JP2018124398A - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device with improved display quality.SOLUTION: A liquid crystal display device 10 has first and second substrates 11, 21 disposed opposite each other, a liquid crystal layer 31 disposed between the first substrate 11 and the second substrate 21, a black mask 14 disposed on the first substrate 11 and composed of a black resin, an overcoating film 15 disposed on the first substrate 11 and the black mask 14, and a color filter 12 disposed on the overcoating film 15.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a liquid crystal display device.

  Since the liquid crystal display device has features such as small size, thin shape, light weight and low power consumption, it is widely used in various display devices such as mobile phones, personal computers, and televisions. The liquid crystal display device includes, for example, a color filter substrate having a color filter, a TFT substrate having a TFT (Thin Film Transistor), and a liquid crystal layer provided between the color filter substrate and the TFT substrate.

  The color filter substrate has, for example, a black mask (or black matrix) arranged on the glass substrate so as to cover the periphery of the pixel region (or opening region), and a color filter that determines the color of the pixel. A plurality of color filters are provided on the pixel region of the color filter substrate and on the black mask. Photo spacers that determine the thickness of the liquid crystal layer at certain distances are provided at the overlapping portions of the color filters on the black mask. The black mask has a function to prevent light from being blocked by the TFT and the photo spacer and to prevent color mixing of different color filters adjacent to each other.

  For the black mask, for example, chromium (Cr) or resin is used. When a resin is used for the black mask, it is necessary to increase the film thickness in order to maintain the light shielding property as compared with the case of using chromium. For this reason, the height difference between the color filters arranged on the pixel region and the black mask is increased, and the height of the color filter in the vicinity of the black mask in the pixel region is increased to increase the region where the liquid crystal alignment is disturbed. As a result, the contrast in the display area is lowered, and the display quality of the liquid crystal display device is degraded.

  A photo spacer is disposed on the color filter on the black mask. When the position of the photo spacer is shifted to the pixel region side in the manufacturing process, the height difference between the color filters on the pixel region and the black mask is large, so that the photo spacer is greatly displaced in the height direction. As a result, the thickness of the liquid crystal layer cannot be kept uniform, and the display quality of the liquid crystal display device is degraded.

JP2013-238729A

  The present invention provides a liquid crystal display device capable of improving display quality.

  A liquid crystal display device according to an aspect of the present invention includes a first substrate and a second substrate disposed to face each other, a liquid crystal layer disposed between the first substrate and the second substrate, and the first substrate. And a black mask made of black resin, an overcoat film disposed on the first substrate and the black mask, and a color filter disposed on the overcoat film.

  ADVANTAGE OF THE INVENTION According to this invention, the liquid crystal display device which can improve display quality can be provided.

It is a top view of the liquid crystal display device of the embodiment of the present invention. It is sectional drawing along the AA 'line of the liquid crystal display device of embodiment shown in FIG. It is sectional drawing along the BB 'line | wire of the liquid crystal display device of embodiment shown in FIG. It is sectional drawing of the liquid crystal display device of a 1st comparative example. It is other sectional drawing of the liquid crystal display device of a 1st comparative example. It is sectional drawing of the liquid crystal display device of a 2nd comparative example. It is other sectional drawing of the liquid crystal display device of the 2nd comparative example.

  Hereinafter, embodiments will be described with reference to the drawings. However, it should be noted that the drawings are schematic or conceptual, and the dimensions and ratios of the drawings are not necessarily the same as the actual ones. Further, even when the same portion is represented between the drawings, the dimensional relationship and ratio may be represented differently. In particular, the following embodiments exemplify an apparatus and a method for embodying the technical idea of the present invention, and the technical idea of the present invention depends on the shape, structure, arrangement, etc. of components. Is not specified. In the following description, elements having the same function and configuration are denoted by the same reference numerals, and redundant description will be given only when necessary.

[Embodiment]
A liquid crystal display device according to an embodiment of the present invention will be described.

[1] Configuration of Liquid Crystal Display Device FIG. 1 is a plan view of a liquid crystal display device 10 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the liquid crystal display device 10 taken along line AA ′ in FIG. FIG. 3 is a cross-sectional view of the liquid crystal display device 10 taken along line BB ′. FIG. 1 shows some black masks, color filters, photo spacers, pixels, TFTs, and the like of the liquid crystal display device 10, and others are omitted.

  The liquid crystal display device 10 includes a first substrate (hereinafter referred to as a color filter substrate or a CF substrate) 11 on which a color filter 12 and a common electrode 13 are formed, a switching element such as a TFT (Thin Film Transistor) 16, and a pixel. A second substrate (hereinafter referred to as a TFT substrate) 21 on which an electrode 22 and the like are formed and is disposed to face the CF substrate 11 is provided. Each of the CF substrate 11 and the TFT substrate 21 is composed of a transparent substrate (for example, a glass substrate). For example, the TFT substrate 21 is disposed to face a backlight (not shown), and illumination light from the backlight enters the liquid crystal display device 10 from the TFT substrate 21 side.

  A liquid crystal layer 31 is filled between the CF substrate 11 and the TFT substrate 21. Specifically, the liquid crystal layer 31 is sealed in a display region surrounded by the CF substrate 11 and the TFT substrate 21 and a sealing material (not shown).

  The liquid crystal material composing the liquid crystal layer 31 has its optical characteristics changed by manipulating the orientation of liquid crystal molecules according to the electric field applied between the CF substrate 11 and the TFT substrate 21. As the liquid crystal mode, various liquid crystal modes such as a VA (Vertical Alignment) mode, a TN (Twisted Nematic) mode, an IPS (In-Place-Switching) mode, and a homogeneous mode can be used.

  The sealing material is made of, for example, an ultraviolet curable resin, a thermosetting resin, or an ultraviolet / heat combined type curable resin, and is applied to the CF substrate 11 or the TFT substrate 21 in the manufacturing process and then cured by ultraviolet irradiation or heating. Is done.

  Next, the configuration on the CF substrate 11 side will be described. A black mask (also referred to as a black matrix or a light shielding film) 14 for light shielding is provided on the liquid crystal layer 31 side of the CF substrate 11. The black mask 14 is disposed at the boundary portion of the pixel 14P and is formed in a mesh shape. The black mask 14 has a function of shielding the TFT 16 and a function of improving contrast by shielding unnecessary light between different color filters. The black mask 14 is formed from, for example, a black resin. The film thickness of the black mask 14 is, for example, about 0.5 to 1.0 μm.

  An overcoat film 15 is provided on the CF substrate 11 and the black mask 14. The overcoat film 15 fills the steps of the black mask 14 disposed on the CF substrate 11 and planarizes the CF substrate 11. In other words, the upper surface of the overcoat film 15 is flattened. The overcoat film 15 is made of a transparent resin such as an acrylic resin. The film thickness of the overcoat film 15 is a film thickness that can flatten the CF substrate 11 on which the black mask 14 is disposed, for example, about 1.5 to 2.0 μm.

  A plurality of color filters 12 are provided on the overcoat film 15. The plurality of color filters (color members) 12 include a plurality of red filters 12R, a plurality of green filters 12G, and a plurality of blue filters 12B. A general color filter is composed of three primary colors of light, red (R), green (G), and blue (B). A set of three colors R, G, and B adjacent to each other is a display unit (pixel), and any single color portion of R, G, B in one pixel is a minimum called a sub-pixel (sub-pixel). It is a drive unit. The TFT 16 and the pixel electrode 22 are provided for each sub-pixel. In the following description, a subpixel is referred to as a pixel unless it is particularly necessary to distinguish between a pixel and a subpixel. The film thickness of the color filter 12 is, for example, about 1.0 to 2.0 μm.

  FIG. 1 shows a stripe arrangement as a color filter arrangement system (or pixel arrangement system). The stripe arrangement is an arrangement in which pixels included in the same row (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 as the arrangement method of the color filters.

  As shown in FIG. 2, two types of color filters 12 are provided on the overcoat film 15 on the black mask 14 so as to overlap each other. That is, the two types of color filters 12 partially overlap above the black mask 14. The surface of the overcoat film 15 on the CF substrate 11 (on the pixel 14P) and on the black mask 14 is substantially planarized. Therefore, there is almost no step between the pixel 14P and the black mask 14 (or the step is reduced), and the step generated in the vicinity of the black mask 14 of the pixel 14P is the minimum generated by the overlap of two types of color filters. It can be suppressed to the level difference.

  A common electrode 13 is provided on the color filter 12. The common electrode 13 is formed in a planar shape over the entire display area of the liquid crystal display device 10. The common electrode 13 is composed of a transparent electrode. For the common electrode 13, for example, ITO (indium tin oxide) is used.

  As shown in FIG. 3, a photo spacer 17 is provided on the common electrode 13 in the overlapping portion of the color filter on the black mask 14. The photo spacer 17 adjusts the thickness of the liquid crystal layer 31 between the CF substrate 11 and the TFT substrate 21. Here, when the photo spacer 17 is disposed on the black mask 14, the position of the photo spacer 17 may be shifted from the black mask 14 (overlapping portion of the color filter) in the manufacturing process. In this embodiment, the step of the black mask 14 is reduced by the overcoat film 15 applied on the CF substrate 11, and the surface of the overcoat film 15 on the CF substrate 11 is almost flattened. For this reason, even when the position of the photo spacer 17 is shifted from the black mask 14 toward the pixel 14P, variation in the height of the photo spacer 17 can be reduced. The height from the bottom surface to the top surface of the photo spacer 17 is, for example, about 3.0 to 4.0 μm.

  As an example, when the arrangement pitch in the X direction of the black mask 14 is 16 to 30 μm, the thickness of the color filter 12 is 1 to 2 μm, and the diameter of the bottom surface of the photo spacer 17 is 12 μm, the X of the black mask 14 The width in the direction is about 5 μm, and the width in the Y direction is about 9 μm.

  Next, the configuration on the TFT substrate 21 side will be described. A plurality of switching elements (active elements), for example, TFTs 16 are provided on the liquid crystal layer 31 side of the TFT substrate 21. For example, an n-channel TFT is used as the TFT 16. As will be described later, the TFT 16 includes a gate electrode 23 electrically connected to the scanning line, a gate insulating film 24 provided on the gate electrode 23, a semiconductor layer 25 provided on the gate insulating film 24, A source electrode and a drain electrode (not shown) provided separately from each other on the semiconductor layer 25 are provided. The source electrode is electrically connected to the signal line 26.

  The configuration on the TFT substrate 21 side will be described with reference to FIG. A plurality of gate electrodes 23 each extending in the X direction are provided on the liquid crystal layer 31 side of the TFT substrate 21. A gate insulating film 24 is provided on the liquid crystal layer 31 side on the plurality of gate electrodes 23. A plurality of pixels for one row arranged in the X direction share one gate electrode 23. The gate insulating film 24 is made of a transparent insulating material. For the gate insulating film 24, for example, silicon nitride (SiN) is used.

  A plurality of semiconductor layers 25 corresponding to the plurality of TFTs 16 are provided on the gate insulating film 24. For example, an amorphous silicon layer is used as the semiconductor layer 25. On one semiconductor layer 25 and the gate insulating film 24, a source electrode and a drain electrode which are separated from each other are provided. The source electrode is electrically connected to a signal line 26 extending in the Y direction. A plurality of pixels for one column arranged in the Y direction are commonly connected to one signal line 26.

  Examples of the gate electrode 23, the source electrode, the drain electrode, and the signal line 26 include aluminum (Al), molybdenum (Mo), chromium (Cr), tungsten (W), or one or more of these. An alloy or the like is used.

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

  On the insulating film 27, as shown in FIG. 2, a plurality of pixel electrodes 22 corresponding to the plurality of pixels 14P are provided. The pixel electrode 22 is electrically connected to the drain electrode. The pixel electrode 22 is composed of a transparent electrode. For example, ITO (indium tin oxide) is used for the pixel electrode 22. The TFT 16 is controlled to be in an on state or an off state by the voltage of the gate electrode 23, and switches the voltage application to the pixel electrode 22 to either the applied state or the cutoff state. Further, an alignment film (not shown) for controlling the alignment of the liquid crystal layer 31 is provided on the surface in contact with the liquid crystal layer 31.

  Although not shown, the liquid crystal display device 10 includes a pair of polarizing plates (linear polarizers) and a pair of retardation plates (¼ wavelength plates) with the CF substrate 11 and the TFT substrate 21 sandwiched from both sides. Is provided.

[2] Comparative Example A comparative example will be described below. As a first comparative example, an example in which a black mask 14 made of resin is disposed on the CF substrate 11 and the color filter 12 is disposed on the black mask 14 will be described. 4 and 5 are cross-sectional views on the CF substrate 11 side of the first comparative example along the lines corresponding to the lines AA ′ and BB ′ in FIG. 1.

  In the first comparative example, the color filter 12 is disposed so as to overlap the CF substrate 11 having the steps of the black mask 14. For this reason, the height of the color filter in the vicinity of the black mask 14 (the boundary region between the pixel 14P and the black mask 14) becomes higher than the height of the color filter on the pixel 14P, and the liquid crystal alignment is disturbed in the vicinity of the black mask 14. As a result, the contrast in the display area is lowered, and the display quality of the liquid crystal display device may be lowered.

  In this embodiment, an overcoat film 15 is provided on the CF substrate 11 on which the black mask 14 is disposed. Thereby, the step of the black mask 14 generated on the CF substrate 11 is eliminated or reduced by the overcoat film 15, and the CF substrate 11 on which the color filter 12 is to be arranged is planarized. As a result, the height of the color filter 12 in the vicinity of the black mask 14 can be reduced, and the region where the liquid crystal alignment is disturbed can be reduced. As a result, for example, it is possible to prevent light leakage from occurring in the vicinity of the black mask 14, reducing the contrast in the display region and degrading the display quality of the liquid crystal display device.

  Further, in the first comparative example, a photo spacer 17 is disposed on the color filter 12 on the black mask 14. When the position of the photo spacer 17 is shifted in the manufacturing process, the height difference between the color filters on the pixel and the black mask 14 is large, and thus the blur in the height direction of the photo spacer 17 increases. As a result, the layer thickness of the liquid crystal layer cannot be kept uniform, and the display quality of the liquid crystal display device may deteriorate.

  In the present embodiment, as described above, the overcoat film 15 is provided on the CF substrate 11 on which the black mask 14 is disposed, and the steps of the black mask 14 on the CF substrate 11 are planarized by the overcoat film 15. . Thereby, even when the photo spacer 17 is removed from the black mask 14, the variation in the height of the photo spacer 17 can be reduced, and deterioration of display quality can be prevented.

  Next, as a second comparative example, an example in which the positional deviation of the photo spacer 17 is taken will be described. 6 and 7 are cross-sectional views on the CF substrate 11 side of the second comparative example along the lines corresponding to the lines AA ′ and BB ′ in FIG. 1.

  In the second comparative example, the color filter 12 is eliminated from the portion where the photo spacer 17 on the black mask 14 is disposed. In this case, it is necessary to increase the width of the black mask 14 in the Y direction in consideration of the alignment accuracy of the photo spacer 17, the black mask 14, and the color filter 12. For example, the width of the black mask 14 in the Y direction is about 30 μm. Then, the aperture ratio in the display area is lowered.

  In this embodiment, since it is not necessary to increase the width of the black mask 14, there is no decrease in the aperture ratio in the display area.

[3] Effect As described above, in this embodiment, the overcoat film 15 is provided on the CF substrate 11 on which the black mask 14 is disposed. Thereby, the step of the black mask 14 on the CF substrate 11 is filled with the overcoat film 15, and the CF substrate 11 is planarized with the overcoat film. By this flattening, it is possible to reduce the height of the color filter 12 in the vicinity of the black mask 14 (the boundary region between the pixel 14P and the black mask 14) from above the pixel 14P, and it is possible to reduce the region where the liquid crystal alignment is disturbed. As a result, light leakage occurring in the vicinity of the black mask 14 can be reduced, and a reduction in contrast in the display area can be prevented. Further, when a part or all of the photo spacer 17 is displaced from a desired position on the black mask 14, for example, even when it is displaced on the pixel 14P, variation in the height of the photo spacer 17 can be reduced, and the liquid crystal layer The layer thickness can be kept uniform.

  As described above, according to the present embodiment, by realizing at least one of prevention of a decrease in contrast in the display region, reduction in variation in the height of the photo spacers 17, and prevention of a decrease in the aperture ratio of the display region, Quality deterioration can be prevented. That is, display quality in the liquid crystal display device can be improved.

  In the present embodiment, the case where a resin is used for the black mask 14 has been described. However, the present invention can also be applied to the case where a material other than a resin is used for the black mask. That is, the present invention can be applied to the case where the film thickness of the black mask is increased and the film thickness causes problems. In addition, the use of a resin for the black mask is advantageous in that the product cost can be reduced compared to the case of using chromium.

Further, the present embodiment can also be applied to a liquid crystal display device having a multi-gap structure.
In a liquid crystal display device having a multi-gap structure, for example, the thickness of the liquid crystal layer is different for each of a red filter, a green filter, and a blue filter. Also in such a multi-gap structure liquid crystal display device, in this embodiment, the overcoat film 15 is provided on the CF substrate 11 on which the black mask 14 is arranged, and the color filter 12 is arranged on the overcoat film. A multi-gap structure can be easily formed.

  The present invention is not limited to the above embodiment, and can be embodied by modifying the constituent elements without departing from the scope of the invention. Further, the above embodiments include inventions at various stages, and are obtained by appropriately combining a plurality of constituent elements disclosed in one embodiment or by appropriately combining constituent elements disclosed in different embodiments. Various inventions can be configured. For example, even if some constituent elements are deleted from all the constituent elements disclosed in the embodiments, the problems to be solved by the invention can be solved and the effects of the invention can be obtained. Embodiments made can be extracted as inventions.

  DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display device 11 ... 1st board | substrate (color filter board | substrate, 12 ... color filter, 12R ... red filter, 12G ... green filter, 12B ... blue filter, 13 ... common electrode, 14 ... black mask (black matrix or light-shielding) Film), 14P ... pixel, 15 ... overcoat film, 16 ... TFT (Thin Film Transistor), 21 ... second substrate (TFT substrate), 22 ... pixel electrode, 23 ... gate electrode, 24 ... gate insulating film, 25 ... Semiconductor layer, 26 ... signal line, 27 ... insulating film, 31 ... liquid crystal layer.

Claims (8)

First and second substrates disposed opposite to each other;
A liquid crystal layer disposed between the first substrate and the second substrate;
A black mask disposed on the first substrate and made of a black resin;
An overcoat film disposed on the first substrate and the black mask;
A color filter disposed on the overcoat film;
A liquid crystal display device comprising:   The liquid crystal display device according to claim 1, wherein an upper surface of the overcoat film is flattened.   The liquid crystal display device according to claim 1, wherein the overcoat film includes an acrylic resin. The color filter includes first and second color filters;
The liquid crystal display device according to claim 1, wherein the first and second color filters partially overlap above the black mask.   The liquid crystal display device according to claim 4, further comprising a spacer that is disposed above an overlapping portion of the first and second color filters and adjusts a thickness of the liquid crystal layer.   The liquid crystal display device according to claim 1, further comprising a transparent electrode disposed on the color filter.   The pixel electrode and a switching element that switches voltage application to the pixel electrode between an applied state and a cut-off state are disposed on the second substrate. Liquid crystal display device.   The liquid crystal display device according to claim 1, wherein the black mask has a thickness of 0.5 to 1 μm.