JP4735744B2 - Electrophoretic display device - Google Patents

Description

  The present invention relates to an electrophoretic display device.

Conventionally, as an electrophoretic display device, an electrophoretic display device to which an electrophoretic method having a micro partition wall structure is applied is known (for example, see Patent Document 1). For example, as shown in FIG. 7, the electrophoretic display device 100 includes a counter substrate 101 that forms a display surface, and a thin film transistor substrate 102 that is disposed to face the counter substrate 101. A plurality of pixel electrodes 103 arranged in a matrix are electrically connected to an inner surface of the thin film transistor substrate 102 facing the counter substrate 100, surrounding the pixel electrode 103 and electrically connected to the pixel electrode 103 via a thin film transistor (not shown). Signal lines (scanning lines, data lines) 104 are provided. Each signal line 104 is formed with a substantially trapezoidal partition wall 105 in a sectional view standing toward the counter substrate 101, so that the upper region of each pixel electrode 103 is located above the adjacent pixel electrode 103. You will be separated from the area.
On the other hand, on the inner surface of the counter substrate 101 that faces the thin film transistor substrate 102, a counter electrode 106 disposed to face the plurality of pixel electrodes 103 is provided.

  A space formed by the counter substrate 101, the thin film transistor substrate 102, and the partition wall 105 is filled with a solvent 107. A plurality of positively charged black particles 108 and negatively charged white particles 109 are dispersed in the solvent 107.

  When the voltage of the counter electrode 106 is made higher than that of the pixel electrode 103, the white particles 109 move to the counter electrode 106 side and the black particles 108 move to the pixel electrode 103 side, and white is displayed on the display surface. (For example, the state shown in FIG. 7). Conversely, when the voltage of the counter electrode 106 is made smaller than that of the pixel electrode 103, the white particles 109 move to the pixel electrode 103 side and the black particles 108 move to the counter electrode 106 side, and black is displayed on the display surface. It will be. By performing this for each pixel, a predetermined figure or character is drawn on the display surface.

JP 2007-25688 A

Here, when the electrophoretic display device 100 is manufactured, the partition wall 105 is formed after the pixel electrode 103, the signal line 104, and the thin film transistor are formed on the inner surface of the thin film transistor substrate 102. Thereafter, a solvent 107 in which particles 108 and 109 are dispersed is poured into the inner surface of the thin film transistor substrate 102, and the counter substrate 101 on which the counter electrode 106 is formed is overlaid thereon. Due to such a manufacturing process, there is a problem that the particles 108 and 109 remain on the upper surface of the partition wall 103 in the manufacturing process. If the particles 108 and 109 remain on the upper surface of the partition wall 103, particles having a color opposite to the color desired to be displayed (black particles 108 a in FIG. 7) exist between the pixels. It was one of the reasons for the decline.
For this reason, the subject of this invention is providing the electrophoretic display device which suppressed the fall of contrast ratio.

In order to solve the above problems, an electrophoretic display device according to the invention of claim 1 is provided:
A first substrate and a second substrate arranged to face each other at a predetermined interval;
A plurality of pixel electrodes arranged on the first substrate;
A wiring made of a metal film disposed between the adjacent pixel electrodes;
A counter electrode provided on the second substrate;
A partition wall erected so as to surround the plurality of pixel electrodes on the wiring of the first substrate toward the second substrate,
An electrophoretic display device in which a solvent in which a plurality of particles are dispersed is filled in a region surrounded by the partition wall, and an outer surface side of the first substrate is a display surface ,
A light-shielding film is formed on the inner surface of the first substrate corresponding to the partition, and the wiring is formed in a layer between the partition and the light-shielding film, as viewed from the outer surface side of the first substrate. A light-shielding film covers the wiring and is configured so that specular reflection by the wiring does not occur .

The invention described in claim 2 is the electrophoretic display device according to claim 1,
A plurality of thin film transistors provided on the first substrate so as to be individually electrically connected to each of the plurality of pixel electrodes provided in a matrix on the first substrate;
A scanning line as the wiring provided on the first substrate so as to extend in a row direction of the plurality of thin film transistors;
A data line provided on the first substrate so as to extend in the column direction of the plurality of thin film transistors, individually surrounding the pixel electrodes together with the scanning lines, and serving as the wiring connected to the plurality of thin film transistors. ,
The partition wall is erected so as to surround the pixel electrode from above the scan line and the data line toward the second substrate in order to individually isolate a plurality of pixels including the plurality of pixel electrodes.
A light shielding film is formed on the first substrate corresponding to the partition, and the scanning line and the data line are formed between the partition and the light shielding film.

The invention according to claim 3 is the electrophoretic display device according to claim 1 or 2,
The plurality of particles are two types of particles having different surface polarities and colors.

The invention according to claim 4 is the electrophoretic display device according to claim 3,
The two types of particles are black particles and white particles.

The invention according to claim 5 is the electrophoretic display device according to claim 3 or 4,
The solvent is a dispersion medium having a lower dielectric constant than the two kinds of particles.

The invention according to claim 6 is the electrophoretic display device according to any one of claims 3 to 5,
The two types of particles are characterized in that a voltage is applied between the pixel electrode and the counter electrode and migrate between the pair of substrates by an electric field formed.

The invention according to claim 7 is the electrophoretic display device according to any one of claims 1 to 6,
The light shielding film is formed of either chromium oxide or a photosensitive resin.

The invention according to claim 8 is the electrophoretic display device according to any one of claims 1 to 7,
The first substrate is a thin film transistor substrate.

  ADVANTAGE OF THE INVENTION According to this invention, the electrophoretic display device which suppressed the fall of contrast ratio can be provided.

It is sectional drawing which showed typically the principal part structure of the electrophoretic display device of this embodiment. It is sectional drawing which shows the principal part structure of the thin-film transistor substrate with which the electrophoretic display device of FIG. 1 is equipped, and is sectional drawing seen from the II-II cutting line in FIG. FIG. 2 is a transmission plan view illustrating a configuration of a main part of a thin film transistor substrate provided in the electrophoretic display device of FIG. 1. FIG. 7 is an explanatory diagram showing a manufacturing process of the electrophoretic display device of FIG. 1. FIG. 7 is an explanatory diagram showing a manufacturing process of the electrophoretic display device of FIG. 1. It is a disassembled perspective view showing schematic structure of the film for partition for forming the partition with which the electrophoretic display device of FIG. 1 is equipped. It is sectional drawing which showed typically the principal part structure of the conventional electrophoretic display device.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, although various technically preferable limitations for implementing the present invention are given to the embodiments described below, the scope of the invention is not limited to the following embodiments and illustrated examples.

  FIG. 1 is a cross-sectional view schematically showing a main configuration of the electrophoretic display device of the present embodiment. As shown in FIG. 1, the electrophoretic display device 1 is provided with a counter substrate 10 and a thin film transistor substrate 20 disposed to face the counter substrate 10 by a partition wall 60 at a predetermined interval. The counter substrate 10 is a second substrate, and the thin film transistor substrate 20 is a first substrate. Pixel electrodes 24 are formed in a matrix on the thin film transistor substrate 20, and scanning lines 22 and data lines 23 as wirings are formed between the pixel electrodes. A partition wall 60 is formed in a grid pattern on the scanning lines 22 and the data lines 23, and an antireflection film 80 is formed between the scanning lines 22 and the data lines 23 and the thin film transistor substrate 20. A frame-shaped sealing material (not shown) is formed between the counter substrate 10 and the thin film transistor substrate 20, and a space is formed between the pair of substrates using the partition wall 60 as a spacer. A solvent 70 in which particles 72 are dispersed is enclosed.

  The counter substrate 10 is made of, for example, glass. A counter electrode 11 is laminated on the inner surface of the counter substrate 10 facing the thin film transistor substrate 20. The counter electrode 11 is made of, for example, ITO (Indium Tin Oxide).

In the solvent 70, a plurality of two types of particles having different surface polarities and colors are dispersed. Of the two types of particles, one type is a positively charged black particle 71 made of, for example, carbon, and the other type is a negatively charged white particle 72 made of, for example, TiO ₂ (titanium oxide). Here, the diameter of the black particles 71 is 5.0 μm or less, and the diameter of the white particles 72 is 0.3 μm or less. As the solvent 70, a dispersion medium having a dielectric constant lower than that of the black particles 71 and the white particles 72 is used.

  Next, the thin film transistor substrate 20 will be described in detail with reference to FIGS. FIG. 3 is a transmission plan view showing the main configuration of the thin film transistor substrate 20. 2 is a cross-sectional view taken along the line II-II in FIG.

  First, a planar structure of the thin film transistor substrate 20 will be described with reference to FIG. The thin film transistor substrate 20 is made of glass or the like, and a plurality of scanning lines 22 and a plurality of data lines 23 are formed on the upper surface so as to intersect each other. In this case, the plurality of scanning lines 22 are provided extending in the row direction, and the plurality of data lines 23 are provided extending in the column direction.

  On each thin film transistor substrate 20, a substantially rectangular pixel electrode 24 with a part cut away is provided in each region surrounded by the scanning line 22 and the data line 23. Thereby, the plurality of pixel electrodes 24 are arranged in a matrix on the thin film transistor substrate 20. A thin film transistor 25 as a switching element is disposed in the notch 241 of each pixel electrode 24. The pixel electrode 24 is electrically connected to the scanning line 22 and the data line 23 through the thin film transistor 25.

  A partition wall 60 is formed on the scanning line 22 and the data line 23 so as to stand toward the counter substrate 10. By the partition wall 60, a plurality of pixels including the pixel electrode 24 are individually separated.

  A plurality of auxiliary capacitance lines 26 are provided on the thin film transistor substrate 20. The auxiliary capacitance line 26 is formed so as to overlap three sides excluding the lower side of the pixel electrode 24 in the drawing.

Next, a cross-sectional structure of the thin film transistor substrate 20 will be described.
As shown in FIG. 2, an antireflection film 80 made of CrO ₂ (chromium oxide) is formed on the inner surface of the thin film transistor substrate 20 facing the counter substrate 10 so as to face the scanning line 22 and the data line 23. ing. The antireflection film 80 is formed wider than the region where the scanning lines 22 and the data lines 23 are formed. The antireflection film 80 may be formed of a photosensitive resin such as photosensitive black polyimide other than CrO ₂ .

On the inner surface side of the thin film transistor substrate 20, a gate electrode 29 made of Cr (chromium) or the like and a scanning line 22 connected to the gate electrode 29 are formed at predetermined positions. The gate electrode 29 and the scanning line 22 are formed on the antireflection film 80. The gate electrode 29 is disposed at a location forming the thin film transistor 25. In addition, a gate wiring 29a made of Cr or the like and an auxiliary capacitance line 26 made of ITO (indium tin oxide) or the like covering the gate wiring 29a are formed at other predetermined locations on the inner surface side of the thin film transistor substrate 20. . The gate wiring 29a is formed on the antireflection film 80, and the auxiliary capacitance line 26 is formed so as to cover both the gate wiring 29a and the antireflection film 80.
In addition, a gate insulating film 30 made of, for example, silicon oxide or silicon nitride is formed on the thin film transistor substrate 20 so as to cover the gate electrode 29, the scanning line 22, and the auxiliary capacitance line 26. As a result, the gate electrode 29 is disposed on the lower layer side of the gate insulating film 30.

  A semiconductor thin film 31 made of a semiconductor such as intrinsic amorphous silicon is formed above the gate electrode 29 on the upper surface of the gate insulating film 30. A channel protective film 32 made of silicon nitride or the like is provided at substantially the center of the upper surface of the semiconductor thin film 31. Ohmic contact layers 33 and 34 made of n-type amorphous silicon or the like are provided on both sides of the upper surface of the channel protective film 32 and on the upper surface of the semiconductor thin film 31 on both sides thereof.

  On the upper surfaces of the ohmic contact layers 33 and 34, a source electrode 35 and a drain electrode 36 made of, for example, Cr are provided. As a result, the source electrode 35 and the drain electrode 36 are disposed on the upper layer side of the gate insulating film 30. Here, the thin film transistor 25 is an inverted stagger type, and includes a gate electrode 29, a gate insulating film 30, a semiconductor thin film 31, a channel protective film 32, ohmic contact layers 33 and 34, a source electrode 35 and a drain electrode 36. .

  A semiconductor thin film 37 made of a semiconductor such as intrinsic amorphous silicon is also formed in the formation region of the data line 23 on the upper surface of the gate insulating film 30. An ohmic contact layer 38 made of n-type amorphous silicon or the like is provided on the upper surface of the semiconductor thin film 37. A drain film 39 made of chromium or the like is formed on the upper surface of the ohmic contact layer 38. This drain film 39 forms the data line 23.

  An overcoat film 50 as an interlayer insulating film made of silicon oxide or the like is formed on the thin film transistor 25 and the data line 23 so as to cover the thin film transistor 25 and the data line 23. A contact hole 40 is formed on the upper surface of the source electrode 35 in the overcoat film 50. Specifically, the contact hole 40 is formed on the upper surface of a portion of the source electrode 35 that is separated from the channel protective film 32.

  As shown in FIGS. 2 and 3, a transparent pixel electrode 24 made of ITO or the like is provided at a predetermined position on the upper surface of the overcoat film 50 through the contact hole 40, the source electrode 35, the auxiliary capacitance line 26, and the like. Are electrically connected.

  In the thin film transistor substrate 20, a partition wall 60 standing from the scanning line 22 and the data line 23 toward the counter substrate 10 is formed of a photosensitive resin such as photosensitive acrylic. The partition wall 60 is formed in a substantially trapezoidal shape when viewed in cross section, and is formed wider than the width of the lines 22 and 23 so that the base 60a covers the scanning line 22 and the data line 23.

Next, a manufacturing method of the electrophoretic display device 1 will be described with reference to FIGS.
First, as shown in FIG. 4A, a chromium oxide film is formed at a predetermined position on the inner surface of the thin film transistor substrate 20 to form an antireflection film 80.
Then, as shown in FIG. 4B, Cr is deposited at a predetermined location of the antireflection film 80 to form the gate electrode 29, the scanning line 22, and the gate wiring 29a.

Thereafter, as shown in FIG. 4C, an ITO film is formed so as to cover the gate wiring 29a, and the auxiliary capacitance line 26 is formed.
Next, as shown in FIG. 4D, for example, silicon oxide or silicon nitride is formed to cover the gate electrode 29, the scanning line 22, and the auxiliary capacitance line 26, thereby forming the gate insulating film 30. After the gate insulating film 30 is formed, an intrinsic amorphous silicon 31a is formed on the upper surface thereof. Further, after the formation of the intrinsic amorphous silicon 31a, a channel protective film 32 is formed by depositing silicon nitride or the like at a predetermined position on the upper surface thereof.

  Further, as shown in FIG. 5A, unnecessary portions of the intrinsic amorphous silicon 31a are removed by using a well-known etching method or the like, and semiconductor thin films 31 and 37 are formed. After the removal, n-type amorphous silicon or the like is formed at a predetermined location to form ohmic contact layers 33, 34, and 38, and Cr is formed on the ohmic contact layers 33, 34, and 38 to form a source. An electrode 35, a drain electrode 36, and a drain film 39 are formed. Thereby, the thin film transistor 25 and the data line 23 are formed.

As shown in FIG. 5B, an overcoat film 50 is formed by depositing silicon oxide or the like on the upper layer side of the thin film transistor 25 and the data line 23. Thereafter, a predetermined portion of the overcoat film 50 is removed by a known etching method to form a contact hole 40.
Then, as shown in FIG. 5C, ITO is formed at a predetermined location on the upper surface of the overcoat film 50 to form the pixel electrode 24.

When the thin film transistor substrate 20 is completed, a partition wall 60 is formed on the thin film transistor substrate 20. Specifically, the partition wall 60 is formed using the partition wall film 61 shown in FIG. Although FIG. 6 shows a state where each layer is peeled off, the partition film 61 is actually formed by laminating a support film 62, a resist film 63, and a cover film 64. For example, the support film 62 is formed from a resin film such as PET, and the cover film 64 is formed from a resin film such as OPP. The resist film 63 is formed of a photosensitive resin such as photosensitive acrylic forming the partition wall 60. A support film 62 is attached to one surface, and a cover film 64 is attached to the other surface.
In order to form the partition wall 60 using the partition wall film 61, first, the cover film 64 is peeled off, and the resist film 63 is bonded onto the thin film transistor substrate 20. The resist film 63 is exposed in this state, and the photosensitive acrylic is transferred to a predetermined position on the thin film transistor substrate 20. After the transfer, the support film 62 is peeled off, and then the resist film 63 is developed to remove portions other than those transferred to the thin film transistor substrate 20. Then, the photosensitive acrylic transferred onto the thin film transistor substrate 20 is post-baked to improve the adhesion, thereby forming the partition wall 60 as shown in FIG.

  After the partition wall 60 is formed, a solvent 70 in which a plurality of black particles 71 and white particles 72 are dispersed is injected into a plurality of regions surrounded by the partition wall 60. After the implantation, the counter substrate 10 is arranged on the thin film transistor substrate 20 so that the counter electrode 11 and the pixel electrode 24 face each other, and bonded and sealed by a frame-shaped sealing material (not shown) formed between the opposing substrates 10 and 20. To do. Alternatively, an adhesive layer may be formed in advance on the entire surface of the counter substrate 10 using a resin film or the like, and then bonded and sealed (see FIG. 1).

Next, the operation of the electrophoretic display device 1 of the present embodiment will be described. In the electrophoretic display device 1, the display surface is the outer surface 20a of the thin film transistor substrate 20, and the viewing direction is the arrow direction in FIG.
When the voltage of the counter electrode 11 is made higher than that of the pixel electrode 24, white particles 72 made of negatively chargeable titanium oxide move to the counter electrode 11 side and black particles made of positively chargeable carbon black. 71 moves to the pixel electrode 24 side, and black is displayed on the display surface (for example, the state shown in FIG. 1). Conversely, when the voltage of the counter electrode 11 is made smaller than that of the pixel electrode 24, the white particles 72 move to the pixel electrode 24 side and the black particles 71 move to the counter electrode 11 side, and white is displayed on the display surface. It will be. By performing this for each pixel arranged on the matrix, a predetermined figure or character is drawn on the display surface.

By the way, as shown in FIG. 1, after manufacturing, black particles 71 and white particles 72 remain between the partition wall 60 and the counter substrate 10 and are sandwiched between the counter substrates 10. When the counter substrate 10 side is used as a display surface, the contrast ratio is lowered because particles of the color opposite to the color to be displayed (white particles 72 in FIG. 1) are present between the pixels. In FIG. 1, since the outer surface 20a of the thin film transistor substrate 20 is a display surface, even if particles having a color opposite to the color to be displayed (white particles 72 in FIG. 1) are present between the pixels, the particles are displayed on the display surface. Can be prevented and a reduction in contrast ratio can be prevented.
Further, when the outer surface 20a of the thin film transistor substrate 20 is used as a display surface, the scanning line 22 and the data line 23 are formed of a metal film, so that mirror reflection occurs and the reflection becomes intense. For this reason, in the electrophoretic display device 1 of the present embodiment, the antireflection film 80 is interposed between the scan line 22 and the data line 23 and the thin film transistor substrate 20 so as to overlap the scan line 22 and the data line 23. Therefore, even when viewed from the display surface side, the above-described reflection can be prevented and display quality can be prevented from deteriorating.

As described above, according to the present embodiment, it is possible to provide the electrophoretic display device 1 that can prevent a reduction in contrast ratio while suppressing reflection.
In addition, since the antireflection film 80 is formed wider than the area where the scanning lines 22 and the data lines 23 are formed, even if the scanning lines 22 and the data lines 23 are misaligned, the antireflection film is surely formed. 80 can cover the display surface side.
Note that the present invention is not limited to the above embodiment, and can be modified as appropriate.

1 Electrophoretic display device 10 Counter substrate (second substrate)
11 Counter electrode 20 Thin film transistor substrate (first substrate)
20a External surface (display surface)
22 scanning line 23 data line 24 pixel electrode 25 thin film transistor 26 auxiliary capacitance line 29 gate electrode 29a gate wiring 30 gate insulating film 31 semiconductor thin film 31a intrinsic amorphous silicon 32 channel protective film 33, 34 ohmic contact layer 35 source electrode 36 drain electrode 37 semiconductor Thin film 38 Ohmic contact layer 39 Drain film 40 Contact hole 50 Overcoat film 60 Partition 60a Bottom 61 Partition film 62 Support film 63 Resist film 64 Cover film 70 Solvent 71 Black particle 72 White particle 80 Antireflection film 241 Notch

Claims (8)

A first substrate and a second substrate arranged to face each other at a predetermined interval;
A plurality of pixel electrodes arranged on the first substrate;
A wiring made of a metal film disposed between the adjacent pixel electrodes;
A counter electrode provided on the second substrate;
A partition wall erected so as to surround the plurality of pixel electrodes on the wiring of the first substrate toward the second substrate,
An electrophoretic display device in which a solvent in which a plurality of particles are dispersed is filled in a region surrounded by the partition wall, and an outer surface side of the first substrate is a display surface ,
A light-shielding film is formed on the inner surface of the first substrate corresponding to the partition, and the wiring is formed in a layer between the partition and the light-shielding film, as viewed from the outer surface side of the first substrate. An electrophoretic display device , wherein a light shielding film covers the wiring, and is configured so that specular reflection by the wiring does not occur . A plurality of thin film transistors provided on the first substrate so as to be individually electrically connected to each of the plurality of pixel electrodes provided in a matrix on the first substrate;
A scanning line as the wiring provided on the first substrate so as to extend in a row direction of the plurality of thin film transistors;
A data line provided on the first substrate so as to extend in the column direction of the plurality of thin film transistors, individually surrounding the pixel electrodes together with the scanning lines, and serving as the wiring connected to the plurality of thin film transistors. ,
The partition wall is erected so as to surround the pixel electrode from above the scan line and the data line toward the second substrate in order to individually isolate a plurality of pixels including the plurality of pixel electrodes.
The light-shielding film is formed on the first substrate corresponding to the partition, and the scanning line and the data line are formed between the partition and the light-shielding film. The electrophoretic display device described.   The electrophoretic display device according to claim 1, wherein the plurality of particles are two types of particles having different surface polarities and colors.   The electrophoretic display device according to claim 3, wherein the two kinds of particles are black particles and white particles.   The electrophoretic display device according to claim 3, wherein the solvent is a dispersion medium having a lower dielectric constant than the two kinds of particles.   6. The two kinds of particles according to claim 3, wherein a voltage is applied between the pixel electrode and the counter electrode, and the two kinds of particles migrate between the pair of substrates by a formed electric field. The electrophoretic display device according to one item. The electrophoretic display device according to claim 1, wherein the light shielding film is formed of one of chromium oxide and a photosensitive resin.   The electrophoretic display device according to claim 1, wherein the first substrate is a thin film transistor substrate.

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