JPH05173111A - Liquid crystal display device and its manufacture - Google Patents

Abstract

PURPOSE:To provide patterning constitution and a patterning method for effectively preventing a light leak in non-picture-element parts of the matrix type liquid crystal display device. CONSTITUTION:The matrix type liquid crystal display device is equipped with a lower transparent substrate 1 which has plural column electrodes arrayed at specific intervals, an upper transparent substrate 2 which has plural row electrodes 6 provided-crossing the column electrodes 5, and a liquid crystal layer 3 sandwiched between both the substrates. Then DELTAnd (DELTAn: amount of double refraction, d: thickness of liquid crystal device) is so set that the light transmissivity of the liquid crystal layer 3 positioned except at the intersection parts of the column electrodes 5 and row electrodes 6, i.e., at the non-picture- element parts is substantially zero. Namely, a photosensitive resin layer 7 for optimizing DELTAnd is arranged between the adjacent column electrodes 5 on the same substrate, e.g. lower transparent substrate 1. This photosensitive resin layer 7 is formed through a process wherein a positive resist film left after the column electrodes 5 are patterned on the transparent substrate 1 is coated with photosensitive resin from above and a process wherein the photosensitive resin is exposed from behind the transparent substrate 1 and developed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matrix type liquid crystal display device having pixels arranged in rows and columns and a manufacturing method thereof. More specifically, the present invention relates to a structure for preventing light leakage in a non-pixel portion left between adjacent pixels and a method for forming the structure.

[0002]

2. Description of the Related Art Generally, due to the structure of a panel which constitutes a matrix type liquid crystal display device, it is difficult to complete the light shielding performance in a non-pixel portion, and some light leakage occurs. If no measures are taken, the contrast of the entire display screen deteriorates due to light leakage.

Conventionally, a so-called black matrix mask has been formed between adjacent pixels in order to prevent a decrease in contrast. As a mask material, a metal thin film of chromium or the like, a resin film in which a black pigment or the like is dispersed, and the like have been conventionally used. In the case of a metal thin film, first, a metal material is deposited on the entire substrate by vacuum vapor deposition or sputtering, and then the metal thin film is removed except for the non-pixel portion using photolithography and etching to form a black matrix mask. It was On the other hand, in the case of an organic film in which a pigment is dispersed, a resin material having photosensitivity is used for itself. This resin material is uniformly applied over the entire surface of the substrate, and then directly exposed and developed to obtain a patterned black matrix mask. In addition to this, as a method of forming a black matrix mask, a technique of offset printing black ink is also known, and is disclosed in, for example, Japanese Patent Laid-Open No. Sho 63-63.
-180933 gazette.

[0004]

When forming a black matrix mask using a metal material such as chromium, a film deposition process using vacuum deposition or sputtering, a patterning and etching process using photoresist,
There is a problem that many additional steps such as a step of overcoating a metal film with an insulating layer are required, resulting in an increase in manufacturing cost. Further, even if the insulating layer is overcoated, a short circuit failure between the transparent electrode and the metal mask formed thereon cannot be completely prevented. While the metal mask has excellent light-shielding performance, it also has conductivity, so it is necessary to always take precautions against short circuits, and it is difficult to handle.

On the other hand, when a photosensitive resin material in which a pigment is dispersed is used, its film thickness is larger than that of a metal thin film by 1 μm.
It will be an order of magnitude. When a black matrix mask having such a thickness is formed, there is a problem that remarkable unevenness or steps are generated on the substrate surface and the alignment of liquid crystal molecules is disturbed. As a countermeasure against this, it has been proposed to cover the black matrix mask with an overcoat layer for planarization. However, a thermosetting resin is generally used for this overcoat layer, and sufficient hardness cannot be obtained. Therefore, when a panel is constructed by bonding a pair of substrates, it is difficult to control the gap size uniformly and uniformly.

Further, the method of offset printing the black ink has a problem that a margin is required to absorb the alignment error and the aperture ratio of the pixel is sacrificed.

In view of the above-mentioned problems or problems of the prior art, the present invention does not use a black matrix mask made of a photosensitive resin material in which a metal material or a pigment is dispersed, or black ink, without using a black matrix mask. It is an object of the present invention to provide a structure and a method for forming the structure capable of substantially completely preventing the above.

[0008]

Means for solving the problems of the above-mentioned conventional techniques and achieving the objects of the present invention are as follows. The simple matrix type liquid crystal display device includes a plurality of first pixels arranged at a predetermined interval.
One substrate having a transparent electrode, another substrate having a second transparent electrode provided so as to intersect with the transparent electrode, and a liquid crystal layer sandwiched between both substrates. .. As a means for increasing the display contrast of this device, Δnd is set so that the light transmittance of the liquid crystal layer positioned other than the intersection (that is, the pixel portion) between the first and second transparent electrodes becomes substantially zero. (Where Δn is the birefringence amount of the liquid crystal, and d is the thickness of the liquid crystal layer). Specifically, it is characterized in that a photosensitive resin layer for setting an optimum Δnd is arranged between adjacent transparent electrodes on the same substrate.

In order to form such a photosensitive resin layer, first, a transparent electrode is patterned on a transparent substrate, and then the photosensitive resin is applied in a desired thickness in an overlapping manner on the remaining positive type resist film. Next, the applied photosensitive resin is exposed from the back surface of the transparent substrate and developed to leave a photosensitive resin layer having a desired thickness only between the transparent electrodes.

The present invention can be applied to an active matrix type liquid crystal display device in addition to the above-mentioned simple matrix type liquid crystal display device. This type of liquid crystal display device has one substrate having pixel electrodes arranged in a matrix and switching elements connected to the pixel electrodes, and another substrate having a counter electrode and arranged to face the one substrate. It consists of a substrate and a liquid crystal layer sandwiched between both substrates. In this device, Δnd may be set so that the transmittance of the liquid crystal layer located in the non-pixel portion between the pixel electrodes is substantially zero.

[0011]

The transmittance of the liquid crystal layer located in the non-pixel portion largely depends on the value of Δnd. Since the birefringence amount Δn is constant and uniform, the transmittance can be made substantially zero by adjusting the thickness d of the liquid crystal layer. Therefore, a photosensitive resin layer having a desired thickness is selectively arranged in the space between adjacent electrodes on the same substrate. That is, the thickness of the photosensitive resin layer may be set so that the gap between the surface of the counter electrode that defines the thickness of the liquid crystal layer in the non-pixel portion and the surface of the photosensitive resin layer has exactly 0 transmittance. By substantially completely preventing the light leakage of the non-pixel portion forming the background portion, the contrast of the entire display screen can be increased.

In order to selectively form such a photosensitive resin layer in the non-pixel portion, the positive resist film used for patterning the transparent electrode is used as it is as a mask. That is, the positive type resist film is not removed after the etching of the transparent electrode, and the photosensitive resin is applied thereon in a desired thickness in an overlapping manner. When the applied photosensitive resin is exposed from the back surface of the transparent substrate, only the exposed photosensitive resin in the non-pixel portion which is not shielded by the positive resist film is cured. By performing the development process, the photosensitive resin layer is formed only in the non-pixel portion. In this way, the number of steps is reduced as compared with the conventional black matrix mask forming step.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example in which the present invention is applied to a super twist nematic type simple matrix type liquid crystal display device. As shown in the figure, this device is composed of a lower transparent substrate 1, an upper transparent substrate 2, and a liquid crystal layer 3 sandwiched between both substrates. The pair of substrates 1 and 2 are attached to each other by a seal 4.

On the inner surface of the lower transparent substrate 1, a plurality of transparent column electrodes 5 arranged at a predetermined interval are formed. On the inner surface of the upper transparent substrate 2, transparent row electrodes 6 are formed so as to intersect the column electrodes 5. A pixel is defined at the intersection of the column electrode 5 and the row electrode 6.
By applying a drive voltage between the column electrode 5 and the row electrode 6, the transmittance of the liquid crystal layer 3 changes. The thickness d0 of the liquid crystal layer 3 in the pixel portion is preset so that the ratio of the transmittance when the pixel is selected and the transmittance when the pixel is not selected is maximized.

On the other hand, the intersection of the row electrodes 6 facing the space between the adjacent column electrodes 5 becomes a non-pixel portion. The gap size between them is d1. This is column electrode 5 from d0
The thickness is subtracted from the value and is automatically determined. This thickness d1 does not necessarily make the transmittance of the liquid crystal layer 3 zero. Actually, the photosensitive resin layer 7 is embedded between the adjacent column electrodes 5. The photosensitive resin layer 7 has an optimum thickness, and the distance d3 between the surface of the photosensitive resin layer 7 and the surface of the row electrode 6 is set so that the transmittance of the liquid crystal layer 3 located in the non-pixel portion is zero. There is. Although not shown, a photosensitive resin layer is also formed in the space between the adjacent row electrodes 6.

The inner surfaces of the lower transparent substrate 1 and the upper transparent substrate 2 are subjected to rubbing treatment, and in this example, the liquid crystal layer 3 is so-called super twist nematic alignment. Polarizing plates 8 and 9 are attached to the outer surfaces of both substrates in order to extract electro-optical changes of the liquid crystal layer 3 as changes in transmittance. Further, a pair of retardation plates 10 and 11 are interposed to prevent coloration of the display screen. Each retardation film is made of a birefringent plastic film made of, for example, polycarbonate or the like, and has a Δnd of 400 nm for an incident wavelength of 545 nm.

FIG. 2 is a schematic diagram showing an optical configuration of a super twist nematic type liquid crystal display device. The direction of the rubbing treatment applied to the inner surface of the lower transparent substrate 1, that is, the lower rubbing axis and the direction of the rubbing treatment applied to the inner surface of the upper transparent substrate 2, that is, the upper rubbing axis, are twisted by 240 degrees. The transmission axis of the lower polarizing plate 8 and the transmission axis of the upper polarizing plate 9 are orthogonal to each other. Further, the stretching axis of the lower retardation plate 10 and the stretching axis of the upper retardation plate 11 are inclined by 56 degrees with respect to each other.

FIG. 3 is a graph showing the relationship between the transmittance and Δnd of the liquid crystal display device having the optical configuration shown in FIG. It can be seen that the transmittance of the liquid crystal panel greatly depends on Δnd. If the thickness of the liquid crystal layer is set so that Δnd becomes 790 nm, the transmittance can be zero. That is, the maximum display contrast can be obtained by setting Δnd of the liquid crystal layer in the non-pixel portion to 790 nm.

On the other hand, FIG. 4 is a graph showing the operating characteristics of the liquid crystal in the pixel portion. When the selection voltage VS is applied to the liquid crystal, the transmissivity of the pixel is increased and the pixel is turned on. On the contrary, when the non-selection voltage VNS is applied, the transmittance of the liquid crystal is 0.
The adjacent pixels are kept in the off state. In general, the setting of Δnd is set so that the ratio of the transmittance between the lit state and the extinguished state is maximized. For example, in the example shown in FIG. 1, the maximum contrast ratio is obtained when Δnd0 in the pixel portion is 840 nm. Since Δn is automatically determined when the liquid crystal material is selected, d0 may be set so that Δnd0 becomes 840 nm.

FIG. 5 is a schematic plan view showing the pixel configuration of the embodiment shown in FIG. The pixels 12 are defined in the overlapping portions of the matrix electrodes of the upper and lower transparent substrates. A non-pixel portion around which at least one electrode does not exist is left. This non-pixel portion includes a portion Gap1 where only one electrode does not exist and a portion Gap2 where both electrodes do not exist. As described above, Δnd0 of the pixel 12 portion is set to, for example, 840 nm in order to obtain the optimum contrast ratio. At this time, for example, if Δn has a value of 0.153 and the film thickness of the electrode is 0.2 μm, Δn of Gap1 is Δn.
If there is no photosensitive resin layer, d is increased by subtracting the film thickness of one electrode, so Δnd1 is 870 nm.
become. Similarly, Δnd of Gap2 increases by subtracting the film thickness of the two electrodes, and becomes Δnd2 = 900 nm. As is clear from the graph of FIG. 3, 870 nm and 9
Since the value of 00 nm is larger than the value of 790 nm corresponding to the transmittance of 0, the transmittance of Gap1 and Gap2 will be about 5% if no measures are taken. This Gap
When the transmittance of the 1 and Gap2 portions approaches 0%, the contrast of the entire display screen is obviously improved. Therefore,
In the present invention, the photosensitive resin layer is used to bring Δnd in the non-pixel portion close to 790 nm. However, it is structurally difficult to set Δnd to 790 nm for both Gap1 and Gap2. Therefore, Δ of the portion of Gap1 that occupies a large area in the effective display screen
nd is adjusted to 790 nm. For example, in the example shown in FIG. 5, when the pixel 12 has the illustrated size, Ga
The area of p1 is 16.5 times the area of Gap2.

It is understood that in order to adjust the Δnd of the Gap1 portion to 790 nm, it is sufficient to form a photosensitive resin layer of about 0.5 μm between the adjacent transparent electrodes. For example, in the example shown in FIG. 1, Δnd1 when the photosensitive resin layer 7 is not formed
In comparison with the above, Δnd3 when the photosensitive resin layer 7 is formed becomes smaller, and the transmittance in the non-pixel portion can be substantially zero. Since the transmittance in the non-pixel portion is determined by Δnd, the photosensitive resin layer 7 to be formed does not necessarily have to be colored in black or the like, and a transparent one can be used. However, a material having birefringence cannot be used. If there is birefringence, Δnd of the material itself adversely affects the transmission characteristics of the liquid crystal panel.

Next, a method of forming the photosensitive resin layer will be described with reference to FIGS. FIG. 6 shows a flow chart of the forming process, and FIGS. 7 to 10 show sectional shapes of semi-finished products in each process. First, prior to the formation of the photosensitive resin layer, the transparent electrode is patterned in step S1. That is, after depositing a transparent electrode material such as ITO on the entire surface of the substrate, a positive resist is applied. As this positive resist, for example, a novolak resin which is a prepolymer of a phenol resin and a quinonediazide compound added as a photosensitizer is used. This positive resist is exposed and developed and patterned, and then the transparent electrode is etched to form a desired row electrode or column electrode.

Next, in step S2, the transparent substrate 240
The positive resist is baked by heat treatment at about 1 hour. This state is shown in FIG. The positive resist 101 turns reddish brown due to carbonization of a phenol resin, a photosensitizer, a dye, or the like. As is apparent from the figure, the positive resist 101 is left in a state of covering the transparent electrode 103 formed on the glass substrate 102, and the space between the adjacent transparent electrodes 103 is exposed.

In step S3, a negative transparent photosensitive resin whose main component is polyimide, epoxy, acrylic or the like is spin-coated or printed on the entire surface of the substrate after the positive resist is baked. Then, in step S4, prebaking is performed.

Next, in step S5, an exposure process is performed from the back surface using the positive resist that has turned reddish brown as a mask, and only the resin existing between the adjacent transparent electrodes is irradiated with ultraviolet rays. This state is shown in FIG. The portion of the photosensitive resin 104 that is superposed on the surface of the positive resist 101 is not exposed because the shadow is just formed when the backside exposure is performed.

Subsequently, in step S6, the photosensitive resin is developed. For example, the uncured portion of the photosensitive resin is dissolved and removed using an alkaline solution having a concentration of about 1%. 1
%, The rate of dissolution of the photosensitive resin is much faster than the rate of dissolution of the positive resist after baking, and the positive resist does not dissolve at the same time as the photosensitive resin. The state after the development processing is shown in FIG. It can be seen that the photosensitive resin 104 is left only between the adjacent electrodes.

Next, in step S7, the photosensitive resin patterned along the space between the adjacent electrodes is post-baked to be completely cured.

Finally, in step S8, the positive resist is stripped using an alkaline solution having a concentration of about 15%.
The state after peeling is shown in FIG. The heat resistance of the positive resist is actually about 150 ° C. In contrast, 24
When baking is performed at a temperature of about 0 ° C., the adhesiveness with the transparent electrode is deteriorated and peeling easily occurs. On the other hand, since the photosensitive resin after post-baking is completely polymerized or cured, it has sufficient alkali resistance and is not peeled from the substrate 102 and is patterned along the adjacent transparent electrodes. A layer 105 is obtained.

As described above, the photosensitive resin layer can be formed between the adjacent electrodes by directly using the positive resist used in the transparent electrode patterning step as a mask. When the appropriate thickness of the photosensitive resin layer is determined based on the relationship between Δnd and the transmittance when designing the panel, and the liquid crystal panel is actually created, the transmittance of the non-pixel portion approaches 0% and the display contrast looks black. Can be improved.
When the transmittance of the actually prepared sample was measured, it was 0.2% in the pixel portion, 0.2% in the Gap1 portion, and 1% in the Gap2 portion in the completely extinguished state. It was 0.20% when the weighted average was calculated according to the area of each part. On the other hand, for comparison, when the transmittance of a sample in which the photosensitive resin layer is not formed is measured, the pixel portion is 0.2%,
The Gap1 portion was 4% and the Gap2 portion was 5%. The weighted average is 0.63%. In this way, by adjusting Δnd using the photosensitive resin layer, the transmittance of the entire screen can be reduced to about 1/3 in the all-off state, and the contrast of the liquid crystal panel can be improved.

In the above-described embodiments, the structure in which the present invention is applied to the simple matrix type liquid crystal display device has been described.
However, the present invention is not limited to this,
For example, it can be applied to an active matrix type liquid crystal display device. An example of this is shown in FIG. Pixel electrodes 201 arranged in a matrix on the transparent insulating substrate,
A switching element 202 connected to this pixel electrode is formed. This switching element 202 is composed of an insulated gate field effect thin film transistor, and its source region S is connected to a signal line 203 arranged in a line. In addition, the gate electrodes G are the scanning lines 2 arranged in rows.
It is formed integrally with 04. Further, the drain region D is connected to the corresponding pixel electrode 201. The non-pixel portion is entirely covered with the photosensitive resin layer 205 according to the present invention, except for the hatched area of the pixel electrode 201. With such a structure, it is possible to effectively prevent light leakage other than in the pixel portion. Although not shown, another substrate having a counter electrode formed thereon is arranged so as to face it apart from the substrate having the pixel electrode and the switching element formed thereon. A liquid crystal layer is sandwiched between both substrates.

[0031]

By patterning the photosensitive resin along the non-pixel portion of the matrix-type liquid crystal display device, that is, between the adjacent transparent electrodes, the Δnd of the liquid crystal layer in the non-pixel portion is formed.
Was adjusted to reduce the transmittance. As a result, the contrast of the liquid crystal display device can be improved. Further, in order to form the photosensitive resin layer between the adjacent transparent electrodes, there is an effect that the manufacturing process can be rationalized by using the positive resist mask used in the preceding transparent electrode patterning process.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a basic configuration of a liquid crystal display device according to the present invention.

FIG. 2 is a schematic diagram showing an optical configuration of the super twist nematic liquid crystal display device shown in FIG.

FIG. 3 is a graph showing the relationship between the transmittance and Δnd of the liquid crystal display device.

FIG. 4 is a graph showing the relationship between drive voltage and transmittance of a liquid crystal display device.

5 is a schematic diagram showing an electrode array of the simple matrix type liquid crystal display device shown in FIG.

FIG. 6 is a flowchart showing a method for manufacturing a liquid crystal display device according to the present invention.

FIG. 7 is a cross-sectional view showing a semi-finished product processed by the manufacturing method according to the present invention.

FIG. 8 is a cross-sectional view showing a semi-finished product at another stage of the same.

FIG. 9 is a cross-sectional view showing a semi-finished product of still another stage.

FIG. 10 is a sectional view showing a final finished product.

FIG. 11 is a schematic view showing an embodiment in which the present invention is applied to an active matrix type liquid crystal display device.

[Explanation of symbols]

 1 Lower transparent substrate 2 Upper transparent substrate 3 Liquid crystal layer 5 Column electrodes 6 Row electrodes 7 Photosensitive resin layer

Claims (4)

[Claims] 1. A substrate having a plurality of first transparent electrodes arranged at a predetermined interval, and another substrate having a second transparent electrode provided so as to intersect with the transparent electrodes. In a liquid crystal display device including a substrate and a liquid crystal layer sandwiched between both substrates, the light transmittance of the liquid crystal layer located at a position other than the intersection between the first and second transparent electrodes is substantially 0. A liquid crystal display device characterized in that Δnd (where Δn is the birefringence amount of the liquid crystal and d is the thickness of the liquid crystal layer) is set so that 2. The liquid crystal display device according to claim 1, wherein a photosensitive resin layer for setting a desired Δnd is disposed between adjacent transparent electrodes on the same substrate. 3. One substrate having pixel electrodes arranged in a matrix and switching elements connected to the pixel electrodes, and another substrate having a counter electrode and arranged to face the one substrate. In a liquid crystal display device including a liquid crystal layer sandwiched between both substrates, Δnd (where Δn is equal to n is set so that the light transmittance of the liquid crystal layer located in the non-pixel portion between the pixel electrodes is substantially 0). A liquid crystal display device characterized in that a birefringence amount of liquid crystal and d is a thickness of a liquid crystal layer are set. 4. A step of applying a photosensitive resin from a positive resist film left after patterning a transparent electrode on the transparent substrate, and exposing and developing the photosensitive resin from the rear surface of the transparent substrate. And a step of forming a photosensitive resin layer between the transparent electrodes by the method of manufacturing a liquid crystal display device.