JP5009087B2 - Liquid crystal display device and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device in which spectral reflectance of a black matrix is controlled to be lowest at a peak wavelength in the absorption spectrum of a-Si by taking the emission spectrum of a backlight into consideration, and the light leakage current of a TFT is decreased. <P>SOLUTION: The liquid crystal display device is equipped with: an array substrate having a TFT having a semiconductor film formed in each pixel region; a color filter substrate; and a backlight. A black matrix on the color filter substrate comprises a metallic light shielding film and antireflection films formed on both faces of the metal light shielding film, in which the film thickness of the antireflection film on the side of the array substrate is controlled to satisfy such a condition that the bottom wavelength in the spectral reflection of the antireflection film on the side of the array substrate for the light from the backlight overlaps the peak wavelength of the spectral sensitivity of a light leakage current in the semiconductor film. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

The present invention can be manufactured in a liquid crystal display panel using a backlight, particularly without significant changes in the conventional manufacturing process, and has a TFT (thin film transistor: Thin) having a semiconductor film caused by reflected light from a black matrix of a color filter substrate. The present invention relates to a liquid crystal display device with a good display image quality in which a light leakage current of a film transistor is reduced.

A TFT using a semiconductor film such as amorphous silicon (a-Si) or polysilicon (p-Si) as an active layer (channel region) is caused by electron-hole pairs when the active layer is irradiated with light. A photocurrent is generated, and the leakage current when the TFT is off increases. Therefore, in a liquid crystal display panel provided with a TFT using a semiconductor film as a switching element, when the TFT is irradiated with light, the display image quality deteriorates due to the occurrence of crosstalk, a decrease in contrast, etc. due to this light irradiation. There is a problem.

Therefore, in the conventional liquid crystal display panel, the TFT channel is formed by providing a light-shielding film on the counter substrate (see paragraph [0003] of Patent Document 1 below) or by forming the light-shielding film above and below the TFT. A region and its peripheral region are shielded from light (see Patent Document 2 below). Furthermore, the TFT is formed as a bottom gate type (also referred to as an inverted stagger type) formed on the upper side of the gate electrode, and the light from the backlight is shielded by the light shielding film or the gate electrode. The direct light from the backlight is not applied (see Patent Documents 1 and 3 below). Among these, the bottom gate type TFT has a gate electrode or a scanning line below the TFT, so that the gate electrode or the scanning line can also function as a lower light shielding film of the TFT.

However, in recent years, since liquid crystal display panels have been required to have a bright display, a light source comprising a cold cathode tube or a light emitting diode (LED) having higher luminance (for example, 10,000 cd or more) as a backlight. Are beginning to be used. When such a high-brightness backlight is used, light leakage current generated in the TFT due to stray light, reflected light, or the like increases in proportion to the brightness of the backlight. Also,
It has been found that when a high-brightness backlight is used, a light leakage current flows through the TFT also by reflected light from the light shielding film on the color filter substrate side. This phenomenon will be described with reference to FIGS.

FIG. 11 is a plan view of several pixels viewed from the color filter substrate side of a conventional liquid crystal display panel. 12 is a schematic cross-sectional view taken along line XII-XII in FIG. FIG. 13 is an enlarged view of the XIII portion of FIG. 12 for explaining the principle of reflected light entering the TFT.

The liquid crystal display panel 50 includes an array substrate AR and a color filter substrate CF. The a-Si layer 52 is formed in each pixel region on the transparent substrate 51 made of a glass substrate or the like of the array substrate AR.
A TFT having (see FIG. 13) is formed. Note that T having the a-Si layer 52 is provided.
Since the configuration of the FT is the same as that in the embodiments described later, detailed description thereof is omitted here. On the transparent substrate 53 of the color filter substrate CF, a black matrix 55 made of, for example, chromium metal is formed at positions corresponding to the scanning lines (not shown), the signal lines 54, and the TFTs of the array substrate AR. In the region surrounded by the matrix 55, for example, three color filter layers 56R, 56G, and 56B of R, G, and B are formed in a stripe shape.

11 to 13, the black matrix 55 has positions corresponding to the scanning lines, the signal lines 54, and the TFTs on the array substrate AR on the surface of the transparent substrate 53 on the color filter substrate CF side. It is formed so as to be shielded from light. In addition, as shown in FIG. 12, the color filter layers 56R, 56G, and 56B are formed in stripes so that each of R, G, and B partially overlaps the black matrix 55.
In the liquid crystal display panel 50, as shown in FIG. 13, when the incident light from the backlight hits the black matrix 55, a part of the incident light is reflected and the a-Si layer 5 of the TFT.
2 is incident. Therefore, as the luminance of the backlight increases, the light leakage current of the TFT increases in proportion thereto.

In order to reduce the light leakage current of the TFT caused by light from such a backlight,
In Patent Document 1 below, a liquid crystal display panel in which a chromium oxide film, a chromium film, and a chromium oxide film are laminated as a black matrix formed on the counter substrate side, and the inner surface side of the counter substrate is made low reflective. The invention is disclosed. Similarly, in Patent Document 3 below, the black matrix formed on the opposite substrate side is made of a laminated structure of a chromium oxide film, a chromium metal film, and a chromium oxide film, so that it is incident between the upper and lower glass substrates from an oblique direction. An invention of a liquid crystal display device that prevents multiple reflection of light is disclosed.
JP 2001-290440 A JP 2000-298290 A JP-A-9-96838

According to the inventions disclosed in Patent Documents 1 to 3 described above, not only incident light from the outside but also light from the backlight can be prevented from entering the channel region of the TFT. However, particularly in the case of the bottom gate type TFT structure, the black matrix and the channel region are considerably separated from each other through, for example, a drain electrode, a source electrode, an interlayer insulating film, and the like when viewed three-dimensionally. Therefore, in a liquid crystal display panel using a bottom-gate TFT structure, even if the above-described conventional technology is applied, the light shielding property against the light that is obliquely incident between the black matrix and the channel region and the reflected light still remains. Is insufficient.

For example, the photocurrent spectral peak wavelength of a TFT using a-Si is 450 to 500 nm.
Therefore, the light leakage current changes depending on the wavelength of light incident on the channel region of the TFT, but the emission intensity of the backlight changes greatly depending on the wavelength. For this reason, in order to reduce the light leakage current of TFTs using a-Si, not only the spectral reflectance of the antireflection film but also the light emission spectrum of the backlight is taken into consideration and the light leakage current spectral characteristics of the TFT are multiplied. It is necessary to consider the integrated value.

On the other hand, the chromium oxide / chromium metal / chromium oxide three-layer laminated type light shielding film as disclosed in Patent Documents 1 to 3 is a normal two-layer chromium light shielding film in which the chromium metal surface is exposed inside the cell. It can be seen that the reflectivity is reduced for the film. However, the invention disclosed in the above-mentioned patent document 1 is different from the glass substrate with the naked eye by changing the wavelength in the visible light region where the reflectance of the chromium oxide film formed on both sides of the chromium metal film is almost minimized. The surface side and the light-shielding film side can be distinguished, and the back and front sides of the substrate can be easily identified at the time of manufacture. Therefore, the above-mentioned Patent Document 1 does not disclose anything about the relationship between the wavelength in the visible light region where the reflectance of the chromium oxide film is substantially minimized and the light leakage current of the TFT, and the backlight The relationship between the emission spectrum of the TFT and the light leakage current of the TFT is not shown. Also, Patent Documents 2 and 3 have no description suggesting the relationship between the emission spectrum of the backlight and the light leakage current of the TFT.

If a further low reflectance is required for the light-shielding film, a photosensitive resin black resist can be used. In order to obtain a high light-shielding property with an OD (Optical Density) value of 3 or more, Since it is necessary to make the film thickness as very thick as about 1 μm, the flatness of the peripheral portion of the display pixel is deteriorated. Further, the patterning accuracy of the resin light-shielding film by the photolithography method is low, and the width of the light-shielding layer line is around 10 μm, so that a small liquid crystal display panel that requires a high-definition pixel pitch leads to a decrease in aperture ratio, which is disadvantageous. .

The present invention has been developed in view of the above-mentioned problems of the prior art, and its purpose is to consider the spectral reflectance of the black matrix formed on the counter substrate in consideration of the emission spectrum of the backlight. TF is set to the lowest value at the peak wavelength of the absorption spectrum of the film.
An object of the present invention is to provide a liquid crystal display device that reduces the light leakage current of T, is bright, and has a good display image quality.

In order to achieve the above object, a liquid crystal display device of the present invention includes an array substrate in which a TFT having a semiconductor layer is formed in each pixel region surrounded by scanning lines and signal lines arranged in a matrix,
In a liquid crystal display device including a color filter substrate including a black matrix formed at a position corresponding to the scanning line, the signal line, and the TFT, and a backlight, the black matrix includes a light shielding film made of metal, An anti-reflection film formed on both sides of the metal light-shielding film, and the film thickness of the anti-reflection film on the array substrate side is determined by spectral reflection of the anti-reflection film on the array substrate side by light from the backlight The bottom wavelength of the semiconductor layer has a thickness that overlaps the peak wavelength of the spectral sensitivity of the light leakage current of the semiconductor layer.

The light leakage current of a TFT having an a-Si layer that is a semiconductor film is wavelength-dependent, and
The emission spectrum of the light from the backlight differs depending on the type of the light source. The antireflection film can change the bottom wavelength of the reflected light by changing its thickness. In the liquid crystal display panel of the present invention, the bottom wavelength of the spectral reflection of the antireflection film on the array substrate side by the light from the backlight overlaps the peak wavelength of the spectral sensitivity of the light leakage current of the semiconductor layer. Since the thickness is set, the reflected light having the wavelength that causes the light leakage current of the TFT is weakened.

Therefore, according to the liquid crystal display device of the present invention, the light leakage current of the TFT due to the reflected light from the black matrix does not increase even when a high-brightness backlight is used.
A liquid crystal display device with good display image quality can be obtained. In addition, according to the liquid crystal display panel of the present invention, the light leakage current of the TFT can be effectively reduced even with respect to the obliquely incident light in the TFT having the bottom gate structure, which has been difficult to cope with with the prior art. Furthermore, according to the liquid crystal display device of the present invention, since it is not necessary to use a resin black matrix, there is no deterioration in the flatness of the pixel portion,
A high aperture ratio can be maintained even in high definition models with a narrow black matrix width.

In the liquid crystal display device of the present invention, the metal light shielding film is made of chromium metal,
The antireflection film is preferably made of chromium oxide.

Chromium metal is a general-purpose light-shielding film forming material, and chromium oxide is a general-purpose anti-reflection film-forming material used in combination with a light-shielding film made of chromium metal. well known. Therefore, according to the liquid crystal display device of such an embodiment, the peak wavelength of the spectral sensitivity of the light leakage current of the semiconductor film and the bottom wavelength of the spectral reflection of the antireflection film by the light from the backlight can be more accurately superimposed, Thus, a liquid crystal display device having a smaller TFT light leakage current, brighter and better display image quality can be obtained.

In the liquid crystal display device of the present invention, it is preferable that the thickness of the antireflection film on the array substrate side is such that the bottom wavelength of spectral reflection is 350 nm to 550 nm.

The light leakage current of a TFT having an a-Si layer as a semiconductor layer has a wavelength of 350 to 550 nm.
Has a peak. Further, a cold-cathode tube generally used as a backlight of a liquid crystal display panel has an emission peak wavelength in the vicinity of 490 nm, and in the case of a white LED, the emission peak wavelength is in the vicinity of 450 nm. Therefore, the reflection light having the wavelength that causes the light leakage current of the TFT is weakened by setting the film thickness of the antireflection film on the array substrate side so that the bottom wavelength of spectral reflection is 350 nm to 550 nm. be able to. Therefore, according to the liquid crystal display device of such an aspect, a liquid crystal display device that has a light leakage current of TFT, is brighter, and has a good display image quality can be obtained.

In the liquid crystal display device of the present invention, the thickness of the antireflection film made of chromium oxide on the array substrate side is preferably 350 to 600 mm.

When the antireflection film is made of chromium oxide, the bottom wavelength of spectral reflection of the antireflection film can be 350 nm to 550 nm when the thickness of the antireflection film is 350 to 600 mm. Therefore, according to the liquid crystal display panel of this aspect, a liquid crystal display panel having a small light leakage current of the TFT, being bright, and having a good display image quality can be obtained.

In the liquid crystal display device of the present invention, it is preferable that the antireflection film on the side opposite to the array substrate has a spectral reflection bottom wavelength of 500 nm to 550 nm.

Visibility of human eyes is highest in the green region with a wavelength of about 500 nm to 550 nm. Therefore, the thickness of the antireflection film on the side opposite to the array substrate is set so that the bottom wavelength of spectral reflection is 500 nm to 550 nm.
As a result, the black matrix portion looks darkest to the eyes of the observer. Therefore, according to the liquid crystal display device of this aspect, it is possible to obtain a liquid crystal display device that has a good contrast and a small light leakage current of the TFT, is bright, and has a good display image quality.

In the liquid crystal display device of the present invention, it is preferable that the thickness of the antireflection film made of chromium oxide on the side opposite to the array substrate is 450 mm to 550 mm.

When the antireflection film is made of chromium oxide and the film thickness of the antireflection film is set to 450 mm to 550 mm, the spectral reflection bottom wavelength of the antireflection film is 500 nm in the green region where human visibility is the best.
It can be set to ˜550 nm. Therefore, according to the liquid crystal display device of this aspect, it is possible to obtain a liquid crystal display device that has a good contrast and a small light leakage current of the TFT, is bright, and has a good display image quality.

Furthermore, in order to achieve the above object, an electronic apparatus according to the present invention includes any one of the liquid crystal display devices described above.

According to the electronic device of the present invention, it is possible to obtain an electronic device including a liquid crystal display device in which the light leakage current of the TFT is small and bright and the display image quality is good.

The best mode for carrying out the present invention will be described below with reference to the drawings and examples and various experimental examples.
However, the embodiment shown below is a liquid crystal display device for embodying the technical idea of the present invention.
A transmissive liquid crystal display panel in which liquid crystal is sandwiched between a pair of substrates (for example, an array substrate and a color filter substrate) is illustrated, and the present invention is not intended to be specified as this transmissive liquid crystal display panel. Rather, it is equally applicable to other embodiments within the scope of the claims.

FIG. 1 is a schematic plan view of one pixel of the array substrate seen through the color filter substrate of the transmissive liquid crystal display panel of the embodiment. FIG. 2 is a sectional view taken along line II-II in FIG. FIG. 3 is a dynamic characteristic diagram of a general TFT. FIG. 4 is a circuit diagram of a spectral light leakage current measurement circuit of a TFT.
FIG. 5 is a spectral light leakage current characteristic diagram of a TFT having an a-Si layer. FIG. 6 is a cross-sectional view of a substrate for measuring spectral reflectance of a chromium oxide film. FIG. 7 is a diagram showing the relationship between the thickness L of the chromium oxide film and the spectral reflectance. FIG. 8 is a spectral light leakage current characteristic diagram of a TFT having an a-Si layer in a liquid crystal display device using a cold cathode tube as a backlight. Emission spectrum of white LED as backlight, spectral reflection intensity of antireflection film, and TF having a-Si layer
It is a spectral light leakage current characteristic diagram of T. FIG. 10A is a diagram showing a personal computer equipped with the liquid crystal display panel of the present invention, and FIG. 10B is a diagram showing a mobile phone equipped with the liquid crystal display panel of the present invention.

In the following description, a TFT using an a-Si layer as a general semiconductor layer will be described as an example. First, the specific configuration of each pixel of the liquid crystal display panel 10 of the embodiment will be described with reference to FIGS.
Will be described. The liquid crystal display panel 10 includes an array substrate AR and a color filter substrate C.
F is provided. On the transparent substrate 11 such as glass of the array substrate AR, a plurality of scanning lines 12 are formed in parallel at equal intervals, and a gate electrode G of the TFT is extended from the scanning line 12. Similarly, on the transparent substrate 11, the auxiliary capacitance line 13 is formed between the adjacent scanning lines 12 so as to be parallel to the scanning line 12. The auxiliary capacitance line 13 is wider than the auxiliary capacitance line 13. An auxiliary capacitance electrode 14 is formed.

Further, a gate insulating film 15 made of silicon nitride, silicon oxide or the like is laminated on the entire surface of the transparent substrate 11 so as to cover the scanning lines 12, the auxiliary capacitance lines 13, the auxiliary capacitance electrodes 14, and the gate electrodes G. An a-Si layer 16 is formed on the gate electrode G via a gate insulating film 15. A plurality of signal lines 17 are formed on the gate insulating film 15 so as to intersect the scanning lines 12, and a TFT source electrode S is extended from the signal line 17 so as to be in contact with the a-Si layer 16. Furthermore, the drain electrode D made of the same material as the signal line 17 is also a-
It is provided on the gate insulating film 15 so as to be in contact with the Si layer 16.

Here, a region surrounded by the scanning lines 12 and the signal lines 17 corresponds to one pixel. The gate electrode G, the gate insulating film 15, the a-Si layer 16, the source electrode S, and the drain electrode D constitute a TFT serving as a switching element, and this TFT is formed in each pixel. In this case, the auxiliary capacitance of each pixel is formed by the drain electrode D and the auxiliary capacitance electrode 14.

A protective insulating film 18 (also referred to as a passivation film) 18 made of, for example, silicon nitride or silicon oxide is laminated over the entire surface of the transparent substrate 11 so as to cover the signal lines 17, TFTs, and the gate insulating film 15. A planarizing film 19 (also referred to as an interlayer film) made of an organic insulating film is laminated over the entire transparent substrate 11. And protective insulating film 1
8 and the planarizing film 19 have contact holes 20 at positions corresponding to the drain electrodes D of the TFTs.
Is formed. Further, in each pixel, a pixel electrode 21 made of, for example, ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide) is formed on the surface of the contact hole 20 and the planarizing film 19, and all of the pixel electrodes 21 are formed on the surface of the pixel electrode 21. An alignment film (not shown) is stacked so as to cover the pixels.

The color filter substrate CF has a black matrix 23 formed on the surface of the transparent substrate 22 such as a glass substrate so as to shield the positions corresponding to the scanning lines 12, the signal lines 17 and the TFTs of the array substrate AR. Yes. The black matrix 23 is composed of, for example, three layers of a chromium oxide film 23a having a thickness of about 500 mm, a chromium metal film 23b having a thickness of about 1200 mm, and a chromium oxide film 23c having a thickness of about 400 mm from the surface side of the transparent substrate 22. It has become a structure.
The reason why the thickness of each layer of the black matrix 23 is specified in this way will be described later.

Further, for example, red (R), green (G), and blue (B) corresponding to each pixel so as to partially overlap the black matrix 23 at each position partitioned by the black matrix 23. A color filter layer 24 is provided. Further, a common electrode 25 and an alignment film (not shown) are stacked on the surface of the color filter layer 24. In addition, as the color filter layer 24, a color filter layer of complementary colors such as cyan (C), magenta (M), and yellow (Y) may be used in appropriate combination. In some cases, no layer is provided.

The array substrate AR and the color filter substrate CF thus obtained are opposed to each other, columnar spacers (not shown) for keeping the cell gap at the peripheral portion constant at appropriate intervals are arranged, and the array substrate The periphery of the AR and the color filter substrate CF is sealed with a sealing material, and the liquid crystal 26 is sealed between the substrates, whereby the liquid crystal display panel 10 is obtained.

Here, the reason why the thickness of each layer of the black matrix 23 is limited as described above will be described. First, the spectral sensitivity of light leakage current of a TFT having an a-Si layer was measured as follows. In general, as shown in FIG. 3, when the voltage below the gate-off voltage is applied to the gate electrode, a very small leakage current flows as shown in FIG. 3, but this leakage current increases when light strikes the TFT channel. It has characteristics. Therefore, here, a TFT having the same configuration as the TFT of the liquid crystal display panel 10 of the embodiment is manufactured alone, and the drain electrode D is grounded and Vs = 15 V is applied to the source electrode S as shown in FIG. Then, −10 V below the gate-off voltage was applied to the gate electrode G, and the light leaked was measured by irradiating the channel portion of the TFT with the dispersed light. The light leakage current was expressed as a current value normalized per unit energy and per channel length of 1 μm. The results are shown in FIG.

As shown in FIG. 5, the TFT having the semiconductor film (a-Si layer) has a wavelength of about 480 nm.
It was observed that photoleakage currents flow over a wide wavelength range of about 400 nm to 700 nm with peaks at about 550 nm and about 610 nm. Therefore, this FIG.
It is clear that it can be regarded as a spectral absorption curve of the i layer.

Next, as shown in FIG. 6, a chromium metal film having a thickness of 1200 mm is formed on the surface of the glass substrate, and a thickness L of a chromium oxide film as an antireflection film is set to 350 mm, 400 mm, and 45 on the surface.
Six types of samples were prepared in which the thickness was changed to 0 mm, 500 mm, 550 mm, and 600 mm. And the spectral reflectance was measured by irradiating light of a predetermined wavelength from the chromium oxide film side of these samples.
The results are shown in FIG. From the result shown in FIG. 7, the thickness L of the chromium oxide film is 350 to 600 mm.
By changing drastically, the bottom wavelength of spectral reflection of the chromium oxide film as the antireflection film can be changed in the range of 430 nm to 650 nm, and the reflectance can be reduced to about 10%. I understand.

Next, a cold-cathode tube generally used as a backlight is adopted as a light source, and FIG.
The sample was irradiated with backlight from the chromium oxide film side of the sample, and the thickness of the chromium oxide film L =
Spectral reflection intensity was measured when the thickness was 300 mm, 350 mm, 400 mm, and 550 mm. The measurement results of the spectral reflection intensity are shown together with the absorption spectrum of a-Si and the emission spectrum of the cold cathode tube in FIG. Note that the intensity of each spectrum shown in FIG. 8 is not an absolute value,
It is a relative value for ease of understanding.

As shown in FIG. 8, the light leakage current of the TFT having the a-Si layer has wavelengths of 480 nm and 5
It has a strong peak at 30 nm, and the cold cathode fluorescent lamp has an emission peak wavelength in the vicinity of a wavelength of 490 nm. Therefore, the antireflection film made of chromium oxide on the array substrate side has a wavelength of 490 n.
If the spectral bottom wavelength is in the range of 480 nm to 500 nm centering on m, the light leakage current of the TFT having the a-Si layer can be reduced most. The thickness L at which the spectral bottom wavelength of the antireflection film made of chromium oxide is close to 480 nm to 500 nm is
From the description of FIG. 7, L = 350 to 450 mm. Therefore, it can be seen that the thickness L of the antireflection film made of chromium oxide on the array substrate side is preferably 350 to 450 mm. In addition, according to the description of FIG. 8, when the thickness of the antireflection film made of chromium oxide is L = 350 mm and L = 400 mm, the wavelength including the light from the cold cathode tube as the backlight is 480 nm to
It can be confirmed that the spectral reflectance is lower in the range of 500 nm than in the case of L = 300Å and L = 550Å.

In addition, the bottom wavelength of spectral reflection is 550 nm to the thickness of the antireflection film opposite to the array substrate.
When the wavelength is set to 560 nm, the wavelength 550 nm to 560 nm has the highest visibility of the human eye.
Since the reflected light in the green region is weaker, the black matrix portion appears darkest to the viewer's eyes. From the description of FIG. 7, it can be seen that when the film thickness L of the chromium oxide film, which is an antireflection film having a spectral reflection bottom wavelength of 550 nm to 560 nm, is obtained by interpolation, about 490 to 510 mm is preferable.

Therefore, based on the measurement results, in the above example, the thickness of the chromium oxide film 23c on the array substrate side was about 400 mm, and the thickness of the chromium oxide film 23a on the side opposite to the array substrate was about 500 mm. According to the liquid crystal display panel of such an embodiment, the thickness of the antireflection film made of the chromium oxide film on the array substrate side is set so that the bottom wavelength of the spectral reflection of the antireflection film on the array substrate side by the light from the backlight is Since the thickness coincides with the peak wavelength of the spectral sensitivity of the light leakage current of the a-Si layer, the reflected light having the wavelength that causes the light leakage current of the TFT is the weakest. Therefore, according to the liquid crystal display device of the present invention, the light leakage current of the TFT caused by the reflected light from the black matrix does not increase even when a high-brightness backlight is used. A device is obtained.

Furthermore, according to the liquid crystal display device of the embodiment, the light leakage current of the TFT can be effectively reduced even with respect to the obliquely incident light in the TFT having the bottom gate structure, which has been difficult to cope with with the prior art. Further, since the resin black matrix is not used, the flatness of the pixel portion is not deteriorated, and a high aperture ratio can be maintained even in a high-definition model having a narrow black matrix width. In addition, according to the liquid crystal display panel of the embodiment, the wavelength 550n having the highest visibility of human eyes.
Since the reflected light in the green region of about m to 560 nm becomes weaker, the black matrix portion appears darkest to the eyes of the observer. Therefore, a liquid crystal display panel with good contrast is obtained.

In the above embodiment, the case where a cold cathode tube is used as a backlight has been described.
LEDs are also widely used as backlights. Therefore, in the following, a modification using an LED as a backlight will be described with reference to FIG. Here, a commercially available white LED is used as the backlight, and the backlight light is irradiated from the chromium oxide film side of the sample shown in FIG. 6, and the chromium oxide film thicknesses L = 300 mm, 350 mm, 400 mm, and 550 mm. The spectral reflection intensity was measured. The measurement results of the spectral reflection intensity are shown together with the absorption spectrum of a-Si and the emission spectrum of the white LED in FIG. Note that the intensity of each spectrum shown in FIG. 9 is not an absolute value but a relative value for ease of understanding.

Since the white LED used here is obtained by artificially obtaining white light by arranging a phosphor around the blue LED, as shown in FIG. 9, it has a sharp emission peak in the vicinity of a wavelength of 450 nm. And has a broad emission peak in the vicinity of a wavelength of 570 nm. Therefore, the light leakage current of the TFT having the a-Si layer has strong peaks at wavelengths of 480 nm and 530 nm, and therefore the antireflection film made of chromium oxide on the array substrate side has a wavelength of 450 n.
If the spectral bottom wavelength is in the range of 440 nm to 460 nm centering on m, the light leakage current of the TFT having the a-Si layer can be reduced efficiently. Thickness L at which the spectral bottom wavelength of the antireflection film made of chromium oxide is close to 440 nm to 460 nm
From the description of FIG. 7, L is in the range of 350 to 400 mm. Therefore, it can be seen that the thickness L of the antireflection film made of chromium oxide on the array substrate side is preferably 350 to 400 mm. Further, according to the description of FIG. 9, the thickness L of the antireflection film made of chromium oxide is L = 3.
In the case of 50 mm and L = 400 mm, it can be confirmed that the spectral reflectance is lower than that in the case of L = 300 mm and L = 550 mm in the wavelength range of 440 nm to 460 nm including the light from the white LED as the backlight. .

In addition, as the above-described modification, a case where a white LED that obtains pseudo white light as a backlight is used has been described. However, the LED as the backlight is red (R
), Green (G) and B (blue) LEDs in combination with three primary colors, or LEDs of other colors
May also be used in combination. In such a case, the film thickness of the antireflection film may be set so as to suppress the spectral characteristics by an integral value obtained by multiplying the spectral characteristics of each LED by the reflection spectral characteristics of the antireflection film and the photocurrent spectral characteristics of the TFT. .

The example of the transmission type liquid crystal display device has been described above as an embodiment of the present invention. Such a liquid crystal display device of the present invention can be used for electronic devices such as personal computers, mobile phones, and portable information terminals. Of these, an example in which the liquid crystal display device 71 is used in the personal computer 70 is shown in FIG. 9A, and an example in which the liquid crystal display device 76 is also used in the mobile phone 75 is shown in FIG. 9B.
Shown in However, since the basic configuration of the personal computer 70 and the mobile phone 75 is well known to those skilled in the art, a detailed description thereof will be omitted.

It is the model top view for 1 pixel of the array substrate which saw through the color filter substrate of the transmissive liquid crystal display panel of an Example. It is sectional drawing along the II-II line of FIG. It is a dynamic characteristic diagram of a general TFT. FIG. 3 is a circuit diagram of a TFT spectral light leakage current measurement circuit. It is a spectral-light leakage current characteristic view of TFT which has an a-Si layer. It is sectional drawing of the board | substrate for spectral reflectance measurement of a chromium oxide film. It is a figure which shows the relationship between the thickness L of a chromium oxide film | membrane, and spectral reflectance. FIG. 6 is a spectral light leakage current characteristic diagram of a TFT having an a-Si layer in a liquid crystal display device using a cold cathode tube as a backlight. It is the light emission spectrum of white LED as a backlight, the spectral reflection intensity | strength of an antireflection film, and the spectral-light leakage current characteristic figure of TFT which has an a-Si layer. FIG. 10A is a diagram showing a personal computer equipped with the liquid crystal display device of the present invention, and FIG. 10B is a diagram showing a mobile phone equipped with the liquid crystal display device of the present invention. It is a top view for several pixels seen from the color filter substrate side of the conventional liquid crystal display panel. It is a schematic cross section along the XII-XII line of FIG. FIG. 13 is an enlarged view of a portion XIII in FIG. 12 for explaining the principle of reflected light entering the TFT.

Explanation of symbols

10: liquid crystal display panel 11: transparent substrate 12: scanning line 13: auxiliary capacitance line 14: auxiliary capacitance electrode 15: gate insulating film 16: semiconductor (a-Si) layer 17: signal line 18: protective insulating film 19: planarization Film 20: Contact hole 21: Pixel electrode 22: Transparent substrate 23: Black matrix 23a: Chromium oxide film (antireflection film) 23b: Chromium metal film (light shielding film) 23c: Chromium oxide film (antireflection film) 24: Color filter Tier 25
: Common electrode 26: Liquid crystal

Claims (7)

An array substrate on which a thin film transistor having a semiconductor film is formed in each pixel region surrounded by scanning lines and signal lines arranged in a matrix, and a black matrix formed at positions corresponding to the scanning lines, signal lines, and thin film transistors In a liquid crystal display device provided with a color filter substrate provided with a backlight,
The black matrix includes a metal light-shielding film and an antireflection film formed on both surfaces of the metal light-shielding film,
The bottom wavelength of the spectral reflection of the antireflection film on the array substrate side by the light from the backlight overlaps the peak wavelength of the spectral sensitivity of the light leakage current of the semiconductor film. A liquid crystal display device characterized by having a thickness. The liquid crystal display device according to claim 1, wherein the light shielding film is made of chromium metal, and the antireflection film is made of chromium oxide. The bottom wavelength of spectral reflection is 350 nm to 550 n with respect to the thickness of the antireflection film on the array substrate side.
3. The liquid crystal display device according to claim 1, wherein m is set. 4. The liquid crystal display device according to claim 3, wherein the thickness of the antireflection film made of chromium oxide on the array substrate side is 350 to 600 mm. The film thickness of the antireflection film on the side opposite to the array substrate has a bottom wavelength of spectral reflection of 500 nm to 5 nm.
The liquid crystal display device according to claim 1, wherein the liquid crystal display device has a thickness of 50 nm. The thickness of the antireflection film made of chromium oxide on the side opposite to the array substrate is set to 450 mm to 550 mm.
The liquid crystal display device according to claim 5.   An electronic apparatus comprising the liquid crystal display device according to claim 1.

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