JP3052353B2 - Electro-optical device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electro-optical device. Specifically, the present invention relates to an electro-optical device having a color filter layer.

[Prior Art] Conventionally, as a method of forming a transparent electrode on a color filter, JP-A-61-233720, JP-A-61-260224, JP-A-61-198131, or JP-A-61-198131. As disclosed in JP-A-153826, the shape and material of a color filter and a protective layer are proposed. Further, a method of forming a cell by combining an electro-optical device (hereinafter referred to as NTN) capable of supporting high-capacity display proposed in JP-A-64-519 and the above-described color filter forming method has been proposed. .

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, the method of forming a transparent electrode on a color filter involves flattening,
It has been studied from the viewpoint of heat resistance and the like, and if this method is applied to NTN, there is a possibility that a high-quality electro-optical device can be provided,
At this time, the spectral transmittance of the color filter and the refractive index difference of a dimming liquid crystal cell (hereinafter, referred to as B cell) and an optically anisotropic substance (hereinafter, referred to as A cell) having a transparent electrode formed on the color filter. The transmittance characteristic at each wavelength is represented by the product of the birefringence index (Δn × d) represented by the product of the anisotropy (Δn) and the cell thickness (d). The display quality such as reproducibility is determined. At this time, the display quality of the B cell and the A cell is determined by adjusting the birefringence (Δn × d), and when the same liquid crystal material is used (Δn is equal).
Must have the same cell thickness throughout the cell. However, the liquid crystal material of the B cell has a problem that an expensive additive is required to improve the response speed and the optical steepness, resulting in an increase in cost. Therefore,
It is conceivable to form the A cell with an inexpensive liquid crystal material so that the product of Δn × d becomes equal, but strictly speaking, complete white and black are not obtained in the visible light region because the refractive index dispersion is not considered. In the display quality. On the other hand, on the color filter side, a black mask (hereinafter, referred to as B / M) is formed between each color filter to reduce the amount of transmission in the negative mode and improve the black level. There is a problem that the cost is increased due to the formation of the / M, a defect occurs at the time of the formation of the B / M, the yield decreases, and strictly, the white and black levels of the pixel portion are not improved.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an electro-optical device capable of displaying a high-quality color with good reproducibility of white and black levels easily and at low cost. .

[Means for Solving the Problems] The electro-optical device of the present invention includes a pair of opposing substrates.
Liquid crystal having birefringence and refractive index dispersion is sandwiched,
Electro-optics in which a liquid crystal cell in which a color filter is formed on one of the pair of substrates, at least one optically anisotropic body having birefringence and refractive index dispersion, and a polarizer are laminated. In the device, the relationship between the birefringence and the refractive index dispersion of the liquid crystal cell and the optically anisotropic body to the luminous transmittance, the birefringence and the refractive index such that the luminous transmittance is minimized. Dispersion is set, and the ratio of the maximum value of the transmittance of each of the blue, green, and red color components of the color filter is set to 1.8 or less, and the maximum value of the transmittance of each of the color components is set to blue, green, and red. It is characterized in that they are sequentially increased.

EXAMPLES Hereinafter, the present invention will be described in more detail based on one example. The electro-optical device according to the present invention can be applied not only to a device that is conventionally twisted by a known orientation process but also to a device that is oriented (not twisted) in parallel with a substrate. It is not limited to. Further, in the case of twist orientation, the twist angle is not limited, but is preferably 90 ° to 360 ° in view of contrast, display characteristics and manufacturing stability. However, there is no limit on the twist angle, so 90
It can be applied to less than 360mm or more than 360mm. Also, in FIG. 1, the A cell is arranged above the B cell, but may be arranged below, or may be arranged above and below. can get. FIG. 1 shows a transmissive electro-optical device, but a well-known reflector may be provided below the lower polarizer 1 to form a reflective electro-optical device.

The structure of the electro-optical device used in various studies of the present invention will be described with reference to FIG. It is to be noted that the effect of the present invention is not limited to only the structure shown here, as described above. As shown in FIG. 1, a color filter is provided inside, a cell thickness is 7 μm, and the left twist is set to 230 ° to form a B cell, and the same birefringence as the B cell (cell gap: d
And liquid crystal or optically anisotropic refractive index anisotropy: Δn
A cell was placed between the polarizers 1 and 2 so as to have the same birefringence as Δn × d = 0.9 and Δn = 0.129) and to optically compensate the B cell. In this embodiment, the A cell is Δn ×
Assuming d = 0.9, d = 8 μm and Δn = 0.113. here,
The B cell, the A cell, and the refractive index dispersion (α) are defined by the following equation. (In general, a liquid crystal material has a refractive index anisotropy Δn having a wavelength λ.
(Use the ratio of refractive index anisotropy at wavelengths λ = 450 nm and λ = 600 nm to show negative dependence on (nm).) Α is the same for the same liquid crystal material, but becomes the same depending on the setting of different liquid crystal materials. It is known that the relationship between α and the birefringence (Δn × d) with respect to the luminous transmittance (% T) is as shown in FIG. 2, and in this embodiment, the condition under which the luminous transmittance is minimized And Under these conditions, a good black state is obtained. The luminous transmittance is obtained by measuring the transmittance at the time of transmission through the B cell and the A cell, and correcting the luminosity to the transmittance at each wavelength. This relationship is such that if the B cell and the A cell have the same birefringence, the refractive index dispersion (α) has the same value. Under the conditions of the present embodiment, α = 1.08. Note that this relationship has an optimum value depending on the values of the birefringence and the refractive index dispersion, and is not limited to the value of the present embodiment. The relationship may be set so that the luminous transmittance becomes smallest depending on the cell condition.

The angle between the orientation directions of the contact surfaces of the B cell and the A cell is preferably in the range of 70 ° to 110 °, more preferably 90 °.
゜. In this embodiment, the angle is 90 °. Further, the angle between the polarization axis of each polarizer and the alignment direction of the contact surface side of each of the B cell and the A cell is set at 20 to 50 °, and the values of the birefringence and the refractive index dispersion used in this embodiment are changed. The condition for black when not lit and white when fully lit is 45 °. However, whether the axis of change with respect to the alignment direction is right or left when viewed from above the electro-optical device is a difference between positive and negative. In this embodiment, the change is made negative.

Also, it goes without saying that the color coordinates of each of blue, green, and red are good for color reproducibility to be wide, but the ratio of each transmittance maximum value is 1.8 or less, and preferably 1.4 or less. Good reproducibility. In this embodiment, it is set within 1.4. This means that, for example, when the color filter is in a stripe shape of 100 to 200 μm, when the color coordinates are measured at a spot diameter of 20 mmφ with BM-7 manufactured by Topcon Corporation, the coordinates of x, y are (x, y).
= (0.29-0.32, 0.31-0.33), it is known that a good white color is obtained, which is consistent with the result. If the ratio of the transmittance maximum value is deviated, the color balance is lost, and the entire white color is shifted to the color side having the higher transmittance.

Example 1 This will be described with reference to FIG. Red, green,
The ink in which each of the blue pigments was dispersed was printed in a stripe pattern with a width of 110 μm by an offset method to form a color filter 4 with a thickness of 1.5 μm. At this time, the color filters were printed so that the overlap between adjacent stripes was 0 to 10 μm, and the color filters were replaced with B / M to prevent light leakage at the adjacent portions of the color filters. After that, an acrylate resin is applied on the color filter by screen printing.
The protective layer 5 was formed with a thickness of μm. A transparent conductive film made of indium oxide-tin oxide (hereinafter referred to as ITO) was formed on the protective layer 5 at a film forming temperature of 180 ° C. by low-temperature magnetron sputtering at 2000 ° C., and a transparent electrode 6 was formed by a photolithographic method. 4 was formed so as to be orthogonal.
Next, the structure of the electro-optical device of the present invention will be described with reference to FIG. Similarly to the glass substrate 3 shown in FIG. 3, a counter electrode 9 is formed on the glass substrate 8 by ITO so as to form a matrix.
To form After that, the alignment films 7, 10 are
Each was formed at 0 to 400 °. At this time, the alignment agent of the glass substrate 3 having the color filter was formed to be 0.8 mm outside from under the seal 11, and then the liquid crystal 13 was sealed through the gap material 12. The optical characteristics of the electro-optical device formed in this manner are reduced by 1 /
When a rectangular wave equivalent to 400 duty was applied and the spectral transmittance at that time was examined, as shown in Fig. 5, the dispersion transmittance of each of the B cell and A cell coincided with OFF as shown in FIG. It can be seen that the target was compensated, the shutter performance was good, and the color became black. In addition, when ON, a color filter of blue (spectral transmittance of 45% at 460 nm), green (spectral transmittance of 50% at 540 nm), and red (spectral transmittance of 60% at 620 nm) with a protective layer and a transparent electrode respectively, At this time, the ratio of the maximum value of each of the spectral transmittances of blue, green, and red was set to within 1.4, and the white state was good to be averaged, so that a high-quality electro-optical device could be formed. In FIG. 5, the transmittance of the color filter is set so that the maximum value of the blue transmittance, the maximum value of the green transmittance, and the maximum value of the red transmittance increase in order. The transmittance at the time of ON is as shown in the figure.

Embodiment 2 This will be described with reference to FIGS. 6 and 7. FIG. 6 shows a cross-sectional view of the substrate with a color filter of the present invention. A color filter was printed in a stripe pattern on a glass substrate 3 by offset printing in the same manner as in Example 1, and then press-pressed to form a flat color filter 14. At this time, the color filter was set to have a width of 100 μm, and the overlap was set to be 10 μm after pressing. Next, ultraviolet sensitization was given to the epoxy acrylate resin, and 1.2
After coating with a thickness of μm, the protective layer 15 was selectively formed by irradiating ultraviolet rays. Thereafter, as shown in FIG. 7, when the electro-optical device was formed in the same manner as in Example 1, similar good results could be obtained. In this embodiment, the protective layer 15 is formed under the seal 11 so that the cell thickness can be easily controlled.
It goes without saying that similar results can be obtained both inside and outside.

Although described through Examples 1 and 2, the structure of the present invention can be applied to other color filter forming methods (for example, an electrodeposition method, a method of dispersing a pigment in a polyimide substrate or the like, Dispersion and patterning by a photo method, etc.) and other materials (for example, thermosetting melamine resin, epoxy resin, silicone resin) as a protective layer are not restricted.

[Effects of the Invention] As described above, according to the present invention, the luminous transmittance is minimized in relation to the luminous transmittance of the birefringence and the refractive index dispersion of the liquid crystal cell and the optically anisotropic material. Set the birefringence and the refractive index dispersion as described above, and the ratio of the maximum value of the transmittance of each color element of the color filter to 1.8 or less,
By increasing the maximum value of the transmittance of each color element in the order of blue, green, and red, black can be displayed more black, white can be displayed as a well-balanced white display, and the transmittance of the color filter By increasing the maximum value in the order of blue, green, and red, the unbalance of the wavelength transmittance characteristics of the electro-optical device can be compensated, so that the color reproducibility and the contrast can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of an electro-optical device shown in one embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the refractive index dispersion and the birefringence (△ nxd) with respect to the luminous transmittance (% T) shown in one embodiment of the present invention. FIG. 3 is a sectional view of a substrate with a color filter shown in Embodiment 1 of the present invention. FIG. 4 is a diagram showing the structure of the electro-optical device shown in Embodiment 1 of the present invention. FIG. 5 is a diagram showing the spectral characteristics of the electro-optical devices shown in Examples 1 and 2 of the present invention. FIG. 6 is a sectional view of a substrate with a color filter according to a second embodiment of the present invention. FIG. 7 is a diagram showing a structure of an electro-optical device according to a second embodiment of the present invention. 1,2 ... Polarizer 3 ... Glass substrate 4 ... Color filter 5 ... Protective layer 6 ... Transparent electrode 7 ... Alignment film 8 ... Glass substrate 9 ... Counter electrode 10 ... Alignment film 11 ... Seal 12 gap material 13 liquid crystal 14 color filter 15 protective layer

Claims (1)

(57) [Claims] 1. A liquid crystal cell comprising a liquid crystal having birefringence and refractive index dispersion interposed between a pair of opposed substrates, and a liquid crystal cell having a color filter formed on one of the pair of substrates. An electro-optical device formed by laminating at least one layer of optically anisotropic substance having refractivity and refractive index dispersion and a polarizer, wherein the liquid crystal cell and the optically anisotropic substance have birefringence and In the relationship between the refractive index dispersion and the luminous transmittance, the birefringence and the refractive index dispersion are set so that the luminous transmittance is minimized, and the transmission of the blue, green, and red color elements of the color filter is performed. An electro-optical device, wherein the ratio of the maximum values of the ratios is within 1.8, and the maximum value of the transmittance of each color element is increased in the order of blue, green, and red.