions in the left, right, up and down directions. The position where the spacer 15 is located is provided between pixel patterns other than the display area of the pixel cell at least one per one or a plurality of pixel cells.
[0025]
Further, a frame layer 16 made of a black light-shielding film is provided by a photolithography method on an outer peripheral portion of a display region which is an outer peripheral portion of the color filter 13.
[0026]
Furthermore, a transparent pixel electrode 17 is formed on the color filter 13 by depositing ITO or the like to a thickness of 1500 ° by a sputtering method and patterning the film by a photolithography method. It is connected to the source / drain passage of the TFT 12 via each through-hole portion 14R, 14B, 14G. The TFTs 12 are arranged at intersections of signal lines and scanning lines arranged in a matrix. On the pixel electrodes 17, an alignment film 18 formed by applying polyimide or the like to a thickness of 600 mm is arranged. ing. In order to prevent the flexible substrate 11 from being damaged, a reinforcing material 19 formed by coating a transparent resin or the like is provided on the surface of the substrate 11 opposite to the surface on which the alignment film 18 is formed. The substrate 20 is constituted.
[0027]
On the other hand, a counter substrate 21 is arranged to face the array substrate 20. The counter substrate 21 is formed of an ultrathin transparent glass material also having a thickness of 0.1 mm or less, and has a transparent counter electrode 23 made of ITO or the like on a counter surface of a flexible substrate 22. An alignment film 24 made of polyimide or the like and having a thickness of 600 ° is sequentially laminated on the counter electrode 23, and is formed by coating a transparent resin for preventing damage on the surface opposite to the surface on which the alignment film 24 is formed. The opposing substrate 21 is constituted by providing the reinforcing material 25 described above.
[0028]
The opposing substrate 21 and the array substrate 20 are fixed by heating and bonding the periphery except for the injection port with a sealing material 26 made of, for example, a thermosetting epoxy adhesive while maintaining a predetermined gap by the spacer 15. In addition, an electrode transfer material for applying a voltage from the array substrate 20 to the counter substrate 21 is formed on an electrode transfer electrode (not shown) around the seal material 26. A liquid crystal member 27 made of, for example, a fluorine-based liquid crystal compound is injected into the gap, and then the injection port is sealed with an ultraviolet curable resin to form a liquid crystal panel 28.
[0029]
Further, a polarizing plate 29 is adhered and fixed to the outer surfaces of the reinforcing members 19 and 25 of the array substrate 20 and the counter substrate 21 of the liquid crystal panel 28, respectively. A color liquid crystal display device is configured by appropriately disposing a backlight, a reflection plate (not shown), and the like.
[0030]
When the color liquid crystal display device is configured as described above, when the color liquid crystal display device is curved left and right or up and down, the spacer 15 is distributed more in the central portion than in the left and right and up and down directions of the liquid crystal panel 28. Since the spacers 15 are arranged so as to have a high density, the distribution density of the spacers 15 is large in the central portion of the liquid crystal panel 28 where stress is applied in a direction in which the distance between the substrates 20 and 21 is reduced. It is strong enough to withstand enough stress to maintain the spacing between them.
[0031]
For this reason, even if the liquid crystal panel 28 is curved in the left-right or up-down direction, it is possible to avoid a situation in which the distance between the substrates 20 and 21 becomes narrower than a predetermined value due to the deformation of the spacers 15. It is possible to prevent the occurrence of display unevenness due to a change in the interval between 20, 20.
[0032]
Moreover, since the spacers 15 are sparse compared to the central portion so that the distribution density is small in the peripheral portion of the liquid crystal panel 28, the ambient temperature of the liquid crystal panel 28 is low and low. Even when the volume of the liquid crystal member 27 is reduced, the substrates 20 and 21 are deformed in a portion where the spacer 15 is sparse, following the reduction in the volume of the liquid crystal member 27, and are constantly in contact with the liquid crystal member 27. State can be maintained. Therefore, no gap is generated between the substrates 20 and 21 and the liquid crystal member 27, and generation of bubbles in the liquid crystal member 27 can be prevented.
[0033]
Therefore, even if the liquid crystal panel 28 is curved, it is possible to prevent display unevenness and bubbles from occurring, as well as display in a normal flat state, and to configure a liquid crystal display device having excellent display characteristics. .
[0034]
In the liquid crystal display device having the above-described configuration, the case where the liquid crystal display device is used in a curved manner in the left-right and up-down directions is described. In the case where the spacer 15 is used only in one direction in advance as shown in FIG. 2, the distribution of the spacers 15 is dense in the central portion and sparse in the peripheral portion along the azimuth to be curved as shown in FIG. It is also possible to set the distribution density of the spacers 15 in advance. In the case where the bending direction is bent only to one position, the stress accompanying the bending is applied to the entire direction orthogonal to the bending direction at all times. If the spacers 15 are arranged so as to have a high distribution density, it is possible to more reliably prevent display unevenness as compared with a case where the spacers 15 are densely and densely arranged in a peripheral portion and a central portion in directions orthogonal to each other. Further, the configuration of the spacer 15 is also simplified.
[0035]
Thus, setting and distributing the distribution density of the spacers 15 so as to be dense and dense between the peripheral portion and the central portion of the display panel 28 means that the free end of the spacer 15 per unit area and the counter substrate 21 side are different. It can also be expressed as a relationship that makes the contact area larger or smaller. In the case shown in FIGS. 1C and 2, the portions that come into contact with the opposing substrate 21 on the free end side of the spacer 15 are all configured to have the same contact area. The contact area between the spacer 15 and the counter substrate 21 per area is naturally larger on the side of the central portion where the spacers 15 are densely arranged.
[0036]
The magnitude of the contact area is not limited to the case shown in the figure, but can be realized in the following configuration.
[0037]
That is, the area of the free end side contact portion of the spacer 15 can be realized by changing the shape of the spacer 15. For example, the outer diameter of the spacer 15 is increased so as to increase the contact area of the spacer 15 in the central portion, and the outer diameter of the spacer 15 in the peripheral portion is configured to be smaller than this outer diameter. As a result, the total contact area of the spacers 15 per unit area can be formed larger in the central portion than in the peripheral portion.
When the contact area is large or small, the present invention can be applied to spacers 15 arranged at regular intervals as shown in FIG. In this case, for example, a square pillar-shaped spacer 15 is used for the spacer 15 located at the central portion, and a square pyramid-shaped spacer 15 is used for the spacer 15 located at the peripheral portion. Can be added. Therefore, even if the number of the spacers 15 per unit area is the same, the size of the contact area can be set.
[0038]
In such a configuration, the counter substrate 21 side and the spacer 15 abut on the entire surface of the substrate 21 at substantially equal intervals, so that not only can the strength balance as the liquid crystal panel 28 be improved, This eliminates the need to set a special arrangement configuration.
[0039]
Such a spacer 15 can be formed by lamination using the colored layers 13B, 13G, and 13R when the color filter 13 is formed.
[0040]
That is, when patterning the material of the color filter 13, the colored layers 13 R, 13 G, and 13 B constituting the color filter 13 are sequentially laminated to form the spacer 15, and the spacer 15 is formed by the pixel patterns of the first color and the second color. If the colored layers 13R, 13G, and 13B are formed simultaneously with the formation of the spacers 15 so as to be arranged between the pixel patterns of the third color and the first color, and between the pixel patterns of the second color and the third color, the manufacturing process of the spacer 15 can be performed. Can be simplified.
[0041]
When the frame layer 16 is formed on the array substrate 20, the spacer 15 can be formed together using the frame layer 16 material.
[0042]
That is, a black light-shielding film for forming the frame layer 16 is formed by photolithography on the outer peripheral portion of the display region, which is the outer peripheral portion of the array substrate 20, so as to hide the non-display region. Is used to form the spacers 15 at the positions on the array substrate 20 where the spacers 15 are to be formed. If the spacer 15 is formed using the same material as the material of the frame layer 16 constituting the frame layer 16 in this manner, the spacer 15 can be formed simultaneously using the same material when the frame layer 16 is formed. Thus, the number of steps can be similarly reduced.
[0043]
Further, the spacer 15 is not limited to such a columnar one, but, for example, as shown in FIG. 3, a spherical spacer 15 is scattered on an adhesive material 30 provided on the substrate 11 so as to be higher than a peripheral portion of the liquid crystal panel 28. It is also possible to configure so that the dispersion density in the central portion is increased. In this case, the adhesive 30 is applied in advance in a grid pattern on the substrate 11 and arranged so as to increase the dispersion density in the central portion, so that the dispersed spherical spacers 15 are dispersed in a predetermined manner. State. Since this spherical spacer 15 can be used as it is as a commercial product, it can be configured relatively inexpensively and easily. Further, since the contact surface on the substrate 22 side opposite to the side fixed by the adhesive 30 of the spacer 15 is spherical, even if the substrates 11 and 22 are curved, the surface on the substrate 22 side is smoothly slid. The stress applied to the spacer 15 can be easily released.
[0044]
Note that the present invention is not limited to those described in these embodiments, and various applications and modifications are possible. For example, the present invention is configured such that the color filter 13 is provided on the opposing substrate 21, 16 can be formed on the counter substrate 21 side. Further, the spacer 15 is not limited to one having one end fixed to the array substrate 20 side, but can be fixed to the counter substrate 21 side, and furthermore, can be arranged so as to project from both substrates 20 and 21 respectively. . Further, the distribution density and contact area of the spacers 15 can be changed continuously from the peripheral portion to the central portion, or can be changed stepwise by dividing into predetermined ranges, and the shape is not limited to a square pillar shape. However, it is needless to say that a shape such as a columnar shape and a triangular prism shape can be adopted, and the present invention can be applied not only to a color liquid crystal display device but also to a monochrome liquid crystal display device.
[0045]
【The invention's effect】
As described above, according to the present invention, even when the liquid crystal display device is curved and stress is applied to the liquid crystal panel, the distribution density of the spacer in the center portion of the panel where the stress is applied most is increased by the spacer in the peripheral portion. By increasing the contact area per unit area, it is possible to reduce the stress applied to the central portion, and therefore, the liquid crystal panel at the central portion of the liquid crystal panel is formed. Since the interval can be maintained at a predetermined value, it is possible to prevent the occurrence of display non-uniformity, and in the peripheral portion where the spacer is sparse relative to the central portion following the volume change of the liquid crystal member due to the temperature change. By displacing, the generation of bubbles can be prevented, and a liquid crystal display device with good display quality can be obtained.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a liquid crystal display device according to the present invention.
FIG. 2 is an explanatory diagram showing a distribution state of spacers that similarly constitute the liquid crystal display device.
FIG. 3 is an explanatory view showing another configuration example of the spacer.
FIG. 4 is a cross-sectional view showing a conventional liquid crystal display device.
FIG. 5 is an explanatory diagram showing a distribution state of spacers that similarly constitute the liquid crystal display device.
FIG. 6 is an explanatory diagram showing stress when the liquid crystal display device is curved.
[Explanation of symbols]
15: Spacer 17: Pixel electrode 20: Array substrate 21: Counter substrate 23: Counter electrode 27: Liquid crystal member

Claims (4)

A flexible array substrate with pixel electrodes,
A flexible counter substrate that is disposed to face the array substrate and includes a counter electrode on a counter surface;
A spacer defining a gap between the counter substrate and the array substrate;
In a liquid crystal display device comprising the opposed array substrate and a liquid crystal member sandwiched between the opposed substrates,
One end of the spacer is fixed to at least one of the array substrate and the counter substrate, and the spacers are arranged so that the density of the spacers in the central portion is higher than the peripheral portion of the substrate. Liquid crystal display. 2. The liquid crystal display device according to claim 1, wherein the spacers are arranged so that the distribution density of the spacers in the central portion of the array substrate and the counter substrate is greater than that in the peripheral portion of the substrate. A flexible array substrate with pixel electrodes,
A flexible counter substrate that is disposed to face the array substrate and includes a counter electrode on a counter surface;
A spacer defining a gap between the counter substrate and the array substrate;
In a liquid crystal display device comprising the opposed array substrate and a liquid crystal member sandwiched between the opposed substrates,
One end of the spacer is fixed to at least one of the array substrate and the counter substrate, and a contact area per unit area between the spacer and the substrate in a central portion is larger than a peripheral portion of the substrate. A liquid crystal display device comprising: 4. The device according to claim 3, wherein a contact area per unit area between the spacer and the substrate in a central portion is larger than a peripheral portion of the substrate in a bending direction of the array substrate and the counter substrate. Liquid crystal display device.

Images