JPH1184430A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure which protects a polarizing layer built in a reflection type display device against deterioration. SOLUTION: The reflection type display device is assembled by using a pair of substrates 1, 2. The first substrate 1 exists on an incident side and is formed with transparent electrodes 6. The second substrate 2 exists on a reflection side and is formed with transparent electrodes 11 and is joined to the first substrate 1 via a prescribed spacing. Liquid crystals 3 are held as an electro-optic material in the spacing between both substrates 1 and 2. The polarizing layer 9 is interposed between the second substrate 2 and liquid crystal 3. The polarizing layer 9 is formed by uniaxially orienting the high-polymer liquid crystals in the state of dispersing a dichroic dyestuff into the liquid crystals. A transparent protective layer 30 is disposed between the polarizing layer 9 and the liquid crystal 3 in order to protect the polarizing layer against the liquid crystal 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a display device.
More specifically, the present invention relates to a reflective display device having a polarizing element built-in.

[0002]

2. Description of the Related Art Many polarizing elements used in a display device using an electro-optical material such as liquid crystal have a structure as shown in FIG. A polarizing element is produced by adsorbing and dispersing polarizing particles on a polarizing substrate 101, sandwiched between supports 102 and fixed with an adhesive layer 103 in order to maintain the durability and mechanical strength. As a basic function, it is important that a polarizing element exhibits a high polarizing function and also has excellent appearance characteristics and durability, and is easy to process as a component and easy to use. In order to satisfy these functions, polarizers for display devices currently supplied on the market mainly use a halogen substance such as iodine or a dye as polarizing particles. As the polarizing substrate 101, a polyvinyl alcohol film is often used. A film of polyvinyl alcohol is stretched about 3 to 5 times in a certain direction between rollers rotating at different speeds. The stretched micelles of polyvinyl alcohol are arranged in the stretching direction, and the arranged film generates strong birefringence.

The above-mentioned polarizing element is generally supplied on the market as a polarizing plate. An adhesive is applied to one surface of the polarizing plate in advance. When incorporated in a display device, a polarizing plate is attached to the outer surface of a liquid crystal panel, which is a main component thereof, via an adhesive. It is necessary to perform this sticking work so that air bubbles and foreign matter are not caught between the panel and the polarizing plate.
This is a burden on the manufacturing process. Further, it is difficult to insert a conventional polarizing element into a liquid crystal panel. In the case of a reflection-type display device, it is not possible to realize this with a conventional polarizing plate, though it is preferable to incorporate a polarizing element inside from the viewpoints of efficiency of use of incident light and image quality.

Japanese Patent Application Laid-Open No. 2-101431 discloses a display device having a built-in polarizing element, which is shown in FIG. In the figure, 1 and 2 are substrates, 6 and 11 are electrodes, 4 and 9 are polarizing layers also serving as alignment layers, 3 is a liquid crystal layer, and 50 is a spacer. The electrode 6 formed on the upper substrate 1 is made of a transparent conductive material such as ITO or SnO _2, and the electrode 11 formed on the lower substrate 2 is made of a reflective metal, for example. The upper and lower polarizing layers 4 and 9 are made of a polymer liquid crystal mixed with a dichroic dye and have uniaxial anisotropy. As dichroic dyes, merocyanine dyes, styryl dyes, azomethine dyes, azo dyes and anthraquinone dyes are used. As the polymer liquid crystal, it is desirable to use a thermotropic system in view of the fact that uniaxial orientation can be easily and satisfactorily imparted by a thermal process.
In order to maintain the developed uniaxial anisotropy for a long time, a thermotropic polymer liquid crystal having a glass transition temperature higher than the operating temperature of the display device is used. In order to form the polarizing layers 4 and 9, the polymer liquid crystal is dissolved in an appropriate solvent such as toluene or tetrahydrofuran, mixed with a dichroic dye, and then applied by a method such as vapor deposition, spin coating, roller coating, or dipping. Then, heat treatment and drying may be performed. The thickness is 0.05 to 0.5 μm. In order to impart uniaxial anisotropy to the polarizing layers 4 and 9, it is indirectly performed through an electrode surface or a substrate surface which has been subjected to an alignment treatment in advance by a rubbing treatment, a plasma treatment, an etching treatment, or the like.

FIG. 10 is a schematic view showing the structure of a polarizing layer. The polarizing layer 9 is formed directly on the substrate 2. Polarizing layer 9
Consists essentially of a deposited polymer liquid crystal 9a and a dichroic dye 9b incorporated therein. The polymer liquid crystal 9a includes liquid crystal molecules uniaxially aligned in a predetermined direction in a side chain.
In the figure, a polymer liquid crystal 9 uniaxially oriented in a direction parallel to the paper surface is shown.
a is schematically represented by an ellipsoid. On the other hand, the dichroic dye 9b exhibits different absorbances for the incident light in the major axis and the minor axis of the molecule. In the dichroic dye 9b, the major axis of the molecule is aligned in a direction parallel to the paper surface according to the uniaxial orientation of the polymer liquid crystal 9a. With such a configuration, the polarizing layer 9 can selectively absorb and transmit the vibration component included in the incident light and convert it into substantially linearly polarized light. Note that a base alignment layer 22 for uniaxially aligning the polymer liquid crystal 9 a is provided between the substrate 2 and the polarizing layer 9.

[0006]

In the conventional structure shown in FIGS. 9 and 10, there is a problem that the dichroic dye 9b contained near the surface of the polarizing layer 9 dissolves into the liquid crystal layer 3.
As a result, the reliability is lowered, and there is a fear that the contrast is deteriorated. In the conventional example shown in FIG.
Reference numeral 4 also serves as an alignment layer, and the liquid crystal layer 3 is twist-aligned, for example. In some cases, an alignment layer for the liquid crystal layer 3 may be separately formed on the surfaces of the polarizing layers 4 and 9. The alignment layer is made of, for example, polyimide. Polyimide is dissolved in an appropriate solvent and applied to the surfaces of the polarizing layers 4 and 9 to form an alignment layer. As a solvent, NMP (n-methyl-2-pyrrolidone), γ-butyrolactone, or the like is used. However, the polymer liquid crystal 9a constituting the polarizing layers 4 and 9 may be dissolved by these solvents, and sufficient polarizing performance may not be obtained. When these solvents are used, when the substrate temperature exceeds 40 ° C., the polymer liquid crystal constituting the polarizing layer is rapidly dissolved.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems of the prior art, the following measures have been taken. The display device according to the present invention is of a reflection type and is basically assembled using a pair of substrates. The first substrate is located on the incident side and has an electrode formed thereon. The second substrate is located on the reflection side, has electrodes formed thereon, and is joined to the first substrate via a predetermined gap. An electro-optical material such as a liquid crystal is held in a gap between the two substrates. Further, a polarizing layer is interposed between the second substrate and the liquid crystal. This polarizing layer is uniaxially oriented in a state where a dichroic dye is dispersed in a polymer liquid crystal, and is incorporated in a liquid crystal panel. As a characteristic feature, a transparent protective layer is provided between the polarizing layer and the liquid crystal in order to protect the polarizing layer from the liquid crystal. Preferably, the protective layer is an acrylic resin coating. Preferably, a counter electrode is formed on the first substrate side. On the other hand, on the side of the second substrate, a pixel electrode and a switching element for driving the pixel electrode are vertically integrated and formed separately with the polarizing layer and the protective layer interposed therebetween, thus forming a so-called active matrix structure. . The switching element including the pixel electrode and the thin film transistor is electrically connected to each other via a contact hole opened in the polarizing layer and the protective layer. The contact hole can be easily formed by selectively etching the polarizing layer and the protective layer. Preferably, the first substrate is provided with a polarizing plate whose absorption axis is orthogonal or parallel to the polarizing layer on the second substrate side, and the electro-optical material is made of twisted nematic liquid crystal.

In the present invention, a polarizing layer is formed inside a panel using a mixture of a polymer liquid crystal and a dichroic dye. By forming a transparent protective layer made of acrylic resin or the like on the polarizing layer, it is possible to prevent dissolution of the dichroic dye in the liquid crystal and to prevent damage when forming the alignment layer on the polarizing layer. ing.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic partial sectional view showing a display device according to the present invention. This display device is assembled using a pair of substrates 1 and 2. The first substrate 1 is located on the incident side and has a transparent electrode 6 formed thereon.
The second substrate 2 is located on the reflection side, on which the transparent electrode 11 is formed, and the first substrate 1
Is joined to. A liquid crystal 3 is held in the gap between the substrates 1 and 2 as an electro-optical material. A polarizing layer 9 is interposed between the second substrate 2 and the liquid crystal 3. The polarizing layer 9 is not externally mounted but is built in the liquid crystal panel. This polarizing layer 9
Is a uniaxially oriented state in which a dichroic dye is dispersed in a polymer liquid crystal. As a feature, in order to protect the polarizing layer 9 from the liquid crystal 3, a transparent protective layer 30 is provided between them. The protective layer 30 is made of, for example, an acrylic resin coating and has a thickness of, for example, about 1 μm. Note that a fluorine-based resin can also be used for the protective layer 30. In this case, the thickness of the protective layer 30 is, for example, about 0.3 μm. In some cases, a transparent inorganic material can be used for the protective layer 30 instead of the organic material such as the resin described above. For example, silica-based material mainly the SiO ₂ (SO
G) can be used for the protective layer 30. By providing such a protective layer 30, the dichroic dye contained in the polarizing layer 9 can be prevented from being dissolved in the liquid crystal 3.

The present display device is of a so-called active matrix type, and has a counter electrode 6 formed entirely on the substrate 1 side. On the substrate 2 side, a pixel electrode 11 and a switching element for driving the pixel electrode 11 are vertically integrated with a polarizing layer 9 and a protective layer 30 therebetween. In this example, this switching element is formed by the thin film transistor 13. The pixel electrode 11 and the thin film transistor 13 are electrically connected to each other via a contact hole 23 opened in the polarizing layer 9 and the protective layer 30. This contact hole 23 can be precisely formed by patterning the polarizing layer 9 and the protective layer 30 by photolithography and etching. In this structure, the liquid crystal 3 includes the counter electrode 6 and the pixel electrode 11.
, The signal voltage can be applied efficiently.

A polarizing plate 4 is adhered to the outer surface of the first substrate 1. As the polarizing plate 4, the conventional polarizing plate shown in FIG. 8 is used. Instead, a polarizing layer may be formed on the inner surface of the substrate 1. The polarizing plate 4 on the first substrate 1 side is the second substrate 2
The absorption axis is orthogonal to the polarizing layer 9 on the side, and a so-called crossed Nicols arrangement is provided. Instead, the polarizing plate 4 and the polarizing layer 9 may be arranged so that the absorption axes thereof are parallel to each other. The liquid crystal 3 uses a nematic liquid crystal twist-aligned by the upper and lower alignment layers 7 and 12. That is, the twisted nematic liquid crystal 3 is twisted 90 degrees between the upper and lower substrates 1 and 2 and has a positive dielectric anisotropy. The helical pitch of the twisted nematic liquid crystal 3 is designed to satisfy Morgan's requirements. That is, the helical pitch is set sufficiently long with respect to the wavelength of the incident light. The alignment of the liquid crystal molecules 3a of the twisted nematic liquid crystal 3 is controlled by the upper alignment layer 7 in a direction perpendicular to the plane of the drawing, and the lower alignment layer 12 is controlled by the lower alignment layer 12 in a direction parallel to the drawing. As a result,
Twisted nematic liquid crystal 3 has 9
The orientation state is twisted by 0 degrees. The transmission axis of the upper polarizing plate 4 is set perpendicular to the paper surface, and the transmission axis of the lower polarizing layer 9 is set parallel to the paper surface. A color filter 5 is formed on the inner surface of the upper substrate 1 so as to correspond to the pixel electrode 11. A flattening film 5a is interposed between the color filter 5 and the counter electrode 6. The color filter 5 may be formed on the lower substrate 2 side instead of the upper substrate 1 side. A light reflecting layer 8 having a diffusivity is formed on the lower substrate 2. Note that the light reflection layer 8 may have a mirror-reflective property. In this case, it is preferable to provide a light diffusion layer on the upper substrate 1.

The reflection type display device according to the present embodiment is of a so-called active matrix type, in which, for example, a thin film transistor 13 is formed on the lower substrate 2 as a switching element for driving each pixel electrode 11. The thin film transistor 13 has a bottom gate structure, and a gate electrode 14, a gate insulating film 15, and a semiconductor thin film 1 in this order from the bottom.
6, the stopper 17 is laminated. An interlayer insulating film 18 is formed so as to cover the thin film transistor 13. On top of this, the source electrode 19 and the drain electrode 2
0 is formed by patterning, and is electrically connected to the thin film transistor 13 through a contact hole opened in the interlayer insulating film 18. The light reflecting layer 8 is formed on the interlayer insulating film 18.
Are formed. The light reflection layer 8 is subdivided for each pixel corresponding to the pixel electrode 11 and has the same potential as the drain electrode 20. The reflective layer 8 has an uneven light scattering surface and realizes a display screen called a so-called white paper. A flattening layer 21 is formed so as to fill the unevenness of the thin film transistor 13 and the light reflection layer 8. A base alignment layer 22 is formed on the flattening layer 21 and is used to uniaxially align a polymer liquid crystal formed thereon. The pixel electrode 11 has a contact hole 2 provided through the protective layer 30, the polarizing layer 9, the base alignment layer 22, and the planarizing layer 21.
3 and is electrically connected to the drain electrode 20 of the corresponding thin film transistor 13.

The operation of the display device will be described with reference to FIGS. FIG. 1 shows a state where no voltage is applied. When external light is incident on the upper substrate 1 in this state, the external light is first converted by the polarizing plate 4 into linearly polarized light having a vibration component perpendicular to the paper surface. However, in the case of the reflection type, a polarizing plate 4 having a low polarization degree may be used intentionally in order to increase the brightness. At this time, the external light is converted into elliptically polarized light instead of linearly polarized light. When the linearly polarized light enters the twisted nematic liquid crystal 3, the linearly polarized light rotates by about 90 degrees due to the optical rotation thereof and advances to the polarizing layer 9 in a state where no voltage is applied. Since the transmission axis of the polarizing layer 9 is set parallel to the paper surface, the linearly polarized light passes through the polarizing layer 9 as it is and reaches the light reflecting layer 8. That is, the present embodiment is a normally white mode, in which most of the incident light is transmitted without applying a voltage. Polarizing layer 9
Is reflected by the light reflection layer 8 and is emitted out of the panel through a path opposite to that at the time of incidence. The polarizing layer 9
When the transmission axis is set to be perpendicular to the plane of the drawing, the linearly polarized light that has passed through the twisted nematic liquid crystal 3 is almost absorbed by the polarizing layer 9, resulting in a so-called normally black mode.

As the applied voltage is increased, the optical rotation of the twisted nematic liquid crystal 3 is gradually lost. As shown in FIG. 2, when a high voltage higher than the threshold is applied, the liquid crystal molecules 3
a shifts to the vertical alignment, and the optical rotation almost disappears. Therefore, the light transmitted through the upper polarizing plate 4 reaches the lower polarizing layer 9 as it is. In the case of the normally white mode, the polarizing plate 4 and the polarizing layer 9 are set in crossed Nicols, so that the linearly polarized light that has passed through the twisted nematic liquid crystal 3 is almost completely absorbed by the polarizing layer 9. In the case of the normally black mode, since the transmission axes of the polarizing plate 4 and the polarizing layer 9 are parallel, most of the incident light is transmitted and reflected by the light reflecting layer 8 as it is.

The method for forming the polarizing layer and the protective layer will be described in detail with reference to FIG. First, the alignment step (A) is performed, and the surface of the insulating substrate 2 such as glass or quartz is aligned along a predetermined alignment direction. For example, after a base alignment layer 22 made of a polyimide film or the like is formed on the surface of the substrate 2, the polyimide film may be rubbed along the alignment direction. In addition, polyamic acid, polyvinyl alcohol, or the like can be used as the base alignment layer 22 instead of polyimide. In some cases, the surface of the substrate 2 may be directly rubbed.

Next, a film forming step (B) is performed. First, a solution in which the polymer liquid crystal 9a and the dichroic dye 9b are dissolved in a solvent is prepared in advance. This solution is subjected to alignment treatment on substrate 2
To form a coating film. The polymer liquid crystal 9a
Has a property of causing a phase transition between a liquid phase on the high temperature side and a liquid crystal phase on the low temperature side at a predetermined dislocation point. The polymer liquid crystal 9a and the dichroic dye 9b are dissolved in an appropriate solvent, and applied to the surface of the substrate 2 that has been subjected to the alignment treatment by spin coating, wire coating, or various printings. As the solvent, for example, a solution in which cyclohexanone and methyl ethyl ketone (MEK) are mixed at a ratio of 8: 2 can be used. After applying the solution, heat and dry at a temperature sufficient to evaporate the solvent.

Subsequently, a temperature processing step (C) is performed, and the substrate 2
Is heated once to the dislocation point or higher, then cooled to room temperature below the dislocation point, and the formed polymer liquid crystal 9a is aligned in the alignment direction to form the polarizing layer 9. In some cases, it is possible to obtain a desired uniaxial orientation by allowing the liquid crystal phase to stand for a certain period of time. As shown, the liquid crystal molecules contained in the polymer liquid crystal are in a random state during the film formation stage,
After the temperature treatment step, the liquid crystal molecules are aligned along the alignment direction, and a desired uniaxial alignment can be obtained. At the same time, the dichroic dye also becomes uniaxially oriented. In the example described above, the polymer liquid crystal already in a polymer state is dissolved in a solvent and applied to the substrate, but a material in a monomer state may be used instead. In this case, a polymer is obtained by uniaxially orienting in a monomer state and then irradiating with ultraviolet rays or the like to polymerize. When the viscosity of the liquid crystal in the monomer state is low, the dichroic dye can be directly dissolved in the liquid crystal without using a solvent, and the solution can be applied onto a substrate.

Finally, a protection step (D) is performed to form a transparent protection layer 30 on the polarizing layer 9. First, the dichroic dye 9
The dichroic dye 9b contained in the vicinity of the surface of the polarizing layer 9 is washed away by using a solvent that dissolves b and does not dissolve the polymer liquid crystal 9a. For example, ethanol can be used as such a solvent. Thereafter, for example, an acrylic resin is applied on the polarizing layer 9 by a method such as spin coating. The coating liquid is obtained by dissolving an acrylic resin in a solvent such as methoxypropyl acetate. Thereafter, a heat treatment is performed to evaporate the solvent contained in the coating film. At this time, it is necessary to perform heat treatment (bake) in a temperature range in which the polarizing layer 9 is not damaged by a solvent such as methoxypropyl acetate. Specifically, it is preferable to perform baking at a temperature of 60 ° C. or less. At this time, evaporation of the solvent becomes more efficient if vacuum baking is performed. When a transparent resin of a type that performs cross-linking polymerization is used as the protective layer 30, the cross-linking polymerization is performed by heating at an appropriate temperature.

FIG. 4 shows specific examples of the polymer liquid crystal 9a, each of which has a side chain type chemical structure. (I)
Indicates a polymer liquid crystal having biphenylbenzoate as a pendant entering a side chain. That is, side chains are bonded to the alkyl main chain at predetermined intervals (only one side chain is shown in the figure). The space length of this side chain is 6 in carbon number, but the present invention is not limited to this. Biphenyl benzoate is attached to the tip of this side chain as a pendant. (II) represents a side chain type polymer liquid crystal having methoxybiphenyl in addition to biphenylbenzoate as a pendant. The space length of the side chain to which methoxybiphenyl is bonded is 2 in carbon number, but the present invention is not limited to this. (III)
Shows a side chain type polymer liquid crystal having methoxyphenyl benzoate as a pendant. The side chain has a space length of 2 or 6 carbon atoms bonded to the main chain.
Types (I) and (II) have better solvent resistance than type (III). Furthermore, the side chain type polymer liquid crystal shown by (IV) also shows good uniaxial orientation.

FIG. 5 shows a specific example of the dichroic dye 9b. In this example, the dyes A to E were mixed to prepare a black dichroic dye. Dye A alone shows blue, Dye B shows yellow alone, Dye C shows red alone, Dye D alone shows blue-violet, and Dye E shows blue alone. These dyes are A: B: C: D: E = 2: 1: 1: 1: 1
To prepare a black dichroic dye.

Finally, with reference to FIGS. 6 and 7, a method of manufacturing the reflective display device shown in FIG. 1 will be described in detail. First, in the step (A) of FIG. 6, a thin film transistor 13 is integratedly formed on an insulating substrate 2 made of glass or quartz. Specifically, after a gate electrode 14 made of a refractory metal film or the like is formed by patterning, a silicon oxide film or a silicon nitride film is deposited by CVD or the like to form a gate insulating film 1.
5 is assumed. A semiconductor thin film 16 made of polycrystalline silicon or the like is formed thereon, and is patterned in an island shape according to the element region of the thin film transistor 13. A stopper 17 is provided thereon so as to match the gate electrode 14. Using the stopper 17 as a mask, an impurity is implanted into the semiconductor thin film 16 by ion doping or ion implantation to form a bottom-gate thin film transistor 13. This thin film transistor 13 is covered with an interlayer insulating film 18 made of PSG or the like.

Proceeding to step (B), after opening a contact hole in the interlayer insulating film 18, the source electrode 19 is formed by sputtering aluminum or the like and patterning it into a predetermined shape.
And a drain electrode 20. At this time, the light reflection layer 8 is formed at the same time. In the region where the light reflecting layer 8 is to be formed, irregularities are formed in advance as a base. As a result, the light reflecting layer 8 has light scattering properties, and a so-called white paper display appearance is obtained. Further, a flattening layer 21 made of an acrylic resin or the like is formed so as to fill the unevenness of the thin film transistor 13 and the light reflection layer 8. A rubbing treatment is applied thereon by applying a polyimide resin, and a base alignment layer 22 is provided. A polarizing layer 9 made of a mixture of a uniaxially oriented polymer liquid crystal and a dichroic dye is formed thereon. Specifically, a solution in which a polymer liquid crystal and a dichroic dye are dissolved is formed on the base alignment layer 22. The polymer liquid crystal is a material capable of phase transition between a high temperature side nematic liquid crystal phase and a low temperature side glass solid phase at a predetermined dislocation point. For example, the polymer liquid crystal is in a glassy state at room temperature, and is preferably a main chain type or a side chain type having a phase transition point at 100 ° C. or higher. After the polymer liquid crystal and the dichroic dye are dissolved in an organic solvent, the solution is applied to the surface of the base alignment layer 22 by spin coating. In addition, you may apply using dipping or screen printing etc. instead of spin coating. Thereafter, the substrate 2 is once heated to a temperature equal to or higher than the dislocation point, then cooled to room temperature equal to or lower than the dislocation point, and the formed polymer liquid crystal is aligned in the alignment direction to form the polarizing layer 9. Subsequently, a protective layer 30 is formed so as to cover the polarizing layer 9. As described above, a coating solution in which an acrylic resin is dissolved in a solvent such as methoxypropyl acetate is applied onto the polarizing layer 9 by a method such as spin coating. And 60 ° C
Vacuum baking is performed at the following temperature to evaporate the solvent, thereby forming a protective layer 30 made of a transparent acrylic resin. The thickness of the protective layer 30 is, for example, about 1 μm, and the thickness of the polarizing layer 9 is, for example, about 0.8 μm.

In step (C), a photoresist 10 is applied so as to cover the entire surface of the protective layer 30. As a coating method, spin coating or screen printing can be used. Proceeding to step (D), the photoresist 10 is exposed and developed to form a window 1
0a is provided.

Proceeding to step (E) in FIG. 7, etching is performed using the patterned photoresist 10 as a mask to form a contact hole 23 penetrating through the protective layer 30, the polarizing layer 9, the base alignment layer 22, and the planarizing layer 21. Open. Here, dry etching in which oxygen plasma or the like is applied is employed. In step (F), after removing the used photoresist 10, a transparent conductive film made of ITO or the like is formed on the protective layer 30, patterned into a predetermined shape, and processed into the pixel electrode 11. The pixel electrode 11 is electrically connected to the drain electrode 20 of the thin film transistor 13 via the contact hole 23. As is clear from the figure, the structure is such that the protective layer 30 is interposed between the polarizing layer 9 and the pixel electrode 11. The protective layer 30 includes the pixel electrode 11 and the polarizing layer 9.
Has a buffer effect of absorbing stress due to the difference in the coefficient of thermal expansion. It is assumed that the pixel electrode 11 is not provided without the protection layer 30 interposed therebetween.
When the polarizing layer 9 and the polarizing layer 9 are in direct contact with each other, damage is caused by a heat treatment applied in a later step, and for example, the surface of the pixel electrode 11 becomes uneven. The heat treatment in the later step includes, for example, baking a resist used when processing the ITO into the pixel electrode 11.

Finally, the process proceeds to the step (G), where the organic alignment layer 12 is formed on the pixel electrode 11 and the protective layer 30. That is,
A horizontal alignment agent is continuously applied on the pixel electrode 11 and on the protective layer 30 exposed between the pixel electrodes 11 and rubbed to form the alignment layer 12. Specifically, polyimide is NM
After applying an aligning agent dissolved in a solvent such as P or γ-butyrolactone, the solvent is evaporated. The thickness of the alignment layer 12 thus obtained is, for example, about 30 nm. In the present invention, since the polarizing layer 9 is covered with the protective layer 30, the solvent contained in the alignment agent does not directly contact the polarizing layer 9. Therefore, there is no possibility that the polymer liquid crystal constituting the polarizing layer 9 is dissolved. Conventionally, when the protective layer 30 is not used, in order to suppress the dissolution of the polymer liquid crystal as much as possible, it is necessary to suppress the processing temperature for evaporating the solvent contained in the alignment agent to 40 ° C. to 50 ° C. or lower. Was. Thereafter, although not shown, the upper substrate on which the counter electrode, the color filter, and the alignment layer have been formed in advance is bonded to the lower substrate 2 via a predetermined gap, and if the nematic liquid crystal is injected into this gap, the reflection will occur. The type display device is completed. When joining the two substrates, a sealing material is used, but heat treatment is required to cure the sealing material. Even if this heat treatment is performed, since the protective layer 30 is interposed between the polarizing layer 9 and the pixel electrode 11, the surface of the pixel electrode 11 does not become uneven due to thermal stress.

[0026]

As described above, according to the present invention,
In a reflection type liquid crystal display device incorporating a light reflection layer and a polarizing layer, a transparent protective layer is provided between the two to protect the polarizing layer from liquid crystal. With such a configuration, the dichroic dye contained in the polarizing layer can be prevented from dissolving into the liquid crystal, which leads to improvement in contrast and reliability. For example, a decrease in the voltage holding ratio of the display device and an increase in the residual DC component can be prevented. Further, when forming an alignment layer for aligning the liquid crystal, dissolution of the polarizing layer by NMP or γ-butyrolactone used as a solvent for the alignment layer can be prevented.
Further, the buffering effect of the protective layer can prevent the pixel electrode from being damaged due to a difference in the coefficient of thermal expansion between the pixel electrode and the polarizing layer.

[Brief description of the drawings]

FIG. 1 is a schematic partial cross-sectional view showing a reflective display device incorporating a polarizing layer and a protective layer according to the present invention.

FIG. 2 is a schematic partial cross-sectional view for explaining the operation of the display device shown in FIG. .

FIG. 3 is a process chart showing a method for producing a polarizing layer and a protective layer.

FIG. 4 is a chemical structure diagram showing a specific example of a polymer liquid crystal used for forming a polarizing layer.

FIG. 5 is a chemical structure diagram showing a specific example of a dichroic dye used for forming a polarizing layer.

FIG. 6 is a process chart showing a method for manufacturing a reflective display device.

FIG. 7 is a process chart showing a method for manufacturing a reflective display device.

FIG. 8 is a schematic view showing the structure of a conventional polarizing plate.

FIG. 9 is a partial cross-sectional view showing a structure of a conventional display device.

FIG. 10 is a schematic diagram showing a structure of a polarizing layer incorporated in the display device shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Substrate, 3 ... Twisted nematic liquid crystal, 4 ... Polarizing plate, 6 ... Counter electrode, 8
..Light reflecting layers, 9 polarizing layers, 11 pixel electrodes,
13 ... thin film transistor, 22 ... underlying alignment layer,
30 ... Protective layer

Claims (4)

[Claims] 1. A first substrate located on an incident side, a second substrate located on a reflecting side and joined to the first substrate via a predetermined gap, and held in a gap between the two substrates. An electro-optical material, a display device comprising a polarizing layer interposed between the second substrate and the electro-optical material, wherein the polarizing layer is a state in which a dichroic dye is dispersed in a polymer liquid crystal. A display device, which is uniaxially oriented, wherein a transparent protective layer is provided between the polarizing layer and the electro-optical material to protect the polarizing layer from the electro-optical material. 2. The display device according to claim 1, wherein the protective layer is an acrylic resin coating film. 3. A counter electrode is formed on the first substrate side, and a pixel electrode and a switching element for driving the pixel electrode are disposed on the second substrate side with the polarizing layer and the protective layer interposed therebetween. 2. The display device according to claim 1, wherein the display device is formed in a vertically integrated manner, and both are electrically connected to each other via a contact hole opened in the polarizing layer and the protective layer. 4. The first substrate is provided with a polarizing plate whose absorption axis is orthogonal or parallel to the polarizing layer on the second substrate side, and the electro-optical material is a twist-aligned nematic liquid crystal. The display device according to claim 1, wherein: