How Car Windows Use Special Coatings to Balance Privacy and Visibility
A patent for automotive glass that uses a specific combination of tinted glass and multi-layered coatings to keep the inside private while ensuring the driver can see out clearly.
Original patent title: “Vehicular colored glass pane with light transmittance and reflectance adjustment”
A patent for automotive glass that uses a specific combination of tinted glass and multi-layered coatings to keep the inside private while ensuring the driver can see out clearly. Granted to Central Glass Co Ltd in 2000 with 15 claims and 7 forward citations, and it is now in the public domain.
Coverage
What does this patent actually cover?
The invention describes a vehicle window that combines a tinted glass plate with a specific multi-layered film coating. The film consists of at least one light-absorbent layer and one non-light-absorbent layer. By carefully controlling the light transmittance (how much light gets through) and the reflectance (how much light bounces off) of both the inner and outer surfaces, the glass ensures that passengers inside have privacy while maintaining clear outward visibility. For example, by keeping the inner surface reflectance low (up to 15%), the glass prevents distracting reflections of the vehicle's interior from appearing on the window at night.
The gap
What does this patent NOT cover?
- Does not cover glass panes that do not incorporate a multi-layered film with both light-absorbent and non-light-absorbent layers.
- Does not cover glass configurations where the visible light transmittance falls outside the specific 25% to 55% range.
- Does not cover smart glass technologies that use electrical currents to change opacity (electrochromic glass).
- Does not cover simple tinted glass that lacks the specified multi-layered film structure.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The invention focuses on the specific mathematical difference between light transmittance and surface reflectance. By ensuring the difference between transmittance and inner reflectance is at least 15%, it guarantees that the view from inside remains clear even when the glass is dark enough to offer privacy from the outside.
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Automotive privacy glass
Rear passenger windows in SUVs and minivans
Factory-tinted automotive side windows
Why it matters
The bigger picture
This technology addresses the classic trade-off in automotive design: dark windows provide privacy and sun protection but can be dangerous if they make it hard for the driver to see out at night. By mathematically defining the relationship between transmittance and reflectance, this patent provided a technical roadmap for manufacturers to meet safety regulations while satisfying consumer demand for privacy.
Filed
July 24, 1997
Granted
March 7, 2000
Market context
Who's building on this
Companies in this space
The technology is utilized by major automotive glass manufacturers and suppliers like AGC (formerly Asahi Glass Co., the parent of Central Glass), Saint-Gobain, and NSG Group. These companies continue to refine thin-film deposition techniques to improve thermal insulation and optical clarity in modern vehicles.
Market impact
This patent helped standardize the performance requirements for factory-tinted automotive glass. It enabled manufacturers to produce consistent, high-quality privacy glass that met international safety standards for light transmission, effectively moving the industry away from aftermarket adhesive tint films toward integrated glass solutions.
Claim 1 — Plain English
What this patent covers
The invention describes a vehicle window that combines a tinted glass plate with a specific multi-layered film coating. The film consists of at least one light-absorbent layer and one non-light-absorbent layer. By carefully controlling the light transmittance (how much light gets through) and the reflectance (how much light bounces off) of both the inner and outer surfaces, the glass ensures that passengers inside have privacy while maintaining clear outward visibility. For example, by keeping the inner surface reflectance low (up to 15%), the glass prevents distracting reflections of the vehicle's interior from appearing on the window at night.
The clever bit
The invention focuses on the specific mathematical difference between light transmittance and surface reflectance. By ensuring the difference between transmittance and inner reflectance is at least 15%, it guarantees that the view from inside remains clear even when the glass is dark enough to offer privacy from the outside.
What it does not cover
- Does not cover glass panes that do not incorporate a multi-layered film with both light-absorbent and non-light-absorbent layers.
- Does not cover glass configurations where the visible light transmittance falls outside the specific 25% to 55% range.
- Does not cover smart glass technologies that use electrical currents to change opacity (electrochromic glass).
- Does not cover simple tinted glass that lacks the specified multi-layered film structure.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
This patent is in the public domain
See the Freedom to Build guide — what is free to use, what is not, and how to cite this patent.
PatentBrief Score
Impact Score
Early stage
Citation count
18/40
Early citations
Claim breadth
10/20
Broad claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$5K – $17K
Midpoint $11K · expired or expiring · industry ×0.9
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Claim text not yet imported for this patent
The original legal language
Original claims
15 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Miyazaki, O., Tanaka, K., & Inoue, M. (2000). How Car Windows Use Special Coatings to Balance Privacy and Visibility (U.S. Patent No. 6,033,785). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/6033785/vehicular-colored-glass-pane-with-light-transmittance-and-reflectance-adjustment
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How Car Windows Use Special Coatings to Balance Privacy and Visibility cover?
A patent for automotive glass that uses a specific combination of tinted glass and multi-layered coatings to keep the inside private while ensuring the driver can see out clearly.
Who owns patent US 6033785?
Central Glass Co Ltd owns this patent, granted in 2000.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 6033785 cited by?
This patent has been cited by 7 later patents that build on its ideas.
What problem does this patent solve?
This technology addresses the classic trade-off in automotive design: dark windows provide privacy and sun protection but can be dangerous if they make it hard for the driver to see out at night. By mathematically defining the relationship between transmittance and reflectance, this patent provided a technical roadmap for manufacturers to meet safety regulations while satisfying consumer demand for privacy.
What does this patent NOT cover?
Does not cover glass panes that do not incorporate a multi-layered film with both light-absorbent and non-light-absorbent layers.
Patent monitoring