JP6972538B2 - Liquid crystal display device - Google Patents

Description

The present invention relates to a liquid crystal display device.

The liquid crystal display panel includes, for example, a TFT substrate having a TFT (Thin Film Transistor), a CF substrate having a color filter, and a liquid crystal layer filled between the TFT substrate and the CF substrate. The thickness of the liquid crystal layer is adjusted by a photo spacer provided on the CF substrate. By increasing the density of the photo spacers, the strength of the liquid crystal display panel can be increased.

By the way, in a low temperature environment, the various members constituting the liquid crystal display panel shrink in volume, but the shrinkage rate of the liquid crystal is particularly large as compared with the shrinkage rate of the other members. Therefore, the shrinkage of the support portion cannot follow the shrinkage of the liquid crystal layer and becomes bubbles (low temperature bubbles). Further, when a slight impact is applied to the liquid crystal display panel at low temperature, bubbles are generated in the liquid crystal layer. This phenomenon is called low temperature shock bubble.

Further, as a problem different from the bubbles, in general, when a load of a predetermined strength or more is applied to the surface of the liquid crystal display panel, display unevenness occurs on the display portion thereof. In order to suppress display unevenness, it is necessary to increase the strength of the liquid crystal display panel.

Japanese Unexamined Patent Publication No. 2013-238729 Japanese Unexamined Patent Publication No. 2013-257393

The present invention provides a liquid crystal display device capable of improving the strength against an external force and suppressing the generation of bubbles in the liquid crystal layer.

The liquid crystal display device according to one aspect of the present invention includes a first and second substrates, a liquid crystal layer filled between the first and second substrates, and a plurality of switching elements provided on the first substrate. An insulating film provided on the plurality of switching elements, a plurality of first spacers provided on the insulating film for adjusting the thickness of the liquid crystal layer, and a color filter provided on the second substrate. It includes a common electrode provided on the color filter and a plurality of second spacers provided on the common electrode and lower than the first spacer.

The liquid crystal display device according to one aspect of the present invention includes a first and second substrates, a liquid crystal layer filled between the first and second substrates, and a plurality of switching elements provided on the first substrate. An insulating film provided on the plurality of switching elements, a plurality of first spacers provided on the insulating film to adjust the thickness of the liquid crystal layer, and the first spacer provided on the insulating film. It includes a plurality of lower second spacers, a color filter provided on the second substrate, and a common electrode provided on the color filter.

According to the present invention, it is possible to provide a liquid crystal display device capable of improving the strength against an external force and suppressing the generation of bubbles in the liquid crystal layer.

The plan view of the TFT substrate side of the liquid crystal display device which concerns on 1st Embodiment. The plan view of the CF substrate side of the liquid crystal display device which concerns on 1st Embodiment. FIG. 2 is a cross-sectional view of the liquid crystal display device along the AA'line of FIGS. 1 and 2. FIG. 2 is a cross-sectional view of the liquid crystal display device along the line BB'of FIGS. 1 and 2. FIG. 2 is a cross-sectional view of the liquid crystal display device along the CC'line of FIGS. 1 and 2. The figure explaining the density of a main spacer and a sub spacer. The figure explaining the height and diameter of a main spacer and a sub spacer. Sectional drawing of the main spacer which concerns on comparative example. The plan view of the TFT substrate side of the liquid crystal display device which concerns on 2nd Embodiment. FIG. 9 is a cross-sectional view of the liquid crystal display device along the BB'line of FIG.

Hereinafter, embodiments will be described with reference to the drawings. However, the drawings are schematic or conceptual, and the dimensions and ratios of each drawing are not always the same as the actual ones. Further, even when the same part is represented between the drawings, the relationship and ratio of the dimensions of each other may be represented differently. In particular, some embodiments shown below exemplify devices and methods for embodying the technical idea of the present invention, and depending on the shape, structure, arrangement, etc. of the components, the technical idea of the present invention. Is not specified. In the following description, elements having the same function and configuration are designated by the same reference numerals, and duplicate explanations will be given only when necessary.

[1] First Embodiment [1-1] Overall Configuration of Liquid Crystal Display Device FIG. 1 is a plan view of the liquid crystal display device 10 according to the first embodiment on the TFT substrate side. FIG. 2 is a plan view of the liquid crystal display device 10 on the CF substrate side. FIG. 3 is a cross-sectional view of the liquid crystal display device 10 along the AA'line of FIGS. 1 and 2. FIG. 4 is a cross-sectional view of the liquid crystal display device 10 along the line BB'of FIGS. 1 and 2. FIG. 5 is a cross-sectional view of the liquid crystal display device 10 along the CC'line of FIGS. 1 and 2. Note that FIG. 2 is a plan view of the CF substrate when viewed from the liquid crystal layer side in FIG.

The liquid crystal display device 10 includes a TFT substrate 11 on which a switching element (TFT) and a pixel electrode are formed, and a color filter substrate (CF substrate) 12 on which a color filter, a common electrode and the like are formed and arranged opposite to the TFT substrate 11. And prepare. Each of the TFT substrate 11 and the CF substrate 12 is composed of a transparent substrate (for example, a glass substrate). The TFT substrate 11 is arranged to face the backlight (not shown), and the illumination light from the backlight is incident on the liquid crystal display device 10 from the TFT substrate 11 side.

The liquid crystal layer 13 is filled between the TFT substrate 11 and the CF substrate 12. Specifically, the liquid crystal layer 13 is enclosed in a display area surrounded by the TFT substrate 11 and the CF substrate 12 and a sealing material (not shown). The sealing material is made of, for example, an ultraviolet curable resin, a thermosetting resin, an ultraviolet / heat combined type curable resin, etc., is applied to the TFT substrate 11 or the CF substrate 12 in the manufacturing process, and then cured by ultraviolet irradiation, heating, or the like. Be made to.

The liquid crystal material constituting the liquid crystal layer 13 changes its optical characteristics by manipulating the orientation of the liquid crystal molecules according to the electric field applied between the TFT substrate 11 and the CF substrate 12. As the liquid crystal mode, various liquid crystal modes such as a VA (Vertical Alignment) mode, a TN (Twisted Nematic) mode, and a homogeneous mode can be used.

A plurality of switching elements (active elements) 20 are provided on the liquid crystal layer 13 side of the TFT substrate 11. As the switching element 20, for example, a TFT (Thin Film Transistor) is used, and an n-channel TFT is used. As will be described later, the TFT 20 has a gate electrode electrically connected to the scanning line, a gate insulating film provided on the gate electrode, a semiconductor layer provided on the gate insulating film, and each other on the semiconductor layer. It includes a source electrode and a drain electrode provided apart from each other. The source electrode is electrically connected to the signal line.

A plurality of gate electrodes 21 each extending in the X direction are provided on the TFT substrate 11. A gate insulating film 22 is provided on the plurality of gate electrodes 21. A plurality of pixels for one row arranged in the X direction share one gate electrode 21. The gate insulating film 22 is made of a transparent insulating material, and for example, silicon nitride (SiN) is used.

A plurality of semiconductor layers 23 corresponding to the plurality of TFTs 20 are provided on the gate insulating film 22. As the semiconductor layer 23, for example, an amorphous silicon layer is used.

A source electrode 24 and a drain electrode 25 separated from each other are provided on one semiconductor layer 23 and the gate insulating film 22. Specifically, the source electrode 24 is formed so as to overlap a part of the semiconductor layer 23 and extend in the X direction. The drain electrode 25 is formed so as to overlap a part of the semiconductor layer 23 and extend in the direction opposite to the source electrode 24.

The source electrode 24 is electrically connected to the signal line 26 extending in the Y direction. A plurality of pixels for one row arranged in the Y direction are commonly connected to one signal line 26. The gate electrode 21, the source electrode 24, the drain electrode 25, and the signal line 26 may be, for example, any one of aluminum (Al), molybdenum (Mo), chromium (Cr), tungsten (W), or one or more of them. An alloy containing molybdenum or the like is used.

An insulating film 27 is provided on the source electrode 24 and the drain electrode 25. The insulating film 27 is made of a transparent insulating material, and for example, silicon nitride (SiN) is used.

A plurality of pixel electrodes 28 corresponding to the plurality of pixels 34 are provided on the insulating film 27. A contact plug 29 electrically connected to the pixel electrode 28 is provided in the insulating film 27 and on the drain electrode 25. For example, as a method of forming the contact plug 29, a contact hole that partially exposes the drain electrode 25 is formed in the insulating film 27, and the pixel electrode 28 is formed so as to fill the contact hole, whereby the pixel is formed. The contact plug 29 is formed at the same time as the forming step of the electrode 28. The pixel electrode 28 and the contact plug 29 are composed of transparent electrodes, and for example, ITO (indium tin oxide) is used. An alignment film (not shown) for controlling the orientation of the liquid crystal layer 13 is provided on the surface in contact with the liquid crystal layer 13.

Next, the configuration on the CF substrate 12 side will be described. A black matrix (also referred to as a black mask or a light-shielding film) 31 for shading is provided on the liquid crystal layer 13 side of the CF substrate 12. The black matrix 31 is arranged at the boundary of the pixels 34 and is formed in a mesh pattern. The black matrix 31 has a function of blocking light from the TFT 20 and a function of improving contrast by shielding unnecessary light between color filters having different colors.

A plurality of color filters 32 are provided on the CF substrate 12 and the black matrix 31. The plurality of color filters (color members) 32 include a plurality of red filters 32-R, a plurality of green filters 32-G, and a plurality of blue filters 32-B. A general color filter is composed of the three primary colors of light, red (R), green (G), and blue (B). An adjacent set of three colors of R, G, and B is a display unit (pixel), and the monochromatic part of any one of R, G, and B in one pixel is the minimum called a sub-pixel (sub-pixel). It is a drive unit. The TFT 20 and the pixel electrode 28 are provided for each subpixel. In the description of the present specification, a sub-pixel is referred to as a pixel unless it is particularly necessary to distinguish between a pixel and a sub-pixel.

In FIG. 2, a stripe arrangement is shown as an arrangement method (or a pixel arrangement method) of color filters. The stripe array is an array in which pixels included in the same column (one row along the Y direction) have the same color. However, the present invention is not limited to this, and other arrangement methods such as a mosaic arrangement and a delta arrangement may be used.

A common electrode 33 is provided on the color filter 32 and the black matrix 31. The common electrode 33 is formed in a planar shape over the entire display area of the liquid crystal display device 10. The common electrode 33 is composed of a transparent electrode, and for example, ITO (indium tin oxide) is used.

Although not shown, the liquid crystal display device 10 sandwiches the TFT substrate 11 and the CF substrate 12 from both sides, so that the TFT substrate 11 and the CF substrate 12 are sandwiched between a pair of polarizing plates (linear polarizing elements) and a pair of retardation plates (1/4 wave plate). To prepare for.

[1-2] Spacer Configuration Next, the spacer configuration will be described. The liquid crystal display device 10 includes a plurality of main spacers 35 and a plurality of sub spacers 36. The heights of the main spacer 35 and the sub spacer 36 are different, and the height of the sub spacer 36 is lower than the height of the main spacer 35. The main spacer 35 and the sub spacer 36 are made of a transparent material, for example, an acrylic photosensitive resin.

The spacers (main spacer 35 and sub spacer 36) are formed at predetermined positions in the panel by a photolithography step. Specifically, a spacer material is applied onto the base layer by spin coating or the like, prebaked and exposed, then developed with an alkaline solution and post-baked. As the spacer, for example, a negative photosensitive material in which the material is cured by exposure is used. Further, as the spacer, it is desirable to use a material having excellent resolution and developability at the time of patterning, high mechanical strength, high transparency, and no contamination with the liquid crystal material.

The main spacer 35 and the sub spacer 36 have a cylindrical shape. The main spacer 35 and the sub spacer 36 may be elliptical columns or square columns.

FIG. 6 is a diagram illustrating the densities of the main spacer 35 and the sub spacer 36. One square in FIG. 6 represents the pixel 34. For example, the number of main spacers 35 is less than the number of sub spacers 36.

The main spacer 35 has a function of holding the thickness of the liquid crystal layer 13 (corresponding to the cell gap between the two substrates) at a predetermined value. Further, the elastic deformation of the main spacer 35 with respect to pressure can suppress the generation of bubbles (or low-temperature impact bubbles) in the liquid crystal layer 13.

The sub-spacer 36 has a function of holding a minimum cell gap when an excessive pressure (load) is applied to the liquid crystal display device 10. By providing the sub-spacer 36, the strength of the liquid crystal display device 10 can be compensated, and the liquid crystal display device 10 can be prevented from being damaged due to, for example, external pressure.

The height h of the main spacer 35, that is, the thickness of the liquid crystal layer 13 is determined as follows. That is, in the 90 degree TN mode, “h = (3 ^1/2/2 ) × (λ / Δn)”. In the VA mode and the IPS (In-Plane Switching) mode, “h = (1/2) × (λ / Δn)”. Δn is the refractive index anisotropy (birefringence) of the liquid crystal, which is the difference between the refractive index of abnormal light and the refractive index of normal light. λ is the wavelength of light, and generally, 550 nm having a large visual sensitivity is selected.

The main spacer 35 is arranged at the corner of the pixel 34. That is, the main spacer 35 is arranged at the corners of the four adjacent pixels 34 and is surrounded by the four pixels 34. The arrangement of the sub spacer 36 is also the same as that of the main spacer 35. The main spacer 35 and the sub spacer 36 are arranged so as to overlap the black matrix 31 in a plan view.

Here, as shown in FIG. 3, for example, the color filter 32 is processed by (1) processing the red filter 32-R, (2) processing the green filter 32-G, and (3) processing the blue filter 32-B. It is formed in the order. Therefore, the green filter 32-G overlaps with one end of the red filter 32-R, and the blue filter 32-B overlaps with the other end of the red filter 32-R. Further, the blue filter 32-B overlaps with one end of the green filter 32-G. The overlapping portion of the color filter has a convex shape.

The main spacer 35 is provided on the insulating film 27 on the TFT substrate 11 side. As shown in FIG. 1, the pixel electrode 28 has a recessed corner. The four adjacent pixel electrodes 28 form a circle with their recesses (recessed portions). The main spacer 35 is arranged in this circle. Since the insulating film 27 has high flatness, the high main spacer 35 has improved stability and can prevent the main spacer 35 from tilting or falling over.

On the other hand, the low-height sub-spacer 36 is provided on the common electrode 33 on the CF substrate 12 side. That is, the sub spacer 36 is arranged at the overlapping portion of the color filter. Since the height of the sub-spacer 36 is low, it is possible to prevent the sub-spacer 36 from tilting or falling down even when the stability of the underlying layer is low.

Next, the conditions of the main spacer 35 and the sub spacer 36 will be described. Assuming that the force F, the cross-sectional area S of the spacer, the diameter d of the spacer, the Young's modulus E, the height h of the spacer, and the amount of change Δh in the height direction of the spacer, the following equation (1) holds.

F / S = EΔh / h
Δh = Fh / ES = Fh / Eπd ²
Δh ∝ h / d ² ... (1)

FIG. 7 is a diagram illustrating the height and diameter of the main spacer 35 and the sub spacer 36. The height of the main spacer 35 and _{h m,} the diameter is _{d m,} the height of the sub-spacers 36 _{h s,} a diameter and _{d s.} The amount of change in the height direction when the same force is applied to the main spacer 35 and the sub spacer 36 is defined as Δhm and Δhs, respectively. From the above equation (1), the following equations (2) and (3) are established.

△ h _m ∝ h _m / d _m ² ... (2)
△ h _s ∝ h _s / d _s ² ... (3)

Here, in order to reduce the low temperature impact bubbles, the flexibility of the main spacer 35 is made larger than the flexibility of the sub spacer 36. That is, the following equation (4) is derived in order to satisfy the condition of _{“Δh m} > Δh <sub>s”.

h m / h s> (d</sub> m / d s) 2 ··· (4)

As an _{example, h m = 3.5μm, h s} = 3.2μm, d m = 12μm, a d s = 11.5 .mu.m. As another _{example, h m = 3.5μm, h s} = 3.4μm, d m = 12μm, a d s = 12 [mu] m.

The above formula is based on the premise that each of the main spacer 35 and the sub spacer 36 is a cylinder. Generalizing, _"d ^{m 2"} can be rephrased as the cross-sectional area of the main spacer 35, _"d ^{s _2"} may be rephrased as the cross-sectional area of the sub-spacer 36. In this case, the cross-sectional area of the main spacer 35 is set smaller than the cross-sectional area of the sub spacer 36. Further, the ratio of the cross-sectional area of the main spacer 35 to the cross-sectional area of the sub-spacer 36 is smaller than the ratio of the height of the main spacer 35 to the height of the sub-spacer 36. The cross-sectional area is the area of the surface obtained by cutting the spacer horizontally (parallel to the substrate) at the same height. The cross-sectional area can also be rephrased as the area when the spacer is viewed in a plane.

Further, when the density of the main spacer 35 and the density of the sub spacer 36 are different, the cross-sectional area of the main spacer 35 can be rephrased as the total cross-sectional area of all the main spacers 35, and the cross-sectional areas of the sub spacers 36 are all. It can be rephrased as the total cross-sectional area of the sub spacer 36 of. That is, the total cross-sectional area of all the main spacers 35 is smaller than the total cross-sectional area of all the sub-spacers 36. Also, the ratio of the total cross-sectional area of all the main spacers 35 to the total cross-sectional area of all the sub-spacers 36 is smaller than the ratio of the height of one main spacer 35 to the height of one sub-spacer 36.

[1-3] Comparative Example Next, a comparative example will be described. FIG. 8 is a cross-sectional view of the main spacer 35 according to the comparative example. It is assumed that the main spacer 35 is formed on the CF substrate 12 side.

It is assumed that the red filter 32-R and the green filter 32-G in FIG. 8A are in the reference processing state. In FIG. 8B, the end portion of the green filter 32-G has a convex shape, and in FIG. 8C, the gap between the red filter 32-R and the green filter 32-G is large.

The height _{h a} of the main spacer 35 of FIG. 8 (a), the height _{h b} of the main spacer 35 of FIG. 8 (b), when the height _{h c} of the main spacer 35 in FIG. 8 (c), the height h _b is higher than _{h a,} the height _{h c} is lower than _{h a.}

Therefore, in the comparative example, since the heights of the plurality of main spacers 35 are not uniform, it is difficult to set the cell gap to a predetermined value.

On the other hand, in the present embodiment, the main spacer 35 is formed on the more stable insulating film 27. Therefore, the cell gap can be set to a predetermined value.

[1-4] Effect As described in detail above, in the first embodiment, the liquid crystal display device 10 has a plurality of main spacers 35 for adjusting the thickness of the liquid crystal layer 13, and a plurality of main spacers 35 having a height lower than that of the main spacer 35. A sub spacer 36 is provided. The main spacer 35 is provided on the insulating film 27 of the TFT substrate 11, and the sub spacer 36 is provided on the common electrode 33 of the CF substrate 12. Further, the total cross-sectional area of the plurality of main spacers 35 is set smaller than the total cross-sectional area of the plurality of sub spacers 36. Further, the ratio of the total cross-sectional area of the plurality of main spacers 35 to the total cross-sectional area of the plurality of sub-spacers 36 is smaller than the ratio of the height of one of the plurality of main spacers 35 to the height of one of the plurality of sub-spacers 36. Set.

Therefore, according to the first embodiment, the strength of the liquid crystal display device 10 can be improved while ensuring the flexibility of the liquid crystal display device 10. As a result, it is possible to suppress the generation of bubbles (or low-temperature impact bubbles) in the liquid crystal layer 13.

Further, since the main spacer 35 can be formed on the insulating film 27 having higher flatness, the stability of the main spacer 35 is improved. Thereby, the thickness of the liquid crystal layer 13 can be optimally set. Further, it is possible to prevent the main spacer 35 from tilting or falling.

Further, the main spacer 35 and the sub spacer 36 can be individually formed. Thereby, the heights of the main spacer 35 and the sub spacer 36 can be optimally adjusted.

In order to form the main spacer and the sub spacer having different heights on the same substrate, for example, a halftone mask in which the amount of light at the time of exposure differs depending on the region is used. However, in this embodiment, since the main spacer and the sub spacer are formed on separate substrates, it is not necessary to use a halftone mask. As a result, the process and cost of designing the halftone mask can be omitted.

[2] Second Embodiment In the second embodiment, both the main spacer 35 and the sub spacer 36 are arranged on the TFT substrate 11 side in order to improve the stability of both the main spacer 35 and the sub spacer 36. ing.

FIG. 9 is a plan view of the liquid crystal display device 10 according to the second embodiment on the TFT substrate side. FIG. 10 is a cross-sectional view of the liquid crystal display device 10 along the line BB'of FIG. The cross-sectional view taken along the AA'line of FIG. 9 is the same as that of FIG.

The sub spacer 36 is provided on the insulating film 27 on the TFT substrate 11 side. Further, the sub spacer 36 is arranged in the recessed region of the pixel electrode 28. The conditions of the height and the cross-sectional area of the sub spacer 36 are the same as those of the first embodiment.

According to the second embodiment, the stability of both the main spacer 35 and the sub spacer 36 can be improved. As a result, it is possible to prevent the sub spacer 36 from tilting or falling.

The present invention is not limited to the above embodiment, and the constituent elements can be modified and embodied within a range that does not deviate from the gist thereof. Further, the above-described embodiments include inventions at various stages, and by an appropriate combination of a plurality of components disclosed in one embodiment or by an appropriate combination of components disclosed in different embodiments. Various inventions can be constructed. For example, even if some components are deleted from all the components disclosed in the embodiment, if the problem to be solved by the invention can be solved and the effect of the invention is obtained, these components are deleted. The embodiment described above can be extracted as an invention.

10 ... liquid crystal display device, 11 ... TFT substrate, 12 ... CF substrate, 13 ... liquid crystal layer, 20 ... TFT, 21 ... gate electrode, 22 ... gate insulating film, 23 ... semiconductor layer, 24 ... source electrode, 25 ... drain electrode , 26 ... signal line, 27 ... insulating film, 28 ... pixel electrode, 29 ... contact plug, 31 ... black matrix, 32 ... color filter, 33 ... common electrode, 34 ... pixel, 35 ... main spacer, 36 ... sub spacer.

Claims (6)

1st and 2nd boards,
The liquid crystal layer filled between the first and second substrates,
A plurality of switching elements provided on the first substrate and
The insulating film provided on the plurality of switching elements and
Pixel electrodes provided on the insulating film and
A plurality of first spacers provided on the insulating film and adjusting the thickness of the liquid crystal layer, and
The color filter provided on the second substrate and
With the common electrode provided on the color filter,
A plurality of second spacers provided on the common electrode and lower than the first spacer are provided.
Each of the plurality of first spacers and the plurality of second spacers has a circular or oval shape.
Each of the plurality of first spacers and the plurality of second spacers is arranged at a corner of a rectangular pixel.
A liquid crystal display device in which the corners of the pixel electrodes are recessed so as not to overlap with the first spacer. 1st and 2nd boards,
The liquid crystal layer filled between the first and second substrates,
A plurality of switching elements provided on the first substrate and
The insulating film provided on the plurality of switching elements and
Pixel electrodes provided on the insulating film and
A plurality of first spacers provided on the insulating film and adjusting the thickness of the liquid crystal layer, and
A plurality of second spacers provided on the insulating film and lower than the first spacer,
The color filter provided on the second substrate and
It is equipped with a common electrode provided on the color filter.
Each of the plurality of first spacers and the plurality of second spacers has a circular or oval shape.
Each of the plurality of first spacers and the plurality of second spacers is arranged at a corner of a rectangular pixel.
The corners of the pixel electrodes are recessed so as not to overlap the first spacer and the second spacer .
A liquid crystal display device in which two spacers of the plurality of first spacers and the plurality of second spacers adjacent to each other in the direction in which the gate electrode extends are arranged with a plurality of pixels separated from each other. The liquid crystal display device according to claim 1 or 2, wherein the cross-sectional area of the first spacer is smaller than the cross-sectional area of the second spacer. The liquid crystal display device according to claim 1 or 2, wherein the ratio of the cross-sectional area of the first spacer to the cross-sectional area of the second spacer is smaller than the ratio of the height of the first spacer to the height of the second spacer. The liquid crystal display device according to claim 1 or 2, wherein the total cross-sectional area of the plurality of first spacers is smaller than the total cross-sectional area of the plurality of second spacers. The ratio of the total cross-sectional area of the plurality of first spacers to the total cross-sectional area of the plurality of second spacers is the ratio of the height of one of the plurality of first spacers to the height of one of the plurality of second spacers. The liquid crystal display device according to claim 1 or 2.

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