JPH0646273B2 - Color liquid crystal display element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a color liquid crystal display device in which a liquid crystal driving semiconductor array is integrated on a substrate.

(Prior Art and Problems Thereof) Liquid crystal display devices have features such as low power consumption, flat panel display, and inexpensive manufacturing, and thus are being put to practical use. In recent years, research and development of a television display using a liquid crystal has been particularly active, and a thin film transistor (TFT: TFT:
The method using the Thin Film Transistor) is attracting attention. The method using the TFT is as shown in FIGS.
The driving TFTs are arranged in a matrix on a substrate (glass or the like) that constitutes a display panel. FIG. 6 (a) is a plan view of a liquid crystal display element provided with a driving TFT, and FIG. 6 (b) is a sectional view taken along the line segment AA 'in FIG. 6 (a).
In FIGS. 6 (a) and 6 (b), a gate electrode 4 is provided on a substrate 1 made of glass or the like in the transistor portion, and an insulating layer 7 is formed thereon.
To form the semiconductor 5, the drain electrode 3, and the source electrode 2. In the display portion, an insulating layer 7F is formed by connecting the transparent electrode 6 to the drain electrode 3. The counter electrode 11 and the insulating film 9 are provided in this order on the counter substrate 11, and the liquid crystal 8 is sealed between the counter substrate 11 and the TFT substrate 1 through the spacer 13. The drain electrode 3 and the counter electrode 10 have In ₂ O ₃ and SnO, respectively.
A transparent conductive film such as ₂ or a metal thin film such as Au or Al is used. Source electrode 2 and gate electrode 4 are Au, Al, Ag, Pt, M
A metal thin film such as o or Cu and a semiconductor thin film such as CdS, CdSe or amorphous silicon is used as the semiconductor 5. A nematic liquid crystal is used as the liquid crystal 8, and the alignment treatment applied to the insulating films 7 and 9 maintains the alignment of the liquid crystal in a specific direction. Display of a liquid crystal display element using this TFT is performed as follows. That is, an image signal is applied to the gate electrode 4,
When a driving voltage is applied to the source electrode 2, the source electrode 2 to which the voltage is applied is electrically connected to the drain electrode 4 intersecting with the transparent electrode 6 connected to the drain electrode 4 and the counter electrode 8. An electric field is generated between them and the alignment state of the liquid crystal 8 changes. It is possible to access each display segment in a two-dimensional matrix by selecting the source electrode 2 and applying a voltage in a scanning manner. When a nematic liquid crystal is used as the liquid crystal 8, a dynamic scattering mode (DSM), It can be displayed in the operation mode of twisted nematic display (TN).

In order to color the liquid crystal display element driven by TFT as described above, it is sufficient to form an inorganic or organic color filter on the counter electrode side corresponding to each display segment. The display element based on such a principle Is proposed. The color filter made of an inorganic material is one in which a low-refractive index thin film and a high-refractive index thin film, for example, an interference filter in which a MgF ₂ thin film and a TiO ₂ thin film are alternately stacked are provided on the substrate 1 or 11.
It is technically difficult to form interference filters of different colors in a minute area of each display segment, and many steps are required, which is not practical. The organic material color filter is a dye filter, which can be formed by permeating a dye into a gelatin film or by directly depositing a dye, and can be manufactured more easily than the above interference filter. However, organic material color filters are
The heat resistance was not sufficient, and the size of the display segment was limited to this extent because the fine pattern had a limit of about 100 μm.

(Object of the Invention) The present invention eliminates such conventional drawbacks and is excellent in light resistance, heat resistance, and pixel density suitable for a liquid crystal display device in which a semiconductor driving circuit is integrally provided on a substrate. Another object is to provide a color liquid crystal display device.

(Structure of the Invention) The present invention relates to a liquid crystal display element in which a liquid crystal material is sandwiched between opposed substrates, and a semiconductor drive circuit is provided on at least one of the substrates, and the semiconductor drive circuit is provided on the inner wall side of at least one of the substrates. The feature is that a diffraction grating is provided.

(Operation / Principle of the Invention) The present invention has solved the problems of the prior art by adopting the above-mentioned configuration. The diffraction grating diffracts the projection light, and by controlling the pitch and phase of the diffraction grating, the wavelength region of specific light can be diffracted in an arbitrary direction. If this diffraction grating is configured inside the liquid crystal display element, the diffraction grating does not absorb light, there is no problem in light resistance and heat resistance, and coloring similar to conventional color filters is possible.
High-precision color display is possible.

FIG. 4 is a diagram showing the principle of wavelength selection by the diffraction grating used in the present invention. In FIG. 4, there is a reflection type diffraction grating in which a reflection film 23 is coated on the surface of a substrate 22 having a rectangular dimple with a depth of d. , + 1st order diffracted light 27 and −1st order diffracted light 28 are diffracted. The + 1st-order diffracted light 27 and the -1st-order diffracted light 28 are diffracted in different directions depending on the wavelength, and the diffraction direction depends on the pitch of the diffraction grating. The wavelength distribution of the 0th-order diffracted light 26 returning to the regular reflection direction depends on the depth d. The 0th-order diffracted light intensity η of an arbitrary wavelength λ is obtained by the following equation, where n is the diffraction index of the medium in which the light travels.

η = cos ₂ (2πnd / λ) (1) Equation (1) has a maximum value of 1 when the depth d of the lattice satisfies the following equation.

d = mλ / 2n (m is an integer) (2) Further, the minimum value is 0 when the depth d of the lattice satisfies the following equation.

d = (2m + 1) λ / 4n (m is an integer) (3) FIG. 5 shows that the refractive index is 1.5, the refractive index of the liquid crystal is 1.5, and the depth d of the diffraction grating is (a) 310 nm, (b). 0 at 260nm, (c) 210nm
The wavelength distribution of the next-order diffracted light is shown. The color for each case is (a)
Cyan, (b) magenta, and (c) yellow are obtained.

Further, a transmissive diffraction grating can be used for the transmissive display cell, and the transmissive diffraction grating can be obtained by periodically arranging various dielectric films having different refractive indexes in a plane. At this time, if the refractive index of the diffraction grating constituent film is n, n ₀ , (1)
The 0th-order diffraction intensity η corresponding to the equation is given by the following equation.

η = cos ² [π (nn ₀ ) d / λ] (4) where d is the thickness of the grating and λ is the wavelength.

When n = 2.8 and n ₀ = 1.5, in order to obtain the 0th order light of cyan, magenta and yellow, the value of d is 720nm, 600nm, 47
Set it to 0 nm.

Since the diffraction grating changes the phase of the projected light,
It does not deteriorate by absorbing projected light, or does not fade due to high temperature. Further, by using the fine processing technology of LSI manufacturing, a grid with a pitch of 1 μm or less is possible, and a high-density color stripe can be formed.

(Embodiment) FIG. 1 is a diagram showing a first embodiment of the present invention. Compared with the conventional display element shown in FIG. 6, the diffraction grating 12 has a glass substrate.
It is different in that it is formed in 11. The pitch of the diffraction grating 12 is the same in the display element, but the depth is periodically different for each display segment. For example, a 2 μm pitte grating is used for each display segment, where a is 377 nm and b is 4
Assuming that the depth of 55nm and c section is 522nm,
As shown in Fig. 3, the 0th order of the reflected light from those parts is red (R), blue (B), and green (G), and the display segments of a, b, and c are red and blue. , Becomes a segment that displays green pixels. The diffraction grating 12 is formed by a photolithography technique by applying photopolymer, photoresist, polyimide or the like, or by sputtering a dielectric material such as SiO ₂ . Next, a reflection type diffraction grating can be manufactured by vapor-depositing a metal reflection film of Al, Au or the like as the counter electrode 10 thereon. On the counter electrode 10, SiO ₂ and SiO are sputtered and vapor deposited as the insulating film 9 and the surface thereof is rubbed, and oblique SiO vapor deposition is applied to form a liquid crystal alignment film. In addition, the pitch of the diffraction grating 12 is set to 1
When the thickness is less than or equal to μm, the periodic structure of the diffraction grating 12 gives an alignment effect to the liquid crystal, so that a configuration without a liquid crystal alignment film is also possible. Further, the diffraction grating 12 is formed by engraving the glass substrate 11 by ion etching, and the counter electrode 1
0, the insulating film 9 may be formed thereon. The glass substrate 11 thus manufactured and the substrate 1 on which the TFT is formed are bonded together with a sealant via a spacer 12,
A display element can be manufactured by injecting liquid crystal.

FIG. 2 is a diagram showing a second embodiment of the electrode. Compared to FIG. 1, the diffraction grating 14 is arranged on the substrate 1 side.
Since the diffraction grating film is a transmissive type, if n is the refractive index, zircon oxide (n = 2.8) and magnesium oxide (n = 1.7).
4), silicon oxide (n = 1.5), magnesium fluoride (n
= 1.38) and other materials having different refractive indexes are alternately arranged. The operation of the display element is the first
It is similar to the embodiment of.

(Effect of the Invention) FIG. 7 shows the results of examining the light resistance against the brightness of the projected light using the electrodes (shown in FIGS. 1 and 2) and the conventional liquid crystal display element. It shows the decrease in saturation when the liquid crystal display element is irradiated with light of 10 ⁶ lux, whereas the color filter (mouth) of the conventional liquid crystal display element fades within 10 minutes. The liquid crystal display device according to the invention does not change even after 10 hours as shown in the curve (a) of FIG.
It showed high light resistance. Further, the size of the display pixel does not depend on the accuracy of the color filter, and it becomes possible to manufacture a high-definition image display device.

As described in detail above, according to the present invention, a color liquid crystal display device having high light resistance, high heat resistance and high density can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of a liquid crystal display device according to the present invention, FIG. 2 is a diagram showing a second embodiment of the liquid crystal display device according to the present invention, and FIG. 3 is a liquid crystal display device according to the present invention. FIGS. 4 and 5 are views for explaining a diffraction grating used in the present invention, FIG. 6 is a view for explaining a conventional liquid crystal display element, and FIG. 7 is a view for showing the effect of the present invention. is there. In the figure, 1 and 11 are glass substrates, 2 are source electrodes, 3 are drain electrodes, 4 are gate electrodes, 5 is a semiconductor, 6 is a transparent electrode, 7 and 9 are insulating films, 8 is a liquid crystal, 10 is a counter electrode, 12, 14
Is a diffraction grating and 13 is a spacer, respectively.

Claims (1)

[Claims] 1. In a liquid crystal display element in which a liquid crystal material is sandwiched between opposed substrates and a semiconductor drive circuit is provided on at least one of the substrates, a diffraction grating is provided on the inner wall side of at least one of the substrates. A color liquid crystal display device characterized by being provided.